Choosing Shell and Tube vs Air-Cooled Heat Exchangers
Selecting the right type of heat exchanger is the first step in optimizing heat transfer and costs. Two of the most common types of heat exchangers are shell and tube heat exchangers, and air-cooled (aka air cooler, aerial cooler, fin-fan) designs. Let’s compare these two heat exchanger types, and how you can select the right one.
Process Requirements and Heat Exchanger Selection
Regardless of the type of exchanger, the process engineer or thermal designer will need the process inlet and outlet temperatures, flow-rate, and the fluid properties at inlet and outlet temperatures (Viscosity, specific heat, thermal conductivity, and density). If there is phase-change (ie, vaporization or condensing), then the vapor/liquid fraction at terminal temperatures is needed, as well as heat release and property curves.
Material selection for tubes and the pressure-boundary should be performed by a metallurgist or similar expert that is familiar with the process conditions, including chemistry, fouling mechanisms, and upset cases.
Advantages and Limitations of Shell and Tube Exchangers
Shell and tube heat exchangers have several advantages, particularly in terms of their ability to handle high pressures and temperatures. These exchangers are also highly customizable, with various configurations available to suit specific process needs. Additionally, shell and tube exchangers have a proven track record of reliability and durability in industrial settings, and are readily repaired and replaced (compared to spiral exchangers, and plate & frame types).
Shell and Tube type heat exchangers require two process streams, a `hot’ one, and a `cold’ one. Depending on the service and application, the purpose of the heat exchanger may be to heat or vaporize (boil) a fluid, or to cool or condense a fluid. Shell and Tube heat exchangers are very efficient, as the heat energy from one stream is transferred almost entirely into the other one.
However, shell and tube exchangers also have some limitations. Maintenance and cleaning can be challenging in some TEMA type configurations, especially when dealing with fouling in inaccessible areas like U-bends or the shellside of fixed bundles. Shell and tube heat exchangers are typically custom-designed to the specific process, so lead-times on replacement can be longer than off-the-shelf (standardized) types of exchangers.
Benefits and Drawbacks of Air-Cooled Heat Exchangers
Air-cooled heat exchangers can have a unique advantage in cooling services vs shell & tube. By using ambient air as the cooling medium, air-cooled heat exchangers eliminate the need for cooling water, which can be a scarce or controlled resource in some regions. This makes air-cooled exchangers an attractive option for industries looking to minimize their environmental impact and operating costs associated with water treatment and disposal.
However, air-cooled exchangers also have some drawbacks. They require significant fan power to force air across the heat transfer surfaces, which can lead to higher energy consumption and increased noise levels. Additionally, air-cooled exchangers are more susceptible to performance fluctuations due to changes in ambient air temperature, and may underperform during the hottest summer days.
Hybrid Designs and Emerging Technologies
To address some of the limitations of traditional shell and tube and air-cooled exchangers, hybrid designs and emerging technologies are being developed.
One shell & tube example is the Helixchanger, which uses baffles in a helical pattern to approximate a corkscrew flow on the shell-side. This licensed technology increases the average shell-side velocity, minimizes dead zones (no flow), and reduces fouling. Helixchangers [1] [2] are effective in high-viscosity shell-side services, and can make the most of available pressure-drop.
Altex Industries also designs and fabricates low-noise air-coolers to meet new project and retrofit applications where noise restrictions must be met due to zoning and safety considerations.
Contact Altex Industries for Shell and Tube Heat Exchangers
When it comes to selecting and designing shell and tube heat exchangers for your industrial processes, Altex Industries is the leading designer, manufacturer, and turnaround service provider. Contact Altex Industries today to discuss your shell and tube heat exchanger requirements.
