scholarly journals Calculating the Efficiency of Complex-Shaped Fins

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 577
Author(s):  
Mateusz Marcinkowski ◽  
Dawid Taler
Keyword(s):  
Analytical Methods ◽  
Heat Exchangers ◽  
The Finite Element Method ◽  
Approximate Methods ◽  
Fin Efficiency ◽  
Finned Tubes ◽  
Hexagonal Shape ◽  
Schmidt's Method ◽  
Staggered Arrangement ◽  
Sector Method

Calculation of fin efficiency is necessary for the design of heat exchangers. This efficiency can be calculated for individual finned tubes or continuous fins. Continuous fins are mostly used in plate-fin and tube heat exchangers (PFTHEs). In most cases, the basic elements of those PFTHEs are circular, oval or flattened pipes, which contain circular or polygonal fins. Continuous fins, as can be observed in PFTHEs, are divided into virtual fins. Those fins can have a rectangular shape for an inline arrangement of pipes or a hexagonal shape for a staggered arrangement of pipes. This research shows a methodology of using the finite element method for calculating the efficiency of fins of any shape, placed on pipes of any shape. This paper presents examples of determining the efficiency of seeming fins, which are most commonly used in PFTHEs. In the article, we also compare the precision of calculations of the efficiency of complex-shaped fins using exact analytical methods and approximated methods: the equivalent circular fin method (Schmidt’s method) and the sector method. The results of the analytical methods and the approximate methods are compared to the results of numerical simulations. The calculations for continuous fins with complicated shapes of virtual fins, e.g., hexagonal elongated or segmented, are also presented.

Evaluation of the residual stress in stainless steel 304L hydraulically expanded joints

2020 ◽  
pp. 095440892096401
Author(s):  
Ying Hong ◽  
Xuesheng Wang ◽  
Yan Wang ◽  
Zhao Zhang ◽  
Yong Han
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Yield Strength ◽  
Residual Stresses ◽  
Heat Exchangers ◽  
Nuclear Power ◽  
The Finite Element Method ◽  
Power Stations ◽  
Stainless Steel 304 ◽  
Initial Clearance

Stainless steel 304 L tubes are commonly used in the fabrication of heat exchangers for nuclear power stations. The stress corrosion cracking (SCC) of 304 L tubes in hydraulically expanded tube-to-tubesheet joints is the main reason for the failure of heat exchangers. In this study, 304 L hydraulically expanded joint specimens were prepared and the residual stresses of a tube were evaluated with both an experimental method and the finite element method (FEM). The residual stresses in the outer and inner surfaces of the tube were measured by strain gauges. The expanding and unloading processes of the tube-to-tubesheet joints were simulated by the FEM. Furthermore, an SCC test was carried out to verify the results of the experimental measurement and the FEM. There was good agreement between the FEM and the experimental results. The distribution of the residual stress of the tube in the expanded joint was revealed by the FEM. The effects of the expansion pressure, initial tube-to-hole clearance, and yield strength of the tube on the residual stress in the transition zone that lay between the expanded and unexpanded region of the tube were investigated. The results showed that the residual stress of the expanded joint reached the maximum value when the initial clearance was eliminated. The residual stress level decreased with the decrease of the initial tube-to-hole clearance and yield strength. Finally, an effective method that would reduce the residual stress without losing tightness was proposed.

Modeling Large-Size Boilers As a Set of Heat Exchangers: Tips and Tricks

2001 ◽  
Author(s):  
Cristóbal Cortés ◽  
Luis I. Díez ◽  
Antonio Campo
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Practical Calculation ◽  
Approximate Methods ◽  
Monitoring Method ◽  
Large Size ◽  
Thermoelectric Plant ◽  
The One

Abstract Practical calculation of the heat-recovery sections of large-size boilers is still based on approximate methods. On the one hand, CFD-based models cannot directly handle the geometric intricacy of tube bundles, and thus rely on volume-averaged source terms that demand empirical input. On the other hand, the standard, lumped heat exchanger calculation, which can be a far simpler and more robust alternative, fails in several important aspects, mainly related to the effects of thermal radiation and the coupling between several sections. In this paper, we consider the diverse sections of a coal-fired utility boiler as a case study to show how to deal with these shortcomings. Under the objective of developing a simple monitoring method, we extend the traditional heat exchanger model to take into account most of the peculiarities of boiler superheaters, reheaters and economizers. Techniques range from the re-examination of analytical solutions to the auxiliary use of CFD calculations. The models are assembled to simulate the thermal performance of the boiler as a whole unit. Results are validated against actual measurements taken at a thermoelectric plant.

On the Use of the Finite Element Method on Some Acoustical Problems

1982 ◽  
Vol 104 (1) ◽  
pp. 108-112 ◽  
Author(s):  
L. Cederfeldt
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Analytical Methods ◽  
The Finite Element Method ◽  
Expansion Chamber ◽  
Low Frequencies ◽  
Angle Bend ◽  
Complicated Geometry ◽  
Sound Reduction ◽  
Element Method

In a project carried out in 1974-1975, financially supported by the National Swedish Council for Building Research, the finite element method was applied on some acoustical problems to illustrate the possibilities of the method. Calculations have been made for the following examples; sound attenuation of a lined right angle bend, a lined straight duct, and expansion chamber and the sound reduction of a resilient skin. The FEM has its power for small geometries particularly at low frequencies, that is, when analytical methods usually are weak. The more complicated geometry and boundary conditions of the studied problem may be the more powerful the FEM is compared to analytical methods.

Estimation of the Total Fatigue Life of Metallic Structures

2016 ◽  
Author(s):  
Peter Abdo ◽  
Farouk Fardoun ◽  
Phuoc Huynh
Keyword(s):  
Finite Element Method ◽  
Fatigue Life ◽  
Analytical Methods ◽  
Critical Section ◽  
The Finite Element Method ◽  
Local Conditions ◽  
Metallic Structures ◽  
Final Failure ◽  
Local Stresses ◽  
Number Of Cycles

The fatigue life of a component is defined as the total number of cycles or time to induce fatigue damage and to initiate a dominant fatigue flaw which is propagated to final failure.(Shigley & Mischke 2002) The aim of this project is to calculate the total fatigue life of metallic structures under cyclic loading by applying equations found by Basquin and Manson-Coffin. The local stresses and strains necessary for the calculation are determined by the finite element method. Former studies concerning this subject have used analytical methods to find the local conditions at the critical section. The analytical methods, based on Neuber and Molski-Glinka’s approaches, permit the calculation of the local stresses and strains at the critical section of the structure’s geometry as a function of the nominal stress (forces) applied. For the finite elements method, ABAQUS is used to determine the local conditions at the critical section of a T-shaped model.

A Survey of Important Auxiliary Equations for Selected Compact Heat Exchanger

2005 ◽  
Author(s):  
Richard G. Carranza
Keyword(s):  
Heat Exchanger ◽  
Surface Area ◽  
Heat Exchangers ◽  
Volume Ratio ◽  
Compact Heat Exchanger ◽  
Fin Efficiency ◽  
Compact Heat Exchangers ◽  
Central Location

Important auxiliary equations are presented that are typically used in compact heat exchanger research. These relationships are presented only for selected compact heat exchangers — bare pipe, helically finned pipe, plate finned pipe, spined pipe, and plate exchangers. The equations primarily address issues relating to heat exchanger geometry, surface area to volume ratio, and fin efficiency. Furthermore, they are organized in a systematic manner and consolidated in one central location for easy reference.

Carbon-foam finned tubes in air–water heat exchangers

2006 ◽  
Vol 26 (2-3) ◽  
pp. 131-143 ◽  
Author(s):  
Qijun Yu ◽  
Anthony G. Straatman ◽  
Brian E. Thompson
Keyword(s):  
Heat Exchangers ◽  
Carbon Foam ◽  
Finned Tubes

Performance of One- and Two-Row Tube and Plate Fin Heat Exchangers

1984 ◽  
Vol 106 (3) ◽  
pp. 627-632 ◽  
Author(s):  
E. C. Rosman ◽  
P. Carajilescov ◽  
F. E. M. Saboya
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchangers ◽  
Local Heat Transfer ◽  
Heat Transfer Analysis ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Fin Efficiency ◽  
Heat Transfer Coefficients ◽  
Experimental Apparatus

Heat exchangers consisting of finned tubes are commonly employed in air conditioning systems, air heaters, radiators, etc. Local measurements of mass transfer coefficients on fins, obtained by Saboya and Sparrow, are very nonuniform. In the present work, an experimental apparatus was set up to measure overall heat transfer coefficients for two-row tube and plate fin heat exchangers. The obtained results, together with Shepherd’s results for one-row exchangers, are used to transform the local mass transfer coefficients into local heat transfer coefficients. A numerical two-dimensional heat transfer analysis has been performed in order to obtain the temperature distribution and fin efficiency. The influences of the Reynolds number and fin material are also analyzed.

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.

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