Evaporator Pretest Quiz Flashcards
What is the function of the evaporator?
To absorb heat into the refrigerant system
The word “evaporate” really doesn’t fit what happens to the refrigerant in an evaporator because;
a) as the refrigerant absorbs heat, it boils
b) as the refrigerant absorbs heat, it condenses
c) as the refrigerant absorbs heat, it changes temp
d) none of these are true, refrigerant in the evaporator evaporates the same way water evaporates from the kitchen counter in your home
a) as refrigerant absorbs heat, it boils
The pressure temperature relationship in the evaporator is(
a) the evaporator is mainly a sensible heat transfer device
b) the evaporator is mainly a latent heat transfer device
c) refrigerant temperature and pressure changes very little in the evaporator
d) refrigerant temperature and pressure changes quite a lot in the evaporator
b) evap is mainly latent heat trnsf dev.
and
c) ref temp and press changes very little in the evap
The other names for a dry expansion evaporator are a ______________ evaporator and a _____ evaporator
direct expansion and DX
The flooded evaporator has the flow of refrigerant into it controlled so that it has;
a) mostly liquid refrigerant at its inlet but gas by the time it reaches its outlet
b) all its tubes wetted by liquid refrigerant from beginning to end
c) mostly liquid refrigerant at its outlet but gas at its inlet
b) all its tubes wetted by liquid refrigerant from beginning to end
On residential and small commercial products you should expect to find ____ evaporators
DX
The refrigerant leaving a flooded evaporator is;
a) just like that leaving a DX evap, slightly superheated
b) just like that leaving a DX evap, saturated
c) saturated, while that leaving a DX is slightly superheated
c)
refrigerant leaving a flooded evaporator is saturated and refrigerant leaving a dry evaporator is slightly superheated
True or False
True
Refrigerant entering a D-X evaporator is a mixture of _______ with _______
liquid with vapour
Flash gas comes from:
a) heat absorbed by the ref through piping as it travels from the condenser to the MD
b) heat absorbed by the ref through the piping as it travels for the MD to the Evap
c) an internal heat transfer from some of the refrigerant to that which becomes flash gas
d) the pressure drop which occurs at the MD
c) internal heat transfer from some of the ref to that which becomes flash gas
and
d) pressure drop that occurs at MD
As flash gas increases, evaporator capacity
a) increases
b) decreases
c) stays the same
d) it depends on the evaporator pressure
b) decreases
Superheat is provided at the outlet of a DX evaporator mainly to ;
a) improve evaporator efficiency
b) increase evaporator capacity
c) protect the compressor
d) increases system capacity
c) protect the compressor
An evaporator which fails to provide superheat at its outlet places which compressor in the most serious danger?
a) rotary
b) compliant scroll
c) reciprocating
d) screw
e) centrifugal
f) all equally
c) reciprocating
Bare tube, finned tube, and plate-surface evaporators are types which allow us to categorize evaporators according to their:
construction
T or F? A finned-tube evaporator is always the best choice for any job
False
A “prime-surface” evap is one of which:
a) has primer sprayed on it to protect it
b) is either a plate-surface or plate-finned type
c) is either a bare-tube or plate-surface type
d) uses only the primary surface, without fins, to transfer heat
c) a bare-tube or plate-surface type
and
d) uses only primary surface, without fins, to transfer heat
As the temperature of the medium which the evaporator cools goes down:
a) the number of coil rows tends to go _____
b) number of fins per inch tends to go ______
c) saturation temp of the refrigerant goes ______
d) the likelihood of forming ice on the coil goes ___
a) down
b) down
c) down
d) up
A chiller is an evaporator designed to cool ______ on brine
water
When the piping required for a job becomes extensive, water is ether than refrigerant because: (3)
a) it is less complicated
b) it is easier to install
c) it is less costly
d) it is smaller in diameter
a) it is less complicated
b) it is easier to install
c) it is less costly
A packaged, reciprocating liquid chiller is most likely to use a ____ chiller while a centrifugal chiller has a _______ chiller
DX
Flooded
Scale from water deposits Scale from water deposits will buildup and need to be removed periodically from: (2)
a) outside of the tubes of a DX chiller
b) inside of the tube of a DX chiller
c) outside of the tubes of a flooded chiller
d) inside of the tubes of a flooded chiller
a) the outside of the tubes of a DX chiller
and
d) the inside of the tubes of a flooded chiller
