Energy & Power, Heating, Cooling & Drying

What Are Heat Exchangers? How Do They Work? What Benefits Do They Bring To Processing Plants?

Phil Black - PII Editor 03/06/2019

660 3 minutes read

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-Thornhill Group Managing Director Simon Tin provides an overview of heat exchangers

There are three main types of heat exchangers – plate, shell and tube and air cooled. They work in different ways and are suited to various applications, but essentially, they all fulfil the same task – transferring heat from one fluid to another.

The applications for using heat exchangers in the processing sector include process heating, cooling, evaporating and condensing, all essential elements of the business regardless of what is being processed.

How do heat exchangers work?

Shell and tube systems function by passing a fluid through a set of tubes that is located within a sealed shell that contains another fluid. The liquids can move in the same direction (parallel flow), opposite directions (counter flow) or at right angles (cross flow).

Plate heat exchangers comprise many thin metal plates to provide a large surface area with narrow channels to transfer the heat rapidly.

Air cooled heat exchangers tend to be used where ambient air is the cooling mechanism. The air is forced or drawn through a tube bundle or core by rans. These can range from large 12m units on oil refineries to small units for train cabins.

Which type of heat exchanger do I need?

Selecting the right type of heat exchanger relies on reviewing a range of criteria to determine what is the most appropriate for the application and the environment in which it will be installed including:

Space – the room available will have a large impact on the sort of heat exchanger that can be used and its design

Maintenance requirements – if you have an onsite maintenance team or one provided by a third party that can respond to breakdowns or performance issues quickly then the type of system you choose will probably be very different if you don’t have access to these people.

Or if the site is in a location where it will take hours or even days to get someone to assess your equipment and fix problems that can seriously impact production maintenance provision will require different considerations.

Energy use – while no food and drink companies want to waste energy, there will be differing requirements for its consumption depending on where in the business the heat exchanger is being used

Ambient conditions – the environment in which the heat exchanger is being installed will have a large effect on its performance and how it should be designed to perform appropriately

Product lifetime – for some processes, companies will be happy to see their heat exchangers work on a “run to fail” basis while for others they need to run with minimal maintenance for many years.

Regulations – meeting statutory regulations and best practice is quite often a minimum requirement in the food and drink sector so ensuring your heat exchanger meets these requirements is essential

Factors to consider when specifying a heat exchanger

1. Design
For process plants it’s essential that the chosen supplier can design to a range of standards such as TEMA, PD5500, EN13445, API and ASME so that they can develop bespoke solutions specified in a way that is most appropriate to the application.

2. Materials
The metals used in a heat exchanger must be suitable for the environment in which it is going to be installed. This will, of course be influenced by what is being processed. For example, a plant handling food and drink will have very different requirements to one producing corrosive chemicals and the materials used must be fit for purpose.

3. Supplier’s experience and location
Clearly the more a supplier understands your business, the better they will appreciate what is important to you. In the processing sector we are proud to be able to list leading companies including Engenda, Lucite, BASF, Nestlé Suntory and Coca Cola as just some of our customers.

4. Servicing
To keep your heat exchanger system working at optimum levels it’s vital to undertake a programme of proactive maintenance so that potential problems can be identified and plans put in place to rectify them to minimise their cost and effect on the business.

However, there may still be emergency situations that require urgent repairs so it’s good to choose a suppler who can meet these needs too so that you can be confident that they totally understand your system prior to taking it apart.

5. Spares
It’s often the case that you will need spares delivered urgently so choosing a supplier that not only provides initial design and manufacture of the overall system but fabricates spares that can be stored on your site or held at theirs can be a lifesaver in emergency situations.

About Thornhill Group
Thornhill Group is the only UK provider of the complete cycle of heat exchanger services encompassing design, engineering, installation, repairs and servicing.
www.thornhillheatexchangers.co.uk