scholarly journals Investigation on the Micromechanisms of the Cracking of 316L Heat Exchanger Tubes

2021 ◽  
Author(s):  
Hui Xu ◽  
Lulu Fang ◽  
Qiaofeng Ding ◽  
Yanjun Guo ◽  
Xiaohui Li ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Chloride Ion ◽  
Service Condition ◽  
Outer Wall ◽  
Optical Microscope ◽  
Point Of View ◽  
Standard Requirement ◽  
Crack Morphology ◽  
Cracking Mechanisms ◽  
Corrosion Pits

The cracking mechanisms of 316L heat exchanger tubes employed in power station were studied using optical microscope (OM) and scanning electron microscope (SEM). It is demonstrated that the hardness value, microstructure and tensile properties of selected #1 and #2 tube samples all meet the requirements of relevant standards, but the contents of Ni and Mo element of #1 tube are slightly lower than the standard requirements. The circumferential cracks on the two samples nucleate at the corrosion pits on the inner wall of the tubes, while Cl element was detected in the corrosion products of these pits. The cracks propagate from the inner wall to the outer wall along the circumferential direction of the tube, forming a dendritic crack morphology with both transgranular and intergranular propagation characteristics. Combined with the investigation of the service condition of the heat exchanger tubes and the analysis of the experimental results, it can be concluded that the main reason for cracking is the initiation of pin-corrosion when the content of chloride ion exceeds the standard during the service of the tubes, which will induce stress corrosion cracking, causing crack expansion through the wall thickness, and finally lead to leakage of the tube. In addition, from the point of view of materials, Mo is an important element to improve the pitting resistance of materials. The content of Mo element detected in the samples is lower than the standard requirement, which is also one of the reasons for the easy pitting corrosion of the inner wall of the pipe.

Optimization and Standardization of Flanged and Flued Expansion Joint Design

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Kamlesh M. Chikhaliya ◽  
Bhaveshkumar P. Patel
Keyword(s):  
Heat Exchanger ◽  
Optimum Design ◽  
Design Methodology ◽  
Thick Wall ◽  
Process Conditions ◽  
Expansion Joint ◽  
Standard Requirement ◽  
Spring Rate ◽  
Tube Heat Exchanger ◽  
Heat Exchanger Design

Flanged and flued type expansion joint (thick wall expansion bellow) used as an integral part of many shell and tube heat exchanger where process conditions produce differential expansion between shell and tubes. It provides flexibility for thermal expansion and also functions as a pressure retaining part. Design of expansion joints is usually based on trial and error method in which initial geometry must be assumed, and accordingly maximum stresses and spring rate are be calculated. Inadequate selection of geometry leads to higher tubesheet and bellow thickness, which increases cost of equipment. This paper presents standardization and optimum design approach of flange and flued expansion bellow fulfilling ASME VIII-1 and TEMA standard requirement. Methodology to define expansion bellow geometry is developed, and geometry dimensions are tabulated for expansion bellow diameter from 300 to 2000 mm and thickness from 6 to 30 mm. Each defined geometry is analyzed using finite element method, and maximum von Mises stresses are calculated for bellow axial displacement from 0.5 to 1.5 mm and internal pressure from 0.1 to 6.5 MPa. Spring rate is also calculated for each defined geometry for consideration in tubesheet calculation. Accordingly, optimum design methodology is developed, tested, and compared with existing design. Results depicted that proposed standardization approach and design methodology will optimize expansion bellow and tubesheet thickness and will also save considerable time in finalization of heat exchanger design.

Thermodynamic Estimate of Minimal Dissipation for Heat Exchange System

2008 ◽  
Author(s):  
Andrei A. Akhremenkov ◽  
Anatoliy M. Tsirlin ◽  
Vladimir Kazakov
Keyword(s):  
Heat Exchanger ◽  
Heat Exchange ◽  
Heat Load ◽  
Point Of View ◽  
Exchange System ◽  
Heat Exchange System ◽  
Heat Exchange Surface ◽  
Minimal Dissipation ◽  
The Difference ◽  
Exchange Surface

In this paper we consider heat exchange system from point of view of Finite-time thermodynamics. At first time the novel estimate of the minimal entropy production in a general-type heat exchange system with given heat load and fixed heat exchange surface is derived. The corresponding optimal distribution of heat exchange surface and optimal contact temperatures are also obtained. It is proven that if a heat flow is proportional to the difference of contacting flows’ temperatures then dissipation in a multi-flow heat exchanger is minimal only if the ratio of contact temperatures of any two flows at any point inside heat exchanger is the same and the temperatures of all heating flows leaving exchanger are also the same. Our result based on those assumptions: 1. heat transfer law is linear (17); 2. summary exchange surface is given; 3. heat load is given; 4. input tempretures for all flows are given; 5. water equivalents for all flows are given.

Optimized Chaotic Heat Exchanger Configurations for Process Industry: A Numerical Study

2013 ◽  
Author(s):  
Akram Ghanem ◽  
Thierry Lemenand ◽  
Dominique Della Valle ◽  
Hassan Peerhossaini
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Process Intensification ◽  
Point Of View ◽  
Square Duct ◽  
Square Channel ◽  
Duct Geometry

A numerical investigation of chaotic laminar flow and heat transfer in isothermal-wall square-channel configurations is presented. The computations, based on a finite-volume method with the SIMPLEC algorithm, are conducted in terms of Péclet numbers ranging from 7 to 7×105. The geometries, based on the split-and-recombine (SAR) principle, are first proposed for micromixing purposes, and are then optimized and scaled up to three-dimensional minichannels with 3-mm sides that are capable of handling industrial fluid manipulation processes. The aim is to assess the feasibility of this mass- and heat-transfer technique for out-of-laboratory commercial applications and to compare different configurations from a process intensification point of view. The effects of the geometry on heat transfer and flow characteristics are examined. Results show that the flux recombination phenomenon mimicking the baker’s transform in the SAR-1 and SAR-2 configurations produces chaotic structures and promotes mass transfer. This phenomenon also accounts for higher convective heat transfer exemplified by increased values of the Nusselt number compared to the chaotic continuous-flow configuration and the baseline plain square-duct geometry. Energy expenditures are explored and the overall heat transfer enhancement factor for equal pumping power is calculated. The SAR-2 configuration reveals superior heat-transfer characteristics, enhancing the global gain by up to 17-fold over the plain duct heat exchanger.

Corrosion behavior of heat-treated and cryorolled Al 5052 alloys in different chloride ion concentrations

2020 ◽  
Vol 67 (1) ◽  
pp. 7-15 ◽  
Author(s):  
Anasyida Abu Seman ◽  
Ji Kit Chan ◽  
Muhammad Anas Norazman ◽  
Zuhailawati Hussain ◽  
Dhindaw Brij ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Corrosion Behaviour ◽  
Solution Treatment ◽  
Chloride Ion ◽  
Optical Microscope ◽  
Al Alloy ◽  
Content Type ◽  
Ion Concentrations ◽  
Heat Treated ◽  
Chloride Environment

Purpose This paper aims to investigate the corrosion behaviour of heat-treated and cryorolled Al 5052 alloys in different Cl− ion concentrations. Design/methodology/approach NaCl solutions with concentrations of 0, 0.5, 3.5 and 5.5 per cent were selected. Samples were subjected to pre-heat treatment (annealing at 300 °C and solution treatment at 540 °C) and cryorolling up to 30 per cent reduction before undergoing corrosion tests. The corrosion behaviour of the samples was then investigated by potentiodynamic polarization. The microstructure of the corroded samples was evaluated under an optical microscope, and the percentages of pits on their surfaces were calculated. Findings The cryorolled samples had a lower corrosion rate than the samples that were not cryorolled. The cryorolled sample that underwent solution treatment showed the highest corrosion resistance among all the samples tested. Practical implications The commercial impact of the study is the possibility of using the cryorolled Al alloy in various ion chloride environment. Originality/value The obtained results help in understanding the corrosion behaviour of cryorolled samples under different heat treatment conditions.

Generation of Longitudinal Streamwise Vortices—A Device for Improving Heat Exchanger Design

1994 ◽  
Vol 116 (3) ◽  
pp. 588-597 ◽  
Author(s):  
G. Biswas ◽  
P. Deb ◽  
S. Biswas
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Delta Wing ◽  
Rectangular Channel ◽  
Point Of View ◽  
Vortex Generators ◽  
Pair Type ◽  
Longitudinal Vortices ◽  
Flat Surfaces ◽  
Heat Exchanger Design

Laminar flow and heat transfer characteristics in a rectangular channel, containing built-in vortex generators of both the slender delta-wing and winglet-pair type, have been analyzed by means of solution of the full Navier–Stokes and energy equations. Each wing or winglet pair induces the creation of streamwise longitudinal vortices behind it. The spiraling flow of these vortices serves to entrain fluid from their outside into their core. These vortices also disrupt the growth of the thermal boundary layer and serve ultimately to bring about the enhancement of heat transfer between the fluid and the channel walls. The geometric configurations considered in the study are representative of single elements of either a compact gas-liquid fin-tube crossflow heat exchanger or a plate-fin crossflow heat exchanger. Physically, these vortex generators can be mounted on the flat surfaces of the above-mentioned heat exchangers by punching or embossing the flat surfaces. They can also act as spacers for the plate fins. Because of the favorable pressure gradient in the channel, the longitudinal vortices are stable and their influence persists over an area many times the area of the slender vortex generators. From a heat transfer point of view, the delta-wing generator is found to be more effective than the winglet-pair. However, most convective heat transfer processes encounter two types of loss, namely, losses due to fluid friction and those due to heat transfer across finite temperature gradient. Because these two phenomena are manifestations of irreversibility, an evaluation of the augmentation techniques is also made from a thermodynamic viewpoint. Conclusions that are drawn thus include discussion about the influence of vortex generators (wings/winglets) on irreversibility.

scholarly journals The influence of sodium chlorides fog on corrosion resistance of heat exchangers used in automotive

2017 ◽  
Vol 37 (1) ◽  
pp. 45-49
Author(s):  
Katarzyna Peta ◽  
Karol Grochalski ◽  
Adam Piasecki ◽  
Jan Żurek
Keyword(s):  
Corrosion Resistance ◽  
Heat Exchanger ◽  
Sodium Chloride ◽  
Chemical Composition ◽  
Light Microscopy ◽  
Heat Exchangers ◽  
Winter Season ◽  
Road Maintenance ◽  
Critical Areas ◽  
Corrosion Pits

AbstractIn the work, the most important factors which influence on the exploitative durability of heat exchangers are classified. Particular attention was paid to the compounds of sodium chloride used in the winter season for road maintenance. In order to determine their impact on automotive heat exchanger corrosion resistance, a test of heaters in a salt chamber which imitates the conditions of their work was realized. It also allows to verify the durability of these products. To evaluate the corrosion changes, observation with the use of light microscopy and scanning microscopy SEM were made supplemented with microanalysis of chemical composition by EDS spectroscopy method. Critical areas in the heat exchangers which are mostly exposed to damage including the formation of local corrosion pits were located and analyzed.

scholarly journals Simulasi dinamik sistem reaktor eksotermal adiabatik dengan alat penukar panas umpan-keluaran (FEHE)

2018 ◽  
Vol 5 (3) ◽  
pp. 513
Author(s):  
Tri P. Adhi ◽  
Gandi R. Setyadi
Keyword(s):  
Steady State ◽  
Heat Exchanger ◽  
Point Of View ◽  
Operational Parameter ◽  
Steady State Condition ◽  
Stable Case ◽  
Aspen Hysys ◽  
Mathematical Correlation ◽  
Operational Temperature ◽  
Process Operation

A study of dinamics behavior on adiahatic exothermal reactor with a Feed-Effluent Heat Exchanger (FEHE) is reported in this paper. In practice of a chemical proces industries, configuration of the heat integration of FEHE system are easi to found at process that involving adiabatic exothermal reactor with the demand of feed's heating and of reactor product's cooling. The FEHE system configuration increase the process thermal efficiency throught the use of heat flow on the reactor product to raise the temperature of reactor feed flow. From the steady state economical point of view, this off cource be very interesting to be implemented, althought controlling and operational considerations are need to be taken into account to keep those advantages un-eliminted by operational and controlling matters. The dynamic simulation can give some illustration on how the hehavior of process operation at FEHE system is. Dynamically this system can be examined so that the boundary of operational parameter which could mantain its stability and trigger unstable system can be known and determined. In this study, the simulation of dynamic and steady state condition on system of FEHE-adiabatic exothermal reactor has been performed by assist of process simulator Aspen-Hysys using ammonia synthesis as the model process. The examined un-stable case were the harmonic osilation phenomena on the operational temperature condition. The objective of this study was to obtain a mathematical correlation model that can be applied in predicting when the un-stable phenomena might be happen.Keywords: FEHE System, Oscillation Temperature, Unstabilize Operation  AbstrakSebuah kajian mengenai kelakuan dinamik sistem reaktor eksothermal adiabatik dengan alat pertukaran panas umpan-keluaran (Feed-Effluent Heat Exchanger, FEHE) disampaikan pada makalah ini. Dalam praktek industri proses kimia, konfigurasi integrasi pwws   sistem  FEHE mudah   ditemukan   pada    proses   yang    melihatkan    reaktor   eksothermal   adiahatik,   dengan kehutuhan pemmw.\·anlfiiiJHIII   reaktor dan pendinginan produk reakt01 Konfigurasi sistem FEHE memherikan  pening/wtan   efisiensi  thermal  proses   melalui  pemanfctatan   a/iran  panas  produk reaktor untuk  menaikkan  tempera fur  a/iran umpan reakt01  Dari sudut pmzdang  ekonomi sistem tunak,   lentu   saja   hal   tersehut   sangat   menarik    1111/uk   diimplemen/asilwn,    a/am   tetapi pertimhangan-pertimhangan    operasi  dan pengendalian   harus  diperhatikan  agar  keuntungan  ini tidak  lere/iminasi  oleh permasalahan-permasalahan   pengendalian   dan pengoperasian.   Simulasi dinamik  dapat  memherilwn  gmnbaran  hagaimana  kelalwan  operasi proses  pada  sistem  FEHE. Secara  dinamik,  sistem  ini dapat  diuji  sehingga  batas-batas  parameter   operasi vang  menjaga kestahilan  danmemicu  ketidakstahilan  dari sis/em  dapat diketaluti  dan ditentukan. Dalam  kajiwz ini simulasi  kondisi  lunak  dan  dinamik. sistem  reaktor  eksothermal  adiahatik-FEHE  dilakukan dengan  hantzwn  simulator  proses  Aspen-Hv.1ys  dengan  mengamhil  sintesi.1·  amoniak  sehagai model  proses.   Kasus  ketidak-stabilan  yang   dikaji  adalah jetwmena    osilasi  harmonik  kondisi tenzperatur operasi.  Tujuan yang  hendak dicapai dari kajian ini adalah untuk mendapatkan  suatu model  korelasi   matematik  yang   dapal  digunalwn   untuk  mcmprediksi  kapan  saat   terjadinyafenomena   ketidak-stahilanlersehut.Kata kunci: Ketidak-stabilan Operasi, Osilasi Temperatur, Sistem FEHE

scholarly journals Investigation of heat transfer enhancement in an annular conduit with angled fins using functionalized GNP colloidal suspension

2021 ◽  
Vol 945 (1) ◽  
pp. 012058
Author(s):  
Sayshar Ram Nair ◽  
Cheen Sean Oon ◽  
Ming Kwang Tan ◽  
S.N. Kazi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Colloidal Suspension ◽  
Industrial Applications ◽  
Point Of View ◽  
Solid Particles ◽  
Working Fluid

Abstract Heat exchangers are important equipment with various industrial applications such as power plants, HVAC industry and chemical industries. Various fluids that are used as working fluid in the heat exchangers such as water, oil, and ethylene glycol. Researchers have conducted various studies and investigations to improve the heat exchanger be it from material or heat transfer point of view. There have been attempts to create mixtures with solid particles suspended. This invention had some drawbacks since the pressure drop was compromised, on top of the occurrence of sedimentation or even erosion, which incurs higher maintenance costs. A new class of colloidal suspension fluid that met the demands and characteristics of a heat exchanger was then created. This novel colloidal suspension mixture was then and now addressed as “nanofluid”. In this study, the usage of functionalized graphene nanoplatelet (GNP) nanofluids will be studied for its thermal conductivity within an annular conduit with angled fins, which encourage swirling flows. The simulation results for the chosen GNP nanofluid concentrations have shown an enhancement in thermal conductivity and heat transfer coefficient compared to the corresponding base fluid thermal properties. The data from this research is useful in industrial applications which involve heat exchangers with finned tubes.

Failure Analysis of Cracked and Corroded Tubings in Sudong Block of Changqing Oilfield

2021 ◽  
Vol 1035 ◽  
pp. 638-646
Author(s):  
Xue Hui Zhao ◽  
Ming Xing Li ◽  
Jun Lin Liu ◽  
Man Liu
Keyword(s):  
Pitting Corrosion ◽  
Mechanical Damage ◽  
Outer Wall ◽  
Fracture Morphology ◽  
Internal Corrosion ◽  
Primary Condition ◽  
Tubing String ◽  
Result Show ◽  
Corrosion Pits ◽  
Macroscopic Analysis

In the process of layer inspection and hole mending, it was found that the corrosion of tubing in a well was serious, and perforation and fracture occurred. Part of the tubing was found to be cracked from the failed pipe samples, and relatively serious pitting corrosion pits were found on the surface of the outer wall. The fracture morphology and corrosion products were analyzed by means of macroscopic analysis and metallographic microscope, SEM and EDS. The result show that the mechanical damage of the outer wall of the tubing was the primary condition for accelerating corrosion, and the severe corrosion thinning of the inner and outer walls of the tubing was the main reason for the failure of the tubing string. The corrosion perforation of tubing was mainly caused by internal corrosion.

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