Top 19 Air Conditioning And Refrigeration Interview Questions You Must Prepare 24.May.2024

Wet bulb depression is the difference between dry bulb temperature and wet bulb temperature.

Polished surface promotes drop wise condensation and does not wet the surface.

In case of engine the performance is judged the efficiency of the engine. That is – Efficiency = Work Done / Heat Supplied .

And in case of refrigeration the process is first reversed that is we have to supply work to obtain lower temperature  or say for that removal of heat. Thus performance of refrigeration is just reversed . That is – N/W

Where – N = The rate of heat abstracted from the body in given time technically called “Net Refrigeration Effect” and W = Work Done .

Thus COP = Net Refrigeration Effect / Work Done Supplied . This is Called Theoretical COP .

Air Conditioner continuously draws the air from the space to be cooled & cools it by the principle of refrigeration and discharge it back to the same indoor space that need to be cooled.

Refrigeration is the process of continuously cooling or extraction of heat from the atmosphere or surroundings with the help of external work.

In MKS system a machine having capacity to produce cooling effect of 50 kcal/minute is known to be a “One Tonne Machine”

Producing cold by machine.

It may be of the following three types:

  1. Vapor Compression Refrigeration System
  2. Vapor absorption Refrigeration System 
  3. Air Refrigeration Systems

One Tonne of Refrigeration me machine is capable of removing heat from a body equal to the heat absorbed by one tonne of ice when it melts from 0 ° C to 0 ° C Water in 24 hours . Here one tonne is equal to 2000 lb .

Refrigerators ejects heat with work input. But heat pumps gives heat with work input.

Refrigerator contains the heat pump, it pumps the heat out so that your system remains cold.

The operation is according to the second law of thermodynamics - Heat can be made to flow from cold body to hot body with the help of external source.

Relative humidity is the ratio between the actual moisture content of the air compared with the moisture content of the air required for saturation at the same temperature.

The Sensible Heat Ratio (SHR) express the ratio between the sensible heat load and the total heat load.

Refrigeration system has 4 basic units

  1. An Evaporator – The cooling Unit
  2. A pump or Compressor
  3. A Condenser – The heat disposer
  4. A liquid mixing device – Expion valve or cylinder or capillary tube

It is the ratio of actual COP and Theoretical COP

As Power Unit of mechanical devices is given by H.P , for electrical equipment the unit of power is kW or MW . In the same way the unit of refrigeration is  ” Tonnes of Refrigeration ”