Papers by Keyword: Filling Ratio (FR)

Abstract: Closed loop pulsating heat pipe (CLPHP) is a relatively new two-phase passive heat transfer device to suit present requirement of high heat flux dissipation in modern electronic components. The operating mechanism of CLPHP is not well understood and the present state of the technology cannot predict required design parameters for a given task. The aim of research work presented in this paper is to better understand thermal performance of CLPHP. A series of experimental investigation were conducted on a multi-turn CLPHP made of copper capillary tube of 2-mm inner diameter. Two kinds of working fluids viz. ethanol and acetone were employed. The influence characterization has been studied for the variation of heat input and filling ratio (FR) of the tested CLPHP. Thermal performance of the CLPHP is evaluated by heat transfer and thermal resistance. The results strongly demonstrate the effect of heat input and FR of the working fluid on thermal performance of the device.

Abstract: Accuracy of the net-shape manufacturing such as forging becomes critical as the process depends on many factors. Defect will harm the assembly tend to affect the performance of the part. Therefore, it must be detected and minimized it as soon as the manufacturing begins. Small size and complexity of the part limits the defective part to be assessed. The paper presents an investigation on the defect of the cold embossing pin. In this work, the effect of design and process parameters to the formation of defect was studied using 2-D FE analysis. The defect can be measured based on the incomplete filling of the region from the FE result. The results show that, the FE observations are in good agreement with the experimental result.

Abstract: The free vibration experiments for the NOPD frame structure were performed to investigate the dynamic characteristics of the frame. The influences of factors such as particle filling ratio, particle filling scheme and vibration direction of the frame on the damping effect are discussed by means of test data. Test results indicate that the particle filling ratio is a principal influencing factor for the damping effect of the frame. Under the same particle filling scheme and filling ratio, the damping increments for out plane vibration of the frame with smaller structural rigidity are normally larger than those for in plane vibration with larger structural rigidity. Within the three schemes of particle filling, the most prominent damping improvement exists in the particle-in-beam scheme under the same filling ratio and the corresponding maximum damping increment reaches 218% for out plane vibration. To obtain the most significant particle damping effect, the most effective scheme of particle filling is to put particles into the cavities of components with large vibration displacement.

Abstract: The dual-step dual-team holographic method to fabricate square lattices is proposed. The effect of intensity threshold was analyzed by calculating the intensity spatial distribution. The photonic band gap properties of two-dimensional square lattice fabricated by holographic lithography are investigated numerically. The influences of intensity threshold and dielectric contrast on photonic gap are comprehensively studied by plane wave expansion method. Calculations of band structure as a function of the intensity threshold show that the full photonic band gap does not increase monotonically with dielectric contrast ratio, but has a peak value instead by studying the relation between the complete PBG and the dielectric contrast.

Abstract: The effect of intensity threshold on the filling ratio was analyzed by calculating the intensity spatial distribution. The photonic band gap properties of two-dimensional triangular lattice fabricated by holographic lithography are investigated numerically. The influences of intensity threshold and dielectric contrast, on photonic gap are comprehensively studied by plane wave expansion method. Calculations of band structure as a function of the intensity threshold show that the PBG of positive structure opens for TM and TE polarization separate, and the negative structure has the complete PBG. The complete PBG does not increase monotonically with dielectric contrast ratio, but has a peak value instead by studying the relation between the complete PBG and the dielectric contrast ratio. The optimal dielectric contrast is 22 when intensity threshold is 0.2.

Abstract: In order to utilize low enthalpy geothermal heat sources, a thermosyphon is a good device which can extract heat without using electric power. The heat transfer in the thermosyphon occurs through the circulation of a working fluid through a sequence of evaporation, vapor transfer, condensation, and liquid return. A two-phase thermosyphon system using carbon dioxide (CO2) as a working fluid has been investigated both experimentally as well as theoretically. Carbon dioxide is the only non-flammable and non-toxic fluid that has the potential to offer environmental safety in a system. A copper tube thermosyphon of total length of 1,000 mm with inside and outside diameters of 9.9 mm and 12.7 mm was developed by consisting of evaporator and condenser sections. The temperature distribution along the thermosyphon was monitored and theninput heat to evaporator section and output heat from condenser were measured as well. The effects of temperature difference between evaporator and condenser section and coolant mass flow rates on the performance of the thermosyphon were determined. The results indicate that the heat flux transferred increased with increasing coolant mass flow rate and temperature difference between evaporation and condenser section. The experimental analysis of the thermosyphon system confirms that the proposed system must be a reliable and highly efficient as well as environmentally friendly alternative to common ground-coupled systems.