Condensers MCQ Quiz - Objective Question with Answer for Condensers - Download Free PDF

Explanation:

High-pressure control (HPC) switch:

• A pressure switch is a device that opens or closes a set of contacts when a certain pressure is applied to the diaphragm of the switch, thus protecting the system from excessively high or low pressures.
• A high-pressure switch is connected to the discharge, or the “high” side of the system to sense discharge pressure.

Need of HPC control switch:

• When the AC pressure is too high, the interior temperature becomes too hot to survive on a sunny day. 
• This situation indicates an underlying issue with the unit, and it’s slowly getting damaged.
• The first part that may fail is the compressor, which is very costly to repair or replace.
• A major reason for high pressure is limited airflow or no airflow passing through the condenser due to blockage.
• Therefore, HPC control switches are installed to sense the condenser pressure.
• If the condenser pressure is too high, the HPC switch senses high pressure and cuts off the power supply to the AC unit.

Explanation:

Condenser coil straightening:

• The condenser coil is made up of copper tubing surrounded by thin metal fins.
• These fins can easily get bent and obstructed, restricting airflow and causing an unnecessary load to be placed on the unit.
• This can result in increased energy usage, poor performance, and even premature failure of the unit.
• To straighten these fins, a tool called fin comb is used.

​Fin comb:

• A fin comb, also known as a coil fin tool, is a specialty tool used to straighten the bent fins of a condensing unit for an air conditioning or heat pump system.
• Most fin combs feature a handle with a comb on the end.
• Some fin combs feature multiple combs that can be spun or otherwise shifted into place in order to accommodate multiple fin sizes.
• Fins are measured in FPI (fins per inch), so figuring out what size one needs is as simple as measuring and counting how many fins there are in an inch.

Explanation:

Explanation:

Air-cooled condensers:

• In this type of condenser, the heat released by the refrigerant is taken away by the air.
• The air can be either natural convection or forced flow.
• Such condensers are used in freon refrigerators for inconvenient or difficult water supply.
• These are usually made of copper tubing with thin fins assisting rapid radiation.
• Air-cooled type of condensers are used for ≤ 3 Tons cooling capacity of a refrigeration unit.

These are mainly of two types

1. Natural air-cooled condensers:
   • In the natural convection type, heat transfer from the condenser is by buoyancy-induced natural convection and radiation.
2. Forced draft condensers:
   • In forced convection-type condensers, the circulation of air over the condenser surface is maintained by using a fan or a blower.
   • Forced air-cooled condenser fins are made up of Aluminum.

Fin-type forced air-cooled condenser:

• In this type the fins are provided vertically on a frame.
• The fins are like a thin rod (2 mm diameter) evenly welded in the proper interval to the frame.
• The condenser coils will be clamped and soldered to the fins.
• The frame is fit at the back wall of the fridge, tighten the screws.
• The natural air passes through the fins (distributed) and the condenser coils get cool.
• The pollution of air, the condenser fins will get a coating of fine dust.
• The dust over the condensing tubes will affect the heat transfer efficiency of the condenser.
• That can be cleaned periodically.

Plate-type air-cooled condenser:

• In this type, the condenser tubes are soldered to a metal plate and the plate will be fixed at the back of the fridge- tighten by the corner screws.
• The condensation takes place through natural air ventilation.
• Condenser tubes give up heat to the plate by conductivity and the plate surface is cooled by natural air velocity.
• So always, it is advised to keep a distance minimum of 15 cm from the wall to the fridge backside for free air circulation.
• The condenser tubes are fixed inner side of the plate and if the dust covers the tubes or plates can be cleaned with a weak soap solution to increase the condenser's performance.

Explanation:

Air-cooled condensers:

• These are usually made of copper tubing with thin fins assisting rapid radiation.

These are mainly of two types

1. Natural air-cooled condensers:
   • In the natural convection type, heat transfer from the condenser is by buoyancy-induced natural convection and radiation.
2. Forced draft condensers:
   • In forced convection-type condensers, the circulation of air over the condenser surface is maintained by using a fan or a blower.
   • Forced air-cooled condenser fins are made up of Aluminum.

Fin-type forced air-cooled condenser:

• In this type, the fins are provided vertically on a frame.
• The fins are like a thin rod (2 mm diameter) evenly welded in the proper interval to the frame.
• The condenser coils will be clamped and soldered to the fins.
• The frame is fit at the back wall of the fridge, tighten the screws.
• The natural air passes through the fins (distributed) and the condenser coils get cool.
• The pollution of air, the condenser fins will get a coating of fine dust.
• The dust over the condensing tubes will affect the heat transfer efficiency of the condenser.
• That can be cleaned periodically.

Plate-type air-cooled condenser:

• In this type, the condenser tubes are soldered to a metal plate and the plate will be fixed at the back of the fridge- tighten by the corner screws.
• The condensation takes place through natural air ventilation.
• Condenser tubes give up heat to the plate by conductivity and the plate surface is cooled by natural air velocity.
• So always, it is advised to keep a distance minimum of 15 cm from the wall to the fridge backside for free air circulation.
• The condenser tubes are fixed inner side of the plate and if the dust covers the tubes or plates can be cleaned with a weak soap solution to increase the condenser's performance.

A condenser is a heat transferring device to change the gas or vapour discharged by the compressor to liquid to be used in the evaporator.

Types of Condensers

• Air-cooled condensers
• Water-cooled condensers
• Combined air and water condensers
• Evaporative type condensers

Air-cooled condensers:  These are usually made of copper tubing with thin fins assisting rapid radiation. These are mainly of two types

1. Natural air-cooled condensers

 In the natural convection type, heat transfer from the condenser is by buoyancy induced natural convection and radiation.

2. Forced draft condensers

 In forced convection type condensers, the circulation of air over the condenser surface is maintained by using a fan or a blower.

In the natural convection air cooled condensers, large condensing surface area is required as the circulating air quantity is less. This type of condensers is used in domestic refrigerators, deep freezers and other small capacity applications.

Explanation:

• The performance of condenser gets affected badly by presence of air which will remain non condensable.
• It covers the heat transfer surfaces such as outside the surface of condenser tubes and reduces the condensing heat transfer coefficient.
• Clinging of air to surface reduces the condensing coefficient
• air imparts large thermal resistance due to its low thermal conductivity

In the condenser, the heat is mainly dissipated by convection. The heat is taken away either by air or water by convection.

Concept:

Condenser efficiency: The efficiency of a condenser is defined as the ratio of the difference between the outlet and inlet temperatures of cooling water to the difference between the temperature of the steam corresponding to the vacuum in the condenser and inlet temperature of cooling water.

\(\eta = \frac{{{T_{ce}} - {T_{ci}}}}{{{T_s} - {T_{ci}}}}\)

With the increase in the overall heat transfer coefficient the heat transfer rate will increase as the

Q = U × A × ∆Tm

U = overall heat transfer coefficient, A = area, ∆Tm = Logarithmic mean temperature difference

• Therefore the exit temperature of the cold fluid will be more with the increased overall heat transfer coefficient, consequently the efficiency of the condenser will increase.
• Now with the increased velocity of the flow the mass flow rate of the cold fluid will increase which will pick more heat from the steam and again the exit temperature of the cold fluid will be higher which will increase the efficiency of the condenser.

When the temperature difference between the steam entering the condenser and inlet temperature of the cold water is high the efficiency of the condenser will decrease as can be seen from the expression for efficiency.

Efficiency of water-cooled condenser is more than air cooled condenser as the heat transfer coefficient of water is much higher than air. For a fixed heat transfer rate, the size required in water cooled air conditioner is more. But the service and maintenance in water cooled condenser is more due to a greater number of components. That’s why in small capacity applications like domestic refrigerators, air cooled is preferred.

Types of air-cooled condenser: There are two types of air-cooled condensers

1. Plate type: In plate type condenser, the condenser tubes are soldered to a metal plate and the plate is fixed at the back of the fridge tighten by the corner screws.

The condensation takes place by natural air ventilation. Condenser tubes gives up heat to the plate by conductivity and the plate surface is cooled by natural air velocity. So always it is advised to keep minimum distance of 15 cm from the fridge back side for free air circulation.

2. Fin type:

In this type fins are provided vertical on a frame. The fins are like a thin rod evenly welded in proper interval to the frame. The condensers are clamped and soldered to the fins.

The compressor and condenser mounted together is called condensing unit. In refrigeration, low side of the refrigeration system means the metering device and the evaporator. High side means compressor and condenser. 

PUF stands for Poly Urethane Foam. It acts as an insulation material replacing glass wool. It is used in modern fridges having body condenser

Condenser is a heat transferring device used to change the gas or vapour discharged by the compressor to liquid ready for the use in the evaporator.