This article is intended for beginners. No additional knowledge needed to understand this topic, why not try?
I have more than 10 plate heat exchangers (PHE) in my plant. We typically control flow, inlet and outlet temperatures, and pressure. Before joining the company, I noticed that “on-site cleaning” (CIP) using caustic soda solution was carried out when PHE could no longer produce the required flow and temperature output. This is one of the ways to eliminate contamination and scale on the surface of the plate to improve heat transfer. If the CIP does not work, we must dismantle the PHE, clean the plates in the hot caustic and attach a new gasket to it. This will be a much more expensive option and will take longer.
To avoid mass contamination and scaling from deterioration, we must regularly conduct CIP. When is the right time to perform CIP? As stated above, when the flow rate is low or the desired outlet temperature cannot be reached, we will consider the possibility of performing CIP.
However, I came out with a simple calculation of the heat exchanger, the formula for calculating the “total heat transfer coefficient” (U-value) of the heat exchanger. The value of U will give me some indication that the heat exchangers provide the worst heat transfer. By simplifying the formula in the excel file, I can easily find out which heat exchanger needs attention by simply inserting the inlet / outlet temperature, mass flow rate, heat capacity of the oil and the surface area of the plates. LMTD (average temperature difference in the register) will be obtained from the formula and then applied to obtain the value of U.
I use and process the following formulas:
Q = mc (theta) = UA (LMTD)
Can you develop a formula?
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