[ILM] 102C Flashcards
condenser coil
dissipates heat from the refrigerant
evaporator coil
absorbs heat from the warm air passing across it
enthalpy
the amount of heat in 1lb of a substance starting from a zero-base point and at a universally accepted temperature
base point for refrigerants
-40F
entropy
a measure of change in a refrigerant’s molecular activity w/o a change in molecular structure while passing as a vapour through a refrigeration compressor
flow rate
the amount of fluid in motion passing a given point per a unit of time
Pascal’s law
the internal pressure of a gas remains the same throughout a closed system
static pressure
the pressure of a stationary fluid or the pressure perpendicular to the flow direction of a moving fluid
psia =
psig + 14.7
Dalton’s Law
the total pressure of a mixture of gases is the sum of each individual gas pressure
PT = p1 + p2 + p3 + … + pn
Bernoulli’s Law
an increase in fluid flow result in a decrease in the lateral or static pressure applied by that fluid
PT = static pressure + velocity pressure
up 2ft ==
up 1ft ==
1psi
0.5psi
Charles’ First Law
an increase in the absolute temperature of an ideal gas whose volume is constant will also result in a proportional increase in the pressure of that gas
p1 x T2 = p2 x T1 (Volume Constant)
convert to absolute pressure +14.7
Charles’ Second Law
an increase in the absolute temperature of an ideal gas whose pressure is constant will result in a proportional increase in the volume of that gas
V1 x T2 = V2 x T1 (Pressure Constant)
convert to absolute temperature +460
Boyle’s Law
p1 x V1 = p2 x V2 (Temperature Constant)
General or Combined Gas Law
a combination of the 2 Charles’ Laws and Boyle’s Law
p1V1T2 = p2V2T1
The standard in the refrigeration industry for static fluid pressure gain or loss is
0.5 psi/foot
Fluids that move through tubes and pipes lose pressure because of friction loss. Common factors are
- Tube length
- Tube diameter
- Tube internal smoothness
- Fitting type & shape
- Fluid weight
- Fluid viscosity (점성)
The long radius elbow has far lower friction losses than the short radius elbow
T or F
True
Refrigeration is measured by its
outer diameter
NRE ==
Evap outlet enthalpy - TXV outlet enthalpy
h3 - h1
HoC ==
Comp outlet enthalpy - Comp inlet enthalpy
h5 - h4
HoR ==
Comp outlet enthalpy - TXV inlet enthalpy
h5 - h1
Mass Flow Rate ==
m = system capacity/NRE
CoP ==
NRE/HoC
Higher CoP values result in effective system performance
CR ==
Saturated Discharge Absolute Pressure / Saturated Suction Absolute Pressure
Lower CR values result in greater system performance
Critical Point
a refrigerant’s condition where its liquid and vapour forms coexist and cannot change state
