Powerpoint: Condensers Flashcards
A condensers function is to _______ heat from the refrigerant to the condensing medium
reject
Condensers cause the refrigerant to change state from a _______ to a _______
vapour to a liquid
The condenser must reject the heat absorbed in the _________ suction line and the compressor
evaporator
Name 3 condensing mediums;
Air
Water
Evaporative (mixture of air and water)
The condenser heat rejection is larger than evap/comp as it must reject heat from the ___________ , ______ line, and __________
evaporator, suction line, and compressor
_____ for open drive compressor capacity
1.25 x
______ for hermetic/semi hermetic compressors capacity
1.3
Fine size of condenser required for a ref. system with a hermetic compressor having a capacity of 24,000btu/hr?
24,000 x 1.3 = 31,200 btu/hr
Normal temp difference of ambient air to saturated discharge temp in a high efficiency compressor is?
15 degrees fahrenheit
Normal temp difference of ambient air to saturated discharge temp in a normal condenser is ____F to _____F
25 to 35F
Ambient temperature makes a huge difference in ___ ________ condensers
air cooled condensers
A ___F change in ambient temperature will change condenser capacity by 3%
10F
A 1F change in condenser sub cooling will change system capacity by ___%
0.5%
Sub cooling liquid temp MUST be colder than the ________ temp (temperature differential)
saturation
Name the two air condenser types.
Natural convection
Forced air
Name two forced air fans
propeller fan (draw through) centrifugal fan (push through)
Capacity control is required to maintain a proper pressure drop of ___ to ____ psig at the metering device
75 to 100psig
Capacity control is usually required if the outdoor ambient temperature falls below ___F
55
Name three air side capacity controls?
Fan speed, modulating dampers, fan cycling
Ref side capacity control characteristics:
The receiver is sized larger to accommodate refrigerant charge required to _____ the condenser
flood
Refrigerant side of capacity control:
The receiver may be equipped with a _____ (usually on small condensers)
heater
O.R.I valve?
Opens on a rise of inlet
measures condenser outlet pressure
O.R.D valve?
Opens on rise of differential
O.R.O.A valve?
Opens on a rise of outlet pressure automatically
Name three advantages of an air cooled condenser?
Air is readily available
Lower initial cost at installation
Simpler maintenance
No freeze up issues
Name three disadvantages of an air cooled condenser?
- Large volume of air may be needed
- Noise may be a problem
- Operating costs may be higher
- Large variations in discharge pressure due to ambient temperature swing
Name two methods of water cooled condensers?
Recirculating or waste water systems
Name the three types of water cooled condensers;
tube in tube, shell and coil, shell and tube
In water cooled condensers, the saturated discharge temperature is controlled by a water regulating valve set at between ___F and ____F
85 and 110F
The preferred location of the water regulating valve in a water cooled condenser is at the ______ condenser
outlet
why is the water regulating valve preferred location at the outlet of the water cooled condenser?
To prevent air from entering and increasing the rate of oxidation inside the condenser
How do you set the water regulating valve between 85 and 110 in a water cooled condenser?
Use the PT chart and find the pressure setting based on temperature and type of refrigerant and adjust valve based on these
The IDEAL saturated discharge temp of ____F is the ideal head pressure in a water cooled condenser
105F
In a water cooled condenser, the _____ pressure is the opening force of the water regulating valve and the ____ is the closing force
head, spring
______ head pressure is higher compression of the spring (water cooled condenser)
higher
______ head pressure is lower compression of spring (water cooled condenser)
lower
Name 3 advantages of water cooled condensers;
- Smaller size
- Constant SDT
- No requirement for capacity control during periods of low outside temp
Name three disadvantages of water cooled condensers?
- Not suitable for outdoor use
- water may be expensive
- bylaws may require an expensive recirculating system (cooling tower)
Evaporative Condensers use _____ and ____ as the condensing medium
water and air
Evaporative condensers are used on ______ capacity systems
larger
Evaporative condensers capacity is based on the _____ bulb temperature of air entering
wet
Wet bulb is based on ____ temp and ______ humidity
Air temp and relative humidity
In Evaporative condensers, as water evaporates, solids are left behind and concentrate in the ________ water
remaining
In Evaporative condensers, to prevent the dissolved liquids from over concentrating and forming deposits on the condenser tubes, a portion of the circulating water must be to ____
drain
In evaporative condensers, periodically the water must be emptied to flush out mineral deposits, this is called ____ ____
blow down
If Evaporative condensers are used in a cold climate the sump must be ______ or located in a _____ space
heated, heated
Condenser heat rejection factors:
- Surface Area of fins; __ to ___ fin/inch
8 to 16 fin/inch (more fins means more efficiency)
Condenser heat rejection factors:
- Type of Material used (thermal _______)
thermal
conductivity
Condenser heat rejection factors:
- ________ of surface
cleanliness of surface
Condenser heat rejection factors:
- Condensing medium temperature difference;
Air is ___ to ____F and 600 to 1200CFM @1000FPM
15 to 35F
Condenser heat rejection factors:
- Water flow rates;
- Waste water system (60F) flows at ____ gals/min/ton
Recirculating water system has a closed cooling tower and flows at ____ gals/min/ton
- 1.5
- 3
Maintenance required for water cooled condensers; Name 6
- Keep water passages _____
- Shell and could must be _______ cleaned
- Check condenser for ______
- _____ water valve
- Check water ____\____ temp
- Clean condenser coils with a commercial cleaning agent solution such as _______
- Clear
- Chemically
- leaks
- flush
- inlet/outlet
- cal-clean
