| Defrosting of evaporators is necessary for the operation of air source heat pumps and refrigeration systems operating at air temperature below the water freezing point. Optimization of defrosting process is required for improving the performance of evaporators and systems. In this work, a hot gas defrosting model of evaporators was developed. The defrosting process was idealized for analysis and simulation, which included heat transfer, mass transfer and pressure change. This model divided the defrosting process into four stages: preheating, melting frost, wet surface, and dry surface, based on evaporator outside surface conditions. This model treated a transient dynamic defrosting process as a two dimensional process involving time and space. Continuous change of refrigerant properties inside the evaporator was considered. The analysis concentrated on the required energy and time for defrosting.;A computer program written using FORTRAN was developed to perform the simulation of defrosting process of evaporators. (Abstract shortened by UMI.)... |
