Film Condensation of Steam on Horizontal Finned Tubes: Effect of Fin Spacing

1986 ◽  
Vol 108 (4) ◽  
pp. 960-966 ◽  
Author(s):  
A. S. Wanniarachchi ◽  
P. J. Marto ◽  
J. W. Rose
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Temperature Rise ◽  
Atmospheric Pressure ◽  
Smooth Tube ◽  
Film Condensation ◽  
Coolant Temperature ◽  
Finned Tubes ◽  
Fin Spacing

The film condensation heat transfer performance of six externally finned copper tubes has been evaluated. All tubes had rectangular-shaped fins with a height and thickness of 1 mm. The spacing between fins was 0.5, 1.0, 1.5, 2.0, 4.0, and 9.0 mm. Data were also obtained for a smooth tube whose outside diameter of 19.0 mm was equal to the diameter at the base of the fins for all of the finned tubes. Tests were performed both at atmospheric pressure and under vacuum (∼ 11.3 kPa). Steam flowed vertically downward with a velocity of approximately 1 and 2 m/s at atmospheric pressure and under vacuum, respectively. The smooth tube was fitted with wall thermocouples for the evaluation of the water-side heat transfer coefficient. This was used, subsequently, to determine the steam-side heat transfer coefficient for the finned tubes for which only overall measurements were made. Strenuous efforts were made to obtain high-accuracy data; in particular, the coolant temperature rise was determined by both quartz-crystal thermometers and a 10-junction thermopile. The two temperature-rise measurements always agreed to within ± 0.03 K. Care was taken to avoid errors due to the presence of noncondensing gases and to ensure that filmwise condensation conditions prevailed over the entire tube throughout all tests. The steam-side heat transfer coefficient for the smooth tube agreed closely with values found by other recent workers. Maximum steam-side enhancement was found for the tube with a fin spacing of 1.5 mm. At this fin spacing, the heat transfer enhancement ratios were around 3.6 and 5.2 for low-pressure and atmospheric pressure runs, respectively.

scholarly journals Numerical Analysis of Heat Transfer and Pressure Drop in Helically Micro-Finned Tubes

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 754
Author(s):  
Muhammad Ammar Ali ◽  
Muhammad Sajid ◽  
Emad Uddin ◽  
Niaz Bahadur ◽  
Zaib Ali
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Thermal Performance ◽  
Finned Tube ◽  
Smooth Tube ◽  
Working Fluid ◽  
Finned Tubes

In this study, the pressure drop and heat transfer characteristics of smooth tube and internal helically micro-finned tubes with two different fin-to-fin height ratios i.e., equal fin height and alternating fin height, are computationally analysed. The tube with alternating fin height is analysed for proof of concept of pressure drop reduction. A single phase steady turbulent flow model is used with a Reynolds number ranging from 12,000 to 54,000. Water is used as working fluid with inlet temperature of 55 °C and constant wall temperature of 20 °C is applied. Friction factor, heat transfer coefficient, Nusselt number, and Thermal Performance Index are evaluated and analysed. The numerical results are validated by comparison with the experimental and numerical data from literature. The results showed that the thermal performance is enhanced due to helically finned tube for a range of Reynolds numbers, but at the expense of increased pressure drop as compared to a smooth tube. The helically finned tube with alternating fin heights showed a 5% decrease in friction factor and <1% decrease in heat transfer coefficient when compared with the equal fin heights tube, making it a suitable choice for heat transfer applications.

Evaporative Heat Transfer and Pressure Drop Performance of Internally-Finned Tubes with Refrigerant 22

1979 ◽  
Vol 101 (3) ◽  
pp. 447-452 ◽  
Author(s):  
G. R. Kubanek ◽  
D. L. Miletti
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Velocity ◽  
Unit Length ◽  
Smooth Tube ◽  
Flow Area ◽  
Finned Tubes ◽  
Smooth Tubes

Heat transfer and pressure drop measurements were performed on three integral spiralled inner-fin tubes (12.7–15.9 mm OD, 30–32 fins, fin height 0.5–0.6 mm) with two-phase flow of refrigerant 22 under evaporating conditions. The data were compared with the performance of smooth tubes with and without a star-shaped insert. Based on the same length of heated test section (0.80 and 2.44 m), change in refrigerant quality (0.2 and 0.7) and mass velocity range (65,000 to 270,000 g/s · m2): (1) The enhancements in heat transfer coefficient for the internally-finned tubes over those for the smooth tubes ranged from 30 to 760 percent, and typically increased with mass velocity. Tighter fin spiralling significantly increased heat transfer. (2) The enhancements in heat transfer coefficient for the smooth tube with the star-shaped insert ranged from 40 to 370 percent, but decreased with mass velocity. (3) The increases in pressure drop for the internally-finned tubes over those for the smooth tubes ranged from 10 to 290 percent, while those for the smooth tube with the star-shaped insert were 300 to over 2000 percent. The factors enhancing the performance of the internally-finned tubes include the low fins which result in only a small reduction in cross-sectional flow area, and the tight spiral which increases the corner length per unit length of tube available for nucleation of vapor bubbles.

Shellside Vacuum Condensation With a Noncondensable Gas

2016 ◽  
Author(s):  
Susan N. Ritchey
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Atmospheric Pressure ◽  
High Speed ◽  
Process Conditions ◽  
Transfer Data ◽  
Noncondensable Gas ◽  
Overall Heat Transfer Coefficient ◽  
Vacuum Condensation

Shell-and-tube vacuum condensers are present in many industrial applications such as chemical manufacturing, distillation, and power production [1–3]. They are often used because operating a condenser under vacuum pressures can increase the efficiency of energy conversion, which increases the overall plant efficiency and saves money. Typical operating pressures in the petrochemical industry span a wide range of values, from one atmosphere (101.3 kPa) down to a medium vacuum (1 kPa). The current shellside condensation methods used to predict heat transfer coefficients are based on data collected near or above atmospheric pressure, and the available literature on shellside vacuum condensation generally lacks experimental data. The accuracy of these methods in vacuum conditions well below atmospheric pressure has yet to be validated. Recently, HTRI designed and constructed the Low Pressure Condensation Unit (LPCU) with a rectangular shellside test condenser. To date, heat transfer data have been collected in the LPCU for shellside condensation of a pure hydrocarbon and of a hydrocarbon with noncondensable gas at vacuum pressures ranging from 2.8 to 45 kPa (21 to 338 Torr). Traditional condensation literature methods underpredict the overall heat transfer coefficient by 20.8% ± 20.4% for the pure condensing fluid; whereas they overpredict heat transfer by 36.8% ± 40.0% with the addition of the noncondensable gas. Over or under predicting the overall heat transfer coefficient in the presence of noncondensable gases leads to inefficient condenser designs and the inability to achieve desired process conditions. With the addition of the noncondensable gas, the measured heat exchanger duty was significantly reduced compared to the pure fluid, even at inlet mole fractions below 5%. In one case, a noncondensable inlet mole fraction of 0.63% was estimated to reduce the duty by approximately 10%. Analysis of the acquired high-speed videos shows that the film thickness changes significantly from the top row to the bottom. The videos also display condensate drainage patterns and droplet interactions. The ripples and splashing of the condensate observed in the videos indicates that the Nusselt idealized model is not appropriate for analysis of a real condenser. This article presents the collected heat transfer data and high-speed images of shellside vacuum condensation flow patterns.

Fluid Flow and Heat Transfer Analysis of Automotive Radiator Using CFD Tools

2005 ◽  
Author(s):  
V. P. Malapure ◽  
A. Bhattacharya ◽  
Sushanta K. Mitra
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Temperature Drop ◽  
Three Dimensional ◽  
Heat Transfer Analysis ◽  
Coolant Temperature ◽  
Flow And Heat Transfer ◽  
Optimization Study

This paper presents a three-dimensional numerical analysis of flow and heat transfer over plate fins in a compact heat exchanger used as a radiator in the automotive industry. The aim of this study is to predict the heat transfer and pressure drop in the radiator. FLUENT 6.1 is used for simulation. Several cases are simulated in order to investigate the coolant temperature drop, heat transfer coefficient for the coolant and the air side along with the corresponding pressure drop. It is observed that the heat transfer and pressure drop fairly agree with experimental data. It is also found that the fin temperature depends on the frontal air velocity and the coolant side heat transfer coefficient is in good agreement with classical Dittus–Boelter correlation. It is also found that the specific dissipation increases with the coolant and the air flow rates. This work can further be extended to perform optimization study for radiator design.

Heat Transfer and Fouling Performance During Falling Film Evaporation in Vertical Porous Tubes

2020 ◽  
Author(s):  
Lei Wang ◽  
Weiyu Tang ◽  
Limin Zhao ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Smooth Tube ◽  
Outer Diameter ◽  
Falling Film ◽  
Film Evaporation ◽  
Falling Film Evaporation ◽  
The Heat Transfer Coefficient

Abstract An experimental investigation was conducted on falling film evaporation along two porous tubes, which were sintered by stainless-steel powder with a diameter of 0.45 and 1 um, respectively. The test section is a 2 m long sintered tube with an outer diameter of 25 mm and a wall thickness of 2 mm. During the experiment, the pressure inside the tube was maintained at 1 atm, the inlet temperature was 373 K, and mass flux ranged from 0.51 to 1.36 kg/ (m s). Conditions of the steam outside the pipe, which was the heat source, were fixed, while the fouling tests were carried out at a constant mass flow of 0.74 kg/ (m s) using high-concentration brine as work fluid. The overall heat transfer coefficient under different working conditions was tested and compared with the stainless steel smooth tube of the same dimensions. The heat transfer coefficient of the two porous stainless tubes are about 35% and 20% lower than that of the smooth one, showing an inferior effect because the steam in the pores of the pipe wall during the infiltration process will reduce the heat conductivity. The heat transfer coefficient of the smooth tube deteriorated severely due to the deposition of calcium carbonate, which had little effect on the sintered tubes. Besides, the fouling weight of porous tubes is 2.01 g and 0 g compared with 5.52 g of the smooth tube.

Use of Optimum Seeking Method in Test of Heat Transfer Performance of Finned Tubes

2010 ◽  
Author(s):  
Xinping Ouyang ◽  
Hua Zhang ◽  
Ni Liu ◽  
Guomei Wu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Curve Fitting ◽  
Convective Heat Transfer Coefficient ◽  
Finned Tubes ◽  
Fitting Method ◽  
Curve Fitting Method

Curve fitting method is often used in the test of heat transfer performance of heat exchangers. The convective heat transfer coefficient may be obtained with the method. However, there are defects with the method. A New Curve fitting method is introduced in this paper. Optimum seeking method is adopted in the New Curve fitting method. The new method is a practical method for test of convective heat transfer coefficient. There are few constraint with the method. Moreover, the results are more precise and the test is more convenient. The method is especially suitable for test of convective heat transfer coefficient of finned tubes outer surface. Two instances of use of the method are given.

One Dimensional Model for Rotating Channels in the Turbine System: Part 2 — Formulation and Validation for Film Condensation

2013 ◽  
Author(s):  
Murali Krishnan R. ◽  
Zain Dweik ◽  
Deoras Prabhudharwadkar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Steam Turbine ◽  
Compressible Flow ◽  
Saturation Temperature ◽  
Film Condensation ◽  
Bulk Temperature ◽  
Dimensional Model ◽  
One Dimensional

This paper provides an extension of the previously described [1] formulation of a one-dimensional model for steady, compressible flow inside a channel, to the steam turbine application. The major challenge faced in the network simulation of the steam turbine secondary system is the prediction of the condensation that occurs during the engine start-up on the cold parts that are below the saturation temperature. Neglecting condensation effects may result in large errors in the engine temperatures since they are calculated based on the boundary conditions (heat transfer coefficient and bulk temperature) which depend on the solution of the network analysis. This paper provides a detailed formulation of a one-dimensional model for steady, compressible flow inside a channel which is based on the solution of two equations for a coupled system of mass, momentum and energy equations with wall condensation. The model also accounts for channel area variation, inclination with respect to the engine axis, rotation, wall friction and external heating. The formulation was first validated against existing 1D correlation for an idealized case. The wall condensation is modeled using the best-suited film condensation models for pressure and heat transfer coefficient available in the literature and has been validated against the experimental data with satisfactory predictions.

Transient Heat Transfer in a Vapor-Heated Heat Exchanger With Arbitrary Timewise-Variant Flow Perturbation

1964 ◽  
Vol 86 (2) ◽  
pp. 133-142 ◽  
Author(s):  
Wen-Jei Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Amplitude Ratio ◽  
Perturbation Technique ◽  
Transient Heat Transfer ◽  
Coolant Temperature ◽  
Flow Perturbation

An analysis is made of transient heat transfer in a vapor-heated heat exchanger with an arbitrary timewise-variant flow perturbation. The heat-transfer coefficient between the tube and coolant is assumed to vary like the n power of the coolant velocity. Results are obtained through the use of the perturbation technique. General relations are presented in closed form and their application is illustrated by carrying out some typical examples: step, linear, exponential, and sinusoidal transients in the coolant flow velocity. The influence of the system parameters on the variation of the coolant temperature is investigated. A phenomenon of resonance in the amplitude-ratio and phase-shift is disclosed for the oscillating flow transient. This phenomenon is explained by analyzing the enthalpy change of the coolant particle in the heat exchanger. The results are also compared with the analyses that have assumed a constant heat-transfer coefficient. Heat exchangers to which these results apply include the double-pipe and shell- and-tube type heat exchangers.

Study on Free Convection Heat Transfer in a Finned Tube Array

2015 ◽  
Vol 23 (01) ◽  
pp. 1550007 ◽  
Author(s):  
Ryoji Katsuki ◽  
Tsutomu Shioyama ◽  
Chikako Iwaki ◽  
Tadamichi Yanazawa
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Finned Tube ◽  
Average Heat Transfer Coefficient ◽  
Average Heat ◽  
Finned Tubes ◽  
Air Cooled Heat Exchanger ◽  
The Heat Transfer Coefficient

We have been developing a free convection air cooled heat exchanger without power supply to improve economic efficiency and mechanical reliability. However, this heat exchanger requires a larger installation area than the forced draft type air cooled heat exchanger since a large heating surface is needed to compensate for the small heat transfer by natural convection. Therefore, we have been investigating a heat exchanger consisting of an array of finned tubes and chimney to increase the heat transfer coefficient. Since the heat transfer characteristics of finned tube arrays have not been clarified, we conducted experiments with a finned tube array to determine the relation between the configuration of finned tubes and the heat transfer coefficient of a tube array. The results showed that the average heat transfer coefficient increased with pitch in the vertical direction, and became constant when the pitch was over five times the fin diameter. The average heat transfer coefficient was about 1.4 times higher than that of a single finned tube in free space. The ratio of the average heat transfer coefficient of the finned tube array with chimney to that of a single finned tube was found to be independent of the difference in temperature between the tube surface and air.

Outer heat transfer coefficient for condensation of pure components on single horizontal low-finned tubes

2017 ◽  
Vol 55 (1) ◽  
pp. 3-16 ◽  
Author(s):  
Anna Reif ◽  
Alexander Büchner ◽  
Sebastian Rehfeldt ◽  
Harald Klein
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Finned Tubes
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