Heat exchangers come in all shapes and sizes. The truth is, size does matter when it comes to heat exchanger performance and investment — but not in the way that’s often assumed. Bigger doesn’t mean better. And the industry standard shell and tube heat exchanger is not only bulky, it offers very low performance for their size.
In many applications, a custom unit with a compact footprint can deliver a level of performance that off-the-shelf units simply can’t. Today’s new breed of custom, compact heat exchangers are designed and built to meet the specific needs of each application. Within a footprint that’s up to 75% smaller, they deliver better performance.
Three myths about heat exchangers
There are three common myths surrounding heat exchangers — and in some cases, they hold engineering teams back from seeing optimal performance in their systems.
The first myth is that compact means less performance. Actually, often the opposite is true. A custom-designed, compact heat exchanger — with a smaller ratio of volume to performance — delivers advantages in key areas. A reduced footprint frees up operational space, offers tighter integration, usually requires simpler connections and plumbing, and most of all provides increased overall performance.
The second myth is that a custom unit entails more overall expense. Again, often the opposite is true. The cumulative loss of performance and diminished operational space adds up, year over year, and cuts into the bottom line. The savings potentially gained by either continuing to use an off-the-shelf unit or choosing another one is likely more than offset by the costs of having a sub-optimal system.
The third myth is that off-the-shelf, basic heat exchangers are all you need. Not in this case. It’s also an essential tenet of engineering that you go for the best approach for the application. But basic is not best: Opting for the most basic solution — an off-the-shelf approach — often creates far more complications. Compromises and workarounds can add complexity to a system. And often, given the initial investment, the chances of an effective fix are years down the road.
The right size for the application
We find clients may be aware of the possible issues if a heat exchanger is not sized correctly, but don’t realize that one component can dramatically impact system performance.
Generally, an off-the-shelf heat exchanger that’s too small does not perform enough energy recovery and may create more pressure drop. The problem with more pressure drop is that the pumps/blowers wind up working harder to push things through the system, wasting energy. If you are not recovering as much energy as you should, that is another form of wasted energy: you’ll need to make that heat back up in another step — either with fuel or cooling, depending on your system goals. But adding another stage into the system adds further complexity, and may add the risk of further issues.
The solution isn’t getting a bigger heat exchanger. It’s getting the right heat exchanger for the job. In fact the right solution may not be bigger at all — just built to effectively address the user’s actual needs.
More commonly, a heat exchanger is too large — and neither overall performance nor cost are optimized. Again, the wrong fit cuts into efficiency and profitability. An oversized unit consumes valuable space in industries where every inch of space counts. Rarely is there a situation in which space isn’t at a premium when it comes to production and performance. An enterprise stuck with an oversized heat exchanger is at a distinct cost disadvantage — and it’s often when a company is looking for alternatives that the potential of custom and compact heat exchangers comes up.
Getting it right
Getting it right starts with a well-considered approach, far beyond a simple purchasing decision. Often the key differentiator is working with experts who have the data, experience, and track record to know how to best address specifications. There’s a whole range of considerations around performance. The biggest factors include:
- Suitability for the application.
- Design, construction and materials that fit the space and life requirements.
- Avoiding wasted materials or energy.
- Design of connections and mounting points.
On all four points, a custom approach ensures the best results: a heat exchanger that is designed to be a precise, optimal solution for your needs. It eliminates the long-term drain in terms of energy and operating costs and the decrease in profitability as faulty performance cuts into the bottom line.
Two cases where custom was the best solution
HRI created custom, compact heat exchangers for two industrial firms on the rise — and in each case, the design proved a far better solution:
Carbon Capture Equipment Application
For a frontrunner in liquid carbon capture, HRI’s custom heat exchanger solves long-time drainability issues in an unusual, compact design.
Challenge: Mantel, a carbon capture innovator with a promising molten salt-to-molten salt system, needed to solve a host of challenges, including salt solidification issues. When the system was shut down, the molten salt within the heat exchanger had to be drainable from both sides in order to prevent it from plugging the unit. Additionally, the unit had to operate at high pressures and be low-profile so it could fit into a very small space.
Solution: HRI addressed Mantel’s needs with a heat exchanger that has a 12’ flow length in a 1’ tall package. Fully drainable on both sides, it’s configured to ensure there’s nowhere for the molten salt to pool and potentially solidify — and plug the system upon a shutdown. It was constructed of Incoloy 800H for exceptional strength, durability, and high-temperature oxidation resistance.
Outcome: HRI’s unique, compact design met all of Mantel’s requirements and is testing well. It’s proof that a heat exchanger can be compact and durable in high temperatures and moderate pressure, be a mere 12” in height, and prevent salt pooling and plugging as well. The design adds a much-needed level of functionality to a promising and innovative approach to carbon capture. Presently, Mantel is testing it at their demonstration site in Boston, and has requested that HRI evaluate the same application at a 10X larger scale.
- Heat exchanger operates at 800C / 1472F.
- Can handle pressure at 5 bar / 73 psi.
- Prevents molten salt pooling and solidifying, ensuring the system won’t become plugged during a shutdown or cooldown.
Process Equipment Provider
For a fast-growing energy company, HRI’s custom heat exchanger is 6X smaller and 37% more effective.
Challenge: A process equipment provider needed a far more compact and efficient heat exchanger for its gas-to-gas application than it could find on the market. Its specifications included a temperature of up to 225C, 50 Barg of pressure, and a heat exchanger that could be smaller than 24 feet long. It wanted a smaller heat exchanger that freed up operational space but still packed a punch in terms of performance.
Solution: Finding the right solution wasn’t just a matter of taking the assignment and running back to the drawing board. Ongoing, interactive discussions involved the HRI team as well as the process equipment provider’s team. Among the challenges: how to balance the need for maximum heat recovery and minimal pressure drop but shrink the footprint down to a feasible size.
Outcome: HRI was able to design a heat exchanger that meets the criteria and then some: it’s not only some 6X smaller (4 feet instead of 24 feet), but it also enabled a 37% increase in heat recovery, which is an additional 23 points of efficiency:
- Original system: completing ~17.9kW(0.0611MBtu/h) = ~60% effective.
- HRI design: completing 24.5kw(0.0836MBtu/h) = ~83% effective.
The project is now in the design phase. The process equipment provider’s team is looking forward to the performance increase and space savings.
Performance, capability, and collaboration
Custom and compact heat exchangers can pack a whole lot of performance and capability into a smaller footprint. But opting for a custom, compact heat exchanger is about more than size as well. If you’re looking for a solution that can scale with your business and that brings your system closer to sustainability, it will pay to collaborate with a trustworthy partner who brings experience, data, and practical knowledge to the table.
Reach out to HRI to learn more about the advantages of a compact, custom heat exchanger.