| 1. |
- Jin, Zhi-jiang, et al.
(författare)
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A parametric study of hydrodynamic cavitation inside globe valves
- 2018
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Ingår i: Journal of Fluids Engineering. - : ASME International. - 0098-2202 .- 1528-901X. ; 140:3
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Tidskriftsartikel (refereegranskat)abstract
- Hydrodynamic cavitation that occurs inside valves not only increases the energy consumption burden of the whole piping system but also leads to severe damages to the valve body and the piping system with a large economic loss. In this paper, in order to reduce the hydrodynamic cavitation inside globe valves, effects of valve body geometrical parameters including bending radius, deviation distance, and arc curvature linked to in/ export parts on hydrodynamic cavitation are investigated by using a cavitation model. To begin with, the numerical model is compared with similar works to check its accuracy. Then, the cavitation index and the total vapor volume are predicted. The results show that vapor primarily appears around the valve seat and connecting downstream pipes. The hydrodynamic cavitation does not occur under a small inlet velocity, a large bending radius, and a large deviation distance. Cavitation intensity decreases with the increase of the bending radius, the deviation distance, and the arc curvature linked to in/export parts. This indicates that valve geometrical parameters should be chosen as large as possible, while the maximal fluid velocity should be limited. This work is of significance for hydrodynamic cavitation or globe valve design.
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| 2. |
- Qian, Jin Yuan, et al.
(författare)
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Effects of dimple cone angles on heat transfer and pressure drop in a dimple jacketed heat exchanger
- 2017
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Ingår i: Proceedings of CHT-17 ICHMT International Symposium on Advances in Computational Heat Transfer, 2017. - 9781567004618 ; , s. 2013-2020
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Konferensbidrag (refereegranskat)abstract
- A Dimple Jacket Heat Exchanger (DJHE) is designed for the Chemical Post-Processing Integrated Equipment (CPPIE) to enhance the heat transfer performance during chemical reaction, crystallization and drying processes. In this paper, a 3D model of a DJHE is established. Dynamic variation of temperature inside the DJHE is compared with experimental data to validate the accuracy of the numerical method. Then, by choosing one dimple from the whole DJHE as the research object, the effects of different dimple cone angles on heat transfer and pressure drop characteristics are analyzed with the validated method. The results show that the dimple cone angle has an obvious effect on the heat transfer and pressure drop performance. This work can reduce the uncertain design of DJHE, and it can also be referred by similar research works on dimple surfaces.
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| 3. |
- Jin, Xin, et al.
(författare)
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Comparative evaluations of thermofluidic characteristics of sandwich panels with X-lattice and Pyramidal-lattice cores
- 2018
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 127, s. 268-282
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Tidskriftsartikel (refereegranskat)abstract
- This study compares the thermo-fluidic characteristics of sandwich panels with the X-lattice and the Pyramidal lattice at a given porosity and surface area density. The numerical model is validated against available experimental data at first. At a given Reynolds number in the range of 3100–5700, numerical results reveal that the X-lattice sandwich panel provides a 47–60% higher average overall Nusselt number. The special topology of the X-lattice induces counter-rotating spiral primary flow and more complex secondary flows, including one which becomes a longitudinal vortex later. The flow in the Pyramidal lattice sandwich panel is composed of a parallel primary flow and a counter-rotating vortex pair entrenched in the zone behind ligaments of the Pyramidal lattice. Compared with the Pyramidal lattice sandwich panel, endwall heat transfer of the X-lattice sandwich panel is enhanced by 75–97% and the ligaments surface heat transfer is enhanced by 85–97% at a given Reynolds number. It is also found that the friction factor of the X-lattice sandwich panel is about 2 times higher for the spiral primary flow and more complex secondary flows induced by the staggered ligaments. Finally, at a given pumping power, the cooling performance of the X-lattice is much better, too. Taking the identical fabrication method and cost into account, apparently the X-lattice is superior in engineering applications.
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| 4. |
- Shen, Han-Ming, et al.
(författare)
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Computational optimization of counter-flow double-layered microchannel heat sinks subjected to thermal resistance and pumping power
- 2017
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 121, s. 180-189
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Tidskriftsartikel (refereegranskat)abstract
- Various microchannel heat sinks are widely used to cool electronic chips, but they are often designed to be single-layer channels. To a certain extent, single-layered microchannel heat sinks can solve the problem of high heat flux. However, due to the limitation of pumping power, only a small coolant flow rate can be adopted; and the temperature of the heated plate is non-uniform. In this paper, the structure of double-layered countercurrent microchannel heat sinks is designed. The NSGA-II optimization algorithm is used to optimize the height ratio of the two layers and the length of the upper layer. The corresponding Pareto frontier is obtained. After validation of the optimization Pareto front, some validated characteristic cases are investigated numerically. The results of the optimization show that despite a conflict between reducing the thermal resistance and lowering the pumping power, there is an appropriate structure of the double-layered countercurrent microchannel heat sink optimized by the NSGA-II optimization algorithm. For the selected cases, Case 4 has the best thermal performance, because Case 4 not only has a smaller pumping power than Case 0, but also has a smaller thermal resistance than Case 0. Therefore, it is indicated that better thermal performance of microchannel heat sinks can be achieved through the optimization algorithm.
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