Controllable Vibrating System To Enhance The Performance Of Heat Pipe Evacuated Tube Solar Collector . Abstract: Mechanical vibration is used to excite a heat pipe evacuated tube solar collector (HP-ETSC), where two (HP-ETSC’s) are built identically to compare the performance of the solar collector with and without applying vibration. A controllable vibration system was designed and manufactured for increased the total collector efficiency. The vibration system consists of a motor with adjustable rotating unbalanced mass and a control circuit. The velocity (frequency) of the motor is controlled by mean of an Arduino circuit that applies the controlling signal in the form of pulses over a certain period of time. The vibration is applied on one of (HP-ETSC’s) and the other is left in static condition under Iraq winter climatic conditions. The enhancement on the thermal performance at different frequency values (2, 4, 6, 8 and 10 Hz) and the three volumetric water flow rates are discussed. Results indicated that the evaporation and condensation heat transfer coefficients increased with vibrational frequencies, and the vibrational frequencies effectiveness depended on the water flow rate and the working conditions. The two heat transfer coefficients, hot water temperature and the total collector effectiveness of the HP-ETSC with controllable vibration system increased by 40%, 20%, and 22% during the test conditions

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