Heat Transfer and Pressure Drop Characteristics of Smooth Horizontal Tubes in the Transitional Flow Regime

Meyer, Josua P.; Olivier, Jonathan

doi:10.1080/01457632.2013.876793

Cited by 24 publications

(18 citation statements)

References 25 publications

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“…12 that higher heat fluxes delayed the transition from laminar to transitional flow. Although these works were conducted at a constant heat flux the delayed transitions were also found by Meyer and Olivier [1,20,22]. In the laminar flow regime, the heat transfer coefficients increased with heat flux as the thermal gradient between the fluid and wall increased.…”

Section: Heat Fluxmentioning

confidence: 80%

“…Also, it appears as if the calming section length will not ensure a fully hydrodynamically developed velocity distribution at the test section inlet (based on Lh = 0.05ReD, at a transition Reynolds number of 3 000 and a diameter of 12.5 mm, it will take approximately 1.9 m for the flow to get fully developed, while the calming section length was 1.2 m). The inlet velocity distribution is an important factor to take into consideration as was shown by Ghajar and co-workers [12,13,45,46] as well as Meyer and co-workers [1,20,22,47]. They showed that another calming section length and/or geometry will influence the critical Reynolds number as well as the characteristics of the friction factors and heat transfer coefficients in the transitional flow regime.…”

Section: Introductionmentioning

confidence: 94%

“…Heat exchangers are found in domestic applications [1], industrial processes such as manufacturing, food processing and chemical plants [2,3], power stations that use fossil, nuclear or renewable energy sources [4], etc. In most of these cases, heat exchangers were designed to operate either in the laminar or the turbulent flow regime.…”

Section: Introductionmentioning

confidence: 99%

“…There are specifically two groups that have dedicated attention to experimental investigations in the transitional flow regime. The first groundbreaking work was performed by Ghajar and his co-workers from Oklahoma State University [12][13][14][15][16], and the second by Meyer and his coworkers at the University of Pretoria [1,5,[17][18][19][20]. Ghajar and his co-workers investigated three different types of inlets at constant heat flux conditions in smooth tubes (macro and micro).…”

Section: Introductionmentioning

confidence: 99%

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Heat transfer and pressure drop in the transitional flow regime for a smooth circular tube with twisted tape inserts and a square-edged inlet

Meyer

Abolarin

2018

International Journal of Heat and Mass Transfer

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HIGHLIGHTS• Experimental investigation of transitional flow regime in tubes with twisted tapes.• Results based on heat transfer coefficients and pressure drops.• Transitional flow regime was influenced by variation in twist ratios.• Variation in heat fluxes influenced the transitional flow regime.• Transition is earlier as the twist ratios and heat fluxes reduced. ABSTRACTThe purpose of this study was to experimentally investigate the heat transfer and pressure drop characteristics in the transitional flow regime of twisted tape inserts in a circular tube.Experiments were conducted in a circular tube with an internal diameter of 19.0 mm and a length of 5.27 m, and twisted tape inserts with twist ratios of 3, 4 and 5. A square-edged geometry was used at the tube inlet and it was experimentally operated with water flowing through it while the tube was heated with a constant heat flux. The experiments were conducted at three different heat fluxes of 2, 3 and 4 kW/m 2 . The experimental set-up was operated between Reynolds numbers of 400 and 11 400, and the Prandtl numbers varied between 2.9 and 6.7. Two methods were used to identify the transition points of the different heat fluxes and twist ratios. The first method used the standard deviation of the temperature measurements, and the second method used three linear curve fits on a log-log scale. The curve fits made it possible for correlations to 1 be developed for the non-dimensionalised heat transfer coefficients and friction factors, which took twist ratio, heat flux and Reynolds number into consideration. For the same heat flux, it was found that the Colburn j-factors increased as the twist ratios decreased, and transition started earlier. When the twist ratio was kept constant and the heat flux was varied, higher heat fluxes delayed the transition from laminar to transitional flow. The friction factors were found to increase as the twist ratio decreased. When both the twist ratio and the Reynolds number were kept constant, an increase in heat flux was found to decrease the friction factor.

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Section: Heat Fluxmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Heat transfer and pressure drop in the transitional flow regime for a smooth circular tube with twisted tape inserts and a square-edged inlet

Meyer

Abolarin

2018

International Journal of Heat and Mass Transfer

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“…Comparatively, due to the wider range of application of circular tubes, their characteristics in terms of heat transfer coefficients and friction factors have been extensively investigated and documented. This is especially so for the laminar and turbulent flow regimes [26][27][28][29][30], and to a lesser extent for the transitional flow regime [27,[31][32][33]. As such, many correlations exist for circular tubes, most of which are available for turbulent flow, followed in number by correlations for laminar flow, and least in number for the transitional flow regime.…”

mentioning

confidence: 99%

Heat transfer and pressure drop in annuli with approximately uniform internal wall temperatures in the transitional flow regime

Ndenguma

Dirker

Meyer

2017

International Journal of Heat and Mass Transfer

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Highlights• Experimental investigation of the transitional flow regime in an annulus for water.• Heated and cooled inner wall uniform wall temperature conditions are studied.• Nusselt number, friction factor and critical Reynolds number results are presented.• Annular dimensions directly impact resultsa new geometric parameter is proposed.• Nusselt number and friction factor correlations are developed. AbstractAn experimental study was conducted to determine the lower and upper Reynolds number limits of the transitional flow regime, and the characteristics of the heat transfer coefficients and friction factors for annular passages with different hydraulic diameters and diameter ratios in the transitional flow regime. Water was used in this investigation during isothermal, heating and cooling cases. Four horizontal concentric counter-flow tube-in-tube heat exchangers with conventional inlet geometries were considered to obtain the required data.The flow was both hydrodynamic and thermally developing, and the transitional flow was composed of mixed and forced convection types. The wall temperature on the inner surface of the annular passages was approximately uniform, while the outer surface was isothermal.Average Nusselt numbers were obtained for both the heating and cooling cases, while friction 1 Corresponding author: jaco.dirker@up.ac.za, Mechanical and Aeronautical Department, University of Pretoria, Private Bag X20, Hatfield 0028, RSA. 2 factors were obtained for heating, cooling and isothermal adiabatic conditions. Isothermal adiabatic condition was considered for reference purposes. The geometric size of the annular passage and direction of the heat flux (heating and cooling cases of annular fluid) had a significant influence on the heat transfer coefficients, friction factors and Reynolds number span of the transitional flow regime. The annular geometric parameters that represent the geometric size of the annular passage were proposed and found to describe the heat transfer coefficient and friction factors well. Subsequently, correlations for predicting the Nusselt numbers and friction factors in the transitional flow regime were developed.

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Turbulent Internal Flow: Momentum and Heat Transfer

2023

Introduction to Convective Heat Transfer

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Heat Transfer and Pressure Drop Characteristics of Smooth Horizontal Tubes in the Transitional Flow Regime

Cited by 24 publications

References 25 publications

Heat transfer and pressure drop in the transitional flow regime for a smooth circular tube with twisted tape inserts and a square-edged inlet

Heat transfer and pressure drop in the transitional flow regime for a smooth circular tube with twisted tape inserts and a square-edged inlet

Heat transfer and pressure drop in annuli with approximately uniform internal wall temperatures in the transitional flow regime

Turbulent Internal Flow: Momentum and Heat Transfer

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