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# Heat Transfer & Thermal Control

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by

## J West

on 7 April 2017

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#### Transcript of Heat Transfer & Thermal Control

Why is Heat Transfer & Thermal Control Important to YOU?
Thermal Control
Your mission is to control conduction and convection.
its not rocket science
Heat Transfer
& Control

I guess it is rocket science . .
1. Define
conduction,
convection,
2. List examples of convection
3. Identify methods to control conduction & convection
Session Objectives
J. West
HpH2TC

773.732.3131
hph2tc@gmail.com
Energy
States that energy is neither created nor destroyed. Energy only moves from place to place and changes form.
1st Law of Thermal Dynamics
States that heat moves from high temperature regions to low temperature regions - never the reverse.
2nd Law of Thermodynamics
Thermal Control Layer
The components that are designed and installed in an assembly to control the transfer of thermal energy (heat).
Conduction
the transfer of heat between substances that are in direct contact with each other
Convection
Occurs when fluids (gasses and liquids) with a lot of heat energy move and take the place of fluids with less heat energy.
Heat transfer that does not rely on any contact between the heat source and the heated object. Unlike conduction and convection.
A measurable quantity of HEAT, work or light.
Heat Transfer
It's Physics . . .
Can you name some examples of convection?
Control Conduction with Insulation
more

cold

Flow is from _____ to _____.
The higher the Temperature Difference, the ______ heat and air want to escape or enter the building.

T=20

20º

90º

70º

70º

Summer

Winter

T = Temperature Difference

Controlling Convection with Air Sealing
Temperature Difference Drives Convection
Flow is from ________________ to ______________ pressure
For every CFM that leaves , one CFM enters
Flow takes the path of _______ resistance.

least
exits

negative (low)

positive (high)

Negative

Positive

Pressure Drives Convection

Air leakage requires:
A hole.
Pressure difference across that hole.
The bigger the hole or higher the pressure difference, the more airflow.
To reduce airflow, we can reduce the size of the hole or lower the pressure difference.

Convection Depends on Hole & Pressure

Indirect Leakage
Leakage enters at one location moves through building cavities and exits at a different location.

Indirect Leakage
Leakage enters at one location moves through building cavities and exits at a different location.

Convection is Direct & Indirect
Direct Leakage
occurs at direct openings to outdoors. Leakage enters and exits at same location.

Infiltration =
Air leaking in.

Exfiltration =
Air leaking out.

Convection Brings Air in & Out

Ventilation = Controlled
air leakage.

positive pressure

negative pressure

Neutral pressure plane

Convection is Stack Effect

Warmer air rises and escapes out of the top of the house. . .
Which creates a suction that pulls in outside air at the bottom of the house.

Indirect Leakage
Enters through one location, moves through building and enters conditioned space at another location
Full transcript