• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.2
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• pp.149-155
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• 2007

The row-by-row heat transfer characteristics of fin-and-tube heat exchangers were experimentally investigated. Three wavy fin samples having different rows (one, two and three) and one plain fin sample (three row) were tested for $600{\leq}Re_{D}{\leq}4,000$. The heat transfer data were obtained for individual rows, and the corresponding heat transfer coefficients were reduced from the data. Results showed that the heat transfer coefficients were strongly dependent on the tube row. The heat transfer coefficient decreased as the tube row increased. However, the row effect was different depending on the fin shape. For the wavy fin, the row effect significantly decreased as the Reynolds number increased, yielding approximately the same heat transfer coefficients at $Re_{D}{\approx}2,500$. For the plain fin, however, the row effect lasted for the whole Reynolds number range. The increased mixing of bulk flow by wavy channels appears to induce high heat transfer coefficient (accordingly diminishing row effect) at downstream rows. The heat transfer coefficients of individual rows were higher for heat exchangers having larger tube rows.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2390-2395
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• 2007

The present research was experimentally performed to analyze the effect of delta-wing vortex generators(DWVG) on the heat transfer of fin surface of the plate fin-oval tube. The local heat transfer coefficient of the fin surface for four kinds of DWVG's arrangement was measured by the naphthalene sublimation technique for Reynolds numbers ranging from 2000 to 3200. The results showed that the heat transfer of the plate fin-oval tube can be significantly enhanced by DWVG for relatively low Reynolds numbers.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.3
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• pp.292-300
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• 1999

Fin conduction not only enhances heat transfer to the ambient air but also increases tube-to-tube conduction. The latter is known to deteriorate the heat exchanger performance. Heat conduction between neighboring tubes thorough the fin is numerically investigated for accurate performance analysis of plate finned-tube heat exchangers. Governing equations for arbitrary plate fin are solved and the temperature distribution is obtained using the principle of superposition. Analysis is made using finite element method by changing the shapes of fin, the arrangements of tubes and the fin parameter mD. It is found that tube-to-tube conduction is significant when mD is small or the distance between neighboring tubes is small.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.4
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• pp.423-430
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• 1998

Single phase heat transfer coefficients were measured for turbulent water flow in a micro-fin tube by using Wilson plot technique. An experiment for counterflow heat exchange between the micro-fin tube and its outer annulus passage was performed. The annulus side heat transfer resistance was varied and the overall heat transfer coefficients were measured. The single-phase heat transfer coefficients in a micro-fin tube were obtained by Wilson plot technique. Nusselt numbers based on the real heat transfer area and the nominal area were about 35% and 50% larger than those for smooth tube respectively Also, single-phase heat transfer correlations based on real heat transfer area and nominal area have been proposed for a micro-fin tube.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1166-1171
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• 2009

Fin-tube heat exchangers are widely used in refrigeration systems. To improve the performance of fin-tube heat exchangers, the shape of plain fin was developed in slit fin and louver fin. These pins have higher heat transfer performance as well as larger pressure drop. Recent studies of a delta winglet vortex generators(DWVG) show less heat transfer capacity than louver fin. However, the DWVG have very small pressure drop. This paper compares the performance for the plain fin and DWVG fin in terms of flow characteristics and heat transfer based on CFD analyses. The DWVG generate vortex and delayed flow separation and leads to a reduction of a wake region behind a tube. The results show that the DWVG produce improved heat transfer and reduced pressure drop compared to a plain fin. This result is opposite to the Reynolds analogy.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.9
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• pp.762-767
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• 2003

An experimental study was conducted to investigate the heat transfer characteristics of a circular finned-tube heat exchanger. The nineteen cases of configuration varying fin material, fin outer diameter and fin pitch were tested by means of the experiment and the numerical calculation. The measured heat transfer data for the circular finned-tube heat exchanger were provided. A transition of heat transfer was found in the case of low fin pitch. The thermal conductivity of fin affected on the pure heat transfer coefficient.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.105-116
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• 2015

In this study, airside performance of round fin-and-tube heat exchangers are compared with that of the herringbone wave fin-and-tube heat exchangers with an aim to investigate the effect of fin shape on thermal performance. Results show that j factors of the round wave fin are 1.2~22% larger than those of herringbone wave fin. The f factors of the round wave fin are -1.0~29% smaller than those of herringbone wave fin for 1 or 2 row configuration. For 3 row configuration, f factors of the round wave fin are 8.3~23% larger. The reason may be attributed to the reduced recirculation zone in the valley of the fin for round wave fin as compared with that of the herringbone wave fin. For round wave fin, the effect of fin pitch on j and f factor is not significant. In addition, j factors decrease as the number of tube row increases. On the other hand, f factors are independent of the number of tube row. A new correlation was developed based on the present data.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.125-133
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• 1998

Nine tubes with trapezoidal integral-fins having fin densities from 748 to 1654fpm and 10,30 grooves and finned tubes with caves of 0.55 and 0.64mm height respectively are tested. A plain tube having same diameter as the finned tubes is also tested for comparison. In case of condensation CFC-11 condensates at saturation state of 32$^{\circ}C$ on the outside surface cooled by inside cooling water flows. And in case of boiling the refrigerant evaporates at a saturation state of 1bar on the outside tube surface and heat is supplied by hot water which circulates inside of the tube. The tube having fin density of 1299fpm and 30grooves has the best condensation overall heat transfer coefficient. However, as far as boiling heat transfer coefficient concerns, fin tubes with cave show higher value than low fin tube having fin density of 1299fpm and 30 grooves.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.11
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• pp.1555-1563
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• 1998

Heat transfer and pressure drop for ${\phi}10.07$ dry surface fin-tube heat exchanger with wave and wave-slit fins were measured for different fin spacings and number of tube rows. Longitudinal and transverse tube spacings of the heat exchangers are 21.65mm and 25mm respectively, and wave depth of wave fin is 1.5mm. The experiments were performed for 4 different fin spacings, 1.3, 1.5, 1.7 and 2.0mm, and the number of tube rows were 1,2 and 3 rows. The present results were compared with the previous results for the wave depth of 2mm. Also hydrophilic coated and bare fins were tested. Correlations for Colburn j-factor and friction factor were developed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.269-278
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• 2011

We investigate the heat-transfer and pressure-drop characteristics of fin-and-tube heat exchangers with a copper plate or copper spiral fins. Twenty-four samples with different fin pitches and tube rows were tested. For both configurations, the effect of the fin pitch on the j factor is negligible, and the f factor increases with the fin pitch. The effect of the tube row depends on the configuration. For plate fin-and-tube heat exchangers, the j factor decreases as the row number increases; the reverse is true for spiral exchangers. We explain this by considering the flow pattern. The j factor for plate fin-and-tube heat exchangers is larger than that for spiral exchangers, and the difference decreases as the row number increases. The f factor of the plate fin-and-tube heat exchanger is also larger. We compare our results with existing predictions of correlations.