螺旋折流片强化壳侧传热的四管模型数值模拟

针对螺旋折流片管壳式换热器的正方形布管方式,建立了相间套螺旋折流片的四管数学物理模型,利用FLUENT软件对该模型的流动与传热情况进行了数值模拟;并与光滑通道中及单管螺旋折流片模型的流动和传热结果进行了对比.结果显示旋向相反的相邻螺旋折流片所诱导的两股旋流通过相互作用可提高通道内流体流速,并有效地形成对相邻传热管外的斜向冲刷,这对于减薄边界层,促进近壁流体与主流区流体的动量和质量交换进而强化传热有明显的作用,算例显示其传热系数可比相同尺寸的光管通道中的情形提高约44%～57%.

NUMERIC SIMULATION OF HEAT TRANSFER ENHANCEMENT WITH FOUR-TUBE MODEL AT SHELL-SIDE OF COIL-STRIP-BAFFLE HEAT EXCHANGER

A four-tube mathematic-physical model with two coil-strip sleeved tubes and two bare ones oppositely placed at each corner of a square was established for quadrilateral tube arrangement in a coil-strip-baffled tube-shell heat exchanger. The flow fields and heat transfer characteristics in the channel outside of the four-tubes are simulated using FLUENT software, and compared with those in both bare tube channel and single coil-strip-baffle tube channel. The numerical simulation results show that the neighboring counter-wise strip-coil-baffles can induce coupled spiral vortex flows, which not only raise the velocity of the flow but also blow the adjacent tubes, thus diminish the boundary layers near the wall of both sleeved tubes and bare tubes, and promote momentum and mass exchange between flow particles near wall and in main stream. The results also show that the heat transfer coefficient at shell side of a tube-shell heat exchanger could be enhanced with this new structure up to the range of 44% to 57% in comparison with bare tube one.