Wyniki wyszukiwania - Biblioteka Nauki

1

Condensation in flow through horizontal tubes

100%

Madejski J.

Archives of Thermodynamics

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2000

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tom Vol. 21, nr 3-4

99-116

EN

Heat transfer and pressure drop in horizontal tubes in which condensation takes place is studied on this paper. The theory of condensate flow in the 3-D film under the influence of gravity and axial shear stress is given. Such condensers are widely used in refrigeration units. A numerical example shows that they can be used also in steam power plants.

2

Condensing flow of wet steam inside horizontal tubes

100%

Madejski J.

Archives of Thermodynamics

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2001

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tom Vol. 22, nr 1-2

5-10

EN

This paper is a continuation of the author's devoted to the condensing flow of dry saturated steam. It is argued that flow of droplets can be treated separately because the deposition on liquid film can be neglected.

3

Synthesis, Characterization and Crystal Structure Studies of 1-(4-Chloro-benzenesulfonyl)-piperidin-4-yl-diphenyl-methanol

80%

Benakaprasad S. , Naveen S. , Anandakumar C. , Sunilkumar Y. , Sridhar M. , Shashidhara Prasad J. , Rangappa K.

Polish Journal of Chemistry

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2007

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tom Vol. 81, nr 5-6

1191-1199

EN

1-(4-Chloro-benzenesulfonyl)-piperidin-4-yl-diphenyl-methanol was synthesized by the condensation of [piperidin-4-yl]-diphenyl-methanol with p-chlorobenzene sulfonylchloride in methylene dichloride as solvent and triethylamine as the base. The compound obtained was characterized by spectroscopic techniques and confirmed by X-ray crystallographic studies. The crystallographic data analysis reveals that the title compound crystallizes in the monoclinic space group P21/c with cell parameters a = 10.214(9capital A, ring, b = 11.371(5)cvapital A, ring, c = 20.939(16)capital A, ring, beta = 115.399(2), V = 2197(3) capital A, ring3 for Z = 4. The structure has been solved by direct methods and refined toR1 = 0.0560 for 3658 observed reflections with I > 2sigma(I). The piperidine ring is in a chair conformation. The geometry around the S atom is distorted from regular tetrahedron.

4

Condensation wave identification in moist air transonic flows through nozzles

80%

Dykas S. , Smołka K. , Majkut M. , Strozik M.

Transactions of the Institute of Fluid-Flow Machinery

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2016

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tom nr 131

67--77

EN

This paper identifies the location of water vapour spontaneous condensation during air expansion in convergent-divergent nozzles. The comprehensive analysis proposed herein includes an analytical solution together with experimental and numerical investigations. Numerical calculations are performed using an in-house computational fluid dynamics code based on the solution of Reynolds averaged Navier-Stokes equations supplemented with additional partial differential equations modelling the condensation process of water vapour contained in atmospheric air. Experiments were carried out using an in-house facility adapted for measurements of atmospheric air transonic flows.

5

Modeling of drying and pyrolysis in a gasifier during the startup phase

80%

Ciżmiński P. , Polesek-Karczewska S. , Kardaś D.

Transactions of the Institute of Fluid-Flow Machinery

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2015

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tom nr 128

73--83

EN

An appropriate arrangement of particular zones in the gasifier is of practical importance for the gasification process effectiveness. One of the parameters that affects the optimum reactor operation and has to be taken into account is the speed of bed movement. The transient one-dimensional model describing the heat and mass transfer in the upper section of the biomass fixed bed gasifier that covers the zones of evaporation and pyrolysis, was introduced. To study the effect of packed bed settling resulted from the wood particles’ volume change due to their devolatilization, the simulations for various bed movement speeds were performed. The computation results indicated, as expected, on the different distribution of pyrolysis and drying zones, depending on the speed value. The clear tendency towards the reduction of pyrolysis zone, and on the other hand, towards the expansion of drying zone, with an increasing movement speed was observed.

6

O wybranych mechanizmach kondesacji treści w przekazach medialnych

80%

Grzelka M.

Poznańskie Studia Polonistyczne. Seria Językoznawcza

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2013

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tom 20

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nr 1

9-18

PL

This article revolves around research into the language of the media with special emphasis placed on a description of the fundamental mechanisms of condensing content in printed and audio and visual media. Condensation is among the basic tools of content accumulation; it is related to simplifying the message, generalization and stylistic deformations. Mechanisms applied to summarize have been identified within various areas, including construing messages and releasing to media as well as modes of organizing the content. Of importance here is the trend of replacing verbal messages with visual messages (tables, photos, information graphics, charts, coverage). While condensation is reflected in media as a communication-related activity strictly functionalized within a message, in its structure (cf. the summarizing role of titles, leads, visualizations), it is also conditioned by genre-related issues (cf. news, previews etc.) and most times results from the broadcaster’s strategic efforts.

7

Numerical estimation of losses in steam flow through LP turbine blade rows

80%

Dyskas S. , Wróblewski W.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2006

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tom Vol. 10, No 2

177-190

EN

The aim of this work is to estimate the losses in steam flow through an LP steam turbine rotor and the who]e stage. Two types of losses occur in steam flow, aerodynamic (profile, secondary flow, leakage) and thermodynamic (due to addition of heat caused by condensation). The presented numerical results are split into two groups. First, a comparison of three different calculation methods of steam flow is carried out. To this end, the geometry of an LP steam turbine's last rotor is chosen. The first examined method is the Streamline Curvature Method (SCM) used on the meridional plane with loss correlations, the other two being commercial and in-house CFD codes, solving the Reynolds-averaged Navier-Stokes equations for a 3D flow. The first two codes model equilibrium steam properties below the saturation line, while the latter models non-equilibrium steam properties. Finally, a comparison is made of the influence on lass prediction of various condensation models for the geometry of the penultimate stage, with the use of an in-house CFD code.

8

Numerical calculation of the expansion flow with spontaneous condensation in water vapour and moist air

80%

Chmielniak T. , Wróblewski W. , Dykas S.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika

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1999

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tom Z. 67

185--194

EN

A method for solving an expansion flow of the water steam and moist air is presented in the paper. The phenomenon of the homogenous condensation is also calculated. The gas is governed by the Euler equation, which are coupled with the system of partial differential equation describing the liquid phase. There is no slip between gas and water droplets. In this paper the real water vapour properties and functions in all regions were considered. It makes possible to model the condensation process more accurate. All governing equations are discretised by the cell-centered finite volume formulation. The numerical procedure is based on an explicit Godunov-type scheme. The method has been extensively tested including a one dimension test called the shock tube test, the expansion flow through a Laval nozzle and flow through the blade cascade of a turbine stator.

9

The influence of electric field on HFC-245fa condensation Br

80%

Bryszewska-Mazurek A. , Mazurek W.

Materials Science Poland

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2009

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tom Vol. 27, No. 4/2

1257--1261

EN

Condensation of HFC-245fa on a vertical cylindrical surface of a heat pipe has been studied experimentally. The temperature of the heat pipe evaporator decreased under the electric field (ac and dc). Heat transfer enhancement was observed when the electrode placed in a condenser section of the pipe was under a high voltage. The heat pipe thermal conductivity increased about 6-8% dependently of a magnitude and kind of high voltage. The best results were obtained for the straight polarity of the electrode.

10

Thermal and visualisation study of the hfe7100 refrigerant condensation process

80%

Bohdal T. , Sikora M. , Formela K.

Acta Mechanica et Automatica

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2024

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tom Vol. 18, no. 1

60--67

EN

Technological advances are contributing to the search for highly efficient energy designs, and increasing interest in compact heat exchangers. Indeed, small channel diameters determine large heat transfer coefficients and condition a significant heat transfer area about the overall volume of the heat exchanger, as well as a smaller amount of refrigerant flowing in the system. Nevertheless, the operat-ing stability and energy efficiency of compact heat exchangers are influenced by two-phase flow structures, which depend on thermal flow parameters. Knowledge of the structures formed during the condensation process is therefore essential for optimising the operation of re-frigeration and air-conditioning equipment. This article presents the results from experimental studies of the HFE7100 refrigerant, from the hydrofluorocarbon group, condensation process in mini-channels with hydraulic diameters dh = 2.0 mm, 1.2 mm, 0.8 mm and 0.5 mm. Thermal flow characteristics were determined, and the forming structures of two-phase flow were recorded. The results of visualisation were subjected to morphological image analysis, based on a special algorithm written in MATLAB software. The algorithm makes it possi-ble to determine the void fraction, which is necessary for calculating the vapour quality, as well as the area of vapour bubbles and their number, directionality and length along the x- and y-axes.

11

Numerical calculation of the steam condensing flow

80%

Dykas S.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2001

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tom Vol. 5, No 4

519-535

EN

Considering the flow in the last stages of LP (low pressure) steam turbine the strong non-linearity of the thermal parameters of state and possibility of the two-phase flow have to be taken into account in the numerical calculation of the flow field. In this paper numerical calculations of the steam condensing flow for the turbine geometry are presented. The steam properties are described here on the basis of the IAPWS’97 formulation. The classical nucleation theory of Volmer and Frenkel was adapted for modelling of condensing flow. The droplet growth model of Gyarmathy is implemented. The calculations are based on the time dependent 3D Euler equations, which are coupled to three additional mass conservation equations for the liquid phase and are solved in conservative form.

12

Influence of condensation on temperature measurements in the case of a dew point probe

80%

Mikielewicz D. , Ihnatowicz E. , Mikielewicz J.

Archives of Thermodynamics

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1998

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tom Vol. 19, no 1/2

87-101

EN

In the work presented are the considerations of the influence of condensation on the measurements of temperature using a dew point probe. The analysis is based on the solution of the differential equations describing the probe dynamics. Investigations of the influence of condensation in the proposed model is are relatively simple as the term responsible for condensation appears as a free term. Obtained results of simulations confirm experimentally observed trends of oscillations induced by droplet separation from the probe membrane. Proposed has also been a direction for investigations where the condensation structure could be investigated as an inverse problem to the one discussed here.

13

Condensation and cavitation in water and water mixtures

80%

Marsik F. , Delale C. , Sedlar M.

Archives of Thermodynamics

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2003

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tom Vol. 24, no 1

3-16

EN

The aim of this investigation is to reconsider the classical theory of homogeneous condensation and bubble nucleation by using real properties of fluids and non-equilibrium (dissipative) effects. To find out the influence of a chemical composition on the surface tension and consequently on the nucleation work and further to elucidate how the nucleation barrier is affected by the irreversible processes on the bubble surface the theoretical analysis is used. Both these effects are important for the nucleation and it is shown that they can increase (for condensation) the nucleation work. The theory is suitable both for pure substances and for their mixtures. The emphasis is laid on water condensation, boiling and cavitation.

14

The influence of electric field on hfc-245fa condensation.

80%

Bryszewska-Mazurek A. , Mazurek W.

Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje

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2007

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tom Vol. 46, nr 19

262-264

EN

The condensation of HFC-245fa on a vertical cylindrical surface of the heat pipe has been studied experimentally. The temperature of the heat pipe evaporator decreased under the electric field (AC and DC). The heat transfer enhancement was observed when the electrode placed in a condenser section of the pipe was under the high voltage. The heat pipe ability to transfer heat (heat pipe thermal conductivity) increased about 6-8 prec. dependently of a magnitude and kind of high voltage. The best results were observed for the straight polarity of the electrode.

15

Ferrocene-derived Aminomethanephosphosphonous Acids. Synthesis of Their Esters and Amides with Polyethylene Glycols and Polyamines

80%

Lewkowski J. , Skowroński R.

Polish Journal of Chemistry

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2005

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tom Vol. 79 / nr 3

525-528

EN

The synthesis of (ferrocenyl)-N-diphenylmethylaminomethane phosphonous acid ester with polyethylene glycols and the synthesis of its amides with polyamines in dichloromethane and in the presence of N,N_-dicyclohexylcarbodiimide (DCC) as condensing agent are presented.

16

Modeling the phenomena accompanying the condensation of environmentally friendly refrigerants in mini-channels

80%

Kuczyński W.

Archives of Thermodynamics

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2023

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tom Vol. 44, no 1

121--137

EN

This paper presents the results of an experimental study and mathematical modeling of the effect of dynamic instabilities on the condensation phase transformation of the refrigerants homogeneous R134a and its replacement in the form of isomers R1234yf and R1234ze and R404A or R507 and R448A in pipe mini-channels. In the case of homogeneous chlorofluorocarbons (CFCs), it is the 1234 isomers that are envisioned as substitutes for the withdrawn ones with high ozone depletion potential and global warming potential. For zeotropic and azeotropic mixtures, for example, these are R507 or R448A. The paper presents a dimensional analysis procedure based on the Buckingham Π theorem to develop a regression velocity model of pressure dynamic instabilities. The experimental part of the work was carried out with the use of tubular mini-channels with internal diameter 1.40–3.3 mm.

17

Influence of fouling and inert gases on the performance of regenerative feedwater heaters

80%

Butrymowicz D. , Trela M.

Archives of Thermodynamics

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2002

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tom Vol. 23, no 1-2

127-140

EN

The paper is devoted to the performance estimation of a recuperative heat exchanger under conditions of fouling and presence of inert gases. Calculations were performed using three different approaches based on: the global, lumped-parameter and 1D models. With the use of 1D model the influence of fouling and air-concentration on the distribution of both the pertinent heater temperatures and heat flux were investigated. It appeared that air plays a dominant role in the case when its concentration is sufficiently high. It may be concluded that the proposed 1D model provides a very efficient method for heat transfer evaluation of heat exchangers.

18

Effect of organic mist on the process of cryogenic condensation

80%

Walczyk H.

Chemical and Process Engineering

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2008

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tom Vol. 29, z. 3

607-622

EN

Results of numerical calculation for low temperature condensation process of volatile organic compounds from a mixture with inert gas and in the presence of organic mist in gaseous phase are presented. Calculations were done based on the developed one-dimensional mathematical model. Numerical results were obtained for various values of dp and Kp given as parameters characterizing mist existing in a gaseous mixture introduced to the condenser.

PL

Przedstawiono wyniki obliczeń numerycznych procesu niskotemperaturowej kondensacji lotnych związków organicznych z mieszaniny z gazem inertnym w obecności mgły w fazie gazowej. Zastosowano jednowymiarowy model matematyczny procesu. Obliczenia wykonano dla różnych wartości parametrów dp i Kp, charakteryzujących mgłę w gazowej mieszaninie wprowadzanej do kondensatora.

19

Experimental study of low-temperature condensation coupled with adsorption

80%

Rotkegel A.

Chemical and Process Engineering

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2008

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tom Vol. 29, z. 3

639-650

EN

An experimental study of volatile organic compound (VOC) removal from gas in a system of low-temperature condensation coupled with adsorption was performed. The gas mixture used in experiments was composed of nitrogen as a inert gas and evaporated 2-propanol as a VOC. It was proved that the proposed method of gas cleaning was extremely effective in the VOC removal from gases, especially with relatively high concentration (10 g.N.m.3) of VOC in inlet gases. In this case, the method is more economic than low temperature condensation or adsorption alone.

PL

Badano doświadczalnie proces oczyszczania gazu z lotnego związku organicznego (ang. volatile organic compound, VOC) w zintegrowanym układzie kondensacji niskotemperaturowej i adsorpcji. Gazem oczyszczanym był azot, a VOC stanowił 2-propanol. Wykazano, że zaproponowana metoda oczyszczania gazu jest bardzo skuteczna w usuwaniu VOC z gazu oraz że w przypadku dużych stężeń VOC w gazie oczyszczanym (10 g.N.m.3) jest ona znacznie bardziej ekonomiczna od kondensacji niskotemperaturowej lub adsorpcji stosowanej z osobna.

20

Nierównowagowe przemiany fazowe

80%

Kornet S. , Badur J.

Logistyka

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2013

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tom nr 4

PL

Woda jest substancją, która występuje najczęściej w naturze i może przyjmować różne stany skupienia. Przemiany fazowe zachodzące w wodzie są przedmiotem naszego codziennego doświadczania. Mogą one zachodzić spontanicznie, lub także mogą być one inicjowane przez człowieka w różnego rodzaju maszynach i urządzeniach. Do najbardziej ciekawych przemian, które zachodzą w tym płynie są kondensacja i flashing. Oba te zjawiska mogą być zainicjowane poprzez szybką zmianę ciśnienia, zatem są to przemiany indukowane „naprężeniowo”. Zjawiskiem branym pod uwagę w realizowanych badaniach jest kondensacja pary wodnej. W części NP kondensacyjnej turbiny parowej przedostatni i ostatni stopień pracują w obszarze, w którym zachodzi zjawisko tzw. spontanicznej kondensacji, która jest nierównowagowym przejściem fazowym. W pracy przedstawiono wyniki obliczeń przepływu pary w części NP turbiny parowej mocy 200MW i porównano je z danymi eksperymentalnymi. Obliczenia przeprowadzono z wykorzystaniem różnych sposobów modelowania przepływu pary.

EN

Water is a substance, which occurs most commonly in nature and can exist in different states of aggregation. Phase transformations, taking place in the water, are a subject of our everyday experience. They happen spontaneously or are initiated by a man in a various kinds of machines and devices. The most interesting phenomenons, occurring in this fluid, are condensation and flashing. Both of these phenomenons can be initiated through a rapid pressure change, therefore there are a stress induced phase transitions brought about the mechanism of local tension of the fluid. Condensation was the main object of the research. In the experimental part of the work only condensation has been taken into account. Actually, in the CFD literature, there are three main types of non-equilibrium condensation models. These three main types of models are: the single continuum approach (called also single-fluid approach), the Eulerian –Eulerian multi-phase approach (called also two-fluid approach) and Lagrangean-Eulerian Fluid Solid Interaction approach. In this part, there have been taken the attempts of different condensation models comparison. Numerical calculation, done using the CFD code, are confronted with a classical experiment IMP PAN made in the de Laval nozzle.