Heat Exchangers are used in the thermal treatment of fluid foods, the concentration of juices/ pastes, chilling/ cooling or freezing of liquids, etc. The primary function of heat exchangers in the food industry to process is to enhance shelf life which maintains the stability of products at ambient / desired temperatures.
The selection and choice of which type of heat exchanger to use in a particular application depend on a number of factors, including the nature of the process fluid, the temperature difference between the process fluid and the cooling medium, the amount of heat that needs to be transferred, the space available, and the cost.
Typically, shell and tube heat exchangers and plate-type heat exchangers are used for various food processing applications. Shell and tube heat exchangers consist of a series of tubes through which the process fluid flows. The tubes are contained within a larger shell, and the cooling medium flows over the outside of the tubes. Plate heat exchangers, on the other hand, have a series of thin, closely spaced plates through which the process fluid and the cooling medium flow.
In food processing, heat exchangers are often used, for heating, cooling, chilling, condensing, sub-cooling, pasteurization, sterilization, evaporation, etc. applications. The systems designed for such applications definitively give better efficiency when enabled with corrugated tube heat exchangers and could also be with a combination of plate heat exchangers. These systems range from small skid-based systems for simpler processes to turnkey lines for fruit pulp, beverage, dairy, nutraceuticals, probiotics, ready-to-eat foods, purees and concentrates, and diced food processing.
The development of corrugated tube design in shell and tube heat exchangers is perhaps the most exciting advancement in heat transfer technology. Corrugations induce turbulence in the media and ensure a high Reynolds number even at low velocity. Such construction of shell and tube heat exchanger is made with specially designed patterns and in a manner where there is no tube wall thinning and the strength of the tube remains intact.
Heat treatment of fluid foods in corrugated shell and tube heat exchanger
Sterilization is the elimination of all forms of pathogens and organisms to allow the excellent microbial quality of the product thereby achieving better product shelf life and safety.
Corrugated shell and tube heat exchangers are increasingly used in food processing for sterilization because they are efficient at transferring heat and can handle high temperatures and pressure. The HTST (High-Temperature Short-Time) method is used to quickly heat the product to a high temperature for a short period of time in order to kill any harmful microorganisms. The UHT (Ultra High Temperature) method involves heating the product to a higher temperature for a very short period of time. These methods are used for beverages, fruit juices, particulate viscous foods, and dairy products because they can effectively kill a wide range of microorganisms. Both the HTST and UHT methods are used to extend the shelf life of the product by reducing the number of microorganisms present, which can help to prevent spoilage and ensure it is safe for consumption.
In a corrugated shell and tube heat exchanger, the food product is heated to high temperatures (such as 62.8°C for 30 minutes or 71.7°C for 15 seconds) while being circulated through tubes within a larger, external shell. The use of heat exchangers with helically corrugated walls helps to enhance convective heat transfer and increase the efficiency of the sterilization process. This is because the corrugated walls create a larger surface area for heat transfer, which allows the heat exchanger to transfer more heat in a shorter period of time. Additionally, the corrugated walls help to increase the turbulence of the fluid being heated, which further enhances heat transfer. Overall, the use of a corrugated shell and tube heat exchanger helps to ensure that the food product is adequately sterilized while also minimizing the amount of energy required for the process.
Juice manufacturers use heat exchangers to sterilize their products through a process called flash pasteurization. This involves heating the juice to a high temperature (usually around 95°C) for a short period of time, which helps to kill any bacteria or other contaminants that may be present. After the juice has been pasteurized, it is typically cooled rapidly through the systems and then within 24 hours is sealed in containers for distribution. The pasteurization process helps to ensure that the juice is safe to drink and will have a longer shelf life.
Plate heat exchangers in milk, milk based products and Juices
PHEs are used for a range of heating, cooling, pasteurization, and heat recovery, for milk In the food and dairy industry, plate heat exchangers (PHEs) are becoming increasingly popular for their versatile uses in various processes. PHEs also play a crucial role in the pasteurization of various liquids, including milk, milk-based products, and juices at 80°C AND below 25 bar pressure.
This efficient heat transfer method, using metal plates to exchange heat between fluids, allows for quick and effective processing in the beverage and dairy industry. As more companies recognize the benefits of PHEs, their usage is likely to continue to grow in this industry.
Plate heat exchangers, or PHEs, have become widely used in various industries for their efficient heat transfer and easy dismantling for cleaning and sterilization. This makes them particularly useful in the food and dairy industry, where cleanliness is of utmost importance. Overall, these benefits make PHEs a popular choice in many industries.
In the food industry, heat exchangers are commonly used in processes such as juice production, paste production, and production of milk/milk-based products. They are also utilized in the beverage industry, pulp/puree, dairy, ready-to-eat, nutraceutical, pharmaceutical, chemical/ agrochemical, fertilizer, cement, paint, oil and fats, steel, power, and many more industries also heavily relies on heat exchangers.
Each industry may have different limitations and therefore require specific modifications to the heat exchanger design. Factors such as fluid pressure, pressure drop, heat transfer rate, and type of fluid being processed all play a role in determining the appropriate type of heat exchanger for a particular process. Ultimately, heat exchangers provide an essential function in various industries by facilitating efficient heat transfer during industrial processes.