Condensation in Smooth Horizontal Tubes

1998 ◽  
Vol 120 (1) ◽  
pp. 193-213 ◽  
Author(s):  
M. K. Dobson ◽  
J. C. Chato
Keyword(s):  
Heat Transfer ◽  
Flow Regime ◽  
Temperature Difference ◽  
Mass Flux ◽  
Flow Regimes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes ◽  
Transfer Behavior ◽  
Condensing Heat Transfer

An experimental study of heat transfer and flow regimes during condensation of refrigerants in horizontal tubes was conducted. Measurements were made in smooth, round tubes with diameters ranging from 3.14 mm to 7.04 mm. The refrigerants tested were R-12, R-22, R-134a, and near-azeotropic blends of R-32/R-125 in 50 percent/50 percent and 60 percent/40 percent compositions. The study focused primarily on measurement and prediction of condensing heat transfer coefficients and the relationship between heat transfer coefficients and two-phase flow regimes. Flow regimes were observed visually at the inlet and outlet of the test condenser as the heat transfer data were collected. Stratified, wavy, wavy annular, annular, annular mist, and slug flows were observed. True mist flow without a stable wall film was not observed during condensation tests. The experimental results were compared with existing flow regime maps and some corrections are suggested. The heat transfer behavior was controlled by the prevailing flow regime. For the purpose of analyzing condensing heat transfer behavior, the various flow regimes were divided into two broad categories of gravity-dominated and shear-dominated flows. In the gravity dominated flow regime, the dominant heat transfer mode was laminar film condensation in the top of the tube. This regime was characterized by heat transfer coefficients that depended on the wall-to-refrigerant temperature difference but were nearly independent of mass flux. In the shear-dominated flow regime, forced-convective condensation was the dominant heat transfer mechanism. This regime was characterized by heat transfer coefficients that were independent of temperature difference but very dependent on mass flux and quality. Heat transfer correlations that were developed for each of these flow regimes successfully predicted data from the present study and from several other sources.

An Experimental Investigation of Flow Patterns During Condensation of HFC Refrigerants in Horizontal Micro-Fin Tubes

2019 ◽  
Vol 27 (01) ◽  
pp. 1950010
Author(s):  
Sanjeev Singh ◽  
Rajeev Kukreja
Keyword(s):  
Heat Transfer ◽  
Flow Regime ◽  
Flow Regimes ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes ◽  
Regime Map ◽  
Fin Tubes ◽  
Flow Regime Map

Condensation heat transfer coefficients and flow regimes in two different horizontal micro-fin tubes are examined during the condensation of refrigerants R-134a and R-410A. The present investigation has focused on determination and prediction of condensation heat transfer coefficients and finding the interrelation between heat transfer coefficients and the prevailing flow regimes. During flow visualization, flow regimes have been captured using borosilicate glass tube at inlet and outlet of the test condenser using high speed digital camera. Stratified, stratified wavy, wavy annular, annular, slug and plug flows have been observed at different mass fluxes and vapor qualities of the refrigerants. The observed flow regimes are compared with the existing flow regime maps proposed by Breber et al. [Prediction of horizontal tube side condensation of pure components using flow regime criteria, J. Heat Transfer 102 (1980) 471–476], Tandon et al. [A new flow regime map for condensation inside horizontal tubes, J. Heat Transfer 104 (1982) 763–768.] and Thome et al. [Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, Int. J. Heat Mass Transfer 46 (2003) 3365–3387.] Thome et al. [Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, Int. J. Heat Mass Transfer 46 (2003) 3365–3387.] flow regime map shows good agreement with experimental data.

Prediction of Horizontal Tubeside Condensation of Pure Components Using Flow Regime Criteria

1980 ◽  
Vol 102 (3) ◽  
pp. 471-476 ◽  
Author(s):  
G. Breber ◽  
J. W. Palen ◽  
J. Taborek
Keyword(s):  
Heat Transfer ◽  
Prediction Method ◽  
Local Heat Transfer ◽  
Flow Regimes ◽  
Local Heat ◽  
Pure Component ◽  
Liquid Volume ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

In order to select the appropriate correlations for prediction of horizontal tubeside condensation heat transfer coefficients, it is necessary to estimate what types of flow patterns exist at various points along the tube. The main criteria required are shown to be the ratio of shear to gravity forces on the condensate film and the ratio of vapor volume to liquid volume. A recently proposed prediction method by Taitel and Dukler is compared with observed flow regimes for condensation in horizontal tubes. The theoretically obtained parameters are shown to characterize the flow regimes well. Based on these parameters, a simplified procedure for prediction of local heat transfer coefficients for pure component condensation in horizontal tubes is proposed.

Measurement of Condensation Heat Transfer Coefficients at Near-Critical Pressures in Refrigerant Blends

2006 ◽  
Vol 129 (8) ◽  
pp. 958-965 ◽  
Author(s):  
Yirong Jiang ◽  
Biswajit Mitra ◽  
Srinivas Garimella ◽  
Ulf C. Andresen
Keyword(s):  
Heat Transfer ◽  
Mass Flux ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Condensation Heat Transfer ◽  
Liquid Region ◽  
Transfer Coefficients ◽  
Reduced Pressure ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

This paper presents the results of an experimental study on condensation heat transfer of refrigerant blends R404A and R410A flowing through horizontal tubes of 9.4 and 6.2mm inner diameter at nominal pressures of 80% and 90% of the critical pressure. Local heat transfer coefficients were measured for the mass flux range 200<G<800kg∕m2‐s in small quality increments over the entire vapor-liquid region. Heat transfer coefficients increased with quality and mass flux, while the effect of reduced pressure was not very significant within this range of pressures. The heat transfer coefficients increased with a decrease in diameter.

Condensation Flow Mechanisms in Microchannels: Basis for Pressure Drop and Heat Transfer Models

2003 ◽  
Author(s):  
Srinivas Garimella
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Visualization ◽  
Flow Regime ◽  
Annular Flow ◽  
Flow Regimes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow Mechanisms ◽  
Transfer Models

This paper presents an overview of the use of flow visualization in micro- and mini-channel geometries for the development of pressure drop and heat transfer models during condensation of refrigerants. Condensation flow mechanisms for round, square and rectangular tubes with hydraulic diameters in the range 1–5 mm for 0 < x < 1 and 150 kg/m2-s and 750 kg/m2-s were recorded using unique experimental techniques that permit flow visualization during the condensation process. The effect of channel shape and miniaturization on the flow regime transitions was documented. The flow mechanisms were categorized into four different flow regimes: intermittent flow, wavy flow, annular flow, and dispersed flow. These flow regimes were further subdivided into several flow patterns within each regime. It was observed that the intermittent and annular flow regimes become larger as the tube hydraulic diameter is decreased, at the expense of the wavy flow regime. These maps and transition lines can be used to predict the flow regime or pattern that will be established for a given mass flux, quality and tube geometry. These observed flow mechanisms, together with pressure drop measurements, are being used to develop experimentally validated models for pressure drop during condensation in each of these flow regimes for a variety of circular and noncircular channels with 0.4 < Dh < 5 mm. These flow regime-based models yield substantially better pressure drop predictions than the traditionally used correlations that are primarily based on air-water flows for large diameter tubes. Condensation heat transfer coefficients were also measured using a unique thermal amplification technique that simultaneously allows for accurate measurement of the low heat transfer rates over small increments of refrigerant quality and high heat transfer coefficients characteristic of microchannels. Models for these measured heat transfer coefficients are being developed using the documented flow mechanisms and the corresponding pressure drop models as the basis.

Visualization Study of Steam Condensation in Rectangular Channel of Multichannel Cylinder Dryer

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Yan Yan ◽  
Dong Jixian ◽  
Tang Wei ◽  
Feng Shiyu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Regime ◽  
Mass Flux ◽  
Rectangular Channel ◽  
Steam Condensation ◽  
Transfer Coefficients ◽  
Steam Quality ◽  
Condensing Heat Transfer

The phenomenon of steam condensation occurring on one surface in a rectangular horizontal channel was experimentally studied. The experiment was conducted using a visualization method with a steam quality of 0.1–0.9 and mass flux of 20–50 kg/m2 s. Four flow patterns (annular, wave, slug, and plug) were observed, and the effects of quality and mass flux on the condensing heat transfer were analyzed. The mass flux and steam quality primarily affect the condensing heat transfer coefficient in the shear-dominated flow regime. The condensing heat transfer coefficients are nearly constant only in a certain range of steam quality. This result is disparate from what has been reported in previous literatures. It was also observed that the condensing heat transfer coefficient rises with an increase in the quality. Two flow regime maps were employed to predict the flow regimes observed in this study. The result reveals that the Tandon flow regime map agrees quite well with the experimental results.

Heat Transfer During Near-Critical-Pressure Condensation of Refrigerant Blends

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Srinivas Garimella ◽  
Ulf C. Andresen ◽  
Biswajit Mitra ◽  
Yirong Jiang ◽  
Brian M. Fronk
Keyword(s):  
Heat Transfer ◽  
Mass Flux ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Liquid Region ◽  
Transfer Coefficients ◽  
Reduced Pressure ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes ◽  
Wide Range

Heat transfer during condensation of refrigerant blends R404A and R410A flowing through horizontal tubes with 0.76 ≤ D ≤ 9.4 mm at nominal Pr = 0.8–0.9 was investigated. Local heat transfer coefficients were measured for the mass flux range 200 < G < 800 kg m−2 s−1 in small quality increments over the entire vapor–liquid region. Heat transfer coefficients increased with quality and mass flux, while the effect of reduced pressure was not very significant within this range of pressures. The heat transfer coefficients increased with a decrease in diameter. Correlations from the literature were not able to predict the condensation heat transfer coefficient for these fluids at these near-critical pressures over the wide range of tube diameters under consideration. A new flow-regime based model for heat transfer in the wavy, annular, and annular/wavy transition regimes, which predicts 91% of the data within ±25%, is proposed.

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