Condensation heat transfer and pressure drop in flattened microfin tubes having different aspect ratios

Lee, E.J.; Kim, N.H.; Byun, Ho-Won

doi:10.1016/j.ijrefrig.2013.09.035

Cited by 21 publications

(4 citation statements)

References 35 publications

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“…Compared with light tubes, the internal thread structure of microfin tubes has largely extended the heat transfer area of internal working media and enhanced the turbulence intensity of fluids in microfin tubes [10][11][12] . In addition, this structure can allow microfin tubes to have excellent heat transfer performance by preventing fluids from generating thick interfacial layers; however, a smaller aperture can provide microfin tubes with a greater capacity to bear higher pressures [13] , which is aligned with the trend towards miniaturization of heat exchangers and offers a feasible option for carrying supercritical fluids. The further to improve the structure of microfin tubes, Kim and Shin [14] explored local convective heat transfer coefficients (CHTCs) of seven types of microfin tubes, and found the CHTC of internal microfin tubes is largely higher than light tubes with increasing fluid mass, however, they failed to find the influence of a specific part of microfin tubes on the tube heat transfer performance.…”

Section: Introductionmentioning

confidence: 99%

Influence of the microfin tube structure on the thermal-hydraulic performance of mixed supercritical CO2/R32

et al. 2023

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This research establishes 5 mm three-dimensional (3-d) flow and heat transfer microfin tube theoretical models with three different geometric structures. Using these models, the thermal-hydraulic performances of supercritical CO2/R32 in microfin tubes with different structures at various working conditions were investigated. The influences of each of three factors (pressure, mass flow, and microfin tube structures) on the thermal-hydraulic performance of CO2/R32 were evaluated respectively. Furthermore, orthogonal tests were undertaken to obtain the optimized combination of overall thermal-hydraulic performance. Results indicate that: the more the temperature of working media approximates to the critical temperature, the bigger the local convective heat transfer coefficient. Compared to non-critical temperatures, the convective heat transfer coefficient at critical temperature shows an eight-fold increase. The closer the pressure of the mixed working media is to the critical pressure, the greater the maximum convective heat transfer coefficient (CHTC) and the lower the temperature corresponding to the peak point, among which, the maximum CHTC under 7.5 MPa is three times as large as that at 8.5 MPa; the CHTC increases with increasing mass velocity, generally showing a linear relationship; through calculating the most optimal combination of thermal-hydraulic performance evaluation using orthogonal tests, the maximum CHTC is determined to be 96 kW/(m2?K).

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Section: Introductionmentioning

confidence: 99%

Influence of the microfin tube structure on the thermal-hydraulic performance of mixed supercritical CO2/R32

et al. 2023

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“…Many investigations on the thermal-hydraulic performance during condensation of different refrigerants in pristine micro-fin tubes with a variety of enhancements have been conducted by various researchers (Cavallini et al, 2009;Colombo et al, 2012;Dalkilic and Wongwises, 2009;Doretti et al, 2013;Lee et al, 2014;Liebenberg and Meyer, 2008;Wu and Sundén, 2016;Wu et al, 2014;Wu et al, 2015). The direct use of the condensation heat transfer and pressure drop results based on the pristine micro-fin tubes without any modification may cause deviation for the actual thermal-hydraulic performance of the heat exchangers.…”

Section: Introductionmentioning

confidence: 99%

Effect of Tube Expansion on Heat Transfer and Pressure Drop Characteristics During Condensation in Micro-Fin Tubes

2021

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Despite of the large number of research dedicated to condensation heat transfer and pressure drop characteristics in pristine micro-fin tubes, experimental investigation on effects of tube expansion have not been reported in the open literature. The paper reports measured cross-sectional dimensions, condensation heat transfer and pressure drop data of R1234ze(E) in pristine (5.10 mm OD) and expanded (5.26 mm OD) micro-fin tubes with mass fluxes from 100 to 300 kg/(m2·s). Effects of mass flux, vapor quality and tube expansion on the heat transfer coefficients and friction pressure gradients were investigated in the study. When the mass flux is 100 kg/(m2·s), the heat transfer coefficient and pressure drop of R1234ze(E) decrease after tube expansion. However, when the mass fluxes are 200 and 300 kg/(m2·s), tube expansion effects on the heat transfer coefficient and pressure drop are not notable. In addition, the experimental results are analyzed based on the existing condensation heat transfer and pressure drop correlations.

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“…With advancement in nanotechnology, surface modification methods have been proposed to increase the phase change efficiency in mini and micro domains [1][2][3][4][5] . Effect of different parameters such as surface wettability 6,7 , surface structure 8,9 , surface inclination 10,11 , saturation temperature 12 , and tube geometry 13,14 on condensation heat transfer in conventional scale have been investigated extensively. Although many studies have been performed on two-phase heat transfer involving boiling and evaporation in microchannels, there are fewer studies on condensation phase change systems in micro domain.…”

Section: Introductionmentioning

confidence: 99%

Parametric study on hydrothermal properties of condensing flow in microtube heat exchangers using numerical and experimental approaches

Sadaghiani¹

2021

Preprint

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Microchannels have increasingly been used to miniaturize heat transfer equipment, improve energy efficiency, and minimize heat transfer fluid inventory. A fundamental understanding of condensation in microscale will yield far-reaching benefits for the different areas of industry. In this study, microtubes with inner diameters of 250, 500, 600, and 900 µm were used to investigate the effect of microtube diameter, inlet quality, and mass flux on the liquid/vapor interface near the wall boundaries in condensing flow. After validation with the experimental results, a transient numerical model (based on the volume of fluid approach) was developed to investigate the hydrothermal properties of condensing such as bubble dynamics, flow map transitions, transient interface shear force, and temperature on flow condensation performance in terms of heat transfer coefficient and pressure drop. The liquid film thickness, slug velocity, and location of transition from annular flow to slug flow inside the microtube were characterized for different microtubes, and the resultant alteration in condensation flow heat transfer and pressure drop is discussed in detail. The obtained results indicated that the interfacial characteristics of condensing flow in microtubes with hydraulic diameters lower than 500µm are majorly different from those with D>500µm.

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Condensation heat transfer and pressure drop in flattened microfin tubes having different aspect ratios

Cited by 21 publications

References 35 publications

Influence of the microfin tube structure on the thermal-hydraulic performance of mixed supercritical CO2/R32

Influence of the microfin tube structure on the thermal-hydraulic performance of mixed supercritical CO2/R32

Effect of Tube Expansion on Heat Transfer and Pressure Drop Characteristics During Condensation in Micro-Fin Tubes

Parametric study on hydrothermal properties of condensing flow in microtube heat exchangers using numerical and experimental approaches

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