THE THERMAL ENVIRONMENT LEVEL ASSESMENT BASED ON HUMAN PERCEPTION

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1 THE THERMAL ENVIRONMENT LEVEL ASSESMENT BASED ON HUMAN PERCEPTION M. V. Jokl Czech Technical University, Czech Republic Corresponding SUMMARY A new way of e ermal level environment assessment based on operative temperature ermal level and new units decierm is introduced, which allow e feelings of man to be followed. Simultaneously e fact at e operative temperature decrease is felt e more unpleasantly e lower are temperatures is also taken into account. The assessment in decierms also allows e comparison (based on numerical values comparison) wi e noise level in decibels and odor level in deciodors and e whole environment level assessment (based on weighted constituent levels adding). Also syndrome SBS can be estimated, e effectiveness of heating and cooling appliances and even e condition of human organism reat by overwarming (hyperermia) or undercooling (hypoermia). INTRODUCTION The paper presents a new way of e ermal environment level assessment being able to give a true picture of e ermal environment level as perceived by man. Thus is way respects also e fact at e operative temperatures decrease is perceived e more uncomfortable e temperatures are lover, e. g. e decrease by 3 C from 10 C to 7 C is always more unpleasant an e decrease from 20 C to 17 C. The distribution of 15-day moving means of mortality against temperature is shown in Fig. 1. Simple correlation gave a coefficient of r= Mortality expressed as a quadratic function of temperature (Y= T+0.025T 2 ) produced a multiple correlation coefficient of 0.72 and t-values of and 12.2 for temperatures T and T 2, respectively. These appeared to be high enough to justify e preference for e polynomial model over linear. Minimum mortality was predicted by e quadratic equation at 23 C. From Fig. 1 it appears at mortality is accelerated below a critical mean temperature of about 18 C and especially ose below 16 C. On e warm side, temperatures did not reach sufficiently high values to enable identification of particularly critical resholds (see Auliciems and Skinner 1989). There is also a physiological background of perceiving cold and warm in different way: special sensors for cold and warm in e skin (see Fig. 2) and special evaluation centres in e brain (Fig. 3). New way originates from human body physiology where Weber-Fechner law is valid: R=k.logS (1) where R e human body response S e stimulus of e environment causing e response k e coefficient

2 PROPOSAL OF NEW EVALUATION SYSTEM At e ermal condition of environment is law can be applied as T L k log [ dth] (2) T = reshold where L operative temperature ermal level [decierm], [dth] T operative temperature [ C] T reshold reshold operative temperature, in is case optimal operative temp. [ C] Equation (2) corresponds wi e formula for noise assessment wi e so called acoustic pressure level P L p 20 log [ db] (3) P = 0 Where e ratio of acoustic pressures forms e stimulus, P is e acoustic pressure wiin e space investigated, P 0 is e acoustic pressure perceived lower limit 20 μpa. The unit decibel (db) has been used for acoustic pressure level, e unit decierm (dth) for operative ermal level. The analogical equations also exist for odor constituent of e environment (Jokl 1998, 2000), e so called deciodors, based on carbon dioxid, so called decicarbdiox (dcd) and on total volatile organic compounds (TVOC), so called decitvoc (dtv). CORRESPOND NEW UNITS TO HUMAN FEELINGS? The equation (2) for ermal environment assessment seems to be reasonable, bo from e human body physiology aspect and from e eory of similarity (Kline 1965, Kožešník 1983), however, its approval by an experiment is necessary, i.e. at decierms describe e man s perception. The perception of e ermal environment level can be described by ASHRAE scale (ANSI/ASHRAE ) (cold, cool, slightly cool, neutral, slightly warm, warm, hot). These should be proportional to ermal level, i.e. it must be proved at L = k1 ( AV) [dth] (4) where AV e values of ASHRAE scale k 1 coefficient of proportionality Of course, Weber-Fechner law (2) is valid simultaneously, so it must be proved at T A V = k 2 log (5) Topt to be L = k 1 AV. After substitution T = T L = k1 AV = k1 k 2 log k log Topt Topt [dth] (2) See fig. 4 where e results of experiments by Fishman and Pimbert (1979) are presented. There is e relationship between operative temperatures (axis x) and averages votes ASHRAE (axis y). Average values ASHRAE have been estimated in e range ±0.2 C for each temperature, e.g. for 20 C: 19.8 C to 20.2 C. The average activity was 80 W/m 2. The

3 feelings of 26 subjects were registered 8 times per day (between 9.30 and hour) for e whole year, i.e values were registered altogeer. From e graph is evident at e ASHRAE and calculated PMV values differ (e lowest difference is near neutral physiological state for which e PMV was derived). The relationship (6) can be estimated for ASHRAE values from e graph (Fig. 4): AV = logT = logT log = log (6) This can be rewritten in a general form T AV k 2 log (5) T = opt and erefore it is valid L = k 1 AV and it is evident at decierms correspond to human feelings and at operative temperature do not correspond to human feelings. THE OPERATIVE TEMPERATURE THERMAL LEVEL ESTIMATION Now ermal levels can be estimated for operative temperatures optimal and long-term and short-term tolerable. Optimal operative temperatures Optimal operative temperatures are determined by e neutral physiological state of man at his activity and cloing. The experimental estimation on is basis being very difficult (however in is case values from Jokl and Kabele 2006 experiments have been available) e optimal values were estimated by e votes of e subjects satisfied wi e evaluated environment (or dissatisfied in e range 10% to 30% related to e requested environment quality) (Fanger 1970, EN ISO 7730). To optimal operative temperatures (analogically as by noise and odors) correspond dth=0 because log1=0. Long-term tolerable operative temperatures Long-term tolerable operative temperatures have ranges too. Their beginning is identical wi optimum upper limit and eir end is determined by e operative temperature on an average skin temperature level because by higher operative temperatures: ere is e danger of human body hyperermia wi e body temperature increase. Range in dth: 46-90, see item Scale. The long-term tolerable operative temperatures can be admitted in warm environment only: e disturbed ermal equilibrium is balanced by sweating. In cold environment sweating corresponds shivering which does not exist wiin most people (shivering caused by nerves cannot be taken into account). Thus shivering cannot be respected as a protective mechanism of e human body. Therefore only short-term values can be taken into account in cold environment. The operative temperature can be estimated for e value minus 46 dth, e beginning of hypoermia of human body. It is interesting at e area of long-term values is e area of sick building syndrome as well (it is out of optimal values being long-term tolerable at e same time).

4 Short-term tolerable operative temperatures Short-term tolerable operative temperatures are also determined by eir limits. The beginning ey have in warm environment is identical wi maximal long-term tolerable values, in cold environment wi minimal values of optimum. The end in e warm is before e reshold of pain (cca 42 C, 135dTh)(pain is e same criterion for noise). Range in dth: , see item Scale. In cold environment ere is a new limit: if a man is able to work continuously (e.g. during e whole shift) during e chosen operative temperature. The limit in Czechia is 10 C, in USA 15 C only. Intolerable operative temperatures Intolerable operative temperatures are characterized only by eir beginning identical wi e end of short-term tolerable values. Range 135dTh and more, see item Scale. SCALE OF OPERATIVE TEMPERATURE THERMAL LEVELS It is determined by e basic equation (2) in which 135 k = (7) 42 log Topt Thermal levels, analogically to operative temperatures, are optimal, tolerable and intolerable (Table 1). Optimal values are very pleasant, pleasant and acceptable (optimal admissible from directives point of view). Tolerable are long-term and short-term tolerable. APPLICATION Two examples have been chosen: - Application to experimental values (Jokl, Kabele 2006) - Application to optimal operative temperatures in an airliner cabin starting also from experimental values in (Jokl, Kabele 2006) but transformed into Czech Directive. Application to experimental values based on neutral physiological state of man (Table 1) The following values have been chosen from e experimental results (Jokl, Kabele 2006): a) For 1.2 Met (70 W/m 2 ), 0.5 clo (optimal operative temperature 24.5 C) L = log [dth] 24.5 The skin temperature determining e upper limit of long-term tolerable values: T sk = q m +35.7= 34 C (Fanger 1970) where q m = 70W/m 2 (activity). The scale of operative temperature ermal levels is presented in Fig. 5. b) For 1.72 Met (100 W/m 2 ), 0.5 clo (optimal operative temperature 21.5 C) L = log [dth] 21.5 The skin temperature determining e upper limit of long-term tolerable values: 33 C The scale of operative temperature ermal levels is presented in Fig. 5.

5 c) For 2.1 Met (120 W/m 2 ), 0.5 clo (optimal operative temperature 19.5 C) L = log [dth] 19.5 The skin temperature determining e upper limit of long-term tolerable values: 32.5 C The scale of operative temperature ermal levels is presented in Fig. 5. In all ree cases following e corresponding ermal levels it can be assessed which measured operative temperatures in an interior are very pleasant, pleasant, acceptable or only long-term or short-term tolerable or intolerable. Application to optimal operative temperatures in an airliner cabin Optimal operative temperature in an airliner cabin is 22 C (dth=0). The corresponding scale of operative temperature ermal levels for activity 1.2 Met and cloing 0.75 clo ( L = log ) is presented in Fig. 6. At e flight beginning operative temperature 22 can be decreased to 21 C (dth=-10). After some flight time, when passengers make emselves comfortable by putting off eir jackets (decrease to 0.5 clo) and start to walk in e cabin (increase to 1.72 Met) it should be increased to 23 C (dth=9). The maximal admissible operative temperature increase can be 25.5 C (31 dth). In e case of some failure e long-term tolerable values are closing at C (89.4 dth). A NEW PROSPECT: THE ASSESMENT OF THE EFFECT THE THERMAL LEVEL ON THE TOTAL ENVIRONMENT Perhaps e greatest advantage of e new decierm unit is possibility of a new type microenvironment evaluation. First each constituent is assessed separately, and en its effect on e whole environment. Decierms can be also a new basis for a constituent mutual interaction study. The paper by Rohles et al. (1989) can be used for is purpose. Various constituents have different effects on e resulting environment; e.g. our heal is more reatened by cold an by aeroions. The preliminary results by Rohles are presented in Table 2. The operative temperature seems to be very important (16%), e corresponding hygroermal constituent has e greatest impact (30%), it is followed by illumination (24%), acoustic (22%), toxic (10%), odor (8%) and aerosol (6%) constituents. The influence of acoustic, odor and hygroermal constituents on e overall environment can be expressed as follows: P 22 P L acoustic = AC20log = 20log [db] (8) ρtvoc ρco 8 ρ 2 TVOC ρ CO L OD(50log 90log ) (50log 90log 2 odor ) = + = + [dco] (9) 30 L = HT(480.7log = (480.7 log [dth] (10) where dco = deciodors.

6 CONCLUSION THE BENEFITS OF DECITHERMAL SCALE The advantages of new proposed evaluation system can be summed up in e following items: 1. The undoubtable benefit of using e deciermal scale is at it gives a much better approximation to human perception of e ermal environment level compared to e operative temperature in grad Celsius. 2. The new decierms values also fit in numbers very well wi e db values for sound and odors, i.e. so ey can be compared to each oer. 3. The new decierms values allow e estimation of operative temperature impact on e whole environment. 4. The new units, decierm and deciodor, can be a new basis for a constituent mutual interaction study. 5. Decierms can be estimated by direct measurement: ermometers can be calibrated directly in new units, i.e. grad Celsius scale can be completed by decierm scale. 6. Decierms allow assessing e feasibility of e ermal environment level, i.e. to which extent it is pleasant or unpleasant. 7. Decierms allow defining newly e ranges of optimal, short-term and long-term tolerable environment condition. 8. Decierms allow a new definition of Sick Building Syndrome (SBS) caused by ermal environment condition it equals to long-term tolerable values. 9. Decierms allow estimating e condition of human organism reat by overwarming (hyperermia) or by overcooling (hypoermia) as a result of long-term tolerable values overcoming. 10. Decierms allow assessing e effectiveness of heating and cooling devices by a new way by estimation to which extent ey can satisfy optimal environment level for a user. REFERENCES 1. Auliciems, A., Skinner, J. L.: Cardiovascular dea and temperature in subtropical Brisbane. Int. J. Biometeorol 33, 1989, 3: Fanger, P. O.: Thermal Comfort. Danish Technical Press, Copenhagen Fishman, D. S., Pimbert, S. L.: Survey of e objective responses to e ermal environment in offices. In Indoor Climate, Copenhagen, Danish Building Research Institute, 1979, p Jokl, M. V.: New units for indoor air quality: decicarbdiox and decitvoc. Int. J. Biometeorol. 42, 1998, 2: Jokl, M. V., Kabele, K.: The optimal (comfortable) operative temperature estimation based on e physiological response of human organism. REHVA Journal (in print). 6. Kline, S. J.: Similitude and Approximation Theory. McGraw-Hill, New York Rohles, F. H., Woods, J. E., Morey, P. R.: Indoor environment acceptability: The development of rating scale. ASHRAE Transactions 95, 1989, 1: LIST OF TABLES Table 1. Recommended values of operative temperature ermal levels. Very pleasant 0-20 dth Optimal Pleasant dth Acceptable (admissible from prescription point of view) dth Tolerable Long-term tolerable dth Short-term tolerable dth Intolerable 135 dth and more * 22-6 h ** 6-22 h

7 Table 2. The impact of some constituents and eir parts on perceived total environment level (according to Rohles et. al. 1989). Constituent (or part of it) Impact (%) Constituent factors Hygroermal 30.1 HT = 0.30 globe temperature 15.8 air streaming 7.2 air humidity 7.1 Odor 7.5 OD = 0.08 Toxic (tobacco smoke only) 9.9 TX = 0.10 Aerosol 6.6 AE = 0.06 Acoustic 21.9 AC = 0.22 loudness 8.7 noisy distraction 8.6 pitch of sounds 4.6 Lighting 24 LI = 0.24 Brightness 11 Glare 7.9 Shadows 5.1 LIST OF FIGURES Figure 1. Distribution of 15-day means of deas during in Brisbane against temperature daily means (Auliciems, Skinner 1989). Figure 4. Comfort votes (ASHRAE scale) in relationship to indoor temperature. Activity 80 W/m 2, cloing 0.64 up to 0.82 clo. (Fishman and Pimbert 1979).

8 Figure 2. Skin receptors. Figure 3. Centres for cold and warm in hypoalamus. a) 1.2 Met, 0.5 clo b) 1.72 Met, 0.5 clo c) 2.1 Met, 0.5 clo Figure 5. Scale of operative temperature ermal levels for 1.2 Met, 0.5 clo (optimal operative temperature 24.5 C), 1.72 Met, 0.5 clo (optimal operative temperature 21.5 C) and for 2.1 Met, 0.5 clo (optimal operative temperature 19.5 C). Figure 6. Scale of operative temperature ermal levels for an airliner cabin.