A.G. Kozlov1, K.S. Baklanova2, M.G. Potudanskaia3

1 Omsk State Technical University (Omsk, Russia)
2,3 Dostoevsky Omsk State University (Omsk, Russia)
1 agk252@mail.ru, 2 ksyusha.m@mail.ru, 3 potudanskaiamg@omsu.ru

The process of thermoregulation in the human body occurs with active heat exchange with the environment and requires a detailed study of the thermophysical parameters of heat exchange. These parameters include the temperature of the human body surface and the heat flux density on the human body surface, as well as the heat transfer coefficient from the human body surface to the environment. For direct measurement of the heat flux density on the human body surface, "additional wall" type sensors are used. When using the considered sensors to measure the heat flux density on the human body surface, it is necessary to take into account a number of factors that affect the measurement error, primarily the systematic error, and limit its spatial resolution.

The aim of the work is an experimental study of the heat flux density on local areas of the human body using heat flux density sensors of an "additional wall" type, an assessment, based on the research data, of the heat transfer coefficient of the human body surface and the development of a method for determining the systematic error in measuring the thermophysical characteristics of the heat exchange process on the human body surface.

The article analyzes the factors affecting the measurement error of heat flux density sensors. An analytical method for determining the systematic error of a heat flux density sensor due to its finite thickness is proposed. The method is based on dividing the "heat flux density sensor – human body" system into three zones and determining the one-dimensional temperature distribution in each zone for areas with and without the sensor. Heat flux densities are found from a joint solution of equations for the boundary conditions between the zones, as well as between the zones and the environment. The systematic error of heat flux density measurement is determined from the difference in heat flux densities between areas without the sensor and with him. The dependence of the relative error on the sensor thickness is obtained and an estimate of this error is made for a specific sensor used.

A methodology for a comprehensive study of heat exchange processes on the surface of human forearms is presented. Surface temperature measurements were carried out using a thermal imaging method (PERGAMED thermal imager). The sensor of DTP 0924-E-D-20-0 type was used to measure the heat flux density. During the study, temperature and average heat flux density were measured in 12 zones of the left and right human forearms. Based on the results of temperature measurements using the thermal imaging method, the average temperature of the sensor location area was determined. Based on the obtained average temperature values and the average heat flux density, the heat transfer coefficient values in the forearm zones were calculated. Using the thermophysical parameters obtained for each zone, an assessment of changing the average temperature, the heat flux density, and the heat transfer coefficient along each forearm was made and these dependencies were presented in an analytical form by approximating them with third-degree polynomials. An analysis of these dependencies for all patients showed that the change of the average surface temperature from the proximal to the distal forearm does not have common patterns. A difference of the surface temperatures between the left and right forearms was noted for each patient. Some patients had a higher temperature in the left forearm, while others, on the contrary, had a higher temperature in the right forearm. The values of heat flux density between the forearm zones have a large spread and the difference in their values between the left and right forearm correlates with the difference of their surface temperatures. The dependences of the average heat flux density along the forearm surface obtained by approximating the experimental values had maxima that were in the middle section of the forearm. The dependences of the heat transfer coefficient along each forearm have a maximum that correlates with the maximum of the dependence of the average heat flux density on the surface of this forearm. For each patient, the ranges of changing the values of the heat transfer coefficients along the left and right forearms are almost the same.

The thermophysical parameters of the zones were used to determine the generalized thermophysical parameters for each forearm of the examined patients and statistically evaluate their values. Their analysis shows that the average value of the average heat flux densities by forearm zones can be used to characterize the heat exchange process on the surface of the human forearm. In this case, the relative standard deviation does not exceed 17.5%. The relative systematic error of the heat flux density sensor, equal to
–6.17%, is significantly less than the specified relative standard deviation.

The obtained results show the potential of using the heat flux density sensor of the “additional wall” type in conducting complex studies of heat exchange processes on the surface of the human body in order to increase the reliability of determining various pathologies due to impaired blood microcirculation and to ensure optimal conditions for its vital activity.

Kozlov A.G., Baklanova K.S., Potudanskaia M.G. Application of heat flux density sensors to study heat exchange processes on a human body surface. Biomedicine Radioengineering. 2025. V. 28. № 6. P. 51–64. DOI: https:// doi.org/10.18127/j15604136-202506-06 (In Russian)

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