Papers by Keyword: Header

Abstract: In order to cope with ever increasing demands from the electronic, automotive and aerospace industries, cooling devices have to be small in size, light-weight and of high performance.The search for a more efficient cooling technology becomes one of the bottle neck problems of the further development of the electronic and automotive industry. Microchannel liquid cooling is one of the candidates for this purpose. The most important parameter in the microchannel is the distribution of the coolant inside the channel. A uniform flow in the microchannel leads to uniform heat transfer.A numerical simulation is carried out to minimize the flow maldistribution inside the microchannel. The microchannel was made as wavy shaped channel. There are six channels with hydraulic diameter of 1mm each. Header is the major part in the microchannel which supplies fluid into different channels. In this work, five different shapes of the header were considered namely circular, frustum conical, rectangular, triangular and trapezoidal. From the simulation results it was found that the mal-distribution is significantly affected by flow rate and shape of the header.

Abstract: Three liquid-gas separator units were designed and manufactured from transparent acrylic resin based on the concept of a new kind of validated high performance condenser. The separator units had different spaces between baffle and outlet arm or different header diameters. A visualization cold state test system was set up to explore the basic principle of liquid-gas separation and liquid discharge process, using air and water as the working fluids. Four kinds of liquid flow patterns were observed by the liquid staining and high-speed photography at inlet air superficial velocities from 1m/s to 15m/s and water superficial velocities from 0.0015m/s to 0.06m/s. The effects of operation conditions and structure parameters on the separation efficiency of the liquid-gas separator units were investigated. The results showed that under the experimental conditions, the separation efficiency was more than 70%, the separation efficiency could be improved by increasing the space between baffle and outlet arm as well as the header diameter.

Abstract: In order to study reasonable structure of rectangular tapered header, the methed of computatation fluid dynamic was used to research pulp distribution characteristic of the rectangularly tapered pulp distributor and to optimize its structure. The results show that velocity distribution and pressure distribution in the tapered header were not uniform and the mass flow rate out of branch pipes was obviously accrescent from inlet of header to outlet of header. There was remarkable deviation comparison to expected value of mass flow rate. The real backwall shape of the rectangularly tapered head was a complicated curve that was obviously different to the simplified header at area of the inlet and the outlet. The pressure distribution in the optimally designed header was more uniform and the pressure curve at the location corresponding to branch pipes was nearly a horizontal line. The mass flow rate distribution out of the branch pipes was more uniform else and was close to the expected value curve. The deviation of the mass flow rate in every branch pipe was less than 1%.

Abstract: The flaws such as crack or slag inclusion, in the welded seam of header of a 300MW steam turbine generator unit, were detected by the ultrasonic non-destructive inspection. Based on the crack modeling, the finite element method (FEM) was used to calculate and analyze the displacement field, stress field and stress intensity factors of the cracks under the conditions of warm start, cold start and normal operation, and the residual service life was predicted. Analyzing results showed that these flaws would not bring about primary brittle fracture and propagation of crack was harmless to safe in operation.