Thermohydraulic performance evaluation of heat exchangers equipped with centrally perforated twisted tape: Laminar and turbulent flows

Abstract

Convective heat transfer enhancement in a round tube mounted with a centrally perforated twisted tape (CP-TT) was numerically investigated. Influences of space of cut ratio (s/w = 0.5, 0.7 and 0.9) and twist ratio (y/w = 2.0, 3.0 and 4.0) under laminar and turbulent flow regimes on heat transfer characteristics were determined. Numerical encompassed Reynolds numbers (Re) from 400 to 2000 for laminar flow and 5000 to 15,000 for turbulent flow. At a given Reynolds number, the tubes with centrally perforated twisted tape (CP-TT) inserts offer higher heat transfer rate than those the plain tube alone. Heat transfer enhancement in a round tube equipped with centrally perforated twisted tape (CP-TT) is strongly dependent on twist ratio (y/w) and space of cut ratio (s/w). The results also found that the heat transfer rate (Nu) and friction factor (f) increase as twist ratio (y/w) and space of cut ratio (s/w) decreases. The thermal enhancement factor () increases as space of cut ratio (s/w) and twist ratio (y/w) decreases in laminar flow regime while the opposite trend is observed in the turbulent flow regime. Over the studied range, the tube equipped with centrally perforated twisted tape (CP-TT) with s/w = 0.5 and y/w = 2.0 gives the maximum thermal enhancement factor () of 8.92 for laminar flow at Re = 2000. In turbulent flow at Re = 5000, the centrally perforated twisted tape (CP-TT) with s/w = 0.9 and y/w = 3.0 yields the maximum thermal enhancement factor () of 1.33. In addition, the flow structure, temperature field and local Nusselt number of heat exchanger tubes equipped with centrally perforated twisted tape (CP-TT) are also reported for the clarification of heat transfer and flow topology mechanisms.

Parametric study on the heat transfer characteristics in a circular tube with helical tape insert under laminar flow conditions

“…1,4 Uses of multiple tapes inside the circular duct, perforated twisted tapes, notched tapes, spaced twisted tapes, v-cut type, and perforated tapes are a few cases of modification of the existing plane tape. [5][6][7][8] These studies revealed that insertion of the twisted tape will enhance the heat transfer rate. From the literature, it is also observed that twisted tapes perform well in laminar flow than that of turbulent flow.…”

“…Plenty of research has been conducted by researchers in using either a full‐length twisted tape or modifications to the full length . Uses of multiple tapes inside the circular duct, perforated twisted tapes, notched tapes, spaced twisted tapes, v‐cut type, and perforated tapes are a few cases of modification of the existing plane tape . These studies revealed that insertion of the twisted tape will enhance the heat transfer rate.…”

Investigation of Overlapped Twisted Tapes Inserted in a Double-Pipe Heat Exchanger Using Two-Phase Nanofluid

“…They reported the maximum value of 1.27 for PEC numbers in the range of studied operational conditions. Ruengpayungsak et al [ 33 ] investigated centrally perforated twisted tape inserts numerically in both laminar and turbulent regimes. They reported the maximum value for PEC number equal to almost 8.92 and 1.33 for laminar and turbulent regimes, respectively.…”

Thermo-Hydraulic Performance Analysis on the Effects of Truncated Twisted Tape Inserts in a Tube Heat Exchanger

“…In the range of their operational conditions, they presented a maximum PEC number equal to 1.27. Centrally perforated twisted tape elements in a tube were investigated by Ruengpayungsak et al [36] for convective heat transfer enhancement under laminar and turbulent flow regimes. Maximum PEC values of 8.92 and 1.33 were reported for laminar and turbulent regimes, respectively.…”