冰蓄冷系统的控制

部分负荷方案的结果 在部分负荷方案中,同时采用制冷机组和蓄冰罐来满足供冷负荷,而且制冷机组在无供冷负荷时对蓄冰罐进行蓄冰操作。因此,对蓄冰和供冷两个阶段都必须加以分析。 蓄冰罐和制冷机组的容量是按照与采用全负荷方案时同样的负荷值,应用模拟研究的方法来确定的。该模拟计算为一迭代过程,即先选定一个制冷机组的容量值,然后再确定蓄冰罐的最小尺寸。 影响蓄冰罐容量的关键因素是在最小负荷下的供冷率。制冷机组的容量等于为满足蓄冰罐蓄冰所需求的冷量。为了消除蓄冰罐蓄冰过程初始阶段的影响,进行了一次持续三天的模拟研究。 对于每一种负荷分布情况,有可能采用不同的蓄冰罐和制冷机组容量的组合。制冷机组必须具有的最小容量应该满足能在整个12小时夜间时间内,以满负荷运行的方式完成蓄冰过程。如果制冷机容量小于该最小值,则其无法为蓄冰罐提供足够的冷量,蓄冰罐则无法完成第二天的供冷任务。 制冷机组的实际最大容量等于在毫无蓄冷量的情况下,为了满足最大供冷负荷所需要的容量值。这些制冷机组容量的限定值也就限定了所需蓄冰罐的大小。 图3给出了对于16℃的供冷空气出口温度,差异因数值等于0.83的建筑物供冷负荷在不同的蓄冰罐和制冷机组容量情况下的特性。该图中也绘出了制     

直接蓄冰系统蓄冷过程动态模型研究

分析了直接蓄冰系统的动态特性,建立了相应的物理模型,并利用该模型得出了蓄冰半径及蓄冷率随时间的变化规律,模型预测值与实测值吻合较好。该模型可为直接蓄冰系统的设计及优化提供理论依据。     

蓄冰空调的应用与推广

蓄冰空调的应用与推广黄虎南京建筑工程学院一、外国蓄冰空调的发展状况蓄冰空调在夜间电网负荷较低的期间进行制冰蓄冷，在日间电网供电高峰时，就可关闭或关闭一部分制冷机，利用释放夜间所蓄的冷量来满足空调负荷。这项技术早在３０年代曾为减少制冷机容量在美国就有应...     

冰蓄冷空调蓄冰罐特性的研究

本文通过对某大厦冰蓄冷空调系统的运行情况的测试,详细研究和分析了蓄冰罐在不同流量下的蓄冷和释冷特性,在融冰工况时,蓄冰罐进口温度出口温度和释冷量的影响。     

浅析蓄冰空调的发展意义

本文从终端节能优先、年运行费用等角度分析了蓄冰空调发展的巨大意义。蓄冰空调并不节能,但从能源需求侧管理（ＤＳＭ）的角度考虑,其具有终端节能的优点;蓄冰空调可降低诉年运行费用。因而在国家和电力部门的支持下,对蓄冰空调系统运行期采用优化控制的策略,发挥蓄冰空调的优势,真正做到利国利民,从而进一步推动蓄冰技术的发展。     

两相冰蓄冷空调系统的应用分析

两相冰是冰与乙二醇水溶液的混合物，两相冰蓄冷是冰蓄冷的一种有效形式。本文分析了两相冰的传热与阻力特性及其蓄冷空调系统的特点。     

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。     

水平置恒壁温单圆管外蓄冰规律的实验研究

管外蓄冰是静态管壳式蓄冰槽所采用的主要方式，对其特性的理解对于进行相关设备的设计和优化具有重要作用。通过实验研究考察了水在有限空间内水平恒壁温单圆管外的冻结过程，通过测量冰层轮廓的变化，确定出密度反转和自然对流对管外蓄冰过程影响的基本特性，以及管外蓄冰过程的特点。实验结果表明，初始水温的大小影响着管外冰层轮廓发展的均匀性。受对流降温现象的影响，无因次冰层断面积随无因次时间的增长趋势和水温为0℃时的冻结过程有很大差别，所体现的蓄冰规律与初始条件有很大的相关性。在管内盐水温度不变的情况下，初始水温高，输入的冷量主要用于降低水温，所以冰层增长慢；初始水温低时，输入的冷量多用于促进冰层的增长。     

某供电大楼冰蓄冷空调测试的分析与评估

通过实测、调研某供电大楼冰蓄冷空调系统,从技术和优化运行角度对该冰蓄冷空调系统所测数据进行分析,指出该系统中蓄冰槽蓄冷率低、释冷不足的问题,并进行分析。接着论述了冰蓄冷空调系统的蓄冰槽不仅要在蓄冰量上与系统主机容量相匹配,同时还要考虑到蓄冰槽的蓄冰、融冰特性,最后说明系统运行管理人员对冰蓄冷空调系统在节能运行上产生的影响。     

我国自主研发蓄冰空调节能超40%

近日,我国自主研发的首台板式制冰蓄冰空调在京完成测试,比传统蓄冰空调节能40%以上。数据显示,目前北京投入运行的蓄冰空调建筑项目只有70多家,还不到市场份额的5%。     

Performance evaluation of a new ice preservation system for supermarkets

At present, all types of large–medium‐sized supermarkets with aquatic products adopt ice preservation to ensure freshness. The traditional method of ice preservation needs to make a large amount of thick ice and thus wastes manpower and freshwater. A new ice preservation system with cold storage (IP&CS) is designed, and its performance is tested. The use of a cold storage tank to replace the thick ice laid achieves a repeated cold storage and discharge. This experiment uses NaCl solution as the cold storage phase change material (PCM). The phase change temperature of the cold storage PCM and the optimum temperature of the secondary refrigerant during the cold storage process are determined. Results show that the center temperature of aquatic products, water loss rate, color of aquatic products, power consumption, and electricity cost of the IP&CS system are better than those of the traditional ice preservation system.     

Freezing and melting of water in spherical enclosures of the type used in thermal (ice) storage systems

This paper describes and evaluates the results of an experimental study aimed at the characterisation of the freezing and melting processes for water contained in spherical elements of the type often found in the beds of thermal (ice) storage systems used building air conditioning systems. The results include semi-empirical equations that allow the mass of ice within a sphere to be predicted at any time during the freezing or melting processes. It is believed that these equations will be useful in modelling the dynamic behaviour of thermal (ice) storage using spherical elements as phase change. The apparatus, method and results are described. A novel method which was used to measure the water–ice interface position during the freezing process is also described. Several interesting results were obtained from this study.     

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.     

高温熔融盐纳米固液相变复合材料研究进展

熔融盐是一种非常有前景的高温液体传热蓄热工质,在太阳能热发电、余热回收及工业热利用方面有显著的优势,但是熔融盐本身存在导热性能不高等问题。本文对纳米复合相变材料固液相变储能过程的若干最新研究进行了回顾,综述了熔融盐纳米固液相变复合材料国内外研究现状及发展趋势,最后对纳米复合相变材料固液相变储能过程的未来发展和重点研究方向进行了展望,认为主要解决纳米复合材料内熔化相变传热双温度模型的建立及求解、NC-PCM的制备工艺、金属纳米粒子的团聚性及NC-PCM蓄热器的热循环实验等方面的问题是未来研究的重点。     

Numerical Analysis of Phase Change Material Characteristics Used in a Thermal Energy Storage Device

In this study, a numerical analysis is performed to investigate the freezing process of phase change materials (PCM) in a predesigned thermal energy storage (TES) device. This TES device is integrated with a milk storage cooling cycle operating under predefined practical conditions. Using this cooling unit, 100 litres of milk is kept cool at 4°C for 48 hours before it is collected. A 2-D model of the TES device is developed in COMSOL Multiphysics to analyze the phase change performance of water-based PCMs. The variations of thermal properties with temperature during the phase change are considered in the analysis. The model is used for exploring the solidification process of PCMs inside the TES device. Temperature variations with time, ice formation, and the impacts of boundary conditions are investigated in detail. Water PCM shows better characteristics in the solidification process in comparison to eutectic PCMs, which is mainly due to the differences between phase change temperatures of the PCMs.     

Entropy generation minimization for charging and discharging processes in a gas-hydrate cool storage system

Thermodynamic optimization models of gas-hydrate cool storage and cool release processes are established in this paper. The optimal temperature configuration at the sensible heat transfer stage and the optimal gas hydrate phase change rate configuration at the phase change stage in the processes of gas hydrate charging and discharging are obtained by taking entropy generation minimization as optimization objective. The optimal control strategies of the cool storage system are determined. The research results indicate that the optimal operating characteristic of the gas-hydrate cool storage system can be achieved by keeping the phase change rates uniform, which are regulated and controlled according to constant heat transfer rates in the charging and discharging processes of gas hydrate. The analysis method and the results presented in this paper can provide important guidelines for optimal design and operation of gas-hydrate cool storage system.     

Heat transfer enhancement in water when used as PCM in thermal energy storage

Efficient and reliable storage systems for thermal energy are an important requirement in many applications where heat demand and supply or availability do not coincide. Heat and cold stores can basically be divided in two groups. In sensible heat stores the temperature of the storage material is increased significantly. Latent heat stores, on the contrary, use a storage material that undergoes a phase change (PCM) and a small temperature rise is sufficient to store heat or cold. The major advantages of the phase change stores are their large heat storage capacity and their isothermal behavior during the charging and discharging process. However, while unloading a latent heat storage, the solid–liquid interface moves away from the heat transfer surface and the heat flux decreases due to the increasing thermal resistance of the growing layer of the molten/solidified medium. This effect can be reduced using techniques to increase heat transfer. In this paper, three methods to enhance the heat transfer in a cold storage working with water/ice as PCM are compared: addition of stainless steel pieces, copper pieces (both have been proposed before) and a new PCM-graphite composite material. The PCM-graphite composite material showed an increase in heat flux bigger than with any of the other techniques.     

Experimental and numerical study on charging processes of an ice‐on‐coil thermal energy storage system

In this study, an external melt ice‐on‐coil thermal storage was studied and tested over various inlet conditions of secondary fluid—glycol solution—flow rate and temperature in charging process. Experiments were conducted to investigate the effect of inlet conditions of secondary fluid and validate the numerical model predictions on ice‐on‐coil thermal energy storage system. The total thermal storage energy and the heat transfer rate in the system were investigated in the range of 10 l min ^?1?V??60 l min ^?1. A new numerical model based on temperature transforming method for phase change material (PCM) described by Faghri was developed to solve the problem of the system consisting of governing equations for the heat transfer fluid, pipe wall and PCM. Numerical simulations were performed to investigate the effect of working conditions of secondary fluid and these were compared with the experimental results. The numerical results verified with experimental investigation show that the stored energy rises with increasing flow rate a decreasing tendency. It is also observed that the inlet temperature of the fluid has more influence on energy storage quantity than flow rate. Copyright © 2006 John Wiley & Sons, Ltd.     

Simulation modeling and analysis of a high temperature phase change heat storage and exchange device

相变储热因单位体积储热量大,储热和放热过程温度基本恒定等优点而成为目前研究的热点。相变过程中涉及固液两相间融化和凝固的传热问题,其储放热过程是一个复杂的非稳态相变过程。本文对高温相变储热换热装置进行换热特性研究,通过研究储热单元的换热特性,基于FLUENT软件,结合装置的设计参数和相变复合材料的物性参数,对相变储热系统储/放热过程中内部的温度分布、传热速率和储放热效率进行了数学建模及模拟分析,重点研究了不同传热流体速度对单元储/放热性能的影响规律。根据仿真结果,在相变储热装置的设计中,可选择合适的空气流速,以实现不同的散热功率及储放热时间,满足不同用户的用热需求。物理实验表明仿真结果偏差较小,可为高温相变储换热装置设计、优化等工作提供依据。     

纳米复合相变材料固液相变储能过程研究进展

对纳米复合相变材料固液相变储能过程的若干最新研究进行了回顾,从相变储能系统的动态性能和典型的凝固、熔化传热过程两方面总结了相关研究的进展,并重点评述了数值模拟研究中纳米复合相变材料有效热物性预测方法的适用性及其与实验结果之间的偏差,最后对纳米复合相变材料固液相变储能过程的未来发展和重点研究方向进行了展望。