Industry 4.0 Innovations Make It Easier to Monitor and Optimize Air Cooled Heat Exchangers
Air cooled heat exchangers are a staple of the Canadian petrochemical industry, vital to everyday processes such as cooling glycol, water, or lube-oil.. Air-cooled heat exchangers take waste heat from processes and exchange it into the atmosphere as a cooling process, allowing for higher plant efficiency.
However, one problem with heat exchangers is that, traditionally, measuring their actual performance and optimizing maintenance has been extremely difficult. In many cases, “good enough” or “does the job” was simply accepted as the most cost-effective capital and operational target, because more precise measurements of performance could easily be more costly than the benefits it brought.
New technology is changing that viewpoint. The adoption of “Industry 4.0” technologies, including monitoring and wireless sharing of performance data via Internet-of-Things (IOT) devices finally makes precise heat exchanger optimization achievable.
In this article, we’ll discuss the basics of how air-cooled exchangers work, the challenges to properly monitoring them, and how new technology is enabling more productive implementation here in Alberta.
I. The Basics of Air Cooled Exchangers
While most readers are likely familiar with the basics, this makes for a good foundation.
The basic function of an air cooled heat exchanger is to remove heat from a process stream and reject that heat into the atmosphere. Heat transfer occurs when there is a temperature differential between two (or more) reservoirs, and there is a shared surface to conduct heat energy across. In this case, tubes provide the surface area and contain the process inside with air outside. Fins are used on the outside surface of the tubes to maximize the surface area in contact with the air, thus improving overall heat transfer.
The air on the outside of the tubes must be kept moving to encourage heat transfer, so fans are typically added to the process, maintaining a fresh supply of cold and turbulent air. Likewise, the process fluid must keep moving inside the tubes via a pumped (pressurized) system.
Winterized air-coolers recirculate cold in the winter for start-up and to control process cooling, utilizing louvers controlled by actuators. Steam, glycol, or electrical heaters are used to bring up ambient temperatures during the coldest start-ups. In short, running an air cooled heat exchanger is something of a balancing act. Every element added to the system can have some level of variance in its performance, and different mechanical systems are stacked and combined to control overall operation. This begins to point at the challenges associated with accurately monitoring, logging, and acting upon the inputs and outputs to optimize the air-cooled heat-exchanger system.
II. Monitoring Challenges with Air Cooled Exchangers
Let’s dig into the problem in a little more depth, by looking at a couple of specific scenarios where monitoring would be useful, but difficult with previous technologies.
1. Heat Transfer Effectiveness
The most important thing to know about heat transfer effectiveness in air-cooled heat exchangers is that, natively, they can only cool the system down to approach the local ambient temperature. This is when adding water sprays and evaporation can help push the cooling further, – but sprays become ineffective if the local heat/humidity is too high, and worse, they also quickly foul the air-side tubing and reduce performance further..
When attempting to maximize cooling, it can be tempting to simply run fans at maximum power – but that isn’t necessarily effective, and it’s rarely efficient, especially when ambient temperatures are elevated. Another complicating factor is that the desire for these systems may not be to simply maximize cooling, but rather to maintain a specific process outlet temperature. In these cases, the most efficient process would be to only use the exact amount of air cooling required, but precise fine-tuning is difficult to achieve.
Given the large size of many industrial air-cooled heat-exchangers in Alberta, there is potentially a lot of energy being wasted, especially by the fans – but how do you find those efficiency gains? And how do you do it without adding so much to the overall costs that it outweighs the gains?
This points to the problems with min-maxing heat transfer efficiency.
2. Heat Transfer Efficiency
Any heat exchanger system will have a theoretical maximum cooling ability, based on the amount of surface area within the system, and the physical properties of the materials and fluids being used. However, of course, no system ever achieves 100% maximum efficiency in any scenario due to confounding factors.
With air cooled exchangers, fouling can be the biggest problem for achieving high levels of efficiency. Various fouling mechanisms are possible (corrosion, chemical, biological) which will be deposited on the inside surfaces of the tubes. Over time, this buildup creates an insulating layer which quickly reduces heat transfer efficiency.
In addition, the same can happen to the system’s exterior. The fan system uses atmospheric air which will contain dust and other contaminants and can quickly foul and inhibit the proper functioning of the fin tube heat transfer surface.
Over time, these fouling elements will create a significant reduction on overall system performance. However, due to the slow buildup (much of this happening within the closed elements of the system) monitoring and tracking is difficult.
For decades, these were problems that owners and operators simply had to live with and fix on a case-by-case basis. Now, new technology is making it possible to gain more precise oversight of your heat-exchanger systems and make more-precise adjustments to the system which will help improve efficiency.
III. Industry 4.0 And Air Cooled Heat Exchangers
Industry 4.0 is a blanket term referring to industrial upgrades that leverage technologies such as AI oversight, smart robotics, and the usage of wirelessly connected “Internet-of-Things” monitoring devices. Previously, the devices needed to measure operations within heat exchanges were too expensive, cumbersome, or difficult to use for most applications. Now, the monitoring devices are small enough to be attached to almost anything, without requiring their own separate power or networking cables.
Sensors can be attached at multiple points in the system. They can connect to the exchanger itself, as well as monitor key indicators at various points upstream or downstream. Likewise, fans, motors, actuators, and other electrical or mechanical devices can be monitored independently for operation, power consumption, and other performance metrics.
If needed, more sensors can be added for other factors such as measuring vibrations, and noise, or even monitoring heat within the fan motors for signs of malfunction. Measuring fouling is even possible, by monitoring pressure and temperature differential for gradual changes over time.
One major improvement in these devices is that they can be entirely external, rather than requiring embedded monitors within the heat exchanger. Those monitors could be a confounding factor themselves, a problem that is avoided when all sensors are external and non-invasive.
Added up, these monitoring systems allow for much more detailed insights into the performance of a heat exchanger setup.
Just as some examples of how this can be utilized:
1. Detailed performance dashboards
The information gathered from the sensors is typically sent to a centralized cloud-based database, where it’s pulled in by a user-accessible dashboard. This allows for highly granular views of every monitoring component within the system, as well as viewing and reporting on aggregate data relating to overall system efficiency or effectiveness. Operations overseers can have more direct knowledge of the moment-by-moment operations of their heat exchangers than before.
2. Early warning of gradual issues like fouling
The biggest challenge to detecting fouling in the past was the incremental nature of the buildup. Day by day, there would be no detectable change in overall efficiency. Only by gathering data over long periods of time can the telltale signs of fouling be seen – which is now possible, as these systems are logging every bit of data for future trend analysis.
The same is true for other gradual deterioration, such as motor bearing lubrication and wear. The system will log incremental heat, noise, and vibration increases, making the data visible and actionable.
3. AI oversight of critical systems
To be clear: What is currently called “Artificial Intelligence” is not actually intelligent in any way, despite how some marketers try to call it “smart.” However, well-programmed modern “AI” solutions are still capable of decision-making based on pre-determined factors and scripting. Once appropriate performance baselines are established, the AI system can then monitor for any changes or issues which fall too far outside allowed variances. These could be large-scale issues or smaller-scale discrepancies which might escape human attention.
From there, the AI could potentially alert human operators, or it could be programmed to take corrective steps of its own. For example, if a vibration transmitter was triggered – the AI could be scripted to power down that fan motor to prevent further mechanical damage, while also notifying an operator to action maintenance.
Industry 4.0 Upgrades Bring Smart Long-term Optimizations
All told, this makes it possible for a new level of efficiency and min-maxing when operating a heat exchanger system. Operators have better insight into operations, both in the short- and long term. Robust reporting allows them to investigate and analyze any particular aspect of operation, while well-programmed AI systems monitor for any immediate problems and take steps to minimize the harm done.
While the upgrades themselves are not free, the overall benefits they bring can frequently outweigh the costs – especially when they can also reduce failures, downtime, and other drags on productivity. Further, these systems become more valuable and effective over time, by leveraging the ever-growing database of performance information to find more subtle opportunities for optimization.
Air Cooled Exchanger Services in Alberta
Altex is Alberta’s leader in air coolers and heat exchangers, and we proudly stay at the forefront of modern technology. If you’re facing challenges monitoring or optimizing your air cooled exchangers, contact us for assistance.