Investigation Of Natural Circulation Solar Energy System Utilizing Nanofluid

Nanofluids and Solar Electric Generating System are two of the hot spots of current researches. We combine the Solar Parabolic Trough Collector Techonology, Heat pipe and Nanofluids, and design a PTC Natural circulation system utilizing Nanofluids as the Heat Transfer Fluid.The system is designed to generate saturated steam of0.5-0.8Mpa,and the power is50KW.In order to get the stable and efficient heat transfer fluid,we investigate the stability and heat transfer character of nanofluid.Brownian dynamics method is conducted to simulate the influencing factors,focusing on the effects of the particle sizes,volume fraction and ζ potentials.The simulation take into account the interaction between the coagulation and sedimentation of nanoparticles.Natural convection of nanofluids is investigated with mixture model and DPM separately. The incompressible Navier-Stokes equations are used in numerical simulation. Based on the Euler-Lagrangian method, nanoparticles are tracked in the Lagrangian coordinate, and two-way couplings are considered between nanoparticles and fluid, including the momentum and thermal couplings. So the interactions between nanoparticles and fluids in the microcosmic scale can be clearly capturef in the numerical simulations.The drag force,gravity force,Brownian force,thermophysics force is considered which take great effect in microscopic.We set up the natural circulation solar system in LangFang.The systems consists of line focus collectors with the rotation axis oriented north-south,Flabeg glass mirrors as reflectors,and our designed concentric cannula absorbers. Thermal energy is transfer to the evaporator utilizing heat pipe, and saturated steam of qualified is generated through controlling the pressure of the evaporator.We investigate the starting character of solar collector and conclude that the system could generate steam stably,and the efficiency is35.04%with water as the heat ransfer fluid at0.5Mpa.Preliminary study of utilizing nanofluids as heat transfer fluid is also conducted,and the heat transfer enchancement is7%compared with water. The influence factor of system effienciey is analysed,as to our system,the main factor is the incident angle and its induced edge effect,besides the heat dissipation of the system loop.