Overall heat trasnfer coefficient
Overall heat trasnfer coefficient
(OP)
We've got an odd design of heat exchanger reactor (Its sort of multi pass cross flow as a best description in Heat exchanger terms.)
When we calculate values for U we get different values for whenever we run the heat exchanger at different stream 1 flowrate, stream 2 flowrates, stream 1 inlet temperature and stream 2 inlet temperature. So giving the sales guy a U value to use in the sales literature is proving difficult.
Is it normal to get U values that vary (Considerably) depending on the conditions or is something odd going on physically inside the thing or during calculations?
Hope someone can be of some help!
When we calculate values for U we get different values for whenever we run the heat exchanger at different stream 1 flowrate, stream 2 flowrates, stream 1 inlet temperature and stream 2 inlet temperature. So giving the sales guy a U value to use in the sales literature is proving difficult.
Is it normal to get U values that vary (Considerably) depending on the conditions or is something odd going on physically inside the thing or during calculations?
Hope someone can be of some help!





RE: Overall heat trasnfer coefficient
RE: Overall heat trasnfer coefficient
Good luck,
Latexman
RE: Overall heat trasnfer coefficient
RE: Overall heat trasnfer coefficient
If your flows and properties span from laminar to turbulent flow, you can have a wide range of U's.
Good luck,
Latexman
RE: Overall heat trasnfer coefficient
A lot of our vendors are lab based chemists (Its only a small unit...) whom seem a little bemused by the whole heat transfer coefficient thing (No offence to any heat trasnfer savvy chemicsts reading!) so seem to want to know a U value and the higher the better...
Thanks!
RE: Overall heat trasnfer coefficient
You need to pick a design condition representative of whatever you establish as a benchmark with respect to throughput, output, or whatever it is that your sales guys are trying to sell and calculate and use the U value for that specific point.
Any variance from that point is a whole different world.
rmw
RE: Overall heat trasnfer coefficient
Many thanks for everyones Input!