The evaporator is the main part of a quick-freeze equipment. There are many factors influencing the heat transfer coefficient of an evaporator. The most important factors among them are the fin shape, tube diameter, d...The evaporator is the main part of a quick-freeze equipment. There are many factors influencing the heat transfer coefficient of an evaporator. The most important factors among them are the fin shape, tube diameter, distance of fin space, frost, and velocity of air flow etc. They mainly influence the thermal efficiency of an evaporator, and therefore its thermal efficiency has direct relationship with the whole efficiency of the quick freeze plant. Evaporators with different structural types have different heat transfer efficiency, in order to obtain high efficiency structure of evaporator, 8 evaporator models with different fin shape, tube diameter and tube arrangement are analyzed and compared. The calculation results show that the integral waved fins, equilateral-triangle arranged small diameter tubes and varying fin-spacing has the highest heat transfer coefficient. The experimental result also shows that the evaporator with this type of structure has better thermal efficiency. The experimental result is in good agreement with the calculation result, it can instruct engineering design for usual designer. A real quick-freeze equipment is designed and put into production. The result shows that, compared with traditional domestic quick-freeze equipments, this equipment decreases by 40% in size and by 20% in energy consumption.展开更多
The underwater counter-rotation propeller non-cavitation noise has an obvious mod- ulation characteristic which is due to the interaction of flow and blade. A modulation mecha- nism is presented in this paper. A sound...The underwater counter-rotation propeller non-cavitation noise has an obvious mod- ulation characteristic which is due to the interaction of flow and blade. A modulation mecha- nism is presented in this paper. A sound pressure spectrum model is presented to describe its non-cavitation noise with application of generalized acoustic analogy method, the modulation mechanism is expressed with the improvement of sound pressure model. The power spectrum and modulation spectrum are presented by numerical simulation. Theoretical analysis and nu- merical simulation results are verified by the cavitation tunnel experiment. The modulation model of counter-rotation propeller is beneficial to the prediction modulation characteristics and identification of underwater high-speed vehicles.展开更多
The theoretical analysis and experimental research on Port/Starboard (P/S) discrimination in towed line array are proposed. Two methods resolving the P/S ambiguity with hydrophone triplets are introduced. By processi...The theoretical analysis and experimental research on Port/Starboard (P/S) discrimination in towed line array are proposed. Two methods resolving the P/S ambiguity with hydrophone triplets are introduced. By processing experimental data, the theoretical analysis is verified. The processing algorithm is extended to broadband signal. The research results show that the method based on optimum beamforming with triplets can be used to remove the port/starboard ambiguity. Also because of the simplicity of the method, it is expected to be implemented in practical towed line array sonar.展开更多
基金This project is supported by National Key Technologies R&D Programme,China (No.2001BA501A22).
文摘The evaporator is the main part of a quick-freeze equipment. There are many factors influencing the heat transfer coefficient of an evaporator. The most important factors among them are the fin shape, tube diameter, distance of fin space, frost, and velocity of air flow etc. They mainly influence the thermal efficiency of an evaporator, and therefore its thermal efficiency has direct relationship with the whole efficiency of the quick freeze plant. Evaporators with different structural types have different heat transfer efficiency, in order to obtain high efficiency structure of evaporator, 8 evaporator models with different fin shape, tube diameter and tube arrangement are analyzed and compared. The calculation results show that the integral waved fins, equilateral-triangle arranged small diameter tubes and varying fin-spacing has the highest heat transfer coefficient. The experimental result also shows that the evaporator with this type of structure has better thermal efficiency. The experimental result is in good agreement with the calculation result, it can instruct engineering design for usual designer. A real quick-freeze equipment is designed and put into production. The result shows that, compared with traditional domestic quick-freeze equipments, this equipment decreases by 40% in size and by 20% in energy consumption.
基金supported by the National Natural Science Foundation of China(11704345)the Key Laboratory of Science and Technology for National Defence Foundation(9140C290304140C29133)
文摘The underwater counter-rotation propeller non-cavitation noise has an obvious mod- ulation characteristic which is due to the interaction of flow and blade. A modulation mecha- nism is presented in this paper. A sound pressure spectrum model is presented to describe its non-cavitation noise with application of generalized acoustic analogy method, the modulation mechanism is expressed with the improvement of sound pressure model. The power spectrum and modulation spectrum are presented by numerical simulation. Theoretical analysis and nu- merical simulation results are verified by the cavitation tunnel experiment. The modulation model of counter-rotation propeller is beneficial to the prediction modulation characteristics and identification of underwater high-speed vehicles.
文摘The theoretical analysis and experimental research on Port/Starboard (P/S) discrimination in towed line array are proposed. Two methods resolving the P/S ambiguity with hydrophone triplets are introduced. By processing experimental data, the theoretical analysis is verified. The processing algorithm is extended to broadband signal. The research results show that the method based on optimum beamforming with triplets can be used to remove the port/starboard ambiguity. Also because of the simplicity of the method, it is expected to be implemented in practical towed line array sonar.
