Printable View
The capacity of Evaporators are available for R 22. I have to use the Evaporators for a system with R 134a. What is the factor by which I shall be able attain the capacity with R 134a of an Evaporator suitable for R 22. Or the size of the Coil remain the same irrespective of the refrigerant.
Can you give an example. I probably have the resource right here, I just don't know exactly what I am looking for.
I have looked through several US manufacturers catalogs and they do not make an adjustment for the unit cooler capacity. They simply specifiy the capacity at a fixed TD.
My guess is they do not adjust the capacity for the refrigerant, only the TXV and nozzle size for the distributor.
Therefore, it appears if the catalog states "X" capacity @ "Y" TD, this is considered the same for any refrigerant. Only the TXV and nozzle are selected for a specific refrigerant at that stated capacity.
From one viewpoint, the air side of the heat exchanger "controls" the overall heat transfer rate(and capacity).
This is the best idea I can find or provide.
Lana would have an immediate answer for this I suppose!.;)
Most do not derate new DX evaps for R134a. What you do need to watch is the distributor. It may or may not be right on R134. More vapor is generated and the distributor must be sized accordingly. The orifice is going to be wrong as will the TXV used on R-22.
Ken
Ken
US Iceman and TXiceman are correct. The US manufacturers change the orifice of the distributor. But I was going through the Guntner Catalogs, where in they have mentioned derating factors for different refrigerants from 404.
Hi everybody,
The evaporator surface area which is OK for R22 will be fine for R134a. But as others mentioned the distributor must be checked for operating conditions.
TEV is a different matter and for sure must be checked and changed as appropriate.
The major concern is the oil in the tubes. If the evaporator is used for R22 with mineral oils then if the refrigerant is changed to R134a then a careful cleaning is required in order to ensure that no mineral oil is remained in the tubes.
If synthetic oil is mixed with mineral one and R134a then high pressure gas is created with acid which will destroy the compressor.
Cheers
It is a new installation and as such changing oil is not there. The reason for my question was that I have to select the Evaporator. The ones that I used are generally of Heatcraft, USA. In their catalogs they have not specified separately for 134a.
Anyway I have spoken to them and they have clarified that only the distributo orifice shall be changed.
This thread was post long time ago, but still I have the similar question.
As the heat transfer characteristic of R134a are poorer than R22, the capacity will be smaller. So there will be difference in capacity, namely if we wanna maintain the capacity, we need to enlarge the heat exchanger(both the evaporator and condenser), is that right?