Pressure loss and performance assessment of horizontal spiral coil inserted pipes during forced convective evaporation of R-600a

The impacts of spiral coil inserts on the pressure loss of environment-friendly refrigerant R-600a are experimentally evaluated during forced convective evaporation within horizontal copper pipes. Then, by considering the current pressure drop and previous heat transfer results and calculating the performance factor, the overall effectiveness of the inserts is determined. Experiments are carried out for smooth and rough tubes. Five spiral coils with various coil pitches and wire diameters are utilized. Also, vapor qualities between 0.08-0.7 and mass fluxes between 109.2-505 kgm-2s-1 are considered for tests. Generally, it is observed that inserts augment the pressure loss in the range of 90-958% over the smooth pipe. However, as the wire diameter decreases and the coil pitch increases, less pressure losses are imposed to the system. Depending on the operational conditions and inserts type, the performance factor was obtained between 0.13-1.40. The coiled wire “CW5” with the wire diameter of 1 mm and coil pitch of 30 mm performed superior compared to the other inserts by maximum performance factor of 1.4. Finally, by using the current data a new correlation is proposed in order to predict the evaporative pressure loss of R-600a within spiral coil inserted pipes.