Development and application of numerical model of thermal sensors for thermal protective clothing evaluation based on CFD simulation

PurposeThe purpose of this paper is to study the heat transfer effect of copper sensor and skin simulant on skin.Design/methodology/approachFor the sensor, the physical and mathematical models of the thermal sensors were used to obtain the definite conditions in the heat transfer process of the sensor, and the heat transfer models of the two sensors were developed and solved respectively by using ANSYS WORKBENCH 19.0 software. The simulation results were compared with the experimental test results. For the skin, the numerical model of the skin model was developed and calculated. Finally, the heat transfer simulation performance of the two sensors was analyzed.FindingsIt is concluded that the copper sensor is more stable than the skin simulant, but the material and structure of the skin simulant is more suitable for skin simulation. The skin simulant better simulates the skin heat transfer. For all the factors in the model, the thermal properties of the material and the heat flux level are the key factors. The convective heat transfer coefficient, radiation heat transfer rate and the initial temperature have little influence on the results, which can be ignored.Research limitations/implicationsThe results show that there are still some differences between the experimental and numerical simulation values of the skin simulant. In the future, the thermal parameters of skin simulant and the influence of the thermocouple adhesion should be further examined during the calibration process.Practical implicationsThe results suggest that the skin simulant needs to be further calibrated, especially for the thermal properties. The copper sensor on the flame manikin can be replaced by the skin simulant with higher accuracy, which will be helpful to improve the accuracy of performance evaluation of thermal protective clothing.Social implicationsThe application of computational fluid dynamics (CFD) technology can help to analyze the heat transfer simulation mechanism of thermal sensor, explore the influence of thermal performance of thermal sensor on skin simulation, provide basis for the development of thermal sensor and improve the application system of thermal sensor. Based on the current research status, this paper studies the internal heat transfer of the sensor through the numerical modeling of the copper sensor and skin simulant, so as to analyze the effect of the sensor simulating skin and the reasons for the difference.Originality/valueIn this paper, the sensor itself is numerically modeled and the heat transfer inside the sensor is studied.

Definition of the Main Features of Material Assemblies for Thermal Protective Clothing During External High-temperature Effect Modelling

A computational-experimental method of material selection for thermal protective clothing design is proposed in this article. The intended operating temperature of the garment lies within the range of 40−170 °С. The prereq¬uisite for the research was the lack of information regarding changes in the physical-mechanical and ergonomic characteristics of material assemblies during their use under high-temperature conditions. During the initial stage of research, there was a problem associated with the selection of the most important and the exclusion of the least significant indicators, in order to further reduce the number of experimental tests in laboratory and industrial conditions. The authors used the method of expert evaluations to solve the problems related to the selection of the most significant indicators for material assemblies. Material assemblies were formed by vary¬ing the combinations of heat-resistant, heat-insulation and lining layers of materials. Initial information for the proposed method was obtained from the experimental tests of sixteen material assemblies. According to the results of the ranking, the main parameters of material assemblies were identified as follows: the temperature range for which the use of clothing is intended, thickness, mass per unit density, rupture resistance, relative tear¬ing elongation, change in linear dimensions during mechanical loads, air permeability and change in assembly thickness during cyclic loads. It was established that the assembly that includes heat-resistant material of the Nomex comfort N.307 220 top, Nomex Serie 100 heat-insulation lining and Nomex TER 135 lining provides the necessary level of protection, reliability and ergonomics, and meets cost requirements.

Influential Parameters of Starching Process on Mechanical Properties of Yarns Intended for Multifunctional Woven Fabrics for Thermal Protective Clothing

The investigation of influential parameters of the starching process on mechanical properties of yarns intended for multifunctional woven fabrics for thermal protective clothing was performed on four different yarn samples starched on an innovative starching machine, adapted to industrial starching conditions. The starching was conducted with two different processes with different starch mass concentrations: the standard starching process and a newer starching process (with yarn prewetting). Based on the results obtained, it can be concluded that starching positively affects all the properties of tested samples and that the increase of starch mass concentration is not accompanied by the improvement of those yarn properties. Synthetic polymer fibers that achieve satisfactory yarn strength need to be starched with lower starch mass concentrations in order to retain the breaking properties and to be protected from abrasion and static electricity, which occurs during the weaving process. The yarn prewetting starching process shows significantly better results than the standard starching process, especially for aramid yarns, where abrasion resistance increased from 42 to 135%. Therefore, we can conclude that the goal of starching such yarns is aimed at increasing the wear resistance. Linear regressions and correlations between the values of breaking properties and abrasion resistance obtained by the testing and their values that were estimated by the analysis show a high correlation coefficient.

Characterization of Heat Protective Aerogel-Enhanced Textile Packages

The aim of this study was to investigate the effects of aerogel application on the thermal properties of textile packages intended for use in protective clothing. The packages were prepared in the form of removable inserts filled with aerogel, differing in terms of fabric and design. The developed packages were tested for resistance to the three major types of heat: radiant, convective, and contact. The package variant with superior thermal performance was also evaluated for water vapor resistance. The package after incorporation of aerogel was found to approximately double radiant and convective heat resistance, with an approx. eightfold improvement for contact heat at the highest test temperature 250℃. Threshold time increased from (17.7±0.7) s to (139.9±4.9) s for the optimum aerogel-enhanced package variant with the greatest number of pouches, which met the criteria of the highest performance level. The thermal conductivity and thermal resistance of three fabrics selected for testing were tested in order to determine their basic thermal insulation properties. In general, packages containing a larger number of narrower pouches exhibited higher thermal protective performance. The results show that the developed textile packages with aerogel can be successfully used in thermal protective clothing.