I am a newbie on refrigeration. I read several documentation to understand how the refrigeration cycle works.
I didn't have the chance to apprentice all the theory in a very deep manner. Therefore I had to concentrate on understanding the basic concepts of the system.
More or less everything is clear to me. I only have a big lack on superheating. In the literature it is told that the superheating measured at the evaporator outlet should be quite low ( usually from 5 to 10 deg Celsius). It is stated that under these conditions, the heat absoprtion efficiency is maximum. In addition I see that when superheating is too low, I risk the flooding while when it is too high, I loss efficiency and I need to blower to speed up to condense the hot vapour.
The concept I can't understand is the following. Why superheating shall be low. In my mind, the higher is the vapour temperature at the outlet and the higher is the amount of heat I have absorbed. What is missing?
Thanks in advance
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Superheat is typically anywhere around 8 to 12 degree F , I do not know off hand what that is in C. For A/C . If your referring to refrigeration, you need to follow the manufacture specification. Also applies to A/C . The manufacture install guide will tell you exactly what they want for Superheat, Subcooling is another form of charging, in A/C systems. You can google superheat " How it works in a refrigeration system " what is superheat? How does low or high superheat affect a system ? you probably can get a better answer via internet.
It takes a relatively small amount of heat to raise the temperature of the vapor an additional degree compared to the amount of heat needed to change the state of refrigerant from liquid to vapor. Therefore, much more work is done by the evaporator when more of it is "flooded" with liquid. The proper amount of superheat is a compromise between more refrigerant - for greater cooling capacity by the evaporator, and less refrigerant - to ensure the evaporator is not fully flooded to the point that no change (or insufficient change) of state occurs in the evaporator. The important result of this also ensures that relatively cool vapor is supplied to the compressor, without liquid being introduced to it.
Thanks both for the very clear explanation . Thus, it's a matter of work done by the evaporator that seems to be higher during the boiling phase. Thinking to the enthalphy diagram, I have enthalphy that increases despite the temperature keeps constant . But enthalphy means work done by the evaporator. Am I right? In addition, do I have to run the blower faster when superheating is high or low? I guess when it' a high because it' more difficult to have the vapour condensed, thanks again
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