The study of refrigerant-based nanofluid boiling and two-phase flow phenomena is still in its infancy. This field of research provides many opportunities to study new frontiers but also poses great challenges. To summ...
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The study of refrigerant-based nanofluid boiling and two-phase flow phenomena is still in its infancy. This field of research provides many opportunities to study new frontiers but also poses great challenges. To summarize the current status of research in this newly developing interdisciplinary field and to identify the future research needs as well, this paper presents a comprehensive review of nucleate pool boiling, flow boiling, condensation and two-phase flow of refrigerant-based nanofluids. The effects of nanolubricants on boiling and two phase flow phenomena are presented as well. Furthermore, studies of applications and challenges of refrigerant-based nanofluids are presented and future research needs are identified. For the limited studies done so far, there are some controversies from one study to another. Conclusions and contradictions on the available refrigerant-based studies of physical properties, boiling and two phase flow are presented. According to this review, it has been realized that the physical properties have significant effects on the refrigerant-based nanofluid boiling and two-phase flow characteristics but the lack of the accurate knowledge of these physical properties has greatly limited the study in this interdisciplinary field. Furthermore, the limited available experiments and quite contradictive results have limited the understanding of the fundamentals of boiling and two phase flow phenomena. flow regimes are very important in understanding the phenomena but less investigated so far. Apparently it is still a long way to go to achieve systematic fundamental knowledge and theory in the relevant subject. Therefore, effort should be made to contribute to the physical property database of nanofluids as a first priority. Secondly, systematic accurate experiments and flow regime observations on boiling and two-phase flow phenomena under a wide range of test conditions and nanofluid types should be emphasized to understand the fundamentals.
The synthesis and properties of metal chalcogenides have been extensively researched because of their useful and novel properties. Most of them have been synthesized by traditional high-temperature calcination methods...
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The synthesis and properties of metal chalcogenides have been extensively researched because of their useful and novel properties. Most of them have been synthesized by traditional high-temperature calcination methods. However, other preparation methods have also been investigated such as solvothermal synthesis method. Pruss et al synthesized layered Cu 2 WS 4 materials with square primitive lattices by using Cu(CH 3 CN) 4 BF 4 and [NH 4 ] 2 WS 4 with the solvothermal method in 1993. Later Crossland group reported the synthesis and characterization of this kind of copper tetrathiometallide materials. In this paper, a new synthesis method of Cu 2 MS 4 ( M = W or Mo) polycrystal was proposed. Cu 2 MS 4 ( M = W or Mo) materials were prepared under the different reaction conditions by hydrothermal synthesis method, the structure of which has been solved from powder X-ray diffraction data, and the scanning electron microscope photographs of which were taken using an JEOL JSM-6700. [NH 4 ] 2 WS 4 crystal and CuCl 2 were used as the raw materials to produce Cu 2 WS 4 crystal. The prepared Cu 2 WS 4 semiconductor crystallizes in space group I-42m with cell parameters a = b = 5.4454 (3) , c = 10.0671(7) . [NH 4 ] 2 MoS 4 crystal, CuCl and ammonia were used as the raw materials to prepare Cu 2 MoS 4 crystal. The Cu 2 MoS 4 material crystallizes in space group I-42m with cell parameters a = b = 5.4087(7) , c = 10.0428(2) . Cu 2 MS 4 ( M = W or Mo) polycrystal contains layers of edge-sharing MS 4 and CuS 4 tetrahedra separated by a van der Waals gap.
Cryogen spray cooling (CSC) can be used in laser dermatology to prevent burning injury of skin during *** uses a short spurt of (40 ~100 ms) on the skin surface before laser irradiation, leading to quick reduction in ...
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Cryogen spray cooling (CSC) can be used in laser dermatology to prevent burning injury of skin during *** uses a short spurt of (40 ~100 ms) on the skin surface before laser irradiation, leading to quick reduction in the skin *** this work, a systematic experimental study was presented to investigate the spray behavior of R134a.
Great quantities of experiments were performed to study the effects of two-phase spray cooling with high heat flux used R22 as refrigerant. A detailed research of the performance of spray cooling at different subcooli...
Great quantities of experiments were performed to study the effects of two-phase spray cooling with high heat flux used R22 as refrigerant. A detailed research of the performance of spray cooling at different subcooling temperature was conducted. The experimental results show that the critical heat flux can reach 272.04W⋅cm−2 with R22 as the working medium, and the corresponding surface temperature is 21.11°C These figures prove that the spray cooling has the advantages of high heat flux as well as lower surface temperature. With increasing overcooling degree of refrigerant at the entrance of nozzle, CHF rises at first and goes to stable then. Which means the CHF can be developed by adding the overcooling of refrigerant. However, the development is limited to a certain degree according to the characteristics of the system; namely, the overmuch increment plays a little role to improve CHF value.
In present work,the gas-solid two-phase flow in a flat-bottom multiple-spouted bed is simulated by the Eulerian-Eulerian *** kinetic theory of granular flow is used to close the equations,and the Johnson & Jac...
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In present work,the gas-solid two-phase flow in a flat-bottom multiple-spouted bed is simulated by the Eulerian-Eulerian *** kinetic theory of granular flow is used to close the equations,and the Johnson & Jackson boundary condition is defined for the solid phase at the wall.
The synthesis and properties of metal chalcogenides have been extensively researched because of their useful and novel *** of them have been synthesized by traditional high-temperature calcination ***, other preparati...
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The synthesis and properties of metal chalcogenides have been extensively researched because of their useful and novel *** of them have been synthesized by traditional high-temperature calcination ***, other preparation methods have also been investigated such as solvothermal synthesis method.
For the investigation on deflagration of oil/natural gas boiler and its prevention, an experimental system was designed and built to measure deflagration characteristics of combustible gas. The explosion limits of met...
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For the investigation on deflagration of oil/natural gas boiler and its prevention, an experimental system was designed and built to measure deflagration characteristics of combustible gas. The explosion limits of methane and its mixture of CO were measured at different temperature. The results matched the theoretical values well. It was also found that the range of explosion limit widens with an increase of initial temperature or a rise of CO rate, which indicates that incompletely burned methane causes high risk of deflagration. The possibility of deflagration, which may happen during purging, was numerically analyzed. Igniting without purging after flameout increases the possibility of deflagration. The result of unsteady numerical modeling on purging shows that ignition should be done rapidly within 5 minutes and purging is necessary before sparking again. The amount of purging air to ensure safety is 4 times of the furnace volume.
For high-efficiently solving the power dissipation problem of electronic components on the spacecraft, experiments were performed using micro-pin-finned structure as heater surface in subcooled nucleate pool boiling o...
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For high-efficiently solving the power dissipation problem of electronic components on the spacecraft, experiments were performed using micro-pin-finned structure as heater surface in subcooled nucleate pool boiling of FC-72 under microgravity condition utilizing the drop tower Beijing. Micro-pin-fins with the dimensions of 50 μm×120 μm (thickness × height) were fabricated on the surface of square silicon by using the dry etching technique. The micro-pin-finned silicon chip was heated by means of controlling heating voltage for the desired heat flux. At the same time, video of the bubble behavior was obtained by using high speed camera. The results showed that micro-pin-fins can increase the effective nucleate boiling sites number and the heat transfer performance efficiently, which stems from the sufficient supply of fresh liquid to the heater surface due to the capillary force independent of gravity. The steady nucleate pool boiling heat transfer on micro-pin-finned surface can be obtained at high heat fluxes and is greatly enhanced compared with smooth surface in microgravity.
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