Heat units-based potential yield assessment for cotton production in Uzbekistan

Cotton yields in Uzbekistan are significantly lower than those in similar agro-climatic regions,requiring the estimation of crop potential and baseline yield to track progress of production enhancement efforts.The current study estimated potential cotton development and baseline yield(maximum given no production constraints)using total heat units(THU)and potential cotton yield(PCY),respectively.Calculations were based on heat units(HU)for a 30-year(1984-2013)period.Long-term average THU and PCY,as well as PCY at three different exceedance probabilities(p=0.99,p=0.80,and p=0.75),were calculated for 21 selected weather stations across cotton-growing areas of Uzbekistan.After confirmation that the current planting date(April 15)is optimal,a comparison of THU with the accepted cotton production cutoff threshold(1444°C)suggested that areas with lower elevations and latitudes are more appropriate for cotton production.Yield gap analysis(relative difference between long-term average PCY and actual yields)confirmed that Uzbekistan cotton production is below potential,while the spatial distribution of yield gaps outlined where efforts should be targeted.Areas near the stations of Nukus,Kungrad,Chimbay,and Syrdarya should be further investigated as benefit/cost ratio is highest in these areas.A comparison between state-set yield targets and PCY values,taking into account climatic variability,suggested that all areas except Jaslyk,Nurata,and Samarkand have safe,appropriate targets.These results present a starting-point to aid in strategic actions for Uzbekistan cotton production improvement.

Parallel Operation Characteristics Analysis of Sewage Source Heat Pump Units in Winter

Sewage source heat pump unit operates under partial load most of the time, and study on the law of coefficient of performance (COP) of the unit varying with load ratio can provide basis for the heat pump units running in high efficiency. A mathematical model determining COP, evaporation temperature and condensation temperature of a single unit was proposed. Under the condition of uniform load distribution, the model was established according to different ways of bearing partial load with the same type multi...

3D simulation on the unit duct in the shell side of the ROD baffle heat exchanger

The ROD baffle heat exchanger can slightly enhance the shell side heat transfer coefficient with the significant reduction of pressure, loss due to the shell side fluid flowing longitudinally through tube bundle, which leads to the reduction of the manufacture and running cost and in some cases to the dimensions reduction of the heat exchangers. Because of the complexities of fluid dynamics equations and the structure of heat exchangers, few theoretical researches have been accomplished to specify the shell side characteristics of the ROD baffle heat exchanger. A unit duct model in the shell side of the longitudinal flow type heat exchanger has been developed based on suitable simplification. A numerical analysis on shell side of the ROD baffle heat exchanger has been carried out at constant wall temperature to obtain the characteristics of heat transfer and pressure drop. The numerical results show that the ROD baffles placed vertically and horizontally in the unit duct continue to shear and comminute the streamline flow when the fluid crosses over the ROD-baffles, and change the fluid flow directions, and then the continuity and stability of the fluid axe destroyed. The effect of disturbing flow can promote fluid turbulent intensity and effectively enhance heat transfer. The numerical analyses can provide the theoretical bases for optimizing the structure of ROD baffle heat exchanger and improving its performance.

Thermodynamic Simulation of CCP in Air-Cooled Heat Pump Unit with HFCs and CO₂Trans-Critical

The exergy analysis and finite time thermodynamic methods had been employed to analyze the compound condensation process (CCP). It was based on the air-cooling heat pump unit. The cooling capacity of the chiller unit is about 1 kW, and the work refrigerant is R22/R407C/R410A/CO2. The MATLAB/SIMULINK software was employed to build the simulation model. The thermodynamic simulation model is significant for the optimization of parameters of the unit, such as condensation and evaporation temperature and mass flow of the sanitary hot water and size of hot water storage tank. The COP of the CCP of R410A system is about 3% - 5% higher than the CCP of the R22 system, while CCP of the R407C system is a little lower than the CCP of R22 system. And the CCP of CO2 trans-critical system has advantage in the hot supply mode. The simulation method provided a theoretical reference for developing the production of CCP with substitute refrigerant R407C/R410A/CO2.

Retrofit of the Heat Recovery System of a Petroleum Refinery Using Pinch Analysis

Energy efficiency has become an important feature in the design of process plants with the rising cost of energy and the more stringent environmental regulations being implemented worldwide. In South Africa, as elsewhere, most process plants built during the era of cheap energy place little emphasis on the need for energy recovery due to the abundance of cheap utilities sources such as coal. In most of these plants, there exist significant potential for substantial process heat recovery by conceptual design of the heat recovery system. By maximizing heat recovery from the processes, there will be a reduction in the process utilities requirement and the associated environmental effects. Pinch analysis has been demonstrated to be a simple but very effective tool for heat integration and optimization of chemical plants. This study uses the pinch principle to retrofit the heat exchanger networks (HEN) of the crude distillation unit of an integrated petroleum refinery to evolve a HEN that features optimum energy recovery. The network was further relaxed by trading off energy cost with capital cost to obtain an optimal HEN topology not too different from the existing network. The simulation works were implemented in AspenPlus v8.0 environment. Analysis revealed that 34 per cent saving on energy usage per annum is realizable. This significant saving in energy also results in diminished gaseous pollutants associated with energy usage.

配置吸收式热泵的热电联产机组厂级智能运行优化

为提高配置吸收式热泵的热电联产机组的全厂运行经济性,基于案例电厂的运行历史数据,使用滑动窗口法进行数据预处理并提取稳态工况,建立配置吸收式热泵的热电联产机组煤耗预测数学模型。以全厂热电联产机组总煤耗最小为适应度函数,利用粒子群优化算法求解得出配置吸收式热泵的热电机组最佳背压和各台热电机组最佳抽汽量。基于以上研究设计了供热系统智能优化软件,实现供热系统在线监测与优化调节,对各供热单元分别提出优化指导,使机组运行经济性最佳,进而降低整体煤耗。计算结果表明:实行供热系统智能优化策略可为案例电厂供热系统平均每小时节省标准煤约1.81 t,节能效果显著。

Characterizing the Urban Temperature Trend Using Seasonal Unit Root Analysis:Hong Kong from 1970 to 2015

This paper explores urban temperature in Hong Kong using long-term time series. In particular, the characterization of the urban temperature trend was investigated using the seasonal unit root analysis of monthly mean air temperature data over the period January 1970 to December 2013. The seasonal unit root test makes it possible to determine the stochastic trend of monthly temperatures using an autoregressive model. The test results showed that mean air temperature has increased by 0.169~ C （10 yr） - 1 over the past four decades. The model of monthly temperature obtained from the seasonal unit root analysis was able to explain 95.9% of the variance in the measured monthly data -- much higher than the variance explained by the ordinary least-squares model using annual mean air temperature data and other studies alike. The model accurately predicted monthly mean air temperatures between January 2014 and December 2015 with a root-mean-square percentage error of 4.2%. The correlation between the predicted and the measured monthly mean air temperatures was 0.989. By analyzing the monthly air temperatures recorded at an urban site and a rural site, it was found that the urban heat island effect led to the urban site being on average 0.865~C warmer than the rural site over the past two decades. Besides, the results of correlation analysis showed that the increase in annual mean air temperature was significantly associated with the increase in population, gross domestic product, urban land use, and energy use, with the R2 values ranging from 0.37 to 0.43.

三套管式加肋相变蓄热单元的强化传热特性

相变蓄热技术在利用工业余热、太阳能等解决热能与用户之间的供需不平衡问题方面起着重要的作用,然而受相变材料自身物性的限制,蓄热熔化时仍存在蓄热速度低、熔化不均匀等问题。本文以三套管式相变蓄热单元为基本结构,利用FLUENT软件模拟研究了在考虑自然对流情况下添加纵向肋片的不同参数(肋片数量、长度、厚度、偏心距及肋片排布方式)对三套管式相变蓄热单元蓄热性能的影响。结果表明,三套管式蓄热单元内外双壁面共同加热,与普通套管式蓄热单元相比,换热面积增大,相变材料全部熔化需要的时间缩短;加装纵向直肋片的三套管蓄热单元的熔化速度进一步加快,相同数量肋片下,肋片的长度和厚度是影响蓄热单元蓄热量与平均蓄热速率的主要因素,肋片长度占相变材料区域径向长度的50%时,蓄热单元的熔化速度加快幅度明显且蓄热量与平均蓄热速率较高。通过优化设计,发现内管向下偏移距离e对相变材料的熔化过程作用显著,偏心距离较短时相变材料完全熔化所需时间最少,相比光滑管蓄热单元,相变材料的熔化速率提升了48.5%,偏移距离过长则会延长蓄热时间;通过加密蓄热单元底部外层肋片的排布,蓄热单元的熔化进程有不同程度的加快,总体蓄热速率较原肋片结构有所提高。

集成蓄热装置的火电机组调峰特性分析

【目的】随着新能源的大规模发展,新能源出力不确定性和波动性问题展现出来,而为了弥补新能源出力缺点,火电机组承担起了调峰作用。为了提升火电机组的调峰能力,对其调峰特性进行了研究。【方法】首先,以某350 MW供热机组作为分析对象,应用仿真软件搭建热力系统模型,并验证该模型的精确性。其次,以蓄热系统为辅助系统,研究机组在满足供热需求情况下的机组调峰能力,并分析蓄热等储能单元对机组调峰能力的影响。最后,采用启发式粒子群算法对蓄热水罐运行策略进行优化,得到随热负荷变化的储热罐最优运行模式。【结果】通过蓄热水罐与火电机组耦合的方法有效提升了机组的调峰和供热能力,并提出可以根据实际热负荷数据确定最大化收益的运行模式。【结论】该方法对机组的运行策略具有指导意义。

Experimental Study on Performance of Supercritical CO_2 Heat Exchanger with Four Different Inner Tubes

The experiment was conducted to investigate the heat transfer performance of supercritical CO_2 in a casing heat exchanger by comparing their heat transfer,entropy production unit number,non-dimensional entropy production rate and field synergy factor.The results show that both heat transfer and entropy production unit number in four tubes decrease with water temperature increasing.Heat transfer and entropy production unit number in multiple tubes( i. e.,triple straight tube and double helix tube) is higher than their single counterparts; the non-dimensional entropy production rate increases with water temperature. Non-dimensional entropy production rate of triple straight tube and double helix tube is far below the single tube. Field synergy factor of double helix tube is much higher than that of the triple straight tube under the same condition. Further experiment was carried out in double helix tube,under various CO_2 pressure and inlet water temperature,the results are analyzed and reported in this paper.

某大科学装置项目工艺冷却水系统设计

介绍了某在建大科学装置项目的工艺冷却水系统设计,包括服务对象、系统形式、系统组成、水温控制策略、流量控制策略等方面的内容。简述了热回收型水源热泵在工艺冷却水系统中的应用方案,并对工艺冷却水系统设计后续可开展的工作和研究提出了3个方向。

煤电机组余热能质深度回收优化研究

针对煤电机组低品位余热能质浪费问题,以某350MW机组为研究对象,采用Ebsilon平台建模模拟研究不同的低品位余热能质深度回收方案,计算“有机朗肯循环(organic Rankinecycle,ORC)”和“加热器”2种方案对应机组运行数据,分析能耗特性、收益特性和差异性等,得到了余热能质深度回收的机理和优化方案。结果表明:2种方案下机组能耗特性均有明显提升,“加热器”方案能耗更低;随着有机工质流量增加,ORC系统发电量逐渐增大,ORC系统热电效率先逐渐增大后趋于平缓并有下降趋势,变化范围为6.94%~7.75%,有机工质流量对ORC系统循环效率影响较小;2种方案技术经济均可行,“ORC”方案可以为电厂带来直接电能收益,“加热器”方案经济性略好。

水冷冷水机组热回收的节能分析

本文首先介绍了夏热冬暖地区生活热水系统常用的三种热水供给方案,并对其所用的热源机组进行能效分析及能耗分析,把空调制冷与生活热水作为一个整体,具体计算了三种方案热源机组的单位制热量耗电指标,这一指标的计算结果表明了回收水冷冷水机组的冷凝余热用于生活热水系统节能效果明显,且在此基础上推导出不同环境温度下运行经济性最佳的水冷冷水机组热回收温度,进而通过工程实例广东佛山某酒店项目的生活热水系统热源机组年能耗计算佐证之。本文量化分析了水冷冷水机组热回收的节能效果以及热回收温度对节能效果的影响,以期为水冷冷水机组热回收的应用及运行提供有益的参考和指导。

灵活性驱动下的热电联产机组多目标协同控制策略

灵活性提升会显著影响热电联产机组的热舒适性及运行经济性等性能,为实现机组大范围快速变负荷过程中的综合性能优化,提出了一种基于预测控制的机组多目标协同控制策略。首先,建立了一套考虑灵活性、热舒适性、经济性及平稳性的机组多目标评价指标体系,为实现多目标协同,设计了一种基于预测控制的机组电热协调控制策略,在滚动优化中引入煤耗指标实现经济优化,并给出了多目标控制律的求解方法;然后,以多目标评价指标作为粒子群优化的目标函数,基于仿真模型离线寻优,获得了控制策略中的最佳参数设定,实现了机组综合性能的优化;最后,以某300 MW机组为例进行了仿真测试。结果表明:该策略可提升热电联产机组的运行灵活性,并在较大程度上保证机组的热舒适性和运行经济性,为热电联产机组的多目标优化控制提供了依据。

An Efficient Acceleration of Solving Heat and Mass Transfer Equations with the First Kind Boundary Conditions in Capillary Porous Radially Composite Cylinder Using Programmable Graphics Hardware

With the latest advances in computing technology, a huge amount of efforts have gone into simulation of a range of scientific phenomena in engineering fields. One such case is the simulation of heat and mass transfer in capillary porous media, which is becoming more and more necessary in analyzing a number of eventualities in science and engineering applications. However, this procedure of numerical solution of heat and mass transfer equations for capillary porous media is very time consuming. Therefore, this paper pursuit is at making use of one of the acceleration methods developed in the graphics community that exploits a graphical processing unit (GPU), which is applied to the numerical solutions of such heat and mass transfer equations. The nVidia Compute Unified Device Architecture (CUDA) programming model offers a correct approach of applying parallel computing to applications with graphical processing unit. This paper suggests a true improvement in the performance while solving the heat and mass transfer equations for capillary porous radially composite cylinder with the first type of boundary conditions. This heat and mass transfer simulation is carried out through the usage of CUDA platform on nVidia Quadro FX 4800 graphics card. Our experimental outcomes exhibit the drastic overall performance enhancement when GPU is used to illustrate heat and mass transfer simulation. GPU can considerably accelerate the performance with a maximum found speedup of more than 5-fold times. Therefore, the GPU is a good strategy to accelerate the heat and mass transfer simulation in porous media.

An Efficient Acceleration of Solving Heat and Mass Transfer Equations with the Second Kind Boundary Conditions in Capillary Porous Composite Cylinder Using Programmable Graphics Hardware

With the recent developments in computing technology, increased efforts have gone into simulation of various scientific methods and phenomenon in engineering fields. One such case is the simulation of heat and mass transfer in capillary porous media, which is becoming more and more important in analysing various scenarios in engineering applications. Analysing such heat and mass transfer phenomenon in a given environment requires us to simulate it. This entails simulation of coupled heat mass transfer equations. However, this process of numerical solution of heat and mass transfer equations is very much time consuming. Therefore, this paper aims at utilizing one of the acceleration techniques developed in the graphics community that exploits a graphics processing unit (GPU) which is applied to the numerical solutions of heat and mass transfer equations. The nVidia Compute Unified Device Architecture (CUDA) programming model caters a good method of applying parallel computing to program the graphical processing unit. This paper shows a good improvement in the performance while solving the heat and mass transfer equations for capillary porous composite cylinder with the second kind of boundary conditions numerically running on GPU. This heat and mass transfer simulation is implemented using CUDA platform on nVidia Quadro FX 4800 graphics card. Our experimental results depict the drastic performance improvement when GPU is used to perform heat and mass transfer simulation. GPU can significantly accelerate the performance with a maximum observed speedup of more than 7-fold times. Therefore, the GPU is a good approach to accelerate the heat and mass transfer simulation.

Application of Solid Oxide Fuel Cell-Auxiliary Power Unit on Different Trucks in Northeast China

A diesel engine of conventional trucks has a low efficiency under the idling condition,leading to a high cost for heating or cooling in the cab during night. The solution to this problem will have great significance on energy conservation and emission reduction. A new auxiliary power unit of solid oxide fuel cell( SOFCAPU) with high efficiency solves this problem perfectly. Heat pump air conditioner is considered as a promising device for the application of SOFC-APU with a high cooling and heating efficiency. To make a quantitative analysis for the application of SOFC-APU,a model is built in Matlab / Simulink. The diesel engine model and SOFC-APU model are fitted based on some experimental data of SOFC-APU and diesel engine during the idling operation. An analysis of the application of SOFC-APU on different trucks in Northeast China is comprehensively made,including efficiency and emission.

风-火-储耦合系统储能容量配置优化对比

为提升风电富集区域风电消纳水平及燃煤机组的灵活性,提出了基于热电共蓄式压缩空气储能的风-火-储耦合系统及系统调度策略,建立了系统的容量配置优化框架,并对7种布局方案进行了多目标优化。优化结果表明:电锅炉将弃风电量转化为热量时,燃煤机组的运行点向电力负荷下限更低的区域移动,风电上网空间增大,燃煤机组出力水平降低;加入热电共蓄式压缩空气储能子系统,使得燃煤机组电功率水平降低;换热器废热的回收进一步降低了燃煤机组产热水平;通过调整燃煤机组热出力,抽汽蓄热子系统能够实现抽汽热的时空平移,促使燃煤机组运行点向电力负荷下限更低的区域移动,可间接促进风电的消纳。综合来看,3种子系统相组合的最佳耦合方案可实现燃煤机组的热电解耦,从而提升了其深度调峰能力,在更大程度消纳风电能力的同时提升了系统的效率和环保性。

基于圆台波浪形换热管的潜热储热单元性能分析

为提高潜热储热单元(latent heat storage unit,LHSU)的储热性能,提出了三种优化换热管结构的新型LHSU,分别为圆台形换热管潜热储热单元、波浪形换热管潜热储热单元和圆台波浪形换热管潜热储热单元(frustum wavy heat transfer tube latent heat storage unit,FW-LHSU)。基于数值模拟方法,比较了传统圆柱形换热管潜热储热单元(cylindrical heat transfer tube latent heat storage unit,C-LHSU)和三种新型LHSU的储热性能。此外,针对FW-LHSU研究了换热管壁面倾斜角度对储热性能的影响。结果发现,所提出的三种新型换热管结构均能增强储热性能,其中FW-LHSU储热效果最好,与C-LHSU相比,FW-LHSU的熔化时间缩短了32.64%,储热速率密度提高了48.1%。当增加FW-LHSU的换热管壁面倾斜角度时,其储热性能可进一步提高。当换热管倾斜角度从2°增加到8°时,FW-LHSU的储热时间可缩短37.00%、储热速率密度可提高48.44%。

Performance of Thermal Energy Storage Unit Using Solid Ammoniated Salt (CaCl₂-NH₃System)

The exothermic chemical reaction of CaCl2 (calcium chloride) with NH3 (ammonia) can be utilized as an energy storage system. Since this reaction is a typical gas-solid reaction, the reaction rate is controlled by the heat transfer rate. In order to improve the low heat transfer rate of the ammoniation and the deammoniation of CaCl2, the influence of a heat transfer media (Ti: titanium) on the heat transfer rate of the solid ammoniated salt (CaCl2&#46mNH3) was studied and tested experimentally. The performance tests were carried out under the conditions of various weight ratios of Ti. No decrease of the activation of chemical reaction and no corrosion of experimental apparatus were observed on the repeated runs (≥30 times each). The heat transfer rate of ammoniated salt was greatly improved by adding Ti under the constant pressure (0.5 MPa). The reaction time required for the ammoniation of CaCl2 mixed with Ti was approximately 16% - 54% shorter than that of CaCl2 alone, and the reaction time required for the deammoniation was also approximately 19% - 59% shorter than that of CaCl2 alone.