Flow boiling heat transfer and dryout characteristics of R152a in a vertical mini-channel

• Boiling heat transfer and dry-out characteristics of R152a in a vertical mini-channel.
• HTCs increased with increasing heat flux and operating pressure.
• HTCs remained unaffected with varying mass flux and quality.
• Identical boiling heat transfer results with R134a.
• Dryout heat flux remained unaffected with varying saturation temperature.

This article reports on flow boiling heat transfer and dryout characteristics of R152a in a vertical mini-channel. The experiments were carried out with a resistively heated stainless steel tube (1.60 mm in diameter and 245 mm heated length) at 27 and 32 °C saturation temperature. Five mass fluxes in the range 100–500 kg/m2 s with heat fluxes from 5 to 245 kW/m2 were tested. Under similar operating conditions experiments were repeated with R134a in the same setup to compare thermal performance of R152a. The results showed that the heat transfer was strongly influenced by the applied heat flux with insignificant convective contributions. The dryout heat flux increased with increasing mass flux but no effect of varying operating pressure was noticed. The experimental results for heat transfer and dryout heat flux were compared with well-known macro and micro-scale correlations from the literature.