Film Condensation of R-11 Vapor on Single Horizontal Enhanced Condenser Tubes

1990 ◽  
Vol 112 (1) ◽  
pp. 229-234 ◽  
Author(s):  
S. P. Sukhatme ◽  
B. S. Jagadish ◽  
P. Prabhakaran
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Film Condensation ◽  
Vertex Angle ◽  
Transfer Performance ◽  
Enhancement Ratio ◽  
Maximum Value ◽  
Enhanced Tubes ◽  
Fin Tubes ◽  
The Heat Transfer Coefficient

The heat transfer performance of R-11 vapor condensing on single horizontal trapezodially shaped integral-fin tubes has been investigated by systematically varying the fin density, the semi-vertex angle, and the fin height. For the nine copper tubes tested, the best performance has been obtained with a tube having a fin density of 1417 fpm, a semi-vertex angle of 10 deg, and a fin height of 1.22 mm. This tube has yielded a maximum value of the heat transfer coefficient of 16,500 W/m2 K at a ΔT of about 3 K, corresponding to an enhancement ratio of 10.3. The performance of the tube has been further improved by fabricating from it “specially enhanced” tubes having axial grooves of varying height. An enhancement ratio of 12.3 has been obtained with this type of tube.

Horizontal Plain and Low-Finned Condenser Tubes—Effect of Fin Spacing and Drainage Strips on Heat Transfer and Condensate Retention

1986 ◽  
Vol 108 (4) ◽  
pp. 946-950 ◽  
Author(s):  
K. K. Yau ◽  
J. R. Cooper ◽  
J. W. Rose
Keyword(s):  
Heat Transfer ◽  
Atmospheric Pressure ◽  
Heat Transfer Performance ◽  
Marginal Effect ◽  
Transfer Performance ◽  
Finned Tubes ◽  
Plain Tube ◽  
Fin Tubes ◽  
Fin Spacing ◽  
The Heat Transfer Coefficient

The paper reports a continuation of an experimental investigation of the effect of fin pitch on the heat transfer performance of horizontal, integral-fin tubes for condensation of steam at near-atmospheric pressure. The effects of “drainage strips” located along the lower edge of finned and plain tubes have been studied. These gave significant increases in the heat transfer coefficient for finned tubes but had only marginal effect for the plain tube. Condensate retention angles have also been measured for simulated condensation using water, ethylene glycol, and refrigerant-113 for finned tubes with and without drainage strips. In the latter case the data agreed satisfactorily with theory. Drainage strips were found to reduce the extent of holdup significantly.

Enhanced Condensation Heat-Transfer on Mini or Low Fin Tubes

2006 ◽  
Author(s):  
Adrian Briggs
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermophysical Properties ◽  
Heat Transfer Performance ◽  
Three Dimensional ◽  
Transfer Performance ◽  
Transfer Enhancement ◽  
Shell Side ◽  
Wide Range ◽  
Fin Tubes

This paper presents an overview of the use of low or mini-fin tubes for improving heat-transfer performance in shell-side condensers. The paper concentrates on, but is not limited to, the experimental and theoretical program in progress at Queen Mary, University of London. This work has so far resulted in an extensive data base of experimental data for condensation on single tubes, covering a wide range of tube geometries and fluid thermophysical properties and in the development of a simple to use model which predicts the majority of this data to within 20%. Work is progressing on the effects of vapor shear and on three-dimensional fin profiles; the later having shown the potential for even higher heat-transfer enhancement.

scholarly journals Experimental and Simulation Study of Micro-Channel Backplane Heat Pipe Air Conditioning System in Data Center

2020 ◽  
Vol 10 (4) ◽  
pp. 1255
Author(s):  
Liping Zeng ◽  
Xing Liu ◽  
Quan Zhang ◽  
Jun Yi ◽  
Xiaohua Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Transfer Performance ◽  
Outlet Temperature ◽  
Transfer Performance ◽  
Micro Channel ◽  
Heat Transfer Capacity ◽  
The Heat Transfer Coefficient

This paper mainly studies the heat transfer performance of backplane micro-channel heat pipes by establishing a steady-state numerical model. Compared with the experimental data, the heat transfer characteristics under different structure parameters and operating parameters were studied, and the change of heat transfer coefficient inside the system, the air outlet temperature of the back plate and the influence of different environmental factors on the heat transfer performance of the system were analyzed. The results show that the overall error between simulation results and experimental data is less than 10%. In the range of the optimal filling rate (FR = 64.40%–73.60%), the outlet temperature at the lowest point and the highest point of the evaporation section is 22.46 °C and 19.60 °C, the temperature difference does not exceed 3 °C, and the distribution gradient in vertical height is small and the air outlet temperature is uniform. The heat transfer coefficient between the evaporator and the condenser is larger than the heat transfer coefficient under the conditions of low and high liquid charge rate. It increases gradually along the flow direction, and decreases gradually with the flow rate of the condenser. When the width of the flat tube of the evaporator increases from 20 mm to 28 mm, the internal pressure drop of the evaporator decreases by 45.83% and the heat exchange increases by 18.34%. When the number of evaporator slices increases from 16 to 24, the heat transfer increases first and then decreases, with an overall decrease of 2.86% and an increase of 87.67% in the internal pressure drop of the evaporator. The inclination angle of the corrugation changes from 30° to 60°, and the heat transfer capacity and pressure drop increase. After the inclination angle is greater than 60°, the heat transfer capacity and resistance decrease. The results are of great significance to system optimization design and engineering practical application.

Heat Transfer Performance During Condensation Inside Spiralled Micro-Fin Tubes

2004 ◽  
Vol 126 (3) ◽  
pp. 321-328 ◽  
Author(s):  
Jean-Pierre M. Bukasa ◽  
Leon Liebenberg ◽  
Josua P. Meyer
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Geometric Parameters ◽  
Experimental Results ◽  
Outer Diameter ◽  
Transfer Performance ◽  
Fin Tube ◽  
R 134A ◽  
Fin Tubes ◽  
Spiral Angle

The effect of the spiral angle on the heat transfer performance in micro-fin tube condensers has not yet been clearly established because other geometric parameters affecting the heat transfer performance were simultaneously varied in previous studies. This paper reports on the influence of the spiral angle on the heat transfer during condensation inside spiralled micro-fin tubes having all other geometric parameters constant. Tests were conducted for condensation of R-22, R-134a, and R-407C inside a smooth (9.52 mm outer diameter) and three micro-fin tubes with approximately the same diameter, having spiral angles of 10 deg, 18 deg, and 37 deg, respectively. Experimental results indicated a heat transfer augmentation with spiral angle increase. A new semi-empirical predictive correlation was developed for practical design of spiralled micro-fin tubes. The proposed new correlation predicted the majority of experimental results of the present study within a deviation zone of ±20%.

Study on the Effect of the Evaporator Area on the Heat Transfer Performance in the Gravity Feed Liquid Refrigeration System

2013 ◽  
Vol 441 ◽  
pp. 112-115 ◽  
Author(s):  
Qing Jiang Liu ◽  
Fang Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Heat Transfer Performance ◽  
System Optimization ◽  
Transfer Performance ◽  
Refrigeration System ◽  
Original Design ◽  
The Heat Transfer Coefficient

In order to study the effect on heat transfer performance of evaporator in the gravity feed liquid refrigeration system the different evaporator area, the simulation procedure is worked out. The procedure uses the visual basic language. The procedure can figure out the heat transfer coefficient and the temperature difference in different evaporator area and evaporating temperature with the required refrigerating capacity. Through simulation calculation, when the area is 80% of the original design area of evaporator, the evaporator of the heat transfer coefficient and heat transfer temperature difference is the most reasonable and the evaporator of the refrigerating capacity can meet the requirements of cold storage. The program provides the reliable data for the gravity feed liquid cooling system optimization.

Comparison of Heat Transfer Performance Between Smooth and Enhanced Heat Transfer Tubes

2019 ◽  
Author(s):  
David J. Kukulka ◽  
Wei Li ◽  
Rick Smith
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
High Performance ◽  
Heat Transfer Performance ◽  
Industrial Applications ◽  
Material Surface ◽  
Transfer Performance ◽  
Enhanced Heat Transfer ◽  
Enhanced Tubes ◽  
Smooth Tubes

Abstract Heat transfer enhancement is an important factor in obtaining energy efficiency improvements in all heat transfer applications. A numeric study was performed that compares the performance of heat exchangers using the Vipertex enhanced heat transfer tubes (model 1EHT) to the performance of heat exchangers that use smooth surface tubes and other enhanced tubes. Surface enhancement of the 1EHT tube is accomplished through the use of the primary dimple enhancement and a secondary background pattern made up of petal arrays. Utilization of enhanced heat transfer tubes is an effective method that is utilized in the development of high performance thermal systems. Vipertex™ tubes, have been designed and produced through material surface modifications that produce flow optimized heat transfer tubes that increase heat transfer performance. Current energy demands and the desire to increase efficiencies of systems have prompted the development of optimized enhanced heat transfer surfaces. Enhanced heat transfer tubes are widely used in many areas (refrigeration, air-conditioning, process, petrochemical, chemical, etc.) in order to reduce cost, create a smaller application footprint or increase production. A new type of enhanced heat transfer tube has been created; therefore it is important to investigate relevant heat exchanger designs using the Vipertex enhanced surface tube in industrial applications and compare that performance to smooth tubes and other enhanced tubes. Results include design characteristics and performance predictions using the design simulations produced using HTRI Exchanger Suite (2016). Performance for all cases considered using the Vipertex tube predicted over design when compared to a smooth tube design. Vipertex 1EHT tubes produced enhanced heat transfer and cost efficient designs. In some of the case studies the 1EHT tubes produce an overdesign that is more than 35%, while smooth tubes produce an underdesign and other low fin tubes produce overdesign but not as large as the 1EHT tubes.

NUMERICAL STUDY ON FLOW BOILING IN A TREE-SHAPED MICROCHANNEL

Fractals ◽  
2019 ◽  
Vol 27 (07) ◽  
pp. 1950111
Author(s):  
WEI YU ◽  
LUYAO XU ◽  
SHUNJIA CHEN ◽  
FENG YAO
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Transfer Performance ◽  
The Heat Transfer Coefficient

A two-dimensional model is developed to numerically study the water flow boiling through a tree-shaped microchannel by VOF method. In this work, the bubble dynamics and flow patterns along the channel are examined. Additionally, the pressure drop, heat transfer performance and the effects of mass flow rate and heat flux on the heat transfer coefficient are analyzed and discussed. The numerical results indicate that, there are three main bubble dynamic behaviors at the wall, namely coalesce-lift-off, coalesce-slide and coalesce-reattachment. At the bifurcation in high branching level, the slug bubbles may coalesce or breakup. The flow patterns of bubbly, bubbly-slug flows occur at low branching level and slug flow occurs at high branching level. The passage of bubbles causes the increasing of fluid temperature and local pressure. Additionally, the pressure drop decreases with the branching level. The flow pattern and channel confinement effect play a vital role in heat transfer performance. The nucleate boiling dominant heat transfer is observed at low branching level, the heat transfer performance is enhanced with increasing branching level from [Formula: see text] to 2. While, at high branching level, the heat transfer performance becomes weaker due to the suppression of nucleate boiling. Moreover, the heat transfer coefficient increases with the mass flow rate and heat flux.

Visualization Study of Pool Boiling on Polished and Porous Coated Surfaces for Deionized Water and Al2O3-Water Nano-Fluids

2013 ◽  
Author(s):  
Gengwen Niu ◽  
Ji Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Transfer Performance ◽  
Pool Boiling ◽  
Porous Coating ◽  
Polished Surface ◽  
Transfer Performance ◽  
Working Medium ◽  
The Heat Transfer Coefficient ◽  
Nano Fluids

In the present work, pool boiling on copper porous coating and polished surface are studied experimentally at atmospheric pressure to explore the characteristics and the regime of boiling. A high-speed camera (maximum frame rate 10000 fps) with attached magnifying lens allowed precise observation of the incipient nucleation of boiling on the two surfaces. The observed boiling phenomena suggest different characteristics in the wall superheat, the heat transfer coefficient, the departure diameter of the bubble and the frequency of the bubble generation on two substrates for two working medium at different input power. The results indicate that the heat transfer performance is greatly enhanced by using porous coating and nano-fluids. The heat transfer coefficient on the porous coating is three to four times of that on the polished surface. Meanwhile, the temperature at incipience of boiling on the porous coating is lower than that on the polished surface qualitatively for the same working medium. The new contribution of this work is that we combined nano-fluids and porous surface together to explore the heat transfer performance and conducted visual experiments to observe the behavior of the bubbles of this assembly in the pool boiling.

A Mathematical Model Predicting Heat Transfer Performance in a Oscillating Heat Pipe

2007 ◽  
Author(s):  
H. B. Ma ◽  
B. Borgmeyer ◽  
P. Cheng ◽  
Y. Zhang
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Heat Pipe ◽  
Temperature Difference ◽  
Heat Transfer Performance ◽  
Temperature Drop ◽  
Film Condensation ◽  
Transfer Performance ◽  
Oscillating Heat Pipe ◽  
Oscillating Motion

A mathematical model predicting the oscillating motion in an oscillating heat pipe is developed. The model considers the vapor bubble as the gas spring for the oscillating motions including effects of operating temperature, non-linear vapor bulk modulus, and temperature difference between the evaporator and the condenser. Combining the oscillating motion predicted by the model, a mathematical model predicting the temperature drop between the evaporator and the condenser is developed including the effects of the forced convection heat transfer due to the oscillating motion, the confined evaporating heat transfer in the evaporating section, and the thin film condensation in the condensing section. In order to verify the mathematical model, an experimental investigation was conducted. Experimental results indicate that there exists an onset power input for the excitation of oscillating motions in an oscillating heat pipe, i.e., when the input power or the temperature difference from the evaporating section to the condensing section was higher than this onset value the oscillating motion started, resulting in an enhancement of the heat transfer in the pulsating heat pipe. Results of the investigation will assist in optimizing the heat transfer performance and provide a better understanding of heat transfer mechanisms occurring in the oscillating heat pipe.

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