Study of saturated pool boiling heat transfer characteristics of R1233zd(E) on Aluminum-based micro-pin finned surfaces

With the continuous development of chip integration and information technology, the heat dissipation has become a major limitation on the performance of electronic devices such as 5 G base stations, data centers and so on, and meanwhile a challenge of conventional single-phase convection cooling methods. Boiling shows prospective in high heat flux cooling and energy saving due to the utilization of latent heat. R1233zd(E), an environmentally friendly refrigerant (GWP=1, ODP=0) with a freezing point of-107 degrees C, is a potential working fluid in phase-change heat sinks for geographical applications. Nevertheless, the poor boiling performance of R1233zd(E) on plain surface due to the limitations in thermophysical properties must be enhanced. Moreover, conventional heat sinks are mostly copper-based, which makes them inconvenient for transportation and installation, and costly for production as well. In this work, micro-pin fins in the range of 100 - 500 mu m are fabricated on the aluminum surface to enhance the pool boiling of R1233zd(E). Moreover, the influence of their size and saturation pressure on the bubble behavior, critical heat flux (CHF) and heat transfer coefficient (HTC) is experimentally and theoretically investigated. The results show that the increase of pressure, as well as the ensuing various nucleation sites and capillary effect to rewet the evaporation region, can lead to an increase in the CHF and HTC. Notably, the 150 - 200 mu m micro pin-finned surfaces reach the highest CHF and 100 mu m one owns the highest HTC, which is 214 % and 383 % higher than that of plain surface, respectively. By considering the balance of capillary effect and bubble convolution effect, a model of CHF is proposed to reveal the mechanism of the optimum size of the micro pin fins. The predicted CHFs have an inaccuracy of less than +/- 20 % compared to experimental values. This paper makes up for the lack of basic experimental data on pool boiling of R1233zd(E) on aluminum surface, which thus provides guidance for the design of phase-change heat sinks such as thermosyphons, 3D vapor chamber (3D-VC) and microchannels.