Position of the evaporator Vs performance

[MobileHVAC]

Due to the space restriction and the position of the air condition box in the vehicle, I have no choice but position the evaporator horizontally.
(Typically, in all automotive vehicles position the evaporator vertically- tank at the top or bottom that will allow the air to pass through the evaporator side ways –
on the other hand, horizontal position, the air will pass from the bottom upward.. I hope it is clear)
The evaporator tested vertically and horizontally with the same conditions:

Here's a very brief summary of the findings:

- No instability was observed at 150 or 250 cfm @ 90 degree position.(vertically)

- Instability was observed at 150 and 250 cfm @ 0 degree position (horizontally)suction pressure was all over the map from 10 PSI to 40 PSI..

- The 0 degree horizontal position had 1000 BTU/hr lower performance than the 90 degree vertical position.
The questions are:
Why I experienced instability at 0 degree horizontal position?
Is it common to loss performance by set the plate and fin evaporator horizontally?

Test details:
Refrigerant Inlet temperature 120F
Superheat 8-12F
Suction pressure 25PSI
TXV pressure (head) 200 PSI

Air inlet temp. 90F
Relative humidity 50%
Air flow 250

 

[twainagain]

Is this a TXV system? Some TXV are finicky about orientation.

 

[pennpoint]

MobileHVAC
In a properly sized evaporator not all of the liquid refrigerant is vapor/gas until the last row of tubes (facing the entering air).
Simply changing the orientation of the coilng without changing or looking at the tube circuiting can result in logging liquid refrigerant and/or oil in return bends.

This may account for the erratic behavour of the system.

Good Luck
Pennpoint

 

[MobileHVAC]

Twainagain,
It is TXV system and I am using (PARKER/EATON)block valve type. As per Eaton specifications this type of block valve TXV can be positioned on 0 or 90 degree +-15deg.

Pennpoint:
The evaporator is plate and fin type (not tube and fin)
It is a six pass core with 7-9-11 circuit, which the last 2 passes has a 4-4-3 circuit separated by flow distribution shims. The instability in the evaporator can be detected almost immediately that lead me to believe no oil build up in the evaporator. Furthermore, the instability is repeatable… However, the thermo-imaging pictures show hot spot at center of the evaporator
Yet to find out WHY!?
Thanks for your input