Testing of an industrial capacity laboratory condensation dryer

Drying is one of the most important preservation methods in the food processing industry. The complete or partial extraction of water from biological materials is an extremely complex process that consumes a large amount of energy. The drying regime that will be applied for any specific case is determined by several influencing factors such as the дуратион of the drying process, the product quality, the dried biological material thermal sensitivity, etc. Traditional methods of agricultural products drying and consumption of a large amount of energy in conventional dryers significantly lowers the final product quality and increases its final price. Applying alternative technologies in the drying process is the focus of many projects. Research in the field of drying systems that is focused on solving these problems is quite justified. In conventional dryers the air is heated to the drying temperature by electric heaters or heat exchangers, which intensifies the exchange of heat and matter. In condensation dryers combined with a heat pump, a significant amount of energy can be saved by keeping the latent and sensible heat of the product within the chamber. Condensation dryers operate as heat exchangers using both high and low temperature sources of a heat pump. These dryers reach slightly lower temperatures, up to 60ºC, and are suitable for drying chopped fruits and vegetables, as well as herbs. The drying quality in such dryers is exceptional, although somewhat slower than in conventional dryers. This paper presents the test results of drying carrots, as a representative of root vegetables. Laboratory condensation dryer with 100kg capacity was used, a product of the company NIGOS - Niš. The incentive for this research lies in the fact that this method of drying has numerous advantages: high quality of the material is maintained in terms of color, taste, smell, nutritional value, etc.; electricity consumption is 3-5 times lower; achieving very low humidity is possible; there is a high degree of automation of the process; high hygiene of the product (in accordance with the HASAP standard); there is no air exchange in the closed system, and the product is not covered with dust; the design is efficient and the use and maintenance is simple. In addition, the closed system allows it to work indoors and outdoors, since it does not discharge steam (like an open system) but condensate, so it does not humidify the premises. A detailed schematic of the dryer is presented. All components, corresponding dimensions and a description of its operation are presented. Drying, in this experimental research, was carried out according to the manufacturer's pre-defined regimes. The temperature and relative humidity of the drying agent (air) are defined by the technology requirements of drying. They are fully monitored and maintained at the desired level, according to a predetermined program. With this dryer, there is the possibility of monitoring the dryer efficiency when the process is guided by the pre-set desired drying curve. The drying process is fully automated. As result of the experimental research, a product with a final moisture content of 4% was obtained, which fits the recommended literature data for this type of vegetable.