Case of Chocolate biscuits to whoever can help me!!

[nike123]

@joe-ice
Signatures in our posts does not have anything with actual posts. It represent our global attitude. I am sure that Peter_1 as teacher (and moderator here ), has some good reasoning for showing that statement as his signature.


To the subect:

Circuit 1

Te=-5,6°C (air in 16,9°C air out 14,6°C)
Tc=46,5°C (air in 36°C air oit 43,3°C)
Tsh=14,2K
Evaporator:
TD=22,5K
dt=2,3K (not much heat collected)
Approach=20,2K (starving)

Condenser:
TD=10,5K
dt=7,3K
Approach=3,2K (not much heat to reject)

Circuit 2

Te=-10,5°C (air in 11,1°C air out 6,9°C)
Tc=54,8°C (air in 27,2°C air out 39,3°C)
Tsh=14,9K
Evaporator:
TD=21,5K
dt=4,2K
Approach=17,3K

Condenser:
TD=27,6K
dt=12,1K
Approach=15,5 K

Approach of condenser in circuit 2 is too high (15,5K) and approach of evaporator is also to high (17,3K).

Something is probably wrong with that refrigerant inside that unit, or vacuum is not sufficient (or not done at all) prior to refrigerant charging and possible noncondensables are occupying condenser volume or unit is heavily overcharged (my bet is here) with filter dryer dirty or some other obstruction in liquid line region.


Superheat in both circuits is similar (around 15K), but without knowing for real subcooling before TXV, I cannot make any further judgment.

Condenser issues in both circuits should be examined before further evaluation.

Based on given numbers, to me, circuit 1 is working with better numbers but with starving evaporator and recirculating condenser air than circuit 2 with less starving evaporator but with condenser which cannot reject heat efficiently.

Also, as compressor is R404A model, possibly is that TXV is also R404A model and somebody has decided just to switch refrigerant without changing TXV. We need to clarify that also.

Is this new equipment just installed or used one from some other project and someone has decided to use it with R134a instead of R404A?

We need more background of these units since:

The average heat transfer coefficient of R404A is estimated to be 26 to 30% higher than that of R134a for the same saturation temperature.

http://www.tandfonline.com/doi/abs/1...0#.Ug81iIKHqxQ

If equipment is designed to work with R404A, than with use of R134A instead of it, you have 30% less capacity then designed, just by using wrong refrigerant. Therefore, you should provide here all equipment specifications and data to troubleshoot that.