ASHRAE LV-11-014-2011 A Methodology for the Comprehensive Evaluation of the Indoor Climate Based on Human Body Response-Part 2 1 Hygrothermal Microclimate Evaluation Based on Human.pdf

1、806 ASHRAE TransactionsABSTRACTDiscrepancies inherent in the application of optimal oper-ative temperatures, estimated on the basis of PMV, and theneed to arrive at usable values for the new Czech GovernmentDirective No. 361/2007 Code and the new European StandardprEN 4666:2009 Aerospace Series, air

2、craft integrated airquality and pressure standards, criteria and determinationmethods led to a series of experiments based on the physio-logical human body response to be commissioned. Experi-ments on 32 subjects (university students) enabled thefollowing to be estimated: (1) the total balance of hy

3、grother-mal flows between the human body and the environment and(2) the optimal operative temperature as a function of thesubjects activity and clothing. This, in turn, enables the opti-mal operative temperatures both for air-conditioned and natu-rally ventilated buildings to be established in a nov

4、el andsimple way without the discrepancies inherent in the PMV-based method.INTRODUCTIONThe environment is responsible for over 70% of discom-fort in the workplace, of which the hygrothermal microclimatealone accounts for almost 30% (see the introduction in Part 1of this series). It is evident that

5、the hygrothermal constituentplays a significant role and, therefore, the correct evaluation ofits impact is important.The physical criterion of the interaction of mans physi-ology and the hygrothermal constituent is the product ofenthalpy and specific mass (see Part 1). If specific mass isconstant,

6、enthalpy remains as the sole criterion, and if specificheat is also constant, operative temperature becomes thecriterion.Then operative temperature can be accepted as the crite-rion of hygrothermal microclimate from the point of humanphysiology in an overwhelming number of cases: just in thearea of

7、low and high relative air humidity enthalpy needs to beconsidered (see the section, “The Influence of Humidity”).The optimal operative temperature has up to now beencalculated from the predicted mean value (PMV) (see, e.g.,EN ISO 7730 Moderate Thermal Environment), which is esti-mated on the basis o

8、f a positive reaction from 80% of thepersons in the given environment. The feelings of humanbeings are by definition subjective, impacted by many otherfactors in addition to the hygrothermal conditions, e.g., byinterior colors, a persons mood, etc. Additionally, due to thelaboratory conditions under

9、 which PMV is obtained, it isapproximately valid for the neutral zone only. This has beenconfirmed by experimental measurements (see Fishman andPimbert 1979 and Newsham and Tiller 1995). The furtheraway from the neutral zone, the more the real values departfrom the values calculated from PMV (see Fi

10、gure 1). What ismore, the greater a persons activity, the greater the disparity,thus rendering the resulting values for high activity levelsproblematic.In Figure 2, the mean thermal sensation vote is plottedagainst the operative temperature for a range of velocities.Each point represents the mean vo

11、te of 32 subjects. The corre-lation between the operative temperature and the mean ther-mal sensation vote is high, with a correlation coefficient of0.97 (n = 5). There is no significant difference between thesexes. The solid curve is the regression line for the individualvote (n = 80). For comparis

12、on, the dotted line represents theresults for 172 Japanese subjects in conditions of low airA Methodology for the Comprehensive Evalua-tion of the Indoor Climate Based on Human Body ResponsePart 2.1: Hygrothermal Micro-climate Evaluation Based on Human PhysiologyM.V. Jokl, PhD K. Kabele, PhD F. Jord

13、nMember ASHRAE Associate Member ASHRAEM.V. Jokl is a full-time professor, K. Kabele is department head, and F. Jordn is a post-graduate student in the Department of Microenvi-ronmental and Building Services Engineering, Czech Technical University, Prague, Czechia. LV-11-0142011. American Society of

14、Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions, Volume 117, Part 1. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAES prior written permission.

15、2011 ASHRAE 807Figure 1a Comparison of mean thermal comfort votes(ASHRAE scale) with predictions by the PMVmodel in an English office building (Fishman andPimbert 1979). Activity 80 Wm2(25.35 Btuh1ft2), clothing 0.64 up to 0.82 clo.Figure 1b Comparison of mean thermal comfort votes(ASHRAE scale) wit

16、h predictions by the PMVmodel in a building (Newsham and Tiller 1995).Activity 70 Wm2 (22.18 Btuh1ft2), clothing0.78 0.21 clo.Figure 3 Effect of operative temperature on thermalsensation vote. Activity 1.2 met, clo value resultsfrom neutral temperature 22.8C (73.04F), rh =40%55%, mean radiant temper

17、ature equals airtemperature (Croome et al. 1993).Figure 2 Mean thermal sensation vote versus operativetemperature for Japanese college-age subjects(Tanabe et al. 1987).808 ASHRAE Transactionsmovement reported by Tanabe et al. (1987), and the dashedline represents the calculated PMV values.Of interes

18、t are also results of research conducted at Read-ing University (Croome et al. 1993). These results take intoaccount the opening and closing of doors, i.e., the ventilationrate (see Figure 3).When the windows and the door were closed, the meanthermal sensation tended to be on the warm side of neutra

19、l.When the windows and doors were open, the votes werespread widely over the thermal sensation scale. However, thecalculated PMV values corresponding to the tests were closeto the neutral point for most of the test conditions. Thissuggests that, in this investigation, PMV underestimates thethermal s

20、ensation when the windows and doors are closedthat is, when air change rates are low and undervalues the vari-ation in thermal sensation when air change is significant.This may be due to three main reasons. The first reason isthe assumption of steady-state conditions in the derivation ofthe PMV equa

21、tion. The second is the oversimplified approachto the assessment of the metabolic rate of the subjects.Subjects rarely sit in test chambers for a long period, say onehour, without moving around. The third reason is the sensitiv-ity of PMV to clo values (Croome et al. 1993). It can beconcluded that t

22、he PMV equation overpredicts the neutraltemperature by as much as 2 K (3.6F), and underpredicts thecomfort requirement when air temperature is distant fromneutrality.Humphreys and Nicol (2000)have suggested that theremay be formulaic errors in such a complex index as PMV, withtwo contributing factor

23、s:1. Steady-state approximation. PMV, like other indices ofwarmth, is a steady-state heat exchange equation, and,therefore, its application to the office environment canonly be an approximation. Recent research shows thatamong an office population, the temperature of thefingers varies extensively an

24、d rapidly, indicating that thethermal state of the bodies of office workers is in contin-ual flux (Humphreys and Nicol 1999). This suggests thatit is better to regard the people as soon as being indynamic thermal equilibrium rather than in a steady ther-mal state. By extension, the same is likely to

25、 be true ofother and more varied pursuits. Thus, any index built onsteady-state assumptions is of limited relevance tonormal living. Indices that exclude thermoregulationcannot therefore simulate real-life conditions.2. Inaccurate numerical formulae for steady state. Mostindices have errors in the n

26、umerical values used in theequations, such as the convective and radiant heat-trans-fer coefficients, skin temperature, and sweat rates that areassumed for thermal neutral conditions. These then affectthe final equations. Additionally, there are numericalerrors attributable to conceptual simplificat

27、ions. Forexample, although the calculation of PMV is based oncalculated skin temperature and sweat rate, for conditionsoutside neutral, PMV is based solely on a hypotheticalheat load. This results in the same body thermal statesbeing attributed different PMV values in different envi-ronments (Humphr

28、eys and Nicol 1996). Conceptual andnumerical approximations add to formulae error. As aresult, no thermoregulatory ranges can be estimatedbased on the PMV system.For these reasons, it was decided to estimate optimaloperative temperatures on the basis of the physiologicalresponse of the human organis

29、m.MATHEMATICAL MODEL OF THE PHYSIOLOGICAL BODY RESPONSEFor the thermal neutral zone, the total heat rate productionand its individual components that occurs heat exchangebetween the human body and the environment are shown sche-matically in Figure 4, where qm = M W is the metabolic heat(see Jokl 198

30、9), qresis the components of the heat flow dueto respiration, and qevis the evaporative heat of moisture fromthe skin surface. The heat flow qdryrepresents the heat flowfrom the body through the clothing layer with a total thermalresistance Rt,wa(qdry= qc+ qr). The regulatory process withinthe neutr

31、al zone is achieved mainly by vasodilation and vaso-constriction, changing the bodys internal resistance of thethermoregulatory and adaptation heat flux qtrand qato the skinsurface. Variables qtrand qaare the instantaneous heat fluxFigure 4 Total heat rate production and its distribution inindividua

32、l components during heat exchangebetween the human body and the environment (qmmetabolic heat, qresrespiration heat, qtrthermoregulatory heat, qevevaporative heat, qcconvective heat, qrradiant heat, Rt,watotalthermal resistance of clothing, Rt,itotal internalthermal body resistance, Ctthermal bodyca

33、pacity, Tideep body temperature, Tcorecorebody temperature, Tskskin temperature, Tgglobetemperature).2011 ASHRAE 809regulating the skin temperature during the subjects interac-tion with the environment; qtris the organisms immediateresponse to changes in the microclimate or metabolic heatchanges, an

34、d qais the reaction shift due to adaptation to heatin summer and cold in winter; qtr+ qamay be negative (heatloss) or positive (heat gain). Transient heat flow occurs even inthe thermal neutral zone and is called quasi-stationary, to bedistinguished from flows in the hyperthermia and hypother-mia zo

35、ne.The equation qtr+ qarepresents accumulated heat storageor heat debt. When the body is in a steady-state thermalbalance with the environment, these values are equal to zero.However, we can consider the state of the subject in the neutralzone by non-steady-state conditions due to periodic changesof

36、 the metabolic heat rate, qm, or short thermal excitations intime followed by changes in the internal thermal resistance ofthe body within the neutral zone.The characteristics of each non-steady process are deter-mined, in addition to the thermal resistances Rt,iand Rt,wa, bythe human body heat capa

37、city, Ct. The values characterizingthe heat exchange are: Tsk, Tcore, and Tg. The internal thermalresistance, Rt,i, also determines the changes in thermoregula-tion and the adaptation heat, qtr+ qa, which is necessary formaintaining the skin temperature within physiological valuesif the core tempera

38、ture is to remain constant (Tcore= 36.7C 0.4C = 98.06F 0.72F).The heat flow balance, as presented in the model shownin Figure 4, can be expressed by a thermal flux equation at thesubject-environment boundary. Thus, (if heat conduction isneglected):Wm2; Btuh1ft2where(1)Wm2; Btuh1ft2This equals the qu

39、antity of excreted perceptible butmostly invisible sweat. This was estimated by weighingduring the experiments as a mean value for the whole range.Heat flux within the human body can be represented as(see model in Figure 4)(2)Wm2; Btuh1ft2where Gt,tiis total body thermal conductance, which can beexp

40、ressed by Equation 3.(3)Wm2; Btuh1ft2where Gt,iis the internal thermal conductance and Gt,mismetabolic thermal conductance.The thermoregulatory and adaptational heat flux primar-ily affects the skin temperature, Tsk. The value of the internalthermal resistance, Rt,i= 1/Gt,i, which characterizes the

41、vaso-dilatation and vasoconstriction process, can be calculatedfrom the following equation:m2KW1; hft2FBtu1(4)EXPERIMENTAL DERIVATION OF THE MATHEMATICAL MODEL PARAMETERSAn experiment over the course of several years wasundertaken in a climatic chamber that enabled parameters inEquations 1 and 4 to

42、be derived.The experimental subjects were male university students.Each of them underwent six experiments, lasting approxi-mately three hours at four levels of activity: (1) sitting in achair, (2) sitting on a bike-ergometer without pedaling,(3) pedaling on a bike-ergometer with a 40 W (136.6 Btuh1)

43、load, and (4) pedaling on a bike-ergometer with a load of1Wkg1(1.549 Btuh1lb1) of body mass (for as long thesubject was able to continue). Metabolic heat productionduring each activity was measured by the indirect calorimetricmethod based on CO2concentration measurement in expiredair. Mean skin temp

44、erature, heat rate, and body water loss wereestimated continuously during each experiment.Skin temperature was measured by a special contactmethod described in (Jirk et al. 1975). Body water loss wasestimated by weighing.Two sets of clothing were used by the subjects: light-weight (pajamas) and heav

45、ier clothing (an anti-g suit forfighter pilots). The air temperature and the surface wall temperatureswere kept the same; therefore, it can be assumed that the over-all temperature equals the operative temperature. Six temper-atures were chosen, 29C 3C (84.2F 5.4F) and 14C 3C (57.2F 5.4F), which def

46、ine temperature rangesoutside the neutral zone and where subjects can be expected tobegin sweating or shivering. The originally chosen range oftemperatures, 8C, 11C, 14C, 17C, 20C, 23C, 26C,29C, and 32 C (46.4F, 51.8F, 57.2F, 62.6F, 68F, 73.4F,78.8F, 84.2F, and 89.6F) was found to be excessive andth

47、erefore was reduced.The relative humidity was maintained within the comfortrange corresponding to a partial water vapor pressure from 700to 1850 Pa (0.102 to 0.268 lbfin.2). The onset of sweatingand shivering was always assessed by the same person. Exper-iments were carried out in all seasons of the

48、 year, thus reflect-ing the seasonal adaptation effect on maximal and minimalqdry1Rtwa,- TgTsk()qmqres qev qtrqa+= qiqswqtrqa+()qevqev ins,qev sens,+ qev ins,qsw+=qmqres qev ins, qi=qsw06qm58 14,(),=qmqres qtrqa+ Gtti,TiTsk()1Rtti,- TiTsk()=Gtti,qmqres()TiTsk() qtrqa+()TiTsk()+= Gtm,Gti,+()Rti,TiTsk

49、()qtrqa+()-=810 ASHRAE Transactionsthermoregulatory heat, i.e., it was possible to determine adap-tation heat. However, it became evident that the seasonal adap-tation effect can be neglected (Jokl and Moos 1992), beinglower than 0.2C (0.36F), i.e., within experimental error oftemperature measurement. This is confirmed by otherresearch (Fanger 1970). Measurements were taken when thethermoregulator