Experimental and numerical characterization of a mechanical expansion process for thin-walled tubes

Avalle, Massimiliano; Priarone, Paolo Claudio; Scattina, Alessandro

doi:10.1016/j.jmatprotec.2013.12.011

Cited by 14 publications

(11 citation statements)

References 11 publications

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“…Numerical simulations were used to study the effect of the expansion ratio on the gap between the tube and the fin and on the thermal conductance after expansion [5]. Although the speed of the expansion ball did not have a large effect on the expansion force [6], the geometry tolerances produced when manufacturing the tube can compromise the heat transfer performance [7]. The friction between the expansion ball and the tube is the most significant factor for increasing the expansion force, which was accurately predicted numerically when the applied friction coefficient was below 0.3 [8].…”

Section: Introductionmentioning

confidence: 99%

The Role of the Process and Design Variables in Improving the Performance of Heat Exchanger Tube Expansion

et al. 2018

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Abstract:In the expansion process of a fin-tube heat exchanger, the process variables and shape of the expansion ball affect the deformation of the tube's inner grooves, the adhesion, and the expansion force. These factors influence the efficiency of heat transfer and the lifetime of the expansion equipment. Therefore, this study analyzed the influential variables of the tube expansion process as well as the expansion ball design through experiments and simulations. A new method was proposed to determine the severity of adhesion in the tube's inner grooves using the expansion force rate. Expansion experiments with Al tubes show that the expansion force decreases when using a lubricant with high viscosity and when the lubricant remains on the expansion ball for a longer duration. Finite element analysis was also performed to examine the expansion of Cu tubes, which showed that the expansion force was higher when using expansion ball shapes that have higher contact area between the ball and tube surface. The radius of curvature of the expansion ball also influenced the expansion force. However, increasing the ratio of the radial force to the expansion force increased the deformation of the tube's inner grooves.

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Section: Introductionmentioning

confidence: 99%

The Role of the Process and Design Variables in Improving the Performance of Heat Exchanger Tube Expansion

et al. 2018

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“…The comparison is excellent for thicknesses of a smaller value, while it is less satisfactory for thicker tubes. From various analyses performed by the authors 2 and from what can be found in the literature, 9 the critical role of the friction value can be shown. A slight change in the friction coefficient value between the ogive and the inner wall of the tube could change the value of the axial driving force.…”

Section: Validation Of the Numerical Modelsmentioning

confidence: 83%

“…The ogive was modelled with a rigid material and axisymmetric elements. The friction between the ogive and the tube was modelled with a simple sliding model, and the coefficient of friction was chosen as 0.15 from a previous analysis by Avalle et al 2 Boundary conditions (Figure 6), to reproduce the real loading conditions, were applied to axial displacements of the first line of nodes of the tube, at the end opposite to that where the ogive was inserted. Then, a constant axial insertion speed of 10 mm/ s was applied to the ogive; a sliding interface was used to model the contact between the ogive surface and the internal tube surface.…”

Section: Modellingmentioning

confidence: 99%

“…As discussed by MacGregor et al, 1 in the hydraulic expansion, a fluid is introduced in the tube and pressurised at a required level. As discussed by Avalle et al, 2 in the mechanical expansion process, the external diameter of the tube is made larger than the diameter of the holes in the fins through the insertion of a tool. The diameter of the tool is larger than the internal diameter of the tube.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of the mechanical expansion process of thin-walled tubes for air heat-exchanger production

Scattina

Avalle

2022

Proceedings of the Institution of Mechanical Engineers, Part B:

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Finned tube air heat-exchangers are built by joining the tubes to the fins by various techniques. A technique mostly used for large heat-exchangers consists of fitting the tubes into the holes of the fins by expanding the tubes using a mechanical process. The expansion is achieved by inserting an ogive of a larger diameter into the tube. The intimate contact of tubes and fins due to the press fitting ensures the proper thermal connection. This work tries to describe an experimental-numerical procedure useful to study and predict the mechanical process and the process parameters. The procedure, based on material properties obtained from tensile tests and the use of the inverse method to identify the material parameters, is based on bi-dimensional finite element (FE) models used to simulate the expansion process. The FE model is then used for process optimisation regarding such parameters as the ogive shape and ogive sizes, friction coefficient and speed of insertion of the ogive into the tube. Indeed, size and shape uncertainties strongly influence the process parameters and the process quality, as well as the heat-exchanger efficiency. The use of numerical models was proven highly effective in predicting and optimising the process by quickly analysing the influencing factors and optimising the production.

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“…14 Some investigators have evaluated heat exchanger performance by measuring the expansion ratio that represents the fin-tube contact quality, 15 while others have optimized tube expanding process to maximize heat exchanging efficiency. 16 Moreover, the heat exchanging efficiency has been improved by optimizing the expanding velocity for tube expanding process, 17 and structural integrity of expansion balls and tubes has been numerically validated by calculating the stress fields produced on tubes during expansion process. 18 However, the tube material in these studies has been limited to copper, without using aluminum tubes.…”

Section: Introductionmentioning

confidence: 99%

A new methodology for detecting adhesion location in aluminum tube expansion

Kwon

Kim

Han

et al. 2017

Advances in Mechanical Engineering

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During the expansion forming of aluminum tube, the efficiency of heat exchanger diminishes due to the adhesion of groove and expansion ball inside the tube. Despite its importance, a limited number of researches on the adhesion problems in aluminum tube expansion have been published. This study aims to analyze the adhesion occurring during the expansion forming of aluminum tube for heat exchanger and to identify its location. For this, the method of using the statistical analysis of geometry by image processing and the slope of force measured from expansion forming was suggested. The new method discovers the adhesion location from the standard deviation of groove height measured before and after expansion of tube and the differentiation of force measured from expansion forming. To prove this method, the area with deviation of groove height above average was discovered, and it was confirmed that from the actual expansion of tube cross-sectional images, the height of some grooves was abnormally shorter due to adhesion. Also, from this method, it was confirmed that the changes in differentiation of force occurring from the expansion of the tube also include the information on adhesion location.

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Experimental and numerical characterization of a mechanical expansion process for thin-walled tubes

Cited by 14 publications

References 11 publications

The Role of the Process and Design Variables in Improving the Performance of Heat Exchanger Tube Expansion

The Role of the Process and Design Variables in Improving the Performance of Heat Exchanger Tube Expansion

Analysis of the mechanical expansion process of thin-walled tubes for air heat-exchanger production

A new methodology for detecting adhesion location in aluminum tube expansion

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