Thermal Performance of an Evacuated U-Tube Solar Collector Using TiO2/EG-Water Nanofluid
AbstractIn this study the effect of nanofluids on collector performance was numerically investigated when using as working fluids in solar collectors which are commonly used in solar energy applications. Nanofluids are produced by adding nanoparticles to a base fluid as known. Thermophysical properties of base fluids change. The most important property of nanofluids is thermal conductivity enhancement. In this study ethylene glycol – water mixture was used as a base fluid which is especially used as cold climates for reducing freezing point. The reasons for this are expanding the range of working temperature and preventing the flow from higher density and viscosity of ethylene glycol at the same time. TiO2/EG-Pure Water nanofluids were used as working fluids in an evacuated U-tube solar collector at 1.0 – 4.0% volumetric concentrations with 30- 70% EG-PW base fluid for determining the effect of nanofluids on collector thermal efficiency. An evacuated tube solar collector with copper U-tube was modeled in FLUENT 17.0 and thermal efficiency of it was calculated by solving of flow field of the collector. 18.1% enhancement was obtained as maximum in thermal efficiency when using nanofluid as a working fluid. It was determined that the flow rate of the fluid was a significant parameter on thermal efficiency of the solar collector. The highest collector efficiency was obtained at 4.0% nanoparticle volume concentration and ṁ=0.045 kg/s.