冷链蓄冷保温箱性能优化数值模拟研究

为缩短充冷时间,提高保冷能力,降低能耗,实现蓄冷保温箱性能的提升。提出一种锯齿形结构新型蓄冷板,并对比了平板蓄冷板与三种不同尺寸新型蓄冷板的蓄释冷性能。同时研究了蓄冷保温箱配送过程中,四种蓄冷板布置方式(顶部布置、四周布置、并列布置、重合布置)下箱体的保冷性能。结果表明:新型蓄冷板与平板蓄冷板相比蓄释冷更快,其中新型蓄冷板3性能最高,其蓄释冷完成时间与平板蓄冷板相比分别缩短了39.1%与39.3%;蓄冷板布置方式对箱体保冷性能存在很大的影响,其中并列摆放时温度场均匀,且平均温度最低,只有281.6 K,效果最好。     

盘管式蓄冷装置蓄冰过程的模拟研究

本文对盘管式蓄冷装置的蓄冷过程建立了集总参数的数学物理模型,并进行了理论计算.分析了该系统的换热效果,讨论了某些参数的变化对蓄冷器换热特性的影响.计算结果对该类换热器的设计和性能优化有一定指导作用.     

低温蓄冷节能技术在冻结法施工中的应用分析

随着能源的日益紧缺以及城市的发展,深厚表土层复杂地质条件的煤层开发及城市地下工程的建设,已经被提上日程。而作为特殊的地下工程建设,冻结法无疑是最好的选择之一,但其耗电量大,施工费用高的问题又限制了其广泛应用。据此,介绍了冻结法发展现状,并对蓄冷节能技术在冻结法施工中的应用前景和可行性进行了综合分析,提出了需要解决的技术难题,最后以一工程实例进行了经济技术分析。     

高温肋板式蓄热器蓄/放热特性的数值模拟

采用计算流体动力学方法对高温不锈钢肋板式相变蓄热器的蓄/放热特性进行了数值模拟。分析了多孔肋片和锯齿肋片对蓄热器蓄/放热特性的影响以及载热体入口温度和流量对相变材料熔化和凝固速度的影响,计算结果表明:在该新型肋板式相变蓄热器中,多孔翅片的性能优于锯齿肋片;随着蓄热器传热温差的增大和载热体流量的增加,蓄热器的蓄/放热性能越好;肋片作为换热元件可以很好的提高蓄热器的蓄/放热性能。所得结论可为高温肋板式蓄热器的优化设计提供有益的参考。     

机械式搅拌锌浸出槽内流场和停留时间的数值模拟

采用标准的k-ε湍流模型、多重参考系稳态流动方法,对锌浸出槽内流动过程进行了数值模拟研究,并且采用示踪剂法,研究了流体在槽内停留时间的分布。模拟结果表明:浸出槽无阻尼板时槽内流体主要以周向流动为主,桨叶承受的压力较大,流体在槽内有局部"短路"现象出现。增加阻尼板后,流体在槽内由原来的周向流动为主转变为轴向流动为主,加速了槽内矿浆的混合,桨叶承受的压力明显降低,其最大压力降低15%,平均压力降低57%,流体在槽内停留时间分布与无阻尼板基本相同,但平均停留时间略有增大,有利于浸出过程的进行。     

户式冰蓄冷空调的应用及经济分析

文章对户式冰蓄冷空调的应用和运行特点作了综合性的论述；按照江苏现行的峰谷时段和电价政策对户式冰蓄冷空调和常规家用空调作了峰谷耗电量和电费的分析比较，得出户式冰蓄冷空调的移峰填谷作用是明显的，但是按照目前的峰谷电价比采用冰蓄冷空调并不经济。只有当峰谷电价比达到一定值以上时，采用冰蓄冷空调才具有良好的经济效益。     

不完全冻结式冰盘管融冰过程中环水温度的变化特性

通过不完全冻结式冰盘管融冰过程的实验研究，分析了水平排列管束外环水温度的变化特性，得出了融冰后期环水升温的过程存在一个升温平台的结论，进而研究了不同初始蓄冰量等因素对环水温度变化特性的影响。     

蓄冷球在流场中凝固过程的数值模拟

通过CFD软件模拟了单个共晶盐蓄冷球在蓄冷槽中的凝固过程.在整个充冷过程中蓄冷球表面与外围载冷剂流场换热直至完全凝固.模拟中发现,由于整个流场的流速较低,蓄冷球凝固初始阶段球表面的自然对流对流场的影响不可忽视,同样也影响球体本身的热通量.模拟结果表明蓄冷球在负向流动流场中所需的凝固时间小于正向的凝固时间.     

内融冰式蓄冷实验台的设计

本文设计了内融冰式冰蓄冷实验台,介绍了该实验台的结构及构成,提出制冰和融冰过程的实验步骤,说明其测量方法。     

冻结条件下土壤水热耦合迁移的数值模拟

以沈阳市季节性冻土为例,基于冻结条件下水热耦合迁移的数学模型,采用中心差分格式并用线性化迭代法求解,对现场土壤冻结过程进行了模拟.与实测结果对比表明,采用的参数及数学模型可成功模拟现场土壤冻结过程,并讨论了土壤冻结时水分与温度的迁移规律,可为后续研究奠定基础.     

Numerical investigation of thermal performance of geometrically modified spherical ice capsules during the discharging period

Ice thermal energy storage (ITES) is a significant option for shifting cooling load from peak hours to off‐peak hours in order to reduce the cooling cost and equipment capacity. Encapsulated ITES system is one of the most preferred types of ITES systems, because it is easier to apply and has lower initial cost than other types of ITES systems. Capsule geometries have great impact on the thermal performance of the encapsulated ITES system. Spherical capsules are widely used in the application because they provide better thermal performance due to the ratio of its volume to its surface area. Also, modified capsule geometries are used for increasing the thermal performance of the ITES system. This paper focuses on a numerical study in order to determine the effect of the geometrically modified spherical capsule on the thermal performance during the discharging period. Seven geometrically modified spherical capsules were investigated and compared with the ordinary spherical capsule. The FLUENT 17.1 code was used for numerical analyses. At the end of the study, it was found that geometrically modified capsules provided higher thermal performance than an ordinary spherical capsule in the equal capsule volume. Capsule D provided the longest discharging period of 2118 seconds, when V_{HTF, in} = 0.001 m/s and T_HTF,in = 275.5 K. The lowest discharging time of 464 seconds was obtained with Capsule A, when V_{HTF, in} = 0.01 m/s and T_{HTF, in} = 283 K. Among the studied modified capsules, Capsule F performed the worst thermal performance. Energy efficiency values were high, and they did not give comparable difference between the capsule models and working conditions. While all exergy values were 98.50% and higher, exergy efficiency values changed between 85.12% and 51.91%. Exergetically, Capsule D provided the best thermal performance during the discharging period.     

Experiments on charging and discharging of spherical thermal (ice) storage elements

This paper is concerned with an experimental investigation into the dynamic behaviour of single spherical thermal (ice) storage elements. Three glass spheres having radii of 4.07, 3.5 and 3.135 cm were chosen for this study. A flowing water–glycol solution over a range of temperature varying between 4.5 and 12°C (during melting) and between ?9.5 and ?4.4°C (during freezing) was used as a heat transfer fluid (HTF) during the tests. The apparatus, method and results are described. Photographic means were used to characterize the water–ice interface position and its shape during discharging (melting) process. However, during charging (freezing) process a new method was devised for the same objectives. Several interesting results have been obtained from this study. Results obtained showed that the charging and discharging rates were constant with respect to the dimensionless time to at least 90% of the storage capacity of the single spherical ice storage element. These important and new results have allowed the formulation, described in the paper, of simple empirical equations describing the charging and discharging rates for a single spherical thermal (ice) storage element at any instant time period within the range of HTF temperature and spherical element size used. It is believed that these equations will be useful to colleagues interested in modelling the dynamic behaviour of thermal (ice) storage using spherical elements as phase change. Effects of the HTF temperature and capsule size on the rate of energy charged and discharged from a single spherical enclosure are presented and discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

热管蓄冰过程的数值模拟研究．

通过建立热管的简化热阻模型,采用数值计算的方法模拟了热管的动态蓄冰。模拟结果与实验结果吻合。同时,对热管冷凝段和蒸发段的长度比为1：2和1：4两种形式进行了数值模拟比较。结果表明,1：4的布置形式更优。     

浅析水工建筑物混凝土的碳化、冻融破坏及防治

通过对混凝土的碳化、冻融破坏机理及影响因素分析 ,提出了水工建筑物混凝土碳化、冻融破坏的防治措施 ,原则上应为防重于治 ,以达到或延长工程的使用寿命。     

Numerical analysis of the discharging performance of a solar energy storage tank containing PCM modules

采用数值模拟软件FLUENT对含有相变储能模块的储热水箱(下文简称为相变储能水箱)和不含相变储能模块的普通水箱(直接进水)的释能工况进行数值模拟,并将模拟结果进行了对比.数值模拟结果表明水箱加入相变储能模块后,一方面相变储能模块的堆积起到了散流作用,减缓了进口水流造成的扰动;另一方面冷水进入水箱中通过相变储能模块缝隙时,相变储能模块对冷水有一定的加热作用.加入相变储能模块后,改善了释能过程的水箱内热分层效果,提高了储热水箱的释热总量.在流量为5 L/min时,相变储能水箱的释能效率比普通水箱的释能效率高7%,但是随着流量的增大,相变储能水箱的释能效率逐渐降低.     

Numerical simulation of three-dimensional flow dynamics in a hot water storage tank

A hot water storage device is one of the most common household appliances yet it is also one of the biggest sources of energy consumption. With natural resources fading, it is imperative that typical high-energy users such as hot water systems are made as energy efficient as possible. Research has shown that the thermal performance of a hot water system can be increased by maximising the level of thermal stratification within the storage tank, which could lead to huge energy saving. To analyse the effects of tank geometry and operating conditions on the thermal stratification within a storage tank, seven three-dimensional models have been numerically simulated by using the computational fluid dynamics program Fluent with realistic boundary and initial conditions applied. The level of thermal stratification in each model has been quantified using exergy analyses. The results show that increasing the tanks height/diameter aspect ratio, decreasing inlet/outlet flow rates and moving the inlet/outlet to the outer extremities of the tank all result in increasing levels of thermal stratification.     

冻结融解作用对岩石边坡稳定的影响

主要通过岩石室内试验,分析子了冻结融解作用对岩石物理力学性质的影响以及岩石裂缝发展的规律,同时结合边坡的破坏事例调查成果,结论认为表层崩塌的破坏模式是岩石边坡长期冻结融解作用的主要表现形式。     

两种结冰方式影响蓄冷速率的数值分析

环状结冰和形成均匀冰水混合物成核相变结冰是冰蓄冷空调水结冰过程的两种主要方式。由于完全冻结时间是影响冰蓄冷空调的主要因素之一，因此，为了研究这两种结冰方式所需要完全冻结时间的差别．对蓄冰球内水的环状结冰方式和形成均匀冰水混合物成核相变结冰方式建立了理论模型，并对两种方式的完全冻结时间进行了数值计算，其计算结果与实验结果基本一致。结果表明，环状结冰方式要比均匀冰水混合物成核相变结冰方式的完全冻结时间长很多，所以后者是冰蓄冷空调工程中理想的结冰方式。     

蓄冰空调系统在办公类建筑中的经济性分析

针对蓄冰空调系统的工程应用,阐述系统工作原理及其适用性分析,选取河北省某办公建筑作为研究对象,按照此建筑用能特点以及当地电价结构,选择了100%、80%、60%、40%、20%五档部分负荷率对蓄冰空调系统与传统空调系统进行全年运行能耗及电费对比,分析结果表明:虽然蓄冰空调系统初投资偏高,但其年运行费用比传统空调系统节省电费32.4%,寿命期内年费用节省20.43%。