scholarly journals Comparison of performance of shell-and-tube heat exchangers with plain and annular-finned tube bundle

2017 ◽  
Author(s):  
Asif Ahmed ◽  
Anuruddha Bhattacharjee ◽  
Sumon Saha
Keyword(s):  
Heat Exchangers ◽  
Tube Bundle ◽  
Finned Tube ◽  
Shell And Tube

A numerical study of heat transfer in the in-line tube bundle under pulsating fluid flow conditions

Vestnik IGEU ◽  
2019 ◽  
pp. 12-21
Author(s):  
A.I. Khaibullina ◽  
A.R. Khairullin
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Numerical Study ◽  
Tube Bundle ◽  
Cross Flow ◽  
Pulsating Flow ◽  
Operating Parameters ◽  
Flow Conditions ◽  
Study Results ◽  
Shell And Tube

Shell-and-tube heat exchangers are widely used in different industries. Even a small increase in the efficien-cy of shell-and-tube heat exchangers can lead to significant energy savings. One of the ways to improve the efficiency of shell-and-tube heat exchangers is the use of pulsating flows for the enhancement of heat ex-change. Despite the fact that heat transfer in the tube bundle cross flow in steady-state conditions has been studied quite well, there is limited data on heat transfer in pulsating flow, which means that the problem of finding regularities of heat transfer with pulsating flows in tube bundles is still important. The work employs the incompressible Reynolds averaged Naviere-Stokes (URANS) equations and the continuity equation. Heat transfer is described by the convective heat transfer (Fourier-Kirchhoff) equation. The calculations are performed using Ansys Fluent. A numerical study has been conducted of the effects of forced asymmet-rical pulsating flow on heat exchange in in-line tube bundle cross-flow conditions. In the numerical experi-ment the Reynolds number Re ranged from 1000 to 2000, the relative pulsating amplitude A/D – from 1 to 2, the Strouhal number Sh – from 0,77 to 1,51, the Prandtl number and the duty cycle had fixed values: Pr = 7,2,  = 0,25. The relative transverse and longitudinal pitch was s1,2/D = 1,3. It has been found that pulsating flows lead to the enhancement of heat transfer in the whole range of the studied operating parameters. An increase in A/D and Sh leads to bigger Nusselt number Nu. An increase in the Re number leads to a de-crease in the Nu ratio in pulsating and steady flow conditions. The general correlation obtained based on the numerical study results can be used to predict heat transfer in a pulsating flow in the range of the studied geometric and operating parameters. More research is needed to predict heat transfer in a wider range of operating parameters and with other tube bundle configurations.

Numerical Analytic Approach to a Calculation of a Thermal Stress State of Shell and Tube Heat Exchangers

2013 ◽  
Author(s):  
Igor Laskin ◽  
Boris Volfson
Keyword(s):  
Numerical Modeling ◽  
Heat Exchangers ◽  
Analytic Solution ◽  
Tube Bundle ◽  
Shell Elements ◽  
Analytic Methods ◽  
Distribution Calculation ◽  
Element Simulation ◽  
Shell And Tube ◽  
Comparison Of The Results

Nowadays, a stress calculation of shell and tube heat exchangers’ elements is based either on analytic methods described in ASME, TEMA, EN, GOST and other standards or on numerical modeling using FEA. The main disadvantage of the analytic methods is that they can be applied only to certain apparatuses’ designs and it is very difficult or even impossible to use them with non-typical constructions. Otherwise, such a calculation is easy to perform with modeling by FEA. However, a direct finite element simulation of several thousands of tubes, which can be designed in one heat exchanger, makes the task very time-consuming and the resulting model very big and computation-intensive. This paper examines a typical model, which includes 3.5 million nodes and more than 3 million elements. We offer a numerical analytic solution of this task, which consists in modeling of a tube bundle by an orthotropic continuum with equivalent properties. The comparison of the results of a temperature distribution calculation and the stress-strain distribution calculation using direct numerical modeling of the tubes in the tube bundle by shell elements from one hand, and of the suggested numerical analytic solution from another, shows that these results do match closely enough to practice.

Flow-Induced Vibration in Spiral Finned Gas Tube Bundle Heat Exchangers

2003 ◽  
Author(s):  
Michael Fischer
Keyword(s):  
Heat Exchangers ◽  
Tube Bundle ◽  
Practical Importance ◽  
Acoustic Resonance ◽  
Finned Tube ◽  
Flow Induced Vibration ◽  
Finned Tubes ◽  
The Past ◽  
Short Period ◽  
Fluidelastic Instability

In the past finned tube bundle heat exchangers were often subject of severe damages due to flow-induced vibration followed by high amounts of loss for the operator. A case of practical importance is the design of spiral finned gas tube bundle heat exchangers that still have been investigated in literature only seldom. Both acoustic resonance and fluidelastic instability can lead to tube rupture within a short period of operation. In this paper analytic calculation methods for tube Eigenfrequencies are extended to spiral finned tubes. The results are in agreement with static and vibrational experiments. Stability criteria for fluidelastic instability are derived by flow channel experiments extending Connor’s equation to the design of spiral finned tube bundles. A number of cases of damage is described. The importance of correct damping values is demonstrated. The scheme reported in this paper is able to avoid damages in spiral finned tube bundle heat exchangers due to fluidelastic instability.

Fluidelastic and Vortex Induced Vibration of a Finned Tube Array

2002 ◽  
Author(s):  
Kazuo Hirota ◽  
Tomomichi Nakamura ◽  
Hirohiko Kikuchi ◽  
Kazunori Isozaki ◽  
Hirotaka Kawahara
Keyword(s):  
Heat Exchangers ◽  
Tube Bundle ◽  
Acoustic Resonance ◽  
Finned Tube ◽  
Flow Induced Vibration ◽  
Design Guideline ◽  
Vortex Induced Vibration ◽  
Finned Tubes ◽  
Critical Velocities ◽  
Vibration Tests

Fluidelastic and vortex induced vibration are important problems in operating heat exchangers. Many studies have been conducted to solve the problems. As a result, design guideline has already existed for the flow-induced vibration of a tube bundle. On the other hand, some kinds of heat exchanger use finned tube array in order to improve the efficiency of the heat transfer. For finned tube array, some studies for vortex induced acoustic resonance have been conducted, where Strouhal numbers are obtained. However fluctuating lift coefficients due to vortex are important from the viewpoint of tube vibration. Moreover, critical velocities for fluidelastic vibration are also important. In this study, fluidelastic and vortex induced vibration tests were conducted for a triangular finned tube array. Two different frequencies of the vortex shedding were observed. For this tube array, Strouhal numbers were 0.13–0.15, 0.37–0.39. However vortex induced forces were too weak to excite the finned tubes. For this tube array, averaged Connors’ constant K was 6.8.

Shellside Waterflow-Induced Tube Vibration in Heat Exchanger Configurations With Tube Pitch-to-Diameter Ratio of 1.42

1989 ◽  
Vol 111 (4) ◽  
pp. 441-449 ◽  
Author(s):  
H. Halle ◽  
J. M. Chenoweth ◽  
M. W. Wambsganss
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Tube Bundle ◽  
Diameter Ratio ◽  
Design Parameters ◽  
Comprehensive Investigation ◽  
Flow Area ◽  
Shell And Tube ◽  
Vibration Coupling ◽  
Tube Pitch

The pitch-to-diameter ratio (P/D) of the tube layout in shell-and-tube heat exchangers is one of the major parameters with which the designer may control heat transfer and pressure drop and facilitate mechanical cleaning. As part of a comprehensive investigation of waterflow-induced tube vibration in an industrial-size research heat exchanger, various configurations characterized by different design parameters, including P/D ratio, had been investigated. To provide a comparison with previous data obtained with P/D = 1.25, this paper presents the results of a study of eight different tube bundle configurations with P/D = 1.42. Four equilaterally spaced tube layout patterns and two baffle edge orientations were investigated. The results indicate that the greater flow area of the P/D = 1.42 configuration increases flow penetration into the bundle, reduces the tube-to-tube vibration coupling and generally provides less well-defined, even though sometimes improved, fluidelastic instability thresholds.

An Experimental Study of Shell-and-Tube Heat Exchangers With Continuous Helical Baffles

2007 ◽  
Vol 129 (10) ◽  
pp. 1425-1431 ◽  
Author(s):  
B. Peng ◽  
Q. W. Wang ◽  
C. Zhang ◽  
G. N. Xie ◽  
L. Q. Luo ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Tube Bundle ◽  
Shell Side ◽  
Helical Baffle ◽  
Shell And Tube

Two shell-and-tube heat exchangers (STHXs) using continuous helical baffles instead of segmental baffles used in conventional STHXs were proposed, designed, and tested in this study. The two proposed STHXs have the same tube bundle but different shell configurations. The flow pattern in the shell side of the heat exchanger with continuous helical baffles was forced to be rotational and helical due to the geometry of the continuous helical baffles, which results in a significant increase in heat transfer coefficient per unit pressure drop in the heat exchanger. Properly designed continuous helical baffles can reduce fouling in the shell side and prevent the flow-induced vibration as well. The performance of the proposed STHXs was studied experimentally in this work. The heat transfer coefficient and pressure drop in the new STHXs were compared with those in the STHX with segmental baffles. The results indicate that the use of continuous helical baffles results in nearly 10% increase in heat transfer coefficient compared with that of conventional segmental baffles for the same shell-side pressure drop. Based on the experimental data, the nondimensional correlations for heat transfer coefficient and pressure drop were developed for the proposed continuous helical baffle heat exchangers with different shell configurations, which might be useful for industrial applications and further study of continuous helical baffle heat exchangers. This paper also presents a simple and feasible method to fabricate continuous helical baffles used for STHXs.

Vibration of Tube Bundles Subjected to Two-Phase Cross-Flow

1985 ◽  
Vol 107 (4) ◽  
pp. 335-343 ◽  
Author(s):  
M. J. Pettigrew ◽  
J. H. Tromp ◽  
J. Mastorakos
Keyword(s):  
Heat Exchangers ◽  
Tube Bundle ◽  
Cross Flow ◽  
Elastic Instability ◽  
Steam Generators ◽  
Two Phase ◽  
Vibration Excitation ◽  
Mass Fluxes ◽  
Excitation Mechanisms ◽  
Shell And Tube

Two-phase cross-flow exists in many shell-and-tube heat exchangers such as condensers, reboilers and nuclear steam generators. Thus we are conducting a comprehensive program to study tube bundle vibrations subjected to two-phase cross-flow. This paper presents the results of experiments on a normal-triangular and a normal-square tube bundle, both of p/d = 1.47. The bundles were subjected to air-water mixtures to simulate realistic vapor qualities and mass fluxes. Vibration excitation mechanisms were deduced from vibration response measurements. Results on damping, hydrodynamic mass, fluid-elastic instability and random turbulence excitation in two-phase cross-flow are presented.

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

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.

Sign in / Sign up

Export Citation Format

Share Document