A question on chemical engineering principles?
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141 When the heat load of the heat exchanger remains constant, reducing the amount of cooling water used will result in ( ). A. The cooling water outlet temperature rises, and the heat transfer area decreases. B. The cooling water outlet temperature rises, and the heat transfer area increases. C. The cooling water outlet temperature decreases, and the heat transfer area decreases. D. The cooling water outlet temperature decreases, and the heat transfer area increases. Additional note: It would be best to use formulas to explain this, thank you.
B It seems there’s something wrong with this question. Since the heat exchangers have already been determined, will the heat transfer area change?
The increase in outlet temperature can be calculated using formulas, while the heat exchange area can only be determined based on quantitative data. In extreme cases, when the amount of cooling water is infinitesimally small, the heat exchange area must be large enough to meet the requirements; therefore, option B is the correct choice. Personal opinion
As the outlet temperature increases, △Tm decreases. So A increases
It should be B, I agree with the opinion from floor 3
That’s right, but is K still constant? It seems like K also decreases, right? ?
Do you mean that a decrease in flow rate will result in a lower velocity? What causes the K value to decrease?
The heat load Q = q1·p1·C1·△T = q2·p2·C2·△t. When Q remains constant, if q2 decreases, then △t increases. The heat exchange area F = UQ/K△t; it seems that K changes, making it difficult to discuss F
With a constant heat load, as the cooling water volume decreases, the outlet temperature should drop, and a larger heat exchange area is required