Ensuring the stability is a key issue to be solved for the technical application of nanocomposite... more Ensuring the stability is a key issue to be solved for the technical application of nanocomposites. In this work, fatty acid P1801 served as base phase change material (PCM)P1801, and its main ingredients are palmitic acid (58%) and stearic acid (38%). Titania (TiO2) and alumina (Al2O3) with mass concentrations of 1% and 5% were selected as nanoparticles, while polyvinylpyrrolidone (PVP) or oleic acid (OA) with mass concentrations of 5% were tested as surfactants. On the basis of the measured temperature distributions in the sample, which is subject to melting and solidification processes, it was determined which of the tested nanocomposites are stable and which are not. In addition, a thermal test was proposed to assess the stability of the produced nanoPCM, which consists in measuring the temperature distribution versus time according to a precisely given procedure.
A comprehensive review of published works dealing with numerical modelling of forced convection h... more A comprehensive review of published works dealing with numerical modelling of forced convection heat transfer and hydrodynamics of nanofluids is presented. Due to the extensive literature, the review is limited to straight, smooth, circular tubes, as this is the basic geometry in shell-and-tube exchangers. Works on numerical modelling of forced convection in tubes are presented chronologically in the first part of the article. Particular attention was paid to the method of the solution of governing equations, geometry of the heating section, and boundary conditions assumed. Influence of nanoparticles on heat transfer and flow resistance are discussed. Basic information is summarized in tabular form, separately for single-phase approach and two-phase models. The second part of the article contains the correlation equations proposed in the presented papers for the calculation of the Nusselt (Nu) number or heat transfer coefficient, separately for laminar and turbulent flow. Details of...
Pipe-in-pipe heat exchangers are commonly used in mechanical and chemical engineering. The value ... more Pipe-in-pipe heat exchangers are commonly used in mechanical and chemical engineering. The value of the heat transfer coefficient inside an annular gap is necessary to determine the needed heat transfer area of such a heat exchanger. While new refrigerants are used in refrigerating technology, applicable correlations for the heat transfer inside annular gaps and for these fluids are needed. The aim of this work was to determine own correlations for the heat transfer coefficient during one-phase flow of such refrigerants inside annular gaps. In this part of the paper, existing correlations are verified, the test stand is described and the experimental procedure is presented.
International Journal of Heat and Mass Transfer, 2005
ABSTRACT In the paper, nonlinear features of the air bubbling from a submerged glass nozzles are ... more ABSTRACT In the paper, nonlinear features of the air bubbling from a submerged glass nozzles are discussed. The air bubbles were emitted from glass nozzles of different diameters submerged in distilled water at a depth of 15 cm in a cylindrical tank of 30 cm in diameter and 37 cm height. The air volume flow rate was changed from 1 l/h to 45 l/h. A laser-photodiode and an acoustic technique system have been used. Also photographic study of bubbles departure has been carried out. Measured data have been analysed using the fractal analysis method. It has been shown that bubbles dynamics is of deterministic chaos nature and behaviours of such system can be chaotic or periodic depending on the volume flow rate. The map of chaos appearance has been constructed. Data recorded by acoustic system has been used to analysis of bubble wall movement.
The aim of the work is to identify the influence of porous coating on average heat transfer coeff... more The aim of the work is to identify the influence of porous coating on average heat transfer coefficient and pressure drop during flow boiling of selected refrigerants and their mixtures with oil. The aim is to determine own correlation for heat transfer coefficient during flow boiling of pure refrigerants inside porous coated tubes. In the first part published results of investigations of flow boiling inside porous coated tubes are discussed. Augmentation of heat transfer coefficient and pressure drop as well as the influence of porous on critical heat flux density is described.
Ensuring the stability is a key issue to be solved for the technical application of nanocomposite... more Ensuring the stability is a key issue to be solved for the technical application of nanocomposites. In this work, fatty acid P1801 served as base phase change material (PCM)P1801, and its main ingredients are palmitic acid (58%) and stearic acid (38%). Titania (TiO2) and alumina (Al2O3) with mass concentrations of 1% and 5% were selected as nanoparticles, while polyvinylpyrrolidone (PVP) or oleic acid (OA) with mass concentrations of 5% were tested as surfactants. On the basis of the measured temperature distributions in the sample, which is subject to melting and solidification processes, it was determined which of the tested nanocomposites are stable and which are not. In addition, a thermal test was proposed to assess the stability of the produced nanoPCM, which consists in measuring the temperature distribution versus time according to a precisely given procedure.
A comprehensive review of published works dealing with numerical modelling of forced convection h... more A comprehensive review of published works dealing with numerical modelling of forced convection heat transfer and hydrodynamics of nanofluids is presented. Due to the extensive literature, the review is limited to straight, smooth, circular tubes, as this is the basic geometry in shell-and-tube exchangers. Works on numerical modelling of forced convection in tubes are presented chronologically in the first part of the article. Particular attention was paid to the method of the solution of governing equations, geometry of the heating section, and boundary conditions assumed. Influence of nanoparticles on heat transfer and flow resistance are discussed. Basic information is summarized in tabular form, separately for single-phase approach and two-phase models. The second part of the article contains the correlation equations proposed in the presented papers for the calculation of the Nusselt (Nu) number or heat transfer coefficient, separately for laminar and turbulent flow. Details of...
Pipe-in-pipe heat exchangers are commonly used in mechanical and chemical engineering. The value ... more Pipe-in-pipe heat exchangers are commonly used in mechanical and chemical engineering. The value of the heat transfer coefficient inside an annular gap is necessary to determine the needed heat transfer area of such a heat exchanger. While new refrigerants are used in refrigerating technology, applicable correlations for the heat transfer inside annular gaps and for these fluids are needed. The aim of this work was to determine own correlations for the heat transfer coefficient during one-phase flow of such refrigerants inside annular gaps. In this part of the paper, existing correlations are verified, the test stand is described and the experimental procedure is presented.
International Journal of Heat and Mass Transfer, 2005
ABSTRACT In the paper, nonlinear features of the air bubbling from a submerged glass nozzles are ... more ABSTRACT In the paper, nonlinear features of the air bubbling from a submerged glass nozzles are discussed. The air bubbles were emitted from glass nozzles of different diameters submerged in distilled water at a depth of 15 cm in a cylindrical tank of 30 cm in diameter and 37 cm height. The air volume flow rate was changed from 1 l/h to 45 l/h. A laser-photodiode and an acoustic technique system have been used. Also photographic study of bubbles departure has been carried out. Measured data have been analysed using the fractal analysis method. It has been shown that bubbles dynamics is of deterministic chaos nature and behaviours of such system can be chaotic or periodic depending on the volume flow rate. The map of chaos appearance has been constructed. Data recorded by acoustic system has been used to analysis of bubble wall movement.
The aim of the work is to identify the influence of porous coating on average heat transfer coeff... more The aim of the work is to identify the influence of porous coating on average heat transfer coefficient and pressure drop during flow boiling of selected refrigerants and their mixtures with oil. The aim is to determine own correlation for heat transfer coefficient during flow boiling of pure refrigerants inside porous coated tubes. In the first part published results of investigations of flow boiling inside porous coated tubes are discussed. Augmentation of heat transfer coefficient and pressure drop as well as the influence of porous on critical heat flux density is described.
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Papers by Janusz Cieśliński