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This comprehensive guide explores the basic principles of heat and cold, detailing how the body generates and regulates temperature. It explains how calories from food are converted to energy and the importance of maintaining a balance to prevent excess fat storage. Discover the three primary ways the body dissipates heat: convection, radiation, and evaporation, and learn about the various factors affecting human comfort, such as temperature, humidity, and air movement. Understand key concepts like heat index, dew point, and wind chill for a deeper appreciation of thermal comfort. ###
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How the Body Produces Heat • All food & drinks contain Calories • A Calorie is the heat value of food • Calories in the body are converted to energy & stored, this conversion process produces heat, which generates our body temp. • Excess Calories are stored as fat cells • Average calorie intake is approx. 2000
Calories & British Thermal Units (BTU) • One calorie is amount of heat required to raise 1 kilogram of water 1 degree C • 252 calories equals 1 BTU • 1 BTU will raise the temp of 1 lb of water 1 degree F Example: 1 lb H2O heated from 75 to 76 degrees, 1 BTU of heat energy absorbed into the H2O
Three Ways the Body Removes Heat • Convection – Heat flows from a hot surface to a surface (or air) with less heat • Radiation – Heat flows from a heat source to an object, does not heat the air • Evaporation – as moisture vaporizes, it removes heat from the surface, lowering its temp.
Factors That Effect Body Comfort • Temperature • Humidity • Air Movement
Temperature • Cool air increases rate of convection, warm air slows it down • Cool air lowers temp of surrounding surfaces, increasing heat radiation • Warm air raises temp of surrounding surfaces, decreasing radiation • Cool air increases rate of evaporation, warm air slow it down • Evaporation rate dependant on humidity level of surrounding air & air movement
Relative Humidity (RH) • 50% RH – air contains half of moisture it is capable of holding • Low RH (dry) readily absorbs moisture • High RH(Moist) slow down evaporation • Human comfort level – 72 – 80 degrees, 35 – 55% humidity
Other Factors • Heat Index – Measurement of discomfort when heat & humidity combine • Dew Point – Is the amount of moisture in the air at a given temperature • Wind Chill – Measurement of discomfort when cold & wind combined • Condensation – Water vapor returned to its liquid state
Air Movement • Evaporation increases – moisture carried away faster • Convection increases as layer of warm air around body is moved away • Radiation increases as heat on body surface is removed
Heat & Cold • Heat – Energy of molecules in motion, sensation of warmth or hotness • Cold – Feeling of no warmth, removal of an objects original heat • Laws of heat & Cold: (Heat is present in all matter) • Sensible heat – any heat that can be felt & measured ie. Heat to cook • Latent heat – heat required to cause a change in state, can not be measured • Water boils at 212 degrees at sea level (14.7psi)
Heat & Cold • Specific Heat – Amount of heat require to raise the temperature of solids, liquids, or gases • Heat Flow – Movement of heat from an object of higher temp to one of lower temp
