Paper deals with theoretical analysis of possible efficiency increase of compression refrigeration cycles by means of application of a twophase ejector. Application of the two phase ejector in subcritical refrigeration system as a booster compressor is discussed in the paper. Results of exergy analysis of the system operating with various working fluids for various operating conditions have been shown. Analysis showed possible exergy efficiency increase of refrigeration compression cycle.

The theoretical basis for the indirect measurement approach of mean heat transfer coefficient for the packed bed based on the modified single blow technique was presented and discussed in the paper. The methodology of this measurement approach dedicated to the matrix of the rotating regenerative gas heater was discussed in detail. The testing stand consisted of a dedicated experimental tunnel with auxiliary equipment and a measurement system are presented. Selected experimental results are presented and discussed for selected types of matrices of regenerative air preheaters for the wide range of Reynolds number of gas. The agreement between the theoretically predicted and measured temperature profiles was demonstrated. The exemplary dimensionless relationships between Colburn heat transfer factor, Darcy flow resistance factor and Reynolds number were presented for the investigated matrices of the regenerative gas heater.

To boost the efficacy of a refrigeration system, researchers have imported nanoparticles into refrigerants in recent years. This paper comprehensively reviewed the properties, heat transfer performance, and system performance of nano-added refriger-ants in recent years. This article likewise assists with recognizing the gap in past research works and explores the possibilities for additional work. Refrigerant R134a charged with the nanoparticles TiO2 has the highest value of coefficient of perfor-mance which is 63.5% higher than that of Al2O3 nanoparticle charged R134a. Charging of the nano-refrigerants has enhanced the heat transfer performance of vapour compression refrigeration systems, particularly in the pool and nucleate boiling heat transfer. The heat transfer coefficient of R134a-based nano-refrigerant is enhanced by 42% and 30.2% with CuO and TiO2 nanoparticles respectively. The inclusions of nanomaterials, concerning their physical phenomena, influencing the vapour compression refrigeration system are confined in this paper