low ambient condenser operation
Hello,
Hope I can get some help with this concept I am struggling with.
What happens to the refrigeration cycle at extremely low ambient temperatures. If there is nothing to regulate the system, wouldn't the fluid exit the condenser at an extremely low temperature? And if that were to happen, the refrigeration cycle would not be possible.
Is there always, without stating it, a system in place (such as an ORI/ORD) that regulates the fluid at the condensor exit (or, more pertinently, expansion valve inlet)? Can I correctly assume this to be the case if I know that the condensor is experiencing free cooling.
Would the condenser type have an affect on this? Air-cooled vs evap condenser for example?
In other words, if someone claims that there commercial refrigeration system operates at a COP of 3.5 for the whole year (give or take negligible variations), and the system involves free cooling of the condensor, should I accept it?
Thank you!
Re: low ambient condenser operation
Quote:
Originally Posted by
mk2coupe85
Hello,
Hope I can get some help with this concept I am struggling with.
What happens to the refrigeration cycle at extremely low ambient temperatures. If there is nothing to regulate the system, wouldn't the fluid exit the condenser at an extremely low temperature? And if that were to happen, the refrigeration cycle would not be possible.
Is there always, without stating it, a system in place (such as an ORI/ORD) that regulates the fluid at the condensor exit (or, more pertinently, expansion valve inlet)? Can I correctly assume this to be the case if I know that the condensor is experiencing free cooling.
Would the condenser type have an affect on this? Air-cooled vs evap condenser for example?
In other words, if someone claims that there commercial refrigeration system operates at a COP of 3.5 for the whole year (give or take negligible variations), and the system involves free cooling of the condensor, should I accept it?
Thank you!
What tends to happen is the condensing temperature drops to a point
where the pressure of the liquid in the liquid pipe is not high enough
for it to force the expansion valve open fully. This then leads to liquid logging
inside the condenser / receiver and the evap becomes a bit starved of refrigerant.
It can be controlled by regulating the speed of the cond fan/s and adding
valves that keep the pressure up in low ambients, but it is a common fault
with basic systems.
Regards
Rob
.
Re: low ambient condenser operation
All of Rob's is correct: but there can be more to it. In a compact system with a fair extent of compressor tolerance and no concerns about oil return or evaporator performance, its exactly what will happen, TXV or Cap Tube or what have you. In the worst cases the evaporating pressure can drop so far that a coil that is just meant for AC will frost and plug up, for instance. But in an expansive system, with oil separators, multiple compressor oil return arrangements, split condenser coils, TXV's with conventional charges trying to pass liquid colder than the Evap Temp and so on: a steady discharge pressure and some operating envelope in terms of the HP liquid temperature, are more like requirements.
Throw heat recovery arrangements on top of all that and it can really get involved.
