RAC 40 Quiz 3 Review Questions with Correct Answers (Already Graded A+)
What is another word for flash gas? - Answer- Adiabatic expansion
What is the meaning of THOR? - Answer- Total heat of rejection
What will high discharge temperatures affect your compressor? - Answer- It will cause the...
RAC 40 Quiz 3 Review Questions
with Correct Answers (Already
Graded A+)
What is another word for flash gas? - Answer- Adiabatic expansion
What is the meaning of THOR? - Answer- Total heat of rejection
What will high discharge temperatures affect your compressor? - Answer- It will cause
the oil temperature to rise and create acid. Acid will eat at the winding in the compressor
and cause a short.
Name the 4 positive displacement compressors. - Answer- Reciprocating, Rotary,
Scroll, Screw
When engineers design air conditioning units what parameters are used. - Answer- A
pressure/enthalpy chart. On the chart it shows pressure and btu/lb, it also shows
saturation points of liquids and vapors.
What temperature will the Hawaii health department use to gauge med temp chill boxes
and low temp freezers? - Answer- Chill box 35-40 degrees F
Freezer 0--10 degrees F
What is the process of refrigeration? - Answer- Removing heat from a place where it
isn't wanted to a place where it makes little or no difference.
How does refrigeration slow down food from spoiling? - Answer- It brings down the
temperature of food so that bacteria growth begins to slow down.
It takes ___ btu of heat energy to melt 1lb of ice at 32F - Answer- 144 Btu
Why are evaporators usually feed from the bottom? - Answer- Because vapor naturally
rises and ther is time for the liquid in the evaporator to boil off before it enters the
compressor.
What type of equipment would you find R-410a refrigerant in? - Answer- Ductless split
units
What type of equipment would you find R-404a refrigerant in? - Answer- Low temp and
Medium temp refrigeration
, What type of equipment would you find R-407c refrigerant in? - Answer- Chill box, R-22
retrofit, Commercial refrigeration
What type of equipment would you find R-134a refrigerant in? - Answer- Automotive,
Low temp, Medium temp, High temp
What type of equipment would you find R-401a refrigerant in? - Answer- Medium temp
refrigeration, Low temp, R-12 replacement
Explain what the evaporator does? - Answer- The evaporator is a bundle of tubing that
absorbes heat from the system. It also boils off liquid refrigerant to bring down the coil
temperature, and makes sure no liquid refrigerant returns to the compressor.
Explain what the compressor does? - Answer- The compressor is also known as a
vapor pump. There should only be 100% vapor going through the compressor. The
main job of the compressor is to pump refrigerant through the system.
Explain what the condenser does? - Answer- The condenser is a bundle of tubing, it's
main job is to reject heat from the system. The condenser also desuperheats the hot
vapor refrigerant coming from the compressor and condenses it into liquid.
Explain what the metering device does? - Answer- The metering device controls the
flow of refrigerant going into the evaporator. It changes the 100% liquid from the
condenser and makes it 25% vapor 75% liquid going into the evaporator.
Explain system superheat? - Answer- System superheat is the amount of heat the
refrigerant vapor picked up from the exit of the evaporator to the inlet of the compressor.
It's measured the same way as superheat and should be around 20F
Explain system subcool? - Answer- System subcool is the amount of heat the
subcooled liquid has cooled off from the exit of the condensor to the inlet of the TXV.
System subcool should be around 15-20F
The _____ compressor is another positive displacement compressor and is used for
larger air conditioning and refrigeration applications. - Answer- Screw Compressor
The four (4) major components of a vapor compression refrigeration system are the
compressor, condenser, evaporator, and ________ ______. - Answer- Metering device
The amount of heat a refrigerant contains with -40F as the 0 heat content reference
point is called - Answer- Enthalpy
From a performance standpoint, a substitute for R-12 is - Answer- R-134A
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