Measurement of local evaporative resistance of a typical clothing ensemble using a sweating thermal manikin

Abstract

To accurately simulate human physiology and thermal comfort, certain human physiological and comfort models categorize the human body into multiple parts. Most of these body parts are normally clothed, which must be quantified in the simulation. However, existing databases of clothing evaporative resistance only characterize the evaporative resistance of the whole body and not those of individual body parts. This implies that each body part has the same level of clothing evaporative resistance. In this research, we measure the local clothing insulation and evaporative resistance. Here, we present the local thermal characteristic values as well as the values for the whole body.

Introduction

The effect of clothing on the exchange of moisture between the body and the environment is conventionally expressed as the clothing evaporative resistance of the whole body. This has been used to evaluate human physiology and thermal comfort. Sweating thermal manikins are commonly used to measure clothing evaporative resistance. International standards such as the International Organization for Standardization 9920 (ISO 9920) and the American Society for Testing and Materials F2370 (ASTM F2370) have stipulated methods for measuring the thermal properties of clothing, using thermal manikins.

McCullough et al. and Wang et al. conducted round‐robin studies of research institutes in countries around the world to measure the clothing evaporative resistance, using sweating thermal manikins. Their results showed that the reproducibility of the experimental results for clothing evaporative resistance was lower than that of the results for clothing insulation, apparently because the experimental conditions were not completely uniform. Therefore, work is underway for strictly unifying the experimental conditions, measurement methods, and other aspects to develop international standards for measuring clothing evaporative resistance. Many researchers, including Havenith et al., Holmér et al., Tamura et al., and Sakoi et al., have used sweating thermal manikins to measure these parameters.

However, these studies examined the clothing evaporative resistance of the whole body. In these studies, the body is considered to be uniformly clothed, and the clothing evaporative resistance of the whole body is calculated using the amount of heat of moisture evaporation and the difference in mean vapor pressures between the skin and the environment. In other words, these studies do not fully express the properties of actual clothing ensembles, such as the materials used and how the clothing overlaps at different areas. Averaging out factors such as the materials used and how the clothing overlaps, followed by applying the clothing evaporative resistance of the whole body to specific locations, can produce discrepancies when measuring human physiology and thermal comfort at different locations on the body. Hence, it is preferable to employ the clothing evaporative resistance of each location.

Therefore, in the present study, we reproduced a hot environment in a climate‐controlled room and used a sweating thermal manikin that was divided into 20 segments to measure the clothing evaporative resistance at each segment, under eight summer clothing ensembles. In addition to these values, segment‐based measurement values of intrinsic clothing insulation were used to calculate the clothing vapor permeation efficiency at each segment. Finally, the clothing thermal properties were investigated for each segment.

Measuring clothing thermal properties at different segments using a sweating thermal manikin

Outline of the experiment

Experiments were conducted from 22 November 2018 to 1 December 2018, in a climate‐controlled room (laboratory) at Tokyo Polytechnic University, to measure the thermal properties of clothing at different locations on the body, using a sweating thermal manikin.

Sweating thermal manikin

The body segments and their respective surface areas on the manikin are listed in Table . The sweating thermal manikin used in this study was an Asian male model of the 20‐zone sweating thermal manikin (Newton, Measurement Technology North West). It weighed 30 kg, was 168.5 cm tall, and was divided into 20 segments. The computer software called Therm DAC 8 was used to control some aspects of the sweating thermal manikin such as the surface temperature, heat flux, thermal resistance, and the sweating rate from each segment.

Body segments and their respective surface areas on the manikin

No.	Segment	Area [m2]	No.	Segment	Area [m2]
1	Face	0.05	11	Stomach	0.12
2	Head	0.10	12	Back	0.09
3	R Upper arm	0.07	13	R Hip	0.08
4	L Upper arm	0.07	14	L Hip	0.08
5	R Forearm	0.06	15	R Thigh	0.13
6	L Forearm	0.06	16	L Thigh	0.13
7	R Hand	0.05	17	R Calf	0.12
8	L Hand	0.05	18	L Calf	0.12
9	Chest	0.12	19	R Foot	0.06
10	Shoulder	0.10	20	L Foot	0.06
				Whole	1.72

To mimic sweating, distilled water, after being warmed by a heater inside the water tank, was carried via a feed pump to about 140 spouts placed throughout the manikin. The water diffused from the spouts into the fabric “skin” worn by the manikin and spread over its entire body surface. The material used for the fabric “skin” in this experiment was selected to fulfill three conditions: absence of an air layer between the manikin and the fabric “skin,” fast moisture transfer, and saturation of the fabric “skin.”

Experimental conditions

The experimental conditions are presented in Table . Experiments were conducted for each clothing under “dry” and “wet” conditions. The experiment lasted for at least 60 minutes under dry conditions and at least 120 minutes under wet conditions. The measurements were conducted in a stationary state. To verify its reproducibility, the experiment was conducted twice under each condition. After the first dry experiment, all clothing was removed from the manikin; it was then reclothed to perform the second experiment. After the first wet experiment, the clothing was left on the manikin. The second experiment was performed after the clothing was completely dry.

Experimental conditions

Parameters	Units	Dry condition	Wet condition
Air temperature	[°C]	21	34
Relative humidity	[%]	50	40
Air velocity	[m/s]	0.1	0.4
Mean radiant temperature	[°C]	21	34
Skin temperature	[°C]	34	34
Sweating rate	[mL/(m2·h)]	—	400

Dry conditions

A temperature difference between the manikin surface and the ambient air was created to measure the clothing insulation at each body segment. The thermal environmental conditions in the laboratory were 21°C for air and radiation temperature, 50% relative humidity, and 0.1 m/second air velocity. The manikin surface temperature was 34°C at all segments.

Wet conditions

The clothing evaporative resistance was measured at each segment, in a high‐temperature environment. The thermal environmental conditions in the laboratory were 34°C for air and radiation temperature, 40% relative humidity, and 0.4 m/second air velocity. To prevent sensible heat transfer between the manikin and the ambient air, the temperature of all segments was set to 34°C, which was equivalent to the air and radiation temperatures of the ambient air. In addition, because ASTM F2370 and other standards do not provide clear criteria for the sweating rate, we referred to a previous study and used approximately 400 mL/(m²·h) water (sweat), which was enough to keep the fabric “skin” in a state of saturation.

Clothing conditions

The clothing conditions are presented in Table and Figure . The experiment was conducted in two nude conditions —with and without the fabric “skin”— and eight summer clothing conditions. The eight male clothing ensembles were assumed to be used outdoors (En A), at home (En B, C, and D), at the office (En E, F, and G), and at a construction site (En H). The clothes used in the experiment were laundered at least two times before use.

Clothing conditions

Code	Components
Nude 1	No clothing components
Nude 2	Fabric “skin”
En A	Briefs (C), Socks (C and A), T‐shirt (C), Half pants (C), Sneakers (C)
En B	Briefs (C), Undershirt (C), Sports T‐shirts (P), Sports shorts (P)
En C	Briefs (C), Socks (C and A), Polo shirt (C and P), Long pants (C), Sneakers (C)
En D	Briefs (C), Under shirt (C), Long‐sleeved shirt (P and C), Long pants (P and C)
En E	Briefs (C), Socks (C and A), Undershirt (C), Short‐sleeved shirt (C), Long pants (W and P), Belt (L), Shoes (L)
En F	Briefs (C), Socks (C and A), Undershirt (C), Long‐sleeved shirt (C), Long pants (W and P), Belt (L)
En G	Briefs (C), Socks (C and A), Undershirt (C), Long‐sleeved shirt (C), Jacket (W and P), Long pants (W and P), Belt (L), Shoes (L)
En H	Briefs (C), Socks (C and A), Undershirt (C), Work jacket (P and C), Work pants (P and C), Safety shoes (C and A)

Abbreviations: (A), acrylic; (C), cotton; (L), leather; (P), polyester; (W), wool.

Clothing conditions

Measurement parameters

The measurement parameters and the measurement positions are presented in Table and Figure , respectively. In the laboratory, thermometers (ESPEC MIC, RSW‐20S) were used to measure the air temperature and relative humidity at +0.1, 0.6, 1.1, 1.7, 2.2, and 2.7 m above the floor at 10‐minute intervals. A PMV meter (Kyoto Electronics Manufacturing Co., amenity meter AM‐101) was used to measure the air temperature, relative humidity, mean radiation temperature, and airflow at +0.6 m above the floor at 10‐minute intervals. Measurements of the skin surface temperature and heat flux at each segment of the sweating thermal manikin were taken at 1‐minute intervals. In the wet condition, a high‐precision scale (Sartorius, Combics 1 Plus) was used to measure the weight of the clothes before and after the experiment.

Measurement parameters

Parameters	Units	Position	Interval
Air temperature	[°C]	FL + 0.1, 0.6, 1.1, 1.7, 2.2, 2.7 m	10 min
Relative humidity	[%]
Mean radiant temperature	[°C]	FL + 0.6 m
Air velocity	[m/s]
Skin temperature	[°C]	20 body parts	1 min
Heat flux	[W/m2]
Clothing weight	[g]	—	Pre/post measurement

Measurement positions (the units of the values are millimeter). A, Plan view. B, Section view

Calculating thermal properties

The thermal networks between the skin and the ambient air are shown in Figure . The heat transfer between the skin and the ambient air was divided into sensible heat transferred by radiation, conduction, and convection, and latent heat transferred by evaporation. This section describes the methods used to calculate the intrinsic clothing insulation, intrinsic clothing evaporative resistance, and clothing vapor permeation efficiency at specific segments.

Thermal networks between the skin and the ambient air. A, Sensible heat. B, Latent heat

Local intrinsic clothing insulation

At a given segment i, the total clothing insulation R_t,i and boundary insulation R_a,i are expressed as Formulas 1 and 2, respectively, which use the temperature difference (t_s,I − t_o) between the skin and the ambient air, and the amount of heat loss Q_i. The intrinsic clothing insulation R_cl,i is expressed as Formula 3. This formula subtracts the boundary insulation R_a,i per clothing area factor f_cl,i from the total clothing insulation R_t,i. The clothing area factor f_cl,i is calculated using Formula 4. The unit conversion for clothing insulation is performed using Formula 5.[Image Omitted. See PDF][Image Omitted. See PDF][Image Omitted. See PDF][Image Omitted. See PDF][Image Omitted. See PDF]

Local intrinsic clothing evaporative resistance

The clothing evaporative resistance can be calculated using either the mass loss (ML) method or the heat loss (HL) method. The ML method uses the amount of moisture evaporation from the manikin surface and the latent heat of evaporation to calculate the amount of evaporation heat Q_e,whole. In the HL method, equalization of the skin temperature and the operative temperature of the ambient air is used to eliminate sensible heat transfer. Thus, the amount of heat supplied from a manikin segment Q_manikin,i is considered to be the amount of evaporation heat released from that segment Q_e,i. The ML method can only measure the amount of evaporation heat from the whole manikin Q_e,whole and cannot be used to measure the evaporative heat for different locations. By contrast, the HL method uses the amount of heat supplied from each manikin segment Q_manikin,i to calculate the evaporative resistance, making it a suitable method for measuring the heat released from different locations.

When using the HL method, for a given segment i, the total clothing evaporative resistance R_et,i and boundary evaporative resistance R_ea,i are calculated using Formulas 6 and 7, which use the difference in vapor pressures between the fabric “skin” surface and the ambient air (p_s,f,I − p_a), along with the amount of evaporative heat loss Q_e,i. Intrinsic clothing evaporative resistance R_ecl,i is calculated using Formula 8, which is similar to Formula 3. Vapor pressure p is calculated using Antoine's equation, which employs temperature t and relative humidity RH in the form of Formula 9. It should be noted that the experiments were conducted when the fabric “skin” was saturated with moisture, and thus the relative humidity on the fabric “skin” surface was calculated as RH_s,f = 100.[Image Omitted. See PDF][Image Omitted. See PDF][Image Omitted. See PDF][Image Omitted. See PDF]

Methods of correcting local clothing evaporative resistance

To calculate the clothing evaporative resistance using the HL method, isothermal conditions (t_s,f = t_o = t_s) need to be met. However, Wang et al. pointed out that when moisture in the fabric “skin” evaporates, the surface temperature t_s,f decreases, making it difficult to strictly meet isothermal conditions (t_s,f = t_o = t_s). In fact, when the fabric “skin” surface temperature t_s,f differs from the ambient air’s operative temperature t_o and the manikin surface temperature t_s, it creates a nonisothermal state (t_s,f < t_o = t_s), which causes sensible heat transfer. Isothermal conditions (t_s,f = t_o = t_s) are only possible with some manikins that allow the fabric “skin” surface temperature t_s,f to be controlled, such as the Walter sweating thermal manikin. However, the Walter sweating thermal manikin is not divided into multisegments and thus is not suitable for measurements at different locations on the body, as done in the present study.

Therefore, when using the sweating thermal manikin used in the present study or another manikin, the decrease in fabric “skin” surface temperature t_s,f,i that accompanies a sensible heat transfer needs to be taken into consideration to generate isothermal conditions (t_s,f = t_o = t_s) and to accurately measure the total evaporative resistance R_et,i. In the present study, we applied the method reported by Lu et al. to correct the local clothing evaporative resistance.

In a nonisothermal state (t_s,f < t_o = t_s), the amount of evaporative heat loss Q_e,i at a segment i can be calculated using Formula 10. This formula uses the amount of heat supplied from the manikin Q_manikin,i and the amount of heat transferred from the ambient air to the fabric “skin” surface Q_env,i. The amount of heat transferred from the ambient air to the fabric “skin” surface Q_env,i can be calculated using Formula 11, which uses the difference between the ambient air’s operative temperature and the fabric “skin” surface temperature (t_o − t_s,f,i), along with the total clothing insulation in a wet state R_t,wet,i.[Image Omitted. See PDF][Image Omitted. See PDF]

Several formulas have been proposed for estimating the fabric “skin” surface temperature t_s,f,i, present in Formula 11, using the amount of heat supplied from the manikin at a segment Q_manikin,i. In the present study, we used the formula proposed by Wang et al., which is given here as Formula 12. The applicable range of this formula is 25°C ≤ t_s,minikin ≤ 34°C, which makes it suitable for this study. The accuracy and validity of this formula was verified by Ueno et al. and others.[Image Omitted. See PDF]

When sweating thermal manikins are used to measure the clothing evaporative resistance, the clothes are often found to be wet after the measurements have been taken. Air has a higher thermal conductivity than water, and clothes have been shown to have less clothing insulation when wet as compared to when they are dry. In other words, in a wet state, the total clothing insulation R_t,wet,i at a segment i can be expressed using Formula 13. The reduction in total clothing insulation r_t,i in Formula 13 can be calculated with Formula 14, using the amount of moisture in the clothes w_t,i. The amount of moisture in the clothes w_t,i, which was measured after the experiment, was confirmed to be within the applicable range of Formula 14 (0 < w_t,i < 900). The present study measured the clothing evaporative resistance at different segments. Therefore, the moisture in the clothes at a certain segment w_t,i was calculated as the amount of moisture in all the clothes w_t,whole weighted by the area of that segment. That is, the moisture in a certain segment w_t,i was calculated using Formula 15, which multiplies the amount of moisture in the clothes w_t,whole by the ratio of the surface area of that segment to the whole area A_i/ A_whole.[Image Omitted. See PDF][Image Omitted. See PDF][Image Omitted. See PDF]

Therefore, the amount of evaporative heat loss Q_e,i in Formula 10 was calculated using Formula 16, which uses Formulas 11‐15. Generally, the amount of evaporative heat loss Q_e,i is larger than the heat supplied from the manikin Q_manikin,i.[Image Omitted. See PDF]

Substituting Formulas 8, 12, and 16 into Formulas 6 and 7 gives Formulas 17 and 18, which are used to calculate the total clothing evaporative resistance R_et,i and the boundary evaporative resistance R_ea,i.[Image Omitted. See PDF][Image Omitted. See PDF]

Clothing vapor permeation efficiency by segment

For a segment i, clothing vapor permeation efficiency i_cl,i was calculated using Formula 19, which considers intrinsic clothing insulation R_cl,i, clothing evaporative resistance R_ecl,i, and the Lewis ratio L_R. We used the fixed value of 16.5 K/kPa for the Lewis ratio L_R.[Image Omitted. See PDF]

Results

The following sections present the results are of the measurements that were performed 10 minutes before the end of the experiment.

Thermal environment

The thermal environment measurements (mean ± SD) are given in Table . The thermal environment in the laboratory was generally maintained at the settings used in both, dry and wet conditions. The upper and lower temperature differences were about 0.1°C for both conditions, indicating that a uniform thermal environment was developed. Similarly, the manikin surface temperatures for all the segments were maintained at the settings used in both the conditions.

Thermal environment measurements (Mean ± SD)

Parameters	Units	Dry condition	Wet condition
Air temperature	[°C]	20.8 ± 0.1	33.7 ± 0.1
Relative humidity	[%]	50 ± 1.5	41 ± 0.4
Air velocity	[m/s]	0.1 ± 0.0	0.4 ± 0.0
Mean radiant temperature	[°C]	20.9 ± 0.3	33.9 ± 0.1
Skin temperature	[°C]	34.0 ± 0.0	34.0 ± 0.0

Local thermal clothing properties

The local thermal clothing properties are given in Table , where values are expressed as the mean of two measurements. Measurements of limbs such as the arm and foot are the mean of the left and right measurements. The repetition error was 5% or less for all segments in both conditions, indicating high reproducibility.

Local thermal clothing properties

Ensemble code	Parameter	Unit	Face	Head	Upper arm	Arm	Hand	Chest	Shoulder	Stomach	Back	Hip	Thigh	Calf	Foot	Whole
Nude1	Ia	[clo]	0.54	0.71	0.66	0.68	0.63	0.67	0.70	0.84	0.65	0.92	0.70	0.66	0.57	0.70
Nude2	Icl	[clo]	0.67	0.79	0.75	0.77	0.76	0.76	0.79	0.86	0.99	1.16	0.84	0.75	0.72	0.82
Rea	[(m2·Pa)/W]	7.5	16.8	13.3	7.5	6.1	10.0	16.0	9.0	20.0	24.0	9.9	7.8	5.9	13.4
En A	Icl	[clo]	0.01	0.00	0.39	0.00	0.00	0.50	0.51	1.28	1.13	1.78	0.40	0.07	0.62	0.53
Recl	[(m2·Pa)/W]	0.0	0.0	7.3	0.0	1.7	6.5	11.6	32.4	39.7	49.4	6.0	2.3	18.2	13.4
icl	[‐]	0.00	0.00	0.51	0.00	0.00	0.72	0.42	0.37	0.27	0.34	0.63	0.26	0.32	0.37
En B	Icl	[clo]	0.00	0.00	0.48	0.00	0.00	0.90	0.78	2.45	1.76	2.10	0.59	0.00	0.01	0.70
Recl	[(m2·Pa)/W]	0.0	0.0	6.2	0.7	0.7	9.8	17.1	40.9	49.2	51.4	10.6	1.1	3.5	14.5
icl	[‐]	0.00	0.00	0.73	0.00	0.00	0.87	0.43	0.56	0.34	0.39	0.52	0.03	0.03	0.46
En C	Icl	[clo]	0.00	0.02	0.34	0.00	0.00	0.52	0.37	1.23	0.97	1.33	0.43	0.56	0.65	0.54
Recl	[(m2·Pa)/W]	0.0	0.0	3.4	0.0	0.0	5.2	10.2	30.3	26.1	31.1	4.3	9.3	25.0	11.3
icl	[‐]	0.00	0.00	1.00	0.00	0.08	0.95	0.34	0.38	0.35	0.40	1.00	0.56	0.24	0.45
En D	Icl	[clo]	0.01	0.00	0.98	0.78	0.03	1.20	0.98	2.80	1.65	2.42	0.84	0.62	0.02	1.01
Recl	[(m2·Pa)/W]	0.0	0.0	19.1	15.2	4.0	13.1	21.0	56.1	43.6	53.6	15.1	15.9	2.7	20.9
icl	[‐]	0.00	0.00	0.49	0.48	0.05	0.87	0.44	0.47	0.36	0.43	0.52	0.37	0.07	0.45
En E	Icl	[clo]	0.00	0.01	0.54	0.00	0.00	0.80	0.77	1.66	1.40	1.44	0.54	0.64	0.99	0.72
Recl	[(m2·Pa)/W]	0.0	0.0	9.7	0.0	0.9	9.8	12.2	32.2	27.0	37.1	8.8	14.4	47.3	16.0
icl	[‐]	0.00	0.00	0.52	0.00	0.02	0.77	0.59	0.49	0.49	0.37	0.58	0.44	0.20	0.42
En F	Icl	[clo]	0.00	0.00	0.82	0.60	0.01	0.86	0.86	1.61	1.45	1.31	0.65	0.66	0.64	0.77
Recl	[(m2·Pa)/W]	0.0	0.0	17.5	9.2	2.5	15.8	19.0	33.9	36.0	40.4	8.6	14.2	51.5	19.4
icl	[‐]	0.00	0.00	0.45	0.62	0.03	0.51	0.43	0.45	0.38	0.31	0.70	0.48	0.12	0.38
En G	Icl	[clo]	0.00	0.03	1.80	1.54	0.15	2.13	1.76	3.65	2.28	2.06	0.87	0.69	0.97	1.39
Recl	[(m2·Pa)/W]	0.0	0.0	39.3	25.6	4.5	27.3	33.2	59.0	56.4	50.0	14.5	12.8	59.3	29.1
icl	[‐]	0.00	0.00	0.41	0.53	0.27	0.69	0.48	0.56	0.38	0.38	0.53	0.41	0.15	0.39
En H	Icl	[clo]	0.00	0.00	0.84	0.71	0.08	1.25	0.87	2.09	1.39	0.93	0.47	0.59	1.12	0.80
Recl	[(m2·Pa)/W]	0.0	0.0	21.7	12.3	2.9	28.1	23.8	52.9	42.5	20.4	6.8	10.0	58.5	20.6
icl	[‐]	0.00	0.00	0.37	0.54	0.24	0.42	0.34	0.37	0.31	0.43	0.65	0.58	0.18	0.37

Boundary insulation I_a in the nude state Nude1 was 0.70 clo for the whole body. This value is consistent with the boundary insulation values for calm airflow environments that are generally reported in the environmental standards of the Architectural Institute of Japan and in ISO 9920. In addition, boundary evaporative resistance R_ea in the state Nude2, where the fabric “skin” was used, was 13.4 (m²·Pa)/W for the whole body. This is similar to the evaporative resistance of 14.2 (m²·Pa)/W reported in a previous study. These findings verify the validity of the whole‐body measurements in nude conditions, confirming that the results of the present study are similar to those of previous studies. Moreover, in clothed conditions, the intrinsic clothing insulation I_cl,i and intrinsic clothing evaporative resistance R_ecl,i values for segments where the clothing overlapped (such as the chest, back, and pelvis) were higher, while those for nude segments (such as the head, neck, and hand) tended to be lower, thus showing that the measurements taken for the segments reproduced actual clothing conditions.

The range of the total clothing vapor permeation efficiency i_cl,whole was 0.37 to 0.46, which was similar to the measurements reported by McCullough et al. and Oohori et al. When examined by segment, intrinsic clothing evaporative resistance R_ecl at the feet of En E, En F, and En G (all of which wore leather shoes) and En H (which wore safety shoes) was about twice the values of En A and En C, both of which wore sneakers. Moreover, the clothing vapor permeation efficiency i_cl measurement values for En E, En F, En G, and En H were lower than those for En A and En C, confirming material‐based differences in vapor permeation. Furthermore, when the manikin was wearing shoes, the clothing vapor permeation efficiency i_cl values of the foot were less than the values for the whole body i_cl,whole. In all clothing conditions (En B, En D, En E, En F, En G, En H, etc.), intrinsic clothing insulation I_cl,i and intrinsic clothing evaporative resistance R_ecl,i value were higher for surface areas where the clothing overlapped (such as the chest, stomach, back, shoulder, and hip) as compared to the resistance values for the whole body. On the stomach, where the lower and upper body clothing overlapped, the measurement values were about twice the values of whole‐body intrinsic clothing insulation I_cl,whole and intrinsic clothing evaporative resistance R_ecl,whole.

The clothing vapor permeation efficiency i_cl,i values on the upper arm, chest, and thigh for En C were higher as compared to the values for other clothing conditions. We think this is because the clothes in En C were for a slim body type, and thus the moisture transfer conditions were different from those in the other types of clothing. Normally, moisture evaporates from the fabric “skin” surface and passes through the clothing, to the ambient air. However, the large amount of contact between the fabric “skin” and the clothing in En C left no space between the fabric “skin” and the clothing. Thus, much of the water discharged from the manikin evaporated from the outer clothing surface and not from the fabric “skin” surface. This likely reduced the evaporative resistance. Therefore, when using sweating thermal manikins in experiments, it is important to consider the size and looseness of the clothes with respect to the manikin.

The measurements performed in the present study showed that for all clothing conditions, there were large differences between segments with regard to intrinsic clothing insulation I_cl,i, intrinsic clothing evaporative resistance R_ecl,i, and clothing vapor permeation efficiency i_cl,i, depending on the type of clothing material and how the clothing overlapped. Therefore, it is necessary to consider the thermal clothing properties at different locations of the body when evaluating factors such as human local physiology and thermal comfort. The results of the present study can be applied to location‐based evaluations, such as predictive models for human physiology and thermal comfort at specific locations on the body.

Conclusion

The present study used a sweating thermal manikin to measure the intrinsic clothing insulation and clothing evaporative resistance at different segments, using eight summer clothing ensembles. We used the results to calculate the clothing vapor permeation efficiency at each segment.

There are two methods for calculating the clothing evaporative resistance: ML and HL. We described the properties of both methods and analyzed why the HL method is better suited for location‐based measurements. We also described a method for correcting these calculations.

Our measurements of the clothing thermal properties for the whole body were consistent with the results of previous research, confirming the validity of the present study’s results. In particular, the range of the clothing vapor permeation efficiency was 0.37 to 0.46 for all clothing ensembles, which is similar to the values from previous reports. However, depending on the clothing material and the extent of overlap, the intrinsic clothing insulation, intrinsic clothing evaporative resistance, and clothing vapor permeation efficiency measurement values of some segments were about twice the whole‐body values, thus demonstrating the existence of large differences between segments. Therefore, when making detailed, location‐based evaluations of factors such as human local physiology and thermal comfort, it is necessary to consider the clothing thermal properties of each location instead of treating the whole body uniformly.

The present study indicated that in clothing conditions such as En C, where there is a large amount of contact between the fabric “skin” and the clothes, the discharged water evaporated not only from the fabric “skin” surface but also from the outer clothing surface as well. This may have a major impact on the measurements of clothing evaporative resistance. Therefore, when using sweating thermal manikins in experiments, it is important to consider the size and looseness of the clothes with respect to the manikin.

Acknowledgments

This work was supported by JSPS KAKENHI (grant number: 19H00797) and the Fund Prepared Research of Wind Engineering Research Center of Tokyo Polytechnic University (agenda no. 18185001).

Disclosure

The authors have no conflict of interest to declare.

Symbols

• A: Body surface area [m²].
• L_R: Lewis ratio [K/ kPa] = 16.5.
• Q: Skin‐to‐environment heat loss [W/m²].
• Q_e: Amount of evaporative heat loss on the fabric “skin” [W/m²].
• Q_env: Amount of heat transferred from the ambient air [W/m²].
• Q_manikin: Amount of heat supplied by the manikin [W/m²].
• R: Clothing insulation [(m²·K)/W] = 0.155 × I [clo].
• R_a: Boundary insulation (when nude) [(m²·K)/W] = 0.155 × I_a [clo].
• R_cl: Intrinsic clothing insulation [(m²·K)/W] = 0.155 × I_cl [clo].
• R_t: Total clothing insulation (when clothed) [(m²·K)/W] = 0.155 × I_t [clo].
• R_ea: Boundary evaporative resistance (when nude) [(m²·kPa)/W].
• R_ecl: Intrinsic clothing evaporative resistance [(m²·kPa)/W].
• R_et: Total clothing evaporative resistance (when clothed) [(m²·kPa)/W].
• RH_a: Relative humidity of the ambient air [%].
• RH_s,f: Relative humidity of the fabric “skin” surface [%].
• f_cl: Clothing area factor [‐].
• i_cl: Clothing vapor permeation efficiency [‐].
• p_a: Water vapor pressure in the ambient air [kPa].
• p_cl: Water vapor pressure in at the outer clothing surface [kPa].
• p_s: Water vapor pressure in at the skin surface [kPa].
• p_s,f: Water vapor pressure in at the fabric “skin” surface [kPa].
• r_t: Reduction in total clothing insulation [%].
• t: Temperature [°C].
• t_a: Air temperature [°C].
• t_cl: Outer clothing surface temperature [°C].
• t_o: Operative temperature [°C].
• t_s: Skin surface temperature [°C].
• t_s,f: Fabric “skin” surface temperature [°C].
• w_t: Amount of moisture in the clothes [g].

Suffixes

• cl: When clothed.
• i: Manikin segment number.
• nude: When nude.
• wet: Wet state.
• whole: Whole body.