Maintenance and Cleaning of Heat Exchangers

2018 ◽  
Vol 919 ◽  
pp. 396-403
Author(s):  
Jiří Kuchař ◽  
Viktor Kreibich ◽  
Vladimir Agartanov ◽  
Milan Petřík
Keyword(s):  
Heat Exchangers ◽  
Internal Surface ◽  
Surface Cleaning ◽  
Corrosion Products ◽  
Mineral Deposits ◽  
Chemical Cleaning ◽  
Heating Systems ◽  
Physico Chemical ◽  
Inner Surface ◽  
Cleaning Methods

Each machine and energetic equipment needs maintenance or cleaning time. Energetic equipment needs more regular cleaning so it works well and reliably, and the heat transfer is permanent and there is no energy loss. The inner surface of heating systems are successively covering during their operation, due to the chemical and physico-chemical reactions, solid, some dirt, minerals and corrosion products. It is therefore advisable to regularly clean and service these devices. The article deals with the distribution of exchangers, formation of sediments and corrosion products associated with their operation. In addition, the article describes the types of internal surface cleaning methods. The whole article ends with a chemical cleaning experiment, where the heat exchanger clogged with mineral deposits was cleaned. The defectoscopic images show how the chemical can remove all deposits and restore the exchanger flow to its original state.

TEM characterization of silicon epitaxial layer grown on Si-TaS2, eutectic composites

1991 ◽  
Vol 49 ◽  
pp. 802-803
Author(s):  
C.M. Sung ◽  
M. Levinson ◽  
M. Tabasky ◽  
K. Ostreicher ◽  
B.M. Ditchek
Keyword(s):  
Substrate Surface ◽  
Bulk Sample ◽  
Surface Cleaning ◽  
Native Oxide ◽  
Czochralski Growth ◽  
Ion Milling ◽  
Cross Sectional ◽  
Cleaning Methods ◽  
Field Emission Cathodes

Directionally solidified Si/TaSi2 eutectic composites for the development of electronic devices (e.g. photodiodes and field-emission cathodes) were made using a Czochralski growth technique. High quality epitaxial growth of silicon on the eutectic composite substrates requires a clean silicon substrate surface prior to the growth process. Hence a preepitaxial surface cleaning step is highly desirable. The purpose of this paper is to investigate the effect of surface cleaning methods on the epilayer/substrate interface and the characterization of silicon epilayers grown on Si/TaSi2 substrates by TEM.Wafers were cut normal to the <111> growth axis of the silicon matrix from an approximately 1 cm diameter Si/TaSi2 composite boule. Four pre-treatments were employed to remove native oxide and other contaminants: 1) No treatment, 2) HF only; 3) HC1 only; and 4) both HF and HCl. The cross-sectional specimens for TEM study were prepared by cutting the bulk sample into sheets perpendicular to the TaSi2 fiber axes. The material was then prepared in the usual manner to produce samples having a thickness of 10μm. The final step was ion milling in Ar+ until breakthrough occurred. The TEM samples were then analyzed at 120 keV using the Philips EM400T.

Development of high k/III-V (InGaAs, InAs, InSb) structures for future low power, high speed device applications

2013 ◽  
Vol 1538 ◽  
pp. 291-302
Author(s):  
Edward Yi Chang ◽  
Hai-Dang Trinh ◽  
Yueh-Chin Lin ◽  
Hiroshi Iwai ◽  
Yen-Ku Lin
Keyword(s):  
Low Power ◽  
Leakage Current ◽  
High Speed ◽  
High Performance ◽  
Gate Oxide ◽  
Chemical Cleaning ◽  
Low Leakage ◽  
Low Leakage Current ◽  
High K ◽  
Cleaning Methods

ABSTRACTIII-V compounds such as InGaAs, InAs, InSb have great potential for future low power high speed devices (such as MOSFETs, QWFETs, TFETs and NWFETs) application due to their high carrier mobility and drift velocity. The development of good quality high k gate oxide as well as high k/III-V interfaces is prerequisite to realize high performance working devices. Besides, the downscaling of the gate oxide into sub-nanometer while maintaining appropriate low gate leakage current is also needed. The lack of high quality III-V native oxides has obstructed the development of implementing III-V based devices on Si template. In this presentation, we will discuss our efforts to improve high k/III-V interfaces as well as high k oxide quality by using chemical cleaning methods including chemical solutions, precursors and high temperature gas treatments. The electrical properties of high k/InSb, InGaAs, InSb structures and their dependence on the thermal processes are also discussed. Finally, we will present the downscaling of the gate oxide into sub-nanometer scale while maintaining low leakage current and a good high k/III-V interface quality.

Design and testing of energy-efficient heat exchangers for Newtonian and non-Newtonian fluids – A review

2021 ◽  
pp. 095765092110470
Author(s):  
Jayesh P ◽  
Mukkamala Y ◽  
Bibin John
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Exchangers ◽  
Internal Surface ◽  
Surface Modifications ◽  
Newtonian Fluids ◽  
Tube Surface ◽  
Pumping Power ◽  
Transfer Enhancement ◽  
The Impact

Heat transfer enhancement, pumping power and weight minimization in enhanced heat exchangers has long been achieved by deploying tubes with internal surface modifications like microgrooves, ribs, fins, knurls, and dimples with and without tube inserts. This article presents a very extensive review of experimental and computational studies on heat transfer enhancement, which covers convectional and unconventional working fluids under different fluid flow conditions. Compound augmentation with tube surface modifications and inserts has yielded enhancements in the overall heat transfer coefficient of over 116% in the fully developed turbulent flow regime. Exotic fluids like nano-coolants deployed in spiral grooved mircofin tubes yielded 196% enhancement in tube side heat transfer rate for concentrations as low as 0.5% by volume, while the thermal efficiency index measuring the overall enhancement in relation to the pumping power was 75%. However, reviews that address the combined effect of unconventional fluids, surface modifications and tube inserts on the overall thermo-hydraulic performance of annular heat exchangers seem to be limited. Further, nano-coolants aren’t frequently used in the process industry. The goal of this study is to document and evaluate the impact of cost-effective and energy-saving passive enhancement techniques such as tube surface modifications, tube inserts, and annular enhancement techniques on annular heat exchangers used in the process industries with Newtonian and non-Newtonian fluids. This review should be useful to engineers, academics and medical professionals working with non-Newtonian fluids and enhanced heat exchangers.

Flexure based gripper to grasp hollow objects by internal surface interaction

2021 ◽  
pp. 095440622110498
Author(s):  
Rajesh Kumar ◽  
Harsh Yadav ◽  
Varan Gupta ◽  
Jitendra P Khatait
Keyword(s):  
Internal Surface ◽  
Surface Interaction ◽  
Design Development ◽  
Friction Forces ◽  
Normal Forces ◽  
Inner Surface

The paper focuses on the design, development, and evaluation of a gripper intended to hold hollow objects by interacting with the inner surface. The gripper moves towards the inside of the hollow object and grips it using the friction forces applied on the surface of the object. The design also ensures the application of variable normal forces on the surface of the object to be grasped. The mathematical architecture is verified using prototypes and experiments.

Influence of Inner Surface Defects on the Fatigue Strength of Pipe Subjected to Cyclic Internal Pressure

1978 ◽  
Vol 100 (4) ◽  
pp. 360-368
Author(s):  
Y. Yazaki ◽  
S. Hashirizaki ◽  
S. Nishida ◽  
C. Urashima
Keyword(s):  
Fatigue Strength ◽  
Internal Pressure ◽  
Test Specimen ◽  
Surface Defects ◽  
Fatigue Crack Initiation ◽  
Internal Surface ◽  
Fatigue Tests ◽  
Inner Surface ◽  
Surface Notch ◽  
Medium Diameter

Cyclic internal oil pressure fatigue tests were carried out on medium-diameter ERW pipes of API 5LX - X60 in an attempt to determine the influence of surface defects on the fatigue strength. Experimental factors investigated were the depth and location of internal surface notch in relation to the axis of pipe. The specimen was subjected to cyclic internal pressure, the cyclic rate being 0.3–0.5 Hz. During the test, Acoustic Emission (AE) techniques were applied to detect the fatigue crack initiation. Along with the aforementioned fatigue tests, pulsating tension fatigue tests were carried out on specimens with the same surface notches as the cyclic internal pressure fatigue test specimen.

Polishing Processing to Internal Surface of Non-Magnetic Pipe by Magnetic Abrasive Finishing

2008 ◽  
Vol 53-54 ◽  
pp. 137-140
Author(s):  
Y. Chen ◽  
X. Wang ◽  
C.J. Zhang
Keyword(s):  
Magnetic Force ◽  
Solution Method ◽  
Internal Surface ◽  
Special Equipment ◽  
Magnetic Abrasive Finishing ◽  
Surface Polishing ◽  
Abrasive Finishing ◽  
Inner Surface ◽  
Magnetic Force Line ◽  
Usual Tool

It is very difficult matter that polishes the internal surface of the pipe, especially to the thin pipe with the traditional surface technology. Because a usual tool cannot into the inner surface of the thin pipe and automation do not achieved easily. This paper brings up a new method that utilize the characteristic of the magnetic force line may penetrate the non-magnetic material, may using the magnetic abrasive finishing (MAF) method complete to the inner surface of the thin pipe precise polishing. The magnetic abrasive finishing does not need special equipment to complete the complex shape internal surface polishing. Moreover, we already obtained the famous processing effect through the experiment. Meanwhile this paper analyses some factors of influences efficiency, and propose some solution method.

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