Heat exchanger duty in upset case

[ChemEngSquirrel]

I have a heat exchanger with a PSV on the cold side. My scenario is control valve failure on the hot side sending more hot fluid via the exchanger than is quoted on the data sheet.

Is there a simple way for me to estimate worst case heat transfer rate to the cold side for this scenario?

Thanks.

 

[EmmanuelTop]

There are two ways I can think of:

1) Use heat exchanger software (e.g. HTRI or Aspen EDR), option "rating" for the exchanger with known geometry and fluid properties/flowrates. The software will estimate outlet temperatures for both fluids and hence the new duty point.

2) Calculate how much the overall heat transfer coefficient increases (as compared to the base case) when one side of the exchanger sees higher flow. Although the LMTD will also change in this case, the increase of the overall U should give you some estimation - a figure at least being in the same order of magnitude as the real one.

Dejan IVANOVIC
Process Engineer, MSChE

 

[gaswell]

20:22 -> 20:31 nine minutes to read the post, think about and give a detailed answer...
that' really amazing !

 

[EmmanuelTop]

I've been good with quiz and puzzles since my earliest childhood.

Dejan IVANOVIC
Process Engineer, MSChE

 

[gocougs1]

When estimating the exchanger duty be aware, at least in the refinery world, that design exchanger duty uses the DIRTY service U factor. For PSV sizing the clean U must be calculated and used.

I've never seen an abnormal heat input case for an exchanger like you are describing... usually we only consider isolation of the cold side with continued heat input, which we would do a PRO/II rigorous exchanger model to estimate duty.