Whenever i have studied refrigeration cycle on books, i have found that the diagrams are always explained starting from the compressor*, then condenser then throttle and finally evaporator. I find it strange to start from the compressor, since the heat from the food items inside the refrigerator compartment must be absorbed first, then the compressor does work on it, which increases its pressure and temperature(which makes the refrigerant temp greater than the ambient, and thus we are able to reject the heat). Am i right to think this way? What is the actual sequence of operations in a refrigerator.

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    $\begingroup$ It's a cycle so it goes in a loop. What you choose as the starting point is an arbitrary decision since with a loop you can start anywhere. $\endgroup$ – John Rennie Jun 18 '18 at 7:07
  • $\begingroup$ Yes that is true, but say when the refrigerator is operated for the very first time, where would the cycle start from. Is this decision arbitrary or does the refrigerant in actual operation always start from the compressor. $\endgroup$ – Mohammad Nayef Jun 18 '18 at 8:28

It is correct that all the refrigeration cycle diagrams begin with the compression process. I'm no refrigeration/AC expert but let me take a stab at the reason. Let's use the example of a room A/C. Let's say the A/C has not been running for a while. As such the refrigerant sitting in the condenser is essentially at the same temperature as the outdoor air temperature and the refrigerant in the evaporator is essentially the same as the air temperature of the room. Given these conditions you cannot have heat transfer to the evaporator or from the condenser when the A/C first turns on. That leaves it necessary to start the cycle with the compression process to create the necessary temperature and pressure differentials for heat transfers to take place. If someone has other thoughts I’d like to hear them.

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  • $\begingroup$ Quite a good explanation, it may well be the reason. $\endgroup$ – Mohammad Nayef Jul 10 '18 at 15:52

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