Experimental study on the heat transfer and flow characteristics of nanorefrigerants inside a corrugated tube

The heat transfer and flow characteristics of MWCNT-R141b nanorefrigerant with different mass fractions have been studied through experiments. Experimental results were compared with existing correlations. A two-step method was used to prepare the nanorefrigerants. Span-80 was used as surfactant with an average particle diameter of 20 nm. Transmittance method was used to evaluate the stability of nanorefrigerants. Results showed that the stability of MWCNT-R141b nanorefrigerant, which is the added dispersant, was good during the experiments. The 0.3 wt% MWCNT-R141b nanorefrigerants had optimal heat transfer enhancement effects compared with pure refrigerants. The maximum Nusselt number increased by 40%. The specific pressure drop of nanorefrigerant increased as the Reynolds number (Re) increased, and the specific pressure drop of the pure refrigerant was minimum, which is similar to R141b.     

Numerical study of thermal-hydraulic and dust-deposition of tube bundles in an intermediate heat exchanger

Very-high-temperature gas-cooled reactors (VHTRs) are promising for efficient, zero-carbon hydrogen production. The intermediate heat exchanger (IHX) is a key piece of equipment for VHTR-coupled hydrogen production. Constrained by the limited space within the VHTR, the IHX must be efficient and compact. Besides, radioactive graphite dust deposition will reduce the performance and reliability of IHXs. Therefore, understanding the thermal-hydraulic and dust-deposition characteristics of IHX tube bundles is crucial for the design and safe operation of IHXs. This study uses the unsteady k-kl-ω model to simulate flow and heat transfer in IHX tube bundles. The discrete particle model combined with a deposition model is used to predict the movement and deposition behavior of graphite dust. The deposition model is achieved using user-defined functions. The model and code are first validated by empirical correlations and experimental results. The transient flow fields show that, in the in-line arrangement, unsteady and asymmetric periodic flow occurs with a period of about 0.047 s. The flow is steadier and more symmetric in the staggered arrangement due to the restriction of the main flow to the separation vortices. The maximum circumferential heat-transfer coefficient for inner tubes occurs at the impact point, where the central angle θ is about 60° and 0° for the in-line and staggered arrangement, respectively. The graphite-dust deposition rate decreases with increasing Reynolds number and particle size and the deposition mechanism is also analyzed in detail. With the current design conditions, the Nusselt number of the staggered arrangement increases by 27.90%–29.17% compared with the in-line arrangement, and the deposition rate decreases by 1.52%–3.15%. Furthermore, new correlations for Nusselt number and friction factor are developed for the thermal-hydraulic design of IHX tube bundles.     

煤矿用聚氯乙烯管材环保性能的分析

目前，煤矿用聚氯乙烯（以下简称PVC）管材主要用于煤矿井下供排水、通风、抽放瓦斯和喷浆等，与金属管材相比，它具有以下优点：（1）密度小，仅为铁的1/8，重量轻，易于井下搬运。     

管磨机与球破机粉碎机理研究

本文由管磨机与球破机相关行业及其研究背景入手，说明课题的巨大研究价值。围绕水泥成品优质高产低消耗的目标，从管磨机与球破机料球截面筛析理论入手，揭示了管磨机与球破机的粉碎机理。由管磨机与球破机的机理比较引出了球破机与球磨机串联粉磨工艺理论，阐明了球破机作为新型破碎机械对水泥粉磨工艺的影响，必将对利用管磨机与球破机进行破碎粉磨的相关行业技术进步带来积极影响。     

盘式钻头齿面强化试验

用球状烧结碳化钨取代粒状铸造碳化钨 ,加入一定量的自熔性合金 ,自制薄管焊条 ,分析了焊条的组成、性能和耐磨性。并对盘式钻头进行齿面强化试验。研究表明 ,自制薄管焊条流动性好 ,焊件耐磨性高 ;盘式钻头齿面强化后 ,台架试验证明钻井效果明显     

Fluid filling of a membrane tube with self-weight

The filling of a membrane tube with self-weight by a fluid is studied theoretically for the first time. The fundamental problem depends on two non-dimensional parameters, $\beta$ and $\gamma$ which represent the importance of internal pressure and membrane self-weight respectively. The nonlinear equations are solved by an efficient numerical integration method. It is found that membrane self-weight has considerable effect on the tube geometry and the tension of the membrane at low filling pressures.     

逆作法施工技术浅析

逆作法施工技术是深基础高层建筑施工的有效方法。它主要特点是可节约工期，最大限度地减少工程基础施工对相邻建筑物的影响。本文简要介绍厦门九州大厦地下室逆作法施工方法以及为适应逆作法施工的结构构造处理措施。     

翅片管的传热分析及其表面几何参数的优化

对翅片管的强化传热过程进行了分析。建立了以单位传热量下翅片管的体积最小为目标函数的最优化薮学模型，并对翅片管的最佳表面几何参数(翅片高度、翅片节距、翅片厚度)进行了分析，这些研究对翅片管的应用具有一定指导作用。     

管状交通空间--一种建筑空间组织的原型

抓住建筑中人的运动流线，运用原型理论对建筑空间组织的规律进行研究，试图从错综复杂的空间组织形式中归纳出建筑空间组合的原型——“管状交通空间”，并探讨它在建筑设计中的作用。     

浅层软黏土注浆加固方法研究

注浆一直是处理不良地质的有效方法,取得了良好的治理效果。针对浅层软黏土注浆管路难以固定;注浆压力上不去,很难劈裂黏土体,导致浆液进不到黏土中的特殊性,提出了一种模袋袖阀管相结合的注浆工艺,利用水泥基速凝材料凝结固化时间较长的特点,研究针对浆液可泵性,调节速凝材料与水泥浆配比,控制注浆压力的注浆方法,制定浅层软黏土注浆加固方案。研究结果应用于南京上元门车站基坑涌水注浆堵水工程,解决了浅层软黏土体涌水问题,实现了围岩稳定性控制。研究成果具有一定的理论和实践意义,对类似工程具有参考价值。