Experimental investigation of R-245fa flow boiling in minichannels at high saturation temperatures: Flow patterns and flow pattern maps

Flow boiling heat transfer in minichannels at high saturation temperatures: Part I – Experimental investigation and analysis of the heat transfer mechanisms

“…The Virtual Institute aims to offer a platform through which experimental data sets shared and new experimental techniques discussed. Flow patterns were identified using the flow pattern maps developed by [6,7]. In the upcoming flow pattern maps, the transition between intermittent flow (I) and annular flow (A) is indicated by a black line.…”

“…The contribution to the overall heat transfer of a variety of mechanisms was identified and discussed for medium and high saturation temperatures. According to the results of [7], at 60°C, the heat transfer coefficient is independent of vapor quality and mass flux during intermittent flow whereas it is sensitive to heat flux. In annular flow, the heat transfer coefficient increases with increasing vapor quality and/or mass velocity.…”

Thermal Energy Processes in Direct Steam Generation Solar Systems: Boiling, Condensation and Energy Storage – A Review

“…Hence, the liquid phase velocity increases, while the vapour phase velocity reduces (the slip ratio drops). Moreover, the surface tension increases and the gravity starts to play a less significant role in shaping the particular flow pattern (Charnay et al, 2014). None of the proposed correlations address these issues.…”

“…A first perspective on the reasons why the existing correlations (two-phase heat transfer or pressure drop) cannot be reliably extrapolated to water/steam applications is because they are developed for refrigerant flow boiling with a relatively low saturation temperature. As reported by Charnay et al (2014), the research on two-phase flow boiling of refrigerants mainly focuses on saturation temperatures between −20 • C and 40 • C. Most of these values correspond to reduced pressures between 0.05 and 0.5. The critical pressures of common refrigerants vary between approximately 35 and 70 bar.…”

Flow boiling heat transfer in minichannels at high saturation temperatures: Part II – Assessment of predictive methods and impact of flow regimes

“…The mass velocity ranged from 100 to 1500 kg/m 2 Á s, the heat flux varied from 10 to 90 kW/m 2 , the inlet vapor quality from 0 to 1 and the saturation temperature from 60 to 120°C. Flow patterns were identified using the flow pattern maps developed by [3].…”