Suggested Response - Q4

* The overall heat transfer coefficient for a new piping process is 400 Wm-2 K-1. Due to fouling, over time the effective heat transfer coefficient becomes 350 Wm-1 K-1. Calculate the magnitude of the fouling factor that has developed over a period of time.

Response:

Fouling adds an additional resistance term that needs to be taken into account in the calculation of the overall heat transfer unit. If we call the initial and final overall heat transfer coefficient U and U’, then we can write:

fraction numerator 1 over denominator U apostrophe end fraction space equals space 1 over U space plus space r

Entering the values and solving for r, we have:

1 over 350 space equals space 1 over 400 space plus space r

r space equals space 0.000357 space m squared space K space W to the power of negative 1 end exponent

Note, this is the resistance due to fouling. The fouling coefficient is then:

fraction numerator 1 over denominator 0.000357 end fraction space equals space 2 comma 801 space W m to the power of negative 2 end exponent space K to the power of negative 1 end exponent

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