For food and beverage manufacturing — as varied as dairy, fruit and vegetable processing, meat, prepared foods, brewing and dietary supplements — the demand for heating (and cooling) requires a large amount of energy. The U.S. Department of Agriculture (USDA) Economic Research Service1 estimated that food processing in the U.S. accounted for some 2.75 quadrillion Btu (806 TWh) of energy in 2002, an increase in energy use by this sector of 8 percent per year since 1997. While there are many energy uses in food processing, this figure includes ovens, boilers and space heating, as well as processes such as drying, sterilization and concentration.
Minimizing environmental impact and lowering costs
In order to reduce environmental impact and make best use of byproducts and biomass wastes, many food producers in recent years have invested heavily in bioenergy production projects such as anaerobic digestion and biomass combustion, as well as other forms of renewable energy. While this has helped to reduce the sector’s environmental footprint, maximizing process efficiency and thermal efficiencies, in particular, is sometimes overlooked, not only as a way of improving environmental performance, but also as a means to generate greater economic returns.
Recapturing and reusing heat from other sources, such as surplus heat from cooling operations or spare boiler capacity, can be an effective way of increasing capacity or adding a new production process without the need for new, major heating or energy infrastructure. Depending on the application, some heat exchanger equipment has been shown to recover as much as 50 percent of previously wasted heat, which can then be used for water, space or process heating, waste treatment or other thermal applications.
Factors to consider when selecting heat exchanger equipment
While some processes and materials require specific equipment, such as ovens or retorts, heat exchangers are an effective and efficient solution and are more likely to enable heat regeneration than other systems. The choice of heat exchanger depends on many factors, such as the nature of the process to be carried out (pasteurization, sterilization or dehydration), the viscosity of the food or drink being processed and whether it contains particles or pieces.
Furthermore, Newtonian and non-Newtonian fluids will behave differently under different temperature and pressure regimes, and this will affect the handling required during processing. For example, if subjected to too much pressure, certain sauces may shear, resulting in failure to meet the end specification, such as pizza sauce not staying on the pizza. Another challenge is presented by certain fat-free products, which become more or less viscous with temperature, so there may be more fluid on the cooling side of the heat exchanger than the heating side.
Benefits of corrugation
Such issues can be overcome by specifying the correct type of heat exchanger for the task in hand and by careful system design. Corrugated tube heat exchangers are available in various configurations, so delicate materials such as cream can be processed without damage. The corrugated design also minimizes fouling in the heat exchanger, which increases the thermal efficiency and prolongs operational periods between cleaning. In addition, corrugated tube heat exchangers have a lower pumping requirement than smooth tubular heat exchangers due to their compact nature, which results in a lower pressure drop. This helps increase operational life while reducing maintenance costs compared with other types of heat exchangers.
For some materials, such as curd production in the dairy sector, increased turbulence can be beneficial. Alternatively, where low pressures are required, scraped surface heat exchangers keep things flowing smoothly while handling the product gently — this is one way to overcome the aforementioned pizza sauce example. Using the right type of heat exchanger can also help reduce product losses caused by materials remaining in equipment at batch changeovers or when cleaning is required. Some scraped surface heat exchangers can be configured to run in reverse, effectively removing product from the heat exchanger without damaging it or affecting its quality.
When dealing with any food processing machinery, it is critical to check for compliance with the necessary legislation; however, ultimately, the selected equipment must perform as required. And, as with any capital expenditure, it is important to compare not just the initial capital costs, but also the operational and maintenance costs across the life of the machinery. All heat exchangers are not alike, but these differences mean that there is a heat exchanger solution that fits different food processing needs.
- USDA (2010): Energy Use in the U.S. Food System. http://web.mit.edu/dusp/dusp_extension_unsec/reports/polenske_ag_energy.pdf.
Matt Hale is the international sales and marketing director for the HRS Group. He is responsible for overseeing and developing the company’s strategies for business development and marketing. Hale has a background of more than 20 years within process and mechanical engineering and aims to provide effective heat transfer solutions to overcome industry challenges. With a focus on renewable energy, he works closely with the global sales teams to achieve their goals.