热管管外结冰过程研究

通过对热管制冰传热过程的理论分析,得出影响结冰速率的主要因素是热管的温度与半径.建立了管外结冰一维传热模型,分别以半径和时间为步长对结冰速率进行迭代求解,并利用半径微元法得出了不同温度以及不同圆管半径下的制冰速率曲线.与试验结果相比,所得理论模型能够较好地与其吻合.     

冬季供暖工况下混凝土辐射顶板传热特性

针对冬季供暖工况下混凝土辐射顶板的传热问题,建立顶板辐射供暖的简化数学模型,利用MATLAB软件计算其供热量,并通过该顶板辐射供暖的热工特性实验验证模型的合理性。研究表明:顶板温度计算值与实验结果的误差在5.01%以内,供热量计算值与实验结果的误差在5.15%左右。通过对实验和计算结果的分析发现:在定流量稳态工况下,顶板温度随供水温度的增大呈指数性增大,随换热盘管间距的增大而减小。     

利用频域有限元法分析内嵌管式辐射地板频域热特性

分析内嵌管式辐射地板的频域热特性,便于进一步了解内嵌管式辐射地板的动态热特征,为辐射地板的系统和控制设计提供重要的参考依据。建立了内嵌管式辐射地板的频域有限元模型,同时采用ANSYS软件建立了内嵌管式辐射地板的时域传热模型,通过2个模型的对比说明了频域有限元模型的准确性。采用频域有限元模型计算并分析了内嵌管式辐射地板的频域热特性。结果表明,在低频区域,地板的频域热响应基本不随频率变化,其传热过程接近于稳态,而在高频区域,地板的频域热响应随频率的变化十分剧烈,地板传热呈现明显的动态特征。当房间内存在较多成分的高频热扰时,关于辐射地板的传热计算应采用动态计算方法。     

地下水渗流作用下地埋管间歇散热特性

为了探求地下水渗流对地埋管换热器间歇运行性能所产生的影响,基于移动的有限长线热源理论模型解析解,利用MATLAB软件编程计算,分析渗流对单钻孔地埋管换热器的影响。同时对比分析了连续和间歇运行情况下其周围土壤的温度响应特征和过余温度场分布特点。研究表明：埋管周围土壤的温度变化是由热流密度、土壤本身的热物性和实际渗流速度耦合作用影响的,而在间歇运行下其因素影响更加明显。     

冷却干燥通风过程中粮仓内热湿耦合传递的数值模拟

基于多孔介质传热传质的理论,建立了一种冷却干燥通风过程中粮仓内热湿耦合传递的数学模型。借助数值模拟的方法,对冷却干燥通风过程中粮仓内温度和水分的变化进行了模拟研究,得到了冷却干燥通风过程中粮堆内部热量传递和水分迁移的基本规律。     

二维高炉区域BFC网格生成技术及其Matlab实现

利用数学模型对高炉冶炼过程进行模拟是高炉炼铁新工艺研发的有效方法,网格生成技术是数值模拟过程中重要的前处理过程,是高炉模拟计算的先决条件。生成网格的质量对高炉模型模拟的精度、效率以及收敛性具有重要影响,因此,建立优质的网格对高炉数学模型的求解具有重要意义。文中提出了一种适用于高炉数学模型的适体坐标系(BFC)网格的生成方法,从求解区域的划分、椭圆型方程的转换、椭圆型方程的离散及BFC网格生成步骤等方面进行了研究,并把死料区的边界作为BFC网格计算的边界条件,使数学模型的求解过程得以简化。采用带有源项的泊松方程作为变换方程,网格的正交性和疏密程度便于控制。该网格生成算法原理简单、易于编程、网格生成效率高,生成的网格能够满足数学模型求解的要求。     

超燃冲压发动机性能的准二维计算方法

为了能在双模态超燃冲压发动机流道方案初步论证中提供一种较快速的发动机性能计算方法,在二维N-S方程基础上,引入一维完全燃烧计算方法,提出了预估超燃冲压发动机性能的准二维计算方法。该方法能够计入激波、边界层分离等对发动机性能的影响,可在较短时间计算出整机推力、比冲性能和沿程热力学参数。通过对自由射流发动机计算,验证了此方法。并在此基础上,初步分析了燃料喷注位置和流道构型对发动机性能的影响。      

基于遥感和GIS的柴达木盆地太阳能估算方法研究

为了科学了解太阳能资源,验证地面实测气象资料与卫星资料的相关性,通过利用遥感和GIS技术,对青海高原太阳能资源丰富区——柴达木盆地的太阳能资源进行反演,以回归统计法求取地面总辐射,用红外资料、可见光和红外数字卫星等资料,估算地面总辐射并与地面实测气象资料进行对比分析,并进行模型检验。结果表明：遥感资料反演和实测值变化很吻合,相关系数超过90%。利用静止气象卫星FY2C资料反演计算地表太阳总辐射,能填补气候学方法的不足,能提高定量研究辐射的空间精度。     

甘肃西部冷凉灌区春小麦综合栽培措施与产量关系模型的研究

本试验采用二次回归通用旋转组合设计的原理和方法,以对春小麦产量影响较大的播种密度、施氮量、施磷量3项主要因素为决策变量,产量为目标函数,建立了甘肃春小麦生产区主要农艺栽培措施与产量关系的数学模型,通过频数寻优,定量化选出了灌区春小麦实现高产的综合农艺栽培措施优化组合方案,分析讨论了各因子及其互作效应对产量的影响,筛选出了产量≥8 000 kg/hm~2的优化农艺措施组合方案。     

热流固耦合作用下页岩渗透特性实验

为探讨地温对页岩渗流特性的影响规律,按照温度对页岩作用部位的不同,从流体动能、骨架应变、吸附解吸三个方面,分析甲烷内摩擦力对动能的影响、页岩热应力及热膨胀导致应变、甲烷解吸引起基质收缩随温度变化的规律,得出热流固耦合作用下页岩渗流特性。以渝东南酉阳龙马溪组页岩样品为分析对象,进行页岩型岩的温度渗流实验,提出三方面五因素的分析方法：温度增加,流体内摩擦力增大减小了流动速度;粘土矿物与有机质的差异性膨胀产生热应力,压缩了页岩骨架,加之基质热膨胀减小了基质间隙,双重作用使渗流通道减小;基质收缩效应对孔隙裂隙双重结构介质渗透量影响很小。温度升高对页岩渗流特性的主要影响体现为,内摩擦力的减速作用及热应力和热膨胀对渗流通道的压缩作用。     

Modeling and Performance Analysis of Unglazed Solar Collector/Regenerator

An analytical model of the unglazed solar collector/regenerator(C/R) was presented. There was an optimum flow rate per unit collector area at normal temperature which led to the maximum evaporation rate. The inlet temperature of absorbent solution and the wind velocity are key parameters to determine the optimum flow rate, in addition, the concentration of solution and solar radiation intensity have obvious effects on the maximum evaporation rate. When the outlet temperature of solution is higher than the inlet temperature, there is not an optimum flow rate, which reflects that the more the flow rate of solution is, the better regeneration efficiency is. With the 2m/s of wind speed, the evaporation rate reaches the peak. In this paper, kinds of factors influencing the performance of solar C/R were evaluated as well.     

Dropwise Condensation Heat Transfer Coefficient on the Horizontal Circular Surface with Radial Gradient Surface Energy

A theoretical model is developed for the dropwise condensation heat transfer on the horizontal circular surface with radial gradient surface energy based on the heat transfer model of individual condensate drop and the size distribution model of condensate drop on homogeneous condensation surface.The effect of variation of contact angle on the gradient surface on condensation heat transfer and condensate drop size distribution is taken account of in this model.The theoretical calculation method was obtained to predict the dropwise condensation heat transfer coefficient on the horizontal circular surface with radial gradient surface energy under various wall subcooled temperature,contact angle profile on wall surface,and working fluid.The effects of surface energy gradient,wall subcooled temperature,and thermophysical properties of condensate on the condensation heat transfer are discussed respectively.The calculation results show that the condensation heat transfer coefficient increases slightly with the increase of wall subcooled temperature.As latent heat and surface tension increasing,the condensation heat transfer coefficient increases.A larger surface energy gradient induces a larger condensation heat transfer coefficient.     

Heat transfer performance analysis of lithium bromide solution falling film evaporation in vertical tube

For making the refrigeration system directly driven by low temperature waste flue gas heat more efficiently,an experimental research on the heat transfer of vertical in tube laminar falling film with different heat fluxes and different concentrations of lithium bromide solution is conducted.The outcome of falling film evaporation experiments show that the heat transfer coefficient increases with the decrease of inlet concentration of lithium bromide solution and significantly increases with the increase of heat flux.Based on multiple linear regression calculation of experimental data,an experimental correlation of falling film heat transfer coefficient is obtained.A falling film generator of lithium bromide absorption chiller is designed from the correlation,and the immersed generator whose heat load is equal to the falling film generator is designed.The comparison of the two generators on heat transfer coefficient,weight and volume of heat transfer components shows that the falling film generator has great advantages.     

Investigation on flow and heat transfer characteristics in capillary porous wick based on alkali metal thermal-to-electric converter (AMTEC)

An axial symmetric invariable temperature phase change interface model of capillary porous wick based on alkali metal thermal-to-electric converter (AMTEC) is established to simulate flow and heat transfer characteristics in capillary porous wick and liquid channel by solving the mass and heat transport controlling equations. The effects of the working fluid flow rate, inlet temperature, porous wick thickness, porosity and effective pore diameter on the distributions of pressure, velocity and temperature are analyzed. In addition, the available effective pore size of the porous wick and the measures to improve the performance of the porous wick are given by analyzing the relationship between the maximum available capillary pressure and the loop pressure drop. The results show that the model presented in gives a good agreement with the three dimensional two-phase evaporation model. The flow and heat transfer characteristics of the capillary porous wick with the alkali metal liquid as working fluid are different from that with the traditional working fluid in some ways.     

Performance analysis of a concentrating solar hybrid photovoltaic thermal system

The photovoltaic components of a hybrid photovoltaic thermal (PV/T) system are combined with a solar thermal collector, which generates both thermal and electrical energy simultaneously with a higher integrated efficiency. A three dimensional steady model of the concentrating solar PV/T system which has a plate type metallic thermal collector with a serpentine rectangular channel is developed. The processes of photovoltaic and thermal transformation and heat transfer in the PV/T collector are calculated and simulated. The effects of the optical concentrating ratio, coolant mass flow rate, ambient air velocity and glass cover on both thermal and electrical performance of the collector are presented and discussed.     

太阳能制冷机组通风系统中粮库温度的系统分析

针对不同的粮库内部太阳能制冷机组空调分布形式,利用CFD计算软件,采用标准k-e模型对粮库内部的大空间气流组织的非稳定特性进行三维数值模拟,分别比较了集中辐射式分布和沿四壁周向式分布两种形式的粮食表面附近的截平面的速度和温度分布,模拟结果显示:采用集中辐射式分布的模型流场扰动范围大,换热效果好,温度场分布均匀,整体降温效果好.由此可以看出流体计算技术在研究空调换热空间速度场和温度场分布的巨大作用,为空调的设计运行参数提供了重要依据,从而可以选用换热效果更好的空调分布形式.     

苏北地区日光温室能量分配动态研究

为了进一步提高日光温室保温性能,减轻温室内低温寡照灾害发生,以苏北（徐州）番茄日光温室为研究对象,利用采集的2010年12月-2011年4月温室小气候数据及番茄发育数据,根据日光温室小气候形成的物理过程与机理,系统研究了冬春季节不同天气类型及不同叶面积指数对温室能量分配的影响。结果表明：日光温室内潜热、显热随着室内总辐射量的改变而发生变化,阴天以显热消耗为主,潜热消耗量全天低于显热;晴天日光温室内用于作物蒸腾的能量显著多于阴天,阴天室内外贯流传热消耗的能量远远多于晴天;随着叶面积指数增大,到达地面的太阳辐射减少,地面升温慢,室内空气与地表的显热交换量减少,同时室内空气与墙体的显热交换增加。本研究结果可为温室的结构优化及冬春季节日光温室管理提供科学依据。     

A STUDY OF THERMOTECHNICAL CHARACTERISTICS IN FORCED CONVECTION BATCH FURNACE

An experimental study of heat transfer mechanism and characteristics of high velocity circulation combustion gas in a batch heat treatment furnace with high velocity burner was presented. The regular patterns of variation of total heat flux, heat convection and radiation heat fluxes given heating materials with heating time were obtained. It was revealed from the results of experiment and calculation that inverse heat flux of metal radiation is an unavoidable heat transfer characteristic.     

Study on Underground Hot Water Storage Tank Cooling of Solar Energy Heating System

In view of the different of the underground heat storage water tank of solar position arrangement, make use of the Fluent software program numerical simulation and calculation, it is concluded that under different conditions the heat storage water tank temperature field distribution of the soil around. At the same time, establishing physical model and mathematical model of underground heat storage water tank and combined with practical engineering, verify the underground storage tank for heat and energy storage, to obtain the relationship between the tank roof loss and total heat release. Calculation results show that under the same conditions, outdoor storage tank at the top of the heat dissipating capacity to reduce, so the method can be used to offset at the top of the energy required collector to reduce, so the method can be used to offset this part of the energy required collector area of the cut, improve thermal efficiency and reduce the user store hot water tank of the store.     

直接接触式换热器传热性能优化

建立了以容积换热系数为目标函数,工质流率U₀、喷头喷孔直径d_i、导热油液位高度Z为决策变量的直接接触式换热器性能优化模型,同时进一步将液滴群行为与传热协同关系作为约束条件引入优化模型中,重点分析该约束条件对优化过程及结果的影响。运用遗传算法对原模型和补充模型进行了优化分析,结果表明：原模型优化后的容积换热系数达到了初始值的6.7倍;而补充模型最优值的迭代次数比原模型减小了约55%,同时最优值比原模型提高了0.3%。所以该约束条件不仅提高了迭代速率,还提高了寻求全局最优值的概率,使得最优解更逼近全局最优值。