A New Model for Forced-Convection Condensation on Integral-Fin Tubes

Cavallini, Alberto; Doretti, Luca; Longo, Giovanni Antonio; Rossetto, Luisa

doi:10.1115/1.2822687

Cited by 20 publications

(9 citation statements)

References 10 publications

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“…The [mal result is in the form of an algebraic expression for the enhancement ratio (ratio of heat flux or heattransfer coefficient for fmned tube based on smooth tube area divided by that for a smooth tube with the same diameter and for the same vapour-to-surface temperature difference) which is independent of temperature difference or heat flux: The above results all apply to quiescent vapour. Cavallini et al [29] fitted data for high velocity vapour to their data for refrigerants using a correlation which satisfied the above result in the low velocity limit. The correlation fits most of the heat-transfer coefficient data for several fluids (excluding steam) to within about 25% as shown in Fig.…”

Section: Theoretically-based Correlationmentioning

confidence: 90%

Surface tension-affected laminar film condensation problems

Wang

Rose

2007

J Mech Sci Technol

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Following Nusselt [1] there were few developments in the theory of laminar film condensation until the advent of digital computers in the 1950s. Approximations used by Nusselt, namely neglect of inertia, convection and surface shear stress (for the free convection case) were then found to give very accurate results for the normal practical range of vapour-to-surface temperature difference. Subsequent developments treated the gas phase and dealt with superheated vapour, condensation in the presence of a non-condensing gas and condensation of mixtures. The temperature discontinuity at the vapour-liquid interface has been studied experimentally and theoretically since the 19 th century and more recently in the 1960s by experiments using liquid metals.In the present paper the focus is on the condensate film and, in particular, the role played by surface tension which is important for condensation on finned surfaces and in microchannels, owing to abrupt changes in curvature of the condensing surface. The way in which surface tension affects condensation heat transfer and difficulties which arise are first illustrated by reference to condensation on a smooth horizontal tube, where the effect of surface tension on heat transfer is minimal. Practically more relevant cases of condensation in microchannels and on finned surfaces and are then discussed and recent results presented.

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Section: Theoretically-based Correlationmentioning

confidence: 90%

Surface tension-affected laminar film condensation problems

Wang

Rose

2007

J Mech Sci Technol

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“…Experiments on single-tube condensation in the literature (e.g., Cavallini et al 1996;Cheng and Tao 1994;Cheng et al 1996;Cheng et al 1997) reported single-tube condensation heat transfer coefficients on enhanced tubes but none directly with R-134a. Chang et al (1996) reported results for R-134a on four different enhanced tubes, which included 1024 and 1575 fins/m (26 and 40 fins/in.)…”

Section: Downloaded By [] At 06:37 06 June 2016mentioning

confidence: 98%

An Investigation of Condensation Heat Transfer Performance of HFC-134a on Single Enhanced Tubes (RP-984)

Xie

Eckels

2003

HVAC&R Research

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Tests to measure shell-side heat transfer coefficients were performed on a single-tube test facility. HFC-134a was condensed on the horizontal test tube with cold water working as the coolant. Two 19.1 mm (0.75 in.) outer diameter (OD) enhanced tubes, one a two-dimensional (2D) finned tube and the other a three-dimensional (3D) enhanced tube, were used to construct the test section. For comparison purposes, a smooth tube of the same nominal diameter was also tested. The experiments were conducted over a heat flux range of 3155 to 63 100 W/m 2 (1000 to 20,000 Btu/h · ft 2 ) at saturation temperatures of 40 and 45°C (104 and 113°F).The tests revealed that the shell-side heat transfer coefficient dropped as heat flux increased. The enhanced tubes significantly improved the condensation heat transfer effectiveness compared with the smooth tube, with the 3D enhanced tube having the highest heat transfer coefficients. Specifically, the 2D tube had heat transfer coefficients that were 8.0 times better than the smooth tube, whereas enhancements of 11.8 times were seen in the 3D tube. The heat transfer coefficients for each tube were also compared with existing single-tube models.

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“…The appropriate correlations are utilized to calculate the heat transfer coef cients for the condensation [30,31], evaporation [32][33][34], and the water-side and single-phase refrigerant [35]. REFPROP [36] was used to calculate the refrigerant thermophysical properties throughout the cycle.…”

Section: Model C: Physical Dynamic Modelmentioning

confidence: 99%

Different modelling strategies for in situ liquid chillers

Browne

Bansal

2001

Proceedings of the Institution of Mechanical Engineers, Part A:

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This paper presents an overview of various simulation models that may be useful for predicting the in situ performance of vapour compression liquid chillers over a wide range of operating conditions. Five models were considered, namely the regression model, the steady state and transient physical models and the steady state and transient neurale network models. Typical real-time operating data taken under various conditions including start-up, quasi-static and modulating operation were used as input to the five models. The predicted performance was then compared with the experimental data to see the conditions under which each may be suitably applied. It was found that steady state models can give fairly accurate results under mildly dynamic conditions (±5 per cent) although, as the operation becomes more strongly transient, inaccuracies can be as high as 25 per cent. However, the dynamic models perform much better under these conditions (such as start-up and during sudden changes in load condition), predicting performance to within ±10 per cent.

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A New Model for Forced-Convection Condensation on Integral-Fin Tubes

Cited by 20 publications

References 10 publications

Surface tension-affected laminar film condensation problems

Surface tension-affected laminar film condensation problems

An Investigation of Condensation Heat Transfer Performance of HFC-134a on Single Enhanced Tubes (RP-984)

Different modelling strategies for in situ liquid chillers

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