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Viewing 61 to 90 of 10280
2016-04-05
Technical Paper
2016-01-0201
Armin Traussnig, Wilko Jansen, Heinz Petutschnig, Sepp Steiner, Petra Gruen
In order to meet current and future emission and CO2 targets, an efficient vehicle thermal management system is one of the key factors in conventional as well as in electrified powertrains. Global vehicle simulation is already a well-established tool to support the vehicle development process. In contrast to conventional vehicles, electrified powertrains offer an additional challenge to the thermal conditioning: the durability of E-components is not only influenced by temperature peaks but also by the duration and amplitude of temperature swings as well as temperature gradients within the components during their lifetime. Keeping all components always at the preferred lowest temperature level to avoid ageing under any conditions (driving, parking, etc.) will result in very high energy consumption which is in contradiction to the efficiency targets.
2016-04-05
Technical Paper
2016-01-1435
Amber Hall, Michael Kolich
Many studies have been conducted and supporting literature has been published to better understand thermal comfort for the automotive environment, particularly, for the HVAC system within the cabin. However, reliable assessment of occupant thermal comfort for seating systems has lacked in development and understanding. Evaluation of seat system performance in terms of comfort has been difficult to quantify and thus most tests have been established such that the hardware components are tested to determine if the thermal feature does no harm to the customer. This paper evaluates the optimal seat surface temperature to optimize human thermal comfort for an automotive seating system applications. The physiological responses and comfort obtained from human subjects are compared to seat surface temperatures & quality data verbatim responses of the seats.
2016-04-05
Technical Paper
2016-01-0200
Chunhui Zhang, Mesbah Uddin, Xu Song, Chen Fu, Lee Foster
Radiator is the key part in the cooling system of a vehicle. The cooling effectiveness of a radiator largely depends on the fresh airflow through it. Airflow speed, mass flow rate and flow-distribution or flow-uniformity over the radiator surface are the major operating parameters influencing the performance of a radiator. The mass of airflow coming from the front grill also plays an important role on the total drag of the vehicle. This paper presents computational studies aiming at improving the efficiency of the radiator and reducing the total drag of the vehicle simultaneously by manipulating the flow pattern approaching the radiator through the design of passive aerodynamic devices. The vehicle model considered is a Hyundai Veloster and all analyses were carried out using a commercial CFD code Star-CCM+ where the baseline model has a vertical radiator without an air-duct.
2016-04-05
Technical Paper
2016-01-0257
Lili Feng, Predrag Hrnjak
This paper presents the experimentally obtained performance characteristics of an air conditioning-heat pump system that uses heat exchangers from a commercially available Nissan Leaf EV. It was found that refrigerant charge needed for cooling operation was larger than that for heating function with the test setup. The effects of: a). indoor air flow rate, b). outdoor air flow rate, and c). compressor speed on heating capacity and energy efficiency were explored and presented. Appropriate opening size of expansion valve that controlled subcooling for better energy efficiency was discussed and results are presented. Expansion valve opening size also strongly affected charge migration. Warm-up tests at different ambient conditions showed the necessity of a secondary heater to be reserved for very low ambient temperature.
2016-04-05
Technical Paper
2016-01-0227
Kaushal Kumar Jha, Imran Shaik
Heat exchangers are thermoregulatory system of an automotive air conditioning system. They are responsible for heat exchange between refrigerant and air. Sizing of the heat exchanger become critical to achieve the required thermal performance. In the present paper, the behaviour of heat exchanger with respect to change in size is studied in detailed by developing a scaling model. The limited experiments have been conducted for different evaporators and condensers. Commercially available 1D tool GT Suite is used for simulations. Cool-3D is used to model the heat exchanger. The heat exchanger experimental thermal capacities are compared with the simulated values and a good agreement up to ±2.3% in the case of condensers and up to ±9% in the case of evaporators is found between the experiments and simulations. Then developed scaling model in GT Suite is used to study the thermal behaviour and pressure drops of heat exchanger while changing the size of the heat exchanger.
2016-04-05
Technical Paper
2016-01-0654
Lakshmaiah Brahmasani, K SARANGAPANI, Samson Solomon, Parvej khan
The paper presents the development of a rear powertrain cooling system of a minivan. The packaging of cooling system is such that the radiator faces towards the rear of the vehicle bumper which is opposite to the conventional rear cooling system (i.e. radiator faces towards the front of the vehicle to get ram air benefit). In small minivan, the space ahead of engine is used as floor for passenger foot. Due to these space constraint, the cooling system has no choice, but to move rear of the vehicle and above the departure plane to meet packaging requirements. Furthermore, in conventional rear cooling system, in front of the radiator, there will be engine and exhaust system, which heats up the air going to the radiator and reduces radiator cooling performance. Thus the cooling system is placed such that the radiator faces the rear bumper to draw in cooler air. In this condition we don’t depend on the ram air but on the fan to meet required airflow.
2016-04-05
Technical Paper
2016-01-0259
Kaushal Kumar Jha, Sarveshwar Reddy Mulamalla, Anil Anugu
The main function of an air conditioning system in a vehicle is to provide the thermal comfort to the occupant at minimum possible energy consumption in all environmental conditions. To ensure the best possible thermal comfort, air conditioning system is optimized on various parameters like heat load, air flow distribution, glass area, trim quality, insulation and cabin leak rate. A minimum cabin leakage is regulatory requirements to ensure the air quality of cabin. Anything above the minimum cabin leak rate ultimately turn into reduced thermal comfort and additional energy consumption. This additional energy consumption to maintain the required thermal comfort in the cabin due to cabin leakage affect the fuel efficiency severely. In the present study, the effect of cabin leakage on fuel efficiency and thermal comfort is studied in details by varying the cabin leakage through mechanical means. The cabin leakage is measured before and end of each experiments.
2016-04-05
Technical Paper
2016-01-0198
Sudhi Uppuluri, Hemant R Khalane, Yogesh Umbarkar, Ajay Naiknaware
Vehicle development teams struggle to optimize HVAC module performance for cold ambient (~ -20 deg. C) test cycles such as defrost and cabin warm-up. Engine heat rejection to coolant during cold starting plays critical role in HVAC / cabin heater performance. Measuring engine heat rejection at cold ambient is extremely difficult due to fast warm-up in fired conditions and longer lead time to test. Conventional approach adopts experimentation by tweaking engine calibration parameters to warm up coolant as fast as possible while meeting statutory requirements. This approach may not attain optimum performance of cabin heater and engine. In view of this, a novel approach is proposed to simulate and improve cold ambient warm-up predictions using 1D computational models. Initially an engine thermodynamic model was developed and validated for typical 2L gasoline turbocharged direct injection engine using commercial code Ricardo WAVE®.
2016-04-05
Technical Paper
2016-01-0252
Huize Li, Predrag Hrnjak
This paper presents the visualization of periodic reverse flow in tubes of an automobile microchannel evaporator. Two microchannel tubes in an off-the-shelf evaporator are modified so that the leading edges are transparent and the rest of the area remains unchanged, providing realistic air heating. Flow reversal is measured under various heat fluxes, and the pressure drops of these two transparent tubes and the entire heat exchanger are recorded simultaneously. The capacity degradation due to reverse flow is identified under each operating condition.
2016-04-05
Technical Paper
2016-01-0248
Mingyu Wang, Edward Wolfe, Timothy Craig, Omar Abdelaziz, Zhiming Gao
Without the waste heat available from the engine of a conventional automobile, electric vehicles (EVs) must provide heat to the cabin for climate control using energy stored in the vehicle. In current EV designs, this energy is typically provided by the traction battery. In very cold climatic conditions, the power required to heat the EV cabin can be of a similar magnitude to that required for propulsion of the vehicle. As a result, the driving range of an EV can be reduced very significantly during winter months, which limits consumer acceptance of EVs and results in increased battery costs to achieve a minimum range while ensuring comfort to the EV driver. To minimize the range penalty associated with EV cabin heating, a novel climate control system that includes thermal energy storage has been designed for use in EVs and plug-in hybrid electric vehicles (PHEVs). The system uses the stored latent heat of an advanced phase change material (PCM) to provide cabin heating.
2016-04-05
Technical Paper
2016-01-0180
Montassar Khammassi, Thierry Marimbordes, Judicael Aubry, Bertrand Barbedette, Mickael Cormerais, Cherif Larouci, Quentin Frossard
In order to cope with new regulations and find a better compromise between fuel consumption, pollutant emissions and comfort, thermal management technologies are getting more complex. This is especially true when it requires replacing a basic passive solution with a mechatronic system. A new Active Cooling Thermal-management (ACT) valve concept has been developed to specifically replace wax thermostat while keeping the same packaging and cost range and bringing closed loop temperature control, fast response time and precision. This new module is manufactured by assembling injected thermoplastic components. By essence it leads to dimension tolerances, deformation and wear over its life. Those uncertainties and deviations have to be taken into account when the nominal part is designed to ensure part efficiency till the end of its life.
2016-04-05
Technical Paper
2016-01-0182
Harish Kumar Gangwar, Ankur Sharma, S.B. Pathak, VIvek Dwivedi, Amit Nigam
Performance optimisation of electronically controlled Hydraulic fan drive (HFD) used in commercial application Abstract Ever tightening emission limits and constant pressure for increase engine power are resulting in increased engine operating temperature. This coupled with continuous drive for fuel economy improvement because of the stiff competition are forcing OEMs to explore alternative cooling solutions resulting in less power take off and quick response as cooling requirement shoots up. Aim of this paper is to analyse the relative benefits of incorporating a new cooling fan drive system concept over conventional viscous fan driven cooling system with step-less variable speed control independent of engine speed variation. Hydraulic fan drive system control fan rpm based on the fluid temperature as compared to air temperature in viscous coupling fan drive system. HFD system provides quick response when increase coolant temperature observed.
2016-04-05
Technical Paper
2016-01-0188
Elankathiravan Mathivanan, Liping Liu
In the present work, the effect of various nanofluids on automotive engine cooling will be experimentally studied. Al2O3, TiC, SiC, MWNT (multi-walled nanotube) and SiO2 nanoparticles ranging between 1 and 100 nm are mixed with base fluids such as distilled water and ethylene glycol to form nanofluids. An ultrasonic generator was used to generate uniform particle dispersion in the fluid and keep the mixture stable for a long period of time. The impact of various particle types and their volume concentration on fluid properties such as thermal conductivity and viscosity will be analyzed using a thermal properties analyzer KD2 pro system and Brookfield DV2T viscometer. Because of their small sizes, nanoparticles are not static in fluid and they tend to move around the fluid in random motion, enhancing the mixing and causing the thermal transport performance to increase.
2016-04-05
Technical Paper
2016-01-0193
Shoichi Imahigashi, Masaharu Sakai, Etsuro Yoshino, Yasushi Mitsuishi
In recent years, the spread of eco-car has led to the demand for adaptation to low heat source, high efficiency and low noise in vehicle air conditioner. On the other hand, larger interior space of vehicle to assure passenger comfort is demanded, so that the car air-conditioner is required to be smaller. Therefore, we adopted 2-Layer HVAC for the air conditioner which can respond to a low heat source. At the same time we have developed the compact high-efficiency 2-layer blower fan for HVAC in order to enable the 2-Layer HVAC to be mounted on eco-car with smaller space than conventional HVAC. Generally, because axial flow velocity increases resulting from downsizing of the blower, the ununiform velocity distribution in the axial direction and the turbulent flow between fan blades occurs. It causes the efficiency decrease. To satisfy both downsizing and high-efficiency of the 2-layer blower, we have developed new technologies which can make the flow uniform between fan blades.
2016-04-05
Technical Paper
2016-01-0205
Mattia De Rosa, Roy Douglas, Stephen Glover
The internal combustion (IC) engines exploits only about 30% of the chemical energy ejected through combustion, whereas the remaining part is rejected by means of cooling system and exhausted gas. Nowadays, a major global concern is finding sustainable solutions for better fuel economy which in turn results in a decrease of carbon dioxide (CO2) emissions. The Waste Heat Recovery (WHR) is one of the most promising techniques to increase the overall efficiency of vehicle system, allowing the recovery of the heat rejected by the exhaust and cooling systems. In this context, Organic Rankine Cycles (ORCs) are widely recognized as a potential technology to exploit the heat rejected by engines to produce electricity. The aim of the present paper is to investigate a WHR system, designed to collect both coolant and exhausted gas heats, coupled with an ORC cycle for vehicle applications.
2016-04-05
Technical Paper
2016-01-0209
Youcai Liang
This paper presents performance of a novel ECCS (electricity-cooling cogeneration system) based on cascade utilization of the waste heat of marine engines. The cogeneration system consists of a steam Rankine cycle and an NH3-H2O absorption refrigeration cycle with an expander. The steam Rankine cycle recycles the energy of both jacket coolant and exhaust gas of engine, while the absorption refrigeration cycle is employed to recover energy of the expanded steam at the turbine outlet in Rankine cycle. The performance of the waste heat recovery system is evaluated in terms of electricity, cooling capacity, equivalent electricity and exergy efficiency. The simulation results show that the novel ECCS exhibited a maximum net electricity output of 4561 kW, a maximum cooling capacity of 3197 kW, and a maximum equivalent electricity of 5233 kW.
2016-04-05
Technical Paper
2016-01-0214
Kaushal Kumar Jha, Ravi Ranjan, Parvej Khan, Lakshmaiah Brahmasani
For the thermal management of an automobile, the induced airflow become necessities to enable the sufficient heat transfer with ambient. In this way, the components works within the designed temperature limit. It is the engine-cooling fan that enables the induced airflow. There are two types of engine-cooling fan, one that is driven by engine itself and other as electrically driven. Due to ease in handling, reduced power consumption, improved emission condition, electrically operated fan becoming increasingly popular compared to engine driven fan. The prime mover for electric engine cooling fan is DC motor. Malfunction of DC motor due to overheating will lead to engine over heat, Poor HVAC performance, overheating of other critical components in engine bay. Based upon the real world driving condition, 1D transient thermal model of engine cooling fan motor was developed. This transient model is able to predict the temperature of rotor and casing with and without holes.
2016-04-05
Technical Paper
2016-01-0210
Taku Matsuda, Yuji Kobayashi, Itsuhei Kohri, Hideaki Nagano, ZongGuang Wang, Saneaki Akieda
Recently, the evaluation of the thermal environment in the engine compartment becomes severe than ever because turbocharger has been more employed and installed in it. This paper proposed a new prediction model of momentum source for turbine of turbocharger, which is applicable to three-dimensional thermal fluid analysis of vehicle exhaust systems in the phase of the actual vehicle development. Taking computational cost into account, the fluid force given by the turbine blades is imitated by adding the external source term to Navier-Stokes equations corresponding to the optional domain without computational grids of actual blades. Mass flow rate through the turbine, blade angle and the revolution number of the blade is used as input data and then the source is calculated so as to satisfy law of conservation of angular momentum.
2016-04-05
Technical Paper
2016-01-0219
Song Lan, Zhijia Yang, Richard Stobart, Edward Winward
The figure of merit Z=S^2/kρ is usually used to compare the performance of a thermoelectric device with different thermoelectric materials. The larger the figure of merit is, the higher the efficiency of the thermoelectric system is. However in the case of recycling waste heat, due to its free or cheap thermal input, the efficiency of the thermoelectric generation system is not an overriding consideration. Instead the maximum power output is the first priority. Besides, the influence of operation condition on the maximum power outputs cannot be overlooked. In this study, the relationship among thermoelectric material property, operation condition and maximum power output is investigated based on a numerical TEG model with a plate-fin heat exchanger, which has been validated by engine test data.
2016-04-05
Technical Paper
2016-01-0224
Robin Y. Cash, Edward Lumsdaine, Apoorv Talekar, Bashar AbdulNour
To address the need of increasing fuel economy requirements, automotive Original Equipment Manufacturers (OEMs) are increasing the number of turbocharged engines in their powertrain line-ups. The turbine-driven technology uses a forced induction device, which increases engine performance by increasing the density of the air charge being drawn into the cylinder. Denser air allows more fuel to be introduced into the combustion chamber, thus increasing engine performance. During the compression process, the air is heated to temperatures that can result in pre-ignition resulting in reduced engine functionality. The introduction of the charge air cooler (CAC) is therefore, necessary to extract heat created during the compression process. The present research describes the physics and develops the theoretical equations that define the process.
2016-04-05
Technical Paper
2016-01-0220
Ban Gu, Xiaohong Yuan
With great development of thermoelectric exhaust heat recovery technology, more and more attention has been paid to optimization of automotive thermoelectric generators (ATEGs). A lot of work has been done on optimization of flow field and thermal analysis, however work that focuses on acoustic optimization is not too much. In this paper, efforts have been paid to research acoustic performance of a flat-plate TEG, and to check out the feasibility of integration of automotive exhaust thermoelectric generator with muffler. The internal configuration of heat exchanger looks like “fishbone”. Four factors have been taken into consideration: the spacing of two fins, angle of the fins, the diameter of inlet and outlet of exchanger, and filling sound absorbing material in heat exchanger chamber. Based on these four factors, acoustic analysis was carried out.
2016-04-05
Technical Paper
2016-01-0232
Zhijia Yang, Edward Winward, Song Lan, Richard Stobart
It is well known that there are approximately two-thirds of fuel energy is rejected as thermal energy in internal combustion engine, one third to the coolant and one third to the exhaust. Thermo-Electric Generator (TEG) is a static solid-state thermal to electricity energy convertor. It is very attractive in the application of engine waste thermal energy harvest because it has no moving parts. Otherwise, it is simple, silent, reliable and scalable. Even though the current commercial thermoelectric material only has 5% thermal efficiency, the research works on new Thermo-Electric Module (TEM) show that thermal efficiency of TEM may possible reach 20% by using quantum well technology and even more may reach maximum 50% by using isolation technology within a TEM. This prediction increases the possibility for TEG becomes one of the important optimization elements in future hybrid vehicle. A one dimensional TEG dynamic model was developed and validated using TEG on engine test data.
2016-04-05
Technical Paper
2016-01-0231
Song Lan, Zhijia Yang, Richard Stobart, Edward Winward
An automotive engine can be more efficient if thermoelectric generators (TEG) are used to convert the heat of exhaust gas into electricity. The exhaust gas flow rate plays important role in this energy transfer process. In this study, the impact of exhaust gas flow rate on the performance of the thermoelectric generator is investigated based on a numerical TEG model with a plate-fin heat exchanger, which has been validated by engine test data. The model is utilized to analyze the influence of exhaust gas flow rate on TEG performance in terms of its maximum power output. Both the engine test data and the TEG model indicates that when the exhaust gas flow rate increases, the temperature drop across the TEG along the flow direction decreases while the pressure drop increases. The TEG model reveals that the impact of the exhaust flow rate on the TEG performance is via the impact of the exhaust gas flow rate on the fin thermal resistance of the heat exchanger.
2016-04-05
Technical Paper
2016-01-0247
Jiu Xu, Predrag Hrnjak
Understanding the flow at compressor discharge is essential for rational design of oil separators and other components. This paper presents visualization, experimental and analytical data of the flow at the discharge of an automotive air conditioning compressor. The flow regime is annular-mist consisting of gas-phase refrigerant flow and oil rich liquid in form of annular film and droplets. The paper reports a method to calculate the oil retention and oil circulation ratio based on oil film thickness, wave speed, oil droplet size, oil droplet speed, and mass flow rate. Oil flow parameters are measured by high-speed camera capture and video processing in a non-intrusive way. The estimated oil retention and oil circulation ratio results are compared quantitatively with the measurements from system experiments under different compressor outlet gas velocity.
2016-04-05
Technical Paper
2016-01-0245
Jingwei Zhu, Stefan Elbel
Increasing energy costs justify research on how to improve utilization of low-grade energy that is abundantly available as waste heat from many thermodynamic processes such as internal combustion engine cycles. One option is to directly generate cooling through absorption/adsorption or vapor jet ejector cycles. As in the case of power generation cycles, cooling cycle efficiencies would increase if the heat input were available at higher temperature. This paper assesses the feasibility of a novel idea that uses a vortex tube to increase the available temperature levels of low-grade heat sources. The desired temperature increase is achieved by sending a stream of vapor that was heated by the waste heat source through a vortex tube, which further elevates the temperature used in a heat driven ejector cooling cycle.
2016-04-05
Technical Paper
2016-01-0256
Hideaki Nagano, Kenji Tomita, Yasuhiro Tanoue, Yuji Kobayashi, Itsuhei Kohri, Shinsuke Kato
For winter season, outdoor air needs to be intaked by HVAC system to prevent the front window from fogging, however, the energy of ventilation loss could not be neglected. In the present study, CFD simulation has been done with the simplified cabin model in order to evaluate the defogging pattern based on the condition of air supplying. The results indicated the mixing ratio of outdoor air and recirculation air had dominant impact on the defogging pattern and also the HVAC load. Additionally, the location of exhaust opening, from which the recirculation air was intaked, had affected on the fluid field in the cabin and then the defogging pattern. It means not only the property of the defroster itself but also the other design such as the exhaust location need to be considered to achieve the effective defogging.
2016-04-05
Technical Paper
2016-01-0253
Jun Li, Pega Hrnjak
This paper presents the experimental analysis of separation in vertical headers based on flow visualization. Two-phase separation phenomena inside the header is observed and quantified. Driving forces are analyzed to study the mechanisms for two-phase flow motion and flow regimes. Main tube of the header is made of clear PVC for visualization study. R-134a is used as the fluid of interest and the mass flux from the inlet pass is 55 kg/m2s – 195 kg/m2s. Potential ways to improve two-phase separation are discussed. A model is built to show how separation brings potential benefits to MAC heat exchangers by arranging the flow path.
2016-04-05
Technical Paper
2016-01-1683
Blago B. Minovski, Lennart Lofdahl, Peter Gullberg
Presented are results from numerical investigations of buoyancy-driven flow in a simplified engine bay representation. This analysis is based on previously performed PIV and temperature measurements of the phenomenon in a controlled physical setup, which reproduced thermal soak conditions in the engine compartment of a vehicle parked in a quiescent ambient after sustaining high thermal loads. Thermal soak is an important phenomenon in the engine bay primarily driven by natural convection and radiation after there had been a high power demand on the engine. With the cooling fan turned off and in quiescent environment, buoyancy driven convection and radiation are the dominating modes of heat transfer. The unsteady and turbulent nature of this complex phenomenon requires high spatial and temporal resolutions and an effective computational strategy. A best practice CFD approach for modeling buoyancy-driven flow in vehicle underhood is developed and demonstrated.
2016-04-05
Technical Paper
2016-01-0892
Oliver P. Taylor, Richard Pearson, Richard Stone
Most major regional automotive markets have stringent legislative targets for vehicle greenhouse gas emissions or fuel economy enforced by fiscal penalties. Large improvements in vehicle efficiency on mandated test cycles have already taken place in some markets through the widespread adoption of technologies such as downsizing or dieselization. Whilst alternative combustion concepts that promise step-out efficiency improvements continue to be of interest, there is now increased focus on approaches that give smaller, but significant incremental benefits, such as reducing parasitic losses due to engine friction. The reduction in tail pipe CO2 emission through the reduction of engine friction using lubricant formulation-controlled viscometric profiles has been reported by many authors. There also exist opportunities to reduce the lubricant viscosity during engine warm-up by thermal management of the lubricating oil as it performs its role in protecting the engine.
2016-04-05
Journal Article
2016-01-0183
Taehoon Han, Hyunki Sul, John Hoard, Chih-Kuang Kuan, Daniel Styles
Exhaust Gas Recirculation (EGR) coolers are regularly used in diesel engines to reduce the re-circulated gas temperature. A common problem with the EGR cooler is a reduction of the effectiveness due to the inner fouling layer of the tubes caused by thermophoresis, diffusion, hydrocarbon condensation and so on. The effectiveness decreases rapidly at first, and usually asymptotically stabilizes over time. There are various hypotheses of this stabilizing phenomenon; one of the possible theories is a deposit removal mechanism. Verifying such a mechanism and finding out the correlation between this removal mechanism and stabilization tendency would be a key factor to understand the problem. Some authors have proposed that the removal due to blowing velocity, or temperature of the deposit surface are possible influential factors, while other authors suggest removal is not a significant factor.
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