Abstract

Drying food involves complex physical atmospheric mechanisms with non-linear relations from the air-food interactions, and those relations are strongly dependent on the moisture contents and the type of food. Such dependence makes it complex to design suitable dryers dedicated to a single drying process. To streamline the design of a novel compact food-drying machine, a heat pump dryer component design optimization algorithm was developed as a subprogram of a Computer Aided Engineering tool. The algorithm requires inputting food and air properties, the volume of the drying container, and the technical specifications of the heat pump off-the-shelf components. The heat required to dehumidify the food supplied by the heat exchange process from condenser to evaporator, and the compressor’s requirements (refrigerant mass flow rate and operating pressures) are then calculated. Compressors can then be selected based on the volume and type of food to be dried. The algorithm is shown via a flow chart to guide the user through three different stages: Changes in drying air properties, heat flow within dryer and product moisture content. Example results of how different compressors are selected for different types of produces and quantities (Agaricus blazei mushroom with three different moisture contents or fish from Thunnini tribe) conclude this article.

Highlights

  • Food drying is one of the strategies for food preservation, and one of several strategies is the thermal based mechanism, which is complex and involves the removal of a solid product’s moisture by the employment of heat

  • The algorithm can be represented in the form of a flow chart to illustrate the proposed logic map

  • The halting of the calculation process is given when the variation of the moisture content over time reaches almost zero, 1E-9. This criterion is flexible because it accommodates residual moisture differences from different types of food

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Summary

Introduction

Food drying is one of the strategies for food preservation, and one of several strategies is the thermal based mechanism, which is complex and involves the removal of a solid product’s moisture by the employment of heat. There are many different machines that can make this process, one of these is heat-pump based [1]. This heat pump based machine extracts energy via a gas compressor from a cold-source and delivers it to a hot-source. The heat-pump provides heat, making it directly useful for heating, ventilation and air conditioning (HVAC), and for drying applications. The machine energy input is the energy received from the compressor and that is added to the amount of energy removed from the cold-source, yielding a higher energy output as heat. For a compressor yielding 100 W to remove 400 W from a cold-source, Inventions 2019, 4, 63; doi:10.3390/inventions4040063 www.mdpi.com/journal/inventions

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