Analysis of natural convection in IPWR type SMR test facility
In advanced and conventional reactors natural circulation plays an important role in cooling of core. This dissertation is based on modeling of a test facility using RELAP5/MOD 4.0. Test facility (TF) comprises of heating core, riser, helical coil heat exchanger, and shell and tube heat exchanger and down comer these components are joined with associate piping and fittings. In the TF, heating core is cooled by natural circulation. In this thesis, analysis of natural circulation depends on geometry and operational parameters. The primary objective of this thesis is to investigate the effects of riser height, riser diameter, Source and sink distance, power and secondary side mass flow rate on primary loop mass flow rate, which is established due to natural convection. Natural circulation loop of TF modeled with the aid of RELAP5/MOD 4.0 thermal hydraulic system code. Riser length=78 inch, Pressure= 1Bar, Pitch to diameter = 1.4, SS Flow rate = 0.45kg/s, ΔH = −5 inch, Riser Diameter = 6 inch and power 37.0kw. Primary loop mass flow rate is 0.17kg/s (612kg/hr), analytical solution mass flow rate is 0.18kg/s, average error is 12.8% in computational solution. This error reduces as power increases with constant intervals. The RELAP5/MOD 4.0 results give good agreement with analytical solution.
CFD investigating flow and heat transfer characteristics in a natural circulation loop
Natural circulation is the most important heat removal mechanism for passive safety systems in new-design nuclear power plants. It is important to investigate the flow and heat transfer characteristics related to the natural circulation mechanism. In this paper, a compressible three-dimensional (3-D) CFD model is proposed to investigate these phenomena in a natural circulation loop. The flow and heat transfer behaviors in a loop can be reasonably captured by the present model, which includes the secondary flow within the elbow and the thermal stratification in the horizontal pipe, etc. This model is also validated with the existing experimental data. Compared with the measured results including time histories of local maximum fluid temperature and temperature difference across the heater, and the relationship between Ress and Grm/NG, the present predicted results show good agreement. These comparisons reveal that the present CFD methodology can be applied in simulating the thermal–hydraulic characteristics related to the natural circulation mechanism in confidence.
Multilayer high density flex technology
The industrial trend of shrinking microelectronic devices while increasing the density of interconnections places great demands on the substrates upon which these devices are packaged. Multilayer flex circuits will provide the interconnection densities needed to meet these demands in a wide range of packaging and interconnection technologies. This paper discusses the development of ultra-high density flexible circuits. Processes and materials to fabricate fine line pitches from 12.5 /spl mu/m to 40 /spl mu/m are examined. Various microvia structures, through hole and blind via, are demonstrated. A test vehicle was designed and built for BGA packages to illustrate the density capability. A four-layer structure is demonstrated by using Z-connection to connect two layer pairs. Electrical, mechanical, and reliability test results are presented to show the selection of flex substrate material, Z-connection methodology and fabrication processes. A cost comparison of high-density flex to alternative substrates is discussed to identify potential.