Introduction to heat

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Introduction to heat

• Is this heat?
• When I touch it, it burns me.
• I can feel the heat at a distance
• The hot gases rise

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But is this heat?

• Yes
• The difference between the two is Temperature
• Any substance whose temperature is above -276
  degrees celsuis or -460 degrees Fahrenheit
  contains heat

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Whether something is hot or cold is subject to
your preconceived experience

• When we see blue we tend to think cold
• When we see red we tend to think hot

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HVAC and R

• H is for heating
• V is for ventilation
• AC is for air conditioning or cooling
• R is for refrigeration

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Heating

• Increasing temperature from an intensity that is
  felt as too low to a comfortable intensity
• This can be accomplished by combustion of a
  chemical that releases heat
• Moving of heat from one place to another
• Convincing the person that they are actually warm

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Ventilation

• The movement of air to distribute heat

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Air Conditioning

• This is a little more complicated
• Air conditioned air is generally considered
  cooled air.
• Its humidity is also changed when it is cooled so
  it is considered conditioned

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Refrigeration

• Refrigeration is generally considered as
  temperatures below human comfort
• First used to extend perishable food life

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Heating Technology

• Technologically, heating is far easier than
  cooling
• The first forms were wood fired campfires around
  which everyone sat to be warmed

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Advantages

• Easy to start if you had something hot and it had
  not rained lately
• Fuel was easy to find
• Fire looks cool

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Disadvantages

• Was not self sustaining
• Smoke always followed you wherever you sat
• Rain had a dampening effect
• You were always cold on the side opposite the fire

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Ways to make campfire better

• Place fire in some sort of shelter to contain heat

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A better system with fire in center and way for
smoke to leave
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An even better way
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But how effective is a fireplace?
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Can you effectively heat a structure with a
fireplace?

• No
• Any ideas why?

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The fireplace draws air from the structure in
large amounts
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If you draw large amounts of air from a
structure, it must be replaced by outside air
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Where do you think the air comes from?
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It must be drawn in from cracks in windows and
doors
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And what temperature is this air?
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The same temperature as the outside air which is
why the other rooms in the structure are very
cold after the fire has been burning for a while
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So what can be done to solve this problem?
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The Franklin Stove
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The Franklin Stove (invented by Ben Franklin)
covered the majority of the open area that
removed so much air and only allowed enough air
to support combustion
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The cast iron body of the stove was warmed by the
fire which warmed the air in the room
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(No Transcript)
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We have developed a stove that is reasonably
efficient that can heat a structure. Is this the
best system for heating?
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What if there are more than one room in the house?

• The temperature in the room with the stove will
  be warm
• All other rooms will be progressively cooler the
  farther they are from the heat source

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This is a typical modern ductwork layout system
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Heat travels from the furnace Forced by a fan
through the Supply ducts to the Conditioned
space
Return air travels Through the return Ducts to
the furnace