在汽车中热化阶段和冷却阶段的热舒适性@中英文翻译@外文翻译

ORIGINALO. Kaynakli E. Pulat M. KilicThermal comfort during heating and cooling periods in an automobileReceived: 9 September 2003/Published online: 17 September 2004C211 Springer-Verlag 2004Abstract Most vehicles have a heating, ventilation andair conditioning (HVAC) device to control the thermalenvironments of interior of the vehicle. But, under hotsummer season or cold winter conditions, it is dicult toachieve and maintain thermal comfort in an automobilefrom the start up to the steady-state conditions. Duringthese transition periods, an understanding of humanthermoregulatory processes facilitates the design anddevelopment of improved heating and cooling systems.This study presents a model of thermal interactionsbetween a human body and the interior environment ofan automobile. The model is based on the heat balanceequation for human body, combined with empiricalequations defining the sweat rate and mean skin tem-perature. Simulation has been performed by the use oftransient conditions. The eects of both heating andcooling processes on the thermal comfort inside theautomobile are investigated. Results are compared withthe present measurements and available experimentaldata in the literature. It is shown that the agreementbetween the experimental data and the model is verygood.List of symbolsA surface area, m2cpspecific heat, J/(kg K)CSIG cold signalf correction factorh heat transfer coefficient, W/(m2K)i segment numberj air or fabric layers numberk conductiveheattransfercoefficient,W/(m K)L heat load, W/m2m body mass, kg_m mass flow rate from per unit area, kg/(s m2)M metabolic heat production rate, Wnl number of layers covering segmentp water vapor pressure, kPaQ heat transfer rate, Wr outer radius of fabric layerR thermal or evaporative resistance, (m2K)/Wor (m2kPa)/WS heat storage, Wt time, s (unless specified in minutes)T temperature,C176CTS thermal sensationV air velocity, m/sw skin wettednessW humidity ratio, kgH2O/kg dry air_W external work rate accomplished, WWSIG warm signalx thickness, mmGreek symbolsa ratio of skin layer mass to total body massg permeation efficiencySubscriptsa airal air layerb bodybl bloodcd conductioncl clothingcr corecv convectiondif diffusione exposed to convective and radiant environmentev evaporationO. Kaynakli E. Pulat M. Kilic (&)Faculty of Engineering and Architecture,Department of Mechanical Engineering, Uludag University,Gorukle Campus, 16059 Bursa, TurkeyE-mail: .trTel.: +90-224-4429183Fax: +90-224-4428021Heat Mass Transfer (2005) 41: 449458DOI 10.1007/s00231-004-0558-9ex exhaledf fabricint interface between outer clothing surface and asolid (such as the seat or back support)max maximumn neutralres respirationrd radiations saturatedsk skinsw sweatt total1 IntroductionThe comfort of the driver and passengers in a vehicle ispartially dependent on the quality and temperature ofair in the vehicle. Three interrelated systems are used toprovide the desired air temperature and quality. Theseare the ventilating system, the heating system and the airconditioning system. The purpose of the heating, venti-lation and air conditioning (HVAC) system of a vehicleis to provide complete thermal comfort for its occu-pants. Hence, it is necessary to understand the thermalaspects of the human body in order to design an eectiveHVAC system.In order to estimate the thermal comfort level,accurate information on the thermal environment isessential. The thermal environments can be roughlyrepresented by the temperature, velocity and humidity inthe automobile interior. In this interaction, heat andmass transfer take place together. Complete model ofhuman comfort consist of energy balances, equations forthe thermophysical properties of the fluids and materi-als, and heat and mass transfer characteristics.The passenger compartment of an automobile isheated in the winter months by circulating hot enginecoolant through a coolant-to-air heat exchanger thatwarms the compartments air. The heating system isdesigned to operate in conjunction with the air venti-lating system to provide the desired air temperature.With progressive reductions in engine size, stemmingfrom considerations of fuel economy, and correspondingreductions in the heat available for the passenger heatingsystem, there is interest in the development of moreeective systems to ensure passengers thermal comforteven in extreme conditions by considering market situ-ation. It is dicult to achieve and maintain passengerthermal comfort under extremely hot or cold drivingconditions. Some auxiliary heating or cooling apparatusmay greatly reduce the time needed to attain thermalcomfort. But, power requirements associated with thisapparatus are substantial.In hot season, air conditioning units are used. Whenair conditioning is mentioned, the first thought thatcomes to mind is cooling and, refreshing of air. Actually,the automobile air conditioning system not only coolsthe air but also cleans, dehumidifies, and circulates itfor the health and comfort of the passengers. Theseprocesses are performed by working in conjunction withthe heating and ventilating systems.Human thermal comfort has been the subject ofconsiderable previous study, and much of the availableinformation documented and codified 3. In the litera-ture, most of the studies have considered the thermalconditions are nearly uniform and steady over the entirebody of occupant. Less attention appears to have beendirected to comfort in an automobile, where conditionsare highly nonuniform and transient over the body ofthe occupant.Yig it 18 is to calculate the heat loses for each bodysegments and total loss for the whole body for five dif-ferent clothing ensembles. However heat losses from theparts of the body were not considered and clothingresistances were not evaluated for the thermal comfort.McCullough et al. 13, 14 published the insulationvalue, evaporative resistances of representative cloth-ing ensembles that were measured with a thermalmanikin. These parameters were also measured forcomponent fabrics using a sweating hot plateapparatus. A computer model was developed thatestimates the resistance to dry and evaporative heattransfer. Olesen et al. 15 studied five dierent cloth-ing ensembles with the same total thermal insulation,but very dierent distributions of the insulation on thebody in experiments with 16 sedentary subjects. Theasymmetry was ranging from nude upper part to nudelower part of the body. Their experimental study willprovide a method for quantifying the nonuniformityof a clothing ensemble and examine how it influenceslocal thermal discomfort.Tanebe et al. 16, investigated sensible and latentheat loss from several parts of the human body by theuse of a manikin. For each considered part of thebody, total heat transfer coecient and thermal resis-tance were found. Since their study was performed inconstant temperature environment, it did not give anyresult about the thermal comfort. Kaynakli et al. 11reported a study in which the human body is dividedinto 16 sedentary segments, a computational model ofthermal interactions between each of 16 body segmentsand the environment is developed. By the use of themodel, skin wettedness and latent (sweating, diusion)and sensible (conduction, convection, radiation) heatlosses from each body segment and whole body arecalculated for both sitting and standing postures.Kaynakli et al. 12 presented a numerical model of theheat and mass transfer between the human body andthe environment. In their study, the required environ-mental and personal conditions for satisfaction of thepeople obtained under steady-state conditions, andtotal sensible and latent heat losses, skin temperature,wettedness, predicted mean vote (PMV) and predictedpercentage of dissatisfied (PPD) values were calculatedvia simulation.450Chakroun and Al-Fahed 7 presented a study ofthe temperature variation and thermal comfort insidea car parked in the sun during the summer months inKuwait. They also considered the eect of using dif-ferent combinations of internal covering on the tem-perature inside the car. Burch et al. 4 reported theresults of a series tests on passenger thermal comfortduring warm-up under severe winter driving condi-tions. They found that low-power electric heating padsinstalled on the seat and back support greatly reducethe time needed to attain thermal comfort. Furtherreductions in warm-up time can be achieved byinstalling electric heaters in the air ducts, although thepower requirements associated with this method aresubstantial. In addition to their experimental study,they presented an analytical study on this subject inthe paper of Burch et al. 5.Heating and cooling periods from the start up ofthe vehicle require some time to reach steady-stateconditions. During these periods, conditions are highlynonuniform over the body of the occupant. Thevehicle passenger experiences localized chilling due tocontact with an initially cold seat or steering wheel,nonuniform radiant heat transfer with the surround-ings, localized solar irradiation, and nonuniform airvelocities that vary depending on the location of theair registers and dashboard control settings. Thus, inaddition to the air temperature, several other factorshave a bearing on the thermal comfort of the pas-senger. Consequently, there is substantial interest inthe development of more ecient techniques forachieving and maintaining passenger thermal comfortin an automotive environment.This study presents a model of thermal interactionsbetween a human and the interior environment of anautomobile. Since, segmental analysis permits thedetermination of local discomforts by considering theclothing insulation asymmetry eects in the relativelysmall volumes such as automobile cabin, the presentmodel is based on the heat balance equation for humanbody by dividing it into 16 segments. By combiningGagge et al.s 10 and Olesen et al.s 15 approaches,all body segments are considered as two-concentriccylinders and required new data such as surface areasof body segments and their masses are refined from theexisting literature. In this way, apart from the Gaggeet al.s 10 model, it is tried to determine the localdiscomforts by calculating the thermal interactions ofeach segment and the skin temperature and wettedness.Simulation has been performed by the use of transientconditions. The eects of both heating and coolingprocesses on the thermal comfort inside the automobileare investigated. Experiments were also conducted forcooling periods. Until the thermal comfort reached inthe automobile compartment, the temperature and thehumidity changed dramatically. Driver and passengersare greatly aected by these changes. The simulationresults and experimental data were compared, in orderto validate the present model.2 Mathematical modelThe velocity of conditioned air that flow over passengeris very important from comfort point of view in smallcompartments that have large heating and coolingcapacity especially such as automobile cabin. Flowingair over driver and passengers injected by inlet vents hasnot same value on any occupants body. Although it is agood approximation to take average velocity for typicalindoor conditions, this results important mistakes byconsidering automobile interior. Local air velocities onthe body of sitting passenger were determined experi-mentally by Burch et al. 5 (Table 1). In this study,determination of heat losses from various regions ofpassenger is based on these velocity values.The model used in this study is based on the sameapproach described in the study of Olesen et al. 15. Inthis study, human body is divided by 16 regions byconsidering clothing groups and local air velocities onthe body in order to investigate the eects of thermalenvironment to occupants especially driver in detail forboth winter and summer condition. In Table 2, surfaceareas and their fractions of total body surface area aregiven.To compute temporal temperature variations byusing stored energy in the body segments it is requiredthe masses of these segments. The masses of body seg-ments and their fractions of the total body mass areshown in Table 3.By considering the human body as whole, mean skintemperature gives an idea from thermal comfort point ofview but the temperatures of the extremities such ashand, foot and face or naked parts of human body mayincrease or decrease unwanted values. By using thedeveloped model, time rate of changes of the parametersthat aect the thermal comfort such as sensible andlatent heat losses each of 16 regions, skin temperaturesand skin wettedness may be examined.2.1 Thermal and physiological modeling of human bodyA two-compartment transient energy balance modeldeveloped by Gagge et al. 10 represents the body astwo concentric cylinders the inner cylinder represents theTable 1 Local air velocities on the body 5Region Air velocity(m/s)Head 0.13Trunk 0.11Right shoulder 0.12Left shoulder 0.13Legs 0.11Right knee 0.18Left knee 0.21Right ankle 0.66Left ankle 0.62451body core (skeleton, muscle, internal organs) and theother cylinder represents the skin layer. This model, byconsidering instantaneous heat storage of the core andthe skin compartment, assumes that temperatures ofthese compartments change with time. The thermalmodel is described by two coupled heat balance equa-tions, one applied to each compartment 3:ScriMiC07pt _WiC0 QresiQcr;skiC0C11SskiQcr;skiC0 QcdiQcviQrdiQevi2where, M rate of metabolic heat production, 7pt _W rateof mechanical work accomplished, Qrestotal rate ofrespiratory heat loss, Qcr,skrate of heat transport fromcore to skin, Qcn,Qcv,Qrdrate of heat loss from skin toenvironment by conduction, convection and radiationrespectively. Scrand Sskthat denotes stored energies incore and skin layer causes instantaneous temperaturechanges in these compartments. These eects are ex-pressed with following equations:dTcridtScri1C0 a micp;bC0C1 3dTskidtSskiamicp;bC0C1 4where m is the body segment mass, cp,bis the specificheat of the body. Qcvand Qrdterms in Eq. 2 are the heattransfers with convection and radiation and can be cal-culated with following relation:QcvQrdiTskiC0ToiAeiRcli 1=hcvihrd fcliC1385where, Aeis the surface area of the body segmentsexposed to the environment (total area minus the area incontact with seat, back support, etc.), fclis the ratio ofthe surface areas of the clothed body and the nude body.Operative temperature value (To) that includes averageradiation and ambient air temperature is given asfollows:ToihrdC22TrdhcviTahrdhcvi6For radiative heat transfer coecient the value of4.7 W/(m2K) is used since it is suciently accurate forinternal conditions 3 and convective heat transfercoecient values of each segment of the body are takenTable 2 Surface areas of the body segments 15Body segments Segment number Surface area m2 Fraction of total body surface area % Left foot 1 0.062 3.5 Right foot 2 0.062 3.5 Left fibula 3 0.140 8.0 Right fibula 4 0.140 8.0 Left thigh 5 0.160 9.1 Right thigh 6 0.160 9.1 Pelvis 7 0.080 4.6Head 8 0.180 10.4Left hand 9 0.050 2.9 Right hand 10 0.050 2.9 Left forearm 11 0.062 3.5 Right forearm 12 0.062 3.5 Left upperarm 13 0.077 4.4 Right upperarm 14 0.077 4.4 Chest 15 0.185 10.6Back 16 0.204 11.7The whole body 1.751 100.0 Table 3 Mass of the body segments 17BodysegmentsSegmentnumberMass(kg)Fraction of totalbody mass (%)Foot 12 1.16 1.45Fibula 34 3.72 4.65Thigh 56 8.00 10.00Pelvis 7 6.78 8.48Head 8 6.48 8.10Hand 910 0.48 0.60Forearm 1112 1.28 1.60Upperarm 1314 2.24 2.80Trunk 1516 32.98 41.22The whole body 80.00 100.00452as described in de Dear et al. 8. The total latent heatloss from the skin due to evaporation, Qev, is given byQeviwi psk;siC0paC0C1AiRcli=gclLR1=hcvi fcli LR7where, w is the wettedness ratio, psk,sis the saturatedwater vapor partial pressure at the skin temperatureand pais the water vapor partial pressure in theambient air, gclis permeation eciency of the clothingand LR is the Lewis Relation which is the ratio of theevaporative heat transfer coecient to the convectiveheat transfer coecient. McCullough et al. 14 havebeen found an average value of gcl=0.34 for commonindoor clothing.The total skin wettedness (w), includes wettednessdue to regulatory sweating (wsw) and to diusionthrough to skin (wdif) is given bywswihfg_mswiQev;maxi8wdifi0:06 1C0wswi 9wiwswiwdifi10Maximum evaporation potential, Qev,maxoccurs whenthe skin surface is completely wetted (w=1).In an automobile, a significant portion (1520%) ofthe body surface area is in contact with a seat, backsupport and steering wheel 5. This portion does notlose heat by convection and radiation. The heat lossfrom the skin due to conduction is given byQcdiTskiC0TintRcliAcdi11In the two-node model, heat exchange between thecore and the skin occurs by direct contact andthrough the skin blood flow. A constant averagethermal conductance, Kcr,sk=5.28 W/(m2K) is as-sumed over the body. The heat flow from core to skinis as follows:Qcr;ski Kcr;skcp;bl_mblC0C1TcriC0TskiAi12The specific heat of the blood, cp,blis 4,187 J/(kg K).Respiratory heat loss is approximately 10% of total heatloss 9. The heat loss due to respiration is given byQres _mrescp;aTexC0TahfgWexC0WaC2C3Ab13where _mresis the mass flow rate of air inhaled, Texand Taare the exhaled air and the ambient air temperatures,respectively. Wexand Waare the exhaled air and theambient air humidity ratio, respectively. The heat ofvaporization (hfg) is 2.43106J/kg._mres 2:58C210C06C0C1M 14Tex 32:60:066Ta32Wa15Wex 0:02770:000065Ta0:2Wa16The ratio of the skin mass to total body mass (a)ismodeled as the following f