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Thermal performance of a single-layer packed metal pebble-bed exposed to high energy fluxes

Shengchun ZHANG, Zhifeng WANG, Hui BIAN, Pingrui HUANG

《能源前沿(英文)》 2021年 第15卷 第2期   页码 513-528 doi: 10.1007/s11708-019-0638-7

摘要: It is difficult to accurately measure the temperature of the falling particle receiver since thermocouples may directly be exposed to the solar flux. This study analyzes the thermal performance of a packed bed receiver using large metal spheres to minimize the measurement error of particle temperature with the sphere temperature reaching more than 700°C in experiments in a solar furnace and a solar simulator. The numerical models of a single sphere and multiple spheres are verified by the experiments. The multiple spheres model includes calculations of the external incidence, view factors, and heat transfer. The effects of parameters on the temperature variations of the spheres, the transient thermal efficiency, and the temperature uniformity are investigated, such as the ambient temperature, particle thermal conductivity, energy flux, sphere diameter, and sphere emissivity. When the convection is not considered, the results show that the sphere emissivity has a significant influence on the transient thermal efficiency and that the temperature uniformity is strongly affected by the energy flux, sphere diameter, and sphere emissivity. As the emissivity increases from 0.5 to 0.9, the transient thermal efficiency and the average temperature variance increase from 53.5% to 75.7% and from 14.3% to 27.1% at 3.9 min, respectively. The average temperature variance decreases from 29.7% to 9.3% at 2.2 min with the sphere diameter increasing from 28.57 mm to 50 mm. As the dimensionless energy flux increases from 0.8 to 1.2, the average temperature variance increases from 13.4% to 26.6% at 3.4 min.

关键词: packed bed     solar thermal power plants     high heat fluxes     radiative heat transfer    

Heat transfer characteristics of high heat flux vapor chamber

Dongchuan MO, Shushen LU, Haoliang ZHENG, Chite CHIN,

《能源前沿(英文)》 2010年 第4卷 第2期   页码 166-170 doi: 10.1007/s11708-009-0076-z

摘要: To meet the challenge of heat spreading in electronic products, highly efficient high heat flux heat transfer vapor chambers have been manufactured and their heat transfer characteristics have been studied by a fast test system. A solid copper block with the same shape as the vapor chamber is used to compare the performance of the vapor chamber. The result shows that, it will take about 5min to achieve a steady state in the fast test system. The heat transfer characteristics of the vapor chamber are more superior to those of the copper block. In this paper, total thermal resistance of the test system is used to evaluate the heat transfer characteristics of the vapor chamber, because it has already been used to consider both the spreading thermal resistance and the flatness of the vapor chamber.

关键词: high heat flux     vapor chamber (VC)     heat transfer characteristics     fast test    

Numerical study of a hybrid absorption-compression high temperature heat pump for industrial waste heat

Zhiwei MA, Huashan BAO, Anthony Paul ROSKILLY

《能源前沿(英文)》 2017年 第11卷 第4期   页码 503-509 doi: 10.1007/s11708-017-0515-1

摘要: The present paper aims at exploring a hybrid absorption-compression heat pump (HAC-HP) to upgrade and recover the industrial waste heat in the temperature range of 60°C–120°C. The new HAC-HP system proposed has a condenser, an evaporator, and one more solution pump, compared to the conventional HAC-HP system, to allow flexible utilization of energy sources of electricity and waste heat. In the system proposed, the pressure of ammonia-water vapor desorbed in the generator can be elevated by two routes; one is via the compression of compressor while the other is via the condenser, the solution pump, and the evaporator. The results show that more ammonia-water vapor flowing through the compressor leads to a substantial higher energy efficiency due to the higher quality of electricity, however, only a slight change on the system exergy efficiency is noticed. The temperature lift increases with the increasing system recirculation flow ratio, however, the system energy and exergy efficiencies drop towards zero. The suitable operation ranges of HAC-HP are recommended for the waste heat at 60°C, 80°C, 100°C, and 120°C. The recirculation flow ratio should be lower than 9, 6, 5, and 4 respectively for these waste heat, while the temperature lifts are in the range of 9.8°C–27.7 °C, 14.9°C–44.1 °C, 24.4°C–64.1°C, and 40.7°C–85.7°C, respectively, and the system energy efficiency are 0.35–0.93, 0.32–0.90, 0.25–0.85, and 0.14–0.76.

关键词: absorption compression     high temperature heat pump     efficiency     industrial waste heat     thermodynamic analysis    

Experimental investigation of liquid metal alloy based mini-channel heat exchanger for high power electronic

Manli LUO, Jing LIU

《能源前沿(英文)》 2013年 第7卷 第4期   页码 479-486 doi: 10.1007/s11708-013-0277-3

摘要: There is currently a growing demand for developing efficient techniques for cooling integrated electronic devices with ever increasing heat generation power. To better tackle the high-density heat dissipation difficulty within the limited space, this paper is dedicated to clarify the heat transfer behaviors of the liquid metal flowing in mini-channel exchangers with different geometric configurations. A series of comparative experiments using liquid metal alloy Ga68%In20%Sn12% as coolant were conducted under prescribed mass flow rates in three kinds of heat exchangers with varied geometric sizes. Meanwhile, numerical simulations for the heat exchangers under the same working conditions were also performed which well interpreted the experimental measurements. The simulated heat sources were all cooled down by these three heat dissipation apparatuses and the exchanger with the smallest channel width was found to have the largest mean heat transfer coefficient at all conditions due to its much larger heat transfer area. Further, the present work has also developed a correlation equation for characterizing the Nusselt number depending on Peclet number, which is applicable to the low Peclet number case with constant heat flux in the hydrodynamically developed and thermally developing region in the rectangular channel. This study is expected to provide valuable reference for designing future liquid metal based mini-channel heat exchanger.

关键词: heat exchanger     liquid metal     mini-channel     heat dissipation     heat transfer coefficient    

Impact of anthropogenic heat emissions on meteorological parameters and air quality in Beijing usinga high-resolution model simulation

《环境科学与工程前沿(英文)》 2022年 第16卷 第4期 doi: 10.1007/s11783-021-1478-3

摘要:

The Large scale Urban Consumption of energ Y model was updated and coupled with WRF.

关键词: Anthropogenic heat emissions     LUCY     High-resolution     Meteorological parameters     Air quality    

High heat flux thermal management through liquid metal driven with electromagnetic induction pump

《能源前沿(英文)》 2022年 第16卷 第3期   页码 460-470 doi: 10.1007/s11708-022-0825-9

摘要: In this paper, a novel liquid metal-based minichannel heat dissipation method was developed for cooling electric devices with high heat flux. A high-performance electromagnetic induction pump driven by rotating permanent magnets is designed to achieve a pressure head of 160 kPa and a flow rate of 3.24 L/min, which could enable the liquid metal to remove the waste heat quickly. The liquid metal-based minichannel thermal management system was established and tested experimentally to investigate the pumping capacity and cooling performance. The results show that the liquid metal cooling system can dissipate heat flux up to 242 W/cm2 with keeping the temperature rise of the heat source below 50°C. It could remarkably enhance the cooling performance by increasing the rotating speed of permanent magnets. Moreover, thermal contact resistance has a critical importance for the heat dissipation capacity. The liquid metal thermal grease is introduced to efficiently reduce the thermal contact resistance (a decrease of about 7.77 × 10−3 °C/W). This paper provides a powerful cooling strategy for thermal management of electric devices with large heat power and high heat flux.

关键词: high heat flux     liquid metal     electromagnetic pump     minichannel heat sink     thermal interface material    

Creep of brazed plate-fin structures in high temperature compact heat exchangers

Shantung TU, Guoyan ZHOU

《机械工程前沿(英文)》 2009年 第4卷 第4期   页码 355-362 doi: 10.1007/s11465-009-0065-2

摘要: In recent years, the need for high temperature heat exchangers to improve the efficiency of power and chemical conversion systems has been growing. However, the creep design of the high temperature compact heat exchangers has been a primary concern because the working temperature can be well above the creep limit of the materials. To establish the high temperature design criterion for compact heat exchangers, creep behavior of the plate-fin structures and brazed joints are investigated in this paper. The time-dependent deformation and bending stress of the plate-fin structures are obtained analytically by simplifying the fins to elastic springs. The creep damage evolution inside the brazed joint is studied by coupling the finite element method with a damage constitutive equation. The significant effect of creep property mismatch in the brazed joint on the creep strength is demonstrated.

关键词: compact heat exchanger     creep     damage     brazing joint    

Exergy analysis of R1234ze(Z) as high temperature heat pump working fluid with multi-stage compression

Bin HU, Di WU, L.W. WANG, R.Z. WANG

《能源前沿(英文)》 2017年 第11卷 第4期   页码 493-502 doi: 10.1007/s11708-017-0510-6

摘要: In this paper, the simulation approach and exergy analysis of multi-stage compression high temperature heat pump (HTHP) systems with R1234ze(Z) working fluid are conducted. Both the single-stage and multi-stage compression cycles are analyzed to compare the system performance with 120°C pressurized hot water supply based upon waste heat recovery. The exergy destruction ratios of each component for different stage compression systems are compared. The results show that the exergy loss ratios of the compressor are bigger than that of the evaporator and the condenser for the single-stage compression system. The multi-stage compression system has better energy and exergy efficiencies with the increase of compression stage number. Compared with the single-stage compression system, the coefficient of performance (COP) improvements of the two-stage and three-stage compression system are 9.1% and 14.6%, respectively. When the waste heat source temperature is 60°C, the exergy efficiencies increase about 6.9% and 11.8% for the two-stage and three-stage compression system respectively.

关键词: multi-stage compression     high temperature heat pump     heat recovery     exergy destruction     R1234ze(Z) working fluid    

Convective heat transfer in helical coils for constant-property and variable-property flows with high

Yufei MAO, Liejin GUO, Bofeng BAI, Ximin ZHANG

《能源前沿(英文)》 2010年 第4卷 第4期   页码 546-552 doi: 10.1007/s11708-010-0116-8

摘要: Forced convection heat transfer of single-phase water in helical coils was experimentally studied. The testing section was constructed from a stainless steel round tube with an inner diameter of 10 mm, coil diameter of 300 mm, and pitch of 50 mm. The experiments were conducted over a wide Reynolds number range of 40000 to 500000. Both constant-property flows at normal pressure and variable-property flows at supercritical pressure were investigated. The contribution of secondary flow in the helical coil to heat transfer was gradually suppressed with increasing Reynolds number. Hence, heat transfer coefficients of the helical tube were close to those of the straight tube under the same flow conditions when the Reynolds number is large enough. Based on the experimental data, heat transfer correlations for both incompressible flows and supercritical fluid flows through helical coils were proposed.

关键词: convective heat transfer     helical coils     high Reynolds number     supercritical pressure     variable property    

CONCENTRATIONS AND FLUXES OF DISSOLVED NUTRIENTS IN THE YANGTZE RIVER: LONG-TERM TRENDS AND ECOLOGICAL

《农业科学与工程前沿(英文)》 2021年 第8卷 第4期   页码 559-567 doi: 10.15302/J-FASE -2020344

摘要:

Intensifying human activity in the Yangtze River basin has substantially increased nutrient concentrations in the Yangtze River Estuary, leading to degradation of the coastal environment. Analysis of nutrient determinations published over the past 50 years reveals a gradual decreasing trend in the concentrations and fluxes of dissolved silicate (DSi). However, both dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphate (DIP) concentrations have increased significantly since the 1970s. The frequency of and area covered by red tide outbreaks have increased greatly during this period, mainly due to changes in nutrient supply ratios [i.e., N/P (DIN/DIP), N/Si (DIN/DSi), P/Si (DIP/DSi)]. A strong correlation was found between the riverine DIN fluxes and the estimated DIN inputs from the major N sources, particularly fertilizers and atmospheric deposition. The data provide a comprehensive assessment of nutrients in the Yangtze River basin and their ecological impacts and indicate a potentially significant influence of atmospheric deposition on DIN loadings and fluxes.

 

关键词: atmospheric deposition / ecological impacts / nitrogen sources / nutrients / Yangtze delta    

Cutting heat dissipation in high-speed machining of carbon steel based on the calorimetric method

QUAN Yanming, HE Zhenwei, DOU Yong

《机械工程前沿(英文)》 2008年 第3卷 第2期   页码 175-179 doi: 10.1007/s11465-008-0022-5

摘要: The cutting heat dissipation in chips, workpiece, tool and surroundings during the high-speed machining of carbon steel is quantitatively investigated based on the calorimetric method. Water is used as the medium to absorb the cutting heat; a self-designed container suitable for the high-speed lathe is used to collect the chips, and two other containers are adopted to absorb the cutting heat dissipated in the workpiece and tool, respectively. The temperature variations of the water, chips, workpiece, tool and surroundings during the closed high-speed machining are then measured. Thus, the cutting heat dissipated in each component of the cutting system, total cutting heat and heat flux are calculated. Moreover, the power resulting from the main cutting force is obtained according to the measured cutting force and predetermined cutting speed. The accuracy of cutting heat measurement by the calorimetric method is finally evaluated by comparing the total cutting heat flux with the power resulting from the main cutting force.

关键词: cutting system     medium     temperature     flux     tool    

Effective interventions on health effects of Chinese rural elderly under heat exposure

《环境科学与工程前沿(英文)》 2022年 第16卷 第5期 doi: 10.1007/s11783-022-1545-4

摘要:

● Education and subsidy were effective interventions during short-term heat exposure.

关键词: High temperature     Health effect     Comprehensive evaluation     Intervention     Rural elderly    

Interfacial heat transfer coefficient between metal and die during high pressure die casting process

GUO Zhipeng, XIONG Shoumei, CHO SangHyun, CHOI JeongKil

《机械工程前沿(英文)》 2007年 第2卷 第3期   页码 283-287 doi: 10.1007/s11465-007-0049-z

摘要: The present work focused on the determination of the interfacial heat transfer coefficient (IHTC) between metal and die during the high pressure die casting (HPDC) process. Experiments were carried out on an aluminum alloy, ADC12Z, using step shape casting so-called because of its shape. The IHTC was successfully determined by solving one of the inverse heat problems using the nonlinear estimation method first used by Beck. The calculation results indicated that the IHTC immediately increased after liquid metal was brought into the cavity by the plunger and decreased as the solidification process of the liquid metal proceeded. The liquid metal eventually solidified completely, a condition when the IHTC tended to be stable. Casting thickness played an important role in affecting the IHTC between the metal and die not only in terms of its value but also in terms of its change tendency. Also, under the test conditions, different change tendencies of the metal solid fraction were found between castings with different thicknesses and the die.

关键词: so-called     calculation     inverse     interfacial     aluminum    

Preparation, with graphene, of novel biomimetic self-healing microcapsules with high thermal stability

《结构与土木工程前沿(英文)》   页码 1188-1198 doi: 10.1007/s11709-023-0027-5

摘要: This paper reports a comparative study of microcapsules with enhanced thermal stability and electrical conductivity inspired by the bionic thermal insulation of birds’ feathers for self-healing aged asphalt. The work is based on an in situ polymerization with composite shell components of graphene and hexamethoxymethylmelamine resin. By using graphene, microcapsules with rough surfaces are achieved, improving the interface between microcapsules and asphalt. In addition, the microcapsules’ initial thermal decomposition temperature is appropriately high, so that the stability of the microcapsule in the asphalt highway system is protected. The proportion of graphene in the microcapsule shell can regulate the microcapsule’s heat resistance because graphene modifies the shell’s structural makeup. Additionally, the microcapsules’ electrical conductivity is relatively high. The self-healing capability of bitumen sharply increases, providing benefit to the effect of microcapsules on the properties of aged asphalt.

关键词: graphene     microcapsule     bitumen     heat insulation     conductivity    

Liquid metal enabled combinatorial heat transfer science: toward unconventional extreme cooling

Xiao-Hu YANG, Jing LIU

《能源前沿(英文)》 2018年 第12卷 第2期   页码 259-275 doi: 10.1007/s11708-017-0521-3

摘要: As a class of newly emerging material, liquid metal exhibits many outstanding performances in a wide variety of thermal management areas, such as thermal interface material, heat spreader, convective cooling and phase change material (PCM) for thermal buffering etc. To help mold next generation unconventional cooling technologies and further advance the liquid metal cooling to an ever higher level in tackling more extreme, complex and critical thermal issues and energy utilizations, a novel conceptual scientific category was dedicated here which could be termed as combinatorial liquid metal heat transfer science. Through comprehensive interpretations on a group of representative liquid metal thermal management strategies, the most basic ways were outlined for developing liquid metal enabled combined cooling systems. The main scientific and technical features of the proposed hybrid cooling systems were illustrated. Particularly, five abstractive segments toward constructing the combinatorial liquid metal heat transfer systems were clarified. The most common methods on innovating liquid metal combined cooling systems based on this classification principle were discussed, and their potential utilization forms were proposed. For illustration purpose, several typical examples such as low melting point metal PCM combined cooling systems and liquid metal convection combined cooling systems, etc. were specifically introduced. Finally, future prospects to search for and make full use of the liquid metal combined high performance cooling system were discussed. It is expected that in practical application in the future, more unconventional combination forms on the liquid metal cooling can be obtained from the current fundamental principles.

关键词: combinatorial heat transfer     liquid metal     high flux cooling     thermal management    

标题 作者 时间 类型 操作

Thermal performance of a single-layer packed metal pebble-bed exposed to high energy fluxes

Shengchun ZHANG, Zhifeng WANG, Hui BIAN, Pingrui HUANG

期刊论文

Heat transfer characteristics of high heat flux vapor chamber

Dongchuan MO, Shushen LU, Haoliang ZHENG, Chite CHIN,

期刊论文

Numerical study of a hybrid absorption-compression high temperature heat pump for industrial waste heat

Zhiwei MA, Huashan BAO, Anthony Paul ROSKILLY

期刊论文

Experimental investigation of liquid metal alloy based mini-channel heat exchanger for high power electronic

Manli LUO, Jing LIU

期刊论文

Impact of anthropogenic heat emissions on meteorological parameters and air quality in Beijing usinga high-resolution model simulation

期刊论文

High heat flux thermal management through liquid metal driven with electromagnetic induction pump

期刊论文

Creep of brazed plate-fin structures in high temperature compact heat exchangers

Shantung TU, Guoyan ZHOU

期刊论文

Exergy analysis of R1234ze(Z) as high temperature heat pump working fluid with multi-stage compression

Bin HU, Di WU, L.W. WANG, R.Z. WANG

期刊论文

Convective heat transfer in helical coils for constant-property and variable-property flows with high

Yufei MAO, Liejin GUO, Bofeng BAI, Ximin ZHANG

期刊论文

CONCENTRATIONS AND FLUXES OF DISSOLVED NUTRIENTS IN THE YANGTZE RIVER: LONG-TERM TRENDS AND ECOLOGICAL

期刊论文

Cutting heat dissipation in high-speed machining of carbon steel based on the calorimetric method

QUAN Yanming, HE Zhenwei, DOU Yong

期刊论文

Effective interventions on health effects of Chinese rural elderly under heat exposure

期刊论文

Interfacial heat transfer coefficient between metal and die during high pressure die casting process

GUO Zhipeng, XIONG Shoumei, CHO SangHyun, CHOI JeongKil

期刊论文

Preparation, with graphene, of novel biomimetic self-healing microcapsules with high thermal stability

期刊论文

Liquid metal enabled combinatorial heat transfer science: toward unconventional extreme cooling

Xiao-Hu YANG, Jing LIU

期刊论文