Abstract
Solar energy is a viable source to fulfill the energy demands of a solar rich country such as Pakistan. Various types of solar thermal technologies are being used around the world, including flat plate, evacuated tube, and compound parabolic trough collectors. However, the performance of these collectors is strongly influenced by the nature of work fluid. Utilization of nanofluids with high thermal conductivity is a very attractive way to further enhance the performance of solar collectors. Therefore, this study deals with the characterization and thermal performance enhancement of compound parabolic collectors (CPC) by using non-metallic nanofluids such as water-based multi-wall carbon nano tubes (H2O-MWCNT) with a thermal conductivity of 3000 W/m·K. In the current work, multiple tests are performed to analyze the thermal conductivity and stability of nanofluids through thermal analyzer and UV-Vis Spectroscopy, respectively. Test results show that the thermal conductivity of water-based MWCNT nanofluid is 37% higher than water at a concentration of 0.075%. Prepared nanofluids are then employed in CPC, and detailed experimentation is performed by varying the concentration of nanoparticles (0.025, 0.05, 0.075%) and their flow rate (0.015, 0.02 kg/s). Maximum temperature difference of 10.5oC with volumetric concentration of 0.075% is achieved in experimental analysis at flow rate 0.015 kg/s. Thermal efficiency enhancement of 19.37% with volumetric concentration 0.075% is recorded as compared to water at flow rate 0.015 kg/s.
Highlights
SWCNT/Water nanofluids were used in flat plate collector, and heat transfer enhancement of 95.12% and 26.25% was obtained for 0.3% and 0.1% volumetric concentration, respectively [1]
MWCNT/Water nanofluids were utilized and heat transfer enhancements of 16%, 21% and 34.13% were achieved for volumetric concentrations of 0.01%, 0.05% and 0.1% respectively [2]
0.05% wt% MWCNT/water nanofluids used in a heat-pipe-evacuated tube solar collector and maximum thermal efficiency of 55% were achieved [3]
Summary
SWCNT/Water nanofluids were used in flat plate collector, and heat transfer enhancement of 95.12% and 26.25% was obtained for 0.3% and 0.1% volumetric concentration, respectively [1]. MWCNT/Water nanofluids were utilized and heat transfer enhancements of 16%, 21% and 34.13% were achieved for volumetric concentrations of 0.01%, 0.05% and 0.1% respectively [2]. In another study, distilled-water-based graphene nanofluids were used in flat-plate solar collector and heat transfer enhancement of 24.09% was recorded for 0.1 wt% at flow rate of 1.5 L/min [4]. SWCNT/water nanofluids were utilized in an evacuated tube solar collector and thermal efficiency of 93.43% for 0.2 vol.% at 0.025 kg/s flow rate was recorded [5]. The stability of these fluids is analyzed with the help of UV-Vis spectrophotometer
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