Human body, heat transfer from

C14-0131. Humans perspire as a way of keeping their bodies from overheating during strenuous exercise. The evaporation of perspiration transfers heat from the body to the surrounding atmosphere. Calculate the total zlS for evaporation of 1.0 g of water If the skin Is at 37.5 °C and air temperature Is 23.5 °C. 

Many familiar heal transfer application. involve natural convection as the primary mechanism of heat transfer. Some examples are cooling of electronic equipment such as power transistors, TVs, and DVDs heat transfer from electric baseboard heaters or steam radiators heat transfer from the refrigeration coils and power transmission lines and heat transfer from the bodies of animals and human beings. Natural convection in gases is usually accompanied by radiation of comparable magnitude except for low-emissivity surfaces. 

Special Topib Heat Transfer from the Human Body... 

Note that the total heat transfer from a human body is approximately 200 W. ... 

As the human body is homeothermic, heat production from the body should ideally equal heat loss. The metabolic rate can vary from about 80 W at rest up to over 1000 W during most strenuous activities, and a large part of this power is converted into heat (typically 80-85%). If the heat production is high, the largest part of this heat has to be evacuated to the environment. The heat exchange with the environment depends on four environmental factors the air temperature, the radiant temperature, the relative humidity in the air and the wind speed. Heat transfer can occur by four different means ... 

The ability of the human hody to maintain its temperature by tuning the amount of heat it transfers to and from its surroundings is truly remarkable. If you take courses in human anatomy and physiology, you will see many other applications of thermochemistry and thermodynamics to the ways in which the human body works. 

Radiative heat transfer between two bodies is a function of the fourth power of the absolute temperature of the surfaces involved. To simplify the computations for warm-to-hot environments, an approximation used for radiative heat transfer from the human body is... 

Identify the physical parameters involved in heat transfer from the human body. 

Clothing acts as a barrier between the human body and its environment, thus one of the functions required for clothing is to maintain heat and moisture from the human body at a certain level under various environmental conditions and to prevent sweat accumulation on human skin by allowing moisture release into the outside air. As presented in Fig. 19.3, heat and mass transfers through clothing are divided into transportation in an air gap between skin and clothing, which is called microclimate, transportation inside the clothing, and convection from the outer surface of clothes to the environment [17,18]. 

For comparison The metabolic heat generated in a human body varies from about 100 W for office work up to about lOOOW for heavy physical work. Note that heat loss by evaporation of water from the skin (perspiration) and in the lungs, which may considerably contribute to the overall heat transfer, is not considered here. 

ABSTRACT The analysis of a thermal comfort or to a thermal stress situation can be achieved using diverse techniques, models and numerical simulations. The main purpose of this paper is to use a human thermal software to analyze the human response to different thermal environmental conditions. The human thermal model is based on equations of heat and mass transfer and, based on the parameters of thermal environment that influence comfort, it can predict the temperatures and humidity at the human body and clothing. A simulation was done using the experimental data obtained from a field investigation at an industrial plant. Results indicate that the software can differentiate body parts concerning its thermal behavior according to their adaptability and in all cases, the temperature values tend to stabilization. A verification of the coefficients of heat transfer between the cloth and the environment is required being pointed as future work. 

By controlling the rate at which blood flows to the superficial areas of the body, it is possible for the body to vary the surface temperature and, thereby, exercise some control over the rate at which heat is transferred from the surface to the environment. Since most humans are equipped with a fairly thick subcutaneous layer of fat with a relatively... 

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