Heat exchangers serve so many purposes, from transferring energy from one source to another to speeding up a cooling process by removing heat, that a custom design is sometimes necessary. Shell and tube heat exchangers and plate heat exchangers may fit most applications, but there are situations in which a custom heat exchanger may be necessary.
For example, some processes require dangerous and even toxic chemicals; others require separating fluids with heat transfer surfaces, and still others allow the fluids to come into contact. Other factors such as space limitations, fluctuations in the flows or temperatures, the presence of solids within fluids, and whether cooling with air is a possibility should also be taken into account.
Are there any space limitations that need to be accounted for?
The first thing to consider when designing a custom heat exchanger is the area that it needs to fit into. Every other part of its design will be based on this factor. Shell and tube heat exchangers are great for many things, but, if space is limited, something more compact like a plate heat exchanger will be necessary. Let’s face it. If it doesn’t fit, even the best heat exchanger in the world won’t fulfill your needs.
What types of fluids are you working with?
The fluid you intend to use with a heat exchanger will also have an impact on how it should be designed. Not every fluid is intended to be used in processes that require high pressures and heat. For example, fluids intended to be used for a solar water heating system are not the same as those needed for applications in the chemical processing industry.
Also consider that, while smaller diameter tubes are most often used when dealing with higher pressures, not every fluid is ideal for this design. Fluids that are prone to fouling should be run through thicker tubes that don’t clog as easily and which require less cleaning.
Do any of the fluids contain solids?
In addition to taking into account which fluids you’ll be working with, also consider whether any of the fluids that you’ll be using contain solids. Major problems with fluids typically revolve around their corrosiveness and viscosity, either of which can be detrimental to a heat exchanger if it is not designed to handle them. If these types of fluids are going to be used, the area where they’ll be contained should be made of anti-corrosive materials.
Are there any fluctuations in the flows or temperatures?
Vast flow and temperature fluctuations also require special consideration during the design process. First of all, dealing with higher flows and temperatures necessitates thicker walls that can withstand a more intense impact. While a faster flowrate leads to more efficient heat transfer, viscous fluids with low to moderate flowrates need more passes to achieve the same results as less viscous fluids.
In some cases, flowing back and forth rapidly may actually be more cost-efficient than keeping the fluid shell-side. However, increasing the diameter on the shell-side may affect flow pattern, offsetting the benefits of a greater flowrate. This should be accounted for on the tube-side as well, as more passes, although beneficial, may decrease the unit’s pressure.
Is cooling with air a viable option?
In some cases, it is possible to forgo traditional shell and tube and plate heat exchangers altogether in favor of an air cooled heat exchanger. While cooling with air is sometimes a necessity, it also has its share of benefits, including the fact that it is far less expensive than water and other fluids. Cooling with air is a method used everywhere from biomass plants to drilling rigs, and, with an ever-increasing number of uses, it’s a more feasible option than many people realize.
When designing a custom heat exchanger, there are a number of factors to consider. The amount of space available, type of fluid being used, whether the aforementioned fluid contains solids, fluctuations in flows and temperatures, and whether cooling may be an option are all crucial questions that must be answered before the design process gets underway.
Designing and installing a custom heat exchanger is meant to be handled by experts in the industry. By answering all of the important questions and working side-by-side with an expert in the design process, you’re guaranteed to end up with a custom heat exchanger that fits your needs perfectly.