Advertisement

Responsive Advertisement

RAC viva question answers

 VCRS Cycle:- Vapour compression refrigeration system.

Q.1 What are the main components of the VCRS cycle?
Ans. There are four components of vcrs cycle -
       1.compressor
       2.condenser
       3.throttling valve
       4.evaporator

Q.2 explain the working of the VCRS cycle.

R-134a is used as a working fluid in VCR which absorb the heat from the refrigerated space and rejects into the surrounding. 

1 step.-  firstly refrigerant compressed in the compressor isentropically, as a result, the pressure and temperature increases. 

2 step- then it passes through the condenser where there is a heat exchanger present by which it rejects the heat, hence the temperature decreases but the pressure remais constant.

3 step- after that it passes through the throttle valve in which the fluid expands as a result pressure and temperature decrease further and the enthalpy of the refrigerant remains constant.

4 step- onwards it passes through the evaporator from where it absorbs the heat from the refrigerated space hence its temperature increases very high.


1. What Will Be The Relative Humidity At Saturation Point?

Answer :

Relative humidity = 100 %


2. Explain The Principle Of Refrigeration?

Answer :

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 an external source.

    3. What Is Air Conditioners?

    Answer :

    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 needs to be cooled.


    4. What Is Wet Bulb Depression?

    Answer :

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


    5. Define Relative Humidity?

    Answer :

    The 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.


    6. What Is Refrigeration?

      Answer :

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


       7. Difference Between The Refrigeration And Heat Pump?

      Answer :

      Refrigerators eject heat with work input. But heat pumps give heat with work input.

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

       8. What Is Sensible Heat Ratio (shr)?

      Answer :

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

        9. How Much Resistance Is Offered To Heat Flow By Dropwise Condensation?

        Answer :

        Nill.

         10. Why Rate Of Condensation Is Higher On A Polished Surface Compared To Rusty Surface?

        Answer :

        A polished surface promotes drop-wise condensation and does not wet the surface.

           11. What Is Mechanical Refrigeration?

          Answer :

          Producing cold by machine.


          12. Classify The Different Refrigeration Systems?

          Answer :

          It may be of the following three types:

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

          13. What Are The Basic Units Of Mechanical Refrigeration Systems?

          Answer :

          The refrigeration system has 4 basic units

          An Evaporator – The cooling Unit
          A pump or Compressor
          A Condenser – The heat disposer
          A liquid mixing device – Expansion valve or cylinder or capillary tube


          Answer :The evaporator

            Answer :

            As the 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 ”


             16. What Is One Tonne Of Refrigeration?

            Answer :

            One Tonne of Refrigeration means a 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.

               17. What  Is The Capacity Of One Tonne Machine In Mks System?

              Answer :

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


               18. Define Co-efficient Of Performance?

              Answer :In the case of the engine, the performance is judged by the efficiency of the engine. That is – Efficiency = Work Done / Heat Supplied. And in the case of refrigeration, the process is first reversed that is we have to supply work to obtain a lower temperature or say for the removal of heat. Thus the performance of refrigeration is just reversed. That is – N/W

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

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


              Question 19. What Is Relative Cop?

              Answer :

              It is the ratio of actual COP and Theoretical COP

              Post a Comment

              0 Comments