29-08-2013, 03:01 PM
Troubleshooting shell-and-tube heat exchangers
[attachment=57576]
INTRODUCTION
It is stressful when exchangers go online and don't per
form as they should. But not all scary things go "bump
in the night." Heat exchangers that go onstream and
don't perform are also scary. This is especially true if
there is a lack of thermal wells, pressure gages and
flowmeters. In addition, you are told that many hun
dreds of thousands of dollars a day are being lost due to
decreased production, so the problem has to be found
immediately. In many cases, there has to be a shutdown.
Here is helpful information on finding a cure, including:
• What information to collect and what to look for
• The importance of calculated pressure drops and how
they help analyze the problem
• Two-phase flow emphasizing low heat transfer due
to stratified flow
• Actual case histories of design and fabrication errors
to help with the diagnosis.
The concentration is on thermal problems; problems
due to vibration and exchanger leaks are not discussed
INFORMATION COLLECTION
Besides the obvious process information of flow, tem
peratures and pressure drops, you win probably need the
manufacturer's heat exchanger drawings. Hopefuny, you
will not have to run heat exchanger tests. But if you do,
there are procedures in the literature. 1, 2
U sing the collected process information, make a full
thermal design computer run. The printout will have much
more information than a standard specification sheet.
Check the printout with the following in mind:
1. Are there any error messages about the physical
properties used?
2. Are there error messages for the input data?
3. Check the section that analyzes the design for com
ments. This is a section of the program that acts as expert
system software.
[attachment=57576]
INTRODUCTION
It is stressful when exchangers go online and don't per
form as they should. But not all scary things go "bump
in the night." Heat exchangers that go onstream and
don't perform are also scary. This is especially true if
there is a lack of thermal wells, pressure gages and
flowmeters. In addition, you are told that many hun
dreds of thousands of dollars a day are being lost due to
decreased production, so the problem has to be found
immediately. In many cases, there has to be a shutdown.
Here is helpful information on finding a cure, including:
• What information to collect and what to look for
• The importance of calculated pressure drops and how
they help analyze the problem
• Two-phase flow emphasizing low heat transfer due
to stratified flow
• Actual case histories of design and fabrication errors
to help with the diagnosis.
The concentration is on thermal problems; problems
due to vibration and exchanger leaks are not discussed
INFORMATION COLLECTION
Besides the obvious process information of flow, tem
peratures and pressure drops, you win probably need the
manufacturer's heat exchanger drawings. Hopefuny, you
will not have to run heat exchanger tests. But if you do,
there are procedures in the literature. 1, 2
U sing the collected process information, make a full
thermal design computer run. The printout will have much
more information than a standard specification sheet.
Check the printout with the following in mind:
1. Are there any error messages about the physical
properties used?
2. Are there error messages for the input data?
3. Check the section that analyzes the design for com
ments. This is a section of the program that acts as expert
system software.