FEATURE BOILERS, PUMPS & VALVES
Heat exchanger selection tips for food producers
By Matt Hale, international sales & marketing director, HRS Heat Exchangers
H
eat exchangers are a well- established tool for the thermal
processing of materials, such as cooking, pasteurisation and sterilisation, as well as heating or cooling a range of products. When it comes to choosing the right solution for a particular situation, there is no substitute for professional advice, but you should have a basic understanding of the factors that need to be considered. These can be broadly divided into commercial and technical considerations…
1. Is this the right technology? There is no doubt that heat exchangers can be relatively complex and expensive. While they are eminently preferable in many situations, particularly where a cooling or heating source is already available or is required for more than one process, they may be over-kill for simple situations where a straightforward heating element or simpler refrigeration system is sufficient.
2. What type of heat exchanger do I need? The simplest forms of heat exchangers are so-called plate heat exchangers, 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 can do a very good job with simple Newtonian fluids like milk and thin oils. However, for more viscous substances, non-Newtonian fluids and processes requiring high levels of heat
transfer, tube-in-tube heat exchangers may be a better option. These come in different forms including those with corrugated tubes to increase product turbulence, which prevents fouling and improves operating efficiency. For high fouling and viscous fluids, scraped surface heat exchangers are available. Reciprocating and rotary versions are available, allowing different products to be handled carefully, so that key quality characteristics can be maintained or mixing increased, while providing maximum operating efficiency.
3. Will the system cope with my products? Firstly, the heat exchanger must be capable of providing the right amount of heat transfer. Different materials will have different thermal properties, which must be considered when designing a heat exchanger. Factors such as viscosity, solids content and texture will need to be assessed alongside product flow rates to ensure that the product receives the correct treatment. For example, if the heat exchanger does not deliver sufficient heat it may result in an incomplete process, which could affect product safety. At the same time, if the system does not handle certain products correctly it can change or damage their quality. Finally, the heat exchanger set-up should be capable of handling the maximum amount of product required at any time, possibly combining multiple units into suitable arrays in order to increase treatment capacity.
4. Are there any other benefits? One of the key benefits of many HRS heat exchangers is their ability to recover heat from the end of the process and re- use it. In many cases this feature enables the system to be more efficient, reducing the amount of heat that needs to be supplied in the first place. However, in some situations – for example, where the heat source is plentiful – then the recaptured heat can be used for another process or for something else altogether, such as heating offices or buildings.
28 DECEMBER/JANUARY 2018 | FACTORY EQUIPMENT
The pasteurisation process can dramatically change the properties of viscous foods
5. What are the maintenance requirements? These will vary according to the type of heat exchanger chosen, its design, and the environment in which it is used. However, the ease of maintenance is even more important. For example, how complicated is it to access key components and what are the costs of routine spare parts such as seals and gaskets? Certain factors will have a key impact on how much the heat exchanger costs to service, both financially and in regard to the time and resources required.
6. How much will the system cost? It is important to compare both the capital cost of different units and their anticipated operating costs and service life. For example, a 25 per cent higher purchase price may easily be recouped by greater product efficiency and reduced serving costs over the same, or even longer, operating life. Only by considering all the associated costs will you be able to make an accurate investment decision.
7. How will the system be designed? While it is imperative that the heat exchanger performs correctly in terms of thermal transfer, other considerations, such as ease of installation and maintenance, are also important.
Left: The latest HRS heat exchanger technology reduces energy usage and costs
8. What back-up and support is there? Not only is it important to have back-up in the event of a problem, but does your supplier offer features such as extended maintenance and servicing? Would you be able to take advantage of any future upgrades, such as improvement in tube design? It may not be essential to deal with a company that is based locally, but you should investigate how well they deal with other clients in similar circumstances.
www.hrs-heatexchangers.com / FACTORYEQUIPMENT
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