Browse Topic: Heat exchangers

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Aircraft and Aircraft Engine Fuel Pump Low Lubricity Fluid Endurance TestARP1797B (Current)11/26/2025
This procedure is intended to apply to fuel pumps. This procedure will be defined in terms of recommended test fluid, test setup, test conditions, and test method. This procedure may be used for other fuel system components, by testing in conjunction with the pump, which normally supplies the component inlet flow, or a substitute test pump of similar capacity. This procedure may be used, with variations in test conditions and test fluid for performing pump evaluation tests. Tests at progressively increasing pump speeds and pressures will provide design limitation data. Alternate test periods on a test pump and another pump, of a design for which actual service durability is known, will provide useful comparison data.
AE-5B Aircraft and Engine Fuel and Lubricant Sys Components
Laboratory Testing of Vehicle and Industrial Heat Exchangers for Heat Transfer and Pressure Drop PerformanceJ1994_202004 (Current)4/28/2020
This SAE Recommended Practice is applicable to all heat exchangers used in vehicle and industrial cooling systems. This document outlines the tests to determine the heat transfer and pressure drop performance under specified conditions. This document has been reviewed and revised by adding several clarifying statements to Section 4.
Cooling Systems Standards Committee
Enhancement of Heat Exchanger Performance Using Oscillating Flow2020-01-09434/14/2020
In this research work, the heat transfer enhancement by using oscillatory flow of the thermal fluid between cold and hot reservoir has been analyzed both theoretically and using simulation methods. The main objective of this study is to examine the feasibility of a system working under oscillatory flow conditions compared to its steady flow counterpart. The principle of incrementing thermal diffusion over molecular diffusion by establishing oscillatory flow has been utilized in this case. The system has been designed and the effect of the flow condition has been analyzed using ANSYS Fluent k-epsilon model. The effect of change in the magnitude and frequency of oscillation on local Nusselt number has been computed. The observed increment in the Nusselt number by increasing the amplitude and frequency of the fluid has been bolstered by analytical calculation. A comparison in the heat transfer of a system working under oscillating and a steady flow conditions has been generated to establish the need for oscillating flow. The scope of the study has been extended to explore possibility of implementation of this concept in the automotive HVAC system and in the cooling, mechanisms employed in microelectronic components present onboard e-vehicles.
Rajagopalan, Haripriya, Premchandra Tavorath, Adhithiya, Pol, Sakshi, Dhamangaonkar, Pradyumna, Rajagopalan, Haripriya, Premchandra Tavorath, Adhithiya, Pol, Sakshi, Dhamangaonkar, Pradyumna
Transient Simulation of Heat Exchangers with Phase Change Material2020-01-01564/14/2020
Heat exchangers with Phase Change Material (PCM) are finding more energy storage applications for both Internal Combustion Engine Vehicles (ICEVs) and Electric Vehicles (EVs). These applications include cold storage evaporators for stop-start cars, thermal storage system for EV cabin heating and cooling, and other Heating, Ventilation, and Air Conditioning (HVAC) and Power Train Cooling (PTC) peak load shaving applications. The energy stored in a PCM heat exchanger is typically charged/discharged using refrigerant, coolant, or air, depending on the system design of different applications. Due to the low thermal conductivity of state-of-art PCM, the PCM heat exchangers generally rely on aluminum fins to enhance the speed of charging and discharging of the stored energy. Different fin shape, height and density will result in different PCM freezing/melting rate. In this paper, two different fin designs (folded-sine-wave fin and off-set-strip fin) are simulated with Computational Fluid Dynamics (CFD) to compare the melting time of a hot PCM with respect to different operating parameters (coolant temperature, coolant convection heat transfer coefficient, and PCM initial temperature). Next, a 1-Dimensional (1-D) approximation of the 2-Dimensional (2-D) transient heat conduction problem is proposed. The equivalent thermal conductivity of the 1-D approximation is determined using similar CFD approach to match the melting time of the original 2-D problem. The equivalent thermal conductivity of the 1-D approximation can be used as a single metric to evaluate different fin designs. Finally, a Simulink model is developed to simulate the transient performance of a full PCM heat exchanger using the 1-D equivalent thermal conductivity, which can be incorporated into system simulation to optimize heat exchanger design and estimate in-vehicle performance. The model is validated against test data of a heat storage PCM heat exchanger, and its capability of simulating peak load shaving application is demonstrated.
Xia, Yanping, Wolfe, Edward, Craig, Timothy
3-Dimensional Numerical Simulation on CuO Nanofluids as Heat Transfer Medium for Diesel Engine Cooling System2020-01-11094/14/2020
CuO-water nanofluids was utilized as heat transfer medium in the cooling system of the diesel engine. By using CFD-Fluent software, for 0.5%, 1%, 3% and 5% mass concentration of nanofluids, 3-dimensional numerical simulation about flow and heat transfer process in the cooling system of engine was actualized. According to stochastic particle tracking in turbulent flow, for solid-liquid two phase flow discrete phase, the moving track of nanoparticles was traced. By this way, for CuO nanoparticles of different mass concentration nanofliuds in the cooling jacket of diesel engine, the results of the concentration distribution, velocity distribution, internal energy variation, resident time, total heat transfer and variation of total pressure reduction between inlet and outlet were ascertained. It is proved by simulation results that nanofluids as heat transfer medium can evidently enhance diesel engine heat transfer capability, when the concentration of nanoparticles increases, the enhancement of heat transfer capacity increases, power loss of water pump also increases in small scale, the relativity between the average resident time of CuO nanoparticles and CuO nanoparticles concentration is not clear in cooling jacket, the relativity between heat transfer efficiency of CuO nanoparticles and nanofliuds flow velocity is not clear.
Yang, Shuai, Yang, Xiaolin, Liu, Haifeng, Li, Xiuyuan
Accounting Thermal Exchanges in Coanda Effect2020-01-00263/10/2020
An exhaustive model of Coandã effect has not been defined, and fundamental questions are still open. One of them is the influence of convective heat exchange on Coandã adhesion. This paper presents an even preliminary numerical study of this problem. It analyses the behaviour of a fluid stream on a convex surface in the presence of a temperature gradient between the fluid and the convex surface. It approaches the problem by a set of CFD simulations, analyses previous hypotheses, which are based on Prandtl number, and evidences the need for a model that account Reynolds number. The performed simulations are still not sufficient for an exhaustive comprehension of Coandã effect in the presence of heat exchange phenomena. It allows producing some consideration that may help future scientific work in toward a better comprehension of these phenomena. In particular, it verifies the importance of Reynolds number, because it is intrinsic in the adopted model, with good accordance with CFD data. In conclusion, this paper is still far from a complete model of the phenomena that govern the Coandã adhesion in the presence of convective heat exchange. Otherwise, it presents a preliminary starting point toward further and more detailed analyses.
Trancossi, Michele, Pascoa, Jose
EFFECT OF DEAN NUMBER ON HEAT TRANSFER CHARACTERISTICS FOR SQUARE CHANNEL HELICAL COIL SUB-COOLED CONDENSER2019-32-05971/24/2020
Attribute to high heat transfer rate and less complexity, the Helical coil sub-cooled condenser (HCSCC) can provide the most innovative and unique application for the air conditioning system. In the case of automobiles, reduction in air-conditioning load may diminish the vehicular emission, and power consumption as the air-conditioning load is the most power-consuming components after the engine load. Moreover, to solve the problem, we focus on the helical type heat exchanger. It may play a vital role in reducing the weight and increase the performance of the small engine because of the compact structure and lighter weight. The compressor unit is the most vital component of the refrigeration cycle, but the condenser unit is also one of the most critical devices, and the author tried to reduce the power consumption by enhancing the performance of the condenser. The crucial point of this study is to use HCSCC, which exemplify the effect of subsequent flow generation inside the fluid, and it is known as the Dean's effect. This effect leads to the heterogenous temperature distribution along the square cross-sectional channel of the HCSCC. Experimentally, two different square cross-section of HCSCC has been analyzed and then compared with CFD investigation. During the analysis, various Dean numbers were evaluated at different flow rates of refrigerant as well as the varying cross-sectional area of the channel. From the result of the study, it is found that the Dean number plays a significant role in enhancing the heat transfer coefficient.
Singh, Hardeep, Washiashi, Junya, Liu, Jun, Ichiyanagi, Mitsuhisa, Suzuki, Takashi
Mathematical Model of Heat-Controlled Accumulator (HCA) for Microgravity Conditions01-13-01-00011/20/2020
It is reasonable to use a two-phase heat transfer loop (TPL) in a thermal control system (TCS) of spacecraft with large heat dissipation. One of the key elements of TPL is a heat-controlled accumulator (HCA). The HCA represents a volume which is filled with vapor and liquid of a single working fluid without bellows. The pressure in a HCA is controlled by the heater. The heat and mass transfer processes in the HCA can proceed with a significant nonequilibrium. This has implications on the regulation of TPL. This article presents a mathematical model of nonequilibrium heat and mass transfer processes in an HCA for microgravity conditions. The model uses the equations of mass and energy conservation separately for the vapor and liquid phases. Interfacial heat and mass transfer is also taken into account. It proposes to use the convective component k for the level of nonequilibrium evaluation. The experiments were carried out in microgravity conditions for the estimation of the k value. The heating of the HCA was investigated in the flight experiments. The working fluid was ammonia. It was determined that in the mathematical model, the k low margin is k = 15…30 for the microgravity conditions. An analysis of the HCA regulation was performed for two values of the k coefficient. It defined that nonequilibrium has a significant impact on the regulation process. It is shown that to ensure a given mode of TPL operation with the HCA equilibrium process (k > 100), a greater HCA heater power is required than in a nonequilibrium process (k = 30).
Gennadiy Olexandrovich, Gorbenko, Polina Sergeevna, Koval, Konstantin Sergeevich, Yepifanov, Pavlo Grigorovich, Gakal, Rustem Yusufovich, Turna
Q&A: A Shape-Morphing, Self-Healing Soft CompositeTBMG-357881/1/2020
Carmel Majidi, Professor of Mechanical Engineering at Carnegie Mellon University, and his team has developed a material with a unique combination of high electrical and thermal conductivity, with actuation and self-repair capabilities that are unlike any other soft composite.
Reducing winter range loss for electric trucks19TOFHP12_0212/1/2019
Researchers at the Austrian Institute of Technology have developed an air exchange system that's capable of reducing heat load by 37% in real-world tests. Battery-electric vehicle (BEV) range loss from winter use of PTC (positive temperature coefficient) heating has become a source of major concern as the industry works to make EVs a mainstream choice. Addressing this particular problem area with an economically viable solution was deemed a worthwhile effort by the Austrian Institute of Technology (AIT), which is jointly owned by the Austrian government and the Federation of Austrian Industries. A fleet test of electric delivery trucks is underway on European roads. The AIT project, results of which were presented at the recent SAE Thermal Management Systems Symposium (TMSS), began by noting a 20% loss in range at −15°C (+5°F) from the heating system. AIT set a target of recovering 25% of that loss, primarily with the use of a ventilation module. Available reference data (at −10°C/+14°F) showed approximately 75% of the cabin heat losses are from ventilation, AIT said, with the remaining 25% from heated air transmission through the interior.
Weissler, Paul
Transport Method Boosts Capacity of Heat ExchangersTBMG-3572312/1/2019
Turbulent heat exchange is a method of heat transport widely used in heating, ventilation, and air conditioning (HVAC) systems. Adding a readily available organic solvent to common water-based turbulent heat exchange systems can boost their capacity to move heat by 500%. Other methods for increasing heat flux — nanoparticle additives or other techniques — have achieved about 50% improvement.
Energy Recovery Rate from an Electric Air-Cycle System under the Cruising Altitude and Speed2019-01-19059/16/2019
A new electric air-cycle system of aircrafts is investigated focusing on energy recovery from the exhaust air. The working fluid of air has the higher energy level in the cabin than in the outside during the cruise because the outside air is at low pressure and low temperature. In the system, by setting a recovery turbine behind the cabin, the discharged energy can be collected, although the working fluid through the system has been only discharged from the cabin into the outside. We perform a thermodynamic cycle-analysis, where the temperature, pressure, entropy, etc. are calculated at each position of the cycle by considering the two pressure ratios of the compressors as variable parameters to show T-s diagram. In addition, we obtain an energy recovery rate of the recovery energy to the necessary power for the electric compressor. The energy recovery rate is roughly estimated 40-80% under the reasonable practical operating conditions.
Adachi, Takahiro, Seki, Naoki, Oyori, Hitoshi, Muraoka, Mikio
Combustion Gas Heat ExchangerTBMG-348978/1/2019
Two very challenging problems facing the U.S. and the world are energy security and global climate change, largely due to dependence on fossil fuels. Cost-effective technologies have been developed that are capable of substantial energy savings through improved energy efficiency.
Machining Capabilities Enhance Space-Related ProgramsTBMG-347367/1/2019
Insaco Quakertown, PA
An Innovative Electric Motor Cooling System for Hybrid Vehicles - Model and Test2019-01-10764/2/2019
Enhanced electric motor performance in transportation vehicles can improve system reliability and durability over rigorous operating cycles. The design of innovative heat rejection strategies in electric motors can minimize cooling power consumption and associated noise generation while offering configuration flexibility. This study investigates an innovative electric motor cooling strategy through bench top thermal testing on an emulated electric motor. The system design includes passive (e.g., heat pipes) cooling as the primary heat rejection pathway with supplemental conventional cooling using a variable speed coolant pump and radiator fan(s). The integrated thermal structure, “cradle”, transfers heat from the motor shell towards an end plate for heat dissipation to the ambient surroundings or transmission to an external thermal bus to remote heat exchanger. A complete lumped parameter numerical modelling was implemented to estimate the thermal behavior of the corresponding electric motor cooling system. Experimental and numerical results compare the temperature, heat flux, and cooling power measurements. For 250VA thermal load applied, the hybrid heat rejection strategy could save up to 33% of the power consumption while the operating condition is secured. Higher thermal loads can be handled through the combined passive and active pathways with minimum power consumption. Based on these findings, integrated electric motor cooling merits attention for further investigation through field testing, scaling, and utilization in other applications.
Shoai Naini, Shervin, Huang, Junkui (Allen), Miller, Richard, Wagner, John R., Rizzo, Denise, Sebeck, Katherine, Shurin, Scott
Development of a Correlation for Predicting Condensation Heat Transfer Coefficients for Refrigerant HFO-1234yf2019-01-01504/2/2019
Author has developed a correlation to predict condensation heat transfer coefficients for refrigerant condensation in an automotive parallel flow condenser. This is a first correlation in the open literature for HFO-1234yf to predict heat transfer coefficients for an automotive condenser. The system refrigerant mass flowrate was varied from 180 to 475 kg/hr; inlet refrigerant qualities from 1 to exit qualities of 0. The tests were conducted at an average condenser saturation temperature of 50°C and the oil circulation ratio was maintained at 3%.
Mathur, Gursaran D.
Metal 3D Printing for Complex Heat ExchangersTBMG-341544/1/2019
Renishaw West Dundee, IL
A Multi-Domain Component Based Modeling Toolset for Dynamic Integrated Power and Thermal System Modeling2019-01-13853/19/2019
Design of modern aircraft relies heavily on modeling and simulation for reducing cost and improving performance. However, the complexity of aircraft architectures requires accurate modeling of dynamic components across many subsystems. Integrated power and thermal modeling necessitates dynamic simulations of liquid, air, and two-phase fluids within vapor cycle system components, air cycle machine and propulsion components, hydraulic components, and more while heat generation of many on-board electrical components must also be precisely calculated as well. Integration of these highly complex subsystems may result in simulations which are too computationally expensive for quickly modeling extensive variations of aircraft architecture, or will require simulations with reduced accuracy in order to provide computationally inexpensive models. As such, a need for software toolsets with the ability to model complex aircraft architectures with accurate calculations while maintaining high computational speeds is apparent. This paper details the development of the ATTMOSphere toolset which enables modeling of electrical, mechanical, thermal, fluid flow and heat transfer across a range of components applicable to integrated power and thermal systems. Graphical user interfaces provide user-friendly parameterization of components, as well as sizing of many of the available components. All ATTMOSphere components operate within universal mechanical, thermal, electrical, and fluid domains allowing for seamless integration of components across many architectures, providing end-users with the ability to simultaneously model vapor cycle systems, air cycle systems, pumped refrigeration systems, and other power and thermal systems along with their interactions with parallel subsystems. This paper provides details of the components developed in ATTMOSphere along with examples of user interfaces and design codes. Demonstration models are presented to illustrate the integrated dynamic analysis capability of the toolset.
McCarthy, Patrick Thomas, McCarthy, Kevin, Hasan, Maher, Boyd, Michelle, Chang, Michael, Walters, Eric, Niedbalski, Nicholas
A Dynamic Two-Phase Component Model Library for High Heat Flux Applications2019-01-13863/19/2019
Pumped two-phase systems using mini or microchannel heat sink evaporators are prime candidates for high heat flux applications due to relatively low pumping power requirements and efficient heat removal in compact designs. A number of challenges exist in the implementation of these systems including: ensuring subcooled liquid to the pump to avoid cavitation, avoiding dry out conditions in heat exchangers that can lead to failures of the components under cooling, and avoiding flow instabilities that can damage components in an integrated system. To reduce risk and cost, modeling and simulation can be employed in the design and development of these complex systems, but such modeling must include the relevant behavior necessary to capture the above dynamic effects. To this end, a component model library has been developed in this work that demonstrates the ability to model dynamic and steady-state flow characteristics commonly observed in pumped two-phase refrigeration systems using microchannel heat sinks. The library is comprised of components that can either be used to model individual components or be coupled with other components to form an integrated system. The dynamic model of the microchannel cold plate component is based on common formulations of the time dependent mass, momentum, and energy balances, which are solved using the finite volume method to capture the two-phase flow behavior. Additionally, to accurately capture pressure drop and heat transfer, friction factors and heat transfer coefficients are based on correlations that compare well with a comprehensive list of academic publications. The mathematical description of the components, the implementation through Simulink and graphical user interfaces, and the application of the toolset will be presented herein. Comparison to hardware results will be shown along with verification of the tool’s ability to capture critical pumped two-phase phenomena such as dry out and flow instabilities.
Hodson, Stephen, McCarthy, Kevin, McCarthy, Patrick, Mudawar, Issam
Ruggedizing Commercial-Grade Computers into MIL-Hardened Systems19AERP02_012/1/2019
As performance capabilities for embedded computing products expand, the requirements for commercial-grade and MIL ruggedized systems blur into similar specifications. There are increasing demands to take feature-rich, successful industrial/commercial enclosure systems into MIL or other harsh environment applications. Similarly, engineers are designing up-front computing platforms that they can expand into harsher environments.
Thinking Ahead Thermally: A Guide to Thermal Management Considerations for Medical Devices, Part 1TBMG-3326511/1/2018
The medical device and engineering industry continues to grow and evolve year over year. As technology improves, the population expands, and the depth and breadth of medical knowledge and treatments grow, so does our need for better devices and equipment. As such, current trends spanning all industries, like electronics getting smaller and more powerful, as well as increased focus on improved customer experience, have greater implications and challenges for the medical industry. Should a device fail, a patient's well-being could be endangered. Additionally, medical devices need to be portable, costs need to be judiciously managed so that treatment can be made available to the populace, and reliability is crucial.
Reliability Case Analysis of an Autonomous Air Cooling System (AACS) for Aerospace Applications2018-01-191610/30/2018
Current More Electric Aircraft (MEA) utilize Liquid Cooling Systems (LCS) for cooling on-board power electronics. In such LCS, coolant pipes around the structure of the aircraft are used to supply water glycol based coolant to sink heat from power electronics and other heat loads in the electronic bay. The extracted heat is then transferred to ram air through downstream heat exchangers. This paper presents a reliability examination of a proposed alternative Autonomous Air Cooling System (AACS) for a twin engine civil MEA case study. The proposed AACS utilizes cabin air as the coolant which is in turn supplied using the electric Environmental Control System (ECS) within the MEA. The AACS consists of electrical blowers allocated to each heat load which subsequently drive the outflow cabin air through the heat sinks of the power electronics for heat extraction. No additional heat exchanger is required after this stage in which the heated air is directly expelled overboard. One key advantage is the avoidance of liquid coolant leakage with the removal of liquid coolant from the MEA. It is necessary that the expected reliability of the AACS is in line with the equivalent LCS and is compliant with Federal Aviation Administration/previous Joint Aviation Authorities (FAA/JAA) reliability limits. Accordingly, this paper evaluates the reliability of the proposed AACS as well as the subsequent operation of safety critical components of the ECS and Electrical Power System (EPS) that the AACS is cooling. The analysis results show that the proposed AACS can provide comparable reliability to an LCS and is expected to be compliant with FAA/JAA reliability limits.
Fong, Chung Man, Norman, Patrick, Seki, Naoki
NASA's Robotic Sniffer Finds Space Station LeakTBMG-328369/1/2018
Stanford Research Systems Sunnyvale, CA
Theoretical Analysis of High Thermal Conductivity Polymer Composite Fin Based Automotive Radiator under Forced Convection2018-28-00997/9/2018
Though high thermal conductivity polymer composites are prepared based on the thermal requirements, the effectiveness and overall heat transfer performance of the radiators have to be addressed comprehensively to validate the concerned efforts taken to prepare the high thermal conductivity polymer composites. In this article, theoretical analysis on the thermal performance of the cross flow type heat exchanger under convection is performed only by concentrating on the term thermal conductivity of the material. Micro channel based geometry is extracted from the given heat exchanger problem to reduce the complexities of simulation. The term cooling system performance index (CSPI) is used to achieve the expected targets in the present investigation. For shorter fins, the effect of thermal conductivity on the cooling system performance index under lower Reynolds number is insignificant. Further discussions on effect of thermal conductivity on various cases are presented with brief explanations.
Vadivelu, M A, Ramesh Kumar, C, Naiju, C D
Cryo-Fluid Capacitor (CFC)TBMG-290346/1/2018
NASA’s Kennedy Space Center (KSC) has created the Cryo-Fluid Capacitor (CFC) that capitalizes on the energy storage capacity of liquefied gases, and the relative simplicity of high-pressure gas bottles while limiting the downfalls associated with both methods. By exploiting a unique attribute of nanoporous materials — aerogel, in this case — fluid commodities such as oxygen, hydrogen, methane, etc. can be stored in a molecular surface adsorbed state at densities on par with liquid, at low to moderate pressure, and then supplied as a gas, on-demand, to a point of interest.
Magnetic Induction Heating of Space Foods During Dispensing Under Weightless ConditionsTBMG-290516/1/2018
Hot foods are psychologically pleasing. Food heating systems are currently part of the astronaut feeding program. An electrical method of heating foods during dispensing in space uses magnetic induction heating. The process is up to 95% efficient in converting electricity into food heat during the process of dispensing. There is no direct contact between the electrical source and the food.
2021-12-29.TEST Towards Optimal Performance of a Thermoelectric Generator for Exhaust Waste Heat Recovery from an Automotive Engine2018-01-00504/3/2018
Thermoelectric generator has very quickly become a hot research topic in the last five years because its broad application area and very attractive features such as no moving parts, low maintenance, variety of thermoelectric materials that total together cover a wide temperature range. The biggest disadvantage of the thermoelectric generator is its low conversion efficiency. So that when design and manufacture a thermoelectric generator for exhaust waste heat recovery from an automotive engine, the benefit of fuel consumption from applying a thermoelectric generator would be very sensitive to the weight, the dimensions, the cost and the practical conversion efficiency. Additionally, the exhaust gas conditions vary with the change of engine operating point. This creates a big challenge for the design of the hot side heat exchanger in terms of optimizing the electrical output of the thermoelectric generator during an engine transient cycle. Based on experimental work and a validated thermoelectric generator dynamic model, the authors have identified a few issues that have big impact on the thermoelectric generator performance for automotive applications. Potential solutions also have been proposed and discussed in this paper. They include module level optimization, heat exchanger design optimization in terms of fin thermal resistance for a transient cycle, assembly and interface optimization aims for compact size and minimized contact thermal resistance, optimization of the number of modules for total maximum power output etc.
Yang, Zhijia, Stobart, Richard, Lan, Song, Mason, Byron, Winward, Edward
Transient Analysis of Natural Convection around a Pair of Circular Cylinders inside a Square Enclosure2018-01-07764/3/2018
Heat exchangers are widely used in various transportation, industrial, or domestic applications such as thermal power plants, means of heating, transporting and air conditioning systems, electronic equipment and space vehicles. In all these applications improvements in the efficiency of the heat exchangers can lead to substantial cost, space and material savings. Hence considerable research work has been done in the past to seek effective ways to improve the efficiency of heat exchangers. In this paper the effect of natural convection is justified between exterior solid wall surfaces and the surrounding air inside the enclosure. Designing of electronic devices, heavy industrial equipments such as boilers, turbines etc. and building aerodynamics are some of the real world application associated with this study. The referred investigation includes the phenomenon of natural convection process to analyses the pattern of heat transfer characteristics inside a square enclosure with two circular cylinders placed at different position inside it. Maximum heat exchange zones are identified so that goal of effective heat transfer can be achieved which helps the heat exchangers to work efficiently at every condition. However, in the present work only unsteady state natural convection technique has been considered. The study of unsteady state natural convection in a square enclosure with conjugate boundary condition is done numerically. The analysis is performed on a square enclosure within which are placed two circular cylinders eccentrically. The enclosure walls are maintained at low temperature to that of cylinders such that a temperature difference is maintained between both the bodies. The cylinders are tilted at different angles inside the enclosure. A transient state 2-D numerical investigation is conveyed for air as an enclosed fluid. The Rayleigh number is varied in the range of 103 to 106 and the results are summarized in a relative manner. The value of Prandtl number is kept constant i.e. 0.71 corresponding to that of the air. The effect of orientation of the two cylinders and the outcome of the variation of Rayleigh number is calculated with the help of corresponding streamlines, and temperature distribution.
Tomar, Mukul, Kumar, Naveen, Malhotra, Aahan
Development of a Simulation Tool for High Capacity Metal Foam Heat Exchanger with Phase Change Material2018-01-07834/3/2018
Metal foam with their high porosity and heat storage capacity can be combined with phase change materials to be a powerful heat storage device. Numerical simulations of metal foam behavior can be challenging due to their complex geometric patterns necessitating high mesh requirements. Furthermore, simulations of the inner workings of a metal foam heat exchanger comprising of a large number of individual metal foam canisters can be impossible. The objective of the current work is to develop a computational model using a proprietary CFD tool Simerics-MP/Simerics-MP+® to simulate the workings of a metal foam heat exchanger with phase change element. A heat transfer coefficient capturing this heat transfer between wax and metal is used to formulate the “simplified” mixture model. The versatility of the proposed model is in the universality of its application to any shape or structure of metal foam. The computational model developed is tested to replicate the results of the 3D simulation. Very good agreements for the coolant temperature rise between the model and 3D simulation are obtained. Metal foam heat exchangers comprising of 89 such individual single metal foam canisters are simulated using the “simplified” model. Different arrangements of the single metal foam canisters to make up the metal foam heat exchanger are explored. Simulation results show pure steel has a better heat transfer performance, followed by metal foam canister with phase change material and finally aluminum. However, weight and other material considerations can make the metal foam canisters a practical alternative for effective heat storage.
Srinivasan, Chiranth, Slike, Jody, Wang, De Ming, Gao, Haiyang
A System-Level Approach to the Development of Optimized Waste Heat Recovery Exhaust Evaporators2018-01-13654/3/2018
This work presents a system-level methodology developed to identify the optimum design of heat exchangers for Organic Rankine Cycle (ORC) Waste Heat Recovery Systems (WHRS) for automotive applications. The optimization of the evaporators is done following an iterative system-level approach, where system and vehicle outputs, such as the Fuel economy (FE) and the System Payback Period are the objects of study. A 1D software has been developed to run an algorithm that, fed with corroborated assumptions, calculates the efficiency of the ORC cycle, the WHRS power output, the WHRS payback period, the FE potential and the Fuel Savings per year - hereby FSPY - for different sets of evaporator designs. The algorithm identifies the optimum trade-off for evaporator efficiency, pressure drop, weight and cost to maximize the system FSPY. The concept of the evaporator is a counter cross-flow heat exchanger; this is, the exhaust gas flows all along the outer case across the internal tubes. The working fluid flows within the tubes transversally in a meander path, in an overall counter current arrangement. There are several geometrical parameters open for optimization, such as the evaporator aspect ratio, cross section vs. length trade-off, arrangement of the tubes, shape of the outer case, number and diameter of the tubes, corrugation of the tubes, transversal and longitudinal corrugation pitch, etc. The resultant performance, size, weight and cost of the heat exchanger depend on which set of parameters is chosen. Moreover, every resultant heat exchanger output is linked in such a way that the optimum trade-off is not trivial.
Folgueira, Adrian, Teniente, Jorge, Carballido, Roman
Exhaust Heat Recovery System Study in Internal Combustion Engines2018-01-13744/3/2018
Strict regulations exist in different countries with respect to vehicular emissions by their respective government bodies requiring automakers to design fuel-efficient vehicles. Fuel economy and carbon emission are the main factors affecting these regulations. In this competitive industry to make fuel efficient vehicles and reduce Green House Gas (GHG) emissions in internal combustions has led to various developments. Exhaust Heat Recovery System (EHRS) plays a vital role in improving powertrain efficiency. In this system, heat rejected by the engine is reused to heat the vehicle fluids faster (for example, engine coolant, engine oil, etc.) correspondingly reducing harmful gas emissions. In internal combustion engines, generally only 25% of the fuel energy is converted into useful power output and approximately 40% of it is lost in exhaust heat. Certain studies show that by using the EHRS, the power output can be increased to 40% and the heat loss can be reduced to as much as 25%. The purpose of this study is to make use of this lost energy and convert most of it into useful energy. The thermodynamic properties and fuel consumed during the warmup period were analyzed to measure the improvement in the engine efficiency. The design was implemented on a Briggs and Stratton Junior 206cc engine. This system includes the use of heat exchangers. The main goal of this study is to develop a robust EHRS design and compare it with the baseline engine configuration to see the thermal and fuel economy improvement during warm up.
Rai, Shashank, Arslan, Selin, Jawad, Badih
Numerical Simulation of Oil Separator of an Automotive Swash Type Compressor2018-01-04884/3/2018
In the present study a numerical investigation is performed by using computational fluid dynamics (CFD) aiming to figure out and maximize the separation efficiency of an oil separator by changing the various design parameters. A typical automotive swash plate type compressor is chosen for this numerical investigation. Basically oil separation becomes very important where oil return is quite problematic due to the multiple constraints in piping layout design. Efficient oil separation makes the compressor lubrication easy and prevents from seizing during running. It also enhances the heat transfer from heat exchanger by reducing or separating oil from the refrigerant flowing in the air conditioning (AC) circuit. A computational method is proposed to analyze an oil separator fitted in a swash plate compressor. Eulerian multiphase model is employed to simulate the oil and refrigerant mixture model. Separation efficiency is predicted numerically by changing the nozzle diameter, separator diameter and height. Further to that a different approach (based on density difference) is utilized to maximize the separation percentage. It is observed that by employing such approach separation efficiency increased drastically. Thus a numerical method is established for predicting oil separation which becomes key element in the early stage of compressor design to avoid field failure.
Sen, Somnath
2021-12-29.TEST Micro-Channel Heat Exchanger: An Exhaust Waste Heat Recovery Device2018-01-00524/3/2018
Almost one-third of the fuel energy is wasted through the exhaust of a vehicle. An efficient waste heat recovery (WHR) process will undoubtedly lead to improved fuel efficiency and reduced greenhouse gases (GHG) emission. Currently, there are multiple WHR technologies that are being investigated by various entities in the auto industry. One relatively simple device to extract heat energy from the exhaust is a heat exchanger. Heat exchangers are used in some automotive applications to transfer heat from the hot exhaust gas to the colder coolant fluid to raise the coolant temperature. The warmer coolant fluid can be used for several purposes such as; faster heating of the engine’s lubrication oil and transmission fluids during cold starts, and faster cabin heating, which in turn, can potentially improve the overall engine efficiency and reduce exhaust emissions. Currently, in the US market place, hybrid vehicles, such as the Toyota Prius and Chevy Malibu, use heat exchangers as an integral part of their WHR systems. While traditional heat exchangers have been studied and employed in some automotive applications, the use of a micro-channel heat exchanger (MCHX) is a relatively new concept. Especially, in the realm of automobiles, use of micro-channel heat exchanger is unprecedented. As the name suggests, the micro-channel heat exchanger may provide a significant advantage in terms of packaging compared to a traditional heat exchanger when higher thermal performance is desired. However, the MCHX design has to be optimized for a particular application to avoid creating high backpressure in the exhaust system. In this paper, the design and performance of a micro-channel heat exchanger is described for a range of exhaust mass flows and temperatures. Predicted results from two 1-D models developed using the GT SUITE and Excel are compared and validated against preliminary experimental results from a prototype MCHX design. Finally, the thermal performance of the MCHX is compared to other traditional heat exchangers.
Sahoo, Dipankar, Gardner, Timothy, Whyatt, Greg
2021-12-29.TEST Correlation for Predicting Two-Phase Flow Boiling Heat Transfer Coefficients for Refrigerant HFO-1234yf2018-01-00554/3/2018
Author has developed a correlation to predict flow boiling heat transfer coefficients for refrigerant evaporating in an automotive evaporator. This is a first correlation in the open literature for HFO-1234yf to predict heat transfer coefficients for automotive evaporator. The refrigerant mass flux was varied from 500 to 1200 kg/m2.s; heat flux was varied from 2 to 6.2 kW/m2; inlet refrigerant qualities from 0 to 40% and exit qualities of about 95%. The tests were conduct at 4.4 °C and the oil circulation ratio was maintained at 3%. Experimental data has been used with MINITAB software, Version 16.1.0 to develop this correlation. Multivariate nonlinear regression analysis has been done to develop this correlation. Experimental data along with refrigerant properties, hydraulic diameter that affects Reynolds number, Prandtl number and other appropriate variables have been used to develop this correlation. Details of the newly developed correlation have been presented in the paper. The developed correlation will be used to predict flow boiling heat transfer coefficients for HFO-1234yf for automotive evaporator (laminate evaporators). The following is the developed correlation for HFO-1234yf: hexp/hl = 2.8738 (1/Xtt)0.109. The developed correlation predicts the experimentally obtained data within ±23%. Further studies are planned to improve this correlation and to compare predictions with other correlations in the open literature; and to study the influence of amount of lubricant (%) on flow boiling heat transfer coefficients.
Mathur, Gursaran D.
Statistical Model to Predict Air Side Pressure Drop for Heat Exchangers2018-01-00814/3/2018
In a typical ground vehicle, airflow enters engine compartment through grille and carries heat from the engine, cabin and other auxiliaries through heat exchangers such as radiator, condenser, oil cooler and charge air cooler respectively. The amount of airflow entering the engine compartment is governed by their individual resistances, the grille and engine compartment resistances. Also, this flow adds to drag and deteriorates overall aerodynamic efficiency. It is known as cooling drag which contributes to 8 to 12 percent of overall drag. Aerodynamics and Front End Air Flow (FEAF) development happens through CFD and it demands accurate heat exchanger pressure drop data which is usually obtained from supplier at very early stages of a vehicle development. Historically, this data is found to have significant variations compared to in-house test data. To have an accurate pressure drop data for CFD simulation, a predictive (statistical) heat exchanger model was built around Kriging Gaussian method. In this study, the heat exchanger geometry was parameterized into six different parameters mainly as fin-density, fin height, fin thickness, fin louvers, tube height and core thickness. The porosity/air side pressure drop performance of any heat exchanger depends on one of the pattern of these parameters. This pattern repeats across the width and height of a heat exchanger and pressure drop across this individual pattern signifies total pressure drop of the entire heat exchanger. The first part of the paper discusses about establishing a correlation between in-house heat exchangers test and CFD for couple of heat exchangers with simplified geometries. Later sections discuss about setting up full factorial Design of Experiments (DOE), CFD models creation and analysis. In this work, DOE was used to generate data points for unique combinations of parameters and pressure drop were obtained across these data points. These parameters and data points were statistically analyzed by fitting Kriging response, thereby obtained a response surface, which was used as a tool to predict the pressure drop for any possible combinations of the heat exchanger parameters.
Dube, Pradip, Hiravennavar, Sadashiv, Ali Z, Abbas
Application of Intermediate Vapor Bypass to Mobile Heat Pump System: Extending Operating Range to Lower Ambient Temperature with Low Pressure Low GWP Fluid2018-01-00714/3/2018
With market share of electric vehicles continue to grow, there is an increasing demand of mobile heat pump for cabin climate control, as it has much higher energy efficiency when compared to electric heating and helps to cut drive range reduction. One big challenge of heat pump systems is that their heating capacities drop significantly when operating at very low ambient temperature, especially for those with low pressure refrigerants. This paper presents a way to improve low ambient temperature heating performance by using intermediate vapor bypass with the outdoor heat exchanger, which works as an evaporator in heat pump mode. The experimental results show a 35% increase of heating capacity at −20 °C ambient with the improved system as compared to the baseline, and heating performance factor also slightly increased when the system is working at higher ambient temperature to reach the same heating capacity as the baseline. Further improvement of system design and heat exchanger optimization is underway.
Feng, Lili, Hrnjak, Predrag
Implementation of Reinforcement Learning on Air Source Heat Pump Defrost Control for Full Electric Vehicles2018-01-11934/3/2018
Air source heat pumps as the heating system for full electric vehicles are drawing more and more attention in recent years. Despite the high energy efficiency, frost accumulation on the heat pump evaporator is one of the major challenges associated with air source heat pumps. The evaporator needs to be actively defrosted periodically and heat pump heating will be interrupted during defrosting process. Proper defrost control is needed to obtain high average heat pump energy efficiency. In this paper, a new method for generating air source heat pump defrost control policy using reinforcement learning is introduced. This model-free method has several advantages. It can automatically generate optimal defrost control policy instead of requiring manually determination of the control policy parameters and logics. More measurement results can be incorporated into the defrost control policy without too many changes in the reinforcement learning algorithm so that the control policy can be better optimized under wider range of working conditions. The learning features also enable the controller to adapt to the system differences and changes which are impossible to predict a priori when designing defrost control policy. The algorithm was validated using experimentally obtained heating capacity and COP data in frost growth cycle of a heat pump under different conditions. The results showed that reinforcement learning can be used to generate defrost control policy that optimizes energy consumption for various working conditions.
Zhu, Jingwei, Elbel, Stefan
Accelerated Corrosion Testing of Automotive Evaporators and Condensers2018-01-00624/3/2018
There is an ongoing effort in the industry to develop an accelerated corrosion test for automotive heat exchangers. This has become even more important as automakers are focusing on corrosion durability of 15 years in the field versus current target of 10 years. To this end an acid immersion test was developed and reported in a previous paper for condensers (1). This paper extends those results to evaporators and establishes the efficacy of the test using these results and those reported in the literature. The paper also discusses variability in corrosion test results as observed in tests such as ASTM G85:A3 Acidified Synthetic Sea Water Test (SWAAT), and its relation to field durability.
Rungta, Ravi, Pandit, Noori
System Characteristics of Direct and Secondary Loop Heat Pump for Electrical Vehicles2018-01-00634/3/2018
The electricity energy consumption for passenger cabin heating can drastically shorten the driving range for electric vehicles in cold climates. Mobile heat pump system is considered as an effective method to improve heating efficiency. This study investigates the system characteristics of mobile heat pump systems for electrical vehicle application. Based on KULI thermal management software, simulation models including HFC-R134a direct heat pump (DHP) and secondary loop heat pump (SLHP) were developed. The secondary loop employed in the SLHP includes a coolant pump, an indoor heater core and a plate heat exchanger, instead of an indoor condenser in the DHP. The use of a secondary loop has advantages to improve air outlet temperature uniformity. The simulation models were verified by measured data obtained from calorimeter experiments. By adopting simulation models, the effects of indoor and outdoor temperatures on system performance and cycle characteristics were discussed. Results show that the increase of indoor temperature will largely decrease the system efficiency, and varied outdoor temperature has a big impact on heating capacity. Then the comparison simulations between DHP and SLHP were conducted, to determine the effect of the secondary loop on heating performance. Results show that the use of a secondary loop is severely harmful to system efficiency, but has little effect on heating capacity. Furthermore, the impact of coolant flow rate on the capacity and COP was discussed, and heat transfer effectiveness of heater core and plate heat exchanger were also evaluated.
Wang, Dandong, Gao, Tianyuan, Li, Wanyong, Yang, Yun, Shi, Junye, Chen, Jiangping
Aerodynamic Investigation of Cooling Drag of a Production Pickup Truck Part 1: Test Results2018-01-07404/3/2018
The airflow that enters the front grille of a ground vehicle for the purpose of component cooling has a significant effect on aerodynamic drag. This drag component is commonly referred to as cooling drag, which denotes the difference in drag measured between open grille and closed grille conditions. When the front grille is closed, the airflow that would have entered the front grille is redirected around the body. This airflow is commonly referred to as cooling interference airflow. Consequently, cooling interference airflow can lead to differences in vehicle component drag; this component of cooling drag is known as cooling interference drag. One mechanism that has been commonly utilized to directly influence the cooling drag, by reducing the engine airflow, is active grille shutters (AGS). For certain driving conditions, the AGS system can restrict airflow from passing through the heat exchangers, which significantly reduces cooling drag. The difference in drag between the AGS vanes being open and closed is referred to as AGS drag. Another vehicle component that influences the cooling drag is chin spoilers. Chin spoilers are components that lie within cooling interference airflow paths for many vehicles and can be used/designed to affect cooling drag. This study focuses on the influence of the chin spoiler on cooling and AGS drag of a production-level F-150 in a wind tunnel test environment. The chin spoiler variables tested were height and curvature (sweep). All experiments were conducted in both stationary and moving ground wind tunnel conditions at 80 MPH between yaw angles of ±7°. In addition to overall vehicle drag coefficients, surface pressures at discrete locations and cooling pack airflow rates were measured to provide better insight into the internal and external airflow behavior. Ground and yaw conditions were shown to heavily influence chin spoiler design. Cooling and AGS drag were also strongly influenced by chin spoiler face height at 0° yaw; at higher angles of yaw this influence was lessened but was still present. Chin spoiler sweep was shown to have a significantly lesser (though non-negligible) impact than chin spoiler face height on all metrics in all conditions.
Larson, Levon, Woodiga, Sudesh
Impact on Fouling of Different Exhaust Gas Conditions with Low Coolant Temperature for a Range of EGR Cooler Technologies2018-01-03744/3/2018
Degradation of anti-pollutant devices must be taken into account in design so durability of the function is guaranteed over the vehicle lifetime. As for NOx reduction of diesel engines, Exhaust Gas Recirculation (EGR) systems are a well-known and robust solution. However, exposure of the EGR cooler inside this system to the exhaust gas conditions leads to a degradation of its function, affecting to the EGR rate and therefore to potential for NOx reduction. So, sizing and technology of these heat exchangers must be selected to avoid malfunction during vehicle operation. Current scenario in Europe with new homologation cycles and focus on NOx emissions of diesel vehicles under real driving conditions is challenging for the design of EGR systems. This leads to the increase of the areas of the engine map using EGR. Moreover new homologation includes also the use of low ambient temperature. In this context, it is important to understand the impact of critical exhaust gas conditions coupled with low EGR coolant temperature. That is to say, the use of low coolant temperature adds condensation to the typical phenomenon of soot deposition, thus making it even more critical since condensation puts in to the thermophoresis a significative impact in the formation of the fouling layer. As the impact varies according to the heat exchanger technology, a set of tests has been performed in order to analyze the effect in the two main functions: thermal efficiency and pressure drop. Six different technologies have been tested: from round to rectangular corrugated tubes, and tubes with fins with different design parameters. Most critical conditions of exhaust gas have been taken in terms of opacity and HC content, as well as the effect of using nominal coolant temperature versus low coolant temperature have also been analyzed. This study enables to discriminate most suitable technologies for different engine conditions. Further work is planned in order to study soot characterization and representativeness in lifetime of the vehicle.
Bravo, Yolanda, Arnal, Cristina, Larrosa, Carmen, Climent, Hector
Development of an Integrated Virtual Engine Model to Simulate New Standard Testing Cycles2018-01-14134/3/2018
The combination of more strict regulation for pollutant and CO2 emissions and the new testing cycles, covering a wider range of transient conditions, makes very interesting the development of predictive tools for engine design and pre-calibration. This paper describes a new integrated Virtual Engine Model (VEMOD) that has been developed as a standalone tool to simulate new standard testing cycles. The VEMOD is based on a wave-action model that carries out the thermo-and fluid dynamics calculation of the gas in each part of the engine. In the model, the engine is represented by means of 1D ducts, while the volumes, such as cylinders and reservoirs, are considered as 0D elements. Different sub-models are included in the VEMOD to take into account all the relevant phenomena. Thus, the combustion process is calculated by the Apparent Combustion Time (ACT) 1D model, responsible for the prediction of the rate of heat release and NOx formation. Experimental correlations are used to determine the rest of pollutants. In order to predict tailpipe pollutant emissions to the ambient, different sub-models have been developed to reproduce the behavior of the aftertreatment devices (DOC and DPF) placed in the exhaust system. Dedicated friction and auxiliaries sub-models allow obtaining the brake power. The turbocharger consists of 0D compressor and turbine sub-models capable of extrapolating the available maps of both devices. The VEMOD includes coolant and lubricant circuits linked, on the one hand, with the engine block and the turbocharger through heat transfer lumped models; and on the other hand with the engine heat exchangers. A control system emulating the ECU along with vehicle and driver sub-models allow completing the engine simulation. The Virtual Engine Model has been validated with experimental tests in a 1.6 L Diesel engine using steady and transient tests in both hot and cold conditions. Engine torque was predicted with a mean error of 3 Nm and an error below 14 Nm for 90 % of the cycle duration. CO2 presented a mean error of 0.04 g/s, while during 80 % of the cycle, error was below 0.44 g/s.
Martin, Jaime, Arnau, Francisco, Piqueras, Pedro, Auñon, Angel
Parallel Thermal Management System of the Water Medium Retarder2018-01-07774/3/2018
The thermal management system of the water medium retarder using engine coolant (water and ethylene glycol) as transmission medium, omits oil-water heat exchanger in the structure. When the hydraulic retarder is operated, the valve is connected with the retarder and water pump, and then the engine coolant enters the working chamber. The kinetic energy of the vehicle is converted into internal energy of the coolant, and the heat is discharged to the external environment through the engine thermal management system. The braking torque of the water medium hydraulic retarder is determined by the water medium flow rate in the working chamber. The smaller the valve opening degree, the greater the braking torque and the faster the heating transmission fluid. Small valve opening is not conducive to the loss of heat. It will affect the normal working of the engine and hydraulic retarder. In this paper, the thermal management system of the water medium hydraulic retarder is independent of the engine. Hydraulic retarder can be controlled individually so that to improve the auxiliary braking performance. Firstly, the independent thermal management system is designed according to the heat dissipation requirement of the hydraulic retarder. Secondly, the heat transfer of the hydraulic retarder thermal management system is analyzed. Finally, compare to the thermal management system of the traditional water medium retarder and the paper. The results show that the thermal management system of parallel water medium hydraulic retarder can effectively use the radiator cooling capacity, and reduce the working temperature of the water hydraulic retarder.
Gao, Xin, Lei, Yulong, Chen, Wei, Cui, Guokai, Zhong, Lei
Critical Cooling in Medical Devices – Part 2TBMG-287494/1/2018
The need for thermal management continues to increase in the medical industry. Active thermal management is critical for applications such as patient core temperature management, skin cooling, medical device cooling, and laboratory equipment cooling. Medical device designers need highly efficient and compact cooling systems that can be integrated into their systems, often with the option of battery power for mobility.
Simplified Method for Uniformly Distributing Flow Within a Fluid Layer of a Multi-Layer Heat ExchangerTBMG-285683/1/2018
In multi-layer and multi-fluid plate and fin heat exchangers, fluid ports are required to be located on the side of the heat exchanger. However, the fluid flow is perpendicular to the direction in which the fluid is introduced into the heat exchanger via the fluid port. In order to turn the flow to the correct direction within a fluid layer, angled fin sections are used. In heat exchangers that have “tented” ends, multiple angled fin sections are required. Often, five or more separate fin pieces are required per fluid layer. Such configurations result in increased part count, more complicated fabrication, and increased overall cost.
LOOP THERMOSYPHONS18AERP02_022/1/2018
Gravity-Driven Two-Phase Cooling for the 21st Century Two-phase cooling has been utilized in the electronics cooling industry for many decades, with possibly the most wellknown adaptation being the heat pipe. Heat pipes are capillary-driven, twophase devices that rely on the boiling and condensation of a working fluid to transfer heat significant distances with minimal temperature gradient. The flow of the working fluid inside of a heat pipe is facilitated by a capillary wick structure that relies on surface tension to return the condensed liquid to the heat generating components. Heat pipes have found their way into a large number of industries and applications because of their high performance, high reliability, and low cost. Unfortunately, as the electronics industry's insatiable quest for smaller, higher-powered devices soldiers on, the discrete cooling power of the heat pipe approaches obsolescence. Cue the heat pipe's lesser-known cousin; the loop thermosyphon (or thermosiphon). Loop thermosyphons (LTS) are gravity-driven, two-phase devices that operate in a similar manner to a heat pipe in so far as a working fluid is evaporated and condensed in a closed loop to transfer heat over a given distance. Some readers may be more familiar with a traditional thermo sy phon, shown in Figure 1a, where the liquid and vapor occupy a single tube. Loop thermosyphons, as shown in Figure 1b (and as the name suggests), operate in more of a loop fashion where the liquid and vapor travel more independently.
Loop ThermosyphonsTBMG-283862/1/2018
Two-phase cooling has been utilized in the electronics cooling industry for many decades, with possibly the most well-known adaptation being the heat pipe. Heat pipes are capillary-driven, two-phase devices that rely on the boiling and condensation of a working fluid to transfer heat significant distances with minimal temperature gradient. The flow of the working fluid inside of a heat pipe is facilitated by a capillary wick structure that relies on surface tension to return the condensed liquid to the heat generating components. Heat pipes have found their way into a large number of industries and applications because of their high performance, high reliability, and low cost. Unfortunately, as the electronics industry’s insatiable quest for smaller, higher-powered devices soldiers on, the discrete cooling power of the heat pipe approaches obsolescence.
Cryo-Fluid Capacitor (CFC) for Solid-State Storage and Supply-on-Demand of Cryogenic FluidsTBMG-282952/1/2018
Storage and transfer of fluid commodities such as oxygen, hydrogen, natural gas, nitrogen, argon, etc. are absolute necessities in virtually every industry. These fluids are typically contained in one of two ways: as low-pressure cryogenic liquids, or as high-pressure compressed gases. Cryogenic liquids afford high energy and volume densities, but require complex storage systems to limit boil-off, need constant settling in zero-gravity environments, and are not well suited for overly dynamic situations where the tank orientation can change suddenly (in an airplane or car, for example). Conversely, high-pressure gas storage bottles are not affected by tank orientation, do not require settling, and can be kept at room temperature; they are considerably less complicated pieces of equipment. These vessels, however, are heavy due to the thick walls required to contain the high pressures, and storage densities — even at extreme pressures such as 10,000 psi — are dramatically lower.
Analysis of a Heat Exchanger for the Cooling Systems of a Vehicular Prototype2017-36-034711/7/2017
This work aims to study the selection of a heat exchanger available in the market with the objective of implementing it in a vehicle. The vehicle used for the tests was a prototype, developed by Formula UFMG team. It was made an experimental and a theoretical study in order to calculate the power of the CB600F engine to compare with the experimental study of heat dissipation of the selected heat exchanger. This comparison was made to check whether the heat exchanger reaches the vehicle’s requirements, and it has shown good convergence. The engine technical features were used in the theoretical studies, and thus the power was calculated. The experimental data were obtained by assembling the car in a roller dynamometer with the necessary instrumentation for these tests being performed. In these tests, the critical operation conditions of the vehicle were simulated, once the engine operates at a temperature of 95°C. For the experimental calculation of the dissipated heat by the radiator, experiments were carried out to obtain the water pump flow curve and the difference of the water inlet and outlet temperatures in the heat exchanger. It was concluded in the present work that this heat exchanger obtained satisfactory performance in the tests, proving that the radiator was correctly selected, since the vehicle was subjected to extreme conditions of use and did not overheat.
de Lima, Bruno Silva, de Oliveira, Rafael Megale, de Oliveira Moraes, Luiz Fernando, Araújo, Gustavo Abreu, de Almeida Carvalho, Gabriel Mendes
The Effect of Swirl on the Flow Uniformity in Automotive Exhaust Catalysts2017-01-238410/8/2017
In aftertreatment system design, flow uniformity is of paramount importance as it affects aftertreatment device conversion efficiency and durability. The major trend of downsizing engines using turbochargers means the effect of the turbine residual swirl on the flow needs to be considered. In this paper, this effect has been investigated experimentally and numerically. A swirling flow rig with a moving-block swirl generator was used to generate swirling flow in a sudden expansion diffuser with a wash-coated diesel oxidation catalyst (DOC) downstream. Hot-wire anemometry (HWA) was used to measure the axial and tangential velocities of the swirling flow upstream of the diffuser expansion and the axial velocity downstream the monolith. With no swirl, the flow in the catalyst monolith is highly non-uniform with maximum velocities near the diffuser axis. At high swirl levels, the flow is also highly nonuniform with the highest velocities near the diffuser wall. An intermediate swirl level exists where the flow is most uniform. To gain further insight into the mechanisms controlling flow redistribution, numerical simulations have been performed using the commercial CFD code STARCCM+. With no swirl, the central jet transverses the diffuser, and a drastic flow redistribution takes place near the monolith face due to its high resistance. Immediately downstream of the sudden expansion, the flow separates from the diffuser wall forming a separation zone around the central jet. Increasing swirl reduces the size of this separation zone, and eventually leads to the formation of the central recirculation zone characteristic of high swirl flows. At intermediate swirl levels, the size of the wall separation zone is reduced considerably, while the axial adverse pressure gradient is insufficient to cause a central recirculation. Such a flow regime occurs at relatively low swirl levels (S ~ 0.23). This may have positive implications for aftertreatment system design with low residual swirl levels from the turbine, which might be tuned by adjusting the distance between the turbine and the catalyst or employing guide vanes. The findings can be directly transferred to other aftertreatment systems with a catalyst or particulate filter. Moreover, swirling flows with an obstruction or a high resistance device downstream (e.g. a heat exchanger or filter) are present in many other applications such as cooling flows, combustion and turbomachinery. Therefore the results are relevant to a much wider research and industrial community.
Rusli, Ijhar H., Aleksandrova, Svetlana, Medina, Humberto, Benjamin, Stephen F.
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