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Viewing 1 to 30 of 4161
2011-04-12
Journal Article
2011-01-0129
MIng Huo, Chia-Fon Lee
In this paper, experimental investigation on spray atomization and droplet dynamics inside a thermostatic expansion valve (TXV), a component commonly used in vehicle refrigeration system, was conducted. A needle and an orifice were copied from a commercial TXV and machined to be mounted inside a chamber with optical access so that the flow inside the TXV is simulated and visualized at the same time. The break-up and atomization of the refrigerant were documented near the downstream of the orifice under different feed conditions for two TXV with different geometry. A Phase Doppler Anemometry (PDA) system was used later to measure the size and velocity of atomized refrigerant droplets. The results showed that the droplet size variation along the radial direction is slightly decreased at near downstream and increased at farther downstream due to the coalescence.
2011-04-12
Technical Paper
2011-01-0133
Gursaran D. Mathur
An experimental investigation has been carried out to quantify the performance enhancements with a suction line heat exchanger (SLHX) in an AC system with HFO-1234yf as the working fluid. An off-the-shelf double pipe cross fluted SLHX is used for this investigation. System level bench tests are conducted with an AC system from a 2009 MY mid-sized sedan. The test results shows that the AC system performance with HFO-1234yf can be improve up to 8~9% in comparison to a baseline system without a SLHX.
2011-04-12
Technical Paper
2011-01-0135
Daniela Magnetto, Robert de Boer, Abdelmajid Taklanti
This paper describes the development of a Mobile Air Conditioning (MAC) system with a very small impact on the environment. The system based on adsorption cooling is powered by the waste heat recovered from the engine coolant. The advantages of such a system are: a drastic reduction of the fuel overconsumption and the CO2 emission associated to the MAC usage, and the use of water as the refrigerant, which is a no Global Warming Potential (GWP) fluid [1] compliant with the new EU regulation and naturally available. In addition the system being based on thermal compression and not on mechanical compression, is decoupled from the engine operation and has no impact on the vehicle handling. Finally, coupled with a small fuel burner or with a solar panel it can provide air conditioning when the vehicle engine is stop. Thus the system can provide the cabin preconditioning and allows the cabin cooling for those vehicles which are also used for rest or sleeping (truck, camper).
2011-04-12
Journal Article
2011-01-0139
Hanfei Tuo, Algirdas Bielskus, Pega Hrnjak
This paper demonstrates that the implementation of Flash Gas Bypass method can improve the performance of conventional direct expansion R134a mobile air-conditioning system with a microchannel evaporator. This method uses flash gas tank after expansion valve to separate and bypass flash refrigerant vapor around the evaporator, and feed the evaporator with only liquid refrigerant. Pressure drop is reduced and refrigerant distribution is significantly improved, resulting in higher evaporator effectiveness and evaporation pressure. Both lower pressure drop and lifted evaporation pressure allows the compressor to work with lower pressure ratio, saving required compressor work. An experimental comparison of the direct expansion system shows that Flash Gas Bypass method increases the cooling capacity and COP at the same time by up to 16% and 11%, respectively.
2011-04-12
Journal Article
2011-01-0128
Lothar Seybold, William Hill, Jean-Jacques Robin
This paper will examine a mobile air conditioning (MAC) system optimized for efficiency as well as evaporator cooling capacity. Different internal heat exchanger (IHX) capacities and various thermostatic expansion valve (TXV) parameters will be applied using R1234yf refrigerant. Factors that will be considered include IHX heat transfer and pressure drop, TXV superheat setting and slope, the effect of oil in circulation and how these factors impact the efficiency and capacity of the MAC system. The paper describes the test facility used and the test procedures applied.
2011-04-12
Technical Paper
2011-01-0126
Steven Gasworth, Triloka Tankala
Heat transfer between the ambient and the air in a vehicle cabin determines the nominal steady state load on the vehicle's heating, ventilation and air conditioning (HVAC) system, a significant factor for vehicle efficiency and greenhouse gas emissions. This paper highlights the effect of glazing (i.e. window) thermal conductivity on steady state heat transfer, with high and low thermal conductivities represented respectively by monolithic glass and standard polycarbonate. Computational fluid dynamics simulations are summarized for a model car cabin including HVAC vents, interior seating, and a rooflite. Passenger and moisture effects are not included. Monthly temperature and radiation data for Phoenix, Arizona and Minneapolis, Minnesota are used to define hot and cold climate scenarios.
2011-04-12
Journal Article
2011-01-0649
Bin Li, Steffen Peuker, Pega Hrnjak, Andrew Alleyne
Automotive air conditioning systems are subject to constantly changing operation conditions and steady state simulations are not sufficient to describe the actual performance. The refrigerant mass migration during transient events such as clutch-cycling or start-up has a direct impact on the transient performance. It is therefore necessary to develop simulation tools which can accurately predict the migration of the refrigerant mass. To this end a dynamic model of an automotive air conditioning system is presented in this paper using a switched modeling framework. Model validation against experimental results demonstrates that the developed modeling approach is able to describe the transient behaviors of the system, and also predict the refrigerant mass migration among system components during compressor shut-down and start-up (stop-start) cycling operations.
2011-04-12
Journal Article
2011-01-0505
Jun Chen, Zhengqi Gu, Yiping Wang
Numerical simulations are performed to investigate noise generated by flow in automotive HVAC ducts. A hybrid computational method for analyzing flow noise is applied: Large Eddy Simulation (LES) for predicting flow fields and Multi-domain boundary element method for predicting acoustic propagation. LES gives time-resolved solutions of flow velocity and pressure fields. By applying the acoustic analogy theory, the unsteady flow parameters are translated into sound source in evaluating the acoustic propagation. The computational result shows the noise caused by the HVAC ducts is strong. The noise is of broadband with a peak value at 370Hz. A major contribution of the noise generation is from the center ducts. Two design modifications of the center ducts are explored to regulate the flow structures with the ducts for reducing noise generation. Test results demonstrate the effectiveness of the modifications.
2011-04-12
Technical Paper
2011-01-0493
Dongkon Lee, Franck Perot, Kang-Duck Ih, David Freed
Nowadays vehicle quality is rated for noise and vibration and the interior sound levels have become a major target of automotive companies. Strides have been made in reducing power train, tire and external wind noise over the years. However, HVAC and blower fan flow-induced noise reaches the interior cabin without any sound isolation and can strongly impact customer comfort. In the early stage of vehicle design, it is experimentally difficult to get an estimate of the flow pattern and sound levels. The goal of this study is to develop and validate a numerical noise prediction tool for complete HVAC systems noise, defined as the arrangement of sub-systems such as air intake duct, thermal mixing unit, blower, ducts and outlet vents. This tool can then be used during the development of vehicles to evaluate and optimize the aeroacoustics performances of the system without additional or belated experiments.
2010-04-12
Technical Paper
2010-01-0799
John P. Rugh
The air-conditioning (A/C) compressor load significantly impacts the fuel economy of conventional vehicles and the fuel use/range of plug-in hybrid electric vehicles (PHEV). A National Renewable Energy Laboratory (NREL) vehicle performance analysis shows the operation of the air conditioner reduces the charge depletion range of a 40-mile range PHEV from 18% to 30% in a worst case hot environment. Designing for air conditioning electrical loads impacts PHEV and electric vehicle (EV) energy storage system size and cost. While automobile manufacturers have climate control procedures to assess A/C performance, and the U.S. EPA has the SCO3 drive cycle to measure indirect A/C emissions, there is no automotive industry consensus on a vehicle level A/C fuel use test procedure. With increasing attention on A/C fuel use due to increased regulatory activities and the development of PHEVs and EVs, a test procedure is needed to accurately assess the impact of climate control loads.
2013-04-08
Journal Article
2013-01-1337
Naohisa Niimi, Takahiko Yoshida, Toshiki Isogai
Humidity sensors used in automatic windshield defogging controls contribute to the improvement of fuel consumption. The optimum control of air conditioning systems can be realized by adding humidity information to conventional systems which have used only temperature information. While resistive humidity sensors have been widely used, their sensing range and responsiveness are observed as issues. Resistive sensors cannot function at a humidity range of around 100% RH as well as at a low temperature range, and have a low response rate to sudden changes in humidity. It is considered that resistive humidity sensors will be replaced with capacitive ones which have a wide sensing range and high responsiveness.
2004-03-08
Technical Paper
2004-01-1507
E.C. Chan, G. Karimi, D. Rose, J.R. Culham
This paper presents a comprehensive steady-state numerical study for an occupant-loaded vehicle seat with internal heating under severe winter conditions. A participant-based postural study showed that the nominal peak occupant seat pressure was 6kPa on the seat cushion, and 2.5kPa on the backrest. Uni-axial compression tests also indicated non-linear stress-strain behaviors in seating. Using an internally developed 3-D numerical model, it was found that the thermal resistance from contact and clothing was uniform (hc=144W·K−1·m−2) throughout the occupied regions. Their contribution to the overall thermal resistance was relatively minor, however, compared to that of skin (hoverall=27.2W·K−1·m−2). The thermal-mechanical simulations were conducted at heat input levels between 20W and 80W, using I-DEAS 10 and the TMG package as the simulation platform. Comparisons was also made between occupied seat with deflected and non-deflected mesh.
2004-03-08
Technical Paper
2004-01-1506
Chris Swales, Christoph Capellmann, Matt Crompton, Marcus Matthes
Customer clinics and surveys have revealed the increased importance to the customer of good defrost and demist performance in their vehicle. Achieving this level of performance, within the time and cost constraints of a modern vehicle development program, places increased reliance on computational (CAE) techniques. However, this paper describes how the optimum development process should be to combine this reliance upon CAE methods with a newly developed experimental technique. This new laser Doppler velocimetry (LDV) based methodology is employed at all stages of the development process and complements the CAE techniques perfectly. The end result is optimized airflow management within the vehicle cabin – essential if good defrost and demist performance is to be achieved in a vehicle.
2004-03-08
Technical Paper
2004-01-1509
Gaurav Anand, Milind Mahajan, Nagendra Jain, Balaji Maniam, Todd M. Tumas
e-Thermal is a vehicle level thermal analysis tool developed by General Motors to simulate the transient performance of the entire vehicle HVAC and Powertrain cooling system. It is currently in widespread (global) use across GM. This paper discusses the details of the air-conditioning module of e-Thermal. Most of the literature available on transient modeling of the air conditioning systems is based on finite difference approach that require large simulation times. This has been overcome by appropriately modeling the components using Sinda/Fluint. The basic components of automotive air conditioning system, evaporator, condenser, compressor and expansion valve, are parametrically modeled in Sinda/Fluint. For each component, physical characteristics and performance data is collected in form of component data standards. This performance data is used to curve fit parameters that then reproduce the component performance.
2004-03-08
Technical Paper
2004-01-1508
Se-Gil Park, Jin-Bok Kim, Sung-ho Song, Jang-hyung Cho
This study validated the process of air ventilation design and the increase of air ventilation performance using CFD(Computational Fluid Dynamics). The application to computing external flow include passenger compartments are designed by one model using new method. The shape and configuration of the air ventilation system determine the ventilation performance. Therefore, the air ventilation system configuration in the early stages need the aerodynamics simulation results of the cowl top, intake duct, blower, HVAC, passenger room and exit. Achievement of these design guides and new development process will be satisfied with predicting the ventilation performance in a short term and cutting down expenditure.
2004-03-08
Technical Paper
2004-01-1505
M.H. Shojaee, Fard P.H. Tehrani, A. R. Noorpoor, M. R. Adili
1 ABSTRACT The need to improve the climatic comfort within passenger vehicles is critical not only to passenger comfort but also to their safety. However, to make progress in this area, a good understanding of the flow behavior within the vehicle is required. In this paper, we use three-dimensional computer simulations to analyses the flow fields and temperature distributions of Heating, Ventilation and Air-Conditioning (HVAC) system of a generic passenger car. We examine the role of HVAC configuration and design parameters, such as air temperatures and velocities at the inlets, the size number and location of the system's inlets and outlets. In this way the model is simulated first for normal mode with 4 front outlet and then the model is optimized by adding a rear outlet, mounted on the back of the console. The models are designed and meshed in GAMBIT environment and solved in FLUENT 5.23software.
2004-03-08
Technical Paper
2004-01-1504
Tomohiro Waku, Norihiko Watanabe, Joji Matsumoto, Junichi Nakanishi
A windshield defroster has an important roll of clearing up fogged window glasses of a vehicle by blowing out warm air. In simulations parameters that affect the defogging time are the velocity, humidity and temperature of the flow from a defroster nozzle. However, individually varying all the parameters and investigating their effects will lead to many computing cases and long runtime. An approach that can considerably reduce calculation time is proposed. The approach is dictated by two key-steps: 1) First, steady-state velocity distributions for several different defroster flow rates are calculated; 2) Secondly, based on the pre-calculated velocity fields, the defogging time is estimated. This approach is compared to the conventional method that always couples all the parameters in transient calculations.
2004-03-08
Technical Paper
2004-01-1511
Adrian Tentner, Paul Froehle, Chung-Yi Wang
This work has explored the preliminary design of a Computational Fluid Dynamics (CFD) tool for the analysis of transient vehicle underhood thermo-hydrodynamic events using high performance computing platforms. The goal of this tool will be to extend the capabilities of an existing established CFD code, STAR-CD [1], allowing the car manufacturers to analyze the impact of transient operational events on the underhood thermal management by exploiting the computational efficiency of modern high performance computing systems. In particular, the project has focused on the CFD modeling of the radiator behavior during a specified transient. The 3-D radiator calculations were performed using STAR-CD, which can perform both steady-state and transient calculations on one of the cluster computers available at Argonne National Laboratory. Specified transient boundary conditions, based on experimental data provided by Adapco and DaimlerChrysler were used.
2004-03-08
Technical Paper
2004-01-1510
Todd M. Tumas, Balaji Maniam, Milind Mahajan, Gaurav Anand, Nagendra Jain
This paper describes a vehicle-level simulation model for climate control and powertrain cooling developed and currently utilized at GM. The tool was developed in response to GM's need to speed vehicle development for HVAC and powertrain cooling to meet world-class program execution timing (18 to 24 month vehicle development cycles). At the same time the simulation tool had to complement GM's strategy to move additional engineering responsibility to its HVAC suppliers. This simulation tool called “e-Thermal” was quickly developed and currently is in widespread (global) use across GM. This paper describes GM's objectives and requirements for developing e-Thermal. The structure of the tool and the capabilities of the simulation tool modules (refrigeration, front end airflow, passenger compartment, engine, transmission, Interior air handling …) is introduced. Model data requirements and GM's strategy for acquiring component data are also described.
2004-03-08
Technical Paper
2004-01-1513
Tarun Malik, Clark Bullard
HEVs idle their engine during the stops to meet the cooling loads. However, idling reduces fuel economy and increases emissions and engine wear. The paper focuses on exploring alternative strategies for air conditioning the HEV during stop times. Simulation analyses are used to identify fundamental differences and new technology tradeoffs encountered in HEVs. An analysis of cooling loads on a car under typical weather and driving conditions is combined with efficiency estimates for an advanced a/c system to compare different cooling strategies in terms of fuel usage and overall system COP. Options considered include belt-and electrically-driven compressors, with thermal and electrical storage technologies. The results of this parametric analysis narrow the range of cooling strategies to be considered for detailed analysis and prototype testing.
2004-03-08
Technical Paper
2004-01-1433
Basel Ismail, Daniel Ewing, James S. Cotton, Jen-Shih Chang
A non-destructive neutron radiography technique was used to measure the thickness of diesel soot deposited in the tubes of exhaust gas recirculation (EGR) cooling devices. Measurements were performed to characterize the fouling in single-tube and three-tube devices for laminar and turbulent flows. Measurements were also performed to characterize the effect that the design of the inlet header had on the deposition characteristics in the device. The analysis of the neutron images showed that the soot deposition in the single-tube device occurred at a faster rate for a turbulent flow than for a laminar flow. The deposition thickness decreased along the tubes for both flow regimes. More soot deposited in the center tube of the three-tube bundle for the expansion angle 45° inlet header suggesting there was an uneven distribution of the exhaust gas flow in the tube bundle.
2004-03-08
Technical Paper
2004-01-1478
Bapiraju Surampudi, Mark Walls, Joe Redfield, Alan Montemayor, Chips Ingold, Jim Abela
The electrification of accessories using a fuel cell as an auxiliary power unit reduces the load on the engine and provides opportunities to increase propulsion performance or reduce engine displacement. The SunLine™ Class 8 tractor electric accessory integration project is a United States Army National Automotive Center (NAC™) initiative in partnership with Cummins Inc., Dynetek™ Industries Ltd., General Dynamics C4 Systems, Acumentrics™ Corporation, Michelin North America, Engineered Machine Products (EMP™), Peterbilt™ Motors Company, Modine™ Manufacturing and Masterflux™. Southwest Research Institute is the technical integration contractor to SunLine™ Services Group. In this paper the SunLine™ tractor electric Air Conditioning (AC) system is described and the installation of components on the tractor is illustrated. The AC system has been designed to retrofit into an existing automotive system and every effort was made to maintain OEM components whenever modifications were made.
2004-03-08
Technical Paper
2004-01-1479
Nicholas Lutsey, John Wallace, C. J. Brodrick, Harry A. Dwyer, Daniel Sperling
Line-haul truck engines are frequently idled to power hotel loads (i.e. heating, air conditioning, and lighting) during rest periods. Comfortable cabin climate conditions are required in order for mandatory driver rests periods to effectively enhance safety; however, the main diesel engine is an inefficient source of power for this conditioning. During idle, the diesel engine operates at less than 10% efficiency, consuming excess diesel fuel, generating emissions, and accelerating engine wear. One promising alternative is the use of small auxiliary power units (APUs), particularly fuel cell-based APUs. The Institute of Transportation Studies (ITS-Davis) developed an ADVanced VehIcle SimulatOR (ADVISOR)-based model to quantify the costs and benefits of truck fuel cell APUs. Differences in accessories, power electronics, and control strategy between the conventional engine idling and APUequipped systems are analyzed and incorporated into the model.
2004-03-08
Technical Paper
2004-01-1381
Vito Melisurgo, Emilio Canuto, Domenico Vitali
Environment and A/C loop conditions strongly affect automotive evaporator performance. The aim of the activity is to identify the parameters it depends on and its functional dependence. Several evaporators, differing in size and technology, are tested on a bench, simulating a wide range of working conditions. The evaporator efficiency is introduced in order to correctly evaluate performances. The functional dependences from air velocity and humidity (key parameters) are shown, and a methodology to characterise automotive evaporators is proposed.
2004-03-08
Technical Paper
2004-01-1382
Srinivasan C. Rasipuram, Karim J. Nasr
Impinging jets are an established technique for obtaining high local heat transfer coefficients between a fluid and a surface. Factors such as jet attachment, surface angle, jet angle, separation distance between jet orifice and surface of impingement, and trajectory influence heat transfer dramatically. In the current study, the specific application of interest is air issuing from the defroster's nozzles of a vehicle and impinging on a glass windshield. The current work is aimed at studying the flow patterns off a vehicle windshield as a result of air issuing from various nozzle configurations. The effects of openings' geometry (circular vs rectangular), number of openings, angle that the windshield makes with the horizontal plane and angle of impinging jet, on windshield heat transfer is examined. An optimal configuration will be recommended for better heat transfer.
2004-03-08
Technical Paper
2004-01-1384
Kimiko Imai, Hiroyuki Kato, Tomohide Nishino, Kazuhiro Fukumoto
One of typical outcome of the desire for increasing passenger comfort is that especially for deodorant efficiency. Since customers are becoming so sensitive about cabin odor, development of more effective deodorant filter is strongly required. Out side of vehicle, which most being disliked is diesel odor, therefore, analysis on this diesel gas and investigation to identity the ingredient for the main cause of the strong odor were executed, and found that acetaldehyde gas is the one. Therefore, identification of the chemical that adsorb acetaldehyde gas with being impregnated in activated carbon was required, since activated carbon itself does not have ability of adsorbing acetaldehyde gas, and finally found appropriate chemical, vitamin Bx. At the end of this report, sensory evaluation result by twenty panelists with deodorant type cabin air filter impregnated with vitamin Bx, and its efficiency for deodorant will be shown at the end of this report.
2004-03-08
Technical Paper
2004-01-1383
David Roy, Pascale Petitjean, Alain Alexandre, Gwenael Burban
This paper presents the results of a study into an innovative system using a new type of technology for the automotive domain with the aim of improving passengers' thermal comfort. A study of the thermal interactions between the cabin and its passengers shows that radiative heat transfers clearly contribute to the passengers' thermal discomfort during the first few minutes of a vehicle's use. Therefore, to limit this kind of heat exchange, an innovative A/C system combining a conventional automotive A/C loop and a Heat Pipe Dashboard Panel has been developed. This reduces the dashboard temperature rapidly, immediately after starting the A/C system (70°C to 10°C in 3 min).
2004-03-08
Technical Paper
2004-01-1378
A. Aroussi, B. S. AbdulNour
The role of the Heating Ventilation and Air Conditioning (HVAC) system of passenger vehicles is to maintain the ambient environment within the vehicle at a temperature and humidity comfortable for the occupants, regardless of the external weather conditions. A commonly occurring problem in vehicles incorporating an HVAC system is that of unwanted water ingress into the cabin space. This occurs mainly in wet weather conditions, and is caused by the penetration of water through the cowl box and air filter. Large droplets are broken up by the blower motor into a fine mist that can collect in the interior of the car, causing window fogging, damage to carpets and passenger discomfort. Numerous solutions have been implemented by the automotive industry ranging from the placement of baffles within the cowl box of the vehicle to the use of variable area ducts.
2004-03-08
Technical Paper
2004-01-1377
Oliver Moos, Franz R. Klimetzek, Rainer Rossmann
Topology optimization in structural analysis is known for many years. In the presented procedure, “topology optimization” is used for computational fluid dynamics (CFD) for the first time. It offers the possibility of a very fast optimization process under utilization of the physical information in the flow field instead of using optimization algorithms like for example evolution strategies or gradient based methods. This enables the design engineer to generate in a first layout air guiding systems with low pressure drop in a fast and easy manner, which can than be improved further due to constraints of styling or production requirements. This procedure has been tested with many examples and shows promising results with a reduction in pressure loss up to 60% compared to a duct designed in CAD in the traditional way.
2004-03-08
Technical Paper
2004-01-1380
Maurizio Parrino, Roberto Carnino, Gianfranco Romitelli, Mery Dongiovanni, Alberto Mannoni
New car developments require that in the initial cabin cool-down it will be necessary to reach a lower average cabin temperature in a shorter time. The aim is to minimize the discomfort of the driver and occupants to just a few minutes during the initial condition of a hot cabin. Today, the target is reached by increasing the evaporator size, the blower capacity, and the compressor power. All of this is done so as to have as much cooling power available in the shortest possible time. After these transient conditions the A/C system generally works at lower heat rejection and the maximum capacity of the system is used in just a few cases. To limit any increase of the A/C system power, some control strategies can be defined and applied to reduce the thermal energy stored in the cabin. This will reduce the transient phase cool-down time, and thus improve fuel economy. A strategy consists of cooling the cabin with outside fresh air before starting the cool-down by use of the A/C system.
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