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

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

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

HVAC and R

• H is for heating

• V is for ventilation

• AC is for air conditioning or cooling

• R is for refrigeration

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

Ventilation

• The movement of air to distribute heat

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

Refrigeration

• Refrigeration is generally considered as temperatures below human comfort

• First used to extend perishable food life

Heating Technology

• Technologically, heating is far easier than cooling

• The first forms were wood fired campfires around which everyone sat to be warmed

Advantages

• Easy to start if you had something hot and it had not rained lately

• Fuel was easy to find

• Fire looks cool

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

Ways to make campfire better

• Place fire in some sort of shelter to contain heat

A better system with fire in center and way for smoke to leave

An even better way

But how effective is a fireplace?

Can you effectively heat a structure with a fireplace?

• No

• Any ideas why?

The fireplace draws air from the structure in large amounts

If you draw large amounts of air from a structure, it must be replaced by outside

air

Where do you think the air comes from?

It must be drawn in from cracks in windows

and doors

And what temperature is this air?

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

So what can be done to solve this problem?

The Franklin Stove

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

The cast iron body of the stove was warmed by the fire which

warmed the air in the room

We have developed a stove that is reasonably efficient that can

heat a structure. Is this the best system for heating?

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

This is a typical modern ductwork layout system

Heat travels from the furnaceForced by a fan through the Supply ducts to the Conditioned space

Return air travels Through the returnDucts to the furnace