The thermal transmission coefficient for a micro-ribbed tube has been determined using theoretical relationships and the outcomes of such calculations have compared with experiments conducted R1234yf refrigerant undergoing condensation. In particular four single-phase flow three multi-phase models used in this regard. experimental results show that: Oliver et al. criterion equation overestimate...

An increase in global warming potential and other environmental concerns are demanding new environmentally friendly refrigerants. For effective performance of refrigeration air conditioning system condenser design play a vital role. Experiments were conducted to study the condensation R1234yf refrigerant inside copper tube 8.4 mm diameter 750 length. The heat transfer coefficients calculated ag...

Abstract The performance of a dual evaporator cycle using ejector is compared with conventional employing pressure reducing valve. In both the systems, high temperature considered as flooded evaporator, thus separator employed after evaporator. However, low kind dry comparison i.e., and assisted, done for same cooling capacities dryness fraction at exit R134a, R152a, R1234yf refrigerants. effec...

This paper presents the results of experimental research and mathematical modelling in terms influence periodic dynamic instabilities have on condensation phase change R1234yf R1234ze refrigerants tubular minichannels. The main reason for this was fact that under Montreal Protocol (1986), as well Regulation No 517/2014 European Parliament Council 16 April 2014, F-gases such hydrofluorocarbons (...

Flow boiling of refrigerants in narrow channels has a great potential to cope with future challenges the thermal management high heat flux electronics. This study investigated flow transfer R1234yf, R1234ze(E), and R134a multi-microchannels as applied was varied from incipience critical flux. A parametric analysis on two-phase local coefficients conducted for channel mass fluxes 415 kg/m2s 1153...

The potential use of many common hydrofluorocarbons and hydrocarbons as well as new hydrofluoroolefins, i.e. R1234yf and R1234ze(E) working fluids for a combined organic Rankine cycle and vapor compression refrigeration (ORC-VCR) system activated by low-grade thermal energy is evaluated. The basic ORC operates between 80 and 40 °C typical for low-grade thermal energy power plants while the basi...