Control of the head pressure in an air-cooled condenser is done by.
3 Part Answer
1) cycling the condenser fan.
2) controlling dampers in the air-stream through the condenser.
3) flooding the condenser with refrigerant.
If the water flow is reduced the temp difference across the condenser will
Increase
condensing temperature in an air cooled condensing can be reduced by.
3 Part Answer
1) increasing the cfm through the condenser
2) increasing the condensing surface area
3) decreasing the temperature of air entering the condenser
Which of the following condenser is the most efficient
water cooled- counter flow
What can be used to maintain the head pressure of a system with a water cooled condenser
water regulating valve
the condenser in a refrigeration system.
3 Part Answer
1) Subcools the liquid refrigerant before it leaves the condenser(sensible heat)
2) Desuperheats the vapor from the compressor(latent heat)
3) condenses the vapor to liquid from the compressor ( sensible heat)
If an R-22 refrigeration system has it's air-cooled condensing unit on a 70*F roof, and the condenser outlet temperature (Liquid Line) is 90*F with how much subcooling is the condenser operating
10*F
A normally operating water cooled condenser is operating with a 10* differential between water in water out. If scale forms on the water tubes and the entering water is 85*F, which of the following is possible.
2 Part Answer
1) It will be less than the 10*F differential.
2) The system head pressure will rise.
The shell and tube condenser is cleaned how.
Mechanically with a brush after removing end caps(end boxes).
Which of the following will allow a system to operate more efficiently
Condenser that had refrigerent leaving with 15* of sub-cooling
In a water cooled condenser with dirty condenser tubes, the temperature difference between the refrigerant and the leaving water will be________ when the tubes are cleaned
Greater than
When a system with a water cooled condenser cycles off, the water regulating valve should
Close since the head pressure is low
Which of the following can be used to maintain the head pressure of a system with an air-cooled condenser.
3 Part Answer
1) condenser flooding valve (HPR)
2) Dampers or louvers
3) Fan cycling
The refrigerant in a condenser in a refrigeration system________________.
Gives up heat
An air-cooled condenser that is operating in a climate that has four distinct seasons must have ______________
Have some type of head pressure control
Mineral deposit in a water portion of a water cooled condenser act as ______________.
An Insulator
In a water-cooled condenser, a regulating vavle is used to control the _____________.
Refrigerant condensing temperature.
The water circuit in shell and coil, and coil type tube in a tube condenser must be cleaned
Chemically
A normally operating water-cooled condenser is operating with a 10* F differential between water in and water out. If the amount of 85* F water going through the condenser is reduced, which of the following is a possible temperature of the water leaving the condenser
greater than the 10* F differential, >96*
The temperature of the water coming into the cooling tower is 95* F and leaves the tower at 85* water temperature.
True or False
True
Low head pressure from low ambient temperature, can cause inefficient refrigerant flow rates through metering devices, which in turn starve evaporates.
True or False
True
Low suction pressure, ice coils, short cycling, and inefficient cooling can also result from high head pressures.
True or False
False
If the spring pressure of a water regulating valve is decreased, the system head pressure will also increase.
True or False
False
head pressure increases, opens valve, by increasing spring pressure
spring pressure decreases, closes valve,by decreasing head pressure
A water regulating valve helps to maintain a systems head pressure by modulating the flow of water through the condenser.
True or False
True
The desired water flow through a condenser connected to a circulated water system is 1.5 gpm. True or False
False
3.0 g.p.m.
The condenser rejects two types of heat
Two Part Answer
Latent (Hidden)
Sensible (measurable)
Condenser is the mirror image of what?
Evaporator
Water cooled is more efficient than air-cooled.
True or False
True
Three types of water cooled condenser.
3 Part Answer
Tube in tube
shell and coil condenser
shell and tube
Counter Flow
Refrigerant and water flow in opposite direction to maximize the heat transfer rate
Water cooled condensers have a design temp difference of how much?
10*F
In a recirculating condenser, what is the design temperature of water coming in, water coming out, condensing temp (refrigerant) coming out.
85*F
95*F
105*F
What will happen to the temperature of the exiting water and condensing temperature, if the line has mineral deposits.
Two part Answer
The exiting water temp will go down below the 95* design.
The exiting condensing pressure will go up above the design 105*F.
What happens in the first part of the condenser.
Desuperheat the gas flowing from the compressor. (Sensible Heat, Measurable)
What happens in the second part of the condenser.
the vapor condenses to a liquid, giving up the most heat in the system in this process. (Latent heat, not measurable)
What happens in the third part of the condenser.
The liquid is subcooled, cooling below the saturation point, (sensible heat, measurable)
What are the three types of cooling towers.
3 Part answer
Natural draft, Forced draft, Evaporative.
What are some of the ways a water tower cools the water.
evaporation, fans, prevailing winds
Five common types of head pressure controls.
5 Part answer
fan cycling devices, variable frequency drives(VFD) fans, air-shutters-dampers,condenser flooding devices, condenser splitting devices
three materials that condensers are normally made of.
3 Part Answer
Steel, Stainless steel, nickle
When is the most heat removed in the refrigeration process.
The second part, the condensation process. When vapor is condensed to a liquid, ( sensible heat,measurable)
When heat is absorbed in a water condenser, the heat can be deposited where.
It can be dumped into a drain (pump and dump), or it can be stored to be recirculated, through a tower or fountain, or retention pond.
A water cooling tower capacity is governed by what aspect of the ambient air.
Wet-Bulb temperature.
What is the condensing temperature of an air-cooled condenser if a standard, mid-efficiency,high-efficiency condenser is being used
_30__*F
_25__*F
_15__*F
Prevailing winds can effect which of the coolin towers
Natural Draft
The type of condenser that has the lowest operating head pressure is the _________ cooled compressor.
Water cooled
Compare the difference of standard and high efficient air-cooled condenser.
Standard air is 30 %, high efficiency is 10%
What is used to supply water that is lost in a cooling tower due to evaporation.
Float-type metering device
Name two problems that a refrigeration system will have if the condensing unit is exposed to a low ambient condition when not equiped with low ambient head pressure control valves.
the head pressure will be reduced and the metering device will starve.
The condensing pressure must be at least ____ psig than the evaporater pressure
75 psig
Author
salvatorefricano
ID
294053
Card Set
Condensers chapter 22
Description
air cooled, water cooled condensers, water cooling towers, chapter 22