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