Investigation of indoor thermal comfort under transient conditions

ARTICLE IN PRESS

0360-1323/$ - se

doi:10.1016/j.bu

�Correspond4428021.

E-mail addr

Building and Environment 40 (2005) 165–174

www.elsevier.com/locate/buildenv

Investigation of indoor thermal comfort under transient conditions

Omer Kaynakli, Muhsin Kilic�

Mechanical Engineering Department, Faculty of Engineering and Architecture,Uludag University, TR-16059 Bursa, Turkey

Received 31 March 2004; received in revised form 21 May 2004; accepted 25 May 2004

Abstract

In industrialized countries about 90% of the time is spent indoors. In indoor, thermal comfort can be basically predicted by the

environmental parameters such as temperature, humidity, air velocity and by the personal parameters as activity and clothing

resistance. In this study, a mathematical model of thermal interaction between human body and environment was established and

the effect of clothing and air velocity was examined under transient conditions. By the developed model, human body has been

separated to 16 segments and possible local discomforts are taken into consideration. Using the model, changes in the sensible and

latent heat losses, skin temperature and wettedness, thermal comfort indices were calculated. In a hot environment latent heat loss

increases by means of sweating. Because of over wetted skin, comfort sense goes worse. Especially, at feet and pelvis skin wettedness

reaches maximum level. Sensible and latent heat losses rise and the skin temperature and wettedness decrease with increasing air

velocity.

r 2004 Elsevier Ltd. All rights reserved.

Keywords: Thermal comfort; Indoor conditions; Transient energy balance model

1. Introduction

A human body can be considered as a thermalmachine, which uses food and oxygen as fuel. As it isknown, in thermal machines, some of energy isconverted into mechanical work while some flows outin various ways. Also in human body, heat appears bymeans of chemical reactions, which are called metabo-lism. The heat produced by the body must be transferredto environment regularly to maintain a vital functionand comfort of the body (ASHRAE [1], Chaffee andGreisheimer [2], Butera [3]). In order to achieve thisgoal, the rate of heat generation of the body must beequal to the rate of heat loss from it (Butera [3]).Thermally uncomfortable or unrelax environments havea negative influence on the performance of workers soon effectiveness of the work (Srinavin and Mohamed [4],

e front matter r 2004 Elsevier Ltd. All rights reserved.

ildenv.2004.05.010

ing author. Tel.: +90-224-4429183; fax: +90-224-

ess: [email protected] (M. Kilic).

Daanen et al. [5]). There is no physiological data todetermine thermal comfort exactly. But the mean skintemperature can be a good guide.People living in industrialized countries spent about

90% of their time indoors (Hoppe and Martinac [6]).Because of this, air conditioning and thermal comfortconditions have importance. Today air conditioning isused in many parts of the world, often in combinationwith heating and ventilation in HVAC systems. Thepurpose of most systems is to provide thermal comfortand an acceptable indoor air quality for humanoccupants. But numerous field studies have documentedsubstantial rates of dissatisfaction with the indoorenvironment in many buildings (Fanger [7]). One ofthe main reasons is that the existing ventilation is notenough especially in the large volume areas. Indoor airconditioning and thermal comfort conditions can bemore easily controlled in smaller volumes of thebuildings especially offices, rooms and shops. However,some areas, such as corridors, lobbies and volumes getdirect sun light, cannot be easily controlled with respect

www.elsevier.com/locate/buildenv

ARTICLE IN PRESS

Nomenclature

cp specific heat, kJ/(kgK)CSIGsk cold signal from the skinDISC discomforth heat transfer coefficient, W/(m2 K)i segment numberj air or fabric layers numberK average thermal conductance, W/(m2K)_m mass flow rate, kg/s

M rate of metabolic heat production, W=m2

nl number of layers covering segmentp water vapor pressure, kPaQ heat flow rate, W=m2

r outer radius of fabric layer, mR thermal or evaporative resistance, (m2 K)/W

or (m2 kPa)/WRH relative humidityT temperature, 1CTSENS thermal sensationV velocity, m/sw skin wettednessWSIGb warm signal from the bodyWSIGcr warm signal from the coreWSIGsk warm signal from the skinZe evaporative efficiency

Subscripts

a air or ambientact activityal air layerb bodybl bloodc coldcl clothingcr corecv convectiondif diffusione evaporationf fabrich hotmax maximumo operativerd radiationreq requiredres respirationrsw sweatings sensiblesk skint total

O. Kaynakli, M. Kilic / Building and Environment 40 (2005) 165–174166

to thermal comfort conditions. When people use theseareas, their thermal comfort conditions will be changeddepending on the conditions they are exposed. In thewarm or hot seasons, these volumes have highertemperatures than the more controlled smaller volumes,hence human body starts to heating when the peopleenters these zones. Therefore, the architects andengineers need to know that the human body responses.This study mainly focused to obtain the information ofthe human responses and the thermal comfort condi-tions when these areas are used.In enclosures the parameters, which effect thermal

comfort, can be examined in two main groups, personaland environmental. Personal parameters are clothingand activity. Environmental parameters are air tem-perature, air velocity, relative humidity and meanradiant temperature. Since each parameter affects thehuman comfort differently, body reaction changes withthe variation of these parameters. Understanding ofhuman adaptation period to environmental conditionswill be playing an important role in the design anddevelopment of HVAC equipments used in all enclosurevolumes. Therefore, the transient energy balance modelis one of the important tools to determine the optimumthermal comfort conditions during warm-up and cool-down process.

In previous studies Kaynakli et al. [8] reported a studyin which the human body is divided into 16 sedentarysegments, a computational model of thermal interac-tions between each of 16 body segments and theenvironment is developed. By using the model, skinwettedness and latent and sensible heat losses from eachbody segment and whole body are calculated for bothsitting and standing postures. Burch et al. [9] studiedthermal comfort conditions in an automobile at heatingperiod for severe winter conditions. In their study, thechanges of the temperatures of interior and body partscontacted with solid surfaces were investigated duringstandard heating process in a very cold day (� �20 1C).During this period, the effects of the heat losses frombody by conduction, convection and radiation on thethermal sensation (TS) were investigated. But, heatlosses from the body segments, and their skin tempera-tures were not considered in their study. Guan et al.[10,11] examined human thermal comfort under highlytransient conditions in an automobile. In the mathema-tical model, physiological and psychological factorswere combined, and environmental and personal para-meters were used as inputs to determine the physiolo-gical responses. They predicted whole body and localthermal sensation for winter and summer conditions aswell. Butera [3] described the factors which affect

ARTICLE IN PRESS

Fig. 1. Thermal resistance network of two-compartment model [9].

O. Kaynakli, M. Kilic / Building and Environment 40 (2005) 165–174 167

thermal comfort conditions and heat exchange mechan-isms between the body and the environment in detailand summarized the heat and mass transfer equationsbetween the body and environment. Also the change ofpredicted mean vote (PMV) with the activity for variousair velocity and clothing were given. Guan et al. [12]summarized the current advances in thermal comfortmodeling for both building and vehicle HVAC applica-tions that have occurred in the literature. Tanebe et al.[13] investigated sensible heat losses from several partsof the human body by the use of a thermal manikin. Foreach considered part of the body, total heat transfercoefficient and thermal resistance were found. Sincetheir study was performed in constant temperatureenvironment, it did not give any result about the thermalcomfort. Fiala et al. [14] modeled the physiologicalmechanisms within the body, thermal exchanges be-tween the body and its environment, and gave thedetailed numerical model in their study. Each bodysegment is modeled as five body layers (core, muscle, fat,inner skin and outer skin). In their model, localvariations of surfaces convection, directional radiationexchange, evaporation and moisture collection at theskin, and the nonuniformity of the clothing ensembleswere considered.In this study, a numerical model of heat interaction

between the body and its environment was presented.Thermal comfort conditions of an indoor were investi-gated by using the transient energy balance model.Human body was divided into 16 sedentary segments,and sensible and latent heat losses, skin temperature,skin wettedness of each segment were calculated.Calculations were performed for 1-h period, andclothing resistance and air velocity effects are takeninto consideration. The results were compared with theavailable experimental and numerical studies in theliterature. Using the present model, the calculated valuesof heat loss, skin temperature and wettedness are shownto be in good agreement with the available results in theliterature.

2. Mathematical modeling

A two-compartment (core and skin) model developedby Gagge et al. [15] represents the body as twoconcentric cylinders. Inner cylinder includes inner sideof the body (skeleton, muscles and internal organs) andthe outer cylinder includes skin and its related tissues.Fig. 1 illustrates thermal resistance network betweenthese two compartments and the environment.Some of the heat generated in the body was

transferred via sensible and latent heat losses from innercompartment to environment with respiration (Qres).Heat is transferred between the core and the skin bothby direct contact and through the skin blood flow. The

heat is transferred from the skin to environment byconvection (Qcv), radiation (Qrd) and by evaporation ofthe sweat (Qev).This paper based on the same approach that was used

in the study of Olesen et al. [16] in which the body wasdivided into 16 segments that are uniformly clothed. Inthe model, dry and evaporative resistances are calcu-lated for each body segments, which are treated asconcentric cylinders. Therefore, each successive layerhas a larger area for heat transfer. There are somedifficulties in calculating the resistance of dry andevaporative heat transfer of clothing ensembles. Theheat flows from the body through alternating clothingand air layers. The total thermal resistance (Rt) and thetotal evaporative resistance (Re;t) for each segment canbe calculated as (McCullough et al. [17])

RtðiÞ ¼ RaðiÞrði; 0Þ

rði;nlÞþ

Xnlj¼1

Ralði; jÞrði; 0Þ

rði; j � 1Þ

�

þRf ði; jÞrði; 0Þ

rði; jÞ

�; ð1Þ

Re;tðiÞ ¼ Re;aðiÞrði; 0Þ

rði;nlÞþ

Xnlj¼1

Re;alði; jÞrði; 0Þ

rði; j � 1Þ

�

þRe;f ði; jÞrði; 0Þ

rði; jÞ

�; ð2Þ

where Ra and Re;a are the thermal and evaporativeresistances of the outer air layer, Ral and Re;al are thethermal and evaporative resistances of the air layerbetween the clothing layers, respectively. Detailedinformation about these resistances may be found inMcCullough et al. [17] and Kaynakli et al. [8]. Since thecircumference area increase with radius, each resistanceterm is multiplied by radius ratio of the related layers.The sensible heat losses (convective and radiative) foreach segment are calculated as follows:

Qs;skðiÞ ¼T skðiÞ � ToðiÞ

RtðiÞ(3)

where T sk and To are the skin and operative tempera-tures, respectively. Operative temperature can be

ARTICLE IN PRESSO. Kaynakli, M. Kilic / Building and Environment 40 (2005) 165–174168

calculated as

ToðiÞ ¼hcvðiÞTa þ hrdT rd

hcvðiÞ þ hrd; (4)

where hcv and hrd are convective and radiative heattransfer coefficients, respectively. hrd is assumed 4.7W=m2K (ASHRAE [1]). The convective heat transfercoefficients for entire body and for all segments of thebody are given in de Dear et al. [18]. Evaporative heatloss from skin (Qe;sk) depends on the difference betweenthe water vapor pressure at the skin (psk) and in theambient environment (pa), and the amount of moistureon the skin ðwÞ

Qe;skðiÞ ¼wðiÞðpskðiÞ � paÞ

Re;tðiÞ: (5)

Total skin wettedness ðwÞ includes wettedness due toregulatory sweating ðwrswÞ and to diffusion through theskin ðwdif Þ: wrsw and wdif are given by

wrsw ¼_mrswhfg

Qe;max; (6)

wdif ¼ 0:06ð1� wrswÞ; (7)

where Qe;max is the maximum evaporative potential,_mrsw is the rate of sweat production, hfg the heatof vaporization of water. Maximum evaporative poten-tial occurs when the skin surface is completely wettedðw ¼ 1Þ:

2.1. Control signal equations

The parameters used in the control signals are thecore, skin and mean body temperature. The blood flowbetween the core and skin per unit of skin area can beexpressed mathematically as

_mbl ¼ ½ð6:3þ 200WSIGcr=ð1þ 0:5CSIGskÞÞ�=3600 (8)

where WSIG and CSIG are warm and cold signal fromthe body thermoregulatory control mechanism, respec-tively. When actual temperatures of the body (core, skinand body) are greater or smaller than neutral tempera-tures, warm or cold signal is sent, respectively.Numerical values of these signals were calculated asdifference of actual and neutral temperatures, and theyonly take on positive values (ASHRAE [1], Doherty andArens [19]).The heat exchange between the core and skin can be

written as

Qcr;sk ¼ ðK þ cp;bl _mblÞðTcr � T skÞ; (9)

where K is average thermal conductance, cp;bl is specificheat of blood. The rate of sweat production per unit ofskin area is estimated by

_mrsw ¼ 4:7 10�5WSIGb expðWSIGsk=10:7Þ: (10)

2.2. Prediction of thermal comfort

The compartment model uses empirical expressions topredict thermal sensations (TSENS) and thermal dis-comfort (DISC). Scales of TSENS and DISC indices areas follow: for the TSENS, 5 intolerable hot/cold, 4very hot/cold, 3 hot/cold, 2 warm/cool, 1 slightlywarm/cool, 0 neutral. For the DISC, 0 comfortable, 1slightly uncomfortable but acceptable, 2 uncomforta-ble and unpleasant, 3 very uncomfortable, 4 limitedtolerance, 5 intolerable. TSENS and DISC values canbe calculated by following equations (ASHRAE [1]):

TSENS ¼

0:4685ðTb � Tb;cÞ TboTb;c

4:7ZeðTb � Tb;cÞ=ðTb;h � Tb;cÞ Tb;cpTbpTb;h

4:7Ze þ 0:685ðTb � Tb;hÞ Tb;hoTb

8><>:

(11)

DISC ¼

0:4685ðTb � Tb;cÞ TboTb;c

4:7ðQe;rsw � Qe;rsw;reqÞ

Qe;max � Qe;rsw;req � Qe;dif ÞTb;cpTb:

8><>:

(12)

3. Results and discussion

The equations were given under the mathematicalmodeling, section of which transferred to Delphi 6programming language. The simulation was performedto determine the heat and mass transfer between thebody and its environment, and also thermal comfort.For 1-h period, changes in convective, radiative,evaporative heat losses, the core and skin temperatures,skin wettedness and thermal comfort indices werecalculated. The simulation results have been comparedwith the available experimental and numerical data inthe literature. Comparisons were performed with theexperimental data of Burch et al. [9], Tanebe et al. [13],Stolwijk and Hardy [20], and with the numerical resultsof Huizenga et al. [21].In Table 1, sensible heat losses from a whole human

body and body segments are given. In the calculationswith the present model, following values are used; Rt ¼

0:205m2K=W; Re;t ¼ 0:0326m2kPa=W; Ta ¼ T rd ¼

24:7 1C. Results obtained from the model, are comparedwith the experimental measurements of Tanebe et al.[13]. It can be seen that both results are in a goodagreement.Stolwijk and Hardy [20] and Huizenga et al. [21]

considered the effects of step-change of ambientconditions (from 30 1C, 40% RH to 48 1C, 30% RH)on the body skin temperature and evaporative heat loss.Variation of skin temperature and evaporative heat lossduring examined periods is comparatively given in Fig. 2(a) and (b), respectively. Results obtained from thepresent model are also in good agreement with the

ARTICLE IN PRESS

Table 1

Comparison of heat losses from each part of the body with

experimental results

Segment number Rate of sensible heat loss ðW=m2)

Experimental a Present study Difference (%)

1 70.00 78.90 12.7

2 70.00 78.90 12.7

3 50.00 49.48 1.0

4 51.35 50.77 1.1

5 45.57 44.40 2.6

6 48.60 47.28 2.7

7 35.00 32.44 7.3

8 44.43 43.57 1.9

9 57.00 58.68 2.9

10 60.71 65.97 8.7

11 35.57 32.44 8.8

12 40.00 37.67 5.8

13 37.30 35.17 5.7

14 41.43 39.32 5.1

15 38.86 36.49 6.1

16 43.10 41.71 3.2

Whole body 45.30 45.97 1.5

aTanebe et al. [13].

Fig. 2. Comparison of measured [20] and simulated ([21] and present

study) skin temperatures and evaporative heat loss during temperature

step-changes. (a) skin temperature and (b) evaporative heat loss.


results of Stolwijk and Hardy [20] and Huizengaet al. [21].In the study of Burch et al. [9], interior air was heated

from �20 to 20 1C, and during this period, variation ofheat losses from body and thermal sensation values wereinvestigated. In these calculations with the presentmodel, following values were used; Mact ¼ 136W, Rcl ¼

1:5 clo (� 0:23m2K=W), and initial values of core andskin temperatures as 37 and 34 1C, respectively. Relativehumidity and mean radiant temperature were taken as0.35 and T rd ¼ 0:94Ta � 1:38 in heating period, respec-tively. In Fig. 3, thermal sensation values are comparedwith the Burch et al. [9] during the warm-up period. Itcan be seen that the agreements between the results arevery well.In Figs. 4–7, the change of heat losses from the whole

body, mean skin temperature, wettedness and thermalcomfort indices are given, respectively, for Mact ¼

80W=m2 (about office activity), the thermal resistanceof clothing 0.5 and 1 clo, and ambient temperature 30

Fig. 3. Comparison of thermal sensation during warm-up process.

Fig. 4. Variations of heat loss from whole body with time

(Mact ¼ 80W=m2; Ta ¼ T rd ¼ 30 1C, RH=50%, V ¼ 0:1m/s).

ARTICLE IN PRESS

Fig. 5. Variations of average skin temperature with time


Fig. 7. Variations of thermal comfort indices with time


Fig. 6. Variations of average skin wettedness with time



1C. In these calculations the ambient and the meanradiant temperatures are equal (Ta ¼ T rd), relativehumidity 50%, mean air velocity over body 0.1m/s areaccepted. To determine the effect of clothing resistanceon the thermal comfort, two types of clothing areexamined: 0.5 clo illustrates summer clothing and 1 cloillustrates a business suit (McCullough et al. [17]). InFig. 4 it can be seen that for both clothing, the latentheat loss from skin due to evaporation exceeds thesensible heat loss after a period. Because of highambient temperature, body cannot lose sensible heatvia convection and radiation, sufficiently. In thissituation, sweating, which is a physiological controlmechanism, begins and latent heat loss increasesimmediately. Naturally, sensible heat loss at 1 cloclothing resistance is less than at 0.5 clo, that’s whyfabrics and air layers between clothing layers, whichdecrease the heat transfer, are important parameters.The cause of a slight rise at sensible heat transfer in thebeginning time is the increase in skin temperature. Theincrease in the skin temperature is shown in Fig. 5.When the mean body skin temperature increases thetemperature difference between the skin and theenvironment increases and so does the sensible heatlosses. One of the important parameters that affect thecomfort sensation is skin wettedness and its variationwith time is given in Fig. 6. Skin wettedness increaseswith time elapsed in the ambient. For the heat balanceof the body with the environment, the body increasestotal heat losses via raising the skin wettedness. Becausethe skin wettedness is an indirect result of sweatgeneration and the evaporative potential of the environ-ment, the increasing in the clothing resistance causes notto be able to evaporate the sweat generated easily, soskin wettedness is higher at 1 clo clothing resistance thanat 0.5 clo. Naturally, high skin temperature and wetted-ness have a negative influence on the sense of comfort(Fig.7). Since skin temperature and wettedness increasewith elapsed time in the ambient, ambient was perceptmore uncomfortable.Although the thermal comfort indices give an idea

about the comfort level of an ambient but some timesthey are not enough. A person may feel thermallyneutral for the whole body, but might not be comfor-table if one part of the body is warm and another cold.Therefore, thermal comfort also requires that no localwarm or cold discomfort exists at any part of the humanbody. So, to determine the local discomfort, it isimportant to examine the human body into 16 segments.Fig. 8 shows that the sensible and latent heat losses fromforearm and foot for 0.5 clo, Figs. 9 and 10 show skintemperatures and wettedness variations with time,respectively. It can be seen that the heat loss from thefoot is less than the heat loss from the forearm. Thereason of that could be explained as existence ofthe shoe, which has high thermal resistance. The rise

ARTICLE IN PRESS

Fig. 9. Variations of forearm and foot skin temperature with time


Fig. 8. Variations of heat loss from forearm and foot with time

(Mact ¼ 80W=m2; Ta ¼ T rd ¼ 30 1C, Rcl ¼ 0:5 clo; RH=50%,

V ¼ 0:1m/s).

Fig. 10. Variations of forearm and foot skin wettedness with time



of the latent heat loss from the foot reduces after 18minbecause the skin wettedness of the foot reaches 1, whichis the maximum value (Fig. 10). Fig. 9 shows the skintemperatures of foot and forearm segments. It can beseen that the foot has a higher skin temperature than theforearm. There is not a big difference between theinsulations of a summer shoe and suit shoe. Because ofthis, the temperature differences of foot are not as highas the forearm for 0.5 and 1 clo. But, clothing resistanceof forearm quite differs between the summer clothingand suit, and the difference between these resistancesaffects these segment’s temperatures.Figs. 11–13 illustrate the heat loss, skin temperature

and wettedness at chest and pelvis. The similar situationof forearm and foot can be seen here also. Because thepelvis has more clothing insulation among othersegments, the sensible and latent heat losses are smalland skin temperature and wettedness are high.

Fig. 12. Variations of chest and pelvis skin temperature with time


Fig. 11. Variations of heat loss from chest and pelvis with time

(Mact ¼ 80W=m2; Ta ¼ T rd ¼ 30 1C, Rcl ¼ 0:5 clo, RH=50%,

V ¼ 0:1m/s).

ARTICLE IN PRESS

Fig. 13. Variations of chest and pelvis skin wettedness with time


Fig. 14. Variations of heat loss from whole body with time

(Mact ¼ 80W=m2; Ta ¼ T rd ¼ 30 1C, Rcl ¼ 0:5 clo, RH=50%).

Fig. 15. Variations of average skin temperature with time


Fig. 16. Variations of average skin wettedness with time


Fig. 17. Variations of thermal comfort indices with time



On some segments of the body, some times airmovement may cause undesired local cooling of thehuman body. This effect is called draft and has beenidentified as one of the most annoying factors inindoors. When people sense draft, it often results in ademand for higher air temperatures in the room or forstopping ventilation system. Although the temperatureand humidity are appropriate, people can feel uncom-fortable because of draft effect. For that reason, velocityand direction of air sent to the body are importantparameters for thermal comfort.Figs. 14–17 illustrate the effect of air velocity on

whole body and Figs. 18–23 illustrate the effect of airvelocities locally. In figures clothing insulation 0.5 clo,activity 80W=m2; ambient temperature 30 1C andrelative humidity 0.50 are accepted. As it is seen inFig. 14, with increasing air velocity, the convective heattransfer coefficient (hcv) so does the sensible heat losses

ARTICLE IN PRESS

Fig. 19. Variations of forearm and foot skin temperature with time


Fig. 20. Variation of forearm and foot skin wettedness with time


Fig. 18. Variations of heat loss from forearm and foot with time

(Mact ¼ 80W=m2; Ta ¼ T rd ¼ 30 1C, Rcl ¼ 0:5 clo, RH=50% V ¼

0:30 m/s).

Fig. 22. Variations of chest and pelvis skin temperature with time


Fig. 21. Variation of heat loss from chest and pelvis with time

(Mact ¼ 80W=m2; Ta ¼ T rd ¼ 30 1C, Rcl ¼ 0:5 clo, RH=50%, V ¼

0:30 m/s).

Fig. 23. Variations of chest and pelvis skin wettedness with time



ARTICLE IN PRESSO. Kaynakli, M. Kilic / Building and Environment 40 (2005) 165–174174

raises. In this situation, the average skin temperaturedecreases (Fig. 15) and the body reduces sweat genera-tion. Moreover, increasing the air velocity also increasesthe mass transfer from skin to ambient, so skinwettedness decreases (Fig. 16). The thermal comfortindices approach to neutral conditions by the reductionof both skin temperature and wettedness (Fig. 17).When the body segments are examined, the same

effects can be seen also. The sensible heat losses increasewhile the skin wettedness decreases due to rising of airvelocity. Because of the skin wettedness reduction, theevaporation losses from the skin also decrease.

4. Conclusions

In warm and hot climate countries, some buildingsections (e.g. corridors, lobbies and volumes get directsun light) have higher temperatures than the more easilycontrolled smaller volumes. When people initially beingin thermal comfort enter these regions, their bodiesrespond the changed conditions. Therefore, the archi-tects and the engineers should be considered thesetransient reactions of the body in every phase of thebuilding from design and construction to operation andmaintenance. The purpose of the present study is toprovide a useful tool to calculate the transient thermalconditions of the body. In order to show that the humanbody responds during warm-up period are investigatedin details. The summary of the results are as follows:when entering a high-temperature indoor, the bodyincreases the blood flow to the skin with its controlmechanism, for increasing the heat losses. Since the heatbalance cannot setup with the environment, the bodyactivates the sweat generation mechanism, and the latentheat loss increases by the rising skin wettedness.Especially pelvis and foot, which have more clothing,have the most skin temperature and wettedness. Clothinginsulation has a reducing effect on sensible and latentheat losses but also has an increasing effect on skintemperature and wettedness. As a result, sense of comfortworsens and ambient can be percept as uncomfortable.With the increasing air velocity the convective andevaporative heat transfer coefficients and heat lossesincrease, for this reason the skin temperature becomesslightly lower and the area of wetted skin shrinks.

References

[1] ASHRAE handbook—fundamentals. Atlanta: American Society

of Heating, Refrigeration and Air-Conditioning Engineers, 1989

[chapter 8].

[2] Chaffee EE, Greisheimer EM. Basic physiology and anatomy.

Philadelphia, Montreal: J.B. Lippincott Comp; 1964.

[3] Butera FM. Principles of thermal comfort. Renewable and

Sustainable Energy Reviews 1998;2:39–66 [chapter 3].

[4] Srinavin K, Mohamed S. Thermal environment and construction

workers’ productivity: some evidence from Thailand. Building

and Environment 2003;38:339–45.

[5] Daanen HAM, van de Vliert E, Huang X. Driving performance in

cold, warm, and thermoneutral environments. Applied Ergo-

nomics 2003;34:597–602.

[6] Hoppe P, Martinac I. Indoor climate and air quality. Interna-

tional Journal of Biometeorology 1998;42:1–7.

[7] Fanger PO. Human requirements in future air-conditioning

environments. International Journal of Refrigeration 2001;24:

148–53.

[8] Kaynakli O, Unver U, Kilic M. Evaluating thermal environments

for sitting and standing posture. International Communications in

Heat and Mass Transfer 2003;30(8):1179–88.

[9] Burch SD, Pearson JT, Ramadhyani S. Analysis of passenger

thermal comfort in an automobile under severe winter condition-

ing. ASHRAE Transactions 1991;97:239–46.

[10] Guan Y, Hosni MH, Jones BW, Gielda TP. Investigation of

human thermal comfort under highly transient conditions for

automotive applications-Part 1: experimental design and human

subject testing implementation. ASHRAE Transactions 2003;109:

885–97.

[11] Guan Y, Hosni MH, Jones BW, Gielda TP. Investigation of

human thermal comfort under highly transient conditions for

automotive applications-Part 2: thermal sensation modeling.

ASHRAE Transactions 2003;109:898–907.

[12] Guan Y, Hosni MH, Jones BW, Gielda TP. Literature review of

the advances in thermal comfort modeling. ASHRAE Transac-

tions 2003;109:908–16.

[13] Tanebe S, Arens EA, Bauman FS, Zang H, Madsen TL.

Evaluating thermal environments by using a thermal manikin

with controlled skin surface temperature. ASHRAE Transactions

1994;100(1):39–48.

[14] Fiala D, Lomas KJ, Stohrer M. A computer model of human

thermoregulation for a wide range of environmental conditions:

the passive system. Journal of Applied Physiology

1999;87(5):1957–72.

[15] Gagge AP, Stolwijk JAJ, Nishi Y. An effective temperature scale

based on a simple model of human physiological response.

ASHRAE Transactions 1971;77(Part 1):247–62.

[16] Olesen BW, Hasebe Y, de Dear RJ. Clothing insulation

asymmetry and thermal comfort. ASHRAE Transactions 1988;

94(1):32–51.

[17] McCullough EA, Jones BW, Tamura T. A data base for

determining the evaporative resistance of clothing. ASHRAE

Transactions 1989;95(2):316–28.

[18] de Dear RJ, Arens E, Hui Z, Ogura M. Convective and radiative

heat transfer coefficients for individual human body segments.

International Journal of Biometeorology 1997;40:141–56.

[19] Doherty TJ, Arens E. Evaluation of the physiological bases of

thermal comfort models. ASHRAE Transactions 1988;94(Part 1):

1371–85.

[20] Stolwijk JAJ, Hardy JD. Temperature regulation in man—a

theoretical study. Pflugers Archiv Gesamate Physiology 1966;

291:129–62.

[21] Huizenga C, Hui Z, Arens E. A model of human physiology and

comfort for assessing complex thermal environments. Building

and Environment 2001;36:691–9.

Documents

Investigation of indoor thermal comfort under transient conditions