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thermal performance of Mini Cooling Channels for High-Power Servo Motor with Non-Uniform Heat Dissipation

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Journal of thermal Science 2023年第2期32卷 650-661页

作者： WANG Tianhu GAO Zhigang BAI Junhua WANG Zhiqiang QIAO Keqiang LI Peng Institute of Precision Guidance and Control Northwestern Polytechnical UniversityXi'an 710072China College of Petroleum Engineering Xi'an Shiyou UniversityXi'an 710065China

High-power servo motor is widely employed as a necessary actuator in flight vehicles.The urgent problem to be solved restraining the working performance of servo motor is no longer the torque and power,but the heat dissipation capability under high-power working conditions,which may cause the overheat,even burn down of motor or other potential safety hazards.Therefore,a structure of mini cooling channels with appropriate channel density is designed in accordance with the non-uniform heat flux of servo motor in this paper.Combined with the regenerative cooling method,the cryogenic fuel supercritical methane is served as the coolant,which is easy to be obtained from the propulsion system,and the heat from the servo motor can be transported to the combustion for reusing.According to the actual working cases of servo motor,a numerical model is built to predict the thermal performance of cooling channels.In order to better represent the secondary flow of coolant in the cooling channels,especially the turbulent mixed flow in the manifold,the k-εRNG model with enhanced wall treatment is employed resulting from its precise capacity to simulate the secondary and wall shear flow.On this basis,the heat transfer mechanism and thermal performance of cooling channels,as well as the influence of various heat flux ratios are investigated,which can offer an in-depth understanding of restraining excessive temperature rise and non-uniformity distribution of the servo motor.By the calculation results,it can be concluded that under the adjustment of the channel density according to the corresponding heat flux,the positive role of the appropriate channel density and the manifolds on heat transfer is manifested.Moreover,the maximum temperature difference of heating wall can be kept within an acceptable range of the servo motor.The heat transfer coefficient in the manifold is nearly 2–4 times higher compared with that in the straight cooling channels.The effect of buoyancy force cannot be neglected even in the manifold with turbulent mi

关键词： servo motor mini cooling channel non-uniform heat flux heat dissipation supercritical methane thermal performance

Numerical analysis on phase change progress and thermal performance of different roofs integrated with phase change material(PCM)in Moroccan semi-arid and Mediterranean climates

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Building Simulation 2023年第1期16卷 69-85页

作者： Yanqiu Huang Shan Yang Moussa Aadmi Yi Wang Mustapha Karkri Zhenhao Zhang State Key Laboratory of Green Building in Western China Xi'an University of Architecture and TechnologyNo.13 Yanta RD.Xi'an 710055China School of Building Services Science and Engineering Xi'an University of Architecture and TechnologyNo.13 Yanta RD.Xi'an 710055China LMASI ElectromagnetismPhysics of Plasmas and ApplicationsPolydisciplinary Faculty of NadorMohammed First UniversityB.P 30062700SelouaneNadorMorocco CERTES Univ Paris Est Creteil61 Avenue du Général de GaulleF-94010 CreteilFrance

Phase change material(PCM)applied to roofs can weak external heat entering the room to reduce air-conditioning energy consumption.In this study,three forms of macro-encapsulated PCM roofs with different PCMs(RT27,RT31,RT35HC,PT37)are proposed.The effects of PCM thickness,the encapsulation forms,and different PCMs on the thermal performance of the roof are discussed in Moroccan semi-arid and Mediterranean climates.The results show that as the PCM thickness increases,the peak temperature attenuation of the roof inner surface decreases.In two climates,the pure PCM layer among the three encapsulation forms(i.***.pure PCM layer,PCM in aluminum tubes,PCM in triangular aluminum)is the easiest to appear the phenomenon of insufficient heat storage and release,while the reduction of the peak inner surface temperature and time lag is the most satisfying.For the PCM in the aluminum tube,phase change time is the shortest and the latent heat utilization ratio is the highest,while thermal regulation performance is the least satisfying.The PCM in triangular aluminum can improve the latent heat utilization ratio significantly,and its thermal regulation performance is in the middle.In semi-arid climate,the time lag increases with phase change temperature increasing.The time lag could reach up to 6 h with 37℃phase transition temperature.In Mediterranean climate,the longest time lag with RT31 is 5 h,while the lowest peak inner surface temperature appears with RT27.The obtained conclusions could provide guidance for the application of PCM roofs in these two climates.

关键词： numerical simulation PCM roof thermal performance inner surface temperature time lag

Evaluation of the thermal performance of radiant floor heating system with the influence of unevenly distributed solar radiation based on the theory of discretization

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Building Simulation 2023年第1期16卷 105-120页

作者： Jiacheng Zheng Tao Yu Bo Lei Xiujing Luo School of Mechanical Engineering Southwest Jiaotong UniversityChengdu 610031China

In the building with many transparent envelopes,solar radiation can irradiate on the local surface of floor and cause overheating.The local thermal comfort in the room will be dissatisfactory and the thermal performance of radiant floor will be strongly affected.However,in many current calculation models,solar radiation on the floor surface is assumed to be uniformly distributed,resulting in the inaccurate evaluation of the thermal performance of the radiant floor.In this paper,a calculation model based on the theory of discretization and the RC thermal network is proposed to calculate the dynamic thermal performance of radiant floor with the consideration of unevenly distributed solar radiation.Then,the discretization model is experimentally validated and is used to simulate a radiant floor heating system of an office room in Lhasa.It is found that with the unevenly distributed solar radiation,the maximum surface temperature near the south exterior window can reach up to 35.6℃,which exceeds the comfort temperature limit and is nearly 8.5℃higher than that in the north zone.Meanwhile,the heating capacity of the radiant floor in the irradiated zone can reach up to 171 W/m^(2),while that in the shaded zone is only 79 W/m^(2).The model with the assumption of uniformly distributed solar radiation ignores the differences between the south and north zones and fails to describe local overheating in the irradiated zones.By contrast,the discretization model can more accurately evaluate the thermal performance of radiant floor with the influence of real solar radiation.Based on this discretization model,novel design and control schemes of radiant floor heating system can be proposed to alleviate local overheating and reduce heating capacity in the irradiated zone.

关键词： radiant floor heating solar radiation simplified model thermal performance

Experimental Research on thermal performance of Ultra-Thin Flattened Heat Pipes

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Journal of thermal Science 2022年第6期31卷 2346-2362页

作者： TANG Yongle CAO Jianguang WANG Shuangfeng Key Lab of Heat Transfer Enhancement and Energy Conservation of Ministry of Education School of Chemistry and Chemical EngineeringSouth China University of TechnologyGuangzhou 510640China Shanghai Institute of Satellite Engineering Shanghai 200240China

Ultra-thin flattened heat pipe(UTHP) is an effective solution to solve the problem of high-power density heat dissipation in narrow space. The key factors that determine its thermal performance include: the shapes and sizes of the UTHP, the wick structure, the type of working fluid and its filling ratio. The change in the filling ratio means not only a change in the amount of the working fluid, but also a change in the space distribution of the gas and liquid phases inside the heat pipe. Therefore, it is important to explore the effect of liquid filling ratio on the thermal performance of UTHP. It can provide effective guidance for the production of UTHP. In this work, experiments were conducted on four groups of UTHPs with different mesh wicks under a series of liquid filling ratios. The results demonstrate that the volume of the filling working fluid should account for 22%-37% of the total internal volume of the UTHP to avoid deterioration of heat transfer during the operation of the UTHP. In addition, a prediction model of the evaporator temperature has been established to provide guidance for the application of UTHPs.

关键词： ultra-thin flattened heat pipe liquid filling ratio gas-liquid phase space distribution thermal performance prediction model

Wall-Attached Night Ventilation Combined with Phase Change Material Wallboard in Hot Summer:An Experimental Study on the thermal performance

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Journal of thermal Science 2022年第2期31卷 318-331页

作者： JI Wenhui YUAN Yanping LI Yajun YU Min School of Mechanical Engineering Southwest Jiaotong UniversityChengdu 610031China

Night ventilation is regarded as a promising cooling strategy by storing night cooling in the thermal mass of the building.However,night ventilation performance in hot summer is restricted by the climatic limits.In this paper,we propose a new solution as the integration of wall-attached night ventilation(WANV)and phase change material wallboard(PCMW).The principle of the proposed system is to utilize the wall-attached jet ventilation to achieve forced convection and to adopt latent energy storage of PCMW to enlarge the energy storage density capabilities,and the coupling method is expected to improve the night ventilation performance.Comparative experiments were conducted to evaluate the thermal performance of the hybrid system by evaluating indoor temperature history,thermal comfort time and cooling efficiency.Due to the high thermal energy storage density capability of PCMW,it was found that the presence of PCMW has a negative influence on night cooling efficiency but still has a positive influence on the overall cooling effect.The proposed WANV combined with the PCMW system significantly increased the temperature decrease of room air and west wall inside surface during one hour's night ventilation by 94.97%and 67.74%,respectively,and reached an extension of 38.42%of indoor thermal comfort time.The results highlight the potential of WANV integration of PCMW to improve the thermal performance of night ventilation.

关键词： night ventilation wall-attached jet ventilation phase change material wallboard thermal performance

Analysis of the thermal performance of External Insulation in Prefabricated Buildings Using Computational Fluid Dynamics

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Fluid Dynamics & Materials Processing 2022年第5期18卷 1293-1306页

作者： Ang Wang Hui Wang Huanghe Science and Technology College Zhengzhou450000China Group LLC of Henan Province The First Construction WorkZhengzhou450000China

This paper investigates the thermal performance of prefabricated exterior walls using the Computational Fluid Dynamics method to reduce energy consumption.The thermal performance of the prefabricated exterior wall was numerically simulated using the software ANSYS Fluent.The composite wall containing the cavity is taken as the research object in this paper after analysis.The simulation suggests that when the cavity thickness is 20 mm and 30 mm,the heat transfer coefficient of the air-sandwich wall is 1.3 and 1.29,respectively.Therefore,the optimal width of the cavity is 20 mm,and the most suitable material is the aerated concrete block.In addition,a comparative analysis is conducted on the cavity temperature in the wall under different conditions.It is proven that an intelligent environment control system can significantly improve thermal efficiency and provide a solid theoretical basis for further research in the external insulation of prefabricated buildings.

关键词： Fluid mechanics prefabricated building FLUENT software architectural cavity thermal performance

performance evaluation of new epoxy resin-based composite phase change materials and their asphalt mixture

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Journal of Traffic and Transportation Engineering(English Edition) 2024年第3期11卷 507-522页

作者： Yuchao Gao Jiao Jin Shuai Liu Yinfei Du Guoping Qian Jie Mao Yongqiang Zhu School of Traffic and Transportation Engineering Changsha University of Science and Technology School of Civil Engineering Central South University Guangdong Guanyue Highway and Bridge Co. Ltd.

In recent years, the temperature-adjusted asphalt pavement has been an extensive concern by scholars in various countries, and this pavement can reduce temperaturerelated diseases. In this study, the shaped composite phase change materials(CPCMs) were successfully synthesized by two processes, which are vacuum impregnation and epoxy curing. Firstly, the applicability of CPCMs in asphalt mixtures was evaluated by microscopic characterization, chemical compatibility, thermal properties, durability, and leakage stability. Secondly, CPCMs were applied to the asphalt mixture to evaluate its temperatureadjusted characteristics and pavement performance. Finally, the performance of the temperature-adjusted asphalt mixture was analyzed by integrating all factors. The research shows that the prepared CPCMs have excellent thermal properties and durability,the phase transition temperature is 48.93°C, and the phase transition enthalpy is 106.5 J/g,which fully meets the requirements for use in pavement. The temperature-adjusted asphalt mixture could alleviate the occurrence of extreme temperature, which was 4.9°C lower than the conventional mixture. The pavement performance of the temperatureadjusted asphalt mixture can meet the specified standards for humid areas. Considering the factors, the recommended amount of CPCMs is 1.5%. The research results provide a basis for the promotion of temperature-adjusted asphalt pavement and effectively support the development of pavement engineering technology.

关键词： Pavement engineering Temperature-adjusted asphalt mixture Phase change materials thermal performance

Analysis of the thermal performance of the novel assembled Chinese solar greenhouse with a modular soil wall in winter of Yinchuan,China

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International Journal of Agricultural and Biological Engineering 2022年第5期15卷 70-77页

作者： Yanfei Cao Hongjun Xu Miao Shi Xueyan Zhang Yahong Zhang Zhirong Zou College of Horticulture Northwest A&F UniversityYangling 712100ShaanxiChina Key Laboratory of Protected Horticulture Engineering in Northwest Ministry of Agriculture and Rural AffairsYangling 712100ShaanxiChina College of Horticulture Xinjiang Agricultural UniversityUrumqi 830052China School of Agriculture Ningxia UniversityYinchuan 750021China

In order to improve the thermal insulation and storage performance of Chinese solar greenhouses in winter,a novel assembled Chinese solar greenhouse(ACSG)without energy supplement in cold climatic areas was designed to evaluate and compare its thermal performance with that of conventional Chinese solar greenhouse(CSG).The thermal properties of both greenhouses were tested in field on cold winter days in Ningxia,China.The results indicated that the land utilization rate of ACSG was 19.3%higher than that of CSG.On a typical sunny day(the lowest outdoor temperature was−22.0℃)and typical cloudy day(the lowest outdoor temperature was−19.7℃)during the experiment,the minimum indoor temperature of ACSG was respectively 1.7℃and 2.0℃higher than that of CSG.The results for 24 consecutive days(the average outdoor daily minimum air temperature was−19.0℃)showed that the average minimum indoor temperature of ACSG was 1.4℃higher than that of CSG(p<0.05).The modular soil wall attached with colored steel polystyrene boards would be exploited as the north wall of CSG in Yinchuan area.

关键词： thermal performance solar greenhouse north wall composite wall structure soil block

thermal performance of a Micro Heat Pipe Array for Battery thermal Management Under Special Vehicle-Operating Conditions

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Automotive Innovation 2020年第4期3卷 317-327页

作者： Chengning Yao Dan Dan Yangjun Zhang Yueqi Wang Yuping Qian Yuying Yan Weilin Zhuge State Key Laboratory of Automotive Safety and Energy Tsinghua UniversityBeijing 100084China Fluids and thermal Engineering Research Group Faculty of EngineeringUniversity of NottinghamNottingham NG72RDUK

The thermal management of battery systems is critical for maintaining the energy storage capacity,life span,and thermal safety of batteries used in electric vehicles,because the operating temperature is a key factor affecting battery performance.Excessive temperature rises and large temperature differences accelerate the degradation rate of such batteries.Currently,the increasing demand for fast charging and special on-vehicle scenarios has increased the heat dissipation requirements of battery thermal management systems.To address this demand,this work proposes a novel micro heat pipe array(MHPA)for thermal management under a broadened research scope,including high heat generation rates,large tilt angles,mild vibration,and distributed heat generation conditions.The experimental results indicate that the temperature difference is maintained 3.44°C at a large heat generation of 50 W for a limited range of tilt angles.Furthermore,a mild vehicle vibra-tion condition was found to improve temperature uniformity by 3.3°C at a heat generation of 10 W.However,the use of distributed heat sources results in a temperature variation of 3.88°C,suggesting that the heat generation distribution needs to be considered in thermal analyses.Understanding the effects of these special battery-operating conditions on the MHPA could significantly contribute to the enhancement of heat transfer capability and temperature uniformity improvement of battery thermal management systems based on heat pipe technologies.This would facilitate the realization of meeting the higher requirements of future battery systems.

关键词： Battery thermal management thermal performance Micro heat pipe array Operating conditions