DEVELOPMENT AND EVALUATION OF AN EQUIPMENT FOR MEASURING THERMAL CONDUCTIVITY OF TROPICAL FRUIT JUICES

Abstract

Fruits juices which is in a liquid form and primary source of vitamin C are nutritious, enjoyable and easy to consume are subjected to thermal treatment in food industry and understanding of their responses to these thermal processing required good knowledge of their thermal properties which serves as guide toward the design of equipment's for processing operations. The specific objectives of this research was to develop an equipment for measuring the thermal conductivity of tropical fruit juices, calibrate the equipment using known standard and fruit juices of known thermal conductivity and evaluate the thermal properties of selected tropical fruit juices. The equipment developed measures thermal conductivity of tropical fruit juices using line heat source method. Its was designed to maintain a constant temperature of 30, 40, 45, 50, 55, and 60o C of the sample chamber containing fruit juices. At the thermal equilibrium of the fruit juice, a constant electrical current of 2.5A was applied to the heater wire in the sample for heating and recording of temperature changes was carried out for the duration 20 minutes through logtag data logger. Mathematical formula designed by researchers were used to evaluate thermal conductivity, thermal diffusivity, specific heat capacity, and latent heat of fussion. The results obtained show that thermal conductivity and diffusivity increases with an increase in temperature for all the fruit juices as water melon having the highest value. The thermal properties values is also influenced with an increase in moisture content of the fruit juices. The fruit juices will required lot of energy to heat or cool due to the value of specific heat capacity and latent heat ranged between 3.45 – 4.06 kJkg-1 0C and 23785.5 – 31992.5 kJkg-1 respectively obtained and tagged as a poor conductor of heat.