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How Do You Analyze Your Heat Exchanger Performance?

I have more than 10 plate heat exchangers (PHE) in my plant. Usually, we'll monitor the flowrate, inlet and outlet temperature, as well as pressure. Before, I joined the company, I observed that the "cleaning in place" (CIP) using caustic solution was carried out when the PHE could no longer produced desired flow rate and temperature outlet. This is one method of eliminating the fouling and scaling on the plate surface in order to improve the heat transfer. If CIP does not work, we have to dismantle the PHE, clean the plates in hot caustic and attach new gasket on it. This will be a far more expensive option and take longer time.

To avoid massive fouling and scaling from getting worse, we have to conduct CIP regularly. When is the right time to perform CIP? As mentioned above, when the flow rate is low or desired outlet temperature could not be achieved, we shall consider doing CIP.

However, I came out with a formula to calculate the "Overall Heat Transfer Coefficient" (U-value) of the heat exchanger. The U-value will give me some indication on which heat exchanger is providing the worse heat transfer. By simplifying the formula in excel file, I can easily know which heat exchanger needs attention just by inserting the inlet/outlet temperature, mass flow rate, heat capacity of oil, and surface area of the plates. The LMTD (log mean temperature difference) will be obtained from the formula and further applied to get the U-value.

I use and manipulated the following formulas:

Q = mc(theta) = UA(LMTD)

Can you work out the formula?

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posted by Kipas Repair JB @ 12:05 AM,


At Tuesday, June 12, 2007, Blogger Webworm said...

You may need to evaluate the source(s) of fouling / scaling by checking any inlet filter / strainer...

At Tuesday, June 12, 2007, Blogger maer wan said...

Zaki bro, nice work on manipulating the formula. However, just wondering, about the value of 'c', which value did u use, Cp (p as subscript), or Cv (v as subscript)?

Cp as in the specific heat, or
Cv as in calorifical value?

or is it the Cp/Cv ratio? because, if i'm not mistaken, there is a factor played by the physical state of the matter (or chemical species), eg. vapor, liquid, etc..

hehe, saja je tanya.. harap2 dapat tunjukajar chem eng berjaya.. ;)

At Tuesday, June 12, 2007, Anonymous Anonymous said...


The fouling and scaling is from the tiny soluble impurities contained in the flowing oil. The filter will only block bigger objects such as plastics, pieces of cloth etc....

Maer Wan,

C is actually Cp (heat capacity) of the oil. No prob, this is a place we can discuss technical stuff and experience....he he

At Wednesday, June 13, 2007, Blogger maer wan said...

thanks, dude

u r one of the good guy..

by the way, banjir kat KL teruk lagi ke? dah jadi ala2 Venice sempena hari 'diaorg' nikah arituh ke? :)

At Wednesday, June 13, 2007, Blogger Webworm said...

Just wanna to...

Cp specific heat capacity at constant PRESSURE

Cv is specific heat capacity at constant VOLUME

If your upstream filter/ strainer somehow failed, particle will go into you HX and will significantly increase the fouling within a short period...so constant checking on the upstream filter/strainer is good operation practice...

At Wednesday, June 13, 2007, Anonymous Anonymous said...

Maer wan,

Boleh le tahan teruk dia...tapi tak sebrutal di JB december lepas...


Thanks for sharing.
Constant checking is regularly carried out. WE have a schedule for that. Also, when inlet pressure increase, we'll dismantle and open the strainer and cleaned them...

At Thursday, December 20, 2007, Anonymous Anonymous said...

That is some very basic algebra don't get to excited


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The Author


I’m Zaki. I used to be a project, process and chemical engineer. Few years ago I successfully became a Chartered Engineer (IChemE) and Professional Engineer (BEM). I'm now employed as a chemical engineering educator/researcher/consultant. Hope you like reading my blog. I welcome any feedback from you. My email: zaki.yz[alias]gmail.com. TQ!

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