Condensation Pressure Drop and Heat Transfer in 5-mm-OD Micro-Fin Tubes

2012 ◽  
Author(s):  
Wei Li ◽  
Dan Huang ◽  
Zan Wu ◽  
Hong-Xia Li ◽  
Zhao-Yan Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Condensation Heat Transfer ◽  
Transfer Enhancement ◽  
Mass Fluxes ◽  
Fin Tubes ◽  
Condensation Heat Transfer Coefficient

An experimental investigation was performed for convective condensation of R410A inside four micro-fin tubes with the same outside diameter (OD) 5 mm and helix angle 18°. Data are for mass fluxes ranging from about 180 to 650 kg/m2s. The nominal saturation temperature is 320 K, with inlet and outlet qualities of 0.8 and 0.1, respectively. The results suggest that Tube 4 has the best thermal performance for its largest condensation heat transfer coefficient and relatively low pressure drop penalty. Condensation heat transfer coefficient decreases at first and then increases or flattens out gradually as G decreases. This complex mass-flux effect may be explained by the complex interactions between micro-fins and fluid. The heat transfer enhancement mechanism is mainly due to the surface area increase over the plain tube at large mass fluxes, while liquid drainage and interfacial turbulence play important roles in heat transfer enhancement at low mass fluxes. In addition, the experimental data was analyzed using seven existing pressure-drop and four heat-transfer models to verify their respective accuracies.

Experimental Investigation on the Condensation Heat Transfer and Pressure Drop Characteristics of R134A at High Mass Flux Conditions During Annular Flow Regime Inside a Vertical Smooth Tube

2009 ◽  
Author(s):  
Ahmet Selim Dalkilic ◽  
Suriyan Laohalertdecha ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Test Section ◽  
Annular Flow ◽  
Condensation Heat Transfer ◽  
Mass Fluxes ◽  
Condensation Heat Transfer Coefficient

This paper presents an experimental investigation on the co-current downward condensation of R134a inside a tube-in-tube heat exchanger. The test section is a 0.5 m long double tube with refrigerant flowing in the inner tube and cooling water flowing in the annulus. The inner tube is constructed from smooth copper tubing of 9.52 mm outer diameter and 8.1 mm inner diameter. The condensing temperatures are between 40 and 50°C, heat fluxes are between 9.78 and 50.69 kW m−2. The temperature difference between the saturation temperature of refrigerant and inlet wall varies between 1.66–8.94°C. Condensation experiments are done at mass fluxes varying between 340 and 456 kg m−2s−1 while the average qualities are between 0.76–0.96. The quality of the refrigerant in the test section is calculated considering the temperature and pressure measured from the test section. The pressure drop across the test section is directly measured by a differential pressure transducer. The average experimental heat transfer coefficient of the refrigerant is calculated by applying an energy balance based on the energy transferred from the test section. Experimental data of annular flow are examined such as the alteration of condensation heat transfer coefficient with the vapor average quality and temperature difference respectively according to different mass fluxes and condensing temperatures. The relation between the heat flux and temperature difference, besides this, the relation between the condensation heat transfer coefficient and condensing pressure are shown comparatively and the effects of mass flux and condensation temperature on the pressure drop are also discussed. The efficiency of the condenser is considered comparing with various experimental data according to tested condensing temperatures and mass fluxes of refrigerant. Some well known correlations and models of heat transfer coefficient were compared to show that annular flow models were independent of tube orientation provided that annular flow regime exists along the tube length and capable of predicting condensation heat transfer coefficient in the test tube.

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

2021 ◽  
Vol 9 ◽  
Author(s):  
Na Liu ◽  
Qian Zhao ◽  
Zhixiang Lan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Condensation Heat Transfer ◽  
Mass Fluxes ◽  
Fin Tubes ◽  
Tube Expansion ◽  
The Heat Transfer Coefficient

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.

Experimental Apparatus for Measuring in Tube Condensation Heat Transfer Coefficient and Pressure Drop Using Smooth and Micro-Fin Tubes for HFC Refrigerants

2008 ◽  
Author(s):  
Pradeep A. Patil ◽  
S. N. Sapali
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Condensation Heat Transfer ◽  
Test Facility ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Fin Tube ◽  
Condensation Heat Transfer Coefficient

An experimental test facility is designed and built to calculate condensation heat transfer coefficients and pressure drops for HFC-134a, R-404A, R-407C, R-507A in a smooth and micro-fin tube. The main objective of the experimentation is to investigate the enhancement in condensation heat transfer coefficient and increase in pressure drop using micro-fin tube for different condensing temperatures and further to develop an empirical correlation for heat transfer coefficient and pressure drop, which takes into account the micro-fin tube geometry, variation of condensing temperature and temperature difference (difference between condensing temperature and average temperature of cooling medium). The experimental setup has a facility to vary the different operating parameters such as condensing temperature, cooling water temperature, flow rate of refrigerant and cooling water etc and study their effect on heat transfer coefficients and pressure drops. The hermetically sealed reciprocating compressor is used in the system, thus the effect of lubricating oil on the heat transfer coefficient is taken in to account. This paper reports the detailed description of design and development of the test apparatus, control devices, instrumentation, and the experimental procedure. It also covers the comparative study of experimental apparatus with the existing one from the available literature survey. The condensation and pressure drop of HFC-134a in a smooth tube are measured and obtained the values of condensation heat transfer coefficients for different mass flux and condensing temperatures using modified Wilson plot technique with correlation coefficient above 0.9. The condensation heat transfer coefficient and pressure drop increases with increasing mass flux and decreases with increasing condensing temperature. The results are compared with existing available correlations for validation of test facility. The experimental data points have good association with available correlations except Cavallini-Zecchin Correlation.

Experimental Study on Condensation of R134a inside Horizontal Inner-Micro-Fin Tubes

2011 ◽  
Vol 354-355 ◽  
pp. 753-758
Author(s):  
Qi Wei Chen ◽  
Xin Ping Ouyang
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Velocity ◽  
Condensation Heat Transfer ◽  
Enhanced Tube ◽  
Glycol Solution ◽  
Fin Tubes ◽  
Condensation Heat Transfer Coefficient

An experimental study of condensation heat transfer of R134a on horizontal inner enhanced tubes was conducted. The tested tubes were inner-micro-fin tubes, named tube A and tube B, respectively. The tested pieces were double-pipe condensers. The glycol solution flowed in the space between outer surface of the enhanced tube and inner surface of outer tube. In the experiment, condensing temperature inside the enhanced tube was 51°C, and the flow velocity of glycol solution was 3.35m/s. The inlet temperature of glycol solution changed according to mass velocity of refrigerant, to maintain certain degree of undercooling of outlet refrigerant. The research showed that the condensation heat transfer coefficient of both tubes increased with the increasing mass velocity of refrigerant. when the mass velocity of refrigerant increased from 300kg/m2s to 700kg/m2s, the condensation heat transfer coefficient in tube A was 1.87% to 6.28% higher than that of tube B. However, the flow resistance of the refrigerant in tube B was 9.56% to 11.05% higher than in tube A. The structure of tube A was superior to that of tube B.

Experiment study on condensation heat transfer and pressure drop of steam flow inside rectangular tube with different aspect ratio

2020 ◽  
pp. 095765092097222
Author(s):  
Yan Yan ◽  
Jixian Dong ◽  
Tong Ren ◽  
Shiyu Feng
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Condensation Heat Transfer ◽  
Aspect Ratios ◽  
Rectangular Tubes ◽  
Condensation Heat Transfer Coefficient

In this study, the condensation heat transfer coefficient and pressure drop of steam are obtained in small rectangular tubes with different aspect ratios. The experiments were carried out on three rectangular tubes with aspect ratios of 1:2, 1:3 and 1:5, with mass flux between 25 and 45 kg/m2s, and vapor qualities between 0.1 and 0.8. The experimental data were analyzed to determine the effect of vapor quality, mass flux, and aspect ratio on the heat transfer coefficient and pressure drop. The results showed that the effect of aspect ratio on condensation heat transfer coefficient appears to be dependent on the flow pattern. For stratified flow, the condensation heat transfer coefficient increases as the mass flux increases. For annular flow, the condensation heat transfer coefficient hardly changed. The pressure drop always increases as the aspect ratio increases. Previous studies on round tube heat transfer and pressure drop correlations have not successfully predicted the small rectangular tube data; therefore, modified Shah correlation and Lockhart & Martinelli correlation are proposed, which predict the data with 20% and 23% RMS error, respectively.

Effect of Fin Geometry on Condensation of R407C in a Staggered Bundle of Horizontal Finned Tubes

2003 ◽  
Vol 125 (4) ◽  
pp. 653-660 ◽  
Author(s):  
H. Honda ◽  
N. Takata ◽  
H. Takamatsu ◽  
J. S. Kim ◽  
K. Usami
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Vapor Phase ◽  
Mass Velocity ◽  
Three Dimensional ◽  
Condensation Heat Transfer ◽  
Finned Tubes ◽  
Fin Tubes ◽  
Condensation Heat Transfer Coefficient

Experimental results are presented that show the effect of fin geometry on condensation of downward flowing zeotropic refrigerant mixture R407C in a staggered bundle of horizontal finned tubes. Two types of conventional low-fin tubes and three types of three-dimensional-fin tubes were tested. The refrigerant mass velocity ranged from 4 to 23 kg/m2 s and the condensation temperature difference from 3 to 12 K. The measured condensation heat transfer coefficient was lower than the previous results for R134a, with the difference being more significant for smaller mass velocity. The effect of fin geometry on the condensation heat transfer coefficient was less significant for R407C than for R134a. The effect of condensate inundation was more significant for the three-dimensional-fin tubes than for the low-fin tubes. By using the dimensionless heat transfer correlation for the condensate film that was based on the experimental data for R134a, a superficial vapor-phase heat transfer coefficient was obtained for condensation of R407C. The vapor-phase heat transfer coefficient showed characteristics similar to the vapor-phase mass transfer coefficient that was obtained in the previous study for R123/R134a.

Condensation Heat Transfer and Pressure Drop of R-404A in 7.0 mm O.D. Smooth and Microfin Tube at Low Mass Fluxes

2018 ◽  
Vol 26 (01) ◽  
pp. 1850005 ◽  
Author(s):  
Nae-Hyun Kim ◽  
Hyung-Ho Gook ◽  
Byung-Moo Lee
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Mass Flux ◽  
Enhancement Factor ◽  
Condensation Heat Transfer ◽  
Transfer Enhancement ◽  
Mass Fluxes ◽  
Penalty Factor ◽  
Low Mass

R-404A condensation heat transfer and pressure drop data are provided for 7.0[Formula: see text]mm O.D. smooth and microfin tubes. Tests were conducted for a range of mass fluxes (from 80 to 200[Formula: see text]kg/m2s) and quality (from 0.2 to 0.8). The heat flux was 6[Formula: see text]kW/m2 and saturation temperature was 45[Formula: see text]C. It was found that both the heat transfer enhancement factor and the pressure drop penalty factor increase as mass flux increases. The range of pressure drop penalty factor (0.99–1.27) was smaller than that of heat transfer enhancement factor (1.21–1.96). Smooth tube heat transfer coefficients and pressure drops are reasonably predicted by Shah [An improved and extended general correlation for heat transfer during condensation in plain tubes, Int. J. HVAC&R Res. 15 (2009) 889–913] and Jung and Radermacher [Prediction of pressure drop during horizontal annular flow boiling of pure and mixed refrigerants, Int. J. Heat Mass Transfer 32 (1989) 2435–2446] correlation, respectively. For the microfin tube, however, all the existing correlations do not adequately predict the present data. Poor predictions may be attributed to the lack of R-404A and low mass flux data in their database.

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