Research Article Predicted Thermal Sensation Index for the...

Research ArticlePredicted Thermal Sensation Index for the Hot Environment inthe Spinning Workshop

Rui-Liang Yang1 Lei Liu2 and Yi-De Zhou2

1School of Mechanical Engineering Tianjin Polytechnic University Tianjin 300387 China2School of Energy and Environment Zhongyuan University of Technology Zhengzhou 450007 China

Correspondence should be addressed to Rui-Liang Yang yangruiliang2001sinacom

Received 17 March 2015 Revised 15 June 2015 Accepted 16 June 2015

Academic Editor Jurgita Antucheviciene

Copyright copy 2015 Rui-Liang Yang et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The spinning workshop is the most typical cotton textile workshop in the textile mill and is characterized by the feature of hightemperature all the year To effectively evaluate the general thermal sensation of the textile worker exposed to the hot environmentin the spinning workshop a new heat index named predicted thermal sensation (PTS) index was proposed in this paper The PTSindex based on the heat balance equation can be derived by the empirical equations of air temperature and heat imbalance A one-month-long continuous research was carried out to investigate the actual thermal condition and judge the validity of the PTS indexActual workshop temperatures in the spinning workshop during the measuring period were all above 32∘C belonging to extremehot environmentThe calculated thermal sensation by the PTS index is very close to the actual thermal sensation whichmeans thatthe PTS index can accurately estimate the actual thermal sensation of the textile workers exposed to the hot environment in thespinning workshop Compared to other indices the PTS index can more effectively predict the mean thermal response of a largegroup of textile workers exposed to the hot environment in the spinning workshop

1 Introduction

The spinning workshop is the most typical cotton textileworkshop in the textile mill and is characterized by thefeature of high temperature all the year According to Chinesenational standard ldquocode for design of cotton spinning andweaving factoryrdquo (GB 50481-2009) [1] summer temperatureof the spinning workshop should range from 30∘C to 32∘Cmuch exceeding the acceptable operative temperature rangefrom 23∘C to 26∘C by ISO 7730 [2] In fact the temperatureof the spinning workshop may often be higher than 32∘Cespecially in the summer Obviously higher temperature ofthe spinning workshop can decrease energy consumptionand capitalized cost but results in deteriorating workingconditions and poor thermal comfort Furthermore workingin the spinning workshop with high temperature has physio-logical and psychological effects on workers it reduces theirproductivity and increases their irritability and loss of theirenthusiasm for their work [3]

Evidence about risks in a hot environment and the relatedhealth consequences have increased dramatically in the past

few decades [4] Extreme hot environment in which thetemperature is above 35∘C for living and above 32∘C forworking [5] is prevalent in the spinning workshop Severalmethods have been proposed to estimate the heat stress in anextreme hot environment The wet-bulb globe temperature(WBGT) index [6] predicted heat strain (PHS) model [7]and the predicted mean vote (PMV) index [8] are standardmethods and remain the choice by most researchers TheWBGT index is a composite temperature used to estimatethe effect of temperature humidity and solar radiation onhumans which is regarded as the most accepted indexrepresenting the heat stress to which an individual is exposedin an industrial environment [9] But theWGBT index shouldbe regarded as an exploratory method with the drawback ofbeing longer and more difficult to undertake [6] The mostserious limitation of the WBGT index is that environmentsat a given level of the index are more stressful when theevaporation of sweat is restricted (by high humidity suchas the spinning workshop) than when evaporation is free[10] Thus it is encouraged immediately to define a newindex or method instead of the WGBT index to be used

Hindawi Publishing CorporationMathematical Problems in EngineeringVolume 2015 Article ID 980619 8 pageshttpdxdoiorg1011552015980619

2 Mathematical Problems in Engineering

in an industrial environment [6] The PHS model evaluatesthe thermal stress in the hot climate and determinates themaximum allowable exposure time (such as Dlimtre index)with which the physiological strain is acceptable The PHSmodel only considers standard subjects in good health andfit for the work they perform it is therefore intended tobe used to evaluate working conditions and it does notpredict the physiological response of individual subjects [7]Although PHS can evaluate the exposure limit for varioussituations it has a limitation when considering the cases inwhich humans exercise moderately [11] such as the workin the spinning workshop The PMV index based on theheat balance of the human body can be used to predict thegeneral thermal sensation and degree of discomfort of peopleexposed to moderate thermal environments and it shouldbe used only for values of PMV between minus2 and +2 andwhen the main parameters are within the specified rangesuch as air temperature between 10∘C and 30∘C [2] Exceptfor three standard methods there are a number of indicesthat have been proposed to measure the heat stress in the hotenvironment such as the equivalent temperature (ET) index[12] the temperature-humidity index (THI) [13] and theenvironmental stress index (ESI) [14] But these indices aremostly constructed based on several simple environmentalvariables not including the personal variables and com-prehensive environmental information which makes theseindices unreliable and ambiguous in the special environmentsuch as the spinning workshop Furthermore most indicesexcept the PMV index [2 8] are used to evaluate the thermalcondition in the hot environment instead of predicting thephysiological response of individual subjects

The textile industry plays an irreplaceable role in the Chi-nese economy [15] and poor workshop environment in thespinning workshop is particularly important to the health ofworkers [16] but there is no appropriate index used to predictthe general thermal sensation of the textile worker nowadaysTo effectively evaluate the general thermal sensation of thetextileworker exposed to the hot environment in the spinningworkshop a heat index named predicted thermal sensation(PTS) index was proposed in this paper The PTS indexan objective index based on the heat balance equation caneffectively predict themean thermal response of a large groupof textile workers exposed to the hot environment in thespinning workshop

2 Model

The thermal balance equation of the body may be written as[17]

119872 minus 119882 = (119862 + 119877 + 119864sk) + (119862res + 119864res) + 119878 (1)

The sensible heat loss from skin (119862 + 119877) describing theheat exchanges between the clothing and the environment isestimated by [7]

119862 + 119877 = 119891cl times [ℎcdyn times (119905cl minus 119905

119886) + 396times 10minus8

times (119905cl + 273)

4minus (119905

119903+ 273)

4]

(2)

where the clothing area factor 119891cl may be estimated from thefollowing equation [18]

119891cl = 1+ 028119868cl (3)

The dynamic convective heat exchange ℎcdyn can beestimated as [7]

ℎcdyn = max 238 1003816

1003816

1003816

1003816

119905sk minus 119905

119900

1003816

1003816

1003816

1003816

025 35+ 52V

119886 87V119886

06 (4)

The sensible heat loss from skin (119862 + 119877) also describingthe heat exchanges between the skin and the clothing surfaceis estimated by [7]

119862 + 119877 =

119905sk minus 119905cl119868cldyn

(5)

where dynamic clothing insulation 119868cldyn can be derived as[7]

119868cldyn = 119868totdyn minus

119868adyn

119891cl (6)

where

119868totdyn = 119862orrtot times (119868cl +

119868ast119891cl

)

119868adyn = 119862orr119868119886 times 119868ast

(7)

For 119868cl ge 06 clo

119862orrtot = 119862orrcl = 119890

0043minus0398V119886+0066V

119886

2minus0378V

119908+0094V

119908

2

(8)

For nude person (119868cl = 0 clo)

119862orrtot = 119862orr119868119886 = 119890

minus0472V119886+0047V

119886

2minus0342V

119908+0117V

119908

2

(9)

For 0 le 119868cl le 06 clo

119862orrtot =

(06 minus 119868cl) 119862orr119868119886 + 119868cl times 119862orrcl

06(10)

with 119862orrtot limited to 1 V119886limited to 3ms and V

119908limited

to 15ms 119868ast is the static boundary layer thermal insulation(= 07 clo) [18]

In the hot environment the workerrsquos body finally reachessteady state [7 11] and the steady state mean skin temperature119905sk can be estimated as a function of the parameters of theworking situation using the following empirical expressions[7]

Mathematical Problems in Engineering 3

119905sk =

119905sknu for 119868cl le 02 clo

119905skcl for 119868cl ge 06 clo

119905sknu + 25 times (119905skcl minus 119905sknu) times (119868cl minus 02) for 02 clo lt 119868cl lt 06 clo

119905sknu = 719+ 0064119905

119886+ 0061119905

119903minus 0348V

119886+ 0198119901

119886+ 0616119905co

119905skcl = 1217+ 0020119905

119886+ 0044119905

119903minus 0253V

119886+ 0194119901

119886+ 0005346119872 + 051274119905co

(11)

The actual evaporation rate 119864sk is given by [19]

119864sk =

120582119878

119903

120582119878

119903

119864maxlt 046

120582119878

119903exp[minus04127 times (

18120582119878

119903

119864maxminus 046)

1168] 046 le

120582119878

119903

119864maxle 17

119864max120582119878

119903

119864maxgt 17

(12)

where 120582 is the latent heat of evaporation of sweat =657Wsdothrkg at 30∘C Sweat rate 119878

119903is a function of the

thermoregulatory signal and can be adequately described by[19]

119878

119903= 042

+ 044 tanh [116times (01119905sk + 09119905co minus 374)]

(13)

The maximum evaporative heat flow at the surface isgiven by [7]

119864max

=

038 times (119901sk minus 119901

119886) times (26119862orrtot

2minus 65119862orrtot + 49)

167 times 119862orrtot times (119868cl + 119868ast119891cl)

(14)

The saturated water vapor pressure at skin temperature119901sk can be estimated as a function of the skin temperature 119905sk

The heat transfer from the deep body core to the skin 119867

can be expressed as [19]

119867 = 84+ 72times tanh [13times (01119905sk + 09119905co minus 379)]

times (119905co minus 119905sk)

(15)

For a heat balance in the body heat flow core to skinequals heat flow skin to environment

119867 = 119864sk + 119862 + 119877 (16)

If 119905

119886 119905

119903 119901

119886 119872 V

119886 V119908 and 119868cl are known all terms

in Expressions (2)sim(16) including 119867 and 119905co can be solvediteratively by Expressions (2)sim(16)

The heat flow by respiratory convective 119862res can beestimated by the following empirical expression [7]

119862res = 000152119872 (2856+ 0885119905

119886+ 0641119901

119886) (17)

The heat flow by respiratory evaporative 119864res can beestimated by the following empirical expression [7]

119864res = 000127119872 (5934+ 053119905

119886minus 1163119901

119886) (18)

Taking Expressions (5) (12) (17) and (18) into Expression(1) yields

119878 = 119872 minus 119882 minus (119862 + 119877 + 119864sk) minus (119862res + 119864res) (19)

The heat storage 119878 is solved as the difference betweeninternal heat production and heat loss to the actual environ-ment at the steady state in the hot environment for a personhypothetically kept at the empirical equations of 119905sk 119878

119903

and 119867 In most industrial situations including the spinningworkshop the effective mechanical power 119882 is small and canbe neglected [7] Tomore effectively predict themean thermalresponse of a large group of textile workers exposed to thehot environment in the spinning workshop the relationshipof heat storage 119878 and TSV value was researched by linearanalysis based on a large number of previous experimentsThen a new heat index named predicted thermal sensation(PTS) index was proposed as follows

PTS = (00025119905

119886minus 00657)

times [119872 minus (119862 + 119877 + 119864sk) minus (119862res + 119864res)]

(20)

The PTS index was derived by the empirical equationsof air temperature and heat imbalance between internal heatproduction and heat loss to the actual environment at thesteady state in the hot environment Similarly to the PMVindex the PTS index can predict the mean thermal sensationof a large group of people on the seven-point thermalsensation scale The difference is that the PTS index wasproposed to be used in the hot environment in the spinning


Table 1 Anthropometric data of subjects

Gender Number Seniority(years)

Height(cm)

Weight(kg)

Male 310 203 plusmn 89a 1712 plusmn 72 711 plusmn 75Female 513 181 plusmn 86 1601 plusmn 62 606 plusmn 76Total 823 190 plusmn 88 1643 plusmn 85 645 plusmn 91aStandard deviation

workshop but the PMV index cannot be used to the hotenvironment in the spinning workshop due to temperatureabove 30∘C

3 Experiment

To investigate the actual thermal condition in the spinningworkshop and judge the validity of the PTS index a one-month-long continuous research was carried out in thespinning workshop of Zhengzhou Hongye Textile Co Ltdone of the largest cotton companies in Henan Province (thecentral part of China the most populous province with over103 million people) Experiments were conducted from July1 to July 31 of 2014 in the spinning workshop with area of4985m2 The selected workers with years of work experience(see Table 1) were the most typical representative of Chinesetextileworkers All investigated subjects recommended by theworkshop director have more than 2-year work experienceand were responsible for their work which ensures that theinvestigated subjects fully adapt to the thermal environmentof the spinning workshop Front-line workers with 23 ofdayshifts and 13 of nightshifts were chosen in the surveyAtypical workers such as those with less cohesive strengthor bad work were excluded from this survey to ensurethat participators are typical representative Participatingworkers were investigated near their workstations during theexperimental process 823 sets of data were collected in thisexperiment with about 20 to 40 sets of data in one day

The PTS index was deduced by four physical variables(temperature 119905

119886 air velocity V

119886 mean radiant temperature

119905

119903 and relative humidity RH) and three personal variables

(clothing insulation 119868cl activity level 119872 and walking speedV119908) Temperature (plusmn05∘C for 0sim400∘C) relative humid-

ity (plusmn3 for 10 sim95) air velocity (plusmn002ms for 0sim

099ms plusmn3 FS for 1sim5ms) and globe temperature (plusmn1∘Cfor 0sim80∘C) were measured by using the laboratory-gradeinstruments Mean radiant temperature was calculated bytemperature air velocity and global temperature accordingto ISO 7726 [20] Measurements for workers were madein workstations where workers were known to spend theirtime [8] The measuring positions were selected to be closeto the participant within a distance of 02m and at threeheights (01m 11m and 17m) Clothing values adoptedgarment insulation values from ISO9920 [18] A time-averagemetabolic rate [2 8] for the worker with activities wasused since the workerrsquos activity consists of a combination ofworkinvestigation periods Workerrsquos miscellaneous occupa-tional activities should be classified as ldquolight machine workrdquo

while investigation activities should be classified as ldquostandingrelaxedrdquo Thus every worker who typically spent 50 minutesout of each hour ldquolight machine workrdquo with metabolic rate of128Wm2 and 10 minutes ldquostanding relaxedrdquo with metabolicrate of 70Wm2 had an average metabolic rate of 128 times

5060 + 70 times 1060 = 118Wm2 119901

119886was estimated by the

air temperature 119905

119886and relative humidity RH Due to the work

characteristics of the investigated workers the walking speedis supposed to be 05ms Once four physical variables andthree personal variables were determined the PTS index canbe calculated by Expression (20)

Analogously the PHS model can be solved by four phys-ical variables (temperature 119905


119886 mean radiant

temperature 119905

119903 and relative humidity RH) and five personal

variables (clothing insulation 119868cl activity level 119872 walkingspeed V

119908 weight and height) [7] The PMV index can be

obtained by temperature 119905


119886 mean radiant

temperature 119905

119903 relative humidity RH clothing insulation 119868cl

and activity level 119872 [2 8] The WGBT index can be esti-mated by temperature 119905

119886 globe temperature 119905

119892 and relative

humidity RH [6] Because the spinning workshop belongs toindoor hot and humid environments solar radiation term inthe ESI index can be neglected [12] Equivalent temperature(ET) [12] the temperature-humidity index (THI) [13] andthe environmental stress index (ESI) [14] were all obtainedby the temperature 119905

119886and relative humidity RH The Actual

Mean Vote (AMV) was obtained by thermal sensation voterecorded on the ASHRAE seven-point scale [8] during thesurvey

4 Results and Discussion

41 Outdoor andWorkshop Temperature during theMeasuringPeriod To investigate actual air temperature in the spinningworkshop a one-month-long continuous monitoring wascarried out by using the laboratory-grade instruments witheight orsquoclock in the morning and two orsquoclock in the afternoonfrom July 1 to July 31 of 2014 and five measured points weredistributed evenly in the spinning workshop The averagetemperature of five measured points was used as the work-shop temperature The outdoor temperature was obtainedfrom local meteorological records

Figure 1 shows the outdoor temperature and workshoptemperature during the measuring period (ie from July 1 toJuly 31 2014) respectively It can be found from Figure 1 thatthe workshop temperatures were all above 32∘C exceedingthe acceptable operative temperature range from 23∘C to26∘C by ISO 7730 [5] required temperature range from30∘C to 32∘C by GB 50481-2009 and upper limit 30∘C ofPMV application range Thus the workshop environmentin the spinning workshop during the measuring periodbelongs to extreme hot environment [5] Due to the risksin hot environment and related health consequences itis necessary to present an objective evaluation instead ofsubjective evaluation of thermal sensation for the textileworker exposed to the hot environment in the spinningworkshopThe PTS index was an appropriate index to predictthe thermal sensation for the textile work which is helpful


Table 2 Measured parameters around the textile worker

Gender Male(119899 = 310)

Female(119899 = 513)

Total(119899 = 823)

Temperature 119905

119886

(∘C) 339 plusmn 10a 341 plusmn 10 340 plusmn 10Air velocity V

119886

(ms) 042 plusmn 023 042 plusmn 022 042 plusmn 022Mean radianttemperature 119905

119903

(∘C) 340 plusmn 17 340 plusmn 18 340 plusmn 18

Relative humidity RH() 592 plusmn 76 601 plusmn 77 598 plusmn 77

Clothing insulation 119868cl(clo) 047 plusmn 003 047 plusmn 002 047 plusmn 003aStandard deviation

Acceptable operative temperature range by ISO7730

Workshop temperature (at 8 am)Workshop temperature (at 2 pm)Outdoor temperature (at 8 am)Outdoor temperature (at 2 pm)

Required temperature range by GB 50481-2009

40

35

25

20

30

20140701 20140711 20140721 20140731

(∘C)

Figure 1 Outdoor temperature and mean workshop temperatureduring the measuring period

for taking effective strategies to prevent the health risk to theworker

42 Comparison of the PTS and the ActualThermal SensationTable 2 shows the measured parameters around the textileworker during the measuring period which were used toderive the PTS index Figure 2 shows the actual thermalsensation (AMV) against the PTS index The PTS valuewas obtained by Expression (20) representing the calculatedthermal sensation of the worker while the AMV value wasobtained by thermal sensation vote record during the surveyrepresenting the actual thermal sensation of the workerMostof the AMV values were 1 (denoting ldquoslightly warmrdquo) and 2(denoting ldquowarmrdquo) In Figure 2 a trend line is shown with thecorresponding 119877

2 value (119899 = 823 119901 lt 0001) representingAMV changes with PTS The dotted line in Figure 2 showsPTS = AMV so ideally all values would be on this line Thereality is that calculated thermal sensation is very close to theactual thermal sensation

AMVLinear (AMV)

3

25

2

15

1

05

0 12 14 16PTS

18 2

AM

V

PTS = AMV

AMV = 09132 PTS + 00348 R2 = 03634

Figure 2 AMV versus PTS

PTSAMV

Linear (PTS)Linear (AMV)

35

25

3

2

PTS

AM

V

1

032 33 34

15

05

35 36to (∘C)

AMV = 01792to minus 46385 R2 = 03411PTS = 01867to minus 47931 R2 = 08930

Figure 3 PTSAMV versus operative temperature 119905

119900

Figure 3 shows the PTSAMV against the operative tem-perature 119905

119900The operative temperature 119905

119900is the common tem-

perature in the thermal research field and can be solved by thetemperature 119905


119886 andmean radiant temperature

119905

119903[2 8] There are two trend lines with corresponding 119877

2

value in Figure 3 representing PTSAMV changes with theoperative temperature 119905

119900 Two trend lines (119899 = 823 119901 lt

0001) are very close which means that calculated thermalsensation is very close to the actual thermal sensation Thefact that the PTS index is very close to the actual thermalsensation means that the PTS index can accurately estimatethe actual thermal sensation of the textile workers in thespinning workshop


2

22

18

16

14

12

27 28 29 30 31 32 33

PTS

PTS = 01349 WGBT minus 23912

R2 = 07977p lt 0001

WGBT (∘C)

Figure 4 PTS versus WGBT

21

300Mean Dlimtre (min)

Mea

n PT

S

320 340 360 380 400 420 440 460 480

2

19

18

17

16

15

14

13

PTS = minus00035 Dlimtre + 31572

R2 = 07212p lt 0001

Figure 5 Mean PTS versus mean Dlimtre of each day during themeasuring period

43 Comparison of the PTS Index and Other Indices In orderto test the validity of this new index the PTS index iscompared with the commonly used indices (WBGT [6] andDlimtre [7]) in these experiments TheWBGT index and thePHSmodel should be used for evaluating working conditionsinstead of predicting the physiological response of individualsubjects However due to the lack of appropriate referenceindex here the WGBT value and the Dlimtre index in thePHSmodel were used as the reference object to compare withthe PTS index The analysis between PTS and WBGT valueis presented in Figure 4 for correlation Dlimtre representsthe maximum allowable exposure time for heat storage inPHS model [7] and mean Dlimtre of each day during themeasuring period was calculated to compare with the meanPTS in Figure 5 The linear regression equations and thebivariate correlation results calculated by SPSS software arealso shown in Figures 4 and 5 The correlations between PTSand WBGT (119899 = 823 119901 lt 0001) and mean PTS and meanDlimtre (119899 = 31 119901 lt 0001) are statistically significant

20140701 20140711 20140721 20140731

8

7

6

5

4

3

2

1

0

minus1

Mean PTSMean AMVMean WGBT (+28∘C)

Mean ET (Mean ESI (Mean THI (

+275∘C)+29∘C)+295∘C)

Mean PMVMean Dlimtre (times150min)

Figure 6 Comparison of mean PTS and other indices in each dayduring the measuring period PTS (20) AMV thermal sensationvote WGBT 07119905

119908

+ 03119905

119892

[6] ET 038119905

119886

+ 063119905

119892

[12] Dlimtremaximum allowable exposure time for heat storage in PHS model[7] PMV PMV index [2 8] ESI 063119905

119886

minus003RH+00054(119905

119886

sdotRH)minus

073 [14] THI 119905

119886

minus (055 minus 00055RH) times (119905

119886

minus 145) [13]

Therefore the PTS (mean PTS) index is linearly related to theWBGT (mean Dlimtre) index

Figure 6 shows comparison of mean PTS index and otherindices in each day during the monitoring period It can beseen from Figure 6 that the mean PTS index is much closerto the mean actual thermal sensation than other indicesDlimtre [7] ET [12] ESI [14] and THI [13] may be used toevaluate the thermal condition in the hot environment butthey cannot be used to predict the physiological response ofindividual subjects The mean PMV index much exceededthe valid PMV range of minus2 to 2 in each day meaning a largeamount of thermal dissatisfied people which is not a factaccording to the AMV Thus compared to other indices thePTS index can more effectively predict the mean thermalresponse of a large group of textile workers exposed to thehot environment in the spinning workshop

44 Nonthermal Factors Figure 7 shows AMV versus PTS ofdifferent gender (female 119899 = 513 male 119899 = 310) Thereare 4 287 199 and 23 female workers voting 0 1 2 and 3 inthe AMV inquiry respectively while there are 3 181 115 and11 male workers in the AMV inquiry The results show thatfemale worker and male worker have almost the same PTSand the actual thermal sensation There are two trend lineswith corresponding 119877

2 value in Figure 7 representing AMVof different genders change with the PTS Two trend lines areboth very close to the line of PTS = AMV which means thatcalculated PTS values of different genders are both close tothe actual thermal sensation


FemaleMaleLinear (F)

Linear (M)

PTS

AM

V

3

25

2

15

1

05

012 14 16 18 222

PTS = AMV

AMV (F) = 09007 PTS + 00584 R2 = 03565AMV (M) = 09310 PTS + 00009 R2 = 03724

Figure 7 AMV versus PTS of different gender

0 5 10 15Seniority

20 25 30 35

PTS

24

22

2

18

16

14

12

1

PTS (F) = 00006 seniority + 15568R2 = 00205 p = 06437PTS (M) = minus00018 seniority + 15745

R2 = 00705 p = 02159

FemaleMale

Linear (female)Linear (male)

Figure 8 The PTS index of different gender versus seniority

Figure 8 shows that the PTS index of the worker changeswith workerrsquos seniority No significant differences (female119899 = 513 119901 = 06437 male 119899 = 310 119901 = 02159) wereobserved in PTS following the seniority whichmeans that thethermal sensation of the textile worker has little relationshipwith the seniority Reference [17] points that the young andold people are equally sensitive to cold or heat which isconfirmed with this conclusion

5 Conclusions

Thepredicted thermal sensation (PTS) indexwas proposed topredict the mean thermal response of a large group of textile

workers exposed to the hot environment in the spinningworkshop Actual workshop temperatures in the spinningworkshop during the measuring period were all above 32∘Cexceeding the acceptable operative temperature range from23∘C to 26∘C by ISO 7730 and required temperature rangefrom 30∘C to 32∘C by GB 50481-2009 belonging to extremehot environment

Higher temperature of the cotton textile workshop mayresult in deteriorating working conditions and poor thermalcomfort The PTS index was an appropriate index to predictthe thermal sensation for the textile work which is helpfulfor taking effective strategies to prevent the health risk tothe worker Comparison of the PTS index and the AMVshows that the PTS index is very close to the actual thermalsensation which means that the PTS index can accuratelyestimate the actual thermal sensation of the textile workersexposed to the hot environment in the spinning workshopCompared to other indices the PTS index can more effec-tively predict the mean thermal response of a large group oftextile workers according to the ASHRAE thermal sensationscale Furthermore the calculated PTS values of differentgenders are both very close to the actual thermal sensationNo significant differences were observed in PTS followingthe seniority which means that the thermal sensation of thetextile worker has little relationship with the seniority

Nomenclature

119862 Convective heat loss from skin (Wm2)119862orrcl Correction for the dynamic total dry

thermal insulation at or above 06 clo(dimensionless)

119862orr119868119886 Correction for the dynamic total drythermal insulation at 0 clo (dimensionless)

119862orrtot Correction for the dynamic clothinginsulation as a function of thedimensionless actual clothing(dimensionless)

119862res Heat flow by respiratory convection(Wm2)

119864max Maximum evaporative heat flow at theskin surface (Wm2)

119864res Heat flow by respiratory evaporative(Wm2)

119864sk Total rate of evaporative heat loss fromskin (Wm2)

119891cl Clothing area factor (dimensionless)119867 Heat transfer from the deep body core to

the skin (Wm2)ℎcdyn Dynamic convective heat exchange

(W(m2sdotK))119868ast Static boundary layer thermal insulation

(= 07 clo)119868adyn Dynamic boundary layer thermal

insulation119868cl Static clothing insulation (clo)119868cldyn Dynamic clothing insulation (clo)119868totdyn Total dynamic clothing insulation (clo)


119872 Activity level (Wm2)119901

119886 Water vapor partial pressure (Pa)

119901sk Saturated water vapor pressure at skintemperature (Pa)

119877 Radiative heat loss from skin (Wm2)RH Relative humidity ()119878 Heat storage (Wm2)119878

119903 Sweat rate (kg(m2sdothr))

119905

119886 Air temperature (∘C)

119905cl Clothing surface temperature (∘C)119905co Core temperature (∘C)119905

119892 Globe temperature (∘C)

119905

119900 Operative temperature (∘C)

119905

119903 Mean radiant temperature (∘C)

119905sk Temperature of skin compartment (∘C)119905sknu Steady state mean skin temperature for nude

subject (∘C)119905skcl Steady state mean skin temperature for

clothed subject (∘C)119905

119908 Wet-bulb temperature (∘C)

V119886 Air velocity (ms)

V119908 Walking speed (ms)

119882 Effective mechanical power (Wm2)120582 Latent heat of evaporation of sweat

657Wsdothrkg at 30∘C (Wsdothrkg)

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This research was supported by the NSFC (the NaturalScience Foundation of China) no 51208527 and FundingScheme for Young Teachers of Higher School in HenanProvince (2012GGJS-124)

References

[1] GB 50481 ldquoCode for design of cotton design spinning andweaving factoryrdquo 2009

[2] ISO ldquoErgonomics of the thermal environmentmdashanalyticaldetermination and interpretation of thermal comfort usingcalculation of the PMV and PPD indices and local thermalcomfort criteriardquo ISO 7730 2005

[3] J Zhao N Zhu and S Lu ldquoProductivity model in hot andhumid environment based on heat tolerance time analysisrdquoBuilding and Environment vol 44 no 11 pp 2202ndash2207 2009

[4] M Ilangkumaran M Karthikeyan T Ramachandran MBoopathiraja and B Kirubakaran ldquoRisk analysis and warningrate of hot environment for foundry industry using hybridMCDM techniquerdquo Safety Science vol 72 pp 133ndash143 2015

[5] Z Tian N Zhu G Zheng and HWei ldquoExperimental study onphysiological and psychological effects of heat acclimatizationin extreme hot environmentsrdquo Building and Environment vol46 no 10 pp 2033ndash2041 2011

[6] ISO ldquoHot environmentsmdashestimation of the heat stress onworking man based on the WBGT-index (wet bulb globetemperature)rdquo ISO 7243 1989

[7] ISO ldquoErgonomics of the thermal environmentmdashanalyticaldetermination and interpretation of heat stress using calcula-tion of the predicted heat strainrdquo ISO 7933 2004

[8] ANSIASHRAE Standard 55 ldquoThermal environment condi-tions for human occupancyrdquo 2013

[9] R Kralikovaa H Sokolovaa and EWessely ldquoThermal environ-ment evaluation according to indices in industrial workplacesrdquoProcedia Engineering vol 69 pp 158ndash167 2014

[10] G M Budd ldquoWet-bulb globe temperature (WBGT)-its historyand its limitationsrdquo Journal of Science andMedicine in Sport vol11 no 1 pp 20ndash32 2008

[11] R Ooka Y Minami T Sakoi K Tsuzuki and H B RijalldquoImprovement of the sweating model in 2-node model and itsapplication to thermal safety for hot environmentrdquoBuilding andEnvironment vol 45 no 7 pp 1565ndash1573 2010

[12] C Liang G Zheng N Zhu Z Tian S Lu and Y ChenldquoA new environmental heat stress index for indoor hot andhumid environments based on Cox regressionrdquo Building andEnvironment vol 46 no 12 pp 2472ndash2479 2011

[13] J Unger ldquoComparisons of urban and rural bioclimatologicalconditions in the case of a Central-European cityrdquo InternationalJournal of Biometeorology vol 43 no 3 pp 139ndash144 1999

[14] D S Moran K B Pandolf Y Shapiro et al ldquoAn environmentalstress index (ESI) as a substitute for the wet bulb globetemperature (WBGT)rdquo Journal of Thermal Biology vol 26 no4-5 pp 427ndash431 2001

[15] J Ruan and X Zhang ldquoldquoFlying geeserdquo in China The textileand apparel industryrsquos pattern of migrationrdquo Journal of AsianEconomics vol 34 pp 79ndash91 2014

[16] R Yang L Liu and Z Long ldquoResearch on workshop environ-ment in the textile company using analytic hierarchy processrdquoEnergy Education Science andTechnology vol 33 no 3 pp 1581ndash1594 2015

[17] ASHRE Handbook-Fundamental American Society of HeatingRefrigerating and Air-Conditioning Engine 2009

[18] ISO ldquoEstimation of thermal insulation and water vapourresistance of a clothing ensemblerdquo ISO 9920 2007

[19] C H Wyndham and A R Atkins ldquoA physiological schemeand mathematical model of temperature regulation in manrdquoPflugers Archiv European Journal of Physiology vol 303 no 1pp 14ndash30 1968

[20] International Organization for Standardization (ISO) ISO2276 Ergonomics of the Thermal EnvironmentmdashInstruments forMeasuring Physical Quantities International Organization forStandardization (ISO) London UK 1998

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MathematicsJournal of


Mathematical Problems in Engineering

Hindawi Publishing Corporationhttpwwwhindawicom

Differential EquationsInternational Journal of

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Applied MathematicsJournal of


Probability and StatisticsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of


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Complex AnalysisJournal of


OptimizationJournal of


CombinatoricsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of


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Journal of


Function Spaces

Abstract and Applied AnalysisHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of Mathematics and Mathematical Sciences


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Algebra

Discrete Dynamics in Nature and Society



Decision SciencesAdvances in

Discrete MathematicsJournal of


Volume 2014 Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Stochastic AnalysisInternational Journal of


in an industrial environment [6] The PHS model evaluatesthe thermal stress in the hot climate and determinates themaximum allowable exposure time (such as Dlimtre index)with which the physiological strain is acceptable The PHSmodel only considers standard subjects in good health andfit for the work they perform it is therefore intended tobe used to evaluate working conditions and it does notpredict the physiological response of individual subjects [7]Although PHS can evaluate the exposure limit for varioussituations it has a limitation when considering the cases inwhich humans exercise moderately [11] such as the workin the spinning workshop The PMV index based on theheat balance of the human body can be used to predict thegeneral thermal sensation and degree of discomfort of peopleexposed to moderate thermal environments and it shouldbe used only for values of PMV between minus2 and +2 andwhen the main parameters are within the specified rangesuch as air temperature between 10∘C and 30∘C [2] Exceptfor three standard methods there are a number of indicesthat have been proposed to measure the heat stress in the hotenvironment such as the equivalent temperature (ET) index[12] the temperature-humidity index (THI) [13] and theenvironmental stress index (ESI) [14] But these indices aremostly constructed based on several simple environmentalvariables not including the personal variables and com-prehensive environmental information which makes theseindices unreliable and ambiguous in the special environmentsuch as the spinning workshop Furthermore most indicesexcept the PMV index [2 8] are used to evaluate the thermalcondition in the hot environment instead of predicting thephysiological response of individual subjects

The textile industry plays an irreplaceable role in the Chi-nese economy [15] and poor workshop environment in thespinning workshop is particularly important to the health ofworkers [16] but there is no appropriate index used to predictthe general thermal sensation of the textile worker nowadaysTo effectively evaluate the general thermal sensation of thetextileworker exposed to the hot environment in the spinningworkshop a heat index named predicted thermal sensation(PTS) index was proposed in this paper The PTS indexan objective index based on the heat balance equation caneffectively predict themean thermal response of a large groupof textile workers exposed to the hot environment in thespinning workshop

2 Model

The thermal balance equation of the body may be written as[17]

119872 minus 119882 = (119862 + 119877 + 119864sk) + (119862res + 119864res) + 119878 (1)

The sensible heat loss from skin (119862 + 119877) describing theheat exchanges between the clothing and the environment isestimated by [7]

119862 + 119877 = 119891cl times [ℎcdyn times (119905cl minus 119905

119886) + 396times 10minus8

times (119905cl + 273)

4minus (119905

119903+ 273)

4]

(2)

where the clothing area factor 119891cl may be estimated from thefollowing equation [18]

119891cl = 1+ 028119868cl (3)

The dynamic convective heat exchange ℎcdyn can beestimated as [7]

ℎcdyn = max 238 1003816

1003816

1003816

1003816

119905sk minus 119905

119900

1003816

1003816

1003816

1003816

025 35+ 52V

119886 87V119886

06 (4)

The sensible heat loss from skin (119862 + 119877) also describingthe heat exchanges between the skin and the clothing surfaceis estimated by [7]

119862 + 119877 =

119905sk minus 119905cl119868cldyn

(5)

where dynamic clothing insulation 119868cldyn can be derived as[7]

119868cldyn = 119868totdyn minus

119868adyn

119891cl (6)

where

119868totdyn = 119862orrtot times (119868cl +

119868ast119891cl

)

119868adyn = 119862orr119868119886 times 119868ast

(7)

For 119868cl ge 06 clo

119862orrtot = 119862orrcl = 119890

0043minus0398V119886+0066V

119886

2minus0378V

119908+0094V

119908

2

(8)

For nude person (119868cl = 0 clo)

119862orrtot = 119862orr119868119886 = 119890

minus0472V119886+0047V

119886

2minus0342V

119908+0117V

119908

2

(9)

For 0 le 119868cl le 06 clo

119862orrtot =

(06 minus 119868cl) 119862orr119868119886 + 119868cl times 119862orrcl

06(10)

with 119862orrtot limited to 1 V119886limited to 3ms and V

119908limited

to 15ms 119868ast is the static boundary layer thermal insulation(= 07 clo) [18]

In the hot environment the workerrsquos body finally reachessteady state [7 11] and the steady state mean skin temperature119905sk can be estimated as a function of the parameters of theworking situation using the following empirical expressions[7]


119905sk =




119905sknu = 719+ 0064119905

119886+ 0061119905

119903minus 0348V

119886+ 0198119901

119886+ 0616119905co

119905skcl = 1217+ 0020119905

119886+ 0044119905

119903minus 0253V

119886+ 0194119901

119886+ 0005346119872 + 051274119905co

(11)


119864sk =

120582119878

119903

120582119878

119903

119864maxlt 046

120582119878


18120582119878

119903

119864maxminus 046)

1168] 046 le

120582119878

119903

119864maxle 17

119864max120582119878

119903

119864maxgt 17

(12)




119878

119903= 042


(13)


119864max

=

038 times (119901sk minus 119901

119886) times (26119862orrtot



(14)






(15)


119867 = 119864sk + 119862 + 119877 (16)

If 119905

119886 119905

119903 119901

119886 119872 V




119862res = 000152119872 (2856+ 0885119905

119886+ 0641119901

119886) (17)


119864res = 000127119872 (5934+ 053119905

119886minus 1163119901

119886) (18)




119903


PTS = (00025119905

119886minus 00657)


(20)





Height(cm)

Weight(kg)



3 Experiment





119905






5060 + 70 times 1060 = 118Wm2 119901







119886 mean radiant

temperature 119905






119886 mean radiant

temperature 119905




119892 and relative










Female(119899 = 513)

Total(119899 = 823)

Temperature 119905

119886


119886


119903







40

35

25

20

30

20140701 20140711 20140721 20140731

(∘C)





AMVLinear (AMV)

3

25

2

15

1

05

0 12 14 16PTS

18 2

AM

V

PTS = AMV

AMV = 09132 PTS + 00348 R2 = 03634


PTSAMV


35

25

3

2

PTS

AM

V

1

032 33 34

15

05

35 36to (∘C)



119900







119905


2





2

22

18

16

14

12

27 28 29 30 31 32 33

PTS


R2 = 07977p lt 0001

WGBT (∘C)


21


Mea

n PT

S

320 340 360 380 400 420 440 460 480

2

19

18

17

16

15

14

13


R2 = 07212p lt 0001



20140701 20140711 20140721 20140731

8

7

6

5

4

3

2

1

0

minus1



+275∘C)+29∘C)+295∘C)



119908

+ 03119905

119892

[6] ET 038119905

119886

+ 063119905

119892


119886

minus003RH+00054(119905

119886

sdotRH)minus

073 [14] THI 119905

119886


119886

minus 145) [13]







Linear (M)

PTS

AM

V

3

25

2

15

1

05

012 14 16 18 222

PTS = AMV



0 5 10 15Seniority

20 25 30 35

PTS

24

22

2

18

16

14

12

1


R2 = 00705 p = 02159

FemaleMale




5 Conclusions




Nomenclature




















119905




119905


119905












Acknowledgments


References




























Volume 2014




Journal of











Journal of


Function Spaces






Algebra










119905sk =




119905sknu = 719+ 0064119905

119886+ 0061119905

119903minus 0348V

119886+ 0198119901

119886+ 0616119905co

119905skcl = 1217+ 0020119905

119886+ 0044119905

119903minus 0253V

119886+ 0194119901

119886+ 0005346119872 + 051274119905co

(11)


119864sk =

120582119878

119903

120582119878

119903

119864maxlt 046

120582119878


18120582119878

119903

119864maxminus 046)

1168] 046 le

120582119878

119903

119864maxle 17

119864max120582119878

119903

119864maxgt 17

(12)




119878

119903= 042


(13)


119864max

=

038 times (119901sk minus 119901

119886) times (26119862orrtot



(14)






(15)


119867 = 119864sk + 119862 + 119877 (16)

If 119905

119886 119905

119903 119901

119886 119872 V




119862res = 000152119872 (2856+ 0885119905

119886+ 0641119901

119886) (17)


119864res = 000127119872 (5934+ 053119905

119886minus 1163119901

119886) (18)




119903


PTS = (00025119905

119886minus 00657)


(20)





Height(cm)

Weight(kg)



3 Experiment





119905






5060 + 70 times 1060 = 118Wm2 119901







119886 mean radiant

temperature 119905






119886 mean radiant

temperature 119905




119892 and relative










Female(119899 = 513)

Total(119899 = 823)

Temperature 119905

119886


119886


119903







40

35

25

20

30

20140701 20140711 20140721 20140731

(∘C)





AMVLinear (AMV)

3

25

2

15

1

05

0 12 14 16PTS

18 2

AM

V

PTS = AMV

AMV = 09132 PTS + 00348 R2 = 03634


PTSAMV


35

25

3

2

PTS

AM

V

1

032 33 34

15

05

35 36to (∘C)



119900







119905


2





2

22

18

16

14

12

27 28 29 30 31 32 33

PTS


R2 = 07977p lt 0001

WGBT (∘C)


21


Mea

n PT

S

320 340 360 380 400 420 440 460 480

2

19

18

17

16

15

14

13


R2 = 07212p lt 0001



20140701 20140711 20140721 20140731

8

7

6

5

4

3

2

1

0

minus1



+275∘C)+29∘C)+295∘C)



119908

+ 03119905

119892

[6] ET 038119905

119886

+ 063119905

119892


119886

minus003RH+00054(119905

119886

sdotRH)minus

073 [14] THI 119905

119886


119886

minus 145) [13]







Linear (M)

PTS

AM

V

3

25

2

15

1

05

012 14 16 18 222

PTS = AMV



0 5 10 15Seniority

20 25 30 35

PTS

24

22

2

18

16

14

12

1


R2 = 00705 p = 02159

FemaleMale




5 Conclusions




Nomenclature




















119905




119905


119905












Acknowledgments


References




























Volume 2014




Journal of











Journal of


Function Spaces






Algebra












Height(cm)

Weight(kg)



3 Experiment





119905






5060 + 70 times 1060 = 118Wm2 119901







119886 mean radiant

temperature 119905






119886 mean radiant

temperature 119905




119892 and relative










Female(119899 = 513)

Total(119899 = 823)

Temperature 119905

119886


119886


119903







40

35

25

20

30

20140701 20140711 20140721 20140731

(∘C)





AMVLinear (AMV)

3

25

2

15

1

05

0 12 14 16PTS

18 2

AM

V

PTS = AMV

AMV = 09132 PTS + 00348 R2 = 03634


PTSAMV


35

25

3

2

PTS

AM

V

1

032 33 34

15

05

35 36to (∘C)



119900







119905


2





2

22

18

16

14

12

27 28 29 30 31 32 33

PTS


R2 = 07977p lt 0001

WGBT (∘C)


21


Mea

n PT

S

320 340 360 380 400 420 440 460 480

2

19

18

17

16

15

14

13


R2 = 07212p lt 0001



20140701 20140711 20140721 20140731

8

7

6

5

4

3

2

1

0

minus1



+275∘C)+29∘C)+295∘C)



119908

+ 03119905

119892

[6] ET 038119905

119886

+ 063119905

119892


119886

minus003RH+00054(119905

119886

sdotRH)minus

073 [14] THI 119905

119886


119886

minus 145) [13]







Linear (M)

PTS

AM

V

3

25

2

15

1

05

012 14 16 18 222

PTS = AMV



0 5 10 15Seniority

20 25 30 35

PTS

24

22

2

18

16

14

12

1


R2 = 00705 p = 02159

FemaleMale




5 Conclusions




Nomenclature




















119905




119905


119905












Acknowledgments


References




























Volume 2014




Journal of











Journal of


Function Spaces






Algebra












Female(119899 = 513)

Total(119899 = 823)

Temperature 119905

119886


119886


119903







40

35

25

20

30

20140701 20140711 20140721 20140731

(∘C)





AMVLinear (AMV)

3

25

2

15

1

05

0 12 14 16PTS

18 2

AM

V

PTS = AMV

AMV = 09132 PTS + 00348 R2 = 03634


PTSAMV


35

25

3

2

PTS

AM

V

1

032 33 34

15

05

35 36to (∘C)



119900







119905


2





2

22

18

16

14

12

27 28 29 30 31 32 33

PTS


R2 = 07977p lt 0001

WGBT (∘C)


21


Mea

n PT

S

320 340 360 380 400 420 440 460 480

2

19

18

17

16

15

14

13


R2 = 07212p lt 0001



20140701 20140711 20140721 20140731

8

7

6

5

4

3

2

1

0

minus1



+275∘C)+29∘C)+295∘C)



119908

+ 03119905

119892

[6] ET 038119905

119886

+ 063119905

119892


119886

minus003RH+00054(119905

119886

sdotRH)minus

073 [14] THI 119905

119886


119886

minus 145) [13]







Linear (M)

PTS

AM

V

3

25

2

15

1

05

012 14 16 18 222

PTS = AMV



0 5 10 15Seniority

20 25 30 35

PTS

24

22

2

18

16

14

12

1


R2 = 00705 p = 02159

FemaleMale




5 Conclusions




Nomenclature




















119905




119905


119905












Acknowledgments


References




























Volume 2014




Journal of











Journal of


Function Spaces






Algebra










2

22

18

16

14

12

27 28 29 30 31 32 33

PTS


R2 = 07977p lt 0001

WGBT (∘C)


21


Mea

n PT

S

320 340 360 380 400 420 440 460 480

2

19

18

17

16

15

14

13


R2 = 07212p lt 0001



20140701 20140711 20140721 20140731

8

7

6

5

4

3

2

1

0

minus1



+275∘C)+29∘C)+295∘C)



119908

+ 03119905

119892

[6] ET 038119905

119886

+ 063119905

119892


119886

minus003RH+00054(119905

119886

sdotRH)minus

073 [14] THI 119905

119886


119886

minus 145) [13]







Linear (M)

PTS

AM

V

3

25

2

15

1

05

012 14 16 18 222

PTS = AMV



0 5 10 15Seniority

20 25 30 35

PTS

24

22

2

18

16

14

12

1


R2 = 00705 p = 02159

FemaleMale




5 Conclusions




Nomenclature




















119905




119905


119905












Acknowledgments


References




























Volume 2014




Journal of











Journal of


Function Spaces






Algebra











Linear (M)

PTS

AM

V

3

25

2

15

1

05

012 14 16 18 222

PTS = AMV



0 5 10 15Seniority

20 25 30 35

PTS

24

22

2

18

16

14

12

1


R2 = 00705 p = 02159

FemaleMale




5 Conclusions




Nomenclature




















119905




119905


119905












Acknowledgments


References




























Volume 2014




Journal of











Journal of


Function Spaces






Algebra















119905




119905


119905












Acknowledgments


References




























Volume 2014




Journal of











Journal of


Function Spaces






Algebra
















Volume 2014




Journal of











Journal of


Function Spaces






Algebra









Research Article Predicted Thermal Sensation Index for the...

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Transcript of Research Article Predicted Thermal Sensation Index for the...