Modelling and Simulation Heat Transfer in Wheat Stored in a Simulated Sealed Pit

Abstract

A mathematical model was developed to predict the change of temperature distribution with time in the radial and axial directions in a simulated sealed cylindrical pit. The finite difference method was used in the model to calculate the conductive heat transfer. The model predicts the grain temperatures in the pit during the storage period using input data of initial grain temperature, storage time and number of spatial elements in both radial and axial directions. Other input data include the finite difference spatial increment in both directions, the finite time increment, temperatures of soil surrounding the pit and the physical properties of grain, pit wall material and surrounding soil. To validate the model, predicted temperatures were compared with measured data for wheat of Apollo variety being stored in a simulated sealed pit for a period of 70 days. The wheat was stored in a cylindrical mild steel tank with 0.6 m in both diameter and height. The initial uniform grain temperature was 15°C and the initial uniform grain moisture content was 12.45% (w.b.). Both measured and predicted wheat temperatures attained steady state within a short period of storage (2 to 6 days) and this equilibrium was maintained throughout the experiment period. At the end of the storage period, the grain temperatures were decreased by an average of 2.63°C and the grain moisture contents were increased by an average of 1.62% (w.b.) at the top layer of the pit. For the bottom layer of the pit, the grain temperatures increased by an average of 7.04°C and the grain moisture contents were decreased by an average of 0.50% (w.b.) The conductive heat transfer model predicted the grain temperatures with a standard error of estimate between measured and predicted of 0.12°C -0.25°C.