Transient 1D heat exchanger model for the simulation of domestic cooling cycles working with R600a

Abstract

Generally, domestic refrigerators and freezers are running in non-continuous operation mode most of the time, which is a necessity to match cooling capacity to thermal loads. In currently available domestic appliances this matching is realized either by on/off or variable frequency control of the hermetic compressor, leading to a repetitive and transient change of the system state. In case of longer compressor runtimes when cooling capacity demand is high (e.g. pull down cycles, initial operation) steady state operating conditions might be reached. The cycling transients cause losses in system efficiency, thus they should be reduced or avoided. To understand the complex transient physical processes and to optimize the cooling system efficiency, the use of numerical methods has turned out to be a promising approach. For this reason, a 1D heat exchanger model, which has been successfully implemented in a domestic cooling cycle simulation tool, is presented in this work. The heat exchanger model is a further development of the model being presented in Berger et al. (2012). The same mathematical framework is used for modeling the evaporator and condenser. In order to compute the void fraction, the pressure drop and the heat transfer in case of evaporation and condensation special empirical models, which are proposed in literature, have been implemented. Finally, the numerical predictions are compared to experimental data gained from a purpose-built test rig.

Transient cycle simulation of domestic appliances and experimental validation

“…The refrigerant temperatures are measured at the in-and outlet, the wall temperature is measured halfway between in-outlet. For more details about the heat exchanger model, its development and the challenging validation, the reader is referred to Berger et al (2012Berger et al ( , 2014Berger et al ( , 2015.…”