PDX_03_Environmental Issues Vocabulary Flashcards
Overall rate of heat flow through any combination of materials, used for determining the size of heating system
Coefficient of heat transmission
Or U-value
A measure of energy, typically noted as the amount of energy needed to raise 1 pound of water by 1°F
British Thermal Unit
BTU/hour that passes through 1 ft.² of material of a given thickness when the change in temperature is 1°F
Conductance (C)
Ability of a material to transmit or conduct heat or electricity based on the physical properties of the material, expressed in BTU
Thermal conductivity (k)
BTU/hour that passes through a 1 ft.² of material 1 inch thick when the change in temperature is 1°F
Conductivity (k/in)
The difference between conductivity and conductance
Conductivity specifies the thickness of given material to be 1”
The measure of an objects ability to absorb and then radiate heat
Emissivity
Energy radiated by the surface of a body person per unit area
Emittance
Number of hours needed for one BTU to pass-through 1 ft.² of material or assembly of a given thickness when the change in temperature is 1°F
Resistance (R)
Heat required to convert a solid to a liquid or vapor, or a liquid into a vapor, without change of temperature, given in BTU
Latent heat
Amount of energy released or absorbed by chemical substance during a change of temperature, changes the temperature but not the state, given in BTU
Sensible heat
The amount of energy required to raise the temperature of a material by 1°F, the capacity to store heat, given in BTU
Specific heat
Heat given off by a vapor condensing to liquid, or the heat absorbed by a liquid evaporating to a gas without a change in temperature
Heat of vaporization
Ratio of moisture content of the air to the max possible moisture content of air at the same temperature without condensing
Relative humidity
Total heat loss in a substance (latent and sensible heat), given in BTU
Enthalpy (H)
Transfer of heat between services that are not in direct contact
Radiation
Transfer of heat between two objects that are in direct contact
Conduction
Transfer of heat that requires a fluid medium like air to transfer
Convection
Liquid is absorbed into the air as latent heat
Evaporation
Amount of insulation which will maintain normal skin temperature of the human body, equivalent of a typical American man’s suit in 1941
Clo
The average yearly difference between the indoor temperature and outdoor temperature. Typically a reference temperature of 65°F is used.
Degree Day (DD)
Used to design and size heating system that determines the day cooler than 98% of all days in a year experienced in a climate
Design Day
Typically referred to as air temperature, it’s what people are referring to when they talk about temperature. It’s an indicator of heat content and measured by a common thermometer, given in degrees Fahrenheit.
Dry bulb temperature
The lowest temperature that can be reached under current ambient conditions by the evaporation of water only, given in degrees Fahrenheit.
Wet bulb temperature
