Common Issues for Poor Heat Exchanger Performance
In this article, we aim to identify the critical issues which may have implications on process plant performance and offer some ideas on how to overcome those problems.
Much of the time heat exchanger performance issues can be fixed with a variety of simple solutions, such as turbulators in particular hiTRAN® Thermal Systems, which will ensure your process plant continues to maximise its performance. However, in some instances the most common heat exchanger problems can be a lot harder to resolve, leading to ever-increasing operating costs and high capital costs. Some of the most common heat exchanger problems for many process plants include the following;
- Vibration issues
- Exchanger leakage
- Increasing exchanger energy consumption
- Pass Partition bypassing (thermal leakage)
- Air cooler air recirculation
All of the above problems can contribute to an under-performing exchanger, the main issue is determining the critical problem (or a combination) that needs to be resolved.
An audited approach to analyzing the given heat exchangers needs to be adopted, as one particular problem can be closely linked to another problem on the list; acting as a chain reaction. A lot of exchanger leakage can be found to come from flow distribution issues. If the flow through the exchanger is not uniform, then high flow velocities can cause an additional problem, vibration. This vibration can increase the effect of erosion in exchangers which then leads to frequent leakage of exchangers creating problematic maintenance and associated costs. CFD services, provided by CALGAVIN®, can be used in a variety of ways to address flow distribution issues inside heat exchangers. This allows engineers to manipulate the flow via changing pressure drops through appropriate solutions offered.
Closely linked to flow distribution problems, is high energy consumption in terms of utilities. With varying flow velocities occurring, there will be tubes or areas on the shell side where poorer heat transfer is taking place compared to other areas inside the heat exchanger. Operationally fans and pumps are usually increased in power to overcome the poor heat transfer, but such technologies as CALGAVIN’s hiTRAN Thermal Systems that greatly improve the heat transfer efficiency, produce a decreased demand of cooling or heating energy needed for a given duty.
Traditional engineering practices such as site visits, taking measurements and examining the exchanger in operation also play a part in determining pass partition bypassing. Infrared thermal readings can resolve an unidentified problem with a simple solution. Onsite audits can also determine air recirculation problems, taking into account the exchanger’s surrounding environment which can also have an impact, i.e. high winds, nearby exhaust gas etc.
Example of Fouling
Finally, the problem of fouling can come in many forms listed below, but it is essential to determine the type of fouling, and it’s a mechanism to offer a solution.
Different types of fouling can be described as the following;
- Polymerisation and or oxidation
- Settlement of sludge, rust or dust particles
- Biological deposits
Fouling, in general, can be determined by either the nature of the fouling process fluid, the heat transfer process or both. Biological fouling or settlement of particulate can usually be rectified by making appropriate low cost process change to slow down the impact of these types of fouling. Improved filtration of water is usually associated with biological fouling before the exchanger, greatly improving operational performance. Again further filtration processes can be implemented upstream of the exchanger to remove particulate from process streams as well.
However, a substantial mechanism for many types of fouling is heat transfer. For crystallization, decomposition and polymerisation heat transfer play a part in the rate of fouling that occurs. For polymerisation or decomposition, high temperatures increase the rate of fouling occurring. By decreasing the temperatures this will obviously slow down this rate and therefore in some cases reduce the frequency of cleaning. This applies to also crystallization, where low temperatures drive the fouling so therefore maintaining higher surface temperature can impair the effect.
At CALGAVIN we can use heat transfer enhancement technologies to improve the heat transfer, therefore positively changing the temperatures needed to process a duty in the direction where fouling can be mitigated through large increases in heat transfer efficiency. There are many other common heat exchanger problems which can be very specific to any given process plant or heat exchanger variety; some of the problems might only occur within one plant due to the type of fluid being processed.
Our heat transfer engineers have extensive knowledge of thermodynamics, heat transfer and fluid flow, combined with the experience of providing solutions to hundreds of plants and engineering teams worldwide.
For more information, or should you have any questions, please contact us on (+44)1789 400401 or email email@example.com.