To fully utilize solar energy as a driving heat source, an experimental study was carried out of the thermodynamic performance of a standing-wave type thermoacoustic engine installed at various inclination angles. The...
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To fully utilize solar energy as a driving heat source, an experimental study was carried out of the thermodynamic performance of a standing-wave type thermoacoustic engine installed at various inclination angles. The test results show that the installation inclination angle of the thermoacoustic engine can exercise a remarkable influence on such parameters as the vibration-initiation temperature, vibration-fading temperature of the thermoacoustic system and temperature gradient in a plate stack during the initiation of vibration etc. When the nitrogen pressure in the system has reached 1.3 MPa, at the seven angles used during the experiment, the highest vibration initiation temperature is 484°C and the lowest, 428°C. These characteristics can provide an experimental basis for choosing an appropriate angle to lower the vibration-initiation temperature of the system. When the system is in a stable oscillation state, any change of the installation inclination angle has a relatively small influence on such thermodynamic characteristics of the system as pressure ratio and pressure vibration amplitude. These characteristics create favorable conditions for driving at different angles thermoacoustic engines operating in a stable oscillation state by utilizing an auto-tracking solar energy collector. The test results can well provide an experimental basis for the design of solar-energy-driven thermoacoustic engines.
A system has been established to conduct the experimental study of dynamic characteristics of shell-and-tube heat exchangers. Through experimental methods, an experimental study has been performed of the dynamic chara...
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A system has been established to conduct the experimental study of dynamic characteristics of shell-and-tube heat exchangers. Through experimental methods, an experimental study has been performed of the dynamic characteristics of heat exchangers with continuous spiral baffle plates, which have water and oil to serve as heat exchange working media. With the inlet flow disturbance representing equal percentage flow rate characteristics, studied were the dynamic responses to water and oil temperature at the outlet in four modes of flow rate disturbance. In the meantime, the effect of fluid disturbing quantity on the temperature rise at heat exchanger inlet and outlet at a certain Re number was also studied with a correlation equation between the temperature rise at the inlet and outlet of the heat exchanger and fluid disturbing quantity being obtained. The tests show that the dynamic response to the temperature of a liquid-liquid heat exchange system needs a comparatively long time. It has been found through the study that under a disturbance with a positive or negative flow rate, the change of temperature at the inlet and outlet of spiral-baffle plate heat exchangers assumes a linear relationship and the variation curve featuring temperature rise at the inlet and outlet has a symmetric feature at a positive or negative flow rate disturbance. A finite-difference numerical forecast model and artificial neural network one have been established respectively to dynamically forecast the outlet temperature at the heat exchanger oil side. The forecast results are in good agreement with the test values. The forecast results obtained from the neural network is better than those from the numerical simulation with the absolute value of the deviation being less than 1.3%, indicating that artificial neural network has a definite merit for engineering reference and applications when performing the discrimination of complicated systems.
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