Abstract
Recently, nanofluid application as a heat transfer fluid for a closed-loop solar heat collector is receiving great attention among the scientific community due to better performance. The performance of solar systems can be assessed effectively with the exergy method. The present study deals with the thermodynamic performance of the second law analysis using graphene nanoplatelets nanofluids. Second law analysis is the main tool for explaining the exergy output of thermodynamic and energy systems. The performance of the closed-loop system in terms of energy and exergy was determined by analyzing the outcome of field tests in tropical weather conditions. Moreover, three parameters of entropy generation, pumping power and Bejan number were also determined. The flowrates of 0.5, 1 and 1.5 L/min and GNP mass percentage of 0.025, 0.5, 0.075 and 0.1 wt% were used for these tests. The results showed that in a flow rate of 1.5 L/min and a concentration of 0.1 wt%, exergy and thermal efficiencies were increased to about 85.5 and 90.7%, respectively. It also found that entropy generation reduced when increasing the nanofluid concentration. The Bejan number surges up when increasing the concentration, while this number decreases with the enhancement of the volumetric flow rate. The pumping power of the nanofluid-operated system for a 0.1 wt% particle concentration at 0.5 L/min indicated 5.8% more than when pure water was used as the heat transfer fluid. Finally, this investigation reveals the perfect conditions that operate closest to the reversible limit and helps the system make the best improvement.
Highlights
Introduction published maps and institutional affilNowadays, different types of solar systems can provide energy for many high-energy demand applications [1]
We focus on evaluating the expanded energy collection, exergy, entropy generation and pumping power performance of the evacuated heat pipe solar collector based on our previous research under given operating conditions for thermal performance assessment under actual field conditions in a tropical region of Malaysia
To determine the optimum particle concentration and flow rate for maximizing solar collector thermal efficiency, several factors have been determined, which will be explained
Summary
The heat transfer (Qu ) to the nanofluid is determined from the following equation: Qu = mc p T out − T in (1). Where c p is specific heat capacity, T in is inlet temperature, T out is outlet temperature and m is the mass flow rate. The solar energy absorption by collector (Qin ) as input energy is calculated from the following equation: Qin = AC S (2). Where AC is the solar energy collection area of ETSC and S presents the solar radiation. The total energy efficiency of the system (η) is determined by dividing the heat transfer to nanofluid and energy input as follows [38]: η=
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