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Viewing 1 to 30 of 1934
2010-10-25
Journal Article
2010-01-2091
Michael J. Lance, C. Scott Sluder, Samuel Lewis, John Storey
Exhaust gas recirculation (EGR) cooler fouling has become a significant issue for compliance with nitrogen oxides (NOx) emissions standards. In order to better understand fouling mechanisms, eleven field-aged EGR coolers provided by seven different engine manufacturers were characterized using a suite of techniques. Microstructures were characterized using scanning electron microscopy (SEM) and optical microscopy following mounting the samples in epoxy and polishing. Optical microscopy was able to discern the location of hydrocarbons in the polished cross-sections. Chemical compositions were measured using thermal gravimetric analysis (TGA), differential thermal analysis (DTA), gas chromatography-mass spectrometry (GC-MS), x-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). Mass per unit area along the length of the coolers was also measured.
2010-10-25
Journal Article
2010-01-2090
Michael Marr, James S. Wallace, Silvio Memme, Sanjeev Chandra, Larry Pershin, Javad Mostaghimi
Surface temperature and heat flux were measured in a single cylinder SI engine piston when uncoated and with two different surface coatings: a metal TBC and YSZ. Average heat flux into the piston substrate was 33 % higher with the metal TBC and unchanged with the YSZ relative to the uncoated surface. The increase with the metal TBC was attributed to its surface roughness. However, the metal TBC and YSZ reduced peak heat flux into the substrate surface by 69 % and 77 %, respectively.
2010-04-12
Journal Article
2010-01-0548
Itsuhei Kohri, Yuji Kobayashi, Yukio Matsushima
The technology concerning thermo and fluid dynamics is one of the important fields which have made great progress along with rapid advance in computational resources. Especially, the CFD technology has been proved as successful contribution to the development of the engine cooling system. Therefore, this technology is widely used at early phase of the vehicle development. However, a serious problem has been remained that it does not always give practical precision. Particularly, the cooling fan is one of the primary components in the cooling system to determine the performance, while practical calculation method without depending on large resources has not established.
2010-04-12
Technical Paper
2010-01-0550
Devadatta Mukutmoni, Jaehoon Han, Ales Alejbegovic, Lionel Colibert, Mathieu Helene
Accurate simulation of long term transient thermal convection is critical to automotive related thermal and fluid flow applications. For instance, long term thermal transients are relevant to “key-off” situations in which a moving vehicle brought to a stop leads to a usual initial spike in temperature followed by a drop as the heat sources are turned off. Presented are simulations of a simple tube and plate configuration that captures the contribution of all heat transfer effects and complexities of a vehicle key-off process. The simulations were performed using a coupling between the flow solver and the thermal simulation package that includes conduction and radiation effects. The simulation results were compared with the test data for steady state forced convection cases and transient natural convection cases. Good agreement was observed for both steady and transient simulations.
2010-04-12
Technical Paper
2010-01-0549
Federico Brusiani, Gian Marco Bianchi, Alberto Bianchi D' Espinosa
The fluid dynamic of fully turbulent flows is characterized by several length scales bounded between the flow field dimension (large scales) and the diffusive action of the molecular viscosity (small scale). The large scales of motion are responsible of the main momentum transport while the small scales of motion are responsible of the energy dissipation into heat. In some cases the analysis of the large scales could be enough to explain the behaviour of the fluid dynamic system under investigation but, in other cases, the effect of all the turbulent scales have to be considered. A classic example of the latter working condition is the aerodynamic field where the efficiency is dictated by a fine equilibrium between mean flow conditions (driven by large turbulent scales) and laminar/turbulent boundary layer evolution (driven by small turbulent scales).
2010-04-12
Technical Paper
2010-01-0553
Peter Gullberg, Lennart Löfdahl, Peter Nilsson, Steven Adelman
The most common fan model to use in commercial CFD software today is the Multiple Reference Frame (MRF) model. This is at least valid for automotive under hood applications. Within the industry, for this typical application, this model is commonly known to under predict performance. This under prediction has been documented by the authors' of this paper in SAE paper 2009-01-0178 and VTMS paper 2009-01-3067. Furthermore has this been documented by S.Moreau from Valeo in “Numerical and Experimental Investigation of Rotor-Stator Interaction in Automotive Engine Cooling Fan Systems”, ETC, 7th European Conference on Turbomachinery, 2007. In preceding papers a specific methodology of use has been documented and it has been shown that the MRF model under predicts performance for the airflow in a cooling system commonly with 14% in volumetric flow rate. This is for a system dominated by inertial effects.
2010-04-12
Journal Article
2010-01-0552
Paul M. Rutkowski
Seat cooling systems are becoming more common as luxury features offered by original equipment manufacturers. Despite the extensive research & application of these systems, a thermal model and comfort requirements of the occupant/seat system have not been established. Without a model or thermal criteria for comfort, the seat temperature & humidity conditions required for optimal comfort can not be defined. A synopsis of the thermal comfort conditions required to achieve an occupant's subjective comfort as well as their comfort transition points are explained. In this context a model is designed specifically from a heat and mass transfer perspective between an occupant and a seat cooling system. Focus is given to the local conduction, convection, and evaporative cooling that takes place at the body to seat surface interface.
2010-04-12
Technical Paper
2010-01-0555
Ashok Patidar
This paper broadly describes two computational fluid dynamics (CFD) analysis methods to predict the de-icing phenomenon over the vehicle windshield and front side windows. 1 Solid Modeling Method: In this method, the windshield and window glasses are modeled as solid and 2 Shell Modeling Method: Here, windshield and side window glasses are modeled as shell elements and considered as wall with defined thickness as input condition to capture the correct heat transfer effect due to the conduction and convection from warm air to ice layer. The CFD analyses by both methods are done in two key-steps: a) First, steady state velocity distributions for several different defroster flow rates are calculated; b) Secondly, based on the pre calculated velocity fields, the defogging time is estimated. The solidification and melting model is used to simulate the ice melting process over the glasses available with commercial CFD software Fluent.
2010-04-12
Technical Paper
2010-01-0554
Felix Regin
The influence of environmental changes on underhood and underbody components of a vehicle is an important issue in new vehicle design as increased engine power, cabin comfort demands and package space limitations create an increasingly difficult problem to solve. Sufficient airflow needs to be available for adequate cooling of the underhood components. The amount of air mass flow depends on the underhood geometry details: positioning and size of the grilles, fan operation, and the positioning of the other underhood components. This paper describes a prediction methodology that significantly streamlines the process of passenger car underhood thermal management by utilizing state-of-the-art computer simulation of airflow. The methodology uses a complete 3-D CAD model of all pertinent underhood components of a passenger car with a general purpose Computational Fluid Dynamics (CFD) code to simulate underhood airflow.
2011-04-12
Technical Paper
2011-01-0656
Jason A. Lustbader, John P. Rugh, Brianna R. Rister, Travis S. Venson
In the United States, intercity long-haul trucks idle approximately 1,800 hrs per year primarily for sleeper cab hotel loads, consuming 838 million gallons of diesel fuel [1]. The U.S. Department of Energy's National Renewable Energy Laboratory (NREL) is working on solutions to this challenge through the CoolCab project. The objective of the CoolCab project is to work closely with industry to design efficient thermal management systems for long-haul trucks that keep the cab comfortable with minimized engine idling. Truck engine idling is primarily done to heat or cool the cab/sleeper, keep the fuel warm in cold weather, and keep the engine warm for cold temperature startup. Reducing the thermal load on the cab/sleeper will decrease air conditioning system requirements, improve efficiency, and help reduce fuel use. To help assess and improve idle reduction solutions, the CoolCalc software tool was developed.
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
Journal Article
2011-01-0130
Darshan Gopalrao Pahinkar, Vivek Kumar
An analytical model, which takes care of thermal interactions of human body with surroundings via basic heat transfer modes like conduction, convection, radiation and evaporation, is compiled. The analytical model takes measurable inputs from surroundings and specific human parameters. Using these parameters a quick calculation entailing all heat transfer modes ensues in net heat exchange of human body with surroundings. Its magnitude and direction decides the qualitative indication of thermal comfort of concerned human being. The present model is scaled on actual human beings by noting the subjective assessment in comfortable as well as uncomfortable surroundings. As a part of validation, it is implemented in an actual Climatic Wind Tunnel Heater test, where temperatures and other parameters on different parts of the body are noted down and fed to the model as input. Output of the equation is then compared with the subjective assessment of human beings.
2011-04-12
Journal Article
2011-01-0132
Sambhaji Jaybhay, Prasanna Nagarhalli, Sangeet Kapoor
In cold climatic regions (25°C below zero) thermal comfort inside vehicle cabin plays a vital role for safety of driver and crew members. This comfortable and safe environment can be achieved either by utilizing available heat of engine coolant in conjunction with optimized in cab air circulation or by deploying more costly options such as auxiliary heaters, e.g., Fuel Fired, Positive Temperature Coefficient heaters. The typical vehicle cabin heating system effectiveness depends on optimized warm/hot air discharge through instrument panel and foot vents, air directivity to occupant's chest and foot zones and overall air flow distribution inside the vehicle cabin. On engine side it depends on engine coolant warm up and flow rate, coolant pipe routing, coolant leakage through engine thermostat and heater core construction and capacity.
2011-04-12
Technical Paper
2011-01-0134
Shinichiro Hirai, Takuya Kataoka, Tatsumi Kumada, Takaaki Goto
Vehicles have been more required to save energy against the background of the tendency of ecology. As the result of improving efficiency of internal combustion engines and adoption of electric power train, heat loss from engine coolant, which is used to heat the cabin, decreases and consequently additional energy may be consumed to maintain thermal comfort in the passenger compartment in winter. This paper is concerned with the humidity control system that realizes reduction of ventilation heat loss by controlling recirculation rate of the HVAC system by using highly accurate humidity sensor to evaluate risk of fogging on the windshield. As the results of the control, fuel consumption of hybrid vehicles decreases and maximum range of electric vehicles increases.
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
Journal Article
2011-01-0644
Shailendra Kaushik, Kuo-huey Chen, Taeyoung Han, Bahram Khalighi
Energy efficient HVAC system is becoming increasingly important as higher Corporate Average Fuel Economy (CAFE) standards are required for future vehicle products. The present study is a preliminary attempt at designing energy efficient HVAC system by introducing localized heating/cooling concepts without compromising occupant thermal comfort. In order to achieve this goal of reduced energy consumption while maintaining thermal comfort it is imperative that we use an analytical model capable of predicting thermal comfort with reasonable accuracy in a non-homogenous enclosed thermal environment such as a vehicle's passenger cabin. This study will primarily focus on two aspects: (a) energy efficiency improvements in an HVAC system through micro-cooling/heating strategies and (b) validation of an analytical approach developed in GM that would support the above effort.
2011-04-12
Technical Paper
2011-01-0645
Devadatta Mukutmoni, Ales Alajbegovic, Jaehoon Han
Many critical thermal issues that occur in vehicles are uncovered only under more “thermally stressed” driving conditions that are transient in nature such as abruptly changing vehicle speed or turning off fan and engine. Therefore, for flow simulations to be useful in the vehicle design process, it is imperative that these simulations have the ability to accurately model long term transient thermal convection on full vehicles. Presented are simulations for a passenger vehicle driving at 60 kilometers per hour followed by a complete stop. The simulations were performed using a coupling between the flow and thermal solver and in the process, taking into account convection, conduction and radiation effects. Temperature predictions were made both under steady state conditions and during the key-off. Good agreement with the measurements was observed.
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
Technical Paper
2011-01-0523
William Nicholas Dawes, William Kellar PhD, Simon Harvey PhD, Neil Eccles PhD
Successful product development, especially in motorsport, increasingly depends not just on the ability to simulate aero-thermal behavior of complex geometrical configurations, but also the ability to automate these simulations within a workflow and perform as many simulations as possible within constrained time frames. The core of these aero-thermal simulations - and usually the main bottleneck - is generating the computational mesh. This paper describes recent work aimed at developing a mesh generator which can reliably produce meshes for geometries of essentially arbitrary complexity in an automated manner and fast enough to keep up with the pace of an engineering development program. Our goal is to be able to script the mesh generation within an automated workflow - and forget it.
2010-04-12
Technical Paper
2010-01-1209
Rance Stehouwer
As global automotive manufacturers prepare for the introduction of HFO-1234yf as the low GWP refrigerant solution in Europe, concern over compressor durability and material compatibility still remain. This preliminary study evaluates several different compressor types on several different tests to address these concerns. Compressor performance and teardown results are shared.
2010-04-12
Technical Paper
2010-01-1210
Lothar Seybold, William Hill, Christian Zimmer
This paper will examine the various design and performance criteria for optimized internal heat exchanger performance as applied to R134a and HFO-1234yf systems. Factors that will be considered include pressure drop, heat transfer, length, internal surface area, the effect of oil in circulation, and how these factors impact the effectiveness of the heat exchanger. The paper describes the test facility used and test procedures applied. Furthermore, some design parameters for the internal heat exchanger will be recommended for application to each refrigerant.
2010-04-12
Technical Paper
2010-01-1208
Stella Papasavva, William Hill, Roberto Monforte
The European f-Gas Directive phases out HFC-134a from Mobile Air Conditioning systems (MACs) in new vehicles by 2017. In the US pending California and USEPA regulations have incentives to phase out HFC-134a earlier than 2017. As a result industry is striving to transform all global markets to a single new refrigerant in order to simplify global marketing. One of the global tools to help evaluate alternatives during this transition is the global LCCP (Life Cycle Climate Performance) and the development of the GREENMAC- LCCP© model. This model has become the global standard to measure the Life Cycle Analysis (LCA) greenhouse emissions of any proposed alternative refrigerant for MACs starting from bench test results and supporting the car manufacturer choice of the best suitable alternative refrigerant from an environmental perspective.
2010-04-12
Technical Paper
2010-01-1207
Gursaran D. Mathur
Experimental investigations have been carried out to determine the AC system performance with HFO-1234yf as the working fluid. System level bench tests have been conducted with an AC system from a 2008 MY mid-sized sedan. The cabin interior condition is held constant at 20°C and 50% RH and evaporator airflow rate is varied from 5 to 9 m₃/min (83 to 150 lps). The dry bulb temperature for the engine compartment is varied from 25 to 45°C. The compressor speed is varied from 800 to 3000 rpm and the air velocity over the condenser is varied from 2 to 10 m/s (546 to 2730 lps). Detailed test results have been presented in the paper.
2010-04-12
Journal Article
2010-01-1205
Taeyoung Han, Kuo-Huey Chen, Bahram Khalighi, Allen Curran, Joshua Pryor, Mark Hepokoski
Virtual simulation of passenger compartment climatic conditions is becoming increasingly important as a complement to the wind tunnel and field testing to achieve improved thermal comfort while reducing the vehicle development time and cost. The vehicle cabin is subjected to various thermal environments. At the same time many of the design parameters are dependent on each other and the relationship among them is quite complex. Therefore, an experimental parametric study is very time consuming. The present 3-D RadTherm analysis coupled with the 3-D CFD flow field analysis takes into account the geometrical configuration of the passenger compartment which includes glazing surfaces and pertinent physical and thermal properties of the enclosure with particular emphasis on the glass properties. Virtual Thermal Comfort Engineering (VTCE) is a process that takes into account the cabin thermal environment coupled with a human physiology model.
2010-04-12
Technical Paper
2010-01-0806
Philip Keller, Wolfgang Wenzel, Michael Becker, Josh Roby
The thermal management of vehicles has increased in importance due to the significant role of friction and auxiliary losses in engine operation on CO2 emissions. To evaluate different system and component concepts regarding their influence on fuel consumption, simulation offers a wide range of opportunities. In this paper a fully integrated model is presented utilizing the GT-Suite commercial code. It contains a diesel engine system model, a cooling circuit including a simplified model for the cooler package in the vehicle front end and a vehicle model. The purpose of this model is the investigation of cooling system components and control strategies with different engine inputs. A significant run time advantage is achieved by using a mean value engine model, which has a reduced number of input parameters. The simulation using the integrated model can be carried out within an acceptable time frame which enables vehicle drive cycle analysis.
2010-04-12
Technical Paper
2010-01-0805
Masaharu Sakai, Toshinori Ochiai, Yasushi Mitsuishi
In recent years, CO2 emission constraint has been strengthened worldwide in order to fight global warming, and it is believed that the demand for compact and energy-saving car will be increasing year after year. On the other hand, larger interior space of vehicle to as-sure passenger comfort is demanded, so that the car air-conditioner is required to be smaller and energy saving efficient further more. Therefore, we have developed the new type of compact high-efficiency blower fan for compact car air-conditioning system (HVAC). Because of the requirements that the blower fan to be not only small size but energy-saving and low noise efficient, we started this development by modifications for basic blower fan internal air flow system of existing products. Generally, Sirocco fan, which is compact and able to supply high pressure, is often adopted for blower to be used for car air-conditioner.
2010-04-12
Technical Paper
2010-01-0804
Ho Teng
The passenger cabin heating and cooling has a considerable impact on the fuel economy for buses, especially during the waiting period. This problem becomes more significant for the hybrid buses for which the impact of the auxiliary load on the fuel economy is almost twice that on the conventional buses. A second-law analysis conducted in this study indicates that a heat-driven AC system has higher energy utilization efficiency than the conventional AC system. On the basis of this analysis, a concept waste-heat-driven absorptive aqua-ammonia heat pump system is proposed and analyzed. Results of the analysis show that the heat-driven system can reduce the engine auxiliary load significantly because it eliminates the conventional AC compressor. In the AC mode, its energy utilization efficiency can be up to 50%. In the heating mode, the effective efficiency for heating can be up to 100%.
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