MWCNT와 Fe3O4 이성분 나노유체 적용 태양열 집열기의 성능 분석

Abstract

In this paper, when the MWCNT, Fe3O4, MWCNT-Fe3O4 binary nanofluids were applied into the flat plate and evacuated tube solar collectors as working fluid, the performance of solar collector was investigated experimentally. The experiment was conducted with a variation of the concentration of nanofluid, size of nanoparticle, and the mass flow rate of working fluid. In addition, Based on the performance of solar collector using MWCNT and Fe3O4 nanofluid, the MWCNT-Fe3O4 binary nanofluid was fabricated and its performance was analyzed with operating conditions. When MWCNT nanofluid was used as a working fluid in flat plate and evacuated tube solar collector, the maximum efficiency was 87.5% at the mass flow rate of 0.047 kg/s. At this case, the MWCNT nanoparticle size and nanofluid concentration was 20 nm and 0.005vol%. In case of evacuated tube solar collector, the maximum efficiency was 75.6% when 20 nm-0.005 vol% MWCNT nanofluid was used. When MWCNT nanofluid was applied into the flat plate and evacuated tube solar collector, the maximum efficiency was improved by 39.6% and 37.7%, respectively, compared to that when the water was used. The maximum efficiency was 71.6% and 69.8% in the flat plate and evacuated tube solar collector, respectively, when the Fe3O4 nanofluid was used. At this case, the Fe3O4 nanoparticle size and nanofluid concentration was 30 nm and 0.015vol%. Besides, when 0.015vol%-Fe3O4 nanofluid was used in the flat plate and evacuated tube solar collector, it was confirmed that the maximum efficiency was improved by 14.2% and 27.1%, respectively, compared to that when the water was used. MWCNT-Fe3O4 binary nanofluid was also used as a working fluid in flat plate and evacuated tube solar collector. When Case 3 (0.005vol%-MWCNT & 0.01vol%-Fe3O4) binary nanofluid was applied into the flat plate solar collector, the highest efficiency was 80.3% which was about 28.1% higher than that using water. When Case 3 (0.005vol%-MWCNT & 0.01vol%-Fe3O4) binary nanofluid was applied into the evacuated tube solar collector, the highest efficiency was 79.8% which was about 45.4% higher than that using water. Form the experimental result, the maximum efficiency using Case 3 (0.005vol%-MWCNT & 0.01vol%-Fe3O4) was higher than Case 4(0.005vol%-MWCNT & 0.015vol%-Fe3O4) which was made by mixing of optimum concentration for MWCNT and Fe3O4 nanofluid, respectively. The performance sensitivity of flat plate and evacuated tube solar collector with operating parameters was analyzed when water, Al2O3, CuO, MWCNT, Fe3O4, and MWCNT-Fe3O4 binary nanofluid were used. The operating parameters used in the performance sensitivity analysis were the concentration of nanofluid, solar radiation, temperature parameter and mass flow rate of working fluid. When the MWCNT nanofluid was used in the flat plate and evacuated tube solar collector, the performance of solar collector was the most sensitive to the concentration of nanofluid, solar radiation, temperature parameter and mass flow rate of working fluid. In order to overcome this problem, it was confirmed that the performance sensitivity of solar collector using MWCNT-Fe3O4 binary nanofluid was reduced with operating conditions. By using this study, it is possible to provide the optimal design data for the high efficiency solar collector according to the type of nanofluid.