Chapter 6: Condensers
Where is the water box located on a vertical shell and tube condenser? (A) At the top of the shell (B) At the bottom of the shell (C) Next to compressor discharge (D) There are no water boxes on vertical shell and tube condenser
(A) At the top of the shell Water enters the water box at top of the vertical shell and tube condenser where there are swirls.
The state of the refrigerant as it enters and exits a condenser is as follows: (A) High pressure gas in, high pressure liquid out (B) High pressure gas in, low pressure liquid out (C) Low temperature liquid in, high pressure gas out (D) Superheated gas in, high temperature liquid out
(A) High pressure gas in, high pressure liquid out High pressure / high temperature refrigerant vapor enters the top of the shell and tube condenser. As the refrigerant vapor passes over the tube bundle (water in the tubes) the refrigerant gives up its heat to the condenser water. As the heat is removed from the refrigerant it liquefies into a high pressure / high temperature liquid refrigerant. This high pressure / high temperature liquid refrigerant exits the condenser at the bottom into the liquid line.
What statement is most nearly correct? (A) Operation of a spray pond and evaporative condenser are similar (B) Spray ponds use a recycling secondary such as ocean water or bay water (C) Induced draft condensers rely on stack effect (D) Air cooled condenser is similar to a spray ponds
(A) Operation of a spray pond and evaporative condenser are similar Both the evaporative condenser as well as an evaporative condenser rely of the evaporation of water in order to reject the heat from the (HPV) and liquefying it into a (HPL), therefore the operation of these systems are similar.
In comparing a shell and tube condenser with a similarly sized shell and coil condenser, it can be said that: (A) Shell and tube can be cleaned by punching the tubes (B) Shell and coil is clean with a special brush (C) Shell and coil generally last longer (D) Shell and tube generally weighs less
(A) Shell and tube can be cleaned by punching the tubes Given the choices given, this is the most relevant answer, remember always chose the better, most relevant answer based on the choices given on a multiple-choice test.
Which of the following best describes a vertical shell and tube condenser? (A) Suitable when the water source has a high potential for tube fouling (B) Has two water boxes (C) Require less room for installation (D) Has a vapor connection at the bottom
(A) Suitable when the water source has a highpotential for tube fouling Vertical Shell and Tube condenser is similar to the horizontal shell and tube in that the water is in the tubes and the refrigerant is in the shell, but the water only makes one pass through the tubes and is suitable when the condenser water is not clean.
How many baffles are there in a (3) pass, horizontal shell and tube condenser? (A) 1 (B) 2 (C) 3 (D) 4
(B) 2 The straight tubes are referred to as passes and the curved ends are referred to as baffles. The primary reason for the baffles is to collect droplets of refrigerant and aid in the circulation. There is always one more pass to the number of baffles.
In a Freon refrigeration system, a shell and coil condenser is to be replaced by a properly designed evaporative condenser. How much water will be conserved? (A) 40-50% (B) 85-90% (C) 50-65% (D) 0%
(B) 85-90% Remember whereas a cooling tower and shell and tube condenser relies on condenser water being circulated from the condenser to a cooling tower, in a evaporative condenser it is the (HPV) refrigerant that is circulated to an evaporative condenser coil, the refrigerant exits the coil as a (HPL). If this set up was put into place instead of a cooling tower, less water would be used as this system relies on water just being circulated in a basin thus requiring 85-90 % less water than the conventional cooling tower which circulates the condenser water.
What type of condenser can be used without water during winter conditions? (A) Shell coil (B) Atmospheric type (C) Vertical shell & tube (D) Submerged
(B) Atmospheric type Evaporative Condenser, rely on evaporation of water to cool the refrigerant. Refrigerant is circulated through a coil as the refrigerant is circulated water is sprayed over the coil to absorb the heat. In the atmospheric evaporative type of condenser a fan is used to remove the heat either forced or induced.
In comparing a air-cooled refrigeration system with a similarly sized water cooled type, which of the following would be correct, assuming normal operating conditions? (A) Head pressure for the waterless would be lower (B) Head pressure for the waterless would be higher (C) Aqua pump is lower than the condenser (D) Suction pressure is continually the same
(B) Head pressure for the waterless would be higher An air-cooled condenser relies on outside air that is circulated though the condenser coil in order to liquified the refrigerant, whereas a flooded or water type condenser uses condenser water as well as a cooling tower to reject heat to the atmosphere, therefore a waterless type of condenser would usually run at slightly higher pressures due to only relying on air to liquefied refrigerant vapor.
Which of the following best describes the function of the eliminators which are located within an evaporative condenser? (A) Eliminate gas noises and vibrations (B) Prevent moisture carry over (C) Conserve energy (D) Control the gas flow
(B) Prevent moisture carry over In the Atmospheric evaporative type of condenser, a fan is used to remove the heat either forced or induced. There are eliminators at top to eliminate moisture carry-over.
Water leaving a horizontal shell and tube condenser is usually: (A) Somewhat warmer than the discharge gas (B) The same temperature as the discharge gas (C) A little cooler than the discharge gas (D) The same temperature as the cooling water
(C) A little cooler than the discharge gas It is the condenser water which removes heat energy from the (HPV) thus, liquefying it and turning it into an (HPL), the leaving condenser water however is usually lower than the discharge gas temperatures. Remember Heat flow from a warmer to a cooler mass therefore there has to be a temperature spread for heat to flow.
How will low condenser pressure affect the operation of a refrigeration system? (A) Less refrigerant will be liquefied (B) System will shut off on low pressure cutoff (C) Evaporator will not be fed properly (D) Frost will form on the suction line and compressor inlet
(C) Evaporator will not be fed properly High pressure refrigerant vapor condenses, turn into a high-pressure refrigerant liquid inside the condenser. This (HPL) has enough energy built into it to travel through the metering device and into the evaporator due to pressure difference, remember high pressure seeks low pressure, however, if the pressure of the liquid refrigerant is low, it will not have sufficient force to go through the metering device into the evaporator.
The rate of heat transfer in a condenser will: (A) Increase as the velocity of the water in the tubes increases (B) Shows only a small increase if the tubes are de-scaled (C) Increase with a lower mean average condenser water temperature (D) Increase as the wet bulb temperature increases
(C) Increase with a lower mean average condenser water temperature In a condenser heat from the (HPV) is transfer to the condenser water, therefore, the cooler the condenser water, the faster the heat transfer. If the condenser water has a lower mean average condenser water temperature this heat transfer will be more efficient.
Which best describes the type of heat rejected from a condenser? (A) Latent heat (B) Sensible heat (C) Latent and sensible heat (D) Heat of compression and latent heat
(C) Latent and sensible heat Condensers liquified refrigerant by changing or causing the refrigerant to change from a gas or vapor to a liquid. They reject heat from the refrigerant cycle (both latent and sensible heat).
In a spray pond condenser, which of the following would be used to kill algae? (A) Silica gel (B) Chromate (C) Potassium-permanganate (D) Potash
(C) Potassium-permanganate In a Spray Pond system, we use potassium permanganate to killAlgae and a well-maintained water treatment program will minimize bacteria growth and corrosion.
Which of the following statements in a regard to a double pipe condenser is most correct? (A) Refrigerant and water enter at the top (B) Refrigerant is in the inner pipe, water is in the outer pipe (C) Refrigerant is in the outer pipe, water is in the inner pipe (D) Ammonia and water enter at the bottom
(C) Refrigerant is in the outer pipe, water is in the inner pipe In a Double Pipe condenser, the water is enclosed in the refrigerant coil, assembled of two tubes one within the other, this is considered a counter flow heat exchanger because the water and refrigerant enter at opposite ends. Refrigerant is in the outer pipe, water is in the inner pipe.
According to recommended practice, to clean a shell and coil condenser of scale deposits an operator should use: (A) Specially made nylon brush (B) Combination of brush and scraper (C) Solution of inhibited hydrochloric acid (D) Weak caustic soda solution
(C) Solution of inhibited hydrochloric acid In the Shell and Coil condenser the refrigerant is in the shell and the water is in the coil. To clean the inside of the coil with a solution of hydrochloric acid due to the multiple baffles and passes.
In which type of condenser is a swirl used? (A) Shell and coil condenser (B) Horizontal shell and tube condenser (C) Vertical shell and tube condenser (D) Atmospheric condenser
(C) Vertical shell and tube condenser Water enters the water box at top of the vertical shell and tube condenser where there are swirls. These swirls circulate the water in a circular motion so the water comes in contact with as much surface of the tube as possible.
A vertical shell and tube condenser has swirls at the top of each of its tubes. If a few of them became blocked, what could the result be? (A) A slow down of the compressor (B) A drop in suction pressure (C) An increase in plant capacity if the suction pressure is constant (D) A need to increase water flow to the remaining spray heads to prevent head pressure from rising
(D) A need to increase water flow to the remaining spray heads to prevent head pressure from rising Block swirls on a vertical shell and tube condenser will limit the heat transfer thus decreasing the capacity of a system, an operator should increase water flow to make up for the decreased water flow to prevent a high head pressure condition.
The amount of sub-cooling that takes place in a refrigeration system is indication of which component's performance? (A) Compressor (B) Evaporator (C) Metering device (D) Condenser
(D) Condenser Condensers are rated by their ability to sub-cooling the liquid refrigerant, sub-cooling refers to any additional temperature drop experienced in the condenser by the liquid refrigerant. For example: an R -22 system high side pressure is 210 PSI with a corresponding temperature of 105 Degrees Fahrenheit, 105 is the temperature at which the refrigerant changes state from a vapor to a liquid, any additional heat lost by the refrigerant after it has changed to a liquid is a function of the effectiveness of the condenser and is referred as sub-cooling. The liquid line of such system may be at a temperature of 95 degrees Fahrenheit or 10 degrees sub-cooled.
