3 replies to this topic

[kadam]

Hello everybody!

 

My task is to find out the flow quantity in a heat exhanger on the cold side. We would like to cool a 95°C water with 25°C water.

We have a DN 800 pipe with 4000 t/h water flow and 4 bar pressure. There is a branch with DN 65 pipe across a heat exchanger and we connect a 2 bar system on the end of the pipe.

The force which allows the fluid to move is the pressure difference.

 

Is it right if I have a given pressure difference and a pipe diameter it determine the flow quantity? Not depends on the flow and velocity in the big pipe?

 

Thanks for your help

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[srfish]

The configuration of the heat exchanger cannot be ignored in calculating the tube-side flow quantity. It may be that it would have a large number of tube passes that would use a large portion of the available pressure difference.

[yazdanpanahimehrdad]

Dear  Kadamı

in detemining accurate flow through this heat exchanger the following items are effective:

1- piping isometric including elevation of pipes( 4barg and 2 barg) and heat exchanger, number of bends and valves and lengthes of the pipes before and after exchanger

2- exchanger geometry for calculating pressure drop 

[aroon]

All above mentioned things may be too complicated ......................
 
You may go with the option of measuring inlet outlet temperatures by using temperature gauges if available (or by using thermo-hunter). By seeing at your statement, you are exchanging only sensible heat. So if process side flow rate is available then it is very easy task
 
mass flow rate for cooling = (m*(Ti-To))_{process side} /(To-Ti)_{cooling side} ....... assuming constant C_p due to both side water.

 

Hope this may be useful for you!