Study on heat and mass transfer of sugarcane stem during vacuum pre-cooling

Abstract

Abstract Heat and mass transfer of fruit and vegetables is significantly affected by vacuum pre-cooling end temperature (VPET). The simulations and experiments on the heat and mass transfer of sugarcane stem were performed to investigate the trends of total system pressure, temperature distribution, the water evaporation rate, weight loss, and thermal conductivity versus time during vacuum pre-cooling. A cylindrical model of heat and mass transfer of sugarcane stem was established, taking the transient heat transfer and mass conservation into consideration. Based on mass and energy conservation, the governing equations for water involved were coupled. What is more, the respiratory heat was regarded as the internal heat source. The finite volume method (FVM) was employed to precisely derive differential equations. The results of the numerical simulation and experiments showed that the maximum deviation of mean temperature between simulation and experiment was less than 2.6 °C. The maximum weight error between the simulation results and the experimental data was less than 2%, while the error of weight loss was 16.35%. The thermal conductivity in the radial direction of the sugarcane stem was lower than that of the axial direction. Compared with the simulation process, the two peaks of water evaporation rate in the experiment were caused by the change in relative humidity. The maximum errors in simulation and experiment operation for water evaporation rate and relative humidity were below 25% and 8.4%, respectively. The results implied that simulation results were consonant with the data obtained in the experiment. The reliably cylindrical model can be taken as an ideal reference for simulation research of other processes in the vacuum pre-cooling.