heating systems
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HEATING HEATING SYSTEMSSYSTEMS
QuestionsQuestions• Why do we need heating systems?• What was the first heating system?• Which types of energy do you need to operate
today’s heating systems?
How is the human body like a How is the human body like a heating system?heating system?
• Purpose of a heating system• Comparison of components in a radiant heat
system vs. the human body• Seasonal heat flow associated with your house
and your body• Purpose of insulation
Desert Cottontail—how does the Desert Cottontail—how does the rabbit shed excess thermal rabbit shed excess thermal
energy?energy?
http://k43.pbase.com/o6/50/493350/1/81965672.V6e9SMLr.DesertCottontail7907web.jpg
Fur keeps the rabbit warm at night
Ears serve as heat radiators (see blood vessels)
Function of a heating Function of a heating systemsystem
• 1. Burn a fuel• 2. Heat a fluid (air or water)• 3. Circulate a heated fluid• 4. Transfer thermal energy into a space
o By convection, conduction and radiation
Heating SystemHeating System• Any device or process that transfers energy to a
substance to raise the temperature of the substance.
The problem: HEAT The problem: HEAT FLOW FROM HOUSEFLOW FROM HOUSE
During cold days
Three thermal energy Three thermal energy transfer methods in transfer methods in
action.action.
Different types of Different types of heating systemsheating systems
• Radiant heating system• Forced-air heating system• Wood stove• Fireplace• Heat Pump• Circulation of geothermal fluids
Radiant Heat SystemRadiant Heat System
Where does the thermal energy go?
Forced-air Heating Forced-air Heating SystemSystem
Solar Heating SystemSolar Heating System
Wood StovesWood Stoves
Geothermal Heating Geothermal Heating SystemsSystems
Do you see where thermal energy is Do you see where thermal energy is
added to a fluid and can you find the added to a fluid and can you find the
exhaust?exhaust?
http://www.hometips.com/hyhw/comfort/38comf.html
http://www.woodfloorsonline.com/techtalk/woodwater7.html
http://www.greenenergy.org.uk/sta/solarenergy/howwork.htm
http://www.diydata.com/projects/centralheating/balancing/balancing.htm
http://www.northridgevillehistoricalsociety.org/images/schoolinnorthw.jpg
http://www.totalcomfortnc.com/geo.htm
http://www.igshpa.okstate.edu/geothermal/geothermal.htm
Heating Heating SystemsSystems
2nd law of thermodynamics—heat always flows from a hotter to a colder
substance
Explain why the heat flow for a home is different in the winter vs. the summer.
Summer– outdoor air temperature is greater than indoor air temperature (flow is from outside in)
Winter—indoor temperature is greater than outdoor temperature (flow is from inside out)
Commom Fuel Commom Fuel Sources for HeatingSources for Heating
• Wood• Coal• Oil• Natural Gas (methane)
MethaneCH4
Mid-1700’s to 1800’sMid-1700’s to 1800’s• Fireplace with brick• Franklin iron wood stove
• Fuel Source: wood
1885-19001885-1900• Coal Boiler• Natural convection (no electricity for pumps)
• Fuel Source: coal
1900-1930’s1900-1930’s• Coal Boiler • Circulated water or steam to radiators
• Fuel Source: coal
1930’s -1930’s -• Radiant Heat and Forced Air Heating Systems • Circulated “heated” water or steam to radiators
and “heated” air through ducts to registers
• Fuel Source: natural gas and oil
1950’s --1950’s --• Trend towards forced air heating systems to
accommodate central air conditioning
• Fuel Source: forced air heating(natural gas)• Air conditioning (electricity from coal)
Burn a fuel
Heat a fluid
Circulate a heated fluid
radiator
Water-filled pipes
Radiant energy
90 F 150 F
Radiant Heating System
Burn a fuel
Heat a fluid
Circulate a heated fluid
convection
Forced-air Heating System (can be adapted to central whole-house air conditioning)
Convection, Convection, Conduction or Conduction or
Radiation?Radiation?1. Stick in campfire2. Hot air balloon rising3. Hot concrete surface
at pool 4. Lizard sunning itself
on a rock5. Pan of soup warming
on the stove6. Foot on cold tile floor
• Conduction• Convection• Radiation
• Radiation
• Convection
• Conduction
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