[ILM] 102A Flashcards
absolute presssure
A system of pressure measurement with a starting point in a perfect vacuum
0 psig = 14.7 psia
absolute temperature
0R == -460F
adiabatic compression
The compression of refrigerant gas without removing or adding heat content
ambient temperature
The average temp of the media that surrounds a point
BTU (British Thermal Unit)
the amount of heat required to raise the temp of 1lb of water by 1F
enthalpy
The heat in 1 lb or kg of a substance from a zero-base point and at -40F
entropy
A measurement of energy transfer where the energy is moved but not used to do work
head, static pressure
Fluid pressure based on the height of a column of fluid
IDLH
Immediately Dangerous to Life or Health
laminar flow
The smooth undisturbed flow of a fluid within a duct or pipe
turbulent flow
The chaotic flow of a fluid within a duct or pipe
latent heat
Heat gained or lost with no temperature change
sublimation
a change of state from a solid directly to a vapour without having a liquid state (승화)
superheating
adding sensible heat to a vapour at its evaporation pressure
subcooling
removing heat from a liquid at its condensation pressure
desuperheating
sensible heat is removed from a vapour or gas while it remains at its saturation or boiling pressure
Threshold limit value (TLV)
The refrigerant concentration in air for a normal 8 hr workday and a 40 hr workweek to which nearly all workers may be repeatedly exposed, day-after-day, without adverse effect
1 ton of refrigeration ==
288,000 Btu/24hrs
12,000 Btu/hr
200 Btu/min
Sensible heat
heat we can sense by touch
Specific heat
the amount of heat required to change 1lb of a substance by 1F
Heat is
energy in the form of molecular motion
subcooling types
- an increase in the subcooling of liquid refrigerant results in a decrease of sensible heat in the refrigerant
- a decrease in sensible heat results in a decrease in the amount of heat contained by the refrigerant
- a decrease in heat results in an increased capacity in the cooling section
The greater the temp difference between two objects,
the faster heat transfers
Conduction
solid
Convection
liquid or gas
Radiation
purely gas
Thermodynamics
study of changing heat energy into mechanical energy and mechanical energy into heat energy
The first law of thermodynamics states
energy cannot be created or destroyed
The second law of thermodynamics states
heat energy moves from a zone of high heat to a zone of low heat
high heat -> low heat
liquid water (specific heat value)
ice (specific heat value)
steam (specific heat value)
1.00 btu/lb/F
0.5
0.46
Sensible heat
a gain or loss of heat that is indicated by a rise or fall in temp
Latent heat
a gain or loss of heat that does not register a temp change
Total heat
the sum of latent heat and sensible heat
Q =
m x c x T
Q = Quantity of Heat
m = mass
c = specific heat
T = temperature difference
Temperature
the average amount of molecular motion in a substance