Thermal Efficiency of a Human Being

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Thermal Efficiency of a Human Being
• A human body is essentially a biological machine. We will analyze its efficiency as compared to machines that we have invented.
• Discussions are included on the specific methods that our bodies use to lose waste heat from the many biological processes necessary to keep us alive, which stabilizes our body temperature.
• Discussions are consider exactly what happens to the food and food energy we ingest each day, which includes some amazing surprises!
• Many other related concepts and subjects are also addressed.

How many BTU’s does the human body generate?

“The human body maintains a basic minimum rate of heat production at about 250 Btu/hr during sleep, the heat equivalent of about 75 watts, and about 400 Btu/hr (120 watts) when awake but sedentary activity increases, the rate of oxidation of food, with its attendant release of energy, must increase. The level of heat production for light work will be about 650 Btu/hr (190 watts), the extreme value for heavy work, about 2400 Btu/hr (700 watts).”

400 BTU’s awake and 250 BTU’s sleeping

How many watts of energy in BTU’s does the human body give off at rest for one hour?

1 met = 1kcal/kg/hr
1kcal = 3.97 Btu
At rest, the human body expends about 0.8 met.
So, a 70 kg person at rest generates 0.8 * (3.97 Btu * 70 kg) every hour.
That would be about 222 btu/hr, which is not a measure of watts, so….
Since 1 btu/hr = 0.293 watts, that same person generates 65.14 watts at rest.

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