2 replies to this topic

[schrodingersmeow]

I've been revising evaporation and although I have the solutions for this question, I don't entirely understand, can somebody help me out with it?

A forced circulation evaporator is to concentrate 60,000 kg/h of 44% NaOH to 65%, using steam at 3 atm pressure. The feed temperature and the condensing temperature are both 40 ºC. The
density of the feed solution is 1,450 kg/m³. The overall heat transfer coefficient is 2,000 W/m²-ºC.

Determine the steam requirement, the required heat transfer area and the system economy.

[schrodingersmeow]

can i use kj/kg instead of btu/lb or do i have to use btu/lb for enthalpies?

[Art Montemayor]

You state you have the solutions for the problem presented. The solutions (or simply the numerical answers) are not important to an engineering problem. An engineer has to prove with concise and clear logic and algorithms that his mathematical steps are not only valid, but clearly represent a credible and logical answer to the problems presented.

Therefore, I don't pay attention to the numerical answer; I am interested in HOW YOU DERIVED AND DEVELOPED THE CORRECT LOGIC AND ANSWER. All engineers are required to show their work, not only the resulting answers. Therefore, could you please present your detailed calculations (in a handy Excel spreadsheet format) so the Forum members can review, check, and verify them? If any faulty or erroneous logic and math is found in the calculations, this will be noted and you will receive helpful hints and recommendations on how to avoid such mistakes.

You are free to use any energy units per unit of mass as ethalpy values.