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Lmtd For Steam Heated Exchangers

heat exchanger design

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#1 A.BHANU

A.BHANU

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Posted 02 March 2017 - 08:12 AM

I have to design 02 HX for heating methyl chloride and chlorine vapor  upto 100C from 50 C. Both inlet and outlets are in vapor form. Heating medium is saturated steam. Should we use LMTD for both the cases ? I doubt coz heating media (steam) temp is same throughout the inlet and outlet.

 

Normally what pressure steam is used for such purpose? and associated temp ?

Would be helpful if anyone can provide specific heat of vapor for chlorine and methyl chloride.

How to calculate the pressure increase in HX. The inlet pressure is 10 bar in both cases and streams are fed to a reactor.

 

 

 



#2 Pilesar

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Posted 02 March 2017 - 10:53 AM

Use the steam the plant has available. A low pressure utility steam should be okay for this service. You will need to determine the available steam pressure and temperature before you begin the exchanger design. The steam to the exchanger will generally pass through a control valve to a lower pressure inside the exchanger. Pick a conservatively low steam pressure for thermal equipment design if you have no other information. Perhaps 20 psig or so. Look up the saturated temperature for the pressure you choose in the steam tables. Choose a conservatively higher steam pressure for mechanical design of the equipment. Steam temperature can be assumed to be essentially constant at a higher temperature than the process side inlet and outlet. You can calculate a 'mean temperature difference' arithmetically without using the 'log' function if you find it useful. 

   Specific heats for your components should be readily found in standard references.

   Pressure will not increase in your heat exchanger. Fluid flows from higher pressure to lower pressure unless there is some external mechanical force (such as a pump or compressor) acting on it.



#3 srfish

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Posted 02 March 2017 - 11:32 AM

For the specific heats of Chlorine and Methyl Chlorine vapor,  try http://webbook.nist....chemistry/fluid or www.prode.com






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