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High-Speed Visualization of Bubble Behaviors for Pool Boiling of R-141b

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Journal of Thermal Science 2006年第1期15卷 79-84,96页

作者： Yanhua DIAO yaohua zhao Qiuliang WANG Institute of Electrical Engineering Chinese Academy of Sciences Beijing 100080 China The College of Architecture and Civil Engineering Beijing University of Technology Beijing 100022 China

A visualization study on the behavior of bubbles has been carried out for pool boiling of R141b on a horizontal transparent heater at pressure 0.1 MPa. The behaviors of bubbles were recorded by a high-speed camera placed beneath the heater surface. The departure diameter, departure time of bubbles and nucleation site density at different heat flux were obtained. The visualization results show that bubble departure diameter and departure time decrease, while the nucleation site density increases as the heat flux increases. R is also observed that there is no liquid recruited into the microlayer in the experiment. Based on the experimental results, boiling curve for R141b was predicted by using the dynamic microlayer model. As a resuR, the agreement between the predictive result based on the dynamic microlayer model and the experiment data for boiling curve of R141b is good at high heat flux.

关键词： R141b heat transfer bubble dynamics pool boiling.

Experimental investigations on the heat transfer characteristics of micro heat pipe array applied to flat plate solar collector

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Science China(Technological Sciences) 2013年第5期56卷 1177-1185页

作者： DENG YueChao QUAN ZhenHua zhao yaohua WANG LinCheng Department of Building Environment and Facility Engineering College of Architecture and Civil EngineeringBeijing University of Technology

This paper introduces a novel fiat plate solar collector （FPC） using micro heat pipe array （MHPA） as a key element. To analyze the thermal transfer behavior of flat plate solar collector with micro heat pipe array （MHPA-FPC）, an indoor experiment for thermal transfer characteristic of MHPA applied to FPC was conducted by using an electrical heating film to simulate the solar radiation. Different cooling water flow rates, cooling water temperatures, slopes, and contact thermal resistances be- tween the condenser of MHPA and the heat exchanger were tested at different heating powers. The experimental results in- dicate that MHPA-FPC exhibits the enhanced heat transfer capability with increased cooling water flow rate and temperature. Total thermal resistance has a maximum decline of approximately 10% when the flow rate increases from 180 to 360 L h-1 and 38% when the cooling water temperature increases from 20~C to 40~C. When the inclination angle of MHPA-FPC ex- ceeds 30~, the slope change has a negligible effect on the heat transfer performance of MHPA-FPC. In addition, contact thermal resistance significantly affects the heat transfer capability of MHPA-FPC. The total thermal resistances lowers to nearly half of the original level when contact material between the condenser of MHPA and the heat exchanger changes from conductive silicone to conductive grease. These results could provide useful information for the optimal design and operation of MHPA-FPC.

关键词： micro heat pipe array novel fiat plate solar collector heat transfer characteristic cooling water flow rate cooling watertemperature slope contact thermal resistance

Experimental study on the new type of electrical storage heater based on flat micro-heat pipe arrays

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Science China(Technological Sciences) 2018年第2期61卷 219-231页

作者： wang zeyu diao yanhua zhao yaohua liang lin wang tengyue beijing key laboratory of green built environment and efficient technology beijing university of technologyBeijing 100124China beijing advanced innovation center for future internet technology Beijing 100124China

A new type of electrical storage heater that utilizes latent heat storage and flat micro-heat pipe arrays （FMHPAs） was developed. The thermal characteristics of the heater were tested through experimentation. The structure and operating principle of the storage heater were expounded. Three rows of FMHPAs were applied （three rows with five assemblies each） with a mass of 28 kg of phase change material （PCM） in the heat storage tank. Electric power was supplied to the PCM in the range of 0.2-2.04 kW, and air was used as heat transfer fluid, with the volume flow rate ranging from 40-120 m3/h. The inlet temperature was in the range of 15-24~C. The effects of heating power, air volume flow rate, and inlet temperature were investigated. The electrical storage heater exhibited efficiencies of 97% and 87% with 1.98 and 1.30 kW of power during charging and discharging, respectively. Application of the proposed storage heater can transfer electricity from peak periods to off-peak periods, and the excess energy generated by wind farms can be stored as heat and released when needed. Good economic and environmental benefits can be obtained.

关键词： flat micro-heat pipe latent heat storage electrical storage heater peak load shifting wind power utilization

Performance simulation and optimization of new radiant floor heating based on micro heat pipe array

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Building Simulation 2022年第7期15卷 1295-1308页

作者： Heran Jing Zhenhua Quan Ruixue Dong Limin Hao Yunhan Liu yaohua zhao Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology Beijing University of TechnologyBeijing 100124China

This paper proposes two new radiant floor heating structures based on micro heat pipe array(MHPA),namely cement-tile floor and keel-wood *** numerical models for these different floor structures are established and verified by *** temperature distribution and heat transfer process of each part are comprehensively obtained,and the structure is *** results show that the cement-tile floor has the better heat transfer performance of the *** under the same inlet water temperature and flow rate,the keel-wood floor's surface temperature distribution is about 2℃ lower than that of the cement-tile *** inlet water temperature of cement-tile floor is about 10℃ lower than that of keel-wood structure when the floor surface temperature is the *** a longitudinal heat transfer above MHPA,the floor surface temperature decreases by 0.5℃ for every 10 mm filling layer *** order to reduce the non-uniformity of the floor's surface temperature and improve the thermal comfort of the heated room,the optimal structure for a floor is given,with the maximum surface temperature difference reduced by 3.35℃.We used research focusing on new radiant floor heating,with advantages including high efficiency heat transfer,low water supply temperature,simple waterway structure,low resistance and leakage risk,to provide theory and data to support the application of an effective radiant floor heating based on MHPA.

关键词： radiant floor heating micro heat pipe array numerical simulation heat transfer

MAXIMUM SCORE CHANGE-POINT ESTIMATION IN BINARY RESPONSE MODEL

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Journal of Systems Science & Complexity 2006年第3期19卷 386-392页

作者： Lincheng zhao ~ Chaofeng KOU yaohua WU Department of Statistics and Finance University of Science and Technology of China Hefei 230026 China.

This paper is concerned with the estimation of change-point in a binary response model with the assumption that the conditional median of the error term, given the explanatory variable, is zero. We construct an estimation of change-point based on the maximum score function and give its exponential convergence rate under some mild conditions.

关键词： Binary response model change-point maximum score estimation.

Cold Storage Capacity for Solar Air-Conditioning in Office Buildings in Different Climates

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Journal of Thermal Science 2019年第6期28卷 1195-1204页

作者： SUN Zhifeng zhao yaohua XU Wei WANG Dongxu LI Huiyong ZHANG Xinyu LI Huai LI Yang College of Architecture and Civil Engineering Beijing University of TechnologyBeijing 100124China Institute of Building Environment and Energy China Academy of Building ResearchBeijing 100013China School of Civil and Resources Engineering University of Science and Technology BeijingBeijing 100083China Second Design Institute Beijing Institute of Architectural DesignBeijing 100045China

The building sector accounts for more than 40% of the global energy consumption. This consumption may be lowered by reducing building energy requirements and using renewable energy in building energy supply systems. Solar air-conditioning systems(SACS) are a promising solution for the reduction of conventional energy in buildings. The storage, especially the cold storage, plays an important role in SACS for unstable solar irradiation. In this paper, we took the absorption refrigerating unit as an example, and the solar air-conditioning system of an office building in Beijing was simulated. The accuracy of this model was verified by comparing with the SACS operation data. Moreover, based on the simulation data, the cold storage capacity of the solar air-conditioning system in different climatic regions was studied. The cold storage capacities of SACS in 20 cities distributed in different climate regions were studied systematically. The results simulated by our proposed model will be beneficial to the SACS design, and will enlarge the application of SACS.

关键词： office building solar air-conditioning system cold storage capacity TRNSYS

Experimental Investigation of Solar Panel Cooling by a Novel Micro Heat Pipe Array

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Energy and Power Engineering 2010年第3期2卷 171-174页

作者： Xiao Tang Zhenhua Quan yaohua zhao 不详

A novel micro heat pipe array was used in solar panel cooling. Both of air-cooling and water-cooling conditions under nature convection condition were investigated in this paper. Compared with the ordinary solar panel, the maximum difference of the photoelectric conversion efficiency is 2.6%, the temperature reduces maximally by 4.7℃, the output power increases maximally by 8.4% for the solar panel with heat pipe using air-cooling, when the daily radiation value is 26.3 MJ. Compared with the solar panel with heat pipe using air-cooling, the maximum difference of the photoelectric conversion efficiency is 3%, the temperature reduces maximally by 8℃, the output power increases maximally by 13.9% for the solar panel with heat pipe using water-cooling, when the daily radiation value is 21.9 MJ.

关键词： Solar Panel Cooling Photoelectric Conversion Efficiency Micro Heat Pipe array

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平板微热管阵列垂直传热的数值分析

化工学报 2014年第2期65卷 508-515页

作者：王宏燕赵耀华北京工业大学建筑工程学院北京100022

对新型高效传热元件平板微热管阵列(MHPA)的工作机理进行了理论研究。通过建立分区微元模型对热管冷凝段内部工质的流动与传热过程进行了分析。确定了微槽内冷凝液膜的厚度,温度场分布及质量流量等物理参数。利用Matlab软件编写的程序... 详细信息

对新型高效传热元件平板微热管阵列(MHPA)的工作机理进行了理论研究。通过建立分区微元模型对热管冷凝段内部工质的流动与传热过程进行了分析。确定了微槽内冷凝液膜的厚度,温度场分布及质量流量等物理参数。利用Matlab软件编写的程序计算结果与实验值吻合较好,最大误差在5%以内。根据软件计算的结果,拟合得到了冷凝段内部饱和温度的表达式。

关键词：微热管凝结传热数值分析

DISTRIBUTION FREE LAWS OF THEITERATED LOGARITHM FOR KERNELESTIMATOR OF REGRESSION FUNCTIONBASED ON DIRECTIONAL DATADISTRIBUTION FREE LAWS OF THEITERATED LOGARITHM FOR KERNELESTIMATOR OF REGRESSION FUNCTIONBASED ON DIRECTIONAL DATA

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Chinese Annals of Mathematics,Series B 2000年第4期21卷 489-498页

作者： WANGXIAOMING zhaoLINCHENG WUyaohua Departmentofstatistics ShanghaiUniversityofFinanceandEconomicsShanghai200433China. DepartmentofstatisticsandFinance UniversityofScienceandTechnologyofChinaHefei230026China.

The authors derive laws of the iterated logarithm for kernel estimator of regression function based on directional data. The results are distribution free in the sense that they are true for all distributions of desig... 详细信息

关键词： Directional data Laws of the iterated logrithm Regression function kernel estimator Strong convergence rates