بررسي تجربي عملكرد كلكتور خورشيدي به روش جذب مستقيم

چكيده انگليسي :

11 Experimental study of direct absorption solar collector performance Mohsen Khoshnoudi m khoshnoudi@me iut ac ir Date of Submission January 15 2014 Department of Mechanical Engineering Isfahan University of Technology Isfahan Iran Degree M Sc Language FarsiSupervisor Ali Akbar Alemrajabi rajabi@cc iut ac irAbstractAfter industrial revolution energy consumption increased sharply so threat of energyshortages led scientists to find new sources of energy During past decades the price of fossilfuels has increased dramatically Due to increasing and harmful effect of using fossil fuels onthe environment renewable energy especially solar energy should be given more attentionthan what has been given before The use of concentrated sunlight as a thermal energy sourcefor production of electricity promises to be one of the most viable options to replace fossil fuelpower plants However the peak efficiencies of existing fossil fuel combined cycle powerplants exceed 505 while those of concentrated solar power CSP plants are below 205 Mostconcentrated solar thermal technologies today use receivers with absorbing surfaces to convertsolar energy from its radiative form into thermal energy Although surface based receivers areefficient at solar to thermal conversion the temperature difference leads to significantemissive losses Alternatively in a volumetric receiver design concentrated solar radiation isdirectly absorbed and more uniformly distributed in the working fluid which decreases thetemperature difference between the collector and the fluid One of the proposed ways toincrease the efficiency of solar collectors with maintaining the simplicity of the system isdirect absorption of solar energy by the bulk of fluid This study at first presents the parabolicconcentrator collectors of direct absorption to investigate the efficiency of the systemcontaining deionized water and then the efficiency of the collector containing aluminum oxidenanofluid with a volume fraction of 0 1 0 2 and 0 35 With increasing volume fraction at lowflow rates between 10 50 L hm2 efficiency has an acceptable process but at higher flowrates efficiency reduces greatly Collector efficiency containing an aluminum oxide nanofluidwith a volume fraction of 0 35 was evaluated at about 655 Increasing volume fraction ofnanoparticle increases the viscosity of nanofluid wich would increase exponentially foraluminum oxide nanofluid On the other hand using nanofluid with low volumetricconcentrations has little effect on the pumping power of the cycle As the volume fraction ofnanofluid increases the stability decrease and particles aggregate and deposit more quickly somust be searched for an optimal point Investigations have shown that with increasing volumefraction more than 0 65 thermal properties of nanofluids did not increase while stabilitydecreased greatly Finally for reducing heat losses and increasing the efficiency of the systemsome guidelines will be outlined

خشنودي، محسن

بررسي تجربي عملكرد كلكتور خورشيدي به روش جذب مستقيم

انرژي خورشيد , كلكتور سهموي , نانو سيال اكسيد آلومينيوم , بازدهي