Heat transfer measurements and correlations in the transition region for a circular tube with three different inlet configurations

Ghajar, Afshin J.; Tam, Lap Mou

doi:10.1016/0894-1777(94)90075-2

Cited by 155 publications

(102 citation statements)

References 3 publications

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“…In the laminar flow regime, the results are under predicted on average, by 5.2%, in the turbulent flow regime, on average, by 2.4% and in the transitional flow regime, on average, by 5.3%. Hence there was a good agreement between the equations by Ghajar and Tam [38] and the measurements over the Reynolds number range.…”

Section: Nusselt Numbersupporting

confidence: 51%

“…The correlation by Ghajar and Tam [38] was used for comparison purposes in the laminar and turbulent flow regime and Equation 19 was used for comparison purposes in the transitional flow regime. Figure 13 to Figure 15 show how the adjusted water correlations predict the MWCNT-water nanofluid results.…”

Section: Comparison Of Results With Existing Heat Transfer Correlationsmentioning

confidence: 99%

“…For the transitional flow regime, the correlation developed by Ghajar and Tam [38] was modified to account for a developing length inlet condition. The modified correlation is shown below:…”

Section: Nusselt Numbermentioning

confidence: 99%

“…Heat transfer results were compared to the correlations developed by Ghajar and Tam [38] for laminar and turbulent flow, which are shown below:…”

Section: Nusselt Numbermentioning

confidence: 99%

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The influence of multi-walled carbon nanotubes on single-phase heat transfer and pressure drop characteristics in the transitional flow regime of smooth tubes

Meyer

McKrell

Grote

2013

International Journal of Heat and Mass Transfer

111

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In this paper, the convective heat transfer enhancement of aqueous suspensions of multiwalled carbon nanotubes flowing through a straight horizontal tube was investigated experimentally for a Reynolds number range of 1 000 -8 000, which included the transitional flow regime. The tube was made out of copper with an internal diameter of 5.16 mm.Experiments were conducted at a constant heat flux of 13 kW/m 2 with 0.33%, 0.75% and 1.0% volume concentrations of multi-walled carbon nanotubes. The nanotubes had an outside diameter of 10 -20 nm, an inside diameter of 3 -5 nm and a length of 10 -30 µm.Temperature and pressure drop measurements were taken, from which the heat transfer coefficients and friction factors were determined as a function of Reynolds number. It was found that heat transfer was enhanced when comparing the data on a Reynolds-Nusselt graph but when comparing the data at the same velocity, it was shown that heat transfer was not enhanced. Performance evaluation of the nanofluids showed that the increase in viscosity was four times the increase in the thermal conductivity, which resulted in an inefficient nanofluid.

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Section: Nusselt Numbersupporting

confidence: 51%

Section: Comparison Of Results With Existing Heat Transfer Correlationsmentioning

confidence: 99%

Section: Nusselt Numbermentioning

confidence: 99%

“…Heat transfer results were compared to the correlations developed by Ghajar and Tam [38] for laminar and turbulent flow, which are shown below:…”

Section: Nusselt Numbermentioning

confidence: 99%

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The influence of multi-walled carbon nanotubes on single-phase heat transfer and pressure drop characteristics in the transitional flow regime of smooth tubes

Meyer

McKrell

Grote

2013

International Journal of Heat and Mass Transfer

111

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“…The influence of the inlet on transition has been investigated systematically by the laboratories of Ghajar at Oklohoma state University and Meyer at the University of Pretoria. Ghajar and co-authors [25][26][27][28][29][30] investigated the influence of different types of inlets while using a constant heat flux. Meyer and co-authors used a constant wall temperature and investigated smooth [31] and enhanced tubes [32,33] and also investigated the use of nanofluids [34] during constant heat flux conditions.…”

Section: Introductionmentioning

confidence: 99%

Inlet flow effects in micro-channels in the laminar and transitional regimes on single-phase heat transfer coefficients and friction factors

Dirker

Meyer

Garach

2014

International Journal of Heat and Mass Transfer

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An experimental investigation of heat transfer and pressure drop in rectangular micro-channels was conducted for water in the laminar and transitional regimes for three different inlet configurations.The inlet types under consideration were the sudden contraction, bellmouth, and swirl inlet types, and hydraulic diameters of 0.57 mm, 0.85 mm, and 1.05 mm were covered. It was found that the critical Reynolds number and the transitional behaviour in terms of heat transfer coefficients and friction factors were influences significantly by the inlet type. For the sudden contraction inlet type, which were investigated for both adiabatic, as well as diabatic cases, adiabatic friction factors were predicted well by the laminar Shah and London correlation, while diabatic friction factors were decreased with an increase in wall heat flux. The sudden contraction inlet critical Reynolds numbers were found to be between 1 800 and 2 000 for adiabatic cases, while for diabatic cases the transition regime commenced at a Reynolds number of about 2 000. The bellmouth and swirl inlet types were investigated for diabatic cases only with swirl inlet tests limited to the 1.05 mm channel. Laminar 2 friction factors were approximately similar to those of the sudden contraction inlet type, however, after the commencement of transition both inlet types exhibited higher friction factors than the sudden contraction inlet. Minor transition occurred as early as at Reynolds numbers of 1 200 and 800 for the bellmouth and swirl inlet types respectively while major transition occurred at Reynolds numbers of approximately 1 800 and 1 500 respectively. Critical Reynolds numbers were found not be significantly influenced by the channel to diameter to length ratio considered in this study. Laminar Nusselt numbers were predicted well by conventional macro-channel thermal entry correlations. The swirl inlet type exhibited the highest friction factors and Nusselt numbers in the transitional regime followed by the bellmouth inlet type. During transition while compared with the sudden contraction inlet, both the bellmouth and swirl inlet types exhibited larger enhancement in heat transfer than increases in the friction factor penalty. Based on the experimental data obtained in this study, a set of correlations were developed which describes the relation between the friction factor and Colburn jfactor. Depending on the inlet type, the correlations predicted between 94% and 100% of the results to within 10% of the experimental measurements.

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Heat Transfer Measurements for Nonboiling Two‐Phase Flow

Ghajar

Tang

2013

Handbook of Measurement in Science and Engineering

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Two‐phase gas–liquid flow in a pipe is influenced by forces such as buoyancy, inertia, viscous, and surface tension, which result in various flow patterns being formed. The interaction of the two‐phase flow patterns with the inner pipe surface leads to the occurrence of nonuniform local heat transfer coefficient on the inner pipe surface. Due to the complex nature of two‐phase flow, the characterization of nonboiling gas–liquid flow heat transfer in a pipe at various inclination angles requires a functional experimental setup and proper experimental procedures. The functionality of the experimental setup and the experimental procedures to measure heat transfer systematically is discussed in this chapter. The measured heat transfer results indicate that the balance between the forces of buoyancy and inertia of two‐phase flow in a pipe, with varying inclinations, affects the local heat transfer coefficient on the inner pipe surface circumferentially. Two‐phase flow in a pipe with slight inclination angles has been observed with enhancement in heat transfer.

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Heat transfer measurements and correlations in the transition region for a circular tube with three different inlet configurations

Cited by 155 publications

References 3 publications

The influence of multi-walled carbon nanotubes on single-phase heat transfer and pressure drop characteristics in the transitional flow regime of smooth tubes

The influence of multi-walled carbon nanotubes on single-phase heat transfer and pressure drop characteristics in the transitional flow regime of smooth tubes

Inlet flow effects in micro-channels in the laminar and transitional regimes on single-phase heat transfer coefficients and friction factors

Heat Transfer Measurements for Nonboiling Two‐Phase Flow

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