HVAC Unit 21 Review Questions

What is the function of the evaporator in the refrigeration system

To act as a heat exchanger between air and refrigerant

Refrigerant in the evaporator
A. changes from vapor to liquid
B. changes from liquid to vapor
C. stays in the vapor state
D. stays in the liquid state

B. changes from liquid to vapor

The sensible heat that is added to a saturated vapor after all of the liquid has boiled away is referred to as

Boiling temperature

What determines the pressure on the low-pressure side of the system

Metering device

A refrigerant system's evaporator typically runs about ___degrees of superheat

8 to 12 degrees Fahrenheit

What does a high evaporator superheat indicate

A starved evaporator

A low evaporator superheat indicates
A. undercharge
B. system restriction
C. overcharge
D. dirt buildup

B. system restriction

Why is a multi-circuit evaporator used

Keeps excessive pressure drop from occurring

Flooded evaporators use a ___ type of expansion device

Float

An evaporator that is not flooded is though of as what type of evaporator

A dry-type evaporator

When an evaporator experiences a heat load increase, the suction pressure
A. remains constant
B. decreases
C. varies up and down
D. increases

D. increases

What is commonly used to defrost the ice from a low temperature evaporator

An electrical heater

A medium temperature refrigeration box operates within what temperature range
A. 28 F to 40 F
B. 40 F to 60 F
C. 0 F to -20 F
D. 0 F to 50 F

A. 28 - 40 degrees Fahrenheit

List seven advantages that an aluminum parallel-flow, plate/fin evaporator has over a standard round, copper-tube plate/fin evaporator

-reduces static pressure throughout coil
-reduces coil depth
-reduced internal volume
-reduced face area of condenspr/evaporator
-30% coil rate and size reduction
-reduction in packing costs
-lowe system costs