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Summary Absorption‐compression hybrid cooling systems with cascade condenser and cascade subcooler are able to effectively reduce compressor power by low‐grade heat. However, differences of both energy saving quantities still cannot be explained exactly through various types of coefficient of performance (COP) indicators, which is adverse for the decision‐making of appropriate layouts. In this regard, we attempt to illustrate the above‐mentioned issue from the new standpoint, that is, by decoupling processes and considering the limitation of thermodynamic cycles and refrigerant characteristics. It is found that there is the critical heat quantity corresponding to the order transition of energy saving for both layouts at first. Subsequently, critical heat quantities for different working conditions are obtained and analyzed. Moreover, expressions regarding critical heat quantities for five refrigerants are fitted by the neural network. It is displayed that the average difference between the critical heat quantity for R1234yf, R1234ze(E), R290 and R32 and that for ammonia is 7.89%, 4.08%, 4.78%, and 4%, respectively. The paper is helpful for decision‐making of absorption‐compression hybrid cooling systems with cascade condenser and cascade subcooler to enhance the amount of energy saving for certain quantities of low‐grade heat.

Solar-assisted hybrid cooling systems are promising for the energy saving of refrigeration systems. In most cases, the solar thermal gain is only able to power the heat-driven process of facilities during part of the working period. Therefore, the reduction of compressor power strongly depends upon the duration of heat-driven processes, which has not been addressed properly. Motivated by such a knowledge gap, the thermodynamic understanding of solar-assisted hybrid cooling systems is deepened through considering the duration in heat-driven processes. Three absorption–compression-integrated cooling cycles were taken as examples. It was found that optimal parameters, e.g., inter-stage pressure and temperature, corresponding to various performance indicators tend to be identical, as the duration of heat-driven processes is taken into account. Furthermore, the optimal parameter for different working conditions was obtained. The dimensionless optimal intermediate temperature of layout with the cascade condensation process varies slightly, e.g., 4%, for different conditions. Moreover, the fall of compressor power in the entire working period was nearly independent upon the intermediate temperature. The paper is favorable for the efficient design and operation of solar-assisted hybrid cooling systems.

Droplet spread over a vertically falling liquid film is studied in this paper. A simulation model is built and verified by experiment. Following this, a unique phenomenon that emerges in this context, namely, a strong inertial oscillation in an early stage of spreading, is analyzed. Finally, the equilibrium features of an oil droplet in this circumstance are discussed. The results show that the maximum spreading length in a strong inertial oscillation is much longer than the equilibrium length, being 152% the length of the latter in the base case. Furthermore, the equilibrium spreading length increases nearly linearly with the initial diameter of the droplet. The paper provides data to understand the effects of an oil droplet on a vertically falling film absorber to promote energy saving in a cold storage refrigeration system with low-grade heat.

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