Numerical Simulation Of The Heat Exchange Tube Fitted With Conical Twisted-tape

The heat transfer enhancement of heat exchanger gets great improvement and development with the progress of industry. Series of novel heat exchanger with the characteristics of low energy consumption and high utilization will become the future direction of the research in the area of heat transfer enhancement.For present, the development of novel twisted-tapes at home and aboard are mainly focus on turbulent flow forced heat transfer in boundary layers. Even though these novel twisted-tapes improve the heat transfer factors of the tube to some extent, it may sometimes led to great pressure drop which bright more negative influence than profits which come from heat transfer enhancement. This article present a new low flow resistance conical twisted-tape insert based on core flow turbulence theory. Characteristics of heat transfer rate and flow resistance of turbulent flow in smooth pipe and bellows equipped with the conical twisted-tape inserts are investigated through numerical simulation method.Firstly, the conical twisted-tape with constant twist ratio(δ=3.0) and different four taper ratios (θ)(1:3.6,1:5, 1:7and 1:9) were investigated under Reynolds number(Re) ranges from 4000 to 14000 by using Fluent software and the results were also compared with typical plain twisted-tape insert. The results indicate that flow resistance is reduced considerably on basis of keeping turbulence intensity by using conical twisted-tape insert through temperature and pressure field analysis, and the overall thermo-hydraulic performance evaluation criteria is also considered.Secondly, the influence of taper ratios(θ) on the performance of heat transfer rate and flow resistance indicates that conical twisted tapes as taper ratio 1:5 has the best overall thermo-hydraulic performance and optimum matching between flow and flow resistance. This results are also showed that the contribution to heat transfer enhancement and flow resistance will be reversed if improving turbulent intensity continuously within the turbulent ranges. It will led to the tube’s energy consumption rise steeply without obviously improvement for heat transfer performance. Therefore, the turbulent intensity of disturbers have no-connection with its heat transfer performance, while the conical twisted-tape with the characteristic of core flow disturbance have a better heat transfer performance within the turbulent fluid flow ranges.Finally, Characteristics of heat transfer rate, flow resistance, and overall thermo-hydraulic performance of smooth pipe and bellows fitted with the conical twisted-tape with three twist ratios (δ)(2.0,4.4 and 6.0) and a constant taper ratio(θ=1:5) were investigated under same Reynolds number(Re) ranges. The effects of twist ratios to heat transfer rate and flow resistance were mainly investigated. The results show that both of tubes’ overall thermo-hydraulic performances are increased with the twist ratios reduction. Comparing with smooth pipe, the bellows equipped with all conical twisted tapes have a better heat transfer performance meanwhile the reason for this were also explained. The conclusion of paper indicates that the conical twisted-tape have an excellent performance in the area of compound heat transfer enhancement and providing a certain reference for heat exchanger new design or updating.