Heat Transfer Characteristics And Flow Behaviors Of The Spiral Plate Heat Exchanger

An investigation has been performed to clarify the heat transfer characteristicsand flow behaviors of the spiral plate heat exchange with the non-circular pin fins, inwhich experimental study and numerical simulation are involved.Experiments have been performed, in which the heat-mass transfer analogy andthe naphthalene sublimation technique are employed, to investigate the heat transferand flow characteristics of the circular pin fin and elliptic pin fins with different axisratio in the spiral channel. The testing fluid was air and the Reynolds number rangedfrom about 2000 to 30000. The empirical equations of heat transfer (Nusselt number)and resistance (Euler number) for different elliptic pin fins are presented in the paper.The convective heat transfer coefficient around the bottom of the spiral channel is alsostudied. Overall capability of the spiral channel with different elliptic pin fins and acircular pin fin is compared each other. The experimental results can be concluded asfollowing: a) the convective heat transfer coefficients of the cylindrical surface of theelliptic pin fins are higher than that of a circular pin fin with Re＞7500 and the trendturns into more significant with the increase of a/b; b) the convective heat transfercoefficients of the bottom of the spiral channel with elliptic pin fins are lower than thatof circular pin fins with Re＞7500;c) the general convective heat transfer coefficients ofthe spiral channel vary slightly with the change of pin shape with Re＜7500, the generalconvective heat transfer coefficients of the spiral channel with elliptic pin fins arelower than that of circular pin fins with Re＞7500; d) the hydraulic drag coefficients ofelliptic pin fins are lower than those of a circular pin fins and the trend turns into moresignificant with the increase of a/b; e) among the spiral plate heat exchanger withdifferent type pin fins compared, the overall capability number k of the spiral plate heat exchanger with a/b=2.0 elliptic pin fin is the highest and increases with Re.In the part of computer calculation, it is carried out by virtue of ComputationalFluid Dynamics (CFD) software. An investigation has been performed to analyze theheat transfer characteristics and flow behaviors in the spiral channel with staggeredarrays of circle-shaped, ellipse-shaped, cube-shaped and diamond-shaped pin fins.Overall capability of the spiral channel with different non-circular pin fins and acircular pin fin is compared each other. The numerical simulation results can beconcluded as following: a) Overall capability of the spiral channel with elliptic pin finsof crossflow major axis with triangle arrangement is higher than that of circular pinfins and the overall capability number k of a/b=2.0～2.5 elliptic pin fin is the highest; b)Overall capability of the spiral channel with elliptic pin fins of crossflow major axiswith triangle arrangement is higher than that of square arrangement; c) Overallcapability of the spiral channel with elliptic pin fins of crossflow major axis is higherthan that of crossflow minor axis; d) Overall capability of the spiral channel withcube-shaped and diamond-shaped pin fins is lower than that of circular pin fins withthe same arrangement way.As a result, overall capability of heat transfer and flow of the spiral plate heatexchanger with elliptic pin fins superior to that of circular pin fins,and the overallcapability number k of a/b=2.0～2.5 elliptic pin fins spiral channel is the highest.