Summary

This work presents a set of mathematical models for the dynamic simulation of household refrigerators. Models were developed for each one of the refrigerator components:  compressor, condenser, evaporator, cabinet and capillary tube —suction line heat exchanger. A semi-empirical modeling approach consisting of two sub-models, namely compression chamber and compressor shell, was  employed for the compressor. The  first considers  a polytropic compression process, once the last takes into account the internal heat exchanges and pressure losses. H ot gas cycle calorimeter tests were performed with a specially instrumented compressor in order to acquire the necessary  empirical parameters  for  the  compressor  model.  The  condenser,  evaporator  and  capillary  tube  — suction line heat exchanger models were based on the mass, momentum and energy conservation laws written in the  differential  form.  A  lumped  modeling  approach,  taking into  account  the inner liner,  the  steel  shell,  the thermal insulation, the door gasket and the internal radiative heat exchanges was employed for the cabinet. The models were solved numerically by successive substitution and a finite-volume procedure was used to integrate the correlating differential equations. Experiments were also performed with an all refrigerator in order to get a better understanding of the start-up and shut-down transient periods. The models potentialities are explored in the present work in terms of the spatial distribution of temperature, pressure and mass of the HFC-134a within each component of the refrigerator as a function of time.

Material for download