Powerpoint: Receivers/Evaporators Flashcards
Filling receivers with liquid is ______
illegal
A receiver is essentially a _______ tank for refrigerant
storage
The receiver is a _____ side component
high
The Receiver inlet is from the _________ and the outlet goes to the ______________
condenser, metering device
Refrigerant receiver types;
Full size receiver: holds _______ system charge
holds entire system charge
Refrigerant receiver types;
Oversized receiver: holds ______ system charge (condenser flooding)
excess
Refrigerant receiver types;
Partial receiver: holds a ______ of the system charge and the rest in condenser (not in canada)
portion
What are the inlet and outlet valves called in a full size receiver?
Inlet - Queen valve
Outlet valve quill- King valve
Inlet and Outlet valves in a partial receiver?
Inlet - no valve
Outlet valve quill - King
Receiver capacity as required by B-52:
- Must hold the entire refrigerant charge and only occupy ___% of its volume at ___F
- If refrigerant side head pressure capacity control is used the receiver must be oversized by ___%
- 90%, 90F
2. 50%
A cooling tower is a device for cooling water on a __________ system
recirculating
Cooling towers have no ________
refrigerant
Cooling towers use water to ______ heat from the water
reject
In a cooling tower, water is pushed to the ____ of the tower from the water cooled condenser and heat is rejected and _______ out the top
top
rejected and removed out of the top
Cooling tower low ambient controls;
- _______ valve
- diverting _____
- fan ______ ______
- mixing valve
- diverting valve
- fan speed control
Evaporators _______ heat into the refrigeration system
absorb
Evaporators absorb heat by maintaining the evaporator at a temperature ______ than the medium to be cooled
lower
Evaporators remove both ______ heat and _______ heat from the medium to be cooled
latent heat and sensible heat
Evaporator types:
- Dry (DX): Liquid/Vapour mix to start and a ____ at the exit
- Flooded:
- _____ level of liq ref (used on direct or indirect systems)
- Ref charge of flooded evap is _____than a DX evap
- Used for ______ systems (ie. ice rinks)
- gas
2. Constant, larger, larger
Construction of Evap:
- Bare pipe
- Finned Tube: fins increase surface area and attach to pipe to increase __________
- Plate: (may use eutectic solution) semi trucks and______ low freezers
- Shell and tube: flooded or dry indirect systems seen in chillers
- heat exchange
3. ultra low
Finned tube type: ____ velocity
temperature range is ___F and above
28
Unit cooler temperature range is ____F and above (most common)
-40F and above
Product cooler temp range is ____F and above and is the largest evaporator
-40F and above
- Fin spacing and temperature application:
- Frosting application- product coil must be below ___F (approx __fin/inch)
- Defrost method must have an external heat source to raise temp above ____F
- When in defrost you must shut off the evap ____
- External heat sources could be hot ____, ______, or hot _____
- Frosting application- product coil must be below ___F (approx __fin/inch)
- 32F, 4fin/inch
- 32F
- fan
- hot gas, electric, hot water
- Fin spacing and temperature application:
- Defrosting application- coil must be below ___F and product above ___F (approx __fin/inch)
- Defrost method is ___/_______
- keep the evaporator fan ________ during defrost
- Defrosting application- coil must be below ___F and product above ___F (approx __fin/inch)
- 32F, 32F, 6fin/inch
- air / positive
- running
- Fin spacing and temperature application:
- Non-frosting application -coil above ___F (approx __fin/inch)
- The defrost method is ____ required
- Improved fin designs reduces stratification by causing _______
- Non-frosting application -coil above ___F (approx __fin/inch)
- 32F, 8fins/inch
- not required
- turbulence
DEFROSTING METHODS;
- Electric (most common): lower first cost higher operating cost, ____ and _____ released into the space
- Hot gas (most efficient): ____ defrost with minimal _____ temperature rise
Hot water (not common): ____F water is sprayed onto a coil at 3GPM, has ____ defrost but requires more maintenance
- heat and moisture
- fast, minimal space temperature rise
- 50F, fast defrost
What are the three methods of stopping the defrost cycle known as defrost termination?
- Time
- Temperature
- Pressure
Defrost Termination:
Defrost timers with a solenoid can terminate defrost by ____ and _______
time and temperature
Defrost Termination
Defrost timers with a solenoid are for ___ temp
low
Defrost Termination:
Defrost timers without a solenoid are for ____ temperature
medium
Defrost Termination:
Defrost timers without a solenoid can only terminate defrost by ____
time
Coil temperature difference (TD):
this determines ______ humidity level
space
Coil Temperature difference:
Evaporator coil TD= Air entering Evap - ____
SST
Normal coil TD’s and Relative Humidity:
- 8 to 10F =
- 10 to 12F =
- 12 to 14F =
- 14 to 18F =
8 to 10 = 90% +
10 to 12 = 85% to 90%
12 to 14F = 80 to 85%
14 to 18F = 70 to 80%
Purpose of refrigerant distributor:
- Has multiple _____/ multi- circuit ____
- Eliminates ______ drop thru long coils by feeding ref. thru multiple circuits within the coil
- provides equal _______ of liquid and vapour to each coil circuit
- branches/multi circuit coils
- pressure drop
- distribution
Capacity control for evaporators:
- Coil splitting methods; _____/row split (stacked), _____/face split (in line)
- vertical, horizontal
Shell and tube evaporator types;
2
Dry (DX) and Flooded
Shell and Tube Evaporators:
- Dry- location of primary ref is on the ____ side and secondary ref on the ____ side
- Purpose of baffled (full or half) is to provide maximum exposure of secondary ________ to primary refrigerant circuits
- Tube, Shell
2. refrigerant
Shell and Tube Evaporators:
- Flooded- location of primary refrigerant ____ side and secondary ref on ____ side
- Tube bundle on ______ of shell
- Purpose of ________ is to prevent liquid ref from returning to the compressor
- Surge drum (accumulator) provides for removal of _____ gas so it does not waste space in the cooler
- shell side, tube side
- bottom
- eliminators
- flash gas
Evaporator Capacity or Efficiency control:
- _____ water flow at all times
- Temperatures: low temp __F TD (secondary refrigerant entering/leaving)
- High temp application ___ to ___F TD (secondary refrigerant entering/leaving)
- Air Cond. chilled water supply at ___ to ___F
- Air conditioning supply air temp ____F
- Secondary ref controlled by ______ conditions
- constant
- 2F
- 10 to 15F
- 40 to 45F
- 55F
- entering
