On Thermal Expansion Induced Stresses in U-Bends of Shell-and-Tube Heat Exchangers

An analytical method is herein developed to evaluate the stress field in the critical regions of a U-tube subject to differential thermal expansion. The solution is intended to be used as a design tool to conveniently study the variation of geometric parameters on the U-tube stress distribution. Those design variables which have significant effects on the structural characteristics of the U-tube are identified by an in-depth study of a typical example problem. Some effective design remedies are also discussed.

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Numerical Investigation on Effect of Thermal Expansion Joint in a Tube Holder Insulating Section in Shell and Tube Heat Exchanger

Mapta Journal of Mechanical and Industrial Engineering (MJMIE) ◽

10.33544/mjmie.v4i2.151 ◽

2021 ◽

Vol 4 (2) ◽

pp. 14-20

Author(s):

Amirhossein Khayyami nejad ◽

Hadi Amirshaghaghi ◽

Navid P.Khabazi ◽

Pourya Shadkami Ahvazi

Keyword(s):

Thermal Expansion ◽

Heat Exchangers ◽

Thermal Stresses ◽

Applied Pressure ◽

The Finite Element Method ◽

Expansion Joint ◽

Ansys Software ◽

Expansion Joints ◽

Tube Heat Exchanger ◽

Shell And Tube

As shell and tube heat exchangers become more widely used, their challenges are becoming more and more important. In some of these heat exchangers, an insulating section is used to reduce thermal stresses on the tube holder section. In this study, the effect of the presence and absence of expansion joints in this insulation section has been investigated. For this purpose, the desired section with and without expansion joint has been analyzed using the finite element method (FEM) in ANSYS software. Based on the results, it was found that the thermal expansion joint reduces thermal deformation and significantly reduces the rate of stresses in the mentioned section, which increases the life of the tube holder section. Also, the presence of expansion joints reduces the applied pressure to the insulation tape around the tube holder section, which increases the life of the insulation tape around the insulation section.

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An Improved Design of Threaded Closures for Screw Plug (Breech Lock) Heat Exchangers

Volume 1B: Codes and Standards ◽

10.1115/pvp2016-63137 ◽

2016 ◽

Author(s):

Haresh K. Sippy ◽

Dipak K. Chandiramani

Keyword(s):

Thermal Expansion ◽

Heat Exchangers ◽

Tube Bundle ◽

Pressure Vessels ◽

Typical Application ◽

Heat Transfer Efficiency ◽

Shrink Fitting ◽

Shell And Tube ◽

Improved Design ◽

Screw Threads

Threaded closures for pressure vessels have been in use for decades. Much work has been done to develop convenient, safe and economical threaded closures. Threaded closures are used when there is a need for opening the vessel either for maintenance or as part of its operation. Heat Exchangers are a typical application where there is a need for opening the vessel and cleaning the tubes at regular intervals to maintain the heat transfer efficiency. These are known as Breech Lock or Screw Plug Exchangers. These are basically U-tube exchangers. The channel side operates at high temperature and pressure and it has a threaded end closure. In some designs, the shell side may also be at high pressure. The tube bundle is removable without having to dismantle the channel or disconnect the nozzles from the pipeline. Thus screw plug exchangers help to reduce fabrication cost and reduce time for in-service maintenance. The major problem encountered with the use of such end closures are 1) Jamming of the threaded plug, due to deformation of the channel barrel. Thus the opening of the end closure by unscrewing becomes a difficult task. With the increase in operating temperatures and pressures, the problems become more severe, due to which, users are not inclined to use these type of end closures. A study was undertaken to assess the reasons for bulging of the end of the channel which caused jamming of the screw threads and also for leakage through the gasket. By shrink fitting a ring over the end of the channel, the deformation was reduced, enabling easy opening of the cover. 2) The leakage through the gasket between the shell and tubesheet, causing the intermixing of shell and tube-side fluids. This on analysing was found that the additional forces were acting on the gasket due to thermal expansion of the internals. This led to changing to a gasket that could withstand the forces and pressure. Leakage through the gasket was prevented by analysing the additional forces acting on the gasket due to thermal expansion of the internals and changing to a gasket that could withstand the forces and pressure.

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A Cost-Based Strategy to Design Multiple Shell and Tube Heat Exchangers

Journal of Heat Transfer ◽

10.1115/1.1643087 ◽

2004 ◽

Vol 126 (1) ◽

pp. 119-130 ◽

Cited By ~ 9

Author(s):

Raquel D. Moita ◽

Cristina Fernandes ◽

Henrique A. Matos ◽

Clemente P. Nunes

Keyword(s):

Heat Exchanger ◽

Heat Exchangers ◽

Current Flow ◽

Process Integration ◽

Design Algorithm ◽

Heat Exchanger Design ◽

Design Variables ◽

New Strategy ◽

Shell And Tube ◽

Feasible Space

Process Integration has been applied in several industrial processes mainly using standard shell and tube heat exchangers (1-1 or 1-2). The flow arrangement in 1-2 multiple shell and tube heat exchangers involves part counter-current flow and part co-current flow. This fact is accounted for in the design by introducing a FT correction factor into the 1-1 heat exchanger design equation. To avoid some steep regions in the feasible space of heat exchangers design some authors introduce other parameters like XP or G. Until now it was not possible to have an overall map to give some guidelines of how to choose between the several XP approaches established in the literature. This paper summarizes the current existing criteria in a general design algorithm DeAl12 to show a path for the calculations of the main design variables of the heat exchanger. Also a new strategy design algorithm StratDeAl12 is introduced in this paper to allow the best choice between the existing XP approaches based on the heat exchanger cost minimisation. Several examples illustrate the advantage of using the developed algorithm and the deviations obtained in the heat exchanger cost if a wrong approach was chosen.

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Temperature Field Prediction of Rectangular Shell-and-Tube Heat Exchanger

Journal of Pressure Vessel Technology ◽

10.1115/1.4024437 ◽

2013 ◽

Vol 135 (6) ◽

Cited By ~ 1

Author(s):

J. F. Zhou ◽

Y. Li ◽

B. Q. Gu ◽

C. L. Shao

Keyword(s):

Thermal Expansion ◽

Temperature Field ◽

Heat Exchanger ◽

Heat Exchangers ◽

Operating Conditions ◽

Shell Side ◽

Tube Heat Exchanger ◽

Shell And Tube ◽

Side Flow ◽

Rectangular Shell

Shell-and-tube heat exchangers are the most common type of heat exchangers in oil refineries and other large chemical processes. In this manuscript, we demonstrate that the shell-side flow in a cylindrical shell was not as homogeneous as that in a rectangular shell. According to the periodic flow field and the arrangement of tubes in the rectangular shell, the solid-fluid coupling heat transfer model consisting of a single tube section and the outer and inner fluids was developed to represent the whole heat exchanger. Using this model, the relationship among four temperatures, namely the inlet and outlet temperatures of tube-side fluid and the upstream and downstream temperatures of shell-side fluid, was established. By dividing each tube into several tube sections at the sites of baffles, a method for predicting the temperature field of the rectangular shell-and-tube heat exchanger was proposed. Based on the node temperature correlation, all the node temperatures were obtained by iterative computation using the established relationship between the four temperatures and the operating conditions. It was found that the temperature distribution of the fluid in tube was approximately linear along axial direction, but the temperature of tube showed nonlinear regularity. The axial deformation compatibility condition for the tube bundle and shell was considered when resolving the stresses in tubes. For the model established in this paper, the mean temperature of the tube at lower position was found to be larger than that at higher position; hence the thermal expansion of the tube at the lower end is larger. In the case the tube-side fluid was heated, all tubes were pulled because of the larger axial thermal expansion of shell, and the stress in the tube with higher temperature is smaller because of the smaller strain.

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