The Human Body
05-20-2008, 08:14 PM
#1
3.0 BAR
Thread Starter
Join Date: Sep 2003
Posts: 5,448
The Human Body
Our living bodies generate heat because we are homiothermic (warmblooded) creatures. The rate at which heat is produced depends primarily on our metabolic rate.
Metabolic rate = our ability to generate heat is mostly a function of our level of muscular activity. Some of the energy generated by muscular activity will be directly translated into work (force x distance) and the excess energy will be dissipated as heat.
Met units - Each of us in this classroom is producing about 1 met (1 unit of metabolic rate) of waste heat.
Because, as we shall see, heat exchange with our environment is primarily via the skin, the met unit is defined in terms of both heat energy and surface area.
1 met = 58.2 w/m2 (SI units)
= 18.4 Btu/h/ft2
(i.e. 58.2 x 3.412/10.76 = 198.5784/10.76 = 18.4
1 watt = 3.423 Btu/h
1 m2 = 10.76 ft2
1 Btu = amount of heat required to increase temperature of 1 pound (1 pint) of water by 1 DEGREE F = heat produced by 1 standard wooden match. Every square foot of body gives off heat of about 19 matches/hour.
To increase temperature of 1 pound of water from 32°F to 212°F requires 180 Btu (i.e. 212-32=180)
SURFACE AREA OF BODY
Du Bois area: The surface area of skin of an "average" adult is 1.8 m2 (1.8 x 10.76 = 19.368 ft2) The total heat production of an "average" person at rest per hour is 58.2 x 1.8 = 104.76 = 105 watts (18.4 x 19.368 = 356.37 = 356 Btu's per hour).
The Du Bois area normally varies between 1.3 m2 (14 ft2) and 2.2 m2 (23.7 ft2) and in any setting the heat produced by sedentary adults will vary between about 75.66 watts (271 Btu's) for 1.3 m2 and 128 watts (459 Btu's) for 2.2 m2.
Metabolic rate = our ability to generate heat is mostly a function of our level of muscular activity. Some of the energy generated by muscular activity will be directly translated into work (force x distance) and the excess energy will be dissipated as heat.
Met units - Each of us in this classroom is producing about 1 met (1 unit of metabolic rate) of waste heat.
Because, as we shall see, heat exchange with our environment is primarily via the skin, the met unit is defined in terms of both heat energy and surface area.
1 met = 58.2 w/m2 (SI units)
= 18.4 Btu/h/ft2
(i.e. 58.2 x 3.412/10.76 = 198.5784/10.76 = 18.4
1 watt = 3.423 Btu/h
1 m2 = 10.76 ft2
1 Btu = amount of heat required to increase temperature of 1 pound (1 pint) of water by 1 DEGREE F = heat produced by 1 standard wooden match. Every square foot of body gives off heat of about 19 matches/hour.
To increase temperature of 1 pound of water from 32°F to 212°F requires 180 Btu (i.e. 212-32=180)
SURFACE AREA OF BODY
Du Bois area: The surface area of skin of an "average" adult is 1.8 m2 (1.8 x 10.76 = 19.368 ft2) The total heat production of an "average" person at rest per hour is 58.2 x 1.8 = 104.76 = 105 watts (18.4 x 19.368 = 356.37 = 356 Btu's per hour).
The Du Bois area normally varies between 1.3 m2 (14 ft2) and 2.2 m2 (23.7 ft2) and in any setting the heat produced by sedentary adults will vary between about 75.66 watts (271 Btu's) for 1.3 m2 and 128 watts (459 Btu's) for 2.2 m2.
05-20-2008, 08:29 PM
#2
3.0 BAR
Join Date: Mar 2003
Posts: 21,479
Re: The Human Body
^^^^This ---- is exactly why you're still a virgin. 
__________________
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
__________________
Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
05-20-2008, 09:14 PM
#7
1.0 BAR
Join Date: Feb 2004
Posts: 243
Re: The Human Body
Don't forget about metabolic uncoupling, allows babies with brown fat to generate more metabolic heat by uncoupling the electron transport chain. There are also a few drugs that can generate the same effects in adults(used to be used for weight loss).
