Experimental Study Of Heat Transfer And Flow Resistance Characteristics Of High Prandtl Number Fluid In The 3-D Internally Crossing-finned Tubes

This paper carry out experimental study of the heat transfer and flow resistance characteristics of high Prandtl number fluid in 3-D internally crossing -finned tubes with cross-experiment design method.use oil as work media. Where Reynolds number ranged from 30 to 1000,Prandtl number from 600 to 4000. One of the results is the criterion of flow state in the 3-D internally crossing -finned tube. It shows that the flow in 3-D internally finned tubes can transform from laminar to transitive state with lower Reynolds number ,the conversional Reynolds number (under critical Reynolds number)Recr is correlated with the structures of the fin . Recr=3.3602(H/Di)-2.380 (Pt/H)-1.646 (B/Pt)-1.352 (S/B)-3.097which descends when H,B or Pt adds.Samely the conversional Reynolds number which show the flow transform from transitive state to turbulent state (up critical Renolds number) Reb is correlated with the structures of the fin too. Reb = 52.51(H / Di)-0.956 (Pt/H)-0.777 (B/Pt)-0.455 (S/B)-0.783 , which descends when H or Pt adds , oppositively when B reduces. The critical Reynolds number is small in the 3-D internally crossing -finned tube. Which is helpful for the engineering design to make the fluid flow in the turbulent zone and improve the heat transfer co-efficient .It shows that the 3-D internally crossing -finned tube is the superior tube for the high Prandtl fluid to enhance heat transfer.Regressed the experimental date with linear use minimal dual multiply method.Got the empirical equation of heat transfer and flow resistance in laminar,transitive and turbulent zone.Analysised the cross-experimental results and found the fittest way of various constructs to get the highest value of the thermal performance factor .Gave the theorith analysis of the mechanism of enhancement of heat transfer.And point out the optimize way of the fin.The conclusion of this paper offered the reference for latter study and engineering design.