Performance investigation of laminar flow through tube fitted with hyperbolic-cut twisted tape inserts

ABSTRACT

This paper reports the numerical investigation of heat transfer intensification for hyperbolic-cut twisted tape (HCTT) fitted heat exchanger tube in laminar fluid flow using ANSYS Fluent 19.2. The laminar flow characteristics and thermal performance are examined for varying twisted ratio (3 ≤ TR ≤ 6), cut ratio (0.25 ≤ b/c ≤ 1), width (10 mm ≤ c ≤ 16 mm) over Re = 100–1500. The heat transfer laminar model is validated with standard correlations and available literature. The hyperbolic-cut twisted tape provides a better heat transfer and performance than that of the plain tube. This intensification is due to the hyperbolic-cut geometry, which provides additional vortex fluid flow, resulting in disruption of thermal boundary and better fluid mixing. The optimum performance of 4.82 is achieved for c = 16 mm at Re = 1500. Moreover, the performance of HCTT is further compared with existing works of literature and found HCTT performances better for all values of Re. The correlation is proposed to estimate thermal performance for tube fitted with HCTT in laminar flow.

Abbreviations: HCTT: Hyperbolic-cut twisted tape; PEC: Performance evaluation criterion; TR: Twisted ratio; TT: Twisted tape

KEYWORDS:

• Laminar flow
• numerical modeling
• thermo-hydraulic performance
• hyperbolic-cut
• twisted tape
• swirl flow

Acknowledgments

The authors would like to thank Mr. Abhinav Rajan (IIT Madras) for helping in simulation analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Nomenclatures

bDepth of hyperbolic-cut (mm)

cWidth of hyperbolic-cut (mm)

$c_p$Specific heat (J/kg-K)

DTube diameter (mm)

fFriction factor

$f_p$ Friction factor of the plain tube

$h_{local}$Local heat transfer coefficient (W/m²-K)

kThermal conductivity (W/m-k)

LTube length (mm)

$L_e$ Entrance length (mm)

Nu Nusselt number

$N{u}_{local}$ Local Nusselt number

$N{u}_p$Nusselt number of the plain tube

PPressure (Pa)

∆PPressure across the tube sections (Pa)

ReReynolds number

tTwisted tape thickness (mm)

TTemperature (K)

VMean velocity of fluid (m/s)

XAxial distance (mm)

yTwisted tape pitch (mm)

wTwisted tape width (mm)

Greek Symbols

ρDensity (kg/m³)

$\mu$ Viscosity (N-s/m²)

$\eta$ Thermo-hydraulic performance

Additional information

Funding

The authors have no funding to report.

Notes on contributors

Abhijit Rajan

Abhijit Rajan received his B.E. and M.Tech. from R.G.P.V. Bhopal, Madhya Pradesh, India, in 2013 and 2017, respectively. Then, he got Ph.D. position in the Department of Mechanical Engineering at National Institute of Technology Jamshedpur, India in 2018 and is working on solar energy and heat transfer under the supervision of Dr. Laljee Prasad.

Laljee Prasad

Laljee Prasad serves as Assistant Professor in the Department of Mechanical Engineering at National Institute of Technology Jamshedpur, India. He obtained his B.Sc. in Mechanical Engineering from Bhagalpur University in 1989 and M.Tech. in 1994 from ISM Dhanbad. He received his Ph.D. from IIT Roorkee in 2005. He has published more than 20 research papers in international/national journals and conferences. His research area includes solar energy and heat transfer.