单螺旋和双螺旋折流板换热器性能的研究

为了研究双螺旋结构对螺旋折流板换热器性能的影响及其与单螺旋结构的比较,利用热态试验和数值模拟方法,研究了四分之一扇形和三分之一扇形螺旋折流板换热器单、双螺旋结构的壳程传热和阻力性能.热态试验结果表明,单、双螺旋结构的壳程传热系数和压力损失均随流量的增大而提高.在相同流量下,双螺旋结构的壳程传热系数高于单螺旋结构,同时其壳程压力损失也有所增大.但随着流量的增加,双螺旋结构对应的单位压降下的传热性能与单螺旋基本一致.这说明双螺旋结构可以提高壳程传热性能,同时不会影响换热器的综合性能.因此在流体输送动力允许的条件下,双螺旋结构有利于设备处理能力的提高.数值模拟结果表明,由于折流板数量是单螺旋结构的两倍,因此双螺旋结构对壳程流体具有更强的导流作用,流体的分布更加均匀,且呈现出更加强烈的旋转运动.

Performance of Heat Exchangers with Single-Helical and Double-Helical Baffles

The effects of baffle constructions on the shell-side performances of heat exchanger with double-helical baffles were investigated,and the comparison of above performances with that of heat exchanger with single-helical baffles were conducted.The shell-side heat transfer and flow resistance performances of heat exchangers with single-and double-helical baffles consisted of 1/3 sectors and 1/4 sectors separately were studied experimentally and by numerical simulation,respectively.The experimental results show that both the shell-side heat transfer coefficients and pressure drops in the heat exchangers with single-and double-helical baffles increase with the increase of the shell-side flow rate,and under the same shell-side flow rate,both the shell-side heat transfer coefficients and pressure drops in the heat exchangers with double-helical baffles are higher than that of heat exchanger with single-helical baffles.But accompanying the increase of the shell-side flow rate,the shell-side combination property(the heat transfer coefficient per unit pressure drop)of the heat exchanger with double-helical baffles accords with that of the heat exchanger with single-helical baffles.It indicates that the double-helix structure could enhance the shell-side heat transfer performance of the heat exchanger and does not reduce its combination property at the same time.Therefore the double-helix structure is favorable to enhance the processing ability of the heat exchanger if the fluid transmission power allows.The numerical simulation results show that,since in the same heat exchanger shell-side,the baffle numbers of the double-helix structure is twice the baffle numbers of the single-helix structure,the double-helix structure has stronger guiding effect,which causes the fluid flow in the shell-side to distribute more uniformly and have strongly rotating movement.