Thermal performances of turbulent tubular flows enhanced by ribbed and grooved wire coils

Chang, Shyy Woei; Gao, Jing Yan; Shih, Hung Lin

doi:10.1016/j.ijheatmasstransfer.2015.07.070

Cited by 44 publications

(18 citation statements)

References 32 publications

(101 reference statements)

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“…An accumulator (4) was installed after the pump to reduce flow pulsations [63,64]. After the accumulator followed a bypass valve (5) and two valves in parallel, upstream of the two Coriolis flow meters (6). The Coriolis flow meter with a range of 4 -108 l/h was used for the mass flow rate measurements in the laminar and transitional flow regimes, while the Coriolis flow meter with a range of 54 -2 180 l/h was used for higher mass flow rate measurements, mostly in the turbulent flow regime.…”

Section: Experimental Set-upmentioning

confidence: 99%

“…These turbulators include coatings and/or roughness on the inner surface of the tube/channel passage, wire and helical coil inserts, corrugated tubes [6][7][8][9], outer grooved cylinder and inner rotating cylinder [10,11], helical and eccentric helical screw tape inserts [12][13][14], twisted tape inserts of different modifications [15][16][17][18][19][20][21][22][23][24][25], etc.…”

Section: Introductionmentioning

confidence: 99%

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Heat transfer and pressure drop characteristics of alternating clockwise and counter clockwise twisted tape inserts in the transitional flow regime

Abolarin

Everts

2019

International Journal of Heat and Mass Transfer

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The purpose of this study was to experimentally investigate the heat transfer and pressure drop characteristics in a smooth circular tube with alternating clockwise and counter clockwise twisted tape (CCCTT) inserts. The CCCTT inserts were fabricated from copper plate strips with a length, width and thickness of 450 mm, 18 mm and 1 mm respectively. The strips were twisted to obtain a twist ratio of 5 and 12 strips were joined longitudinally so that a clockwise direction twisted tape insert was connected to a counter clockwise direction twisted tape. The assembling was at connection angles of 0°, 30° and 60°, to form CCCTT inserts with an overall length of 5.27 m. The CCCTT inserts were placed in a smooth circular copper tube with an inner diameter of 19 mm. Water was used as the test fluid and experiments were conducted at constant heat fluxes of 1.35, 2, 3 and 4 kW/m 2 between Reynolds numbers of 300 and 11 404. This covered the laminar, transitional and turbulent flow regimes. Specific attention was given to the identification of the transitional flow regime with the CCCTT inserts and the influence of the connection angle and heat flux on the transitional flow regime. It was found that both the start and the end of the transitional flow regime were influenced by the connection angle and the heat flux. When different connection angles were compared it was found that an increase in connection angle enhanced the heat transfer in the transitional flow regime. An increase in heat flux significantly enhanced the heat transfer in the laminar flow regime and delayed transition. Heat transfer and pressure drop correlations were developed to predict the experimental data in the laminar, transitional and turbulent regimes as a function Reynolds number, modified Grashof number and connection angle.

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Section: Experimental Set-upmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Heat transfer and pressure drop characteristics of alternating clockwise and counter clockwise twisted tape inserts in the transitional flow regime

Abolarin

Everts

2019

International Journal of Heat and Mass Transfer

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“…Several researchers have experimentally studied the influence of coiled wire type of inserts on the heat transfer characteristics. 2,9,10 In general, they observed that there was an improvement in the heat transfer rate with a coiled tube when compared with a bare tube. A higher Nu and pressure drop were obtained, and the thermohydraulic performance index (THPI) was also reasonably better for a wired coil.…”

Section: Introductionmentioning

confidence: 99%

“…This creates a swirling motion around the coil, which increases the fluid mixing and hence this promotes the heat transfer rate. Several researchers have experimentally studied the influence of coiled wire type of inserts on the heat transfer characteristics . In general, they observed that there was an improvement in the heat transfer rate with a coiled tube when compared with a bare tube.…”

Section: Introductionmentioning

confidence: 99%

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

Kumar

Dinesha

Narayanan

et al. 2019

Heat Trans. Asian Res.

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In the present study, the effect of a helical coiled tape on the heat transfer characteristics in a tubular heat exchanger has been studied. Numerical analysis is carried out in a tubular heat exchanger with a helical coiled tape insert under laminar flow conditions. The heat transfer characteristics, like Nusselt number (Nu) and friction factor (f), have been determined. Numerical modeling is undertaken and validated using analytical results. To study the parametric variation, simulation is carried out for different width ratios (WR) and twist ratios (TRs). It is observed that Nu increases as the WR is increased and the TR is reduced. The thermohydraulic performance index (THPI) is measured and found to be higher for a combination of a higher WR and a higher TR. From the tested values, it is seen that for a combination of WR = 3 and TR = 1.25, the maximum THPI was observed. It is concluded that both the tape width and pitch will significantly influence the thermohydraulic characteristics in a tubular heat exchanger with a helical tape insert inserted.

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“…Various passive elements e.g. extended surfaces [2,3], corrugated absorber [4], artificial roughness [5,6], packed bed [7], wire coils [8,9], twisted tape [10] etc. have been utilized to ameliorate the performance of a solar air heater.…”

Section: Introductionmentioning

confidence: 99%

Analytical Investigation on Solar Air Heater with Fins and Twisted Tapes

Kumar¹,

Chand²

2019

IJHT

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The present work proposes an analytical investigation on the energetic and exergetic performance of an air heating solar collector having absorber surface equipped with fins and twisted tapes of twist ratio Y=2,4,6 and 8. A mathematical model capable of predicting the energy and exergy efficiency has been developed. The effects of mass flow rate, twist ratio and insolation on the thermal and exergy efficiency have been studied. Further, a comparison has been made with the results of smooth absorber solar air heater to check the performance enhancement over it. The results indicated that the thermal efficiency increases monotonically with increase in air flow rate but the exergy efficiency curve first goes up, achieves its maxima and then declines. Decrease in twist ratio from Y=8 to 2 leads to improvement in the thermal efficiency for whole range of studied mass flow rate but enhancement in the exergy efficiency was observed only up to the mass flow rate of 0.022 kg/s thereafter it starts decreasing.

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Thermal performances of turbulent tubular flows enhanced by ribbed and grooved wire coils

Cited by 44 publications

References 32 publications

Heat transfer and pressure drop characteristics of alternating clockwise and counter clockwise twisted tape inserts in the transitional flow regime

Heat transfer and pressure drop characteristics of alternating clockwise and counter clockwise twisted tape inserts in the transitional flow regime

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

Analytical Investigation on Solar Air Heater with Fins and Twisted Tapes

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