Dear stress community,

I need some help for following problem.

I have to calculate a pipeline with liquid medium between a pump and an fast closing valve (simplified model), also a waterhammer calculation.

In the pipeline 4 heat exchangers are built in, to heat up the liquid.

To estimate the influence of the closing time I need to calculate the time of reflection in the pipeline. My question: what is the point where the travelling pressure wave will be reflected?

Have I to use the length between valve and heat exchangers
or
have I to take the assumption, that the pressure wave goes “through” the heat exchangers until to the pump and then back to the valve.

To solve my problem, I would like to get suggestions from “shock wave calculation” experienced engineers.

Thanks in advance …

Herr Ortel,

During a transient flow the waves goes through the heat exchanger.

If you are using the characteristics method for water hammer calculation, depending on the type of heat exchanger, it can be replaced by an equivalent pipe having a crosssectional equivalent area and the head loss in the equivalent pipe is assumed equal to the head loss in the heat exchanger.

Commercial water hammer software includes heat exchanger modelation.

Regards,

R. Kühn

Dear Mr. Oertel,

I think R. Kühn is right - the pressure wave will propagate through the equipment. But the diameter/wallthickness ratio as well as the equipment material will affect the wave propagating velocity. Also, if the fluid changes its temperature there will be a different density, which also might have an effect on the wpv.

If you are interested also in time-history forces: We are using Flowmaster2 to calculate those forces for later usage in our pipe stress sofware. Feeel free to contact me if you need further help.

All the best,

Veit Bockemühl
vb@esn-gmbh.com
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