Experimental and Numerical Investigation of the Gas Side Heat Transfer and Pressure Drop of Finned Tubes—Part I: Experimental Analysis

2012 ◽  
Vol 4 (4) ◽  
Author(s):  
Rene Hofmann ◽  
Heimo Walter
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Direction ◽  
Measurement Data ◽  
Heat Transfer Correlation ◽  
Average Deviation ◽  
Finned Tubes ◽  
Measurement Results ◽  
Staggered Arrangement ◽  
Industrial Boiler

In this study, a heat transfer and pressure drop correlation are determined for helically I- and U-shaped finned tubes as well as for solid I-finned tubes at constant transverse and longitudinal spacing. In the heat transfer correlation, the influence of the number of tube rows arranged in flow direction is taken into consideration. A detailed description of the test rig and the data reduction procedure is presented. A thorough uncertainty analysis was performed to validate the results. The investigation has shown that the influence of the fin geometry on the heat transfer of the helically segmented I- and U-shaped tubes can be disregarded. The heat transfer correlation, which is valid for the helically segmented I- and U-shaped tubes in a staggered arrangement, can describe 90% of all measurement data within ±15%. All measurements are performed for constant transverse and longitudinal spacing. For the pressure drop coefficient, two new correlations, which are only valid for helically segmented U shaped finned tubes in a staggered arrangement, show an average deviation of approximately ±13% for 90% of all measurement results. All new correlations are compared with correlations from open and established literature for industrial boiler applications. The new heat transfer and pressure drop correlations show a relative deviation of ±20% in comparison with correlations in open literature. The new pressure drop correlations show the same characteristic as most correlations in the open literature.

Comparison Between Numerical and Experimental Gas Side Heat Transfer and Pressure Drop of a Tube Bank With Solid and Segmented Circular I-Fins

2012 ◽  
Author(s):  
Rene Hofmann ◽  
Heimo Walter
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Tube Bundle ◽  
Three Dimensional ◽  
Finned Tube ◽  
Three Dimensional Model ◽  
Finned Tubes ◽  
Numerical Predictions ◽  
Staggered Arrangement ◽  
Flow Experiments

In the present work, a comparison between numerical and experimental gas side heat transfer and pressure drop for a tube bundle with solid and segmented circular finned tubes in a staggered arrangement is investigated. For the numerical simulations a three dimensional model of the finned tube are applied. Renormalization group theory (RNG) based k–ε turbulence model was used to calculate the turbulent flow. Experiments have been carried out to validate the numerical predictions. The numerical results for the Nu-number and pressure drop coefficient show a good agreement with the data from measurement. A comparison between solid and segmented finned tubes from the global calculation of the Nu-numbers within the analyzed Re-range shows an enhancement by applying segmented finned tubes rather than finned tubes with solid fins.

Tube Banks Heat Transfer Enhancement Using Conical Fins

2010 ◽  
Author(s):  
Ignacio Carvajal-Mariscal ◽  
Florencio Sanchez-Silva ◽  
Georgiy Polupan
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Pressure Drop ◽  
Finned Tube ◽  
Hot Water ◽  
Experimental Results ◽  
Tube Bank ◽  
Finned Tubes ◽  
Tube Banks ◽  
Annular Fins

In this work the heat transfer and pressure drop experimental results obtained in a two step finned tube bank with conical fins are presented. The tube bank had an equilateral triangle array composed of nine finned tubes with conical fins inclined 45 degrees in respect with the tube axis. The heat exchange external area of a single tube is approximately 0.07 m2. All necessary thermal parameters, inlet/outlet temperatures, mass flows, for the heat balance in the tube bank were determined for different air velocities, Re = 3400–18400, and one constant thermal charge provided by a hot water flow with a temperature of 80 °C. As a result, the correlations for the heat transfer and pressure drop calculation were obtained. The experimental results were compared against the analytical results for a tube bank with annular fins with the same heat exchange area. It was found that the proposed tube bank using finned tubes with conical fins shows an increment of heat transfer up to 58%.

Effects of Rib Arrangements on Pressure Drop and Heat Transfer in a Rib-Roughened Channel With a Sharp 180 deg Turn

1997 ◽  
Vol 119 (3) ◽  
pp. 610-616 ◽  
Author(s):  
S. Mochizuki ◽  
A. Murata ◽  
M. Fukunaga
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Secondary Flow ◽  
Flow Direction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Diameter Ratio ◽  
Equivalent Diameter ◽  
Before And After ◽  
Rib Roughened

The objective of this study was to investigate, through experiments, the combined effects of a sharp 180 deg turn and rib patterns on the pressure drop performance and distributions of the local heat transfer coefficient in an entire two-pass rib-roughened channel with a 180 deg turn. The rib pitch-to-equivalent diameter ratio P/de was 1.0, the rib-height-to-equivalent diameter ratio e/de was 0.09, and the rib angle relative to the main flow direction was varied from 30 ∼ 90 deg with an interval of 15 deg. Experiments were conducted for Reynolds numbers in the range 4000 ∼ 30,000. It was disclosed that, due to the interactions between the bend-induced secondary flow and the rib-induced secondary flow, the combination of rib patterns in the channel before and after the turn causes considerable differences in the pressure drop and heat transfer performance of the entire channel.

Numerical Simulation on Heat Transfer and Fluid Flow Characteristics of Arrays With Nonuniform Plate Length Positioned Obliquely to the Flow Direction

1998 ◽  
Vol 120 (4) ◽  
pp. 991-998 ◽  
Author(s):  
L. B. Wang ◽  
G. D. Jiang ◽  
W. Q. Tao ◽  
H. Ozoe
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Direction ◽  
Flow Characteristics ◽  
Numerical Results ◽  
The Body ◽  
Number Range ◽  
Plate Length ◽  
Nonuniform Plate ◽  
Short Plate

The periodically fully developed laminar heat transfer and pressure drop of arrays with nonuniform plate length aligned at an angle (25 deg) to air direction have been investigated by numerical analysis in the Reynolds number range of 50–1700. The body-fitted coordinate system generated by the multisurface method was adopted to retain the corresponding periodic relation of the lines in physical and computational domains. The computations were carried out just in one cycle. Numerical results show that both the heat transfer and pressure drop increase with the increase in the length ratio of the long plate to the short plate, and decrease with the decrease in the ratio of transverse pitch to the longitudinal pitch. The numerical results exhibit good agreement with available experimental data.

Shellside Waterflow Pressure Drop Distribution Measurements in an Industrial-Sized Test Heat Exchanger

1988 ◽  
Vol 110 (1) ◽  
pp. 60-67 ◽  
Author(s):  
H. Halle ◽  
J. M. Chenoweth ◽  
M. W. Wambsganss
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Operating Cost ◽  
Power Requirement ◽  
Pressure Drops ◽  
Pressure Losses ◽  
Finned Tubes ◽  
Heat Exchanger Design ◽  
Isothermal Water

Throughout the life of a heat exchanger, a significant part of the operating cost arises from pumping the heat transfer fluids through and past the tubes. The pumping power requirement is continuous and depends directly upon the magnitude of the pressure losses. Thus, in order to select an optimum heat exchanger design, it is is as important to be able to predict pressure drop accurately as it is to predict heat transfer. This paper presents experimental measurements of the shellside pressure drop for 24 different segmentally baffled bundle configurations in a 0.6-m (24-in.) diameter by 3.7-m (12-ft) long shell with single inlet and outlet nozzles. Both plain and finned tubes, nominally 19-mm (0.75-in.) outside diameter, were arranged on equilateral triangular, square, rotated triangular, and rotated square tube layouts with a tube pitch-to-diameter ratio of 1.25. Isothermal water tests for a range of Reynolds numbers from 7000 to 100,000 were run to measure overall as well as incremental pressure drops across sections of the exchanger. The experimental results are given and correlated with a pressure drop versus flowrate relationship.

scholarly journals Modelling and Evaluation of the Thermohydraulic Performance of Finned-Tube Supercritical Carbon Dioxide Gas Coolers

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1031 ◽  
Author(s):  
Lei Chai ◽  
Konstantinos M. Tsamos ◽  
Savvas A. Tassou
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Pressure Drop ◽  
Supercritical Carbon Dioxide ◽  
Heat Pump ◽  
Life Cycle Cost ◽  
Flow Direction ◽  
Finned Tube ◽  
Distributed Modelling ◽  
Supercritical Carbon

This paper investigates the thermohydraulic performance of finned-tube supercritical carbon dioxide (sCO2) gas coolers operating with refrigerant pressures near the critical point. A distributed modelling approach combined with the ε-NTU method has been developed for the simulation of the gas cooler. The heat transfer and pressure drop for each evenly divided segment are calculated using empirical correlations for Nusselt number and friction factor. The model was validated against test results and then used to investigate the influence of design and operating parameters on local and overall gas cooler performance. The results show that the refrigerant heat-transfer coefficient increases with decreasing temperature and reaches its maximum close to the pseudocritical temperature before beginning to decrease. The pressure drop increases along the flow direction with decreasing temperature. Overall performance results illustrate that higher refrigerant mass flow rate and decreasing finned-tube diameter lead to improved heat-transfer rates but also increased pressure drops. Design optimization of gas coolers should take into consideration their impact on overall refrigeration performance and life cycle cost. This is important in the drive to reduce the footprint of components, energy consumption, and environmental impacts of refrigeration and heat-pump systems. The present work provides practical guidance to the design of finned-tube gas coolers and can be used as the basis for the modelling of integrated sCO2 refrigeration and heat-pump systems.

Experimental Study on Characteristics of Condensation and Flow Resistance Inside Horizontal Corrugated Low Finned Tubes

2018 ◽  
Author(s):  
Bin Ren ◽  
Xiaoying Tang ◽  
Hongliang Lu ◽  
Dongliang Fu ◽  
Yannan Du ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Performance Evaluation ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Flow Resistance ◽  
Vapor Quality ◽  
Transfer Coefficients ◽  
Finned Tubes ◽  
Heat Transfer Coefficients ◽  
Inlet Conditions

It is the simplest and most feasible method to enhance heat transfer by replacing the smooth tube with various kinds of special-shaped enhanced tubes. In this paper, the characteristics of condensation and flow resistance inside horizontal corrugated low finned tubes were studied experimentally. The effects of steam inlet conditions and condensation tubes structural parameters were analyzed. The results showed that the heat transfer performance inside corrugated low finned tubes was greater than that inside smooth tubes. Like inside smooth tubes, the heat transfer coefficients increased with the vapor quality and steam mass flux. But the enhancement rate showed the opposite trend. And the heat transfer coefficients inside corrugated low finned tubes increased with the decrease of pitch and increase of protrusion height. Meanwhile, the variation trend of pressure drop gradient changing with inlet conditions and construal parameters was consistent with trend of heat transfer coefficient. The performance evaluation criteria were used to evaluate the comprehensive performance. It was found that the maximum performance evaluation factor was acquired at the minimum vapor quality and mass flux. The maximum value was 2.24 happened in the tube with pitch of 6 mm and height of 0.7mm. Finally, both the correlation for heat transfer coefficient and correlation for pressure drop gradient were developed by fitting experimental data. And this would provide calculation foundations for the design of horizontal condensers with corrugated low finned tubes.

Flow Pattern, Heat Transfer and Pressure Drop Behaviors of Micro-Channel Flow Boiling

2018 ◽  
Author(s):  
Sira Saisorn ◽  
Pochai Srithumkhant ◽  
Pakorn Wongpromma ◽  
Maturose Suchatawat ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Flow Boiling ◽  
Flow Direction ◽  
Saturation Pressure ◽  
Nucleate Boiling ◽  
Steel Tube ◽  
Stainless Steel Tube

Two-phase flow of R-134a with high confinement number was experimentally carried out in this study. Flow boiling conditions for different orientations were controlled to take place in a stainless steel tube having a diameter of 0.5 mm. Based on a saturation pressure of 8 bar, a heat flux range of 2–26 kW/m2, and a mass flux range of 610–815 kg/m2s, a constant surface heat flux condition was controlled by applied DC power supply on the test section. The flow behaviors were described based on flow pattern and pressure drop data while heat transfer mechanisms were explained by using heat transfer coefficient data. In this work, nucleate boiling was observed, and the importance of the change in the flow direction was neglected, corresponding to the confinement number of around 1.7.

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