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HEAT TRANSFER NINE QUESTIONS TO ASK ABOUT HEAT EXCHANGERS
Matt Hale, Global Key Account Director, HRS Heat Exchangers, lists nine questions to ask your potential heat exchanger supplier
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eat exchangers are commonly used for a wide range of purposes in the food industry, from pasteurisation, sterilisation and evaporation to general heating and cooling. With a wide range of types and designs available from numerous manufacturers, choosing the right solution, from the right supplier, can seem daunting. However, posing the right questions at the beginning of the procurement and design process can prevent future
misunderstandings, and ensure that you arrive at the optimal product or system for your specific requirements. Here are nine key questions to ask any potential heat exchanger supplier…
1. Do I actually need a heat exchanger? Although heat exchangers are the preferred option for many food processing processes that include heat (pasteurisation, sterilisation, evaporation, etc.), it is a good idea to consider alternatives. In some situations, a straightforward heating element or refrigeration system may be more suitable. A creditable heat exchanger supplier will not try to sell you a solution that you don’t need. 2. What type of heat exchanger best suits my needs?
The simplest option are plate heat exchangers (PHEs), which consist of combinations of plates and gaskets through which the product and the heating or cooling medium move. They are relatively simple and cost-effective and do a good job with simple fluids like milk and thin oils. However, for more viscous substances, non-Newtonian fluids and processes requiring high levels of heat transfer, tubular heat exchangers are more effective.
Tubular heat exchangers come in different forms, including those with corrugated tubes. Corrugated tubes increase product turbulence compared to smooth tubes (which are more common), which prevents fouling and improves operating efficiency. Corrugated tube heat exchangers are ideal for products with medium viscosity or containing small particles in suspension, such as cream, sauces, etc. For simple fluids, such as milk, smoothies and juices, we have multi-tube designs including the MI Series and the MR Series. As materials become more viscous in nature (such as honey, soups and creams), then we
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move up through the range using tube-in- tube or annular space designs such as the DTA or AS Series respectively.
For high fouling materials and viscous fluids, or those containing large particles such as fruit pieces, scraped surface heat exchangers (SSHEs) are the best choice. Different designs (such as reciprocating or rotary versions) provide options in terms of gentle handling (to maintain product integrity, for example creams or thick sauces) or thorough mixing (mechanically deboned meat, jams, etc.), while maximising operating efficiency and uptime. 3. Will the heat exchanger cope with my product/s?
Product features such as viscosity, solids content and texture will all affect thermal and physical behaviour in a heat exchanger. Suppliers need to understand product properties, as well as factors such as required flow rate and temperature change, in order to supply the correct solution. While there may be plenty of existing data and experience for common materials such as milk, products such as complex sauces or meat products will need specific analysis and solutions. A failure to understand the product can result in ineffective treatment which affects product safety, product quality, economic returns, or usability of the equipment. 4. How will you design the heat exchangers? Does the supplier use the very latest
scientific information on energy and heat transfer, or is it relying on papers and data
which are out of date? While the heat exchanger needs to perform correctly, other considerations, such as ease of installation and maintenance, are also important. A reputable manufacturer will also be able to offer expert insights into the latest technological advancements that could benefit users’ systems process and operational costs. 5. How energy efficient is the system? Some heat exchanger designs are more energy efficient than others (for example, the use of corrugated tubes improves energy efficiency). In addition, heat exchangers may be able to recover heat from the end of the process and re-use it (known as heat regeneration).
Although potential energy cost savings need to be offset against the capital and running costs of the heat exchanger, your supplier should be able to provide details of the efficiency of their equipment and offer heat regeneration where it is desirable. 6. Will you supply a complete system? Some suppliers will only supply components, leaving the customer or a third-party engineering contractor to combine the heat exchanger and control systems with the necessary ancillaries, such as pipework, pumps, holding tanks, etc. Some systems will use a combination of two or more heat exchangers; for example, a simpler system to pre-cool or pre-heat the bulk of the product and then the more specialist system to perform the main process.
If your heat exchanger supplier proposes a complete ‘plug and play’ solution, then you can be confident that the various components will work together and the system will perform as expected. You will also have a single point of contact for any maintenance or warranty queries. 7. Do you offer bespoke solutions? Different materials have different handling requirements and there is no ‘one size fits all’ solution in terms of heat exchanger. That is why manufacturers produce a range of
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