Development of Solar Accumulating Drying Equipment Based on the Theoretical Studies of Solar Energy Accumulation

Abstract

The process of heating a dewatered object in an infrared solar drying plant (with paraffin on the bottom) with solar energy storage is considered. To solve this problem, it is assumed that the heat capacity of paraffin exceeds the heat capacity of the dehydrated object. Infrared rays fall on the upper layer, and heat exchange takes place due to heat and mass transfer with the surface air located between the metal plate and the object to be dehydrated. The equations of thermal conductivity for a dewatered object are given, its relationship at the phase interface is determined using the equality of temperature and heat flow. For an exposure of overheating with a period of 6.5 h, the time of passage of the phase boundary in accordance with the law of motion of the spreading (hardening), was determined according to the formula of ξ = α √6,5 h ≅ 12 h.The optimal thickness of the accumulating paraffin layer was ascertained. On the basis of the theoretical studies, experiments were conducted to study the temperature field of various heataccumulating materials in the laboratory of Tashkent State Technical University. It was found that of all heat-accumulating materials, paraffin has the best heat retention ability when its thickness is of 2–4 cm. The optimal variant of a solar accumulator drying plant with a heat accumulator, viz. paraffin has been designed. In particular, 2–4 cm of paraffin layer with a mass of 50 kg with a corresponding flat surface in terms of specific heat of evaporation is 2400 kJ/kg. The specific melting value of paraffin (150 kJ/kg) allows additional evaporation of 5.8 l of moisture when drying objects. The proposed solar accumulator drying plant can be used for dehydration of medicinal herbs.

Keywords

• solar accumulating drying equipment
• thermal conductivity
• temperature
• paraffin
• solar collector