2 replies to this topic

[chem101]

Hi every One:
Is that true that One can size exchanger based on Heat duty?
From engineering point of view one need to know the out let temperature if not then
using material balance Outlet Temperature can be found but one of my co-worker was
saying that using heat duty you can size heat exchanger. I disagree with that, but don't know how to explain Please help me if you can.
Thank you very much

[Art Montemayor]

Chem:

You have not filled in all information in your profile. We also don't know your academic level as a student. Consequently, not knowing your background and training makes it hard to understand what you are stating.

The basic equation under which all heat exchangers operate is:

Q = (U) (A) (LMTD)

where,

Q = the heat duty imposed on the exchanger;
U = the Overall Heat Tranfer Coefficient for that exchanger & service;
A = the total heat transfer area required to carry out the stated duty;
LMTD = the Log Mean Temperature Difference across the exchanger.

The prime information required to size and design a heat exchanger is the DUTY of the same. This is analogous to the problem of carrying sacks of potatoes with a horse: You must first identify the size (weight) of the load (duty). If the load is heavy, you select a Belgium Draft horse to carry the load; if the load is light, you might get by with a Shetland pony.

Without an identification of the duty, you cannot size or design a heat exchanger.

[chem101]

Thank you Mr. Art;
Sorry for not filling the all information. its because i don;t have too much information. I finished my Chemical Engineering Degree but i am still in process of learning about Engineering. I appreciate your answer.
Thanks one again.