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Theoretical and Experimental Analysis of Drying Various Geometrical Forms of Red Pepper

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Onat A., Binark A.

Acta Physica Polonica A

2015

vol. 127

issue 4

1388-1392

In this study, a counter flow convection-type dryer was designed and manufactured. During experiments, four different geometrical forms of pepper specimens were dried in a complete (unsliced), perforated, crosscut, and longitudinally sliced forms. For each type of red pepper specimens, the experiments have been conducted at air velocity level of 0.5 m/s, relative humidity of 10-15%, and temperature of 55-60°C. The theoretical mathematical model of drying process was developed, considering the pepper's bottom surface to be isolated. The drying curves of experimental results are compared to ones obtained from the theoretical analyses. The comparison showed that experimental results are consistent with the theoretical model. The best results, considering the drying duration, are collected from the specimens sliced longitudinally, which were followed by the crosscut specimens, perforated and unsliced-complete specimens, respectively. 82% water (humidity) content in 500 g sample was reduced to 4% in longitudinally cut samples, 6% in crosscut samples, 7.5% in perforated samples and 8% in unsliced-complete samples, after 14 hours of drying. It is suggested that regarding to easiness of processing, the crosscut red peppers are more suitable, compared to the other geometrical forms.

Analysis of Thermal Field in Mineral Transformer Oil Based Magnetic Fluids

100%

Kosterec M., Kurimský J., Cimbala R., Čonka Z., Kruželák L., Rajňák M., Timko M., Kopčanský P., Vargová B.

Acta Physica Polonica A

2017

vol. 131

issue 4

937-939

Growing interest in the use of magnetic fluids in power systems especially in transformers as insulation and a coolant is nowadays registered. Magnetisable nanofluids, which are used in cooling systems as an alternative to mineral transformer oil, are characterized by lower concentration of magnetic nanoparticles. The magnetic fluid has better heat transfer and dielectric properties such as breakdown than mineral transformer oil and it can be used to improve heat flow, thereby increasing the ability of the active parts to resist failures such as electromagnetic pulses. External magnetic field may be used for forced circulation of magnetic fluid. Magnetic force inside the magnetic fluid can be adequately controlled by adjusting the incident magnetic field. This paper presents thermal distribution, fluid flow and cooling ability of mineral transformer oil and magnetic fluid based on mineral transformer oil. The concentration of Fe₃O₄ magnetic nanoparticles is 0.15% volume of mineral transformer oil. The thermal field is generated by a steel conductor. Thermal distributions in mineral transformer oil and magnetic fluid are investigated and differences for both cases are discussed in the paper.

Experimental Modelling of Czochralski Melt Flow with a Slow Crystal Dummy Rotation

100%

Haslavsky V., Gelfgat A., Kit E.

Acta Physica Polonica A

2013

vol. 124

issue 2

193-197

This study examines the effect of slow crystal dummy rotation on three-dimensional oscillatory instability and time-dependent supercritical flow states in a Czochralski melt flow experimental model. To enable further comparison with numerical modelling, the experiments are carried out using a 20 cSt silicone oil as an experimental liquid and in a large diameter crucible, which allows one to work in a narrow temperature interval, so that temperature dependence of all the thermophysical properties of the experimental liquid can be neglected. The measurements confirm, partially qualitatively and partially quantitatively, earlier numerical predictions on destabilization ofthe Czochralski convective flow by a slow rotation. A simple power dependence of flow oscillations frequency on the Grashof and rotational Reynolds numbers that fits all the experimental runs was found.

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3 Acta Physica Polonica A

1 2017

1 2015

1 2013

1 Binark A.

1 Cimbala R.

1 Gelfgat A.

1 Haslavsky V.

1 Kit E.

1 Kopčanský P.

1 Kosterec M.

1 Kruželák L.

1 Kurimský J.

1 Onat A.

1 Rajňák M.

1 Timko M.

1 Vargová B.

1 Čonka Z.

Search results

Theoretical and Experimental Analysis of Drying Various Geometrical Forms of Red Pepper

Analysis of Thermal Field in Mineral Transformer Oil Based Magnetic Fluids

Experimental Modelling of Czochralski Melt Flow with a Slow Crystal Dummy Rotation