DETERMINATION OF DEPENDENCE BETWEEN THERMOPHYSICAL PROPERTIES AND STRUCTURAL-AND-PHASE CHARACTERISTICS OF MOIST MATERIALS

Abstract

Most of foods, raw materials and half-finished products are disperse systems. One of the most energy- consuming processes during foods production is drying. Intensive study of this process allows high-quality final products to be obtained at lower energy consumption. The aim of the research is to determine the interrelation between thermophysical properties and structural-and-phase characteristics of moist materials to establish optimum parameters for drying. A set of experiments has been made to find the influence of temperature on rheological properties of suspensions. A suspension of 40% chokeberry juice and ultradisperse starch from berry meal was used as the object of the research. Thermostatting was carried out in the range from 20 to 50 C with an increment of 10 C. The thermal conductivity coefficient for blocked samples with dimensions of 50 50 75 m-3 was determined by means of a continuous plate flat source. Samples were prepared using the plastiс mass forming method at the pressure of 50 MPa and the moisture of mass of 15%, and then dried. The results show that yield stress increases with temperature because of coagulation structuring intensification. The material has the highest thermal conductivity at the least capillary moisture of WLCM =14.2%, i.e. when a monomolecular layer of tightly bound water takes on the property of continuity through the material. The obtained results allow us to conclude that the use of volume phase characteristics makes it possible to improve the technique for determining thermophysical characteristics of dry and wet disperse systems to be improved, which in turn allows obtained results to be more accurate.

Keywords

• Granulation
• granules
• powder
• drying
• phase characteristics