Scientific and Technical Basis for the Development of an Induction Heating Unit for Milk Pasteurization

Abstract

Introduction. Induction heating is a preferred heating technique for industrial, medical and consumer systems, because it has a number of advantages over traditional heat transfer methods. The advantages include energy efficiency, heating rate, safety of operation, cleanliness of the process, low metal consumption, simple design, and precise control of the temperature of the heated raw materials. An induction heating unit is especially important for farms involved in processing of milk and producing milk-based products. Aim of the Study. The study is aimed at developing a prototype unit for long-term pasteurization of milk using a container heated by induction currents and at selecting optimal operating conditions for the developed prototype unit. Materials and Methods.There was used 3D modeling in the KOMPAS-3D computeraided design system to develop the main components of a milk pasteurization prototype unit with induction heating. The container for raw materials, stirrer and lid are made of stainless steel AISI 304 and AISI 430. The inductor is a frame made of polymer material with a litz wire arranged in a spiral manner. The body of the prototype unit is made of aluminum composite material. The developing and debugging of the electronic circuit of the prototype unit power part was carried out with the use of the design program Proteus 7.10. The microcontroller Mega 2560 was used to make the power part of the electromagnetic induction generation unit. The controlled temperature was monitored by using the waterproof temperature sensor DS18B20. A thermal imager was used to visualize the propagation of the thermal field over the surface of the container walls. Results. The structure diagram of the developed prototype unit with induction heating for long-term pasteurization of milk is presented. The article gives grounds to the use of the necessary elements and actuators in the unit for pasteurization of milk in a container heated by induction currents. There are presented a diagram of the developed power part for the prototype unit and the results of testing it when heating containers made of various materials. An algorithm has been developed to control the operation and PID regulation of the milk pasteurization in an experimental unit with the use the Raspberry Pi microcomputer. The graphs of transient processes when changing the coefficients of PID temperature control are presented. Discussion and Conclusion. When testing the induction heating principle on stainless steels of different compositions, it has been concluded that for the efficiency of heating the container, there is required a ferromagnetic steel pad welded on top of the main container made of food-grade stainless steel. The developed system of inductors made it possible to create a prototype unit with two heating zones depending on the volume of processed raw materials that is important for small farms engaged in processing milk and producing milk-based products.