I d . Eng. Chem. Prod. Res. Dev. 1981, 20, 18-23
18
restrictions in the fabric to bending. Elastic flexural rigidity represents the elastic component of stiffness. Coercive couple considers the frictional component of bending behavior. F i m e 8 exemDlifies a twical bending hvsteresis curve. Elasiic flexural iigidity a d coercive c&&e were determined as Go = F(As - AR - A, - A Q ) / ~ where Go = elastic flexural rigidity, A, = couple at first zero reading, AQ = couple at -1 cm-' reading, AR = couple at second zero reading, As = couple at +1 cm-' reading, F = wg(L 0.35)/2.5 = calibration factor of pointer, W = pointer mass, g, g = gravitation ratio, dyn/g, L = distance from gravity center of pointer to edge of pointer grip, and
+
Co = F(AR - A,)/2 where cO = coercive coup1e* Literature Cited Alley, V. L.. Jr.; McHatton. A. D. "A ProDosed QuantltathrsMeastre of Fabrk &ianae and the Relathre Characterlzahca of Some Aerospace Matedals by Handle Modull", Paper presented at the Ninth Alr Force oeophyeics L a b ratory Sclentlflc Balloon Symposlum, Portsmouth, N.H., Oct 1976. Alley, V. L., Jr. Trans. Am. Soc. Mech. €4. 1980, 702, 25. Behery, H. M. Alternate Fabrics for Distlncthre Ah Force Unlforms (Final R e port). Clemson Unhrersity, Clemson, S.C., 1979.
Received for review February 8, 1980 Accepted September 19, 1980
Presented at the 179th National Meeting of the American Chemical Society, Houston, Texas, March 1980. Cellulose, Paper and Textile Division.
Clothing as a Key to Energy Conservation Frederick H. Rohles and Ellrabeth A. McCullough" Institute for Environmental Research, Kansas State UnlversHy, Manhattan, Kansas 66506
The body's response to four environmental factors (air temperature, water vapor pressure, mean radiant temperature, and air velocity) interacting with the person's clothing and metabolic heat production (activity level) over a period of time determine his/her thermal comfort. The U.S. Emergency Building Temperature Restriction Plan became effective on July 16, 1979 and resMcted the air temperatwe levels in nonresidential buildings. specifically, thermostats could be set no higher than 18.3 OC for heating and no lower than 25.6 OC for cooling. The adding and removal of clothing is the most economical and effective way for expanding the personal comfort zone to the government limits. This paper discusses measuring the insulation value (clo) and permeability Index (i,) of individual clothing items and ensembles using a copper manikin housed in an environmentally controlled chamber. Methods for predicting comfort levels of people at different clo value and temperature combinations are also presented.
The United States Emergency Building Temperature Restriction Plan became effective on July 16,1979. Briefly, this plan restricted the temperatures to which commercial, industrial, government, and other nonresidential buildings could be heated or cooled. Specifically, thermostats could be set no higher than 18.3 "C (65 O F ) for heating and no lower than 25.6 "C (78 O F ) for cooling-except to achieve a dew point temperature of 18.3 "C (65 O F ) (US.Department of Energy, 1979). Implications of the plan were widespread, and enforcement procedures were questioned. Consequently, the law may be revised in the future. However, people will continue to adjust their thermostats voluntarily in both public and residential buildings in an attempt to decrease energy costs. Factors Affecting Thermal Comfort The body's response to four environmental factors (air temperature, water vapor pressure, mean radiant temperature, and air velocity) interacting with the person's clothing and metabolic heat production (activity level) over a period of time determine his/her thermal comfort. Air temperature, which is measured by a dry bulb thermometer, is the factor that is most often manipulated to higher and lower levels to decrease energy consumption. However, many people have indicated that they are not comfortable at the new energy-saving temperature settings. This is probably because they have not modified any of
the other six factors in an effort to compensate for the change in temperature and expand their personal comfort zone. Therefore, we will discuss the factors which influence man's response to the thermal environment with an emphasis on strategies for manipulating clothing as a means to energy conservation. Water vapor pressure is the pressure exerted by water vapor in air as measured by a dew point thermometer or expressed as relative humidity. The upper limit specified for cooling in the Emergency Building Temperature Restriction Plan is 25.6 "C at 18.3 "C dew point. In this condition, approximately 10% of sedentary individuals wearing light clothing will be uncomfortable (Rohles et al., 1975). If, however, the activity level of the occupants were increased, an even greater percentage would be uncomfortable. Dehumidification at this air temperature would increase comfort slightly, but since this uses energy, as a conservation strategy it is impractical. At the heating limit of 18.3 "C, the humidity level in the Restriction Plan is not specified; therefore raising it would appear to be a good approach to increasing comfort. However, heating moist air requires more energy than heating dry air, and although humidity contributes significantly to our comfort at high temperatures, it has little influence at temperatures as low as 18.3 "C. This should not be interpreted that we should ignore the humidity; however, in the "middle" temperature range, humidity
Q196-4321/8l/1220-0018$01.QQf0 0 1981 American Chemical Society
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20, No. 1, 1981 19
does not affect comfort significantly. Mean radiant temperature is defined as the temperature of a uniform black enclosure in which a solid body or occupant would exchange the same amount of radiant heat as in the existing nonuniform environment. A 1 "C decrease in air temperature can be offset by a l "C increase in mean radiant temperature (Goldman et al., 1979). Increasing insulation of floors, walls, and windows will keep the mean radiant temperature closer to the air temperature in value. However, the Emergy Building Temperature Restriction Plan specifically prohibits the use of radiant space heaters. Air velocity can be increased through the use of fans according to the Restriction Plan. Increasing the air velocity will increase a person's heat loss through evaporation which is desirable at higher air temperatures. However, the air flow should be uniform or people will feel discomfort from drafta (Fanger, 1977). Fans may be undesirable in an office because they increase the noise level and often blow items around. The activity level of an individual is defined by the unit MET, where 1MET corresponds to 50 kcal/m2 h or sedentary activity. As the level of activity is increased, metabolic rate increases. Less insulation is needed because producing body heat is as effective as preserving it. However, increasing a person's activity level is not an effective strategy for staying comfortable at lower temperatures. In fact, the trend in society is toward a.growing mechanization of tasks. The thermal conditions to which man is exposed are never constant for long periods of time. In general, three types of non-steady-state conditions can be identified. The first involves a discrete situation exemplified by moving from one condition to another. However, the individual adapts to a new environment in about 15 min, so this phenomenon is of little engineering and design significance (Rohles and Wells, 1977). The second type of temperature fluctuations are known as "ramps" or "drifts" and involve allowing the temperature of a room to drift with the outside temperature conditions. Night set-back of thermostats is an example of the result of drifts. Bergland and Gonzalez (1978) found that slow temperature drifts of f0.5 "C/h (fl"F/h) about a thermally neutral temperature are almost indistinguishable from constant temperature conditions, and a drift of this magnitude which causes the temperature to deviate from the neutral point by 1.9 "C (3.5 O F ) will only reduce thermal acceptability to about 80%. The third temporal condition is related to cyclical temperature fluctuations which are associated with thermostat tolerances, the size and effectiveness of the heating and cooling systems, and the thermal efficiency of the structure (Le., storm windows, insulation). In a study on the effect of cyclical temperatures on thermal comfort, Rohles et al. (1980) identified four temporal dimensions: (1)the temperature and relative humidity about which the fluctuation occurs; (2) the amplitude of the temperature swing; (3) the rate of temperature rise in degrees per hour; and (4) the rate of temperature decline in degrees per hour. From a study involving 800 subjects in which these variables were varied systematically, it was concluded that for people engaged in near-sedentary activities while wearing light clothing in temperature conditions for comfort, the thermal environment will be acceptable if t h e rate of change does not exceed 3.3 "C/h (6 "F/h) and if the amplitude is less than or equal to 3.3 "C or f1.6 "C. The conditions will be unacceptable both in and out of the comfort zone at temperatures which exceed these values.
FRONT
BACK
Figure 1. Thermistor locations on the copper manikin.
Clothing refers to all of the items that lie between a nude human being and the physical environment. Individual clothing items are described in terms of their design and constituent materials. The insulation value, moisture permeability index, and pumping coefficient are clothing parameters which affect the thermal comfort of people in different environments. Clothing Insulation Values The insulation of a clothing system is defined in terms of a clo unit. Gagge et al. (1941) derived the value for 1 clo by first considering that the resting metabolic heat production of an average man is about 50 kcal/m2 h. Approximately 25% of this heat is lost via the respiratory system and by diffusion of moisture through the skin. Therefore, 38 kcal/m2 h remains to be lost through the clothing via radiation and convection (Hollies and Goldman, 1977). The temperature difference across the clothing is equal to the difference between the mean skin and the ambient air temperature (TJ, temperature (T,) assuming the mean radiant temperature of the surroundings is equal to the air temperature. Consequently, a clothed person with a comfortable skin temperature of 33 "C (92 O F ) in a comfortable environment at 21 "C (70 OF), has a 12 "C temperature gradient across which 38 kcal/m2 h is transferred. A heat transfer coefficient of 0.32 "C m2 h/kcal is calculated by dividing the temperature difference by the heat flow (Le., 12/38) (Hollies and Goldman, 1977). Winslow et al. (1940) had previously determined that about 0.14 O C of the 0.32 "C total was contributed by the surrounding air layer, so 0.18 "C was contributed by the clothing alone. Thus, 1clo of insulation is equal to 0.18 "C m2 h/kcal. The reciprocal of this value, 5.55 kcal/m2 h "C or 6.45 W/m2 "C, is often used in calculations for convenience. The thermal insulation value ( d o ) of a clothing ensemble is best measured using a heated manikin in thermal equilibrium with its surroundings. The manikin at Kansas State University consists of a black anodized copper skin formed to approximate the physical form and size of a typical man. Heating wires, sewn in a cloth carrier, are bonded to the inside surface of the copper skin to provide internal heating distributed so as to approximate the skin temperature distribution of a human. All heating circuits
20
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20, No. 1 , 1981
except the hands and feet are connected in a series to allow for independent temperature control in the extremities. The manikin is instrumented with 16 thermistor sensors in various locations. (See Figure 1.) The insulation values, including the external air layer (IT),are measured on the dry manikin in an environmentally controlled chamber with the air velocity 0.1 m/s and the mean radiant temperature equal to the air temperature. The equation for calculating IT is 6.45(T8- T,)A, IT = (1) HD where HD = power input (W), A, = manikin surface area (m2),T, = mean skin temperature (“C), T, = ambient air temperature (“C), and IT = total thermal insulation of clothing plus boundary air layer ( d o ) . The clo value (IT)can be converted to the R value using the formula R IT = 0.88
To determine the intrinsic d o value of a clothing ensemble (Icl),it is necessary to subtract the insulation provided by the air layer over the ensemble from the total d o value (IT) = IT- Ia/fc1 (3) where Icl= intrinsic thermal insulation of clothing ( d o ) ,
IT = total thermal insulation of clothing plus boundary air layer (do), I, = thermal insulation of air layer around nude manikin ( d o ) ,and f d = clothing area factor. Values for the clothing area factor (fcl) are dependent upon the design of the ensemble and may be obtained from the literature (Fanger, 1973) or determined using a photographic method (Seppanen et al., 1972). The value for I, is obtained by operating the manikin without clothing and using eq 1 to find I, at various values of (T,- T,). Moisture Permeability As the air temperature rises, the radiation and convection heat loss decreases whereas evaporative cooling increases (Goldman, 1973). consequently, the evaporative potential (Woodcock, 1962) of a garment should be determined in addition to the d o value for predicting thermal comfort a t extreme temperatures and/or high activity levels. The moisture permeability index (i,) of clothing ensembles can be measured with a “sweating” copper manikin. A cotton “skin” is wetted to simulate a body covered with sweat. The water displaces trapped air so that the skin does not contribute to the insulation value. The permeability index is calculated as follows
where Hw= power input with cotton “skin” wet (W), A, = manikin surface area (m2),IT = total thermal insulation of clothing plus boundary air layer (clo), Ti, = mean skin temperature, wet run (“C), Taw= ambient air temperature, wet run (“C), S = constant = 2.2 OC/mmHg vapor pressure, Paw= saturated vapor pressure at T,, (mmHg), Pa = saturated vapor pressure at Taw(mmHg), 4, = ambient air relative humidity (% ), and i, = moisture permeability index (dimensionless), The gradient for evaporative heat transfer is the difference between the vapor pressure at the surface (P,) and the ambient vapor pressure (4,Pa)in mmHg. The parameter S is a factor which converts a vapor pressure
difference to an effective temperature difference (Goldman, 1973). The permeability index (i,) can range from zero for an ensemble with no evaporative transfer to 1 for clothing with maximum moisture permeability. The evaporative impedance (i,/clo) indicates the maximum sweat evaporative cooling possible in a given environment without wind (Goldman, 1973). Thus a person wearing an ensemble where ,i = 0.45 and clo = 1.50 can obtain about 30% of the maximum cooling possible (0.45/1.50 = 0.30). Pumping Body motion increases the heat exchange between a person and the environment by creating convection currents at the surface and within a clothing ensemble. It also accelerates the rate of evaporative cooling for a sweating person (Holliesand Goldman, 1977). Researchers a t the U.S. Army Research Institute of Environmental Medicine have attempted to measure and quantify this effect which they call the pumping coefficient. More work, however, is needed in this area. Persons at low to medium activity levels in indoor environments usually do not lose a large amount of heat through evaporation. Consequently, determination of the permeability index and pumping coefficient is not that c ~ c i a l .The clo value is the key factor that we should alter to expand the comfort zone and save energy. Index of clo Values Through the use of the copper manikin in simulated indoor conditions, Sepannen et al. (1972) developed an index of clo values for a great variety of individual men’s and women’s garments as well as clothing ensembles. Selected clo values are listed in Table I. The researchers also reported a greater range in the clo value of ensembles commonly worm by women than those commonly worn by men. Specifically, there was a larger variety of design features and fabrics represented in women’s garments which accounted for more variety in ensemble combinations for women than for men. A linear regression equation was then developed by Sprague and Munson (1974) which can be used to predict the insulation value of men’s and women’s clothing ensembles from individual garments constituting that ensemble. This allows the estimation of the insulation value of infinite numbers of clothing ensembles. men: Icl = 0.727cIi + 0.113
(5)
women: Icl= 0.770cIi + 0.050 (6) where Eli = sum of intrinsic thermal insulation values of individual clothing items ( d o ) and Icl = estimate of intrinsic d o value for ensemble ( d o ) . The difference between these two equations presumably reflects differences in compressibility between men’s and women’s clothing items. Insulation is a linear function of thickness, so the differential response of fabrics to compression would require adjustments. However, today men and women are dressing more similarly with respect to fabrics and garment design. Consequently, the new ASHRAE standard will combine the two equations into one (ASHRAE, 1980). Icl = 0.82(CIi) (7) Lower Thermal Comfort Threshold After the ensemble clo values are obtained by direct measurement on the copper manikin or by prediction from individual items in the d o value index, the results may then be used to compute the Lower Thermal Comfort Threshold (LTCT). This is the temperature and relative
Ind. Eng. Chem. Rod. Res. Dev., Vol. 20, No. 1, 1981 21
Table I. Intrinsic Insulation (clo Values) for Individual Items of Clothing men
O C
2.0"
'
20 I
'
'
'
25
'
I
'
'
'
'
30
SEDENTARY S O X RH
women
clo clothing clo Underwear 0.06 bra and panties sleeveless 0.05 0.09 half slip T shirt 0.13 0.05 full slip briefs 0.19 long underwear upper 0.10 long underwear upper 0.10 long underwear lower 0.10 long underwear lower 0.10 clothing
shirt light, short sleeve long sleeve heavy, short sleeve long sleeve (plus 5% for tie or turtleneck vest light heavy trousers light heavy sweater light heavy jacket light heavy socks ankle length knee high shoes sandals oxfords boots a
Torso blouse 0.14 light 0.22 heavy 0.25 dress 0.29 light heavy 0.15 0.29 0.26 0.32 0.20 0.37 0.22 0.49
skirt light heavy slacks light heavy sweater light heavy jacket light heavy
Footwear stockings 0.04 any length 0.10 panty hose shoes 0.02 sandals 0.04 pumps 0.08 boots
0.20 0.29
64
68
72
76
80
84
O F
0.22 0.70
OPERATIVE TEMPERATURE
Figure 2. Clothing insulation necessary for various levels of comfort at a given temperature (ASHRAE, 1980).
0.10 0.22 0.26 0.44 0.17 0.37 0.17 0.37
0.01 0.01
0.02 0.04 0.08
Seppanen et al. (1972); ASHRAE (1980).
humidity combination at which most people would be comfortable for a given amount of clothing insulation at low activity levels. The equation was derived from a model developed at Kansas State University by Rohles, Woods, and Nevins (1973) based on data collected from human subjects in environmentally controlled chambers. LTCT = 29.74 "C - 7.29 OC(I,J (84 LTCT = 85.54 OF - 13.1 OF(I,.,) (8b) where LTCT = lower thermal comfort threshold (ET*)and IcI= intrinsic thermal insulation of clothing (clo). Effective temperature, designated as E P ,is an index that combines the air temperature and relative humidity into a single value; it is physiologically derived by identifying the dry bulb condition at 50% relative humidity where constant body wettedness resulting from regulatory sweating occurs (Gagge et al., 1971). Thus, ET* deviates from the dry bulb temperature above and below the 50% R.H. level. If we lower the ET*,we can determine how much clo we will need to add to be comfortable, or conversely, if we add insulation, how much we can drop the EP. Adjusting the Insulation Value of Clothing to Achieve Thermal Comfort Over the past 50 years in which research on comfort has been systematically conducted, the temperatures preferred by people in the winter have been rising, and the clothing worn has become lighter (Nevins, 1966). The American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) has sponsored numerous studies
Table 11. Men's Summer Clothing Ensemble garment underpants light weight shorts light weight shirt, short sleeves sandals rli (sum of clo values for individual garments) Id (estimated d o value for the ensemble, ASHRAE formula)
0.05 0.22 0.14 0.02 0.43 0.35
concerning the interrelationships between the above seven factors and their effect on human comfort. This organization has used these and other research findings to develop and revise the ASHRAE Standard: Thermal Environmental Conditions for Human Occupancy (1980). The standard contains basic comfort criteria for specifying conditions that are thermally acceptable to 80% or more people. Figure 2 presents the clo values and operative temperatures (i.e., numerical average of the air and mean radiant temperatures) which correspond to the optimum comfort level and to the 80% acceptability limits as defined by the standard. By examining Figure 2, we can predict how people would have to alter their clothing insulation to stay comfortable at the new temperature extremes of 18.3 "C (65 O F ) and 25.6 "C (78 OF). Warm Indoor Environments. The ASHRAE chart indicates that a person's clothing insulation should be reduced to 0.1-0.6 clo (ideally, 0.3) to maintain comfort at 25.6 "C (78 OF). By removing clothing and exposing the skin, or by wearing loose, permeable clothing, people can minimize the amount of sweat-wetted body surface area and increase heat loss via radiation, convection, and evaporation. A recent study conducted for the Federal Energy Adminiitration (Gagge and Nevins, 1976) revealed that at 25.626.7 "C (78-80 O F ) , the thermal sensitivity of men to heat was greater than that of women even after corrections were made for differences in clothing insulation. However, the men tended to wear 50% more clothing (i.e., insulation) than women in the summer at work. For example, women wear sun-dresses, sleeveless blouses, and wrap-around skirts that do not require slips, and the ensembles can be complimented with sandals without the use of hose. In comparison, the male executive will wear a short-sleeve shirt, tie, long trousers, underwear, shoes, and sometimes a coat. An ideal ensemble for a man in the summer is presented in Table 11. Unfortunately, the removal of this much clothing may be socially unacceptable in many indoor environments. In addition, some people are reluctant to wear shorts and reveal their legs.
22
Ind. Eng. Chem. Prod. Res. Dev., Vol. 20, No. 1, 1981
Table 111. Women's Winter Clothing Ensemble garment bra and panties heavy weight blouse, long sleeves heavy weight slacks medium weight sweater, long sleeves, V-neck suit jacket socks, knee-high shoes r l , (sum of clo values for individual garments) IC1(estimated clo value for the ensemble, ASHRAE formula)
0.05
0.29 0.44 0.25
0.37 0.10 0.04 1.54 1.26
Cool Indoor Environments. According to Figure 2, a person engaged in sedentary or light work should wear between 1.2 and 1.8 clo (ideally, 1.5) at an air temperature of 18.3 " C (65 OF) to achieve thermal comfort. Although men and women basically prefer the same temperature ranges for comfort (Fanger, 1973), women are more sensitive to the cold than are men, particularly in their extremities (Gonzalez and Nishi, 1976; Gagge and Nevins, 1976). A typical woman's clothing ensemble that provides adequate insulation is presented in Table 111. Although convection heat low is largely a function of fabric thickness, there is a limit as to how much bulk and weight a person can add. Thick, cumbersome clothing can restrict mobility and contribute to a less attractive appearance according to current fashion standards. Consequently, many individuals resist changing their clothing habits to achieve thermal comfort. Distribution of Insulation on the Body. Although studies and prediction models indicate how much clothing insulation a person needs to be comfortable in different environments, they do not specify the optimum distribution of the clo on the body. If clothing items are not distributed uniformly over the body, local warm and cold discomfort may occur at different parts of the skin although the body as a whole is thermally neutral (Le., comfortable) (Fanger, 1977). Specifically,a decline in the temperature of the extremities usually signals the onset of thermal discomfort. McIntyre and Griffiths (1975) found that when subjects put on a sweater (0.3 clo) at 19 "C and 15 O C (66 "F and 59 OF), it did not eliminate their discomfort in the hands and feet. The addition of the sweater did, however, increase their general sensation of warmth. Fashionable footwear (such as boots and closetoed shoes) and stockings that would adequately insulate an individual's feet in an 18.3 "C (65 O F ) environment are available in the marketplace and commonly worn by many people. However, gloves or mittens impair a person's manual dexterity for many tasks, and consequently, they are not appropriate for indoor wear. In addition, hats are not yet socially acceptable for indoor environments. Methods for Determining clo Values In addition to the manikin, guarded hot plates, other mechanical devices, and units other than clo (e.g., R and Tog) are used to assess thermal transfer across textile systems. Studies using a guarded hot plate have shown that the relationship of 1.57 clolcm of fabric thickness holds for most conventional fabrics, regardleas of their fiber content and fabric construction (Hollies and Goldman, 1977). However, the manikin measurements reflect not only the contribution from fabric thickness but also the trapped air insulation between the skin and clothing. Garments should be tested on a manikin so that the effects of fabric overlap and garment design, shape, fit, and layering are reflected in the measurements. These characteristics vary extensively among clothing ensembles and
consequently alter insulation values. Therefore, measurements of convective and radiant heat loss and evaporative heat loss on small flat pieces of fabric have little correlation with the respective values associated with clothing ensembles. The number of manikins in the world is limited. Manikins instrumented for thermal comfort research are located at the Kansas State University Institute for Environmental Research in Manhattan, Kans., the US. Army Research Institute for Environmental Medicine in Natick, Mass., the Technical University of Denmark in Copenhagen, and the Bekleidungsphysiologisches Institut in Hohenstein, Germany. In addition, the instrumentation is complex, and the data collection procedure is timeconsuming and expensive. Consequently, other methods for measuring, estimating, or predicting garment clo values have been recently developed. Azer (1976) used a heat transfer model to predict the thermal insulation values of single-layergarmenb from the physical properties of their fabrics. He then recommended the use of Sprague and Munson's (1974) linear regression equations to predict the clo values of ensembles. Nevins developed a clothing check lit which could be used to describe the garments worn by people (Nishi et al., 1976). He then estimated the individual clo values by using the clothing index of Seppanen et al. (1972) and calculated the clo for the ensembles using the regression equations. Nishi et al. (1975) also used a calorimetry method for directly measuring the thermal efficiency of clothing when worn by live subjects in a climate-controlled chamber, during rest and exercise. Conclusions and Recommendations Even without government restrictions, many people will voluntarily lower their thermostats in the winter and raise them in the summer in an effort to conserve energy. Changing the insulation value ( d o ) of clothing is the most economical and effective way of providing thermal comfort under these conditions. Although people cannot be compelled to alter their clothing habits drastically, dress codes should be modified to allow people to adjust their clothing more effectively. In addition, information regarding the insulation properties of garments should be provided to consumers so that they can select the appropriate clothing for different environments. Some manufacturers of outdoor clothing are beginning to recognize the marketing potential of being able to quantify and advertise the thermal properties of their products. However, some product claims are based on the results obtained with inadequate test procedures or fabricated rating systems. In light of the quality control concerns of manufacturers and the regulations on labeling and advertising, it is necessary to have reliable and valid methods for assessing the insulation value of clothing. We suggest the development of a voluntary standard which would consist of an expanded clo value index of a wide variety of men's and women's clothing items and a formula for estimating the clo value of ensembles. The index would provide a description of the garment design, selected fabric properties such as construction, weight, thickness, and permeability, and the clo value measured on a manikin. Manufacturers who wanted to label their products would have a standard source of information on which to base their product claim, and no expensive testing would be necessary. In addition, the information in the standard could be made available to consumers through the educational system and the media to enable them to estimate the insulation value of unlabeled garments on their own. In this way, people could use clothing more
Ind. Eng. Chem. F+rcd.Res.
effectively to expand their thermal comfort zone. Literature Cited American Society of Heating, Refrigerating, and AlrCondkionlng Engineers, Inc., “ASHRAE Standard 55-74R-Thermai Environmental Condltlons for Human Occupancy”, ASHRAE: New York, Apr 25, 1980. Azer, N. Z. ASHRAE Trans. 1978, 82(I), 87-106. Bergland, L. G.; Oonzalez, R. R. ASHRAE Trans. 1978, 84(II), 110-114. Fanger, P. 0. Ann. &cup. Hyg. 1977, 20, 285-291. Fanger, P. 0. “Thermal Comfort-Analysis and Application in Environmental Engineering”, McQraw-Hill: New York, 1973. Gagge, A. P.; Burton, A. C.; Bazett, H. C. Science 1941, 94, 428-430. Gagge, A. P.. Nevins, R. G. “Effect of Energy Conservation GuMellnes on Comfort, Acceptability, and Heath”, Report prepared for the Federal Energy Office, Washington, D.C., by the John B. Pierce Foundation Laboratory, New Haven, CN, Mar 1976. Gagge, A. P.; Stoiwijk, J. A. J.; Nlshl, Y. ASHRAE Trans. 1971, 77(I), 247-262. Nishl, Y.; Gonzalez, R.; Nevins, R. G.; Gagge, A. P. ASHRAE Trans. 1978, 82(II), 248-259. Goidman, R. F. “Clothing Design for Comfort and Work Performance in Extreme Thermal Environments”, Third Shirley International Seminar on Textiles for Comfort, Manchester, England, June 15-17, 1973. Goldman, R. F.; Bergland, L.; Rohles, F. H. ”Human Factors in Dynamic Control of Environmental Condition”. Workshop on Dynamic Response of Environmental Control Process in Buildings, Purdue University, Lafayette, IN, Mar 13-15, 1979, pp 32-48. Gonzalez, R. R.; Nlshl, Y. ASHRAE Trans. 1978, 82(I), 76-86. Hollies, N. R. S.;Goldman, R. F., Ed.; “Clothing Comfort”, Ann Arbor Science Publishers, Inc.: Ann Arbor, MI, 1977.
Dev. 1981, 20, 23-31
23
McIntyre, D. A., Grlffiths, I. D. Ergonomics 1975, 78(II), 205-211. Nevins, R. G. 6uM. Res. Jul-Aq 1988, 27-30. Nlshi, Y.; Oonzalez, R. R.; Gagge, A. P. ASI-IRAE Trans. 1975, 87(II), 183-1 99. Nishi, Y.; Oonzalez, R. R.; Nevins, R. 0.;Gagge, A. P. ASHRAE Trans. 1978, 82(II), 248-259. Rohles, F. H.; Hayter, R. B.; Miliken, G. A. ASHRAE Trans. 1975, 87(II), 148- 156. Rohles, F. H.; Skipton, D. E.; Milliken, G. A.; Krstlc, I. ASHRAE Trans. 1980, 86(II). Rohles, F. H.; Wells, W. V. ASHRAE Trans. 1977, 83(II),21-29. Rohles, F. H.; Woods, J. E.; Nevins, R. G. ASHRAE Trans. 1973, 7S(II), 71-80. McNall, P. E.; Munson, D. M.; Sprague, C. H. ASHRAE Trans. Seppanen, 0.; 1972, 78(I), 120-130. Sprague, C. H.; Munson, D. M. ASHRAE Trans. 1974, 80(I). 120-129. US. Department of Energy, “How to Comply with Emergency Building Temperature Restrictions”, U.S. Department of Energy, Washington, D.C., July, 1979. Winslow, C . I . A.; Gagge, A. P.; Herrington, L. P. Am. J. physbl. 1940, 737, 79. Woodcock, A. H. Text. Res. J . 1982, 32, 628-723.
Received for reuiew April 16, 1980 Accepted August 22,1980
Paper presented at the 179th National Meeting of the American Chemical Society, Cellulose, Paper, & Textile Division Symposium on Textile Comfort, Houston, TX, Mar 26, 1980.
111. Symposium on Automobile Exhaust Catalysis L. L. Hegedus and W. K. Hall, Chairmen 178th National Meeting of the American Chemical Society Washington, D.C., September 1979 (Continued from September 1980 issue)
Design Factors of Dual Bed Catalysts Jack C. Summers and Davld R. Monroe’ Physical Chemistry Department, General Motors Research Laboratories, Warren, Michigan 48090
Dual bed catalysts offer one means of meeting increasingly stringent automobile emission standards. The work presented herein is an investigation into the effect of various design parameters on the performance of dual bed systems. For front bed catalysts in which Rh is very active, neither Pt nor Pd adds to the warmed up CO or HC conversions. Pt and W do affect the NO conversion activii of Rh, deteriorating rich and enhancing lean conversions. Pt and Pd assist Rh for lightoff. The three-way durability performance of Pt and Pd Is poorer than that of Rh. The main function of the rear bed of a dual bed converter is to oxidize the CO and HC emitted from the front bed under warmed up operation. Increasingthe noble metal loading of the rear bed increases the warmed up durability of the dual bed catalyst. Poisons are unequally distributed with P and Pb collecting heaviest on the front bed and S heaviest on the rear.
Introduction The simultaneous control of nitrogen oxides, carbon monoxide, and hydrocarbon emissions from automobile exhaust can be achieved by the use of complex three-way catalysts, in connection with an O2sensor and closed loop electronic circuitry (Canale et al., 1978;Engh and Wallman, 1978). This &fuel ratio (A/F) control system is required to keep the exhaust composition near the stoichiometric point where simultaneous conversions of these emissions can be attained. Two alternate approaches have been developed around the closed-loop A/F control system; both represent a compromise between NO and CO control. The single bed (or three-way) approach uses one catalyst bed filled with a three-way catalyst (Ghandi et al., 1976;He-
gedus et al., 1979),operating in a near stoichiometric exhaust. The dual bed approach, which is the subject of this paper, employs a smaller volume of three-way catalyst in the front bed followed by an oxidation catalyst. Air is injected between the two catalyst beds. For the same total volume, the single bed approach favors NO conversion while the dual bed approach favors CO conversion. Dual bed catalysis, like three-way catalysis, requires the use of an O2sensor and closed loop electronic circuitry. During warmed up operation, the exhaust entering the first bed is maintained near the stoichiometric point, while air is pumped into the second or oxidizing bed in order to oxidize the CO and HC that were not converted in the front bed. During the warm-up portion of the operation, the system
o ~ ~ ~ ~ ~ ~ i 1 ~ i 1 i ~ ~ o - o0o 1981 ~ ~ $American o 1 . o Chemical o 1 ~ Society
