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1、TRANSACTION ON CONTROL AND MECHANICAL SYSTEMS, VOL. 1, NO. 8, PP. 362-369, DEC., 2012. RECEIVED: 18, NOV., 2012; REVISED: 29, NOV., 2012; ACCEPTED: 18, DEC., 2012; PUBLISHED: 22, DEC., 2012. ISSN: 2345-234X Abstract: In this paper, the aim is obtaining convection coefficient of human body. At first
2、a 3D human body has been designed by unstructured grids. Feet and hands are stretched completely in considered sample. Two segments (standing and supine) are considered for body. Soles and the back of entire body are considered in contact with the ground respectively in these segments. Other parts o
3、f human body are exposed to surrounding air. The heat transfer and the body temperature are assumed steady and constant. The results are obtained by applying finite volume method for each grid and extracted by the weighted area method. Then the attained results are validated with the recent experime
4、ntal results. Good agreement is observed between the obtained results and the previous experimental results. Finally two formulas are derived for natural convection coefficient of human body. Keywords: Convection Heat Transfer Coefficient, Standing, Supine, Human Body, Numerical Simulation 1. INTROD
5、UCTION The forced convection process, is a process in which external operator causes the heat transfer operation to be performed 1. The natural convection (free convection) process is a process which doesnt need any external force to complete the thermal cycle. For instance, if a heat source is assu
6、med in a cold space, the air of the cold space which is close to the heat source is warmed and expanded. So because of decreasing density the air goes upward. Then in consequence of vicinity with cold air, its temperature decreases and it compressed again and therefore it goes back to its initial po
7、sition in the cycle. This process will take place only because of the temperature difference between the heat source and cold surrounding air. In this process there is no need of external operator such as fan. This paper is aimed at finding the natural convection heat transfer coefficient of human b
8、ody. This coefficient is essential for determining the exchanged heat transfer of human body with environment. In previous studies because of experimental limitations, thermal mannequins are used. Also for determining convection heat transfer coefficient an approximation area surface of the heat tra
9、nsfer for the mannequins was needed 2. In most of the previous studies, the convection heat transfer coefficient is determined by theoretical and experimental methods 3-35. In experimental studies determining the quantities such as temperature, velocity has some errors. But in analytical computation
10、s determining the quantities have less errors. In addition, obtaining a specific condition in laboratory is difficult and would be with some limitations. But in analytical simulation these conditions would set as an input. Also due to calculating up to some decimals, the accuracy of the calculating
11、is much more than the experimental measurements which have limitations. In some studies convection heat transfer coefficient is determined by using the ratio of a specific surface area to the entire body area and by use of the local coefficient. In most of these studies the accuracy of the results i
12、s decreased because of ignoring surfaces which dont have any convection heat transfer with surrounding air. The natural convection coefficient is calculated in experimental research related to temperature difference which is corrected by weighted area method. Of course in this method, the relation b
13、etween heat transfer coefficient with heat flux and temperature difference is assumed to be linear 2. In 1996 Dear 36 calculated this coefficient in a paper with the same content. But he determined the coefficient for each part of the body separately and in the limited number. In previous studies, h
14、eat transfer of the body has been determined experimentally by use of the simple thermal equipment 37, 37, 38, real objects 8-24, 39, or the naphthalene mass transfer 40-42. For simulation of human body heat transfer, the heat transfer has been considered in the mannequins 12, 25-46. In these studie
15、s different air velocities of the air has been considered for creating force convection heat transfer and various temperature difference between surrounding air and body for creating free heat transfer. In all the studies for human body, different shapes with various complexities are considered. Als
16、o, most of the shapes are situated in standing or sitting positions. So the body contact would be a little with the ground and calculations would be simpler. This shows the reason why the majority of researchers consider area ratio 1 for convection heat exchange. Although Kurazumi et al. 47, 48 showed that 10 to 20% of body surface doesnt participate in heat transfer by calculations. In these researches besides this heat condition, body situation 2, temperature of body
