Okay I have my first HX sizing for a homework problem, and I have h and k values so I can find overall U. The problem I'm having is the fact that I'm given little info for the the delta T, I'm told I want to vaporize 6,000lb/hr methanol by passing steam through the shell side of a double-pipe HX (both components are at atmospheric pressure and steam condenses through the HX). I can use a steam table, but what about the methanol? How am I supposed to find the temperature when it's entering the exchanger?
You can verify this by looking up the values for the heat of vaporization of methanol, but I would expect that it is much higher than the heat required to raise the temperature of the liquid methanol to its boiling point (from a reasonable temperature) so it probably won't have a significant impact on the design of your heat exchanger. The major portion of heat will be used to vaporize the methanol. Reasonable assumptions would be 1) start with methanol entering at room temperature, or 2) assume it's already at its boiling point. It would be interesting to see what difference it makes in your design - I'm thinking not that much. Hope this helps
