Just as the name implies, a heat exchanger is a piece of equipment that transfers heat, usually between one or more fluids. Heat exchangers are ideal devices that are commonly used in refrigeration, air conditioning units, power stations, sewage treatment, gas processing and even when it comes to regulating engine cooling in internal combustion engines.
Heat exchangers are classified by how they operate, however they’re typically categorized into three main types – shell and tube heat exchangers, compact heat exchangers and air cooled heat exchangers. The shell and tube heat exchanger type is the most popular, as it’s estimated that over 50 percent of all heat exchangers currently in operation today are of this variety. However, in some applications, it makes more sense to go with one of the other types. Before we get into more concrete advice on how to choose a heat exchanger, it’s first important to note the major differences between the three main types.
Main Types of Heat Exchangers
- Shell and tube: As we noted, these are the most popular type installed – and they’re also the best understood. They’re versatile in the service that they can provide across a span of applications and work at a wide range of pressures and temperatures. Shell and tube exchangers are also made to last, and are normally able to withstand rugged environments.
- Compact: Compact heat exchangers are a more affordable option, available in a wide variety of configurations. They enable high heat transfer coefficients (up to 3 times greater than what is permitted by a shell and tube exchanger) and also permit high temperature crosses to be achieved. What’s more is that, fitting to the name, these heat exchangers have a small footprint and are easier to be installed in confined spaces.
- Air cooled: Air cooled heat exchangers are ideal options for applications that involve cooling water or applications where cooling water is expensive. A big benefit of these types of heat exchangers is that they have low operating costs and normally require less maintenance compared to other models. However, they’re considered the most expensive of all heat exchangers.
Choosing a Heat Exchanger
Now that we’ve covered the main types of heat exchangers, you can probably already get an idea of which one is correct for your application. But it’s also worth noting that just because the shell and tube exchanger is the most popular doesn’t mean that it’s a sure-fire fit for your application. That’s right, the heat exchanger that you choose should largely be dictated by the application. Failure to choose it in this manner can lead to poor plant performance, operation issues and even full-blown equipment failure. But aside from deciding what type of heat exchanger is ideal for your application, there are other factors to consider. Here’s a closer look:
- Total lifecycle cost: The total lifecycle cost of a product, let alone a heat exchanger, includes the initial purchase price, the installation cost, the operating cost and maintenance costs until the product is not used anymore. So, for instance, if a company decides to purchase a compact heat exchanger because they’re generally cheaper and can be installed easier, the may have to weigh the fact that it may cost more to maintain due to the thin nature of wall thicknesses of compact models. Conversely, while shell and tube heat exchangers are generally more expensive, their rugged build helps them stand up better over time. Air cooled exchangers have a high initial purchase price, but are relatively inexpensive to operate and maintain. These are all factors that must be considered when weighing total lifecycle cost.
- Application: What role does your heat exchanger need to help perform? Boiling? Condensing? Something else? This is a huge consideration, as the application will, in most cases, dictate the type that you need to best accomplish the task at hand.
- Operating pressures/temperatures: What type of temperatures and pressures is the heat exchanger intended to work with? That’s a big question to ask, as it will dictate your selection.
- Durability: Depending on the application, the heat exchanger may have to do its job in some very demanding conditions. If that’s the case, it’s important to consider an exchanger’s durability and reliability. For instance, as we noted above, shell and tube exchangers are usually very rugged in build and able to stand up well in demanding environments, compared to compact exchangers, which are normally made to be less durable.
- Footprint: What type of space are you working with? Is it a large space? Or do you need something that will fit in a confined space? That will also largely dictate your heat exchanger selection. Compact models are small and able to fit in a more confined area, while air cooled models require a large space. Shell and tube heat exchangers are on the larger side, but generally more versatile in terms of installation space required.
- Accessibility: How easily will the heat exchanger be able to be reached for the likes of cleaning and maintenance? Despite the reputation of some heat exchangers being more durable than others, routine maintenance is almost always key to longevity.
- Operating specs: This goes along with application, but it’s important to know exactly what you need your heat exchanger to do, and what temperatures and pressures it needs to be able to withstand in order to do it. Operating specifications are a big reason why the shell and tube heat exchangers are the most popular – they’re able to work across the widest variety of temperatures and pressures.
- Other considerations: Other considerations on how to choose a heat exchanger include things like the fouling characteristics of the fluid, any utilities that are available (i.e. cooling towers, steam, etc.), potential for future expansions and the impact that the heat exchanger has on the overall environment.
Another big consideration is cost, as heat exchangers aren’t cheap, especially those of the air cooled variety. Though essential to the operations of many facilities worldwide, heat exchangers may put plant managers in a bind if one of their units prematurely fails or needs extensive repair. If replacement isn’t in the budget, what can you do? That’s where a credible site like Bid on Equipment can help, as the service provider collects pre-owned industrial equipment and puts it back on the market for sale. Think of it like getting a functional, like-new product at a used price. It’s these lower price points that can do wonders for a company.
For more information on heat exchangers, and to browse Bid on Equipment’s selection of this equipment, contact us today.