Conference Year

2016

Keywords

CFD, cold storage chamber, heat mass transfer, vegetables

Abstract

During storage of fruits and vegetables in cold stores, quantitative as well as qualitative losses may occur due to non-uniformity of storage conditions. The macroscopic energy balance, mainly used to design storage chambers, cannot predict where storage conditions are going to induce the loss of commodity. The numerical modelling of the cold storage can be applied as an effective tool to investigate the  homogeneity of the treatments to which the produce is subjected. The most important factors affected the uniformity of temperature and relative humidity, and consequently, the quality of the commodity, are velocity, temperature and humidity of air from the cooling unit, load arrangements and physical properties of vegetables and fruit. The work and performance of cooling unit depends on the working conditions and should be analyzed together with the chamber and its load as one computational task, but a distinctive feature of the storage chamber is a great variation in sizes of objects making its geometry. There are large empty spaces in the chamber, filled only with humid air, as opposed to very large areas occupied by huge number of small objects (pieces of produce in boxes or palloxes and coils of a heat exchanger in the cooling unit). It is impossible to maintain, in a geometric model of the cold store, the shape of all its relatively small details. This is the reason for use of porous media model in modelling of the air flow through the bulk of produce and the cooler. The numerical model and results of calculations of heat and mass transfer in a Chinese cabbage cold storage chamber are presented in the paper. The main feature of the model is the connection between phenomena  occurring in the bulk of vegetables and in the heat exchanger of cooling unit accomplished via user defined functions UDF. The model relates cooling capacity to the transpiration and respiration in the bed of cabbage. The thermal non-equilibrium model of heat transfer in porous media was applied both to the bed of vegetables and to the heat exchanger of the cooler. The heat and mass transfer coefficients in the bed of cabbage and in the cooler were treated as field quantities. The results of calculations were applied to the preparations of experimental evaluation of heat and mass transfer in the real cold store.

Share

COinS