Thermal and exergy assessment of solar chimney performance in various energy absorptions; using indoor experimental setu
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ORIGINAL
Thermal and exergy assessment of solar chimney performance in various energy absorptions; using indoor experimental setup Ramin Mehdipour 1
&
Ehsan Mohammadi 1 & Amir Mohammad Babaie Parsa 1 & Hassan Nahalekah 1
Received: 10 September 2019 / Accepted: 21 July 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Environmental pollution caused by burning fossil fuels, global warming, the greenhouse effect, and other factors has changed the approach of science to the use renewable energies. The main objective of this paper is to study the effects of diverse inputs (solar radiation) and collector geometries and also heat transfer of the solar chimney power plants (SCPP) model on the thermal and efficiency of the power plant. To achieve this purpose, an innovative setup of a solar chimney power plant is designed and a series of tests are performed. The setup is designed on a scale of 1/00 of an actual power plant. All tests are carried out in the indoor condition. Therefore, solar emission is simulated by heaters embedded in the floor of the collector. The new design of the collector of the present solar chimney power plants (SCPP) made it feasible for the user to change the canopy slope and the canopy height. It is shown that the canopy slope may influence the underneath airflow velocity and temperature and also changing the canopy geometry from divergent (inlet of the chimney) to convergent or collector-less form, decreases the amount of absorbed energy (usability) by the air inside the collector. In the present study, exergy of flow rate, Nusselt number, and Rayleigh number are calculated in three different geometries of solar chimney. It is shown that for the divergent geometry, increasing the input height improves the exergy value by 48% and 70%. On the other hand, average Nusselt value for divergent geometry is 193% and 780% higher than convergent and collector-less geometry respectively. Nomenclature Xin Exergy transferred to the system (kW) Xout Output exergy of the system (kW) Xdestroyed Exergy loss (kW) G Acceleration due to earth’s gravity (m.s-2) Gr Grashof Number Highlights • An experimental setup for solar chimney with novel design is fabricated and got tested. • The setup is indoor so ambient temp., solar radiation, wind, etc. can be controlled. • Ratio of energy transferred to that introduced to the collector (RET) is evaluated. • Nusselt Number as well as heat transfer coefficient are assessed in three different geometries. • Reasons for poor performance of common solar chimneys are widely discussed. • It is shown that thermal performance of divergent chimney is better than the other geometry. * Ramin Mehdipour [email protected] 1
Department of Mechanical Engineering, Tafresh University, Tafresh, Iran
H he he0 hic hich hoch k l L ˙ ic m ˙ ich m ˙ och m Nu Pstore Pr ˙ Q 0 ˙ Q 0r ˙ Q 0og ˙ Q ch ˙ Q loss
Ra s s0 T0
Convective heat transfer coefficient (W.m-2. K-1) Enthalpy of airflow in specified state (kj.kg-1) Enthalpy of reference (dead) state (kj.kg-1) Ent
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