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.

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.

scholarly journals Condensation inside smooth horizontal tubes: Part 1. Survey of the methods of heat-exchange prediction

2015 ◽  
Vol 19 (5) ◽  
pp. 1769-1789 ◽  
Author(s):  
Volodymyr Rifert ◽  
Volodymyr Sereda
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Film Condensation ◽  
Experimental Investigations ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

Survey of the works on condensation inside smooth horizontal tubes published from 1955 to 2013 has been performed. Theoretical and experimental investigations, as well as more than 25 methods and correlations for heat transfer prediction are considered. It is shown that accuracy of this prediction depends on the accuracy of volumetric vapor content and pressure drop at the interphase. The necessity of new studies concerning both local heat transfer coefficients and film condensation along tube perimeter and length under annular, stratified and intermediate regimes of phase flow was substantiated. These characteristics being defined will allow determining more precisely the boundaries of the flow regimes and the methods of heat transfer prediction.

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.

Local Heat Transfer Coefficients and Pressure Drop During Evaporation in a Smooth Horizontal Tube

2002 ◽  
Author(s):  
C. Aprea ◽  
A. Greco ◽  
G. P. Vanoli
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Local Heat ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

R22 is the most widely employed HCFC working fluid in vapour compression plant. HCFCs must be replaced within 2020. Major problems arise with the substitution of the working fluids, related to the decrease in performance of the plant. Therefore, extremely accurate design procedures are needed. The relative sizing of each of the components of the plant is crucial for cycle performance. For this reason, the knowledge of the new fluids heat transfer characteristics in condensers and evaporators is required. The local heat transfer coefficients and pressure drop of pure R22 and of the azeotropic mixture R507 (R125-R143a 50%/50% in weight) have been measured during convective boiling. The test section is a smooth horizontal tube made of a with a 6 mm I.D. stainless steel tube, 6 m length, uniformly heated by Joule effect. The effects of heat flux, mass flux and evaporation pressure on the heat transfer coefficients are investigated. The evaporating pressure varies within the range 3 ÷10 bar, the refrigerant mass flux within the range 200 ÷ 1000 kg/m2s, the heat flux within 0 ÷ 44 kW/m2. A comparison have been carried out between the experimental data and those predicted by means of the most credited literature relationships.

Local Heat Transfer Coefficients around Horizontal Tubes in Fluidized Beds

1980 ◽  
Vol 102 (1) ◽  
pp. 152-157 ◽  
Author(s):  
R. Chandran ◽  
J. C. Chen ◽  
F. W. Staub
Keyword(s):  
Heat Transfer ◽  
Particle Size ◽  
Fluidized Beds ◽  
Local Heat Transfer ◽  
Local Heat ◽  
General Tendency ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes ◽  
System Pressure

The local characteristics of heat transfer from horizontal tubes immersed in fluidized beds were investigated experimentally. Steady-state heat transfer measurements were obtained in air-fluidized beds of glass beads, both for a single tube and a ten-row bare tube bundle. The test results indicated that local heat transfer coefficients are strongly influenced by angular position and gas flow rate, as well as by particle size and system pressure. The heat transfer coefficients, averaged around the circumference of the tube, exhibited a general tendency to increase with decreasing particle size and increasing system pressure. The heat transfer coefficients for a tube in an inner-row position within the bundle were found to be slightly higher than those for a tube in the bottom-row. Comparison of the average heat transfer coefficient data obtained in this study with some of the existing correlations for heat transfer from horizontal tubes showed that the correlations are unsatisfactory.

Local and Average Heat Transfer and Pressure Drop for Refrigerants Evaporating in Horizontal Tubes

1960 ◽  
Vol 82 (3) ◽  
pp. 189-196 ◽  
Author(s):  
M. Altman ◽  
R. H. Norris ◽  
F. W. Staub
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Test Facility ◽  
Transfer Coefficients ◽  
Local Pressure ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

A test facility is described that has been constructed to investigate local heat transfer and pressure drop for evaporating or condensing refrigerants. The empirical method of B. Pierre [1] for correlating the average heat-transfer coefficients of refrigerants evaporating in horizontal tubes is presented in conjunction with the data of several authors [3–6]. Data on local heat-transfer coefficients and pressure drop are presented for Refrigerant-22 evaporating in two 4-ft-long, 0.343-in-ID straight horizontal tubes, and are correlated by a refinement of the curve proposed in [1]. The procedure of Martinelli-Nelson [9] correlated the data for local pressure drop within 15 per cent.

Heat Transfer to Carbon Dioxide in the Immediate Vicinity of the Critical Point

1969 ◽  
Vol 91 (1) ◽  
pp. 16-20 ◽  
Author(s):  
N. M. Schnurr
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Critical Point ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Reduced Pressure ◽  
Circular Duct ◽  
Heat Transfer Coefficients ◽  
Thermodynamic Critical Point

Local heat-transfer coefficients are measured for carbon dioxide very near the thermodynamic critical point for flow through an electrically heated circular duct. The experiments cover a range of fluid bulk temperatures spanning the transposed critical temperature and of pressure from 1075 to 1110 psia (reduced pressure from 1.003 to 1.03). The data are correlated by the equation Nuz = 0.0266 Rez0.77 Prw0.55 where the Prandtl number is evaluated at the wall temperature and Nusselt and Reynolds numbers are evaluated at a variable reference temperature. The dominant heat transfer mechanism is found to be turbulent forced convection. There is evidence that free convection effects are also present.

Numerical Simulation of Condensation for R410A in Horizontal Round and Flattened Minichannels

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Wei Li ◽  
Jingzhi Zhang ◽  
Guanghui Bai ◽  
Jin-liang Xu ◽  
Terrence W. Simon ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Liquid Film ◽  
Mass Flux ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Bottom Surface ◽  
Vapor Quality ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Heat transfer characteristics for condensation for R410A inside horizontal round (dh = 3.78 mm) and flattened tubes (aspect ratio (AR) = 3.07, 4.23, and 5.39) with larger horizontal than vertical dimensions at a saturation temperature of 320 K are investigated numerically. The flattened tube has flat upper and lower walls and circular end walls. The heat and mass transfer model for condensation is verified by comparing numerical heat transfer coefficients of round tubes with experimental data and empirical correlations. Liquid–vapor interfaces and local heat transfer coefficients are also presented to give a better understanding of the condensation process inside these tubes. The results indicate that local heat transfer coefficients increase with increasing mass flux, vapor quality, and aspect ratio. The enhancement of heat transfer coefficients for flattened tubes is more pronounced at higher mass flux and vapor quality values (about 1.5 times the heat transfer coefficients for round tubes when G = 1061 kg m−2 s−1, x ≥ 0.8). Unlike in the round tubes, the liquid film in the flattened tube accumulates at the sides of the bottom surface and at the middle of the top surface of the channels when vapor quality is low. Peak values of liquid film thickness in flattened tubes are obtained around angles about the centroid θ of 70 deg and 117 deg, where θ = 0 deg is upward.

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