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2015-04-14
Technical Paper
2015-01-0348
Chuqi Su, Meng Xu, Naiqiang Tong, Yulian Chen
Abstract The potential for automotive exhaust-based thermoelectric generator (TEG) has been increasing with continuously advances in thermoelectric technology. In this paper, the thermal deformation of the TEG system is studied on the basis of the surface temperature distribution of the heat exchanger. The simulation result shows that thermoelectric modules (TMs) on different positions have different thermal performance which can significantly influence the power generation efficiency of the system. Meanwhile, in terms of the working performance of TMs, the clamping mechanism is considered to have some effects on both the cold side and the hot side of TEG. Following the simulation, bench tests are carried out to confirm the reasonability of the simulation results.
2015-04-14
Technical Paper
2015-01-0347
Logesh Shankar Somasundaram, S Sriraman, Rakesh Verma
The paper aims at numerically modeling the flow and thermal processes occurring in an agricultural tractor using Computational Fluid Dynamics (CFD) and determines the comfort level of the tractor operator during working condition. The motive of the investigation is to develop and demonstrate capabilities of CFD as an automotive analysis tool. The work describes a methodology that significantly stream lines the process of thermal flow taking place in a tractor by utilizing state-of-the art computer simulation of air flow and heat transfer. The numerical investigation carried out with a three-dimensional geometry of the vehicle assembly and the measurements were taken from the vehicle. The geometry created with Pro/Engineer formed the domain for the automatically generating discretized grid contained the majority of the main components within the underhood environment.
2015-04-14
Technical Paper
2015-01-0346
Lei Dongxu, Minli Bai, Jizu Lv, Peng Wang, Chengzhi Hu, Yuyan Wang
Abstract Due to the latent heat of vaporization, the efficiency of boiling heat transfer is several times and even dozens of times higher than that of the convection heat transfer. With the improvement of power density of the engine, there are more requirements for engine cooling system design. It has been confirmed that the subcooled boiling did exist in the engine cooling. If boiling heat transfer can be reasonablely used, we can achieve the objective of enhancing heat transfer without changing the existing structure. In this paper, in order to quantitatively research the subcooled boiling in the engine, we simulated the subcooled boiling in the analog channel with the Euler multiphase model, found the importance of the turbulent dispersion. In additon, we explored the applicability of existing models to subcooled boiling, and compared the results with the experiment.
2015-04-14
Technical Paper
2015-01-0351
Jason A. Lustbader, Cory Kreutzer, Steven Adelman, Skip Yeakel, John Zehme
Abstract Annual fuel use for long-haul truck rest period idling is estimated at 667 million gallons in the United States. The U.S. Department of Energy's National Renewable Energy Laboratory's CoolCab project aims to reduce heating, ventilating, and air conditioning (HVAC) loads and resulting fuel use from rest period idling by working closely with industry to design efficient long-haul truck climate control systems while maintaining occupant comfort. Enhancing the thermal performance of cab/sleepers will enable smaller, lighter, and more cost-effective idle reduction solutions. In order for candidate idle reduction technologies to be implemented at the original equipment manufacturer and fleet level, their effectiveness must be quantified. To address this need, a number of promising candidate technologies were evaluated through experimentation and modeling to determine their effectiveness in reducing rest period HVAC loads.
2015-04-14
Technical Paper
2015-01-0350
Zhi Li, Gangfeng Tan, Jing Cai, Zhongjie Yang, YiRui Wang, Haobo Xu
Abstract The vehicle engine exhaust wastes heat. For the conventional scheme, the hot-end of the thermoelectric module is connected with the exhaust pipe, while the cold-end is cooled through the vehicle engine cooling cycle. The variation of vehicle engine operating conditions brings the instability of the hot-end temperature, which affects the power generation performance of thermoelectric materials and increases the damage risk to the thermoelectric materials caused by the high temperature. This research adopts the heat transfer oil circulation as the intermediate fluid to absorb the dynamic heat flux of the vehicle engine exhaust so as to release the heat steadily to the hot-end of the thermoelectric module. The thermal characteristics of the target diesel vehicle engine exhaust gas are evaluated based on the experimental data firstly.
2015-04-14
Technical Paper
2015-01-0355
Matthew A. Jeffers, Larry Chaney, John P. Rugh
Abstract Passenger compartment climate control is one of the largest auxiliary loads on a vehicle. Like conventional vehicles, electric vehicles (EVs) require climate control to maintain occupant comfort and safety, but cabin heating and air conditioning have a negative impact on driving range for all-electric vehicles. Range reduction caused by climate control and other factors is a barrier to widespread adoption of EVs. Reducing the thermal loads on the climate control system will extend driving range, thereby reducing consumer range anxiety and increasing the market penetration of EVs. Researchers at the National Renewable Energy Laboratory have investigated strategies for vehicle climate control load reduction, with special attention toward EVs. Outdoor vehicle thermal testing was conducted on two 2012 Ford Focus Electric vehicles to evaluate thermal management strategies for warm weather, including solar load reduction and cabin pre-ventilation.
2015-04-14
Technical Paper
2015-01-0327
Elizabeth M. Patterson, Iman Goldasteh, Salamah Maaita
Abstract Recent progress in computer-aided engineering (CAE) has made it possible to model complex interdisciplinary multiphysics analyses. This paper investigated the sequential coupled thermal-structural analysis by examining the associated thermal stresses under simulated operational conditions close to the real situation. An evaluation of exhaust muffler strain due to thermal stresses was made by coupling Star-CCM+ CFD software and ABAQUS FEM structural analysis software. The study was made to evaluate discovered muffler durability test failure and to develop a countermeasure design. Failure of the muffler internal pipe was discovered after heat cycle durability testing. The internal pipe had broken into two pieces. In the first step, CFD analysis was done by thermo-flow simulation to determine the resulting heat distribution on the muffler assembly when subjected to the prescribed peak duty cycle temperature.
2015-04-14
Technical Paper
2015-01-0328
Wilko Jansen, Joe Amodeo, Sam Wakelam, Kamalesh Bhambare
Abstract The level of infotainment in today's vehicles and the customer expectation of the functionality imply a significant effort is required on thermal management of the systems, to guarantee their full operation under all operating conditions. The worst case thermal conditions the system will get exposed to are caused by solar loading on the cabin or heat up as a result of cabin heating. Simulation of a solar load driven case will be discussed in this paper. The long soak conditions during these tests result in the modelling requirement for long natural convection periods. This is creating a challenge for the conventional CFD simulations in turnaround time. New simulation methodology has resulted in significant speed up enabling these fully transient simulations in a reasonable turnaround time to enable programme support. A two phase approach to simulating this problem is proposed in this paper.
2015-04-14
Journal Article
2015-01-0326
Takuya Yamaguchi, Yuzo Aoyagi, Noboru Uchida, Akira Fukunaga, Masayuki Kobayashi, Takayuki Adachi, Munemasa Hashimoto
Abstract In heavy duty diesel engines, the waste heat recovery has attracted much attention as one of the technologies to improve fuel economy further. In this study, the available energy of the waste heat from a high boosted 6-cylinder heavy duty diesel engine which is equipped with a high pressure loop EGR system (HPL-EGR system) and low pressure loop EGR system (LPL-EGR system) was evaluated based on the second law of thermodynamics. The maximum potential of the waste heat recovery for improvement in brake thermal efficiency and the effect of the Rankine combined cycle on fuel economy were estimated for each single-stage turbocharging system (single-stage system) and 2-stage turbocharging system (2-stage system).
2015-04-14
Technical Paper
2015-01-0331
Sina Shojaei, Simon Robinson, Chris Chatham, Andrew McGordon, James Marco
Abstract Among the auxiliary systems on electric and hybrid electric vehicles the electric air conditioning (eAC) system causes the largest load on the high voltage battery and can significantly impact the energy efficiency and performance of the vehicle. New methods are being investigated for effective management of air conditioning loads through their integration into vehicle level energy management strategies. For this purpose, a fully integrated vehicle model is developed for a commercially available hybrid vehicle and used to develop energy management algorithms. In this paper, details of the eAC model of this vehicle are discussed, including steady state component validation against rig data. Also results of simulating the cabin pull-down are included.
2015-04-14
Technical Paper
2015-01-0335
Sandeep Makam, Christopher Dubbs, Yeliana Roosien, Feng Lin, William Resh
Abstract Due to ever-tightening CO2 regulations on passenger vehicles, it is necessary to find novel methods to improve powertrain system efficiency. These increases in efficiency should generally be cost effective so that the customer perceives that they add value. One approach for improving system efficiency has been the use of thermal energy management. For example, changing the flow of, or reusing “waste” heat from the powertrain to improve efficiency. Due to the interactions involved with thermal management, a system level approach is useful for exploring, selecting, and developing alternative solutions. It provides a structured approach to augment the right kind of synergies between subsystems and mitigate unintended consequences. However, one challenge with using these approaches early in a program is having appropriate metrics for assessing key aspects of the system behaviors.
2015-04-14
Technical Paper
2015-01-0329
Mark Hepokoski, Allen Curran, Richard Burke, John Rugh, Larry Chaney, Clay Maranville
Abstract Reliable assessment of occupant thermal comfort can be difficult to obtain within automotive environments, especially under transient and asymmetric heating and cooling scenarios. Evaluation of HVAC system performance in terms of comfort commonly requires human subject testing, which may involve multiple repetitions, as well as multiple test subjects. Instrumentation (typically comprised of an array of temperature sensors) is usually only sparsely applied across the human body, significantly reducing the spatial resolution of available test data. Further, since comfort is highly subjective in nature, a single test protocol can yield a wide variation in results which can only be overcome by increasing the number of test replications and subjects. In light of these difficulties, various types of manikins are finding use in automotive testing scenarios.
2015-04-14
Technical Paper
2015-01-0330
Iman Goldasteh, Shi-Ing Chang, Salamah Maaita, Gursaran Mathur
Abstract Proper flow distribution on the windshield and side windows is critical for adequate visibility while driving. Fog or ice which forms on the windshield is the main reason of invisibility and leads to major safety issue. It has been shown that proper clear visibility for the windshield could be obtained with a better flow pattern and uniform flow distribution in the defrost mode of the automobile heating, ventilation, and air-conditioning (HVAC) system. In this study, a three dimensional numerical model of a car cabin with full HVAC system was developed using Star-CCM+, a commercial CFD package. The Reynolds-Averaged Navier-Stokes equations (RANS) approach with the realizable two-layer k-ε turbulence model was employed for simulating the airflow field on the windshield for the defrost mode. The HVAC unit, ducts and defroster grille were included in the analysis in detail and the air distribution on the windshield was studied.
2015-04-14
Journal Article
2015-01-0339
Aimon Allouache, Smith Leggett, Matthew J. Hall, Ming Tu, Chad Baker, Haiyan Fateh
Abstract The performance of an organic Rankine cycle (ORC) that recovers heat from the exhaust of a heavy-duty diesel engine was simulated. The work was an extension of a prior study that simulated the performance of an experimental ORC system developed and tested at Oak Ridge National laboratory (ORNL). The experimental data were used to set model parameters and validate the results of that simulation. For the current study the model was adapted to consider a 15 liter turbocharged engine versus the original 1.9 liter light-duty automotive turbodiesel studied by ORNL. Exhaust flow rate and temperature data for the heavy-duty engine were obtained from Southwest Research Institute (SwRI) for a range of steady-state engine speeds and loads without EGR. Because of the considerably higher exhaust gas flow rates of the heavy-duty engine, relative to the engine tested by ORNL, a different heat exchanger type was considered in order to keep exhaust pressure drop within practical bounds.
2015-04-14
Technical Paper
2015-01-0340
Jan Eller, Thomas Binner, Heinrich Reister, Nils Widdecke, Jochen Wiedemann
Abstract Collective life-cycle data is needed when developing components like elastomer suspension mounts. Life-time prediction is only possible using thermal load frequency distributions. In addition to current extreme load cases, the Idle Load Case is examined at Mercedes-Benz Car Group as a collective load case for Vehicle Thermal Management (VTM) numerical simulations in early development stages. It combines validation opportunities for HVAC, cooling and transmission requirements in hot-country-type ambient conditions. Experiments in climatic wind tunnels and coupled 3D CFD and heat transfer simulations of the Idle Load Case have been performed. Measurements show steady conditions at the end of the load case. Decoupling of the torque converter, changes in ambient temperature and the technical implementation of a wind barrier for still air conditions exhibit influence on component-level results. Solar load, however, does not significantly change the examined component temperatures.
2015-04-14
Technical Paper
2015-01-0336
Amey Karnik, Daniel Pachner, Adrian M. Fuxman, David Germann, Mrdjan Jankovic, Christopher House
Abstract Numerous studies describe the fuel consumption benefits of changing the powertrain temperature based on vehicle operating conditions. Actuators such as electric water pumps and active thermostats now provide more flexibility to change powertrain operating temperature than traditional mechanical-only systems did. Various control strategies have been proposed for powertrain temperature set-point regulation. A characteristic of powertrain thermal management systems is that the operating conditions (speed, load etc) change continuously to meet the driver demand and in most cases, the optimal conditions lie on the edge of the constraint envelope. Control strategies for set-point regulation which rely purely on feedback for disturbance rejection, without knowledge of future disturbances, might not provide the full fuel consumption benefits due to the slow thermal inertia of the system.
2015-04-14
Technical Paper
2015-01-0358
Praveen Balaj Balakrishnan, Xiaoyong Yu, Ka Chung Chan, Chi Yan Tso, Christopher Chao
Abstract An adsorption air conditioning system is proposed to provide cabin comfort cooling for automotives. This report focuses on the development of a compact adsorption cooling system for automobile applications and its experimental performance. This system uses AQSOA - Z01, an adsorbent material that adsorbs and regenerates water efficiently at low temperature ranges. A water circulation system was built to simulate the process of obtaining heat from exhaust gas heat and providing low-grade thermal energy for the adsorption cooling system. As this system does not need to be powered by the engine as it is in the conventional system, fuel efficiency of the engine can be improved by 10%. This also results in reduction of pollutants due to combustion. The prototype is produced a maximum1310 Watts of cooling power. The system also achieved 650 W/kg SPC (Specific Cooling Power) and a COP (Coefficient of Performance) value of 0.45.
2015-04-14
Journal Article
2015-01-0359
Satoki Uematsu, Toshiyuki Uehara, Toshiya Uchida, Gursaran D. Mathur
Abstract In last 10 years or so, a number of OEMs are designing vehicles with start-stop function to save energy and to reduce pollution. For these systems, the situations in which air-conditioning systems are used have been changing with a significant increase in adoption of idle-time reduction systems (no idling-system). Blower fan remains operating at idle condition while compressor stops in most cases for these systems. In this case, the air temperature at the vent outlets increases. The increase in the air temperature under range of thermal boundary conditions around the evaporator causes a concern of odor to occur. This paper describes and explains experimental studies on changes in heat and humidity at the air outlets according to the switching operation of compressor and root cause analyses of odor coming from air-conditioning system for vehicles with start-stop function.
2015-04-14
Technical Paper
2015-01-0360
Maryline Leriche, Wolfgang Roessner, Heinrich Reister, Bernhard Weigand
Abstract An accurate model to predict the formation of fogging and defogging which occurs for low windshield temperatures is helpful for designing the air-conditioning system in a car. Using a multiphase flow approach and additional user-defined functions within the commercial CFD-software STAR-CCM+, a model which is able to calculate the amount of water droplets on the windshield from condensation and which causes the fogging is set up. Different parameters like relative humidity, air temperature, mass flow rate and droplet distributions are considered. Because of the condition of the windshield's surface, the condensation occurs as tiny droplets with different sizes. The distribution of these very small droplets must be obtained to estimate numerically the heat transfer coefficient during the condensation process to predict the defogging time.
2015-04-14
Technical Paper
2015-01-0362
Neal Lawrence, Stefan Elbel
Abstract Much attention has been given in recent years to the use of two-phase ejectors and particularly to the performance of the standard ejector cycle with a liquid-vapor separator. However, this cycle may not be the best choice for automotive applications due to the large size required by an efficient separator as well as the cycle's performance at conditions of lower ejector potential. A limited amount of recent research has focused on alternate two-phase ejector cycles that may be better suited for automotive applications. One of these cycles, using the ejector to allow for evaporation at two different temperatures and eliminating the need for a separator, will be the subject of investigation in this paper. Previous investigations of this cycle have been mainly theoretical or experimental; this paper aims to provide a numerical analysis of the effect of evaporator design on the performance of the ejector cycles.
2015-04-14
Technical Paper
2015-01-0363
Vasanth Balashunmuganathan, Ramakrishna Nukala, Sathishkumar Sampath Kumar, Murali Govindarajalu
In recent years clearing the mist on side windows is one of the main criterions for all OEMs for providing comfort level to the person while driving. Visibility through the side windows will be poor when the mist is not cleared to the desired level. “Windows fog up excessively/don't clear quickly” is one of the JD Power question to assess the customer satisfaction related to HVAC performance. In a Mobile Air Conditioning System, HVAC demister duct and outlet plays an important role for removing the mist formation on vehicle side window. Normally demister duct and outlet design is evaluated by the target airflow and velocity achieved at driver and passenger side window. The methodology for optimizing the demister outlet located at side door trim has been discussed. Detailed studies are carried out for creating a parametric modeling and optimization of demister outlet design for meeting the target velocity.
2015-04-14
Technical Paper
2015-01-0364
Yinhua Zheng
This paper presents the way to optimize vehicle AC system TXV to meet the various AC system requirements. It discusses vehicle AC system TXV sizing and selection process. In today's automotive industry, sizing and selecting the TXV is more complicated than before as various new components are introduced such as external control compressor, internal control compressors and internal heat exchanger etc. These components complicated the system interaction among the components. Thus it requires mapping TXV characteristic to meet the system demand. Sizing TXV capacity, it must start with the vehicle heat load requirement. The type of TXV (i.e. cross charge or parallel charge head) is determined by the system configuration such as compressor, evaporator, and condenser type and with or without internal heat exchanger, etc. To optimize TXV in the system involves in evaluating TXV characteristic and cooling capacity in the various AC operating conditions.
2015-04-14
Technical Paper
2015-01-0365
Gursaran D. Mathur
Abstract Experimental studies have been conducted to determine the energy stored in vehicle's Cockpit Module (CPM) at cold soaking conditions for a MY2012 production vehicle. Detailed analysis has been done in this paper to show the influence of energy stored in various components (e.g., Instrument panel, HVAC system, heat exchanger, wire harness, etc.) contained within the CPM unit. Experiments conducted show that the instrument panel stores the maximum amount of energy at a given temperature.
2015-04-14
Technical Paper
2015-01-0366
Cristian Rostiti, Stephanie Stockar, Marcello Canova
Abstract In a conventional passenger vehicle, the AC system is the largest ancillary load. This paper proposes a novel control strategy to reduce the energy consumption of the air conditioning system of a conventional passenger car. The problem of reducing the parasitic load of the AC system is first approached as a multi-objective optimization problem. Starting from a validated control-oriented model of an automotive AC system, an optimization problem is formalized to achieve the best possible fuel economy over a regulatory driving cycle, while guaranteeing the passenger comfort in terms of cabin temperature and reduce the wear of the components. To complete the formulation of the problem, a set of constraints on the pressure in the heat exchanger are defined to guarantee the safe operation of the system. The Dynamic Programming (DP), a numerical optimization technique, is then used to obtain the optimal solution in form of a control sequence over a prescribed driving cycle.
2015-04-14
Technical Paper
2015-01-0368
Janampally Sandeep Kumar Reddy, Shailendra Deopa, Abhay Sharma, Piyush Aggarwal
Abstract Bumper opening area projected on condenser to total condenser core area is referred to as condenser opening area. The condenser opening area plays a vital role in A/C Performance of vehicle particularly during idling and initial cooling of vehicle. This paper presents detail study on effects of condenser opening area on A/C performance. Based on theory, the effect of condenser opening area is studied and it is validated by experimental results. Depending on these results an optimum value of condenser opening area required for best A/C performance is concluded.
2015-04-14
Technical Paper
2015-01-0369
Rupesh Sonu Kakade
Abstract In addition to the thermal comfort of the vehicle occupants, their safety by ensuring adequate visibility is an objective of the automotive climate control system. An integrated dew point and glass temperature sensor is widely used among several other technologies to detect risk of fog formation on the cabin side (or inner) surface of the windshield. The erroneous information from a sensor such as the measurement lag can cause imperfect visibility due to the delayed response of the climate control system. Also the high value, low cost vehicles may not have this sensor due to its high cost. A differential equation based model of the cabin air humidity is proposed to calculate in real-time specific humidity of the passenger compartment air. The specific humidity is used along with the windshield surface temperature to determine relative humidity of air and therefore, the risk of fog formation on the interior surface of a windshield.
2015-04-14
Technical Paper
2015-01-0370
Modar Horani, Osamah Rawashdeh
Abstract Traditional Heat Ventilation and Air Conditioning (HVAC) control systems are reactive by design and largely dependent on the on-board sensory data available on a Controller Area Network (CAN) bus. The increasingly common Internet connectivity offered in today's vehicles, through infotainment and telematic systems, makes data available that may be used to improve current HVAC systems. This includes real-time outside relative humidity, ambient temperature, precipitation (i.e., rain, snow, etc.), and weather forecasts. This data, combined with position and route information of the vehicle, may be used to provide a more comfortable experience to vehicle occupants in addition to improving driver visibility through more intelligent humidity, and defrost control. While the possibility of improving HVAC control utilizing internet connectivity seems obvious, it is still currently unclear as to what extent.
2015-04-14
Journal Article
2015-01-0371
Rupesh Sonu Kakade, Prashant Mer
Abstract The human thermal comfort, which has been a subject of extensive research, is a principal objective of the automotive climate control system. Applying the results of research studies to the practical problems require quantitative information of the thermal environment in the passenger compartment of a vehicle. The exposure to solar radiation is known to alter the thermal environment in the passenger compartment. A photovoltaic-cell based sensor is commonly used in the automotive climate control system to measure the solar radiation exposure of the passenger compartment of a vehicle. The erroneous information from a sensor however can cause thermal discomfort to the occupants. The erroneous measurement can be due to physical or environmental parameters. Shading of a solar sensor due to the opaque vehicle body elements is one such environmental parameter that is known to give incorrect measurement.
2015-04-14
Technical Paper
2015-01-0372
Rupesh Sonu Kakade
Abstract The vehicle air-conditioning system has significant impact on fuel economy and range of electric vehicles. Improving the fuel economy of vehicles therefore demand for energy efficient climate control systems. Also the emissions regulations motivate the reduced use of fuel for vehicle's cabin climate control. Solar heat gain of the passenger compartment by greenhouse effect is generally treated as the peak thermal load of the climate control system. Although the use of advanced glazing is considered first to reduce solar heat gain other means such as ventilation of parked car and recirculation of cabin air also have impetus for reducing the climate control loads.
2015-04-14
Technical Paper
2015-01-0399
Alexander Jaust, Bastian Morcinkowski, Stefan Pischinger, Jens Ewald
Abstract In this work, a transport and mixing model that calculates mixing in thermodynamic phase space was derived and validated. The mixing in thermodynamic multizone space is consistent to the one in the spatially resolved physical space. The model is developed using a turbulent channel flow as simplified domain. This physical domain of a direct numerical simulation (DNS) is divided into zones based on the quantitative value of transported scalars. Fluxes between the zones are introduced to describe mixing from the transport equation of the probability density function based on the mixing process in physical space. The mixing process of further scalars can then be carried out with these fluxes instead of solving additional transport equations. The relationship between the exchange flux in phase space and the concept of scalar dissipation are shown and validated by comparison to DNS results.
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