Choosing Between Air Cooled and Shell & Tube Exchangers
When selecting a heat exchanger for a project, you must consider a variety of factors, such as the process (type of fluid) being used, the required operating temperature range, available utilities (power, glycol, water), and the available plot space. Depending on the specific needs of the project and plant, an air cooled exchanger or a liquid-cooled shell & tube heat exchanger may be the best choice. Let’s discuss the advantages and disadvantages of each type of heat exchanger so that you can make an informed decision about which one is right for your project.
Factors to Consider
There are a few things that will influence whether an air cooled exchanger or liquid cooled exchanger are best for your plant and needs.
Temperature Approach: Temperature Difference Between Hot and Cold Fluids
The temperature approach in a heat exchanger is the temperature difference between hot and cold fluids streams. If the temperature approach is tight (small), an air-cooled exchanger will require more surface area to compensate and may be uneconomical. Air cooled exchangers are ideal when the desired process outlet and ambient temperatures have a differential greater than about 5°C (9°F)
For temperature approaches less than 5°C (9°F), a shell & tube heat exchanger, evaporative cooling, or refrigeration process may be required.
However, if the temperature approach is large, shell & tube heat exchangers are well suited to recovering the heat energy prior to an air-cooled exchanger for the final waste heat.
Availability of the Coolant: Is There a Cooling Water System in the Plant?
If you have a cooling water (or glycol) system in your plant, then you may consider using a liquid-cooled exchanger. Liquid-cooled exchangers are effective because they can transfer more heat per unit area than air-cooled exchangers – thus requiring less space, and also do not require additional power (eg, electric motors for fans). If you do not have access to a cooling water (or glycol) system in your plant, then an air-cooled exchanger may be the better choice.
Power Needs and Availability
Air-cooled exchangers are available as forced-draft (fan under bundle), induced-draft (fan above bundle), and natural draft (no fan). Forced-draft and induced-draft both require power sources to drive fan motors. Natural-draft air-cooled exchangers work via a difference in air density as heat energy is transferred from the process fluid to outside air. If you do not have access to power, then a natural-draft air-cooled exchanger or liquid-cooled shell & tube heat exchanger may be the appropriate choice.
Heat Transfer Area: Do You Have Enough Plant Plot Space?
Air-cooled exchangers are much larger than liquid-cooled exchangers, so they tend to be difficult to install in small spaces. Additionally, air-cooled exchangers have access requirements for periodic maintenance like belt tensioning and bearing lubrication. Shell and tube heat exchangers may be easier to retrofit into an existing plant provided that piping and supports can be modified. On the other hand, if you have the available plot or pipe rack space then an air-cooled exchanger may be a suitable choice.
Find the Perfect Air Cooled Exchanger for Your Plant With Altex
As a leading air cooled exchanger manufacturer in Canada, Altex has the right heat exchanger for your plant. Our team of thermal design experts will help you select the right exchanger for your project and ensure that it meets your needs. Contact us to discuss your project requirements and get a quote.
