WorksheetsRefrigeration Final
Total questions: 69
Worksheet time: 3hrs 25mins
A ton of refrigeration is equal to (a) BTUs per hour?
The three states of matter are?
Solid
Gas
Liquid
Round
A column of 30 ft of water is equal to a pressure of:
10.2 psi
12.9 psi
62.4 pounds per square foot
15.6 inHg
When an object is refrigerated:
Some of its heat is destroyed
More cooling is added
Heat is removed from it
Its molecules move faster
Water boils at (a) deg F when exposed to atmospheric pressure?
Absolute zero is calculated to be (a) deg F?
The unit to measure the amount of heat removed or added to a substance is the:
BTU
Deg C
Deg F
Joules
The boiling point of a liquid:
Increases at the elevation above sea level
Depends on the absolute pressure
Depends on the radiation
Depends on the specific heat of a substance
If a pressure gage reads 5 psi at sea level elevation, the corresponding absolute pressure is (a) psia?
When a pound of water is heated from 32 deg F to 212 deg F it gains:
970 BTU of latent heat
180 BTU of sensible heat
144 BTU of latent heat
The heat of fusion
The low side of a vapor compression cycle contains the:
Condenser
Evaporator
Compressor discharge line
Condenser and evaporator
The boiling point of refrigerant in the condenser is the same as:
Evaporator temperature
Condensing temperature
Compressor suction temperature
Condensing pressure
Of the following items, the largest amount of heat removal in BTUs for one pound of water is:
Its sensible heat
Its latent heat of fusion
Its latent heat of vaporization
Its latent of melting
If the evaporator in a vapor compression cycle is not cold enough, it can be made colder by:
Raising the evaporator pressure
Lowering the evaporator pressure
Stopping the compressor temporarily
Venting the refrigerant to the atmosphere
The purpose of the condenser in the vapor compression cycle is to:
Save the refrigerant for re-use
Reduce the evaporator pressure
Reduce the superheated vapor to evaporator temperature
Lowering the condenser pressure
In the vapor compression cycle, the compressor:
Heats the refrigerant vapor
Compresses the refrigerant vapor
Reduces the evaporator pressure
All of the above
Water can be made to boil at 50 deg F by:
Subcooling it to 50 deg F
Placing it under a high enough vacuum
Reduce the pressure to 14.7 psia
Lowering the pressure to atmospheric pressure
An example of a halogen is:
Sulphur dioxide
Carbon dioxide
Butane
None of the above
A fluid…….
Cannot exist in a vapor
Must be in a liquid state to be fluid
Can be either a liquid or a solid
Can be either a liquid or a gas
Refrigerant HCFC-22 is a:
Halogenated hydrocarbon
Chlorinated hydrocarbon
Halocarbon
Any of the above
The purpose of wearing goggles when handling halocarbon refrigerants is to avoid:
Being irritated by the fumes
The possibility of freezing the eye
Toxic effects
The danger of phosgene
A non-condensable gas in a refrigeration system can be:
Carbon dioxide
Air
Methane
All of the above
In transferring refrigerant from one cylinder to another, it is a good idea to avoid filling the cylinder more than (a) % full.
Air in a refrigeration system results in:
An increase in compressor discharge temp
Lower condensing pressure
A decrease in condensing pressure
Less moisture in the system
A shaft seal is required in:
A hermitic compressor
An open compressor
A semi hermetic compressor
All of the above
As compared to the speed of the prime mover, the speed of a direct drive compressor:
Is always the same as that of the prime mover
Is slower
Depends on the relative size of the drive pulleys
Is usually faster
Operation of the compressor changes conditions within the refrigeration system. The compressor ________condenser pressure.
Increases
Decreases
Operation of the compressor changes conditions within the refrigeration system. The compressor ________evaporator pressure.
Increases
Decreases
Operation of the compressor changes conditions within the refrigeration system. The compressor ________evaporator temperature.
Increases
Decreases
Operation of the compressor changes conditions within the refrigeration system. The compressor ________condenser temperature.
Increases
Decreases
One type of compressor is the helical-rotary, name one other type of compressor?
(a)
Of the four essential components of the vapor compression cycle, the condensing unit contains? Choose all that apply.
Compressor
Condensing coil
Metering device
Evaporator coil
For determining the size of an electric service to supply a hermetic compressor motor, you should know the:
Rated HP
KW Input
Brake HP
Motor speed at rated frequency
For compressors having a lubricating oil pump, the pressure which pushes oil through the compressor oil passages is equal to:
Oil pump suction pressure plus compressor suction pressure
Oil pump discharge pressure minus compressor suction pressure
Compressor suction pressure plus oil pump discharge pressure
Compressor discharge pressure minus oil pump discharge pressure
When refrigerant becomes dissolved in the lubricating oil in a reciprocating compressor:
The thinner mixture improves lubrication
The oil pump can more easily develop pressure
The flashing of the refrigerant cools the oil to improve lubrication
Oil foaming can increase when the compressor starts
The purpose of a crank case heater on a motor/compressor is to:
Keep the viscosity of the oil low so it will flow easily
Carbonize the oil
Keep the refrigerant boiled out of the oil
Make starting the compressor easier by reducing the starting torque
A compressor operates under the conditions such that its volumetric efficiency is 70%. If the discharge pressure increases but the suction remains unchanged, volumetric efficiency will:
Be greater than 70%
Remain at 70%
Be less than 70%
Depend on the percentage change in clearance volume
The capacity of a reciprocating compressor ________ as the discharge pressure decreases?
Increases
Decreases
The piston in a reciprocating compressor makes a compression stroke and a suction stroke, each of these two strokes being divided into two parts to make a total of four parts or functions for each cycle of the piston. These four parts or functions are compression, discharge, re-expansion and ____________.
Suction
Evaporation
Condensing
Fusion
Cooling tower drift is:
Movement of a spray pond
Evaporator loss
The same as bleed off loss
None of the above
Algae is:
A growth of tiny animals
A plant growth
A bacteria
Composed of chemical fumes
The proper location of a cooling tower blead off is:
At the high point of the piping system
At the pump suction
At the low point of the piping system
Just below the tower basin
A once through condenser water system is supplied with water at 75 deg F, and the water leaves the condenser at 87 def F. How many BTUs does each pound of condenser water carry off?
120 btu/lb
1.2 btu/lb
12 btu/lb
12,000 btu/lb
A refrigeration system having a water-cooled condenser has the following operating conditions.
System capacity= 10 tons
Condenser water flow rate= 30 gpm
Heat rejection rate= 15,000 BTU/hr/ton
Water enters condenser at 87 deg F
Calculate the temperature of the water leaving the condenser.
85 deg F
97 deg F
95 deg F
107 deg F
The lowest temperature water obtainable from a cooling tower is limited by the _________ temperature.
Fan speed
Dry bulb
Wet bulb
Water flow rate
1. Cooling towers can be constructed in several arrangements as concerns the relative directions of water flow and air flow. Three such arrangements are parallel-flow, counter-flow and (a) .
A recirculating condenser water system having a cooling tower removes approximately __________BTUs for each pound of water evaporated in the tower.
1,000
100
12,000
15,000
Cooling towers contain a number of items which should be cleaned to assure adequate flow of water through the tower. Name one.
(a)
A refrigeration system has a hand-operated needle valve for the refrigerant expansion device. If refrigeration load and suction pressure remain constant, a decrease in condensing temperature will:
Result in greater refrigerant flow
Increase available pressure difference
Result in reduced refrigerant flow unless valve is opened more
Be automatically compensated for
The proper location of a high-side float is:
Between the evaporator and the compressor
Between the receiver and the condenser
Between the evaporator and the condenser
After the expansion device
The low-side float should be located:
Between the evaporator and the compressor
Between the condenser and the receiver
Between the compressor and the condenser
Between the expansion device and the evaporator
The advantage of a capillary tube is that:
It is less likely to become stopped up
It avoids pressure equalization during shutdown
It allows for use of a less expensive compressor motor
It closes when the compressor stops
A constant pressure expansion valve:
Maintains constant evaporator pressure
Maintains constant refrigerant flow
Adjust compressor load to actual load
Varies suction pressure according to load
The thermostatic expansion valve measures:
Superheat only
Condenser pressure and superheat
Evaporator pressure and superheat
Pressure at the evaporator outlet
When a compressor service valve is front seated:
The compressor is connected to the discharge piping.
The back seated gage port is closed to the compressor.
The compressor is shut off from the hot gas line.
And if the valve has a front seated gage port, this port is closed to the discharge line.
When a compressor service valve is back seated:
The compressor is connected to the discharge piping.
The back seated gage port is closed to the compressor.
The compressor is shut off from the hot gas line.
And if the valve has a front seated gage port, this port is closed to the discharge line.
To protect a large compressor against excessive compressor discharge you could use:
A fusible plug.
A magnetic check-valve.
Either a fusible plug or a rupture disk.
A spring-loaded pressure relief valve.
Hammer blow action in a solenoid valve is intended to:
Make the valve close more positively.
Increase the magnetism of the solenoid armature.
Help open the valve.
Allow the valve to close gradually.
To prevent evaporator temperature from falling too low, you could use:
An evaporator pressure regulator.
A hold back valve.
A suction pressure regulator.
A crank case pressure regulating valve.
Receivers are usually required in systems having:
Cooling towers.
Evaporative condensers.
Shell and tube condensers.
Pump down control.
An important feature of a refrigerant receiver, in the case where the liquid line to the evaporator comes out of the top of the receiver, is a:
Gage glass.
Drain valve.
Liquid level test cock.
Dip tube.
If a refrigerant sight glass shows bubbles, you know:
There is air in the system.
There is gas in the liquid.
The system has too much refrigerant.
A restriction must be causing flash gas.
A liquid refrigerant receiver has two liquid level test cocks, one near the top of the receiver and one near the bottom. If the system contains enough refrigerant, when the lower cock is opened:
Refrigerant vapor should come out of the test cock.
The test cock should discharge liquid refrigerant.
Water should drain out.
The dip tube should become completely drained.
Desiccants are used in:
Strainers.
Moisture indicators.
Gage glasses if combined with moisture indicators.
Driers.
A refrigerant heat exchanger might cause:
Too much sub cooling for proper operation of the expansion valve.
The compressor to become overheated.
Flash vapor in the liquid line.
The suction line to sweat.
The purpose of a suction line accumulator is to:
To trap and accumulate the non-condensables.
Trap oil.
Accumulate excess vapor.
To trap liquid refrigerant.
If not properly installed, a hot gas muffler might trap:
Oil.
Hot gas.
Suction gas.
Superheated vapor.
The proper location of an oil separator is near the:
Compressor.
Condenser.
Receiver.
Evaporator.
The oil separator is intended to remove oil from the (a) pipe.
