Mathematical Model for Localised and Surface Heat Flux of the Human Body Obtained from Measurements Performed with a Calorimetry Minisensor

Abstract

The accuracy of the direct and local measurements of the heat power dissipated by the surface of the human body, using a calorimetry minisensor, is directly related to the calibration rigor of the sensor and the correct interpretation of the experimental results. For this, it is necessary to know the characteristics of the body’s local heat dissipation. When the sensor is placed on the surface of the human body, the body reacts until a steady state is reached. We propose a mathematical model that represents the rate of heat flow at a given location on the surface of a human body by the sum of a series of exponentials: W(t) = A0 + ∑Aiexp(−t/τi). In this way, transient and steady states of heat dissipation can be interpreted. This hypothesis has been tested by simulating the operation of the sensor. At the steady state, the power detected in the measurement area (4 cm2) varies depending on the sensor’s thermostat temperature, as well as the physical state of the subject. For instance, for a thermostat temperature of 24 °C, this power can vary between 100–250 mW in a healthy adult. In the transient state, two exponentials are sufficient to represent this dissipation, with 3 and 70 s being the mean values of its time constants.

A Method to Determine Human Skin Heat Capacity Using a Non-Invasive Calorimetric Sensor

“…The experimental system has already been described in previous works [19,20], but in order to explain the calorimetric model proposed in this work, it is necessary to briefly describe the elements that constitute the sensor. The core of the sensor is a measurement thermopile (part 2 in Figure 1) located between an aluminium plate (part 1 in Figure 1) and a thermostat (part 3 in Figure 1).…”

“…The working principle consists of applying the sensor to the skin (5-15 min) and determine the heat flow that is transmitted by conduction from the skin to the thermostat inside the device. Two prototypes with different configurations have been built, the first one with a measuring surface of 36 cm 2 [17,18] and the second one with a measuring surface of 4 cm 2 [19,20]. The second one, with smaller size, has a faster response and is easier to handle.…”

A High-Resolution Measurement System Designed for Semiconductor Microcalorimetry Sensors

“…However, regarding measurement and control systems, the design best practices are not discussed, which is particularly important in the case of the sensitive microcalorimeters for test samples that are very small in volume. Finally, more recent applications of microcalorimetric devices can be found in [34][35][36].…”

A Miniaturized 3D Heat Flux Sensor to Characterize Heat Transfer in Regolith of Planets and Small Bodies

“…Different sensing principles can be used to infer heat flux in surfaces, such as the detection of infrared radiation [ 16 ], contact thermopiles [ 17 , 18 ], indirect procedures such as calorimetry [ 19 , 20 ] or other approaches in which temperature gradients are measured and an estimation of the thermal conductivity is used [ 21 ].…”