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Ran Zhao

Bio: Ran Zhao is an academic researcher from Tsinghua University. The author has contributed to research in topics: Heat flux & Supercritical fluid. The author has an hindex of 4, co-authored 4 publications receiving 51 citations.

Papers
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Journal ArticleDOI
Junjie Yan1, Yinhai Zhu1, Ran Zhao1, Shuai Yan1, Pei-Xue Jiang1 
TL;DR: In this article, the authors investigated the flow and heat transfer instabilities in supercritical pressure n-decane, with pressure of 2.5 and 3.0 MPa and inlet temperature of 16-225°C.

39 citations

Journal ArticleDOI
TL;DR: In this article, the two-phase flow patterns of R32 flow boiling in horizontal mini channels were investigated and a new flow pattern map was established and it agrees 97.6% of the experimental data in the study.

20 citations

Journal ArticleDOI
TL;DR: In this article, the heat transfer coefficient and pressure drop of R32 flow boiling in horizontal mini channels were investigated, where the working conditions cover 1 and 2mm channel inner diameters, 10−20°C saturation temperatures, 50−600 kgm−m−2 ǫs−1 mass fluxes, 10 −30 kW −m−n−2 heat fluxes and 0 −1 vapor qualities.

13 citations

Journal ArticleDOI
TL;DR: In this paper, experimental studies are reported on coke deposition of n-decane and HF-II fuel in sintered bronze porous media at different pressures and a temperature ranging from 350 to 638 °C.
Abstract: Transpiration cooling technology is a feasible thermal protection method for hypersonic vehicles. To ensure the safety of transpiration cooling structures, the coke deposition rule of hydrocarbon fuels in porous media is a key problem that has to be considered. In this paper, experimental studies are reported on coke deposition of n-decane and HF-II fuel in sintered bronze porous media at different pressures and a temperature ranging from 350 to 638 °C. Results showed that the temperature was a dominant factor for coke generation from hydrocarbon fuels. Two types of coking behaviors, i.e., thermal-oxidative coking and pyrolysis coking, were observed, which resulted in the coke surface deposition rate exhibiting a double-peak curve. At a certain temperature, the mass flow rate determined the fluid residence time in porous channels. Thermal-oxidative coking was affected by the residence time and the dissolved oxygen concentration, so the coke surface deposition rate increased at first and then decreased wit...

12 citations

Journal ArticleDOI
TL;DR: In this paper , the effect of ECC jackets for enhancing the seismic performance of existing bridge columns was investigated in terms of mitigating damage, increasing load-carrying capacity, ductility and energy dissipation capacity.

5 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the authors investigate two-phase heat transfer of HFE-7100 in mini-channels and its cooling performance in order to determine its effectiveness for a fuel cell application.

43 citations

Journal ArticleDOI
TL;DR: In this paper, a novel structure of micro-channel heat sink with rhombus fractal-like units is proposed for improve the overall performance, and a geometry optimization approach is developed for the design of the new microchannel heat sinks.
Abstract: Microchannel heat sink is commonly used as a high-efficiency heat exchanger type in electronic microchips cooling, and the parallel microchannels arranged on the heat sink not only enhance heat transfer area but also result in large pumping power. In this paper, a novel structure of microchannel heat sink with rhombus fractal-like units is proposed for improve the overall performance, and a geometry optimization approach is developed for the design of the new microchannel heat sink. The validation of the geometry optimization approach is performed, and the results show that the predicted pumping power can describe 93% of the experimental data within the deviation limit of ± 5% and the mean deviation is 1.95%. Compared to the conventional parallel microchannel heat sink, the microchannel heat sink with rhombus fractal-like units may increase the COP by 7.9%-68.7% under the same constrains of external size, specified heat flux and maximum temperature limitation, which indicates the rhombus fractal-like units may effectively improve the efficiency of microchannel heat sinks.

39 citations

Journal ArticleDOI
TL;DR: In this paper, the authors focus on the flow boiling characteristics of pure R32 in a single horizontal stainless steel tube with an internal diameter of 6.0mm and a total of 437 experimental results are presented for two-phase heat transfer coefficient and frictional pressure drop and the effect of the operating parameters in terms of mass flux, saturation temperature, and imposed heat flux.
Abstract: Refrigerant R32 is one option for the replacement of R410A in residential air conditioning and heat pump systems. This paper focus on the flow boiling characteristics of pure R32 in a single horizontal stainless steel tube with an internal diameter of 6.0 mm. A total of 437 experimental results are presented for two-phase heat transfer coefficient and frictional pressure drop and the effect of the operating parameters in terms of mass flux (from 146 to 507 kg/m2 s), saturation temperature (from 24.6 to 40.6 °C) and imposed heat flux (from 2.4 to 41.2 kW/m2) is discussed. Several heat transfer coefficient and pressure drop data of R410A obtained in the same test section are also used for comparison purposes. Finally, predictions of the most quoted flow boiling heat transfer and frictional pressure drop methods are compared to experimental data to evaluate their agreement.

30 citations

Journal ArticleDOI
TL;DR: In this article, a double-layer cooling channel was proposed to improve the active regenerative cooling performance of a scramjet using supercritical n-decane, and a new type of cooling channel, the double layer channel, was proposed based on reliable numerical simulations.

28 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of secondary flows and heat flux redistribution induced by buoyancy on supercritical-pressure heat transfer were analyzed, and it was shown that drastic variations of the fuel density with temperature at a supercritical pressure of 3 MPa induce strong buoyancy effect on heat transfer.

28 citations