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Verification of Thermal Models in the Design of Personal Protective Equipment Against Cold

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Verification of Thermal Models in the Design of Personal Protective Equipment Against Cold IOP Conference Series: Materials Science and Engineering PAPER • OPEN ACCESS Verification of thermal models in the design of personal protective equipment against cold To cite this article: I V Cherunova et al 2021 IOP Conf. Ser.: Mater. Sci. Eng. 1029 012035 View the article online for updates and enhancements. This content was downloaded from IP address 170.106.202.8 on 25/09/2021 at 06:00 Dynamics of Technical Systems (DTS 2020) IOP Publishing IOP Conf. Series: Materials Science and Engineering 1029 (2021) 012035 doi:10.1088/1757-899X/1029/1/012035 Verification of thermal models in the design of personal protective equipment against cold I V Cherunova1,2*, M P Stenkina1, N V Kornev2 1Department of Design and technology, Don State Technical University, Shakhty, Russia 2 Chair of Modeling and Simulation, University of Rostock, Rostock, Germany *Corresponding author: [email protected] Abstract. In the article research results are presented, which aim to verification of thermal models in the design of personal protective equipment against cold. Under the effect of wind, movement, and pressure of the human being himself on the clothing, the design thermal resistance of the clothing decreases and does not provide the stable human comfort. To eliminate such risks, special heated garments are being developed, which are fitted with electric batteries.The basis for such a development is the mathematical model of the system "Human- Clothes-Environment", which allows to establish the main parameters of the heating intensity of each individual section of the clothing, taking into account the overall functioning of the system. Such a model has been developed. The problems of verification of thermal models for designing if the clothing are associated with the assessment of experimental data on the parameters of the system under study. A structure for the formation of a method for experimental verification of the models of thermal protective clothing has been developed. Design of experimental protective clothing against cold with heating based on a mathematical model has been developed.The ratio of feelings of thermal comfort and temperature under heated clothing of small thickness under wind load, cold and lack of physical activity has been installed. 1. Introduction The prospects for the development of the northern regions, offshore, and maritime territories require great attention to the safety and comfort of human labor in the regions with the severe cold climate. There are scientific and technical designs of passive protective clothing, which is intended for the specified cold conditions [1]. All of them are based on the design parameters of the thickness of clothing made from a set of textile materials with certain characteristics of thermal conductivity [2,3]. Under the effect of wind, movement, and pressure of the human being himself on the clothing and under the changes in the humidity of the environment, the design thermal resistance of the clothing decreases and does not provide the stable human comfort [4]. To eliminate such risks, special heated garments are being developed, which are fitted with electric batteries [5]. As a rule, in case of lack or excess of heat under the clothes, the vest heating control is performed directly by a human, which reduces the convenience of the clothes use. An alternative solution is the active control of the thermal balance of the under-clothing space based on the information about the temperature distribution over the surface of the human body [6,7]. Wherein, the clothes heating control system is to be based on the knowledge about the aerodynamic and thermodynamic interactions between the human body, protective clothing, and the environment [8]. The basis for such a development is the mathematical model of the system "Human- Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd 1 Dynamics of Technical Systems (DTS 2020) IOP Publishing IOP Conf. Series: Materials Science and Engineering 1029 (2021) 012035 doi:10.1088/1757-899X/1029/1/012035 Clothes-Environment", which allows to establish the main parameters of the heating intensity of each individual section of the clothing, taking into account the overall functioning of the system [9]. Such a model has been developed [10]. It is characterized by a large number of factors, variable conditions, and the complexity of the mathematical apparatus, and therefore it requires special attention to the processes of verification of the model and its results [11]. The problems of verification of thermal models for designing if the clothing are associated with the assessment of experimental data on the parameters of the system under study. Experimental studies of the system, with taking into account the technical and biological components, require special complex conditions and techniques [13], which is subject to new R & D studies. 2. Theoretical part There are a number of up-to-date ways to ensure and verify that the thermal protection of the clothing is sufficient for expected cold conditions. They are used to verify the models in the designing of protective clothing. The traditional criterion for ensuring the thermal protection of clothing is based on the formation of thermal insulation of a package of clothing materials, in which no additional heating is provided [14]. This method applies to special clothing for protection from the cold for employees of various professions who work in open areas and in unheated premises. The special clothing is designed, fabricated, and tested taking into account the operation in various climatic regions. Using the example of Russia, special climatic regions are distinguished, for which characteristic average climate parameters are established (temperature of the cold period / wind speed, respectively) [14]: Zone 1 (-1.0 ℃ / 2.7 m/s); Zone 2 (-9.7 ℃ / 5.6 m/s); Zone 3 (-18.0 ℃ / 3.6 m/s); Zone 4 (-41.0 ℃ / 1.3 m/s). For experimental tests of thermal protective clothing, the standard rules established by the standard method for testing of general thermal insulation without additional heat sources are used [13]. The standard value of the thermal insulation parameter of such clothes is set taking into account the stay in the cold no more than 3 hours. The main criterion for evaluating the results of designing of the clothes is the level of "permissible thermal state" at which the working capacity and health of the employee are preserved, taking into account the requirements of continuous stay in the cold environment. Normalized thermal insulation values for this technique are given in Table 1. In order to verify the models that allow to obtain the design parameters for packages of materials and from thermal insulation in clothes, the methods for determining the thermal insulation of a set of ready- made clothes are used [13]. This method has two versions of implementation: A – with the participation of a human, and B – with a thermal dummy. In the first case (version A), the method consists of determining the thermal insulation of the clothing based on the results of measurement of the temperature of the human skin and the density of the dry thermal flow from the surface of the human body in the required test conditions [13]. Table 1. Normalized thermal insulation Protection class Temp- Speed* Standard value of clothing insulation, °C * m / W Wind / Climate air in zone (region) temperature winter For air permeability of the upper material, dm /(m ·s) * in winter months, months, °C m / s 10 20 30 40 4 / " Special " (IA) - 25 6,8 0,669 0,714 0,764 0,823 3 / IV (1Б) - 41 1,3 0,744 0,752 0,759 0,767 2 / III (II) - 18 3,6 0,518 0,534 0,551 0,569 1 / II-I (III-IV) - 9,7 5,6 0,451 0,474 0,500 0,528 *Probable air temperature and wind speed 2 Dynamics of Technical Systems (DTS 2020) IOP Publishing IOP Conf. Series: Materials Science and Engineering 1029 (2021) 012035 doi:10.1088/1757-899X/1029/1/012035 Version A2 implies a method for determining the thermal insulation of the clothing based on the measurement of the power of the energy consumed by the dummy to maintain the temperature of its surface in the desired test conditions [15]. The shape and size of the dummy conforms to an adult and must have a constant average surface temperature. The temperature distribution over the surface of the dummy's body should be the same as that of a human [14, 16]. A particularly difficult requirement is that the dummy must walk with a frequency of (45 ± 2) steps per minute, have a head, chest, back, abdomen, buttocks, arms with shoulders, forearms and hands with fingers, legs with thighs and lower legs and feet. Wherein, the total surface area of this thermal dummy is (1.8 ± 0.3) m, the height is (1,75 ± 0,1) m, anthropometric parameters of all parts of the body in accordance with the standard sizes of a human clothing. In addition to the enormous difficulties in ensuring the functioning of the listed requirements for the thermal dummies, it should be noted that such tests of experimental clothing depend on the respective special laboratory [16]. Such laboratories provide energy supply and an automated control system for the thermal dummies and the conditions for the formation of external climatic factors in the laboratory space, close to natural and industrial ones [17, 18, 19]. With all the technical difficulties in providing such a method, which includes a thermal dummy, the established problem should be highlighted that limits its use for heated clothing.
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