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Food & Beverage footprints, and cleaning difficulties. In addition to that, these traditional methods often require a large amount of energy, which increases the cost for food producers. Currently, multi-stage plate heat exchangers are extensively used for milk pasteurization, they are usually composed entirely of stainless steel, allowing high standards of hygiene.
Multi-stage plate heat exchanger Multi-stage plate heat exchanger is also a type of gasket plate heat exchanger. It can be used for heating and cooling two or more fluids, usually separated by intermediate frame, and can be manufactured into 2-stage, 3-stage, 4-stage, etc. The intermediate frame has connections for the circulation of media. Usually, the material of the intermediate frame is SS304 or SS316, since all the parts in contact with the medium should be made of stainless steel in order to avoid oxidation, cross-contamination and other pathologies of the heat exchanger. As for the gaskets, they can be made of NBRF, NBR-HTF, EPDMF, etc. Multi-stage plate heat exchangers include a multitude of advantages, such as:
• High heat exchange efficiency and low operating costs.
• Compact design, small footprint, easy to install.
• Easy maintenance, convenient disassembly for mechanical cleaning 。
• Easy expansion to add plates, increasing heat exchanging area 。
• Good turbulence effect, not prone to scaling.
Milk pasteurization process in multi-stage plate heat exchanger Step 1: Preheating( regeneration zone) Cold milk is first passed through the heat exchanger to receive thermal energy from the hot milk that has already been pasteurized, preheating it to a temperature close to the pasteurization temperature. As hot milk in the pasteurization cycle flows through the heat exchanger, it transfers heat to the incoming cold milk. This process reduces the amount of energy required to heat the milk to pasteurization temperature and is a key demonstration of the plate heat exchangers system’ s heat recovery capability. Technical details: The temperature difference between the hot fluid and the cold milk and the control of the flow rate are central to the optimization of thermal efficiency. Step 2: Pasteurization( heating zone) This is the critical stage for destroying harmful bacteria. At this point the milk is further heated to the required pasteurization temperature, usually 72 ° C for 15 seconds according to the High Temperature Short Time( HTST) method, to enter the sterilization phase. The heating medium, usually hot water or steam,
A multi-stage plate heat exchanger at HFM factory. Photo courtesy of HFM.
transfers heat through the other side of the heat exchanger plate for precise and uniform temperature control. Technical details: Ensure constant flow rate and uniform temperature distribution to prevent overheating or under-sterilization. Step 3: Insulation( insulated pipes) After reaching the target temperature, the milk needs to be maintained in the holding tube for a certain period( e. g. HTST at 72 ° C for 15 seconds) to ensure that there is enough heat to complete the sterilization process. Plate heat exchangers systems can also be used with heat recovery at this stage to improve energy efficiency. Technical details: Key variables include flow rate and duration within the holding zone to meet food safety requirements and ensuring that the pathogens will be killed. Step 4: Cooling( cooling zone) After sterilization, the milk must be rapidly cooled to below 4 ° C to inhibit microbial regeneration to ensure freshness and extend shelf life. At this point, the heat exchanger quickly reduces the temperature of the milk by means of a cooling medium( e. g. chilled water or other cooling medium). Technical details: Factors such as the temperature difference between the milk and the cooling liquid and the efficiency of heat transfer as well as the heat transfer capacity of the PHE directly influence the cooling rate.
Energy efficiency and sustainability advantages of multi-stage plate heat exchangers The multi-stage plate heat exchanger system significantly reduces the consumption of steam and hot water in the milk pasteurization process by efficiently recovering heat energy through the regeneration section, thus minimizing energy costs and improving overall economic efficiency. At the same time, the www. heat-exchanger-world. com Heat Exchanger World July 2025
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