| Author: | Chen, Yisong |
| Title: | The development of a perspiring fabric manikin for the evaluation of clothing thermal comfort |
| Degree: | Ph.D. |
| Year: | 2003 |
| Subject: | Clothing and dress -- Physiological aspects Textile fabrics -- Physiological aspects Hong Kong Polytechnic University -- Dissertations |
| Department: | Institute of Textiles and Clothing |
| Pages: | xviii, 142, 23 leaves : ill. ; 30 cm |
| Language: | English |
| Abstract: | In modern society, clothing is a necessity of human being not only for aesthetics but for keeping comfort Clothing comfort includes many aspects such as freedom of body movement, tactile and thermal comfort. Among them, thermal physiological comfort is a primary one since clothing is intended to be worn in various environmental conditions. To quantify and accurately evaluate the properties of clothing important to thermal comfort is critical to functional clothing design and end use. Thermal manikins are widely recognized as the most desirable method for the measurement of clothing properties related to thermal comfort due to its objectivity, reproducibility and lower cost in comparison with direct tests on human subjects. However, simulation of perspiration in thermal manikins remains a challenge, despite of the considerable research efforts around the world since the first dry copper manikin was developed in 1947 (Holmer 1999). The early "sweating" manikin was in fact a dry manikin covered with wet hydrophilic underwear, on which water was sprayed (Fonseca 1970). Recently developed sweating manikins in Finland (Meinander 1992) and Switzerland (Richards 2001) were made of rigid copper or plastic materials. Tiny holes were drilled on the surface of these manikins, through which water was supplied to simulate sweating. "Sweating" only occurred at localized spots having the water supplying holes, but not the entire the skin surface. Without the report of sufficient experimental data, the reliability of these sweating manikins remains to be questionable. Due to the limitations of existing manikins (including the recent sweating manikins (Meinander 1992)), the measurement of the two primary clothing parameters: thermal insulation R, (or Clo value) and evaporative resistance Re (or Im index), had to carried out in two steps. The two-step method assumed that (1) the thermal insulation values measured on a dry manikin equal to that measured on a sweating manikin and (2) the relative humidity at the skin surface, when the manikin was sweating, was consistently kept at 100% during the entire period of sweating simulation. These two assumptions could however result in considerable errors in the measurements, which was not considered in the previous research publications. The novel perspiring manikin developed in this project is the world first perspiring manikin made of mainly flexible materials: water and breathable fabric, and it can simulate body heat generation and perspiration. It has following unique features: (1), its body is fully filled with water and its fabric "skin" shaped the body similar to a real person; (2), its water circulation system inside body is analogous to the human body's blood circulation system, which distributes heat generated in the center of the trunk to the head and limbs; (3), its "skin" was made of a breathable fabric, and perspiration can be simulated by water vapour transmission through its tiny pores in the breathable fabric; (4), the thermal insulation value Rt and evaporative resistance Re can be measured simultaneously, i.e. in one single step; (5), the "skin" can be changed to different versions to simulate different perspiration, depending on the breathability of the fabric "skin"; (6), the body is flexible with soft touch feel; (7), "walking" can be simulated by pulling and pushing its arms and legs through an external mechanism; (8), the fabric manikin can be constructed with relatively low cost, in comparison with the extremely high cost for the construction of other types of manikins. Owing to the unique design of our manikin, the evaporative resistance can be determined without the need of assumption of 100% relative humidity at the outer surface of the "skin". It can be determined from the total resistance including the skin minus the resistance of the "skin". In determining the total evaporative resistance including the "skin", the vapour pressure at the inner surface of the "skin", where the humidity was constantly 100%, was used. The evaporative resistance of the "skin" was pre-determined. This also avoided the common difficulty in measuring the humidity at the skin surface. The novel manikin has been used to test clothing ensembles in a standard atmosphere of 20 C and 65% RH. It was found that moisture accumulations take place within clothing when the manikin is perspiring. The amount of moisture accumulation depends on the materials and construction of clothing assembles. It takes about 12 hours for the moisture accumulation to stabilize within clothing. To obtain reliable results, measurements should be taken after the moisture accumulation has been stabilized. This finding suggests that the validity of test results, obtained after the clothing ensembles were put on for just one to two hours by previous researchers, is questionable. Following the established experimental procedure, the manikin was used to measure the heat loss, evaporative water loss, thermal insulation, and evaporative resistance of the nude manikin and 12 clothing ensembles. The results were found to be highly reproducible. The coefficients of variation are generally less than 5%. The experimental results from the novel manikin are also comparable to those reported by previous workers. The present investigation has also for the first time examined the effect of heavy perspiration or sweating on the clothing thermal insulation. The clothing thermal insulation values measured when the manikin had little perspiration (with a lowly breathable "skin") and when it had heavy perspiration (with highly breathable "skin") were compared and analyzed. The study revealed that the clothing thermal insulation during heavy perspiration is significantly less than that with low perspiration. The differences varied from 2-8%, related to the increased moisture accumulation within clothing. From this study, it is believed that previously published results of clothing thermal insulation and evaporative resistance, obtained with the conventional two-step measurement method, may contain considerable error and some adjustments may be necessary in applying the clothing thermal insulation measured on a dry manikin to a sweating condition. From the findings of this work, it is believed that the "after chill" effect of wearers after heavy exercise may not only be caused by the heat absorption due to desorption and evaporation of water within clothing, but also due to the reduced clothing thermal insulation. The effect of garment fitting has long been recognized. Nevertheless, no systematic experimental investigations had been carried out to quantify such effect. In this work, fifteen garments were made of 3 types of fabrics in different sizes and tested on the perspiring fabric manikin under no wind (v = 0.5+-0.3 m/s) and windy condition (v = 2.0+-0.5 m/s). It was found that thermal insulation and evaporative resistance of clothing worn on a standing manikin increases generally with the increase of garment sizes when wind velocity was up to 2.0 m/s. When garment size increases from S to XXL, the increase of clothing thermal insulation and evaporative resistance initially increase more steeply, then levels off. The magnitude of increases found in our work was similar to those reported previously. Base on the experimental results, the development of the novel perspiring fabric manikin was successful and we believe it has important benefit clothing research, industry or consumers. |
| Rights: | All rights reserved |
| Access: | open access |
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