Human skin thermal properties determination using a calorimetric sensor
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Human skin thermal properties determination using a calorimetric sensor P. J. Rodríguez de Rivera1,2 · Mi. Rodríguez de Rivera1 · F. Socorro1 · M. Rodríguez de Rivera1 · G. M. Callicó2 Received: 29 August 2019 / Accepted: 23 March 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The purpose of the calorimetric sensor developed is to measure the heat flux transmitted by conduction between the human body surface and a thermostat located inside the sensor. The measurement surface has an area of 2 × 2 cm2. We have verified that the measured heat flux decreases linearly with the increase in the thermostat temperature. This allows us to define an equivalent thermal resistance between the internal temperature of the human body and the temperature of the thermostat. This equivalent thermal resistance can be determined by measuring the heat flux for different constant temperatures of the thermostat. An alternative is to perform a single measurement with linear programming of the thermostat temperature. With this type of measurement and from the calorimetric signal, it is also possible to determine an equivalent heat capacity of the skin in the measurement zone. In this article, we present the modelling and simulation of the sensor operation when the thermostat temperature varies linearly. We also present experimental measurements performed on the human body and with reference Joule dissipations. Keywords Direct calorimetry · Heat conduction calorimeters · Human skin · Medical calorimetry · Thermal resistance · Thermal capacity
Introduction A specially designed calorimetric sensor has been developed to directly measure the heat flux dissipated by the surface of the human body when the sensor is placed on the skin. This heat flux is transmitted by conduction between the human skin and a thermostat located inside the sensor. * M. Rodríguez de Rivera [email protected] P. J. Rodríguez de Rivera [email protected] Mi. Rodríguez de Rivera [email protected] F. Socorro [email protected] G. M. Callicó [email protected] 1
Departamento de Física, Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain
Instituto Universitario de Microelectrónica Aplicada (IUMA), Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain
2
Two prototypes have been developed, the first one with a detection surface of 6 × 6 cm2 [1–4] and the second one with a detection surface of 2 × 2 cm2 [5–8]. Both prototypes share the same principle of operation, although the second one, smaller in size, has smaller time constants and can be applied more easily to the skin. These sensors can be included in the group of non-differential heat conduction calorimeters [9]. In the normal operation of this sensor, the measurements are made with its thermostat at a constant temperature. However, making measurements for different constant temperatures of the thermostat (between 24 and 36 °C, below 37 °C) we verify that the measured power decreases when the thermostat temperat
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