Heat Exchanger Control

Dear,

i am looking at the control of heat exchangers. I have one set of two heat exchangers.

When i select its control valve that will be serving two heat exchanger, i select it based on the coil of two heat exchangers (worst case)

However, during part load, will this control valve work properly?
Sometimes, we add another control valve in parallel to get a better control (check attached sketch.
or put one control valve for each heat exchanger?

please advice.

charbel

I'm not sure why you have two valves in parallel controlling the supply two both exchangers. It is unlikely that the process flow and temperatures to both exchangers will be identical. I would use one control valve for each heat exhchanger.

yes having a big and a small valve is done a lot in refrigeration
some remarks: have the supply and return exchanged, this way the exchangers will always be full.
if possible put exchangers in series

Dear,

thank you for your answers. Actually, big and small valve is used on the heat exchanger set to take care of the part load conditions i believe. in some case, they put big and small valve on each heat exchanger, which I dont see the purpose, any idea?

I tend to agree with Tom to have for each heat exchanger one control valve on the return ( as mentionned by shooter, in order to have each heat exchanger always full)

thank you!

charbel

We mostly use two valves per exchanger. One for controlling the flow through, and one for controlling the by pass. And they open (inversed) proportionally to each other.

The control valve is mostly situated in the return part of the exchanger when we control the temperature coming out of the exchanger on the primary side. And we place it in the supply part of the exchanger when we control the temperature on the secondary side of the exchanger. Mostly... lol