Numerical and experimental study of the transient behavior of a domestic vapor compression refrigeration system – Influence of refrigerant charge and ambient temperature

Thermodynamic Irreversibility Analysis of Dual-Skin Chest-Freezer

“…The mathematical model employed in the simulations performed in this work is the capacitive model developed in [9,12,13]. In summary, this model is composed of sub-models for each main system component (compressor, condenser, capillary tube, evaporator, and cabinet compartment).…”

“…These equations consists, mainly, on mass and energy conservation laws and heat transfer rates that allow the computation of: component temperatures, fluid evaporation and condensation pressures and their corresponding temperatures, refrigerant mass distribution in the main components, and the degrees of sub-cooling and superheating. The system performance parameters are also computed, including the system coefficient of performance (COP), cooling capacity, consumed compressor electric power, mean consumed energy, and others, for example, see [13].…”

“…This previous model was properly modified for performing the calculation of component and system transient entropy generation and exergy destruction rates (thermodynamic irreversibilities), as well as the second law efficiency. The modifications performed in the present model in relation to the previous one from [9,12,13] consist of: (i) the calculation of the suction mass flow rate when the compressor is turned off. This mass flow rate is now used in compressor, condenser, and evaporator sub-models; (ii) the calculation of the flashing heat transfer rate in the condenser when the compressor is turned off; (iii) the transient calculations of the entropy generation and exergy destruction rates and of the transient entropy variations.…”

“…The adopted procedure for implementing these equations is presented in Section 3. The original capacitive model from [9,12,13] is denominated as "model A". The proposed modified model is called "model B".…”

“…All models encountered in the literature review uses the integrative control volume approach for the system, including the one developed in this work, which can be justified by the fact that vapor compression cycles (VCS) are complex systems. In the present work, the lumped control volume approach published in [9,12,13] is extended by the proposition of very detailed procedures for calculating the temporal entropy generation and exergy destruction rates of the refrigeration system and its components.…”