refrigeration evaporator performance

[buster]

My work involves an environmental test chamber (hot, cold & humidity, the issue I have is during cold tests (-20°F or so) the evaporators frost up from traffic into and out of the chamber (reducing performance of the refrigeration system). Looking for information on evaporator de-rating as ice is accumulated and sucessful stratigies to combat or reduce ice formation on evaporators. [sig][/sig]

 

[JohnVA]

As you can see there is NO standard for this problem. The installation simply gets more defrosts as the facility dictates. Russell Coil in Brea Calif actually designed an infrared system to detect when a demand defrost was needed and performed one. Thus allowing the system to perform better with no loss of product, production, and garnered energy savings.

 

[negotiator]

The ever-reoccuring frost-up. You find a resolution for that and you will be decorated with three bronze stars. I took care of the sweating of toilet tanks one year by plumbing HOT water in the tank. Cold water initiated condensation, so.......
This was a two-fold accomplishment; no more wet carpet and
heat-transfer into the bathroom. A small fan gave passive
circulation as well as the evacuation fan.
SO, what system is it ? Is the evapp isolated ? What heating cycle/element does it have on it ? I need more parametric info........
thestocksguy@hotmail.com

 

[Fayaz]

Buster,
Do you have more details on the design? What is your CFM? Type of refrigerant? Low temp. fluid?
What is the capacity of your de-humidifer?
You need to control the grain level (mechanical humidification and dehumidification). I did work on a wind tunnel with 50 deg. C to -40 deg. C.
If the frosting is due to the trafic (in and out) try for conditioned air curtins.

Fayaz

 

[la45]

Hello friend. I have just signed.
The problem you have mantioned of accum. of frost on coils lowering overall performance , I had a similar problem on a chamber (Lab-line Envornmental chamber 708a-2dhx.in which I found pockets around cooling coil by-passing circulating air . Which when tackled properly maintained temp. and humidity to the set points. Checking defrosting timer might help further.
Regards. Alley. Karachi Pakistan.