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Wyniki wyszukiwania dla: REDUCED PRESSURE

The effect of reduced pressure on carbon dioxide flow boiling heat transfer in minichannels
Publikacja. In the paper presented are the results of the study on the effect of reduced pressure on flow boiling heat transfer data in minichannels as well as conventional ones. That effect renders that most of heat transfer correlations fail to return appropriate results of predictions. Mostly they have been developed for the reduced pressures from the range 0.10.3. The special correction has been postulated to the inhouse model of flow...

An improved method for flow boiling heat transfer with account of the reduced pressure effect
PublikacjaIn the paper are presented the results using the authors own model to predict heat transfer coefficient during flow boiling. The model has been tested against a large selection of experimental data to investigate the sensitivity of the inhouse developed model. In the work are presented the results of calculations obtained using the semiempirical model on selected experimental flow boiling data of the refrigerants: R134a, R1234yf,...

A semiempirical model for flow boiling heat transfer with account of the reduced pressure effect
PublikacjaIn the present study the attention was focused on the influence of reduced pressure on the predictions of heat transfer during flow boiling at the extensive range of pressures. The results of calculations were to test the sensitivity of the inhouse flow boiling model with respect to the selection of the appropriate twophase flow multiplier, which is one of the distinctive elements of that model. For this purpose a few twophase...

Comparison of predictive methods for flow boiling heat transfer in conventional channels and minichannels  the effect of reduced pressure
PublikacjaIn the paper are presented the results of follow on studies from [1]–[3] using authors own model to predict heat transfer coefficient during flow boiling. The model has been tested against a large selection of experimental data collected from various researchers to investigate the sensitivity of the inhouse developed model. The collected experimental data came from various studies from literature and were conducted for the full...

COMPARISON OF PREDICTIVE METHODS FOR FLOW BOILING HEAT TRANSFER IN CONVENTIONAL CHANNELS AND MINICHANNELS – THE EFFECT OF REDUCED PRESSURE
PublikacjaIn the paper are presented the results of follow on studies from [1]–[3] using authors own model to predict heat transfer coefficient during flow boiling. The model has been tested against a large selection of experimental data collected from various researchers to investigate the sensitivity of the inhouse developed model. The collected experimental data came from various studies from literature and were conducted for the full...

Analysis of Organic Rankine Cycle efficiency and vapor generator heat transfer surface in function of the reduced pressure
PublikacjaIn the paper presented is analysis of the influence of reduced pressure on efficiency and heat transfer area of vapor generator of Organic Rankine Cycle (ORC) in case of subcritical and supercritical parameters of operation. Compared are two cases of subcritical and supercritical ORC featuring a similar arrangement of heat source supply and heat removal, that is featuring the same temperatures of working fluid before the turbine,...

Flow boiling of R1233zd(E) in a 3 mm vertical tube at moderate and high reduced pressures
PublikacjaThe results of flow boiling of R1233zd(E) in a 3 mm vertical stainless steel tube are presented at moderate and high saturation temperatures. Integral flow characteristics in the form of pressure drop and heat transfer coefficient are discussed for saturation temperatures ranging from 115 to 145 °C (corresponding reduced pressures from 0.2 to 0.7), mass velocity of 800 kg/m2s and heat flux of 20 kW/m2. All of the obtained heat...

Flow Maps and Flow Patterns of R1233zd(E) in a Circular Minichannel at Low, Medium and High Values of Saturation Pressure
PublikacjaThere is a gap in knowledge regarding the flow pattern of lowboiling working fluids in the range of high saturation temperatures (above 120°C) and medium and high reduced pressures (0.50.9). Data are present in the literature for similar values of reduced pressures, but for lower values of saturation temperature. This is due to the existing refrigeration applications of these working fluids. At high values of reduced pressure,...

Pressure drop and heat transfer during boiling and condensation at subcritical region
PublikacjaMost of the data presented in the literature relate to saturation temperatures in the range  20°C to 40°C due to the application in refrigeration technology. There is necessity to extend databases to higher values of saturation temperature due to new applications such as Organic Rankine Cycle and high temperature heat pumps. Only few papers contain data for high reduced pressure for low boiling point liquids. This paper focus...

Data points of structures of R1233zd(E) flowing in a circular minichannel at low, medium and high values of saturation pressure
Dane BadawczeDatabase present structures of twophase flow of R1233zd(E) in 3 mm vertical channel. Database contains datapoints which contain information of reduced pressure (ratio of saturation pressure and critical pressure), quality and mass velocity. 4 two phase structures are distinguished: bubbly flow, slug flow, intermittent flow and annular flow.

Experimental study of flow boiling pressure drop and heat transfer of R1233zd(E) at moderate and high saturation temperatures
PublikacjaThe paper presents the results of experimental study of flow boiling of R1233zd(E) in minichannel at moderate and high saturation temperatures. The heat transfer coefficient and pressure drop were measured for flow boiling in a stainless steel tube with 2 mm inside diameter and a length of 300 mm. Experiment has been conducted for saturation temperatures ranging from 83 to 145 °C which corresponds to values of reduced pressures...

Explanation of Reduction of Pressure Forces in Turbine Chamber Seals
PublikacjaThe paper describes a chamber seal reducing the aerodynamic forces created in shroud seals. Asymmetrical pressure distribution (due to rotorstator eccentricity) in the blade tip clearance leads to the creation of pressure forces acting on the blade shroud. By increasing the volume above the shroud, the pressure distribution becomes more uniform on the whole shroud circumference and the effect of rotor eccentricity is reduced....

Explanation of Reduction of Pressure Forces in Turbine Chamber Seals
PublikacjaThe paper describes a chamber seal reducing the aerodynamic forces created in shroud seals. Asymmetrical pressure distribution (due to rotorstator eccentricity) in the blade tip clearance leads to the creation of pressure forces acting on the blade shroud. By increasing the volume above the shroud, the pressure distribution becomes more uniform on the whole shroud circumference and the effect of rotor eccentricity is reduced....

Opposite pressure impact on electronphonon coupling in Eu2+ and Ce3+ doped AlN
Dane BadawczeThis data analyzes the influence of pressure on electron–lattice interactions in the 5d excited states of Ce3+ and Eu2+ in the AlN host based on pressuredependent photoluminescence and photoluminescence excitation spectra. Highpressure measurements on AlN samples doped with Eu2+ and Ce3+ ions reveal that the Stokes shift increases with pressure for...

The influence of moderate pressure and subzero temperature on the shelf life of minced cod, salmon, pork and beef meat
PublikacjaThe effect of moderate pressure at subzero temperature on natural microflora of minced cod, salmony, pork and beef meat was studied. Pressure of 193 MPa at –20 °C caused reduction of total bacterial count in pork and beef meat by 1.1 and 0.6 log cycles, respectively, and by about 1.5 log cycles in fish meat. Under these conditions the psychrophilic and psychrotophic bacteria were below the detection limit (<10CFU/g of sample) in...

Changes in enzymatic activity of fish and slaughter animals meat after high pressure treatment at subzero temperatures
PublikacjaThe aim of this study was to determine changes in the activity of proteolytic enzymes and transglutaminase of fish and mammal meat after pressurization at subzero temperatures. The activity was measured at the optimal pHs determined for enzymes from particular types of tested meat. It was found that increasing the pressure in the range of 60–193 MPa, did not change significantly the activity of acidic proteases of cod flesh, while...

Modeling of Surface Roughness in Honing Processes by UsingFuzzy Artificial Neural Networks
PublikacjaHoning processes are abrasive machining processes which are commonly employed to improve the surface of manufactured parts such as hydraulic or combustion engine cylinders. These processes can be employed to obtain a crosshatched pattern on the internal surfaces of cylinders. In this present study, fuzzy artificial neural networks are employed for modeling surface roughness parameters obtained in finishing honing operations. As...

Modelling study of flow boiling heat transfer of perspective fluids for refrigeration technology
PublikacjaThere is a gap of knowledge on flow boiling at high saturation temperatures and higher values of reduced pressure. Thus far, the inhouse developed semiempirical model for flow boiling and flow condensation showed a satisfactory accuracy for calculations for various refrigeration fluids for a wide scope of reduced pressures. This study presents results of calculations of heat transfer coefficient of perspective refrigeration fluids,...

Modelowanie procesu wrzenia i kondensacji w rozszerzonym zakresie ciśnień zredukowanych
PublikacjaNiniejsza rozprawa doktorska ma na celu pokazanie wpływu uwzględnienia ciśnienia zredukowanego w analizowanym modelu opisującym współczynnik przejmowania ciepła na zbieżność z danymi eksperymentalnymi.Przedmiotem analizy jest półempiryczny model Mikielewicza w zastosowaniu do danych eksperymentalnych w kanałach konwencjonalnych i o małej średnicy płynów uznanych za perspektywiczne.W ramach realizowanych prac badawczych pozyskano...

Evaluation of the influence of the opening pressure of a marine Diesel engine injector on the results of numerical simulation of the working cycle and their comparison with the results of the laboratory experiment
PublikacjaThe article presents the results of a numerical simulation of the working process carried out in a diesel engine. In the applied utility program DIESELRK, the laboratory engine Farymann Diesel type D10 was implemented. A selected inoperability of its functional fuel supply system  reduced opening pressure of the injector pinj  was introduced. The values of adequate diagnostic parameters were determined: working gas temperature...

Exergy analysis of a negative CO2 emission gas power plant based on water oxycombustion of syngas from sewage sludge gasification and CCS
PublikacjaA power cycle with waterinjected oxycombustion (water cycle) is investigated by exergy analysis. It is fueled with syngas (aka. producer gas) from gasification of sewage sludge. The cycle is equipped with a sprayejector condenser (SEC). CO2 is separated and compressed for transportation and storage. The net delivered electric power is 31% of the fuel exergy. The task efficiency is 39% when the flue gas bleed to gasification...

Effect of power frequency on the stress state of disc actuator
PublikacjaThis paper presents the concept of determining the optimum frequency of coil supply in inductivedynamic drive. As a criterion to obtain the sought frequency, the smallest value of reduced stress in the disc was assumed while maintaining the desired dynamics. The disc stress is determined on the basis of solution of vibrating thin plate equation. Magnetic pressure acting on the disc is obtained from a hybrid circumferentiallyfield...

The effect of high pressure and subzero temperature on total antioxidant capacity and the content of vitamin C, fatty acids and secondary products of lipid oxidation in human milk
PublikacjaThe objective of this study was to compare of the effects of high pressure of 193 MPa at  20°C and Low Temperature Long Time pasteurization (LTLT or holder pasteurization, 62,5°C; 30 min) on the content and composition of fatty acids (FAs), concentrations of secondary products of lipid oxidation (TBARS), the total antioxidant capacity (TAC), total vitamin C and ascorbic acid (AsA) content in human milk. It was shown that no significant...

Wyznaczenie obciążeń na poszycie okrętu wywołanych uderzeniem fal i uderzeniem w lód i ich wpływ na bezpieczeństwo okrętu
PublikacjaThe main problem is the vessels rather accurate determination of the hydrodynamic loads socalled hydroelasticity outside . This can be done by theoretical analysis , computer simulation or by experiment. This gives the hydrodynamic pressure distribution on the walls of the ship's hull and also on the walls of marine vessels .The most dangerous are the impact of extreme storm waves , the impact of the wharf and the impact zone...

XPS analysis of the GO based materials
Dane BadawczeGraphene oxides samples were measured by XPS method. The Xray photoemission spectroscopy measurements were carried out with Omicron NanoTechnology UHV equipment. The hemispherical spectrophotometer was equipped with a 128channel collector. The XPS measurements were performed at room temperature at a pressure below 1.1 × 10−8 mBar. The photoelectrons...

Hydrogen direct reduction and reoxidation behaviour of highgrade pellets
PublikacjaHigh grade pellets with basicity index close to 0.5 were directly reduced in pure hydrogen atmosphere. The reduction experiments were performed in the temperature range 800 e1000 C at the pressure of 8 bar. The pellets internal structure was analysed through micro tomography observations in the unreduced and reduced conditions. After reduction, the pellets showed a variation of porosity up to more than 15% with a remarkable change...

Analysis of start energy of Stirling engine type alpha
PublikacjaThe Stirling engine type alpha is composed of two cylinders (expansion space E and compression space C), regenerator that forms the space between the cylinders and the buffer space (under the pistons). Before the startup and as a result of longterm operation, the average pressure in the working space (above the pistons) and in the buffer space is the same. However, in the initial phase of operation, the average pressure in the...

Dissociation pathways of protonated water clusters
PublikacjaRelative abundances of positively ionized water clusters formed in a lowpressure electrical discharge as function of reduced electric field were obtained by using drift cell and quadrupole mass spectrometer. It was noticed that some clusters say with n=4 were more abundant than others, at comparable drift conditions. Dissociation energies have been derived from equilibrium conditions for relative clusters abundances. The HartreeFock...

Graphene oxide thin films deposited on a PCB board  chemical analysis
Dane BadawczeGraphene oxides based films were measured by Xray photoemission spectroscopy (XPS) method. TheXPS measurements were carried out with the Omicron NanoTechnology UHV equipment. The hemispherical spectrophotometer was equipped with a 128channel collector. The XPS measurements were performed at room temperature at a pressure below 1.1 × 10−8 mBar. The...

Evaluation of working spaces' technical condition of marine diesel engine on the basis of operation research
PublikacjaThe paper presents the method of evaluation of the technical state of working spaces of a marine diesel engine at the reduced control susceptibility. The method foresees making diagnosis on the basis of the measurements of exhaust gas pressure in the channels connecting engine cylinders with turbocharger's turbine. In the beginning of the article the research objects are characterized i.e. ZVIEZDA main engine of M401 type and the...

Dissociation energies of protonated water clusters
PublikacjaRelative abundances of positively ionized water clusters formed in a lowpressure electrical discharge as function of reduced electric field were obtained by using drift cell and quadrupole mass spectrometer. It was noticed that some clusters say with n = 4 were more abundant than others, at comparable drift conditions. Dissociation energies have been derived from equilibrium conditions for relative clusters abundances. The HartreeFock...

Calculation method for flow boiling and flow condensation of R134a and R1234yf in conventional and small diameter channels
PublikacjaThe paper presents the results of calculations performed using the authors’ model to predict the heat transfer coefficient during flow boiling for two refrigerants R134a and R1234yf. The experimental data from various past studies have been collected and the calculations have been conducted for the full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the inhouse...

EXPERIMENTAL VERIFICATION OF THE METHOD OF FLOW BOILING AND FLOW CONDENSATION HEAT TRANSFER PREDICTION FOR SELECTED FLUIDS
PublikacjaIn the paper presented are the results of calculations using authors own model to predict heat transfer coefficient during flow boiling of different refrigerants. The experimental data from various research studies from literature were collected. Calculations were conducted for a full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the in house developed model....

Timedomain description of pointsource acoustic wavefields as a useful approach in ultrasonic techniques
PublikacjaIn traditional acoustics, field problems are usually treated in the frequency domain, broadband fields being reduced to superposition of harmonic spectrum components. However, this approach is inherently acausal and it is known that in case of arbitrary signals, the distributionbased, timedomain description can be more effective. The present paper is an attempt to expand the timedomain linear systems formalism onto space problems...

TimeDomain Description of PointSource Acoustic Wavefields as a Useful Approach in Ultrasonic Techniques
PublikacjaIn traditional acoustics, field problems are usually treated in the frequency domain, broadband fields being reduced to superposition of harmonic spectrum components. However, this approach is inherently acausal and it is known that in case of arbitrary signals, the distributionbased, timedomain description can be more effective. The present paper is an attempt to expand the timedomain linear systems formalism onto space problems...

The importance of individual spray properties in performance improvement of a ureaSCR system employing flashboiling injection
PublikacjaThe appropriate mixing of a urea–water solution (UWS) with exhaust gases in a selective catalytic reduction system is crucial to efficiently reduce nitrogen oxides and diminish the deposition of liquid wall film. One of the methods to enhance the mixing of the UWS with the exhaust gases is a flashboiling injection. Its positive effect has been linked with a reduced Sauter mean diameter (SMD) and improved evaporation, but the...

Wavelet transform analysis reveals differences between patients with impaired LVEF and healthy individuals
PublikacjaHeart failure (HF) is a global pandemic. It af fects 64 million people worldwide, with stead ily increasing incidence, morbidity, mortality, and economic burden [1]. Forecasts indicate continued rising prevalence, especially among the elderly and in lowtomiddle sociode mographic index regions [2]. Left ventricular ejection fraction (LVEF) significantly impacts HF treatment and prognosis [3]. The sequence of physiological...

Problems of analytical determination of journal bearing bush fatigue strength estimates
PublikacjaProblems connected with determination of stress distribution in sliding layer of thinwalled bearing bushes, investigated in bearing fatigue test rigs, have been presented. Using an example of plain bearings tested in the fatigue machine SMOK (built at the Gdask University of Technology) problems with obtaining a convergence of iterative procedure for determining the fatigue strength estimators of bearing alloy surface layer are...

Comparison of state feedback and PID control of pressurizer water level in nuclear power plant
PublikacjaThe pressurizer water level control system in nuclear power plant with pressurized water reactor (PWR) is responsible for coolant mass balance. The main control goal is to stabilize the water level at a reference value and to suppress the effect of timevarying disturbances (e.g. coolant leakage in primary circuit pipeline system). In the process of PWR power plant operation incorrect water level may disturb pressure control or...

Prediction of flow boiling heat transfer coefficient for carbon dioxide in minichannels and conventional channels
PublikacjaIn the paper presented are the results of calculations using authors own model to predict heat transfer coefficient during flow boiling of carbon dioxide. The experimental data from various resea rches were collected. Calculations were conducted for a full range of quality variation and a wide range of mass velocity. The aim of the study was to test the sensitivity of the inhouse model. The results show the importance of taking into...

Combined numerical and experimental approach to determine numerical model of abdominal scaffold
PublikacjaA proper junction of the prosthesis and the abdominal wall is important in successful hernia repair. The number of tacks should be balanced to assure appropriate mesh fixation and not to induce postoperative pain. Numerical simulations help to find this balance. The study is aimed at creating a proper numerical model of a knitted surgical mesh subjected to boundary conditions and load occurring in the abdominal cavity. Continuous,...

Optimizing CO2 Purification in a Negative CO2 Emission Power Plant
PublikacjaIn the pursuit of mitigating CO2 emissions, this study investigates the optimisation of CO2 purification within a Negative CO2 Emission Power Plant using a spray ejector condenser (SEC) coupled with a separator. The approach involves directcontact condensation of vapour, primarily composed of an inert gas (CO2), facilitated by a subcooled liquid spray. A comprehensive analysis is presented, employing a numerical model to simulate...

Extremal thermal loading of a bifurcation pipe
PublikacjaThe subject of considerations is a spherical bifurcation pipe of a live steam made of steel P91, which is an element of a block of coalfired power plant working with a 18K370 turbine. As experience shows, it is a very sensitive element of the boiler pipelines. An extreme work scenario for such a block has been adopted, in which the turbine is shutting down to a warm state three times in 24 hours. This is an action dictated by...

Application of Feed Forward Neural Networks for Modeling of Heat Transfer Coefficient During Flow Condensation for Low and High Values of Saturation Temperatur
PublikacjaMost of the literature models for condensation heat transfer prediction are based on specific experimental parameters and are not general in nature for applications to fluids and nonexperimental thermodynamic conditions. Nearly all correlations are created to predict data in normal HVAC conditions below 40°C. High temperature heat pumps operate at much higher parameters. This paper aims to create a general model for the calculation...

Numerical analysis of vacuum drying of a porous body in the integrated domain
Publikacjan the present study, the vacuum drying process of an apple slice is numerically modeled based on a control volume method. Transient twodimensional Navier– Stokes, energy, moisture, and Luikov equations are solved by numerical coding (Fortran) to simulate the simultaneous heat and mass transfer in the ambient and apple slice, respectively. The privilege of using Luikov's model is that the capillary forces are considered, and a...

A novel approach for processing CaAlSiON glassceramics by spark plasma sintering: Mechanical and electrical properties
PublikacjaLithium containing glassy materials can be used as solid electrolytes or electrode materials for lithiumion batteries due to their high energy density. Conventional meltquenched Ca11Al14Si16O49N10 glass powder containing 24 e/o N, doped with Liions (1, 3, and 6 wt. %) and sintered by spark plasma sintering technique (SPS) was studied. The benefits of using SPS to produce glassceramics are rapid heating rates compared to conventional...

Numerical Study on Mitigation of Flow Maldistribution in Parallel Microchannel Heat Sink: Channels Variable Width Versus Variable Height Approach
PublikacjaMicrochannel heat sink on one hand enjoys benefits of intensified several folds heat transfer performance but on the other hand has to suffer aggravated form of trifling limitations associated with imperfect hydrodynamics and heat transfer behavior. Flow maldistribution is one of such limitation that exaggerates temperature nonuniformity across parallel microchannels leading to increase in maximum base temperature. Recently, variable...

Thermal Biomass Conversion: A Review
PublikacjaIn this paper, the most important methods of thermal conversion of biomass, such as: hydrothermal carbonization (180–250 °C), torrefaction (200–300 °C), slow pyrolysis (carbonization) (300–450 °C), fast pyrolysis (500–800 °C), gasification (800–1000 °C), supercritical steam gasification, high temperature steam gasification (>1000 °C) and combustion, were gathered, compared and ranked according to increasing temperature. A comprehensive...

Analysis of the properties of the YSTF ceramics materials before and after reduction
Dane BadawczeThe valence of titanium in reduced YSTF ceramics materials was investigated. Ceramics were reduced by annealing in a hydrogen atmosphere. For comparison unreduced sample was also measured. Valance state was measured by XPS method.

Enhancing seismic performance of bucklingrestrained brace frames equipped with innovative bracing systems
PublikacjaNowadays, to improve the performance of conventional bracing systems, in which, buckling in the pressure loads is the main disadvantage, the bucklingrestrained brace (BRB) is introduced as a solution. In this study, the performance of the BRB system was improved with innovative lateralresisting systems of doublestage yield bucklingrestrained brace (DYB), and a combination of DYB improved with shape memory alloy (SMA) materials...