Clothing heat and humidity performance test system—sweating and warming dummyRelease time: 2015-07-17 10:40
In cool and cold climates, the human body maintains the internal and external thermal balance mainly through convection, conduction, and radiation. At this time, the cold-proof and warm performance of clothing is the main factor to maintain the human thermal balance; in hot summer, when the external environment temperature and the human body When the surface temperature is equal or even higher than the surface temperature of the human body, the only way for the human body to dissipate heat is through the evaporation of sweat. At this time, the moisture permeability and ventilation performance of the clothing are the decisive factors for maintaining the body's thermal balance in the thermal environment.
The application of dummy technology to study the heat transfer between human and environment is an advanced technology that has been adopted in many countries. The advantages are high accuracy, good repeatability, and the ability to test clothing comfort performance under extreme environmental conditions that real people cannot test. At present, the dummy that has been developed and used in the research of clothing comfort performance mainly includes the warm body dummy and the sweat dummy. The warming dummy can only simulate the thermal physiological response of the human body (such as skin temperature, heat emission, etc.) in the non-evaporative heat dissipation range, and is used to test and evaluate the thermal performance of clothing in cold environments, while for evaporative heat dissipation, only through sweating The dummy simulates the heat-moisture exchange between the human body, clothing and the environment in order to test and evaluate the heat-moisture transfer performance and the comfort of wearing heat and humidity in the thermal environment. Therefore, the research on sweating dummy has become a research hotspot in the field of clothing ergonomics. . The sweating dummy has been studied abroad since 1988. At present, the units that have successfully developed sweating dummy include the Finnish Technical Research Center and the Tokyo Bunka Women's University. The common feature of these two sweating dummy is that they can simulate the human body. In the state of gaseous sweat, the heat and moisture transfer performance of occupational protective clothing can only be tested in cold or comfortable environments .
1 Sweating dummy system composition
1.1 Overall composition of sweating dummy The sweating dummy system mainly includes five parts: dummy body, interface circuit, dummy thermal control device, dummy sweat control device and application software. The block diagram is shown in Figure 1. The sweating dummy's body is based on the measured three-dimensional data of Chinese male soldiers, and a digital human body model is used to quickly develop a technical route to develop a dummy model.A platinum resistance temperature sensor and a multi-channel direct-flow control power supply are used as the core to form a dummy thermal control system. Detection of the surface temperature of the dummy and heating control of the dummy; the core is composed of a precision peristaltic pump and a high-precision weighing mechanism to form a dummy sweat control system, which simulates human sweat according to different test modes; Visual Basic modular programming language is The platform creates a sweat dummy control and management system software to realize real-time detection of multiple signals and regulation of heat and humidity of the dummy.
1.2 Sweating dummy shell structure and sweating mechanism According to real-life test data and literature data under thermal environment , when the person is sitting in a quiet environment under thermal environment, the human skin temperature is basically stable at 32.3 ~ 35.5 ℃, and the human body sweats The volume is about 60 ~ 200mL (/ m · 2 h) (body surface area: 1.7m2). When the average skin temperature of the human body is 35 ℃ and the core temperature is 38 ℃, the maximum sweat volume of the human body is about 400 mL (/ m2 · h ). Based on this, the stable skin temperature of the sweating dummy was set to 34 ° C, and the sweating level was controlled at 60 ~ 400 mL (/ m2 · h). According to the sweating dummy test system to stabilize the skin temperature and the simulated sweating level, several asymmetric hydrophilic polytetrafluoroethylene laminated films were selected for the sweating test test. Finally, 100% cotton fabric was selected as the artificial skin. Inner layer, asymmetric hydrophilic polytetrafluoroethylene film as the outer layer of artificial skin, to ensure the rapid absorption and diffusion of moisture, and simultaneously have the dual functions of liquid sweat and gaseous sweat; under different sweating rates, the wet area of a single sweat gland With the change of time, the design principle of an 80 cm2 ellipse as the wet area of a sweat hole was determined. A total of 160 sweat units were arranged on the dummy surface. The cross section of the sweating unit is shown in Fig. 2. The dummy has 8 layers of structure from the inside to the outside, and the sweat passes through 2 to 6 layers to reach the inner layer of the artificial skin, and is quickly absorbed and diffused by the artificial skin. The asymmetric hydrophilic polytetrafluoroethylene film selected in this study is a very thin polymer film. A large number of micropores with a diameter of 0.3 to 1.5 μm are distributed on the film. The diameter of water vapor molecules is generally 0.000. 4 μm, the diameter of the mist is generally 20 ~ 100 μm, so the diameter of the micropores of the asymmetric hydrophilic polytetrafluoroethylene film is much larger than the water vapor molecules, and smaller than the diameter of the mist and water molecules. At the same time, water vapor can pass through the film smoothly, and water droplets are trapped in the holes and fixed by the surface tension. When it is necessary to simulate the human body's liquid sweat, the pressure of the sweat pump is adjusted to destroy the surface tension of the water droplets, allowing the liquid water droplets to penetrate At the same time, because the film is asymmetrically hydrophilic, it can simulate human body sweating liquid. The sweating dummy has an 8-layer composite structure, and a new type of hydrophilic polytetrafluoroethylene laminated fabric is selected as the simulated skin to realize the integrated design of the heating circuit, temperature measurement circuit and sweating circuit of the sweating dummy. With dual functions of liquid sweat and gaseous sweat.
2 Basic Principles and Main Features of Sweating Dummy System According to human physiological theory, the human body and the external environment exchange heat through non-evaporative heat dissipation (conduction, convection, radiation) and evaporative heat dissipation.The basics of the sweating dummy test system The principle is to place a sweating dummy in an artificial climate chamber. The dummy's skin surface temperature control model and sweating control model are used to regulate the dummy's skin temperature and sweating volume.The thermal control and sweating volume are stabilized at a certain level to make the dummy -The clothing-environment is in a dynamic thermal-humidity equilibrium state.At this time, the thermal resistance, moisture resistance, and thermal resistance of the clothing can be obtained from the surface temperature of the dummy, the ambient temperature, the heat supply of the dummy, the amount of sweat, and the amount of evaporation. The moisture permeability index and other indicators are used to evaluate the heat and moisture transfer performance of the garment.
The human body is a complex giant system. The sweating dummy can only test and evaluate the heat and moisture transfer performance of clothing. Based on ergonomic principles and combining theories of physiology and clothing comfort science, the heat of the clothing system can be simulated as realistically as possible. During the wet transfer process, the sweat dummy test system has the following characteristics:
a. Simulate the transfer of heat and moisture from the surface of human skin through clothing to the environment.
b. The fake human body conforms to human anatomy.
c. The dummy is divided into 12 independent heating control sections, and the shoulder, hip, and ankle joints can be moved.
d. The surface temperature and sweat rate of the dummy's skin are controlled by the computer in real time.
3 Sweating dummy test mode and evaluation index In order to make the sweating dummy test system effectively test and evaluate the moisture permeability and breathability of different garments, and better serve the scientific research, according to the needs of scientific research work, the sweating dummy was studied. Three test modes, namely constant temperature and constant humidity test mode, constant temperature and constant sweat rate test mode, and simulated human test mode.
3.1 Constant temperature and humidity test modeThe constant temperature and humidity test mode is to keep the surface temperature and wetness of the sweating dummy skin constant, and obtain the thermal resistance, moisture resistance, and moisture permeability index of the clothing. It is mainly used for testing and evaluating clothing. Hot and humid performance. Table 1 is the wet resistance and moisture permeability index measured when the sweating dummy is naked and wearing different test clothing. It can be seen from Table 1 that the wet resistance and moisture permeability index measured when the sweating dummy is naked and wears different clothing have good repeatability, and can effectively distinguish the heat and moisture transfer performance of different clothing.
3.2 Constant temperature and constant sweat rate test modeThe constant temperature and constant sweat rate test mode is to make the surface temperature and sweat rate of the sweating dummy constant, and to obtain the modified thermal resistance value of clothing under sweating conditions, which is mainly used to compare different clothing in different performance. The process of reducing the thermal insulation performance of clothing when the amount of sweat is the change of thermal resistance value, provides a scientific basis for the structural design of clothing and the selection of fabrics, as well as improving the thermal and moisture protection performance of clothing. Table 2 shows the test results of the sweatpants and camouflage suits when the sweat rate is 50 g (/ h · m2), 100 g (/ h · m2), and 200 g (/ h · m2).
3.3 Simulated real-life test mode The simulated real-life test mode is to change the surface temperature of the sweating dummy with the temperature of the test environment and the amount of sweat to change with the temperature of the skin surface, that is, during the test, the human sweating and skin obtained based on the real-life test The relational equation of surface temperature enables the perspiration rate of the dummy to be supplied according to the skin surface temperature, and the heat supply is divided into two parts: dry heat dissipation and evaporative heat dissipation. The evaporative heat dissipation part is supplied according to the heat required to evaporate sweat. This test method can obtain the human body's equilibrium skin temperature, heat and humidity sensation index and evaporation heat dissipation index under different test conditions.
4 Test and Evaluation of Clothing Thermal and Moisture Performance Using the sweating dummy system, the thermal and humid performance of current military uniforms, public security raincoats, comfortable underwear, chemical protection clothing, and SARS protective clothing was tested. The test results are shown in Table 3. The current summer clothing is a polyester special deformed filament fabric newly developed by the General Military Quarters, which has good water transmission and fast drying properties. The moisture permeability index measured by the sweating dummy is 0.480. The index is 0.53). It has excellent thermal and wet comfort. The polyester-cotton camouflage training clothing is mainly used by military personnel for training activities or work wear. It requires abrasion resistance and good moisture permeability. As can be seen from Table 3, its moisture permeability index is 0.430, and its thermal and wet comfort is good. For the several public security raincoats in Table 3, in comparison, the PTFE composite polyester raincoat has the smallest thermal and wet resistance, the largest moisture permeability index, and the best thermal and wet performance, while the PVC and polyvinyl chloride raincoats have the best thermal and wet resistance. The largest, the moisture permeability index is almost zero, the worst heat and humidity performance, it is recommended to use PTFE composite polyester fabric public security raincoat. The comfortable knitted suit is a comfortable fabric developed by a textile research institute. Compared with the ordinary polyester-cotton knitted suit developed by the institute, the newly developed comfortable knitted suit has a much lower wet resistance than the ordinary polyester-cotton knitted suit. The wet index is larger than the latter, showing good thermal and wet comfort. Among the two types of chemical protective clothing, the standard type breathable chemical protective clothing uses surface carbon treatment, while the hot zone type chemical protective clothing uses carbon fiber fabric, and the thermal resistance, moisture resistance and moisture permeability index of the two types of chemical protective clothing are comprehensively compared. , The heat and humidity comfort performance of the hot zone type breathable chemical protective clothing is slightly better than that of the standard type breathable chemical protective clothing. The two types of SARS protective clothing are protective clothing worn by medical personnel during SARS. From the test results, the moisture resistance of breathable SARS protective clothing is significantly lower than that of standard SARS protective clothing, and the moisture permeability index of the former is significantly higher than the latter. Medical staff also felt that the thermal and wet comfort of breathable SARS protective clothing was better than that of the latter, which was consistent with the test results of the sweating dummy. The above sweating dummy test test shows that the sweating dummy test system can effectively distinguish the thermal and wet comfort performance of different garments.
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