Wyniki wyszukiwania - Biblioteka Nauki

1

The analysis of the solar power plant performance in temperate climate

100%

Zdyb A. , Dragan P. , Jaremek A.

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tom z. 65, nr 1

73--79

EN

Due to gradual depletion of fossil fuels resources and emission of harmful chemicals accompanying the combustion process, the interest in alternative energy sources still increases. Among many kinds of alternative sources, solar radiation is very special because of its wide availability and large technical potential. Photovoltaic systems providing the electric energy are used in many countries. The most important part of photovoltaic system is a module, which parameters (e.g. efficiency, rated power, temperature coefficients of power and efficiency, short circuit current, open circuit voltage) are determined in laboratory tests under Standard Test Conditions (STC: 25°C, 1,000 W/m2 , air mass 1.5). However, in real outdoor conditions the modules exhibit lower efficiency since local climate influences their performance and different external factors generate energy losses in the whole system. The aim of this work is the performance analysis of a solar power plant connected to the grid, which total rated power is 2.985 MW and it works in temperate climate in eastern Poland. Insolation in the location was estimated according to Solargis data and the role of the modules tilt angle, of which the value is non-typical for the considered location was studied. The tilt angle smaller than optimal angle allows increasing the amount of the solar radiation collected in the summer period. The electric energy production based on the inverters data in 2016 and 2017 as well as yearly yield are presented. The results are compared to data coming from other solar power plants, also located at high latitude.

2

Single – axis sun tracking unit with sensor control

100%

Bugała A. , Frydrychowicz-Jastrzębska G.

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2015

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tom Vol. 13

414--422

EN

The results of experimental verification of considerations conducted in [3] are presented, in terms of application single – axis tracking units, to increase the efficiency of the photovoltaic conversion, in comparison with fixed systems optimally oriented. The design and physical realization of a measurement stand is presented. A photovoltaic module inclination angle correlation algorithm, for a selected location and a measurement period, is described. The measurements were conducted in natural lighting conditions for different weather conditions. The current – voltage and power – voltage characteristics were compared for a fixed and vertically variable configuration. The value of the electric energy generated by tested photovoltaic modules in both cases was determined.

3

Experimental investigation of gravity-assisted wickless heat pipes (thermosyphons) at low heat inputs for solar application

86%

Al-Joboory H. N. S.

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tom Vol. 41, no 2

257--276

EN

The performance of ten wickless heat pipes without adiabatic sections is investigated experimentally at low heat inputs 120 to 2000 W/m2 for use in solar water heaters. Three heat pipe diameter groups were tested, namely 16, 22, and 28.5 mm. Each group had evaporator lengths of 1150, 1300, and 1550 mm, respectively, with an extra evaporator length of 1800 mm added to the second group. The condenser section length of all heat pipes was 200 mm. Ethanol, methanol, and acetone were utilized as working fluids, at inventory of 25%, 50%, 70%, and 90% by evaporator volume respectively. The 22 mm diameter pipes were tested at inclination angles 30°, 45°, and 60°. Other diameter groups were tested at 45° only. Experiments revealed increased surface temperatures and heat transfer coefficients with increased pipe diameter and evaporator length, and that increased working fluid inventory caused pronounced reduction in evaporator surface temperature accompanied by improved heat transfer coefficient to reach maximum values at 50% inventory for the selected fluids. Violent noisy shocks were observed with 70% and 90% inventories with the tested heat pipes and the selected working fluids with heat flux inputs from 320–1900 W/m2. These shocks significantly affected the heat pipes heat transfer capability and operation stability. Experiments revealed a 45° and 50% optimum inclination angle of fill charge ratio respectively, and that wickless heat pipes can be satisfactorily used in solar applications. The effect of evaporator length and heat pipe diameter on the performance was included in data correlations.

4

Numerical study of heating transfer by natural convection in an inclined elliptical cylinder charged with nanofluid

72%

Amroune A. , Bouras A. , Taloub D. , Driss Z.

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tom Vol. 28, no. 3

28--41

EN

In this paper, thermal transfer with natural convection in a tilted annular cylinder with a Cu-water nanofluid has been numerically studied. The hot interior and cold exterior elliptical surfaces of the enclosure were maintained at constant temperatures Th and Tc , respectively. The governing equations were solved by the stream function-vorticity approach. The finite volume approach was utilized to discretise the controlling equations. The volume fraction range of the nanoparticles and the Rayleigh number was as follows: [...] respectively. The inclination angles were γ=30°,45°,and 60°. Results were given as isotherm contours, streamlines, average and local Nusselt numbers. The results indicate that the thermal transfer ratio increases with an increase in the tilt angle, regardless of the nanoparticle size values. and the impact of the inclination angle on the heating transfer rate is more important the higher the Rayleigh number and the more convection there is.

5

Investigations of the turbulent thermo-fluid performance in a circular heat exchanger with a novel flow deflector-type baffle plate

58%

Rahman M. A. , Dhiman S. K.

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tom Vol. 71, nr 4

art. no. e145939

EN

An axial flow tubular heat exchanger has been experimentally investigated to augment the heat transfer rate with a novel swirl flow of air past the heated tubes. The novel design has been based on circular baffle plates provided with trapezoidal air deflectors of various inclination angles. The arrangement of tubes is kept the same throughout the experiment, in accordance with the longitudinal airflow direction. The tubes maintained a constant heat flux condition over the surface. Four deflectors with equal inclination angles were developed on each baffle plate, generating air swirl inside a circular duct carrying the heated tubes that increase air-side turbulence and, consequently, the surface heat transfer rate. The baffle plates were placed equidistant from each other at variable pitch ratios. The Reynolds number was kept in the range of 16000– 28000. The effect of pitch ratios and inclination angles on the thermo-fluid performance of the heat exchanger was studied. The investigations revealed an average improvement of 3.75 times in thermo-fluid performance for an exchanger with a deflector baffle plate with a baffle inclination angle of 50_ and a pitch ratio of 1.4 when compared to other inclination angles and pitch ratios.