In the present work, the performance of aluminum oxide and deionized water nanofluid used as heat transfer fluid on a parabolic trough solar collector system with hot water generation tank is evaluated. The parabolic trough solar collector is developed using easily and locally accessible materials. Five different concentrations of aluminum oxide and deionized water based nanofluid from 0.5-2.5% is prepared by the magnetic stirrer initially and then the mixture is subjected to ultrasonication process to break aggregates with the absence of surfactant. The prepared nanofluids are allowed to flow through the absorber which is located at a focal point of the solar collector. The performance of nanofluid is compared with pure deionized water. The test is conducted from 8.00 a. m. to 16.00 p. m. daily in the whole length of the test span. The heat transfer fluid is allowed to flow at a mass-flow rate of 0.020 kg/s and 0.09246 m/s velocities. The maximum solar radiation is 821 W/m2, and maximum efficiency is observed at noon time 60.41% for deionized water and 60.49% for 2.5% volumetric fraction of alumina nanofluid. The efficiency enhancement was 3.90% than deionized water. The influence of the critical parameter on the performance is also examined.
In the quest for energy conservative building design, there is now a great opportunity for a flexible and sophisticated air conditioning system capable of addressing better thermal comfort, indoor air quality, and energy efficiency, that are strongly desired. The variable refrigerant volume air conditioning system provides considerable energy savings, cost effectiveness and reduced space requirements. Applications of intelligent control like fuzzy logic controller, especially adapted to variable air volume air conditioning systems, have drawn more interest in recent years than classical control systems. An experimental analysis was performed to investigate the inherent operational characteristics of the combined variable refrigerant volume and variable air volume air conditioning systems under fixed ventilation, demand controlled ventilation, and combined demand controlled ventilation and economizer cycle techniques for two seasonal conditions. The test results of the variable refrigerant volume and variable air volume air conditioning system for each techniques are presented. The test results infer that the system controlled by fuzzy logic methodology and operated under the CO2 based mechanical ventilation scheme, effectively yields 37% and 56% per day of average energy-saving in summer and winter conditions, respectively. Based on the experimental results, the fuzzy based combined system can be considered to be an alternative energy efficient air conditioning scheme, having significant energy-saving potential compared to the conventional constant air volume air conditioning system.
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