Experimental investigation on heat transfer and friction factor characteristics of micro-finned tube fitted with full-length twisted tape and left–right twisted tape inserts of twist ratio 7.44, 8.27 and 11.17 has been presented. The experimental data obtained were compared with those obtained from plain tube published data. The heat transfer coefficient enhancement for left–right twisted inserts is higher than that for full-length twisted tape inserts for a given twist ratio. The empirical correlation for Nusselt number, friction relating Reynolds number and twist ratio was formed for both twisted tape inserts and left–right inserts and found to fit the experimental data within ±3.6% and ±2.5% for Nusselt number and ±7% and ±8.5% friction factor, respectively. Performance evaluation analysis was made and the maximum performance ratio was obtained for left–right twisted tape inserts.

Yagna S Mukkamala

Department of Automotive Engineering

School of Mechanical Engineering

Vellore Campus

Nagarajan P.K

Sivashanmugam P.

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Applied Thermal Engineering

Automotive radiators cool the engine coolant preventing heat seizure due to thermal expansion. Since both the coolant pump and radiator fan are parasitic devices (power has to be supplied by the engine), radiators with lower air-side and coolant pressure drop deploying coolants with superior thermo-physical characteristics that consume lower engine power need to be designed. Hence, augmented radiators with better overall <a href="https://www.sciencedirect.com/topics/engineering/heat-transfer-enhancement">heat transfer enhancement</a> using improved tube-side and air-side geometries that emit fewer emissions, save energy and can be easily fabricated, tested and analysed are necessary. This review addresses this issue. Specially designed and fabricated air-side fins and flat extruded coolant tubes have significantly improved the thermal performance of engine cooling systems. This article reviews the state-of-the-art in experimental testing and computational modeling of enhanced radiators which can be deployed with high performance vehicles and their superiority over conventional radiators. Unlike other reviews which focused solely on coolant tube and air-side design and spacing, flow velocities and pressure drops, this article will also focus on the impact of nano-coolants on improving the thermal efficiency of radiators while summarizing the efficacy of aerodynamically efficient air-side fins like delta-winglets in reducing air-side pressure drop. This article aims to consolidate the available literature in the 21st century (experimental and analytical) for enhanced radiators equipped with unconventional coolants and aerodynamically designed air-side fins and should serve as a single reference for practicing engineers and graduate students.

Renewable and Sustainable Energy Reviews

Contemporary trends in thermo-hydraulic testing and modeling of automotive radiators deploying nano-coolants and aerodynamically efficient air-side fins

Experiments were conducted with hot water in a horizontal 12.09-mm nominal diameter, 1.83-m long, double-pipe microfin tube heat exchanger, at effective Reynolds numbers in the range of 3573−12,621, and an average Prandtl number of 4.5. Smooth tube heat transfer and pressure drop measurements for similar flow conditions agreed satisfactorily with widely reported smooth tube correlations. Heat transfer measurements conducted at a linearly averaged, constant microfin tube wall temperature condition, and the corresponding isothermal pressure drop measurements were reduced to Nusselt numbers and friction factors based on the microfin tube effective diameter. A maximum heat transfer enhancement ratio (hdeff)microfin/hsmooth of 2.07 was obtained, while the corresponding efficiency index (hdeff/fdeff)microfin/(h/f)smooth was 1.77, indicating that this particular microfin tube performed excellently in the developing turbulent flow regime. The maximum friction enhancement (fdeff)microfin/fsmooth was 1.2. The key element in this work is the development of correlations (based on the effective diameter Reynolds number) corrected for entrance length effects for both heat transfer and friction pressure drop, and generation of experimental data, for transition flows in a microfin tube heat exchanger. Further, the thermal performance of such heat exchangers is quantified, based on the global measurements in the operating range of conventional HVAC equipment.

Journal of Enhanced Heat Transfer

Single-Phase Flow Pressure Drop and Heat Transfer Measurements in a Horizontal Microfin Tube in the Transition Regime

Encyclopedia of Pharmaceutical Science and Technology, Fourth Edition

Peptides and Proteins: Physical and Chemical Stability

International Journal of Heat and Mass Transfer

Performance assessment in a heat exchanger tube with alternate clockwise and counter-clockwise twisted-tape inserts

In this paper, experimentally determined pressure drop and heat transfer characteristics of flow of water in a 75-start spirally grooved tube with twisted tape insert are presented. Laminar to fully turbulent ranges of Reynolds numbers have been considered. The grooves are clockwise with respect to the direction of flow. Compared to smooth tube, the heat transfer enhancement due to spiral grooves is further augmented by inserting twisted tapes having twist ratios Y ≃ 10.15, 7.95 and 3.4. It is found that the direction of twist (clockwise and anticlockwise) influences the thermo-hydraulic characteristics. Constant pumping power comparisons with smooth tube characteristics show that in spirally grooved tube with and without twisted tape, heat transfer increases considerably in laminar and moderately in turbulent range of Reynolds numbers. However, for the bare spiral tube and for spiral tube with anticlockwise twisted tape (Y = 10.15), reduction in heat transfer is noticed over a transition range of Reynolds numbers. © 2008 Elsevier Ltd. All rights reserved.

Heat transfer and pressure drop in a spirally grooved tube with twisted tape insert

Chemical Engineering Communications

EXPERIMENTAL STUDIES ON HEAT TRANSFER AND FRICTION FACTOR CHARACTERISTICS OF TURBULENT FLOW THROUGH A CIRCULAR TUBE FITTED WITH RIGHT AND LEFT HELICAL SCREW-TAPE INSERTS

Studies on heat transfer and friction factor characteristics of turbulent flow through a micro-finned tube fitted with left–right inserts

Journal	Data powered by TypesetApplied Thermal Engineering
Publisher	Data powered by TypesetElsevier BV
ISSN	1359-4311
Open Access	0