Research on single hole heat transfer power of ground source heat pump system

In this paper,the single hole heat transfer power of the ground source heat pump system in Hengshui is compared with data gained from thermal response test.The results show that maximum monitoring data of heat transfer power per meter in summer is 97.1% of the test data,and the average value accounts for 81.8%.The per meter heat power data through on-site thermal response test can provide references for designing engineering project and optimizing ground source heat pump system as these data do not vary greatly from the actual monitoring data.

RHEOLOGICAL CHARACTERISTICS,POWER CONSUMPTION,MASS AND HEAT,TRANSFER DURING XANTHAN GUM FERMENTATION

Xanthan gum fermentation is probably the most complex fermentation process in terms ofrheological property variations and associated mixing,power consumption,mass and heat transferproblems.In order to obtain these data,fermentations of Xanthomonas campestris were carried outon pilot scale bioreactor with different D/T ratios and different feeding strategies(batch andfed-batch).It was discovered that the rheology of xanthan fermentation broth is of paramountimportance to the above characteristics.The aerated power consumption and power number are both afunction of aeration rate during the initial stage of the fermentation when the viscosity is low andthe Reynolds number high.However when the becames viscous and Reynolds unmber≤10~3,thegas velocity does not show any effect on the power number.The oxygen mass transfer coefficientsand the overall heat transfer coefficients are both dependent on the impeller speed,the apparentviscosity of the broth and the D/T ratio.These data taken from practical

Modelling Study to Compare the Flow and Heat Transfer Characteristics of Low-Power Hydrogen,Nitrogen and Argon Arc-Heated Thrusters

A modelling study is performed to compare the plasma flow and heat transfer characteristics of low-power arc-heated thrusters （arcjets） for three different propellants： hydrogen, nitrogen and argon. The all-speed SIMPLE algorithm is employed to solve the governing equations, which take into account the effects of compressibility, Lorentz force and Joule heating, as well as the temperature- and pressure-dependence of the gas properties. The temperature, velocity and Mach number distributions calculated within the thruster nozzle obtained with different propellant gases are compared for the same thruster structure, dimensions, inlet-gas stagnant pressure and arc currents. The temperature distributions in the solid region of the anode-nozzle wall are also given. It is found that the flow and energy conversion processes in the thruster nozzle show many similar features for all three propellants. For example, the propellant is heated mainly in the near-cathode and constrictor region, with the highest plasma temperature appearing near the cathode tip; the flow transition from the subsonic to supersonic regime occurs within the constrictor region; the highest axial velocity appears inside the nozzle; and most of the input propellant flows towards the thruster exit through the cooler gas region near the anode-nozzle wall. However, since the properties of hydrogen, nitrogen and argon, especially their molecular weights, specific enthMpies and thermal conductivities, are different, there are appreciable differences in arcjet performance. For example, compared to the other two propellants, the hydrogen arcjet thruster shows a higher plasma temperature in the arc region, and higher axial velocity but lower temperature at the thruster exit. Correspondingly, the hydrogen arcjet thruster has the highest specific impulse and arc voltage for the same inlet stagnant pressure and arc current. The predictions of the modelling are compared favourably with available experimental results.

Effect of thermal conductivity on heat transfer for a power-law non-Newtonian fluid over a continuous stretched surface with various injection parameters

The two-dimensional non-Newtonian steady flow on a power-law stretched surface with suction or injection is studied. Thermal conductivity is assumed to vary as a linear function of temperature. The transformed governing equations in the present study are solved numerically using the Runge-Kutta method. Through a comparison, results for a special case of the problem show excellent agreement with those in a previous work. Two cases are considered, one corresponding to a cooled surface temperature and the other to a uniform surface temperature. Numerical results show that the thermal conductivity variation parameter, the injection parameter, and the power-law index have significant influences on the temperature profiles and the Nusselt number.

In-Situ Preparation and Thermal Shock Resistance of Mullite-Cordierite Heat Tube Material for Solar Thermal Power

In order to improve the thermal shock resistance of solar thermal heat transfer tube material, the mullite-cordierite composite ceramic as solar thermal heat transfer tube material were fabricated by pressureless sintering using a-Al203, Suzhou kaolin, talc, and feldspar as starting materials. The important parameter for solar thermal transfer tube such as water absorption （W）, bulk density （Db）, and the mechanical properties were investigated. The phase composition and microstructure of the composite ceramics were analyzed by XRD and SEM. The experimental results show that the B3 sintered at 1 300 ℃ and holding for 3 h has an optimum thermal shock resistance. The bending strength loss rate of B3 is only 2% at 1 100℃ by air quenching-strength test and the sample can endure 30 times thermal shock cycling, and the water absorption, the bulk density and the bending strength are 0.32%, 2.58 g·cm-3, and 125.59 MPa respectively. The XRD analysis indicated that the phase compositions of the sample were mullite, cordierite, corundum, and spinel. The SEM images illustrate that the cordierite is prismatic grain and the mullite is nano rod, showing a good thermal shock resistance for composite ceramics as potential solar thermal power material.

Numerical Research of Heat Transfer of Supercritical COR2R in Channels

With the worldwide development of nuclear power plant and requirement of saving energy and resource, high thermal efficiency and economical competitiveness are achieved by using supercritical COR2R with spe-cial thermal properties and better flow and heat transfer characters. In this paper, heat transfer of supercritical COR2R has been investigated in square and triangle array tube-bundle of cooled system in reactor using com-putational fluid dynamics (CFD) code FLUENT, and the basic knowledge of heat transfer of supercritical COR2R and first experience of CFD simulation are obtained. The effect of mesh structures, turbulence models, as well as flow channel size is analyzed. The choice of turbulence model adopted in simulating supercritical COR2R is recommended. Comparing the effect of heat transfer with supercritical COR2R and supercritical water as cooled medium, the results show that the former was higher. The new idea is provided for choice of cooled medium and improving thermal efficiency this paper.

Heat Transfer Between a Missile's Combustion Chamber and the Warhead

Under higher temperatures the charge within a warhead will be subjected to physical and chemical changes, which will influence the security of the warhead launching process. In this paper the problem is studied adopting finite difference method for the case of a rocket powered missile. Temperature distribution tables are given through quadrature experiments, and the results fit the actual measured values very well. The results also show that to ensure the launching security of rocket powered missiles having warhead charge critical temperature close to about 60?℃, the designer can select appropriate heat insulation structural parameters.

A Compound Cycle for Power Generation by Utilizing Residual Heat of Flue Gas in Electric Steelmaking Process

Electric furnace short process steelmaking is one of the most important steelmaking methods in the world today, and the waste heat recovery potential of electric furnace flue gas is huge.?The research on the recovery of electric furnace flue gas waste heat is of great significance. In order to make better use of this part of the heat,?in this paper, a compound cycle of nitrogen Brayton cycle as a first-order cycle and toluene transcritical Rankine cycle as a second-order cycle is proposed to recover waste heat from furnace flue gas in steelmaking process for power generation. A mathematical model was established with the net output power as the objective function and the initial expansion pressure, the final expansion pressure, the initial expansion temperature and the initial pressure of the second cycle as the independent variables. The effect of multivariate on the net output power of the waste heat power generation cycle is studied, and then, the optimal parameters of the compound cycle are determined. The results show that under the general electric furnace steelmaking process, the power generation efficiency of this new cycle can be increased by 21.02% compared with the conventional cycle.

Research of Inorganic Heat Transfer Element Starting Proprerty

This article studies the wall temperature distribution of inorganic heat transfer element in different working conditions by experiments, and analyzes the impact of inclination angle, heating power, different kinds of cooling medium and different inlet temperature of cooling medium on the starting property of inorganic heat transfer element.

电厂锅炉实验虚拟仿真系统建设与应用

为开展能动专业核心课程“锅炉原理”的实验教学,校企合作开发了电厂锅炉实验虚拟仿真系统。基于两相流动与辐射对流传热原理构建的仿真系统,由风烟和汽水两大模型构成,严格遵守质量、能量、动量守恒方程。变负荷虚拟实验显示,随锅炉负荷增加,热效率降低、燃料耗量增加。根据辐射传热原理,结合火焰平均温度计算发现:只有炉膛出口烟温增加,才能保证炉膛传热负荷增加,继而抬升排烟温度,导致排烟热损失变大、锅炉热效率降低。锅炉原理实验虚拟仿真,可训练学生运用锅炉本体热力计算原理分析问题的思维,是落实创新能力培养的重要举措。

光伏-绿化复合屋面的研究现状与展望

从屋面热湿环境和植被状态、光伏发电效率、水分平衡、能量平衡与热过程模型4个方面对光伏-绿化复合屋面的研究现状进行阐述。结果表明不同气候和空间配置条件下,光伏组件与植被间的相互作用存在动态变化,导致屋面综合性能存在一定的不确定性。最后对光伏-绿化复合屋面工程应用中面临的挑战以及未来的研究方向进行分析和展望,并指出掌握光伏组件与植被之间的相互作用机理是准确预测与优化光伏-绿化复合屋面综合性能的关键。

小倾角对Ω形弯曲热管传热特性的影响

为研究小倾角对Ω形槽道弯曲热管传热特性的影响,搭建了热管传热性能实验台,基于实验对不同小倾角下热管的温度分布、总热阻、当量导热系数和最大输入功率进行分析。结果表明:在相同输入功率下,倾角为0°和倾角为负的热管壁温均匀性优于倾角为正的热管;倾角为正的热管总热阻最大,倾角为0°和倾角为负的热管总热阻相近;热管倾角为0°时的最大输入功率最高。热管安装和应用中易出现重力倾角偏差,研究结果表明,较小倾角会对Ω形槽道弯曲热管的传热性能造成影响。

一种用于设计电加热滚塑工艺的传热计算方法

首先针对一个空模具以及生产4种不同厚度的氢气瓶内胆的电加热滚塑工艺,通过实验分别测量了模具表面和模内的温度、加热时间和耗电量,并据此计算了在这5种情形下的加热效率和放大系数。然后提出了一种用于设计电加热滚塑工艺的计算方法。即在模具的材料和质量、模内粉料的物性和质量、工艺参数确定后,先计算出有效热能,接着根据放大系数初步估算出在加热阶段电热丝需发出的热能,并由此得出满负荷的加热功率和电热丝的长度。然后利用static bed模型通过FLUENT软件仿真计算出加热时间和电热丝实际需发出的热能。以一个中空立方形的塑料制品的电加热滚塑工艺为例说明了该方法的应用步骤,并研究了满负荷的加热功率和模具材料对加热效率、加热时间和电热丝实际需发出的热能的影响。结果表明,加热效率随氢气瓶内胆厚度的增加而下降,加热时间随着满负荷功率的增大而减少的速率变得越来越慢。采用钢制模具的加热时间比采用铝制模具更长,电热丝也需发出更多的热能。

小型压水堆功率控制系统堆芯换热系数不确定性量化研究

为研究堆芯换热系数不确定性对堆芯功率控制系统的影响,以小型压水堆为例,构建堆芯状态空间模型,结合PID控制器,建立堆芯功率控制系统,利用拉丁超立方方法进行参数抽样,开展不同功率水平下堆芯反应性阶跃扰动和堆芯冷却剂进口温度阶跃扰动的仿真,最后采用区间估计Bootstrap方法进行不确定性量化分析。结果表明:40%FP下堆芯换热系数的不确定性对堆芯功率控制系统的影响比100%FP下的更显著,在PID控制器的作用下,堆芯相对功率和冷却剂平均温度的不确定度均在0.1176%以内,堆芯换热系数不确定性对堆芯功率控制系统的影响是可接受的。

大功率充电连接器相变冷却换热特性研究

直流大功率快充技术可显著缩短电动汽车充电时间,缓解充电焦虑,然而在高电压、大电流下,充电连接器的温度短时间内急剧上升,将降低连接器使用寿命且易引发安全问题。为此,提出一种适用于大功率充电连接器的高效相变冷却技术,分别对单相和相变冷却性能进行数值建模分析,研究了冷却液种类、流量、套管厚度等参数对冷却性能的影响规律。结果表明,充电时长为5 min,加载电流为600 A时,采用40℃水单相冷却可将电缆温度降低至69℃,而采用R134a两相相变冷却则可将电缆温度降低至40℃以下。电缆温度随两相冷却液流量增加而降低,随套管厚度增加而增加,套管厚度相较冷却液流量对电缆温度的影响更为显著。

基于概率论的核电传热管安全寿命评估方法研究

核电传热管是核电站热交换系统的重要组成部分,其安全运行对整个核电站的稳定性和可靠性至关重要。基于正态分布求概率的方法提出核电传热管安全寿命概率评估方法,融合传热管的抗拉强度和历史检测记录的失效概率数据,拟合传热管的持久强度与疲劳运行时间的指数关系,实现传热管在不同拉力工作环境下在任意运行时间失效的概率计算,同时建立安全寿命与平均破断寿命的关系,为传热管的维护和更换提供参考依据。

某太阳能热发电项目导热油管道保温厚度优化研究

储热型槽式太阳能热发电项目在集热场中使用导热油管道数量多,因此消耗保温材料量及施工量大,针对导热油管道保温层厚度进行合理优化,可以提高整个项目的经济性。以某储热型槽式太阳能热发电项目导热油管道为例,结合保温材料的相关费用及保温厚度的技术要求等,对管道保温厚度进行合理性优化,从而达到项目的经济性最优。优化后的结果作为项目导热油管道保温层设计变更的有效依据。

从迪拜光热+光伏综合电站项目浅谈温度仪表新应用

迪拜光热+光伏综合电站项目是目前世界上集光能发电之大成,既有光伏发电又集成了光热发电,且光热发电涵盖了目前世界上仅有的2种光热发电形式——槽式、塔式,其是一个成体系的完整光能发电项目,极具代表性。通过对光热发电原理的解读,结合迪拜光热综合电站项目知晓光热发电的测温需求,通过工程案例论述了光热镜场传热介质的测温方案,以及测温技术应用的关键点,对测温技术在光热发电方面的应用有着积极的意义。

光热发电导热油泄漏在线检测方法研究

针对光热发电导热油泄漏检测指标需求,基于MOS气体传感器技术提出了一种光热发电导热油泄漏检测方法,并通过实验验证了该方法的可行性。采用MOS气体传感器,通过气体改变金属氧化物涂层上的电子浓度,建立导热油检测数学模型,针对采集数据的非线性、非平稳特点,分别采用小波变换、快速傅里叶和希尔伯特黄3种降噪算法对MOS传感器输出信号进行降噪处理。实验结果表明:该检测方法在响应时间为8 s时,达到稳定测量值90%、检出限小于20 ppm,且稳定性好,测量精度高,达到了系统的设计要求。

超临界二氧化碳发电循环回热器及预冷器方案论证

回热器及预冷器是超临界二氧化碳布雷顿循环发电中核心换热部件,它们的高效性和经济性对于循环的应用意义重大,为了切实比较回热器及预冷器采用印刷电路板式换热器及管壳式换热器的差异,本文以某工程参数为基础,分别设计了两种换热器的工程方案,并对两种方案的传热性能及经济性进行比较分析。