Fundamentals Of Heat Transfer Flashcards
Conduction and convection are tied to hat kind of motion?
Molecular
What are the three fundamental modes of heat transfer?
Conduction, convection, and radiation
Radiation heat transfer is tied to what?
Electromagnetic waves
True/false: radiation heat transfer requires a medium such as air or water through which to travel.
False.
The movement of heat through a substance or between two substances in contact with each other is called what?
Conduction
Which is the most efficient of the 3 types of heat transfers?
Conduction
The rate of conduction heat transfer through a material is (blank) to the temperature difference between each surface and (blank) to the thickness of the material.
Proportional. Inversely proportional.
Materials that resist heat flow are called what?
Thermal insulators
Convection is heat transfer by the (blank)of heated or cooled (blank)
Motion. Mass
True/false: radiative energy travels near the speed of light when unimpeded.
True
Radiant heat transfer (does, does not) require a molecular medium for heat transfer to occur.
Does not
Radiative energy is classified by length of what?
Wavelength
What are the 3 most important waves associated with thermal radiation?
Ultraviolet, visible light, and infrared
In radiant heat transfer, higher temperature bodies emit (smaller, larger), (more powerful, less powerful) wavelengths
Smaller. More powerful
With translucent materials, the capability of the surface of the receiving body to transmit, absorb, and reflect radiative energy varies with the size of (blank) striking the surface.
Wavelength
The radiative energy emitted by the surface of a body is called what?
Emissive power or emmittence.
A (blank) is a hypothetical globe-shaped body that absorbs all of the radiative energy striking it, and emits all of this radiative energy.
Black body
Heat passing through materials in a building envelope is called what?
Transmission heat loss
Thermal conductivity describes a (blank) material’s ability to (blank)
Homogeneous. Transfer heat
A heterogeneous or composite materials ability to transfer heat is called what?
Thermal conductance.
A measure of a material’s ability to resist heat transfer is called what?
Thermal resistance.
The denser a material, the (more/less) resistance it has to the flow of heat and the (higher/lower) it’s resistance value (R). The lighter, less dense the material, the (higher/lower) it’s R value and insulating value.
Lower. Lower. Higher.
What is total thermal resistance?
The insulating ability of a construction assembly of materials, including air films.
The Total Thermal Resistance of construction assembly of materials is determined by adding the (blank) of each component.
Thermal resistances
the ability of a construction assembly to transfer heat, from exterior to exterior, including air films is called what?
The Overall Coefficient of Heat Transmission
A (blank) in a building envelope assembly or component is a penetration of the insulation layer by a highly conductive or non insulating material.
Thermal bridge.
Name three methods to express thermal resistance (R) properties of a construction assembly.
Center of cavity R value
Clear-wall R value
Whole wall R value
The center of cavity R value is an R value estimation at a point in the assemblies cross section containing the most (blank)
Insulation
The clear wall R value is an R value estimation for the exterior wall area containing only (blank) and necessary (blank) for a clear section with no fenestration, corners, or connections between other envelope elements.
Insulation
framing materials
The whole wall R value is an R value estimation for the (blank) including including the thermal performance of the clear wall area and envelope interference detailsipoh.
Whole opaque wall
A temperature gradient exists when there is a change in (blank) over some (blank) across a material.
Temperature
Distance
What is the difference between natural convection and forced convection?
Natural convection occurs naturally and forced convection occurs by mechanical means
What is heating load?
It is the heat that the HVAC equipment must generate me introduce into the building to Into comfortable conditions.
