Heat Exchanger Request for co-current UA reporting

[HenkF]

Hi Jasper,
An additional request... I noticed that the heat-exchanger model calculates a heat transfer coefficient when in counter-current calculation mode.
For co-current flows it doesn't do. I can't think of a reason why it shouldn't be able to also calculate one. Would it be possible to add this as well?

regards, Henk

[jasper]

What exactly is the specification of the heat exchanger? Which type? Which mode?

[HenkF]

In Temperature mode Heat Transfer (W/K) seems to be calculated/reported for the counter-current case, but not for co-current. In many cases design (m2 HX surface), temperature and flow data for heat-exchanging equipment are available, and the exchanged heat can be calculated (as the HeatExchanger model does). When an overall heat-transfer coefficient is available, the influence of fouling of the HX tubes can be calculated.
regards, Henk

[jasper]

I am not clear on that. In temperature mode (temperature specified), there is no need to specify co- or counter current and the heat exchanger simply runs a heat balance. Indeed UA is reported for counter-current operation.

Do I understand you want the ability to switch to co-current mode? This will only affect the reported UA.

[HenkF]

I would appreciate the implementation.

The differences showed when an Excel report was made:

Excel HX report.jpg (64.74 KiB) Viewed 25128 times

[jasper]

There are more consequences. Currently, for the T-specified heat exchanger the amount of heat transferred is limited such that T[in,hot] >= T[out,1] >= T[in, cold as well as T[in,hot] >= T[out,2] >= T[in, cold] where T[out,1] is only the specified temperature in case this condition is not violated. For a co-current heat exchanger, this condition changes so that T[out, hot] >= T[out, cold], so the limiting case would be different. More-over, this limiting case requires a 1 dimensional solver to be found (but it only has to be solved for in case the condition is violated at the specified temperature).

It would be somewhat strange to do so for the T specified heat exchanger, but not for the Q specified heat exchanger. This one is limited for counter-current operation such that Q <= max( Q[hot]@T[in,hot] - Q[hot]@T[in,cold], Q[cold]@T[in,hot] - Q[cold]@T[in,cold] ), equivalent to to the temperature limits above. A similar change would apply in case of co-current operation.

[HenkF]

Thanks for your explanation. I see the consequences as you describe it.
Anyway, I'll try to set up a solution using Excel. If this works out, I'll share this with you.
regards,
Henk

[jasper]

I will make the change, it is in the pipe line. It will just take a bit as I have more pressing stuff on my desk at this moment.

I will try to get to it before the weekend.

[jasper]

Please check that all works as expected? (CUP).

[HenkF]