By pass valve

[redif]

Hi,

We have designed a fresh water cooled condenser for a refrigeration plant at 37 degC inlet water temperature. But later it is found that the inlet fresh water temperature is not stable. In winter it may go below to 5 degC. My question is "will the compressor/condensor unit will function properly without providing any bypass valve for recirculation"?

Thanks

 

[Drazen]

I must answer with question: what kind of load control you actually use for your condenser? You must have some system for load balancing because you need to have condenser outlet temperature contolled.

 

[TXiceman]

More than likely, you will need to add a condenser water regulating valve (WRV) in order to keep the head pressure up to a specificied minimum. In order for the refrigerant to feed properly from the high pressure side to the low pressure side, you will have a minmum discharge pressure or head pressure. Contact the chiller manufacturer for the minimum discharge pressure on your unit.

If you want to tacle this on your own, look at Johnson Controls or Metrix fro water regulating valves. These are self contained pressure operated (condenser pressure) valves.

Ken

TXiceman

http://www.rae-corp.com

 

[SAK9]

It wont work mate.The compressor will trip on low suction pressure as the regrigerant head pressure in the condenser would drop substantially with low water temperatures.
You do need a tower bypass control which would raise the water temperature to an acceptable level.

 

[TXiceman]

SAK9. the common way around the start up issue is to use a timed starting bypass on the low pressure switch to allow the unit some time to build up pressure. Also use a pressure regulator and check to pressurize the receiver...

Ken

TXiceman

http://www.rae-corp.com

 

[tombmech]

"Plant" seemed to be the operative word. Large systems have been known to draw water directly from a pond, lake, or river source. In those cases, a bypass is the only way to reliably control the water temperature. Some chillers are very sensitive to condenser water temps, and there is little chance that a 2-way throttling valve or pressure regulator can keep the chillers online. There simply isn't enough mass flow rate of the water at the reduced temperatures to keep the safeties from tripping.

Heating the water is not possible, either - unless you "punt" and put in cooling towers - the water source is an infinite heat sink. Any fresh water system would have ample filtration and bypass capability built-in, though. I would think it a simple matter to modify some of that to make a bypass loop somewhere in the system. That would provide some degree of tempering by mixing the water streams.

It's all conjecture unless Redif gives us more detail, though. Strategies differ depending on the size of the system.