RU as heat pump with 2 condensers

[kgiger]

Hello

I'd like to use a screw compressor refrigeration unit as a heat pump. So, the evaporator will be used for cooling some process fluid. The system will have two condensers. One will be used to heat up some process fluid and the other one will be cooled by cooling water to remove the excess heat that cannot be removed by the first condenser.
How are the two condensers best arranged, in series or parallel?
In my understanding the condensation pressure will be the same in both condensers (please correct me if I'm wrong). The process fluid to be heated up will have a lower inlet temperature than the cooling water. Which medium (process fluid or cooling water) will dictate the condensation temperature/pressure?
The goal is to keep the condensation pressure as low as possible and discharge as much heat as possible via the process fluid. However, the process fluid stream will not be sufficient and, thus, cooling water which has a higher inlet temperature will also have to be used.

Thanks in advance for any help.
K. Giger

[nike123]

I would connect 2 BPHE in series and cooling water BPHE as second one. I would put water regulating valve (guided by pressure in condensers) at water outlet of cooling water BPHE.
Dimension both BPHE for full load.

Why should condensing pressure should be "as low as possible"?
I would set it as optimal as possible.

[kgiger]

I would connect 2 BPHE in series and cooling water BPHE as second one. I would put water regulating valve (guided by pressure in condensers) at water outlet of cooling water BPHE.
Dimension both BPHE for full load.

Why should condensing pressure should be "as low as possible"?
I would set it as optimal as possible.
Because the temperature of the process fluid is lower than the temperature of the cooling water. The idea is to keep the condensation pressure lower in order to get a better COP. That's also why I asked about the resulting condensation pressure in case of a two condenser system: Is it dicated by the cooling water inlet temperature or the process fluid temperature? How to calculate the condensation pressure in such a case?
What do you mean by optimal? Optimal with respect to what?
My goal is to reduce the COP, if possible. If you have any good ideas, I'd be happy to hear them.

Thanks for you help.

Regards
K. Giger

[nike123]

Because the temperature of the process fluid is lower than the temperature of the cooling water. The idea is to keep the condensation pressure lower in order to get a better COP. That's also why I asked about the resulting condensation pressure in case of a two condenser system: Is it dicated by the cooling water inlet temperature or the process fluid temperature?

It is dictated first by process fluid temperature and its flow. If that flow is inadequate to keep condensation pressure low enough that additional condenser is not necessary, than water regulating valve will open and let cooling water in amount necessary to keep condensation pressure as adjusted at water regulating valve.


How to calculate the condensation pressure in such a case?

No need for calculation. It will be as adjusted at water regulating valve or lower if you have too much cooling at process fluid HE.



What do you mean by optimal? Optimal with respect to what?
My goal is to reduce the COP, if possible. If you have any good ideas, I'd be happy to hear them.

http://www.refrigeration-engineer.com/forums/showthread.php?t=18910