CH 51
The heat transfer rate for natural-draft evaporators is approximately _____.
1 Btu/hr×ft2×°F
Air-cooled condensers in commercial systems generally have a temperature difference of ____.
10°F-30°F
Liquid receivers should be sized ____ larger than the total liquid volume in a system.
15%
Total heat load represents the amount of heat that a commercial refrigeration system must remove in a(n) ____ period.
24-hour
For most refrigerant lines, the maximum allowable pressure drop is equal to a saturation temperature drop of ____.
2°F (1°C)
The heat transfer rate for forced-draft evaporators is approximately ____.
3 Btu/hr×ft2×°F
Which of the following statements regarding pressure drop is false?
As the length of the line increases, the pressure drop decreases.
The saturated suction line temperature can be calculated by subtracting the temperature difference from the design temperature of the ____.
conditioned space
A commercial refrigeration system's liquid line must always be insulated.
false
A double suction line should consist of two lines of equal size.
false
By decreasing the line size, a technician can decrease the pressure drop.
false
It is advisable to add 15%-20% to the calculated compressor load to ensure that the system components will not be undersized.
false
The lower the number of fins per inch (FPI), the greater the surface area of the evaporator.
false
The thicker the evaporator's material, the greater the heat transfer.
false
For a reciprocating compressor, the theoretical compressor volume is determined by the ____.
number of cylinders stroke bore Correct! All of the above
The required minimum velocity for a refrigerant line depends on the ____
size of the line temperature of the refrigerant Correct! All of the above. type of refrigeran
Once the relative humidity of the conditioned space is selected based on the product being refrigerated, the ____ can be determined.
temperature difference
The equivalent length for each fitting and valve in a line is added to the length of the line itself to find the line's ____.
total equivalent length
The total heat load for a system plus the energy added to the refrigerant by the compressor is the ____.
total heat of rejection
A smaller compressor with a longer operating cycle can be as effective as a larger compressor with a shorter operating cycle.
true
A suction line runs from the evaporator outlet to the compressor inlet.
true
Liquid refrigerant can collect in a compressor's cylinder head during the Off cycle when the discharge valves leak.
true
Low-temperature lines require higher velocities than high-temperature lines because oil flows less easily at lower temperatures.
true
Suction line problems can be avoided in a modulating refrigeration system by using a double suction line with one small line and one larger line.
true
The required capacity for the condenser is greater than the required capacity for the compressor.
true
The volume displaced by the piston on each stroke is the volume of refrigerant vapor moved through the compressor.
true
Traps installed in the suction line are intended to prevent a large slug of oil from returning to the compressor during start-up.
true
