Browsing by Author "Kayapunar A."

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    A comparative investigation of the effect of honeycomb core on the latent heat storage with PCM in solar air heater
    (Elsevier Ltd, 2019) Abuşka M.; Şevik S.; Kayapunar A.
    The aims of this study were to comparatively investigate the effect of using PCM and honeycomb as the internal fin structure in the PCM panel on the thermal performance of solar air heater. The tests performed at six air mass flow rates from 0.008 to 0.048 kg/s. The heat storage material was tested in two forms, PCM with honeycomb core in the first heater (Type I) and only PCM in the second heater (Type II). The third heater (Type III) with a flat absorber plate (without PCM) was used for comparison. The average day-time thermal efficiency of the Type I-II heaters with PCM increased from 8.4% to 9.0% for the mass flow rates of 0.032, 0.04, and 0.048 kg/s, while from 0.8% to 8.0% decreased for the mass flow rates of 0.008, 0.016 and 0.024 kg/s. The use of honeycomb as the internal fin structure significantly reduces the charge-discharge time, while slightly reducing the instantaneous-daily thermal efficiency, and provides a temperature increase of up to 8.8 °C at the PCM-temperature. The daily thermal efficiency comparison between heaters with PCM was in favor of the heater without honeycomb at values ranging from 0.1% to 4.4%. Taking into consideration the daily thermal efficiency, the Type I-II heaters with PCM are more efficient between from 2.6 to 22.3%, especially at high mass flow rates. It took approximately one hour to equal the outlet air temperature of the Type-III with the inlet air temperature. In PCM heaters, the inlet-outlet temperatures are approximately equal to 6 to 10 h. © 2018 Elsevier Ltd
  • No Thumbnail Available
    Item
    Comparative energy and exergy performance investigation of forced convection solar air collectors with cherry stone/powder
    (Elsevier Ltd, 2019) Abuşka M.; Şevik S.; Kayapunar A.
    The purpose of this study is to design new solar air collectors (SACs), to ensure that designed SACs continue to operate in cloudy weather and after sunset and to evaluate in terms of energy and exergy whether the cherry stone/powder will be appropriate to use as a sensible thermal energy storage (STES)material. The experiments were performed for a powdered cherry stones SAC (Type I), a cherry stones SAC (Type II), and a flat plate SAC (Type III)at seven different air mass flow rates (from 0.004 kg/s to 0.048 kg/s). Average thermal efficiency fluctuated between 6.05% and 39.99%, depending on the air mass flow rates under which the experiments were performed and whether the collectors have heat storage. The maximum difference in daily collector efficiency is in Type II, with a slight difference from Type I, which was 18.7% higher than the Type III. The inlet-outlet air temperatures of Type I and Type II were equaled 5 and 4 h after sunset, respectively, compared to the flat plate collector. The exergy efficiency ranged from 1% to 7% during the charging period. As a result, it can be seen that the use of cherry stone/powder as a STES material is promising in contributing to the collector sustainability. © 2019 Elsevier Ltd
  • No Thumbnail Available
    Item
    Experimental analysis of solar air collector with PCM-honeycomb combination under the natural convection
    (Elsevier B.V., 2019) Abuşka M.; Şevik S.; Kayapunar A.
    Phase change material (PCM) is at the head of materials commonly used in latent heat storage. However, usually the main problem is that the heat conductivity of PCMs is low. Therefore, a novel solar air collector (SAC) combined the PCM-Rubitherm RT54HC with aluminum honeycomb was manufactured and investigated the effect of using honeycomb core on the collector thermal performance regarding heat storage with PCM under natural convection conditions. In the experiments, the heat storage material was tested in two forms with 26 kg capacity, PCM with honeycomb core in the first collector (type I) and only PCM in the second collector (type II), and also the third collector (type III) with a flat absorber plate for comparison. The first collector reached the PCM melting point about 50 min ago. Also, when we consider the peak point, an apparent 10 °C advantage is achieved in sensible heat storage in favor of type I. It is observed that the honeycomb core used as a heat transfer enhancer is effective in shortening the charge-discharge times, also a noticeable difference in sensible heat storage during the noon. The production of useful energy in Type I lasted 469 min and 539 min longer than type III, respectively. The thermal efficiencies under daylight were calculated as 10.1%, 10.9% and 13.6%, respectively. As a result, it can be said that the use of honeycomb core as heat conductivity enhancer material is very functional, in particular during the discharge period. © 2019 Elsevier B.V.
  • No Thumbnail Available
    Item
    Experimental performance analysis of sensible heat storage in solar air collector with cherry pits/powder under the natural convection
    (Elsevier Ltd, 2020) Abuşka M.; Şevik S.; Kayapunar A.
    It is important to enhance the availability of SACs either in cloudy weather or after sunset for space heating and agricultural drying process. In this context, this study aims to determine experimentally thermal performance of cherry pits as sensible heat storage material under natural convection conditions. In the first collector (Type I), powdered cherry pits (32 kg) were used as heat storage material and cherry pits (24 kg) were used in the second (Type II). The third collector (Type III) with a flat absorber plate is for comparison. Although the maximum thermal efficiencies were found 26.54% and 27.03% for Type I and Type II respectively, average thermal efficiency of Type I is higher than Type II. According to the test results, the inlet-outlet temperatures were equalized 46 min for the Type III, 200 min for Type II, and 270 min for Type I collector after sunset. As a result, it can be said that the use of cherry pits and powder as sensible heat storage material is promising. © 2018 Elsevier Ltd
  • No Thumbnail Available
    Item
    Experimental and numerical investigation of thermal performance in solar air heater with conical surface
    (Springer Science and Business Media Deutschland GmbH, 2021) Abuşka M.; Kayapunar A.
    The absorber plate surface modifications of a solar air heater (SAH) increase the convective heat transfer rate of the inlet air. Forced convection heat transfer of air in a SAH with a staggered arrangement of conical obstacles has been carried out experimentally and numerically at mass flow rates (0.04, 0.08, and 0.1 kg/s) under ambient conditions for the aim of to enhance the thermal efficiency and to create proper volume for heat storage material in terms of the effectiveness of the SAH. The thermal efficiency for the absorber with conical obstacles was 14.0, 14.6, and 11.8% higher than the flat absorber plate for the mass flow rates, respectively. The results show that the number of Nusselt obtained in conical surface experiments was highest for all cases tested regardless of Reynolds number. The experimental results are compared with the numerical results obtained by the CFD method. The model results indicate good agreement with the experimental results. Also, the results show that the heat transfer in front of the conical elements is high, and the back is low; in the smooth absorber, a linear velocity distribution is seen along the channel; however, in the conical surface absorber, the velocity distribution due to turbulence is very variable. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.