Heat recovery

[Pykester1]

Can anyone help?
I am looking to recover some heat from a large 3 compressor pack by pumping water through a plate heat exchanger fitted inline on the discharge line to the remote condenser and using the warmed up water to suppliment the factory's hot water system.
If anyone has any useful info regarding this matter I would be very grateful. I have seen systems like this fitted on different sites before, but have never had to install one. Thanks.

[icecube51]

be careful whit redrawing heat from the compressor(s).if you try to take some heat from the HP line it is possible the condenser will not work properly. if you take heat from the cooling water or compressor itself you will benefit in both ways. the oil in the compressor be cooler,the compression will be higher and so on and on . be careful by changing anything on the line's itself.

Ice

[US Iceman]

Desuperheating refrigerant vapor for heat recovery sounds nice and it can provide some heat. However, if the refrigerant vapor has the potential to condense in the desuperheater you can have some problems.

Most of the desuperheaters I have seen (and their associated refrigerant piping) can provide a way for the condensed vapor to collect in the heat exchanger. If this happens then you loose all heat generation capacity for recovery. This is similar to an air-cooled condenser with head pressure controls that flood the condenser with liquid. It reduced the condenser capacity.

You have to make sure the liquid refrigerant can drain by gravity to achieve 100% of the rated heat recovery potential.

[Pykester1]

Hello US Iceman, thanks for the advice, that makes a lot of sense. So in theory if I install the heat exchanger higher than condenser the condensed vapour should drain into the condenser?
If so, how does one select the correctly sized heat exchanger? I realize that it does not have to be exact, but I wouldn't want to install a heat exchanger that did nothing at all.
Also I wouldn't want to install a heat exchanger that was so oversized that it over condensed the refrigerant.
Any help would be gratefully received.
Cheers.
Simon Pyke. UK.

[US Iceman]

Hi Simon.

The heat recovery exchanger needs to have connections that allow the condensed vapor to drain. I have seen some exchangers which even though single pass on the refrigerant side, they allow the liquid to accumulate.

The trick is to drain any liquid while allowing the gas to also flow into the condenser.

I think most of the desuperheater sizing is based on only sensible heat transfer, not latent where condensing occurs.

You might have to ask the manufacturer and see what he/she says about this, but I think it is all sensible myself.

[Andy]

Hello US Iceman, thanks for the advice, that makes a lot of sense. So in theory if I install the heat exchanger higher than condenser the condensed vapour should drain into the condenser?
If so, how does one select the correctly sized heat exchanger? I realize that it does not have to be exact, but I wouldn't want to install a heat exchanger that did nothing at all.
Also I wouldn't want to install a heat exchanger that was so oversized that it over condensed the refrigerant.
Any help would be gratefully received.
Cheers.
Simon Pyke. UK.

Hi Pykester1

you could size the heat exchanger to 25% of your normal winter THR.

Kind Regards Andy D

[wilsoncheung]

I think a shell and tube heat exchanger can drain the liquid refrigerant quit well coz the refrigerant is in the shell side and we can put it above condenser.

[sterl]

Your condenser outdoors? Your climate such that freezing water with O/D install of concern? Note also: if you employ liquid side regulators for head pressure control, in the cooler season, the air cooled condenser shuts off with liquid refrigerant in it. Depending on Check Valves and etc: This can actually freeze the water in the tubes of an S & T HR even if the S & T is indoors....Regulators need to be on the Discharge Line.