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Heat exchanger choices explored

01 July 2024

Matt Hale discusses the different types and heat exchanger designs that are available for use in food processing applications and offers some advice on which to choose for a range of different applications.

Multi-tube heat exchangers are suitable for products with low to medium viscosities.
Multi-tube heat exchangers are suitable for products with low to medium viscosities.

The first consideration when specifying a heat exchanger should be whether the application requires complete stainless-steel construction for hygiene reasons. The next consider revolves around the nature of the material being processed, in particular its viscosity and whether it contains particles. 

The simpler and less viscous the material being processed, the simpler the heat exchanger can be. However, materials become thicker, or contain suspended particles or large solids, then heat exchange becomes more challenging, and more sophisticated designs will be required to ensure the desired performance. 

Heat exchanger choices start with simple multi-tube designs, moving through double tubes – where viscosity is higher or solids are present – and annular space designs to handle highly viscous products. The most challenging materials will require the use of scraped surface heat exchangers (SSHEs).

Difficult applications
SSHEs are often the preferred choice for difficult heat transfer applications; for example, those with high viscosities and where fouling can become a problem. Users can choose between SSHEs with a reciprocating movement to provide gentle mixing for delicate products, such as whole fruit or vegetable pieces; or a rotary design which is considered to be well suited to use with high fouling fluids where thorough mixing is beneficial.

Another consideration is what happens in the event of a leak. In certain circumstances – particularly where the service fluid is not water – a leak can be business critical. In such cases, double tubeplate multitube heat exchangers should be considered, as these provide leak detection in order to avoid cross contamination between the service and product fluids.

Most heat transfer applications will require the use of corrugated tube heat exchangers which offer a number of benefits over smooth tube designs – in particular, heat transfer and energy efficiency are increased, making them better for high-capacity heating or cooling. Fouling is also minimised meaning that units can be more compact and economical, and cleaning and servicing requirements are reduced. Corrugated tube heat exchangers for food use include annular space heat exchangers; double tube heat exchangers, and multitube heat exchangers.

Annular space heat exchangers are designed to ensure thorough heat transfer in high viscosity products. The product flows through the annular space between the inner and outer tubes, through which the service fluid flows to ensure even heating or cooling. As well as highly viscous products such as ketchup, honey, some dairy products and vegetable fats and oils.

Double tube heat exchangers consist of a tube within a tube and are considered to be the most versatile corrugated tube heat exchangers. They are typically designed for more viscous products or products with large particulates in suspension, such as fruit mixes.

Multitube heat exchangers are the simplest design and carry the product in more than one interior tube, while the service fluid flows through the surrounding shell. 

Matt Hale is Global Key Account Director at HRS Heat Exchangers.


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