Could anyone give me an idea on the minimum velocity with which 'normal' evporators are designed?
I am confronted with the same problem on at least 10 identical installations.
The evaporators consists of a distribotor with several circuits of copper tube (5/8") in a bath of etheleen glycol. This bath kept at approx. 0°C) is a kind of buffer for a second copper coil in which a fluidum runs that has to be cooled down to +2°C.
This works. Their is no problem with the final result, but in several cases I had compressors broken down with no oil left in them. My guess is the oil is in the evaporator 'coil'. Until now I wasn't able to physicaly check the pressence of the oil in the evaporator (the units are a few thousand miles from here). But I would like to check theoretically if their is something wrong with the design of the evaporators. To me they seem too big and the internal velocities are too low. That is why I am looking for general rules on the design of an evaporator (minimum velocity for oil return, maximum slope, ...).