Heat transfer augmentation in a circular tube with perforated double counter twisted tape inserts. (May 2016)

• Record Type: Journal Article
• Authors: Bhuiya, M.M.K.; Azad, A.K.; Chowdhury, M.S.U.; Saha, M.
• Is Part Of: International communications in heat and mass transfer. Volume 74(2016:May)
• Page Start: 18
• Page End: 26
• Publication Date: 2016-05
• Subjects: Perforated double counter twisted tape insert -- Porosity -- Nusselt number -- Friction factor -- Thermal enhancement efficiency; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Heat -- Transmission; Mass transfer; Periodicals; 621.4022
• DOI: 10.1016/j.icheatmasstransfer.2016.03.001
• Languages: English
• ISSNs: 0735-1933

Abstract

Abstract: The present study explored the effects of perforated double counter twisted tapes on heat transfer and fluid friction characteristics in a heat exchanger tube. The twisted tapes with four different porosities of R p = 1.2, 4.6, 10.4 and 18.6% were used as counter-swirl flow generators in the test section. The experiments were conducted in a circular tube in turbulent flow regime with Reynolds number ranging from 7200 to 50, 000 using air as the working fluid under uniform wall heat flux boundary condition. The experimental results demonstrated that the Nusselt number, friction factor and thermal enhancement efficiency were increased with decreasing porosity except porosity of 1.2%. The results also revealed that the heat transfer rate of the tube fitted with tapes were significantly increased with corresponding increase in friction factor. In the range of the present investigation, heat transfer rate and friction factor were obtained to be around 80 to 290% and 111 to 335% higher than those of the plain tube values, respectively. Based on constant blower power, the highest thermal enhancement efficiency of 1.44 was achieved. In addition, the empirical correlations of Nusselt number, friction factor and thermal enhancement efficiency were developed based on the experimental data.