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Basic Refrigeration
quizes
| Question | Answer |
|---|---|
| discuss the procedure for a burn victim in the vicinity of energized electrical equipment | secure power, check vitals, provide comfort |
| what would provide the best protection from gas leaking from a refrigeration unit? | SCBA |
| Define a refrigeration ton. | 1200 BTU per hour. |
| describe the heat gained per. pound of refrigerant in the evaporator. | refrigeration effect |
| describe total heat. | latent & sensible = total |
| what kind of heat causes a change in temp | sensible heat |
| describe the heat compression. | heat removed by condenser from refrigent |
| define latent heat | change in state |
| what is specific heat | heat required per. unit mass to change one degree |
| define sensible heat | molecular motion seen on a thermometer. |
| In the refrigeration cycle, where will we find superheated vapor? | Inlet outlet of compressor |
| What is the metering device in a refrigeration system? | TXV = saturated liquid vapor mix |
| Describe the refrigerant when it leaves the metering device of the system. | Reducing flash gas |
| Why due we sub cool the refrigerant prior to the TXV? | To increase refrigerant effect by reducing flash gas. |
| What does the pressure in the control tubing of a TXV spend on? | Superheat in the tail coil. |
| Describe the condition when liquid is forced back to the compressor. | Flood back (liquid returning to the compressor) |
| Where does the refrigerant absorb the latent heat of vaporation? | Evaporator. |
| Describe where the latent heat of condensation is removed. | Condenser. |
| What PPE should be worn when handling contaminated oil? | Rubber gloves. |
| Define liquid slugging. | Liquid coming back to compressor from evaporator. |
| What is short cycling? | Frequent starting & stopping in a compressor. |
| If some refrigerants are burned, what is the result? | Odor,compressor burn out ,contamination in oil. |
| Describe the methods to determine if there is moisture in the refrigerant. | Color change in the moisture indicator. |
| Why do we install sight glass in the liquid line? | To see moisture, state of change. |
| What causes frost on the compressor suction line? | TXV (metering device) stuck open. |
| What causes the crankcase to sweat? | Flood back (liquid return to compressor) |
| What do you check first when the compressor doesn't start? | Power, fuses |
| What will result from the oxidation of the lube oil due to overheating? | Sludge |
| What causes crankcase oil to foam? | Refrigerant boiling out of solution with the oil |
| What do we do to prevent flashing in the liquid line? | Sub cooling in condenser. |
| When does an automatic compressor restart? | Suction pressure increases. |
| What causes the low pressure cutout switch to actuate? | Low refrigerant pressure. |
| What will happen if excessive foam occurs in the crankcase? | Bearing over heating. |
| What will cause the release of refrigerant from the oil/refrigerant mixture? | Sudden reduction of pressure at start up. |
| Define the refrigeration system between the expansion value & the compressor. | Low side |
| What components separate the high side from the low side? | Compressor, metering device |
| What does the compressor do? | Circulate refrigerante |
| What will cause the suction line temperature to increase? | Heat load increase |
| What occurs to the temperature of the refrigerant as it passes through the TXV? | Decreases to the lowest point |
| What will most likely occur if the evaporator coil becomes covered with frost? | Short cycle |
| What would cause high head pressure at the compressor | Dirty condenser coils |
| What will prevent the compressor from starting? | low refrigerant level will not cause L/P switch to acturate |
| What problems are assoc. with excessive circ of the lubricating oil with the refrigerant? | Evap temp will rise, too much oil in the system |
| Describe the operation of a refrigeration unit that is low on refrigerant? | Frequent cycling continuous starting |
| List the methods to determine if a unit is low on refrigerant | Bubbles in the sight glass |
| Describe the procedure to add refrigerant to the low side of an A/C system. | Add as a vapor to the suction side service value. |
| Describe the procedure for charging refrigerant. | purge charging line |
| What are the sources of moisture in a low pressure refrigeration system? | leaking tubes |
| Describe the procedure for admitting fresh air to a HVAC for the greatest efficiency. | As little as possible for proper ventaliation |
| What is the purpose of dehumidifiers in an A/C system? | Remove moisture |
| What type of refrigerant is R-12 | CFC |
| The ozone layer protects the earth from | UV |
| What chemical found in the upper stratosphere indicate that the ozone layer is being destroyed | Chlorine Monoxide |
| The state of the refrigerant leaving the condenser of a refrigerant system is? | h/t, h/p sub cooled liquid |
| Refrigerant entering the compressor of a refrigeration system is a : | L/T, L/P superheated vapor |
| Refrigerant entering the metering or expansion device of a refrigeration system is a : | H/T, H/P, sub cooled liquid |
| The low pressure gage is color coded | Blue |
| The component that changes a low pressure vapor to a high pressure vapor is: | Compressor |
| When heat is moved, the temp of the substance it moved from: | Drops |
| List the components that are contained in all mechanical refrigeration. | Metering Device, Evaporated, Compress, Condenser |
| List the four basic categories for the use of mechanical refrigeration | Comfort, Refrigeration, Process, Cryogenics (low temp work) |
| As the temp of any substance increase, the molecules which make it up vibrate: | Faster |
| When a substance changes state from a liquid to a gas, the spacing of its molecules: | Increase greatly |
| One pound of refrigerant will take up the most space in what state | Gas |
| List several good thermal insulator & therefore poor conductor? | Polystyrene = poor conductor Copper, Aluminum = good thermal insulator |
| To the refrigerant technician the most important type of heat is: | Latent |
| As 32°F liquid water is heated we witness: | Sensible, Latent, Sensible |
| A fluid (liquid or gas) is called saturated when: | It contains all the heat it can w/out change of state |
| In terms of refrigeration language, the water we drink is: | Sub cooled |
| The difference between a D-X coil & a cooler is: | D-X coil = cools air A Coolers = cools liquid |
| Your electric temp probe shows that the temp of the refrigerant in an evaporator is 40°F. It's condition is: | Need the pressure to determine refrigerant condition |
| Describe the shell on a chiller | Casing that encloses the evaporator & condenser |
Created by:
Rafael Leon