Refrigeration Student Study Notes

GT109

Refrigerant Handling Safety

1. What happens to pressure inside a cylinder or a refrigeration system when a refrigerant is heated?

2. When a refrigeration cylinder is moved what safety precautions MUST be taken?

3. What is the purpose of a fusible plug or rupture disc on a pressurized cylinder?

4. What is the approved method for heating a refrigerant cylinder.

5. What two pieces of personal protective equipment will you use when working around refrigerant that could be released as the work proceeds?

6. What precautions MUST you take when working in cool or cold spaces?

7. What serious problems can occur if refrigerant gas leaks?

8. Why are refrigerant monitors placed in refrigerant storage areas?

9. Why must the fire department know about the amounts and types of refrigerants stored in your facility?

10. What precautions MUST be taking when handling chemicals or used refrigerant oil?

MECHANICAL REFRIGERATION CYCLE

1. Define refrigeration.

2. Sketch and describe the basic operation of a mechanical refrigeration cycle. State what the various parts do. Describe the state of the refrigerant in each section of the refrigerant cycle. Sketch in the division points.

THEORY

1. What is temperature?

2. What is the definition of a BTU?

3. Define heat and cold.

4. In which direction does heat always move?

5. What is the law of the conservation of energy?

6. What three factors determine the rate at which heat will flow?

7. What is forced convection?

8. What is sensible heat?

9. What is latent heat?

10. Where does a refrigeration system absorb and reject latent heat?

PRESSURE

1. What is atmospheric pressure at sea level?

2. What is gage pressure, pounds per square inch gage, psig?

3. How is vacuum expressed in refrigeration terms? (Complete vacuum = 29.92 in. Hg vacuum = 0 microns)

4. What happens to boiling and condensing temperatures a refrigerant as pressure increases and decreases?

5. Why should you not heat a can of refrigerant, an evaporator, or a condenser, with a torch or other extreme heat source?

6. If you know the pressure in the evaporator or condenser what else do you know?

7. What happens to the pressure of a refrigerant if air or another gas is mixed into the refrigerant?

8. Why do you need a high and low-pressure side to make a refrigeration system work properly?

9. Describe how a thermostat will control temperature in a cooled space.

10. When will you use a refrigerant pressure temperature chart?

11. Use the refrigerant pressure temperature chart to determine these values. (IN THE SEMINAR)

HFC-134a boils at °F at atmospheric pressure, at °F at 70 psi,

and °F at 150 psi.

CFC-22 boils at °F at atmospheric pressure, at °F at 70 psi,

and °F at 150 psi.

Ammonia, R 717 boils at -28 °F

COMPRESSORS

1. What is the purpose of a refrigeration compressor?

2. What is the difference between a hermetic compressor and a semi hermetic compressor?

3. What maintenance do compressors require?

4. Why should you not try to convert a refrigeration system from medium or high temperature to low temperature operation?

5. Why is a compressor burnout so terrible?

EVAPORATORS

1. What is the purpose of an evaporator? What is the boiling temperature in an evaporator called?

2. Why must an evaporator be colder than the surrounding air in the cooled space?

3. How does an evaporator remove moisture from the air?

4. Sketch and describe the operation of a dry type of evaporator under normal load.

5. What is relative humidity and dew point? How does ice form on an evaporator?

6. Describe the on-off method of defrosting.

7. What maintenance do evaporators require?

8. What is a S.E.E.R. rating?

CONDENSERS

1. What is the purpose of a condenser?

2. Sketch and describe the operation of an air-cooled condenser.

3. What is the condensing point in a condenser called?

4. Describe the operation of an evaporative condenser.

5. What maintenance do condensers require?

EXPANSION DEVICES

1. What is the purpose of an expansion device?

2. Describe the general operation of a thermo-expansion valve as it opens and closes.

3. Why do you generally want a ball park figure of 10 °F of superheat in an evaporator?

4. Describe the operation of a capillary tube.

5. What maintenance will expansion devices require?

6. Describe the operation of a fixed orifice metering valve.

7. Describe the operation and purposes of a receiver fitted with a king valve.

8. What is the purpose of a filter drier? How will you now if a filter drier is plugged?

9. What is the purpose of a suction line accumulator?

10. Where a sight glass located and what is its purpose?

11. Describe the purpose and uses for pressure access ports.

REFRIGERATION TROUBLESHOOTING

1. List the basic steps in troubleshooting a warm or cold call.

2. How will you maintain the desired relative humidity for the product being refrigerated?

3. How much colder should an evaporator be than the air flowing through it?

4. How much hotter should a condenser be than the air flowing through it?

HEAT PUMPS

1. Describe the operation of a heat pump in the cooling mode and cooling mode.

2. Describe the operation of a four way reversing valve.

3. What is the coefficient of performance?

4. Describe the general operation of an air to air heat pump defrost cycle.

5. When is the auxiliary heat used in a heat pump?

6. What special maintenance will air source heat pumps require?

7. What are the most common problems with air source heat pumps?

8. Describe the general operation of a geothermal heat pump.

9. Describe the general operation of a hot water heater using heat pump technology.

REFRIGERATION MAINTENANCE

1. List the general maintenance required by refrigeration systems.

2. Where will you learn the specific maintenance required by specific systems?

3. Describe how to use an electronic leak detector

4. Describe the purpose of evacuating a system.

5. Describe the general process of recovering refrigerant.

6. Describe the general process for charging a refrigeration system.