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The scroll compressor is a kind of positive-displacement compressor applied in refrigeration systems, heat pump systems, and air conditioner systems. Using the spring smoothing method and considering the heat transfer, the numerical simulation model of the scroll compressor is established under standard working conditions. The results show that the CFD model is well validated by the experiment result. The compressor performance and the working process are analyzed. The pre-compression and the over-compression phenomenon are also studied. Moreover, the temperature distribution and velocity distribution of gas flow in the compressor are illustrated. The result shows that the pre-compression can improve the performance of the scroll compressor and the optimization of the suction channel geometry can provide a smoother suction process. Under the combined effect of the pre-compression and heat transfer, the refrigerating capacity is increased by approximately 0.54 kW and the volume efficiency is increased by approximately 2.2%. The additional power loss due to over-compression is 47.6615 W, and the setting of over-compression discharges can reduce the pressure and power loss. This study is helpful to the performance prediction and the structural optimization of the scroll compressor. [ABSTRACT FROM AUTHOR]

Pressure pulsation has a critical importance in the design of refrigerant compressor since it acts as a noise and vibration source. For capturing the pressure pulsation and the transient flow structure, the numerical simulation based on detached eddy simulation and dynamic mesh approach was performed. Numerical results agree well with experimental data in the frequency band of 1000–2900 Hz. The results show that the vortex flows arise when the pressure disturbances propagate in the refrigerant gases and impact against the wall leading to the dramatic increase of the sound pressure level (the frequency band is about over 1800 Hz) in the cylinder and the noise radiated from compressor shell. Furthermore, we employed the numerical model to analyze the noise reduction mechanism of the muffler hole in the cylinder wall. [ABSTRACT FROM AUTHOR]

Abstract: Different chemical state of titanium oxide films were deposited on commercially pure Ti (CP Ti) by reactive DC magnetron sputtering under different oxygen flow rates to examine a possibility of their applications to endovascular stents. The chemical composition and crystal structure of the obtained films were analyzed by XPS and XRD, respectively. In dependence on the deposition parameters employed, the obtained films demonstrated different mixture of anatase TiO2, Ti2O3, TiO and Ti. The wettability of the films was measured by the water contact angle variation. By formation of titanium oxide film on CP Ti, contact angle was decreased. In order to modify and control the surface wettability, the resultant TiOx films were etched subsequently by different plasma. The wettability was influenced by etched process according to the decreased contact angle values of etched TiOx film. Furthermore, TiOx films became highly hydrophilic by ultraviolet (UV) irradiation, and returned to the initial relatively hydrophobic state by visible-light (VIS) irradiation. The wettability of the TiOx film was enabled to convert between hydrophilic and hydrophobic reversibly by alternative UV and VIS irradiation. By adjusting deposition parameter and further modification process, the wettability of the TiOx films can be changed freely in the range of 0–90°. [Copyright &y& Elsevier]