BS: Lesson 3 - Basic Thermal Process Flashcards
What is temperature?
Temperature is a measure of stored heat energy. Temperature can never be transferred.
What is heat?
Heat is the amount of energy in a system or substance. Heat can be transferred to a substance with or without changing the substances temperature.
What is sensible heat?
Heat that changes the temperature of a substance, and does not represent the addition of any moisture to the substance.
What is latent heat?
The heat added to or removed from a substance causing it to change its state.
How is heat transferred?
radiation
convection
conduction
latent heat (evaporation)
The rate of radiation exchange is based on what?
- surface temperature of the objects
- the viewed angle
- emissivity
Emissivity is
the rate at which an object gives off heat; its a property of the material
True or False:
A black, dark and/or matte surfaces have higher emissivity and absorptivity than white, light and/or shiny surfaces.
True. Black, dark and matte surfaces heat up quickly, but cool rapidly.
True or False.
White, light and shiny surfaces heat up slower than black, dark and matte surfaces and stay hot longer.
True.
Selective surfaces
Surfaces that have a high absorptivity in one wavelength (usually solar) and low emissivity in another wavelength (usually infrared).
Which gases contribute to the earth’s greenhouse effect?
Carbon dioxide
Methane
Nitrous oxide
Chlorofluorocarbons
Mean radiant temperature
The average radiant temperature of your surroundings. It is independent of air temperature.
A globe thermometer is used to measure what?
Mean radiant temperature
The amount of heat one looses from conduction, convection, radiation and/or evaporation is based the interaction between what?
Our metabolism, clothing and environment.
True or False.
A liquid can evaporate only by removing large quantities of heat from the surface it is leaving.
True.
As air and surface temperatures approach our own body temperatures, what form of heat flow is most beneficial to help cool the body?
Evaporation with dry moving air.
As air and surface temperatures decrease, evaporation increases or decreases.
Evaporation decreases.
Conduction
The heat follow process that occurs when objects are in direct contact. It is not directional.
True or False.
Conduction is not directional
True.
How is resistivity (r) and conductivity (k) related?
Resistivity is the inverse of conductivity
True or False.
In buildings, conduction does not occur inside walls.
False.
How thick in R19 batt insulation?
6 1/2”
How thick is R15 batt insulation?
3 1/2”
What is one way to reduce the value of batt insulation?
Compressing its thickness.
Power.
The rate of energy usage over time.