Multi-artery,heat-pipe spreader

Multiple, columnar liquid vapor chamber allows for effective heat removal from finite, concentrated heat source by heat spreading via lateral vapor flow, while minimizing conduction resistance through thinner evaporator wick. The individual liquid arteries are designed by wick coated solid pillar. We optimize the artery geometry, numbers, and distribution, for both liquid and air-cooled, finned condensers, and show that the overall thermal resistance is substantially lower than the uniform wick vapor chamber.     

热管技术及其应用分析

简要介绍了热管及热管换热器的发展现状,主要应用在利用热能、回收废热、节约原料、降低成本等方面,特别是在工业余热利用中发挥了越来越重要的作用,并取得了显著的经济效益。     

热管换热器在吉化化肥厂的应用

文章介绍了热管换热器结构的本质特点,并列举其在化肥工业领域中的几项应用实例,同时对热管换热器在吉化化肥厂中的开发应用提出了建议。     

热管式真空集热管的研制与应用

阐述了热管式真空集热管的基本构成及其特性,分析了热管式真空集热管研制的几个主要方面:热管和吸热板、玻璃管、选择性吸收涂层,玻璃一金属封接,真空度、聚光板.介绍了热管式真空集热管在太阳能热水系统、太阳热发电、太阳能制冷与空调、太阳能海水淡化等方面的应用,表明热管式真空集热管在太阳能中高温领域中具有广泛应用前景.     

常温热管换热性能的分析

以热管为传热元件的换热器具有传热效率高、结构紧凑、流体阻损小、有利于控制露点腐蚀等优点的新型传热元件。随着科学技术进步,热管的应用范围已经从航天、航天器中的均温和控温,扩展到了工业技术的各个领域。将热管传热原理应用于风能致热技术的传热中,作为传热元件,目的在于探讨热管技术在风能致热的热能进输送中应用的可能性,以期获得风能致热的基本数据,为实际应用提供基础。针对自行设计和研发的风车及磁涡流发热系统,通过对多组实验的测试,分析热管在不同蓄水量时的热导率,并对所测的数据进行归纳对比,得到了热管的有关传热规律。实验结果表明,热管的热导率随着蓄水量的增加而增大,其关系呈非线性关系。这对热管技术在风能致热的热能传输中的实际应用具有重要意义。     

Thermal performance of a flat-plate heat-pipe collector array

This article presents a theoretical model for the determination of the efficiency, the heat removal factor, and the outlet water temperature of a single collector and an array of flat-pipe heat-pipe collectors. The model is validated by on-site testing of 16 heat-pipe collectors under the typical weather conditions in Singapore. Within the operational range of interest of the hot water temperatures, the results show that the proposed model is sufficient to describe the steady-state performance of the collector array.     

提高抛煤机链条炉运行效率的实践

通过对抛煤机链条炉燃烧特点的分析,结合该类型锅炉多年运行管理和技术改造的经验,给出了抛煤机链条炉优化运行的建议.     

Thermosyphon heat-pipe evacuated tube solar water heaters for northern maritime climates

Under transient climatic conditions previous research has reported that evacuated tube solar water heaters (ETSWHs) with heat-pipe absorbers are the most effective solution for collection of solar energy. The cost of such systems is greater than the mass produced “water in glass” evacuated tube solar water heater mainly manufactured in China. Previous studies have reported that the costs of solar water heating can be reduced through the adoption of thermosyphon fluid circulation. Well designed thermosyphon systems are as effective as pumped systems but with lower capital and running costs. To investigate if costs could be reduced and performance levels maintained, outdoor testing of three thermosyphon heat-pipe ETSWHs primarily designed for pumped fluid circulation was carried out under a northern maritime climate. Experimental data from a year’s side by side monitoring of two thermosyphon ETSWHs (both with the same area of 2 m²) was collected and used to validate a correlation based on a modified version of the f-chart design tool between the observed and expected performance for both systems. The R² value between measured and predicted monthly solar fractions was greater than 0.99 for both systems. The R² value between measured and predicted diurnal solar fractions was calculated as greater than 0.95 for both systems. The only difference between the two was that one utilised internal heat-pipe condensers whilst the other used external ones. The system with internal condensers was found to be 17% more efficient. A simplifying assumption of a constant temperature rise across the collectors reduced the calculations required to predict the performance of thermosyphon heat-pipe ETSWHs and was also statistically significant. To determine if the assumption was valid for other thermosyphon heat-pipe ETSWHs with different collector parameters a third system with internal condensers an area of 3 m², a heat removal factor (F_R) of 0.816 based on the absorber area and a collector loss coefficient (F_RU_L) of 2.25 W m^?2 K^?1 was assembled and its performance monitored, when the same assumption was applied the R² value between the measured and predicted daily solar fractions was calculated as 0.96 experimentally demonstrating that this relationship was still statistically significant for another heat-pipe thermosyphon ETSWH with different collector parameters.     

Thermal performance of flat vapor chamber heat spreader

Experiments were performed to examine the spreading thermal resistance of centrally positioned heat sources and the thermal performance of a water charged, gravity assisted flat vapor chamber to be used for electronic cooling. Parametric studies including different heat fluxes and operating temperatures were conducted, and the effect of the relevant parameters on the cooling performance in terms of the spreading resistance was presented and discussed. The present vapor chamber heat spreader showed a heat removal capacity of 220 W/cm² with a thermal spreading resistance of 0.2 °C/W.     

Heat-transfer characteristics of a closed-loop oscillating heat-pipe with check valves

The heat-transfer characteristics of this system i.e. a CLOHP/CV, depend on the ratio of check valves (R_cv), aspect ratio (L_e/d_i) and the dimensionless parameters of the heat transfer. The CLOHP/CV used employed a copper tube with inner diameters of 1.77 and 2.03 mm. The evaporator, adiabatic and condenser lengths were equal to 50, 100 and 150 mm. The selected working fluids were water (H₂O), ethanol (C₂H₅OH) and R123 (CHCl₂CF₃) with a filling ratio of 50% of total volume. The number of turns was 40. The R_cv values were 20, 8, 5 and 4. The evaporator was heated by hot water, while the condenser section was cooled by distilled water. The inclination of the CLOHP/CV used in the experiments was 90° to the horizontal, with a controlled working-temperature of 50 °C. When the system reached the steady state, the temperature and the flow rate of the cooling water were measured in order to calculate the heat-transfer rate of the CLOHP/CV. The experimental results showed that the heat-flux increases with an increase of R_cv and decreases with an increased aspect ratio. A correlation for predicting the heat-transfer rate for the heat-pipe in the vertical position has been established.     

A parabolic solar collector heat-pipe heat exchanger reactor assembly for cyclohexane's dehydrogenation: A simuation study

Hydrogen is an optimum large scale fuel for the future, although there remain some problems in transport and long-term storage. One has to develop the use of alternative fuels that are easily transformed into hydrogen and that can be stored in liquid form, and, thus, more safely and economically. A simulation study on the possibility of the utilisation of cyclohexane as a vector for hydrogen storage, itself used as a vector of solar energy storage, has been carried out. The results of this study indicate that a dehydrogenation muti-tube reactor for cyclohexane is feasible. Neverthless, a good heat transfer, which is a limiting process, has to be assured. To heat this reactor a system of a Parabolic Solar Collector heat pipe heat exchanger reactor assembly (PSCHPHERA) is studied.     

The application of adjoint sensitivity theory to a liquid fuels supply model

Adjoint sensitivity theory has been applied to a liquid fuels supply model to determine the sensitivity of calculated results to the parameters in the model. The power of the adjoint sensitivity methodology is that it provides, in principle, an efficient means of calculating the sensitivity, $\text{d}\text{R}\text{d}\text{x}$, of any calculated result R to every parameter x in the model. The liquid fuel supply model considered is one of a class of models that may be constructed from the Generalized Equilibrium Modeling System (GEMS) developed at Decision Focus, Inc., Los Altos, California. It is shown that for this class of models the lengthy development effort that is usually associated with applying the adjoint sensitivity methodology can be avoided by using the GEMS program to evaluate the large number of partial derivatives that are needed to apply the methodology.     

A novel hybrid heat-pipe solar collector/CHP system—Part II: theoretical and experimental investigations

A theoretical analysis has been carried out to investigate the thermodynamic and heat transfer characteristics of a hybrid heat pipe solar collector/CHP system based on the assumption that the system operates on a typical Rankine cycle. Experimental testing of the prototype was also carried out using two types of turbine units. The variation of refrigerant pressures and temperatures, hot water temperatures in the collector and boiler systems, as well as chill water temperatures were recorded. The results were used to estimate the heat from the boiler and the solar collectors, the electricity and hot water generation (indicated as kW energy) from the CHP operation and the gas consumption of the system. The modelling and experimental results were compared for the impulse-reaction turbine system, and a simple analysis of the energy and environmental benefits of the system was carried out. The analysis indicated that the proposed system would save primary energy of approximately 3150 kWh per annum compared to the conventional electricity and heating supply systems, and this would result in reduction in CO₂ emission of up to 600 tonnes per annum. The running cost of the proposed system would also be lower than conventional heating/power systems.     

Two-dimensional transient thermal analysis of a phase-change-material canister of a heat-pipe receiver under gravity

High-temperature Phase Change Material （PCM） is used as a thermal storage medium of a heat-pipe receiver in an advanced solar dynamic system. With both void cavity and natural convection considered, thermal performance of the heat-pipe receiver is numerically analyzed under gravity. The results indicate that the PCM contained in the integrated heat pipe performs an averaging function of heat loadings. The thermal performance of the heat-pipe receiver is stable and reliable. When a heating cycle is stable, the temperature fluctuations both on heat-pipe wall and in PCM canister remain less than 13 K throughout a sunlight and eclipse cycle. The utility of PCM is essentially improved. The maximum melting ratio of PCM is 92%. Under gravity, PCM melts more quickly with the effect of natural convection. Natural convection accelerates the process of phase changes. Numerical results are compared with the experimental results concerned. The accuracy of numerical model under gravity is verified. The experiment for the PCM canister on the ground can be well prepared with our numerical simulation.     

Optimized solar-powered liquid desiccant system to supply building fresh water and cooling needs

This paper studies the feasibility of using a solar-powered liquid desiccant system to meet both building cooling and fresh water needs in Beirut humid climate using parabolic solar concentrators as a heat source for regenerating the liquid desiccant. The water condensate is captured from the air leaving the regenerator. An integrated model of solar-powered calcium chloride liquid desiccant system for air dehumidification/humidification is developed. The LDS model predicted the amount of condensate obtained from the humid air leaving the regenerator bed when directed through a coil submerged in cold sea water. An optimization problem is formulated for selection and operation of a LDS to meet fresh water requirement and air conditioning load at minimal energy cost for a typical residential space in the Lebanon coastal climate with conditioned area of 80 m² with the objective of producing 15 l of fresh drinking water a day and meet air conditioning need of residence at minimum energy cost. The optimal regeneration temperature increases with decreased heat sink temperature with values of 50.5 °C and 52 °C corresponding to sink temperatures of 19 °C and 16 °C.     

供热与集热模式下热管式太阳能PV/T热泵系统实验研究

文章搭建了热管式太阳能PV/T热泵系统,设计了供热和集热两种运行模式,并选取了日均太阳辐射强度和室外温度基本接近的两个工作日,对两种运行模式下,该系统的各项性能进行了实验研究。分析结果表明,供热模式下,热管式PV/T热泵系统日均热效率为33.9%,日均电效率为12.2%,比单一光伏发电系统的日均电效率提高了25.7%,日均COPth、日均COPpv/t分别为2.52,3.26;集热模式下,热管式PV/T热泵系统日均热效率为25.3%,日均电效率为12.9%,比单一光伏发电系统的日均电效率提高了14.2%,日均COPth、日均COPpv/t分别为1.82,2.33。因此,供热模式下热管式太阳能PV/T热泵系统的绝大部分性能优于集热模式。     

余热回收高效节能热管换热器应用与工作介质的研究

本文对热管的工作原理做了介绍,叙述了多年来设计的热管换热器及其应用情况,重点阐述了热管对其工作介质的要求和对目前常用的几种工作介质进行了分析研究。     

10t／h抛煤机链条炉的节能改造数值模拟分析

针对SZD10-13-AII型抛煤机锅炉存在的燃烧不强烈、冒黑烟、飞灰含碳量大、热效率低以及燃料消耗量大的问题,提出使用短前拱与二次风组合、长折焰拱及高温飞灰分离及流化复燃技术等的改造方案。使用CFD软件对改造前后的锅炉炉内的速度场和温度场进行模拟计算与对比。研究结果表明,改造后的抛煤机链条炉燃烧强烈,烟气充满度高。设计运行结果表明．锅炉的燃烧效率、烟气排放浓度等均达到所需的指标.