Study On Strengthened Shell Side Heat Of Twisted Oval Tubes Heat Exchanger

Tube-shell heat exchanger with twisted oval tubes has good heat transfer performance.Most of the research on the shell and tube heat exchangers mainly focus on the tube arrangements with the oval-tube bundles twisting in the same direction.There are no studies about the influence of the twisting directions between the adjacent tubes on the thermal performance of the shell and tube heat exchanger.The fluid between adjacent twisted tubes with opposite twisting directions flows in the same direction under the inducement of twisted tubes,which is helpful to improve the flow of shell side fluid and promote the mixing of cold and hot fluids at shell side,thus improving the heat transfer performance of the heat exchanger.Therefore,it is of great significance to study the influence of the twisting directions on the thermal performance of the shell and tube heat exchanger in order to further improve the performance of heat exchangers.In this paper,the influence of the twisting directions of twisted oval tubes on the thermal performance of the shell and tube heat exchanger is studied by numerical simulation.Under the condition of constant twisted pitch length P and aspect ratio B/A,the effects of the reverse torsion arrangement and the same torsion arrangement on velocity,temperature,friction factor and heat transfer are analyzed,and different tube bundle arrangements are compared under the overall performance factor.The results show that the layout with counter twisting directions between the adjacent tubes has a significant effect on the flow and heat transfer in the shell side channel of the heat exchanger,and the optimal twisted pitch length and aspect ratio make the heat transfer performance of the heat exchanger better.Under the condition of constant twisted pitch length,when the aspect ratio B/A = 0.45,the heat transfer performance of reverse torsion arrangement is the best.At B/A = 0.37,the maximum differences of the Nusselt number Nu and overall performance factor h/?P^(1/3)under different tube bundle arrangement are about 9.23% and 11.16%,respectively.At B/A = 0.45,the maximum differences of the Nusselt number Nu and overall performance factor h/?P^(1/3)under different tube bundle arrangement are about 17.88% and 14.73%,respectively.At B/A = 0.55,the maximum differences of the Nusselt number Nu and overall performance factor h/?P^(1/3)under different tube bundle arrangement are about 10.81% and 7.96%,respectively.At B/A = 0.71,the maximum differences of the Nusselt number Nu and overall performance factor h/?P^(1/3)under different tube bundle arrangement are about 1.18% and 1.12%,respectively.When the aspect ratio B/A is constant at 0.45,the twisted pitch length P is 50 mm,the heat transfer performance of reverse torsion arrangement is the best.At P=50,the maximum differences of the Nusselt number Nu and overall performance factor h/?P^(1/3)under different tube bundle arrangement are about 17.88% and 14.73%,respectively.At P=60,the maximum differences of the Nusselt number Nu and overall performance factor h/?P^(1/3)under different tube bundle arrangement are about 5.58% and 6.66%,respectively.At P=80,the maximum differences of the Nusselt number Nu and overall performance factor h/?P^(1/3)under different tube bundle arrangement are about 3.9% and 5.37%,respectively.At P=100,the maximum differences of the Nusselt number Nu and overall performance factor h/?P^(1/3)under different tube bundle arrangement are about 1.71% and 4.42%,respectively.