新型相变贮热材料

在太阳能热利用、工业余热回收、采暖及空调领域中 ,为了调整热能供应与人们需求之间的不一致 ,热能的贮存是极为关键的一环。目前普遍使用的贮热方式有两大类 :显热式贮热和潜热式贮热。所谓显热式贮热 ,就是通过加热介质 ,使其温度升高而贮热 ,它也叫“热容式贮热”。潜热式贮热是利用贮热介质被加热到相变温度时吸收大量相变热而贮热 ,它也叫“相变式”贮热。物质由固态转变为液态（熔解） ,由液态转变为气态（气化） ,或由固态直接转变为气态（升华） ,都会吸收相变热 ;而进行逆过程时则释放相变热。这是潜热式贮热所依据的基本原理 ,在…     

利用单水浴法测量相变贮热材料及其构件的贮热能力

发展了一种用于测量相变贮热材料及其构件贮热能力的单水浴法。这种方法使用一个其中盛有一定量水的恒温水浴，将水温从T1均匀加热到T2,利用热流片测出通过水浴各壁面的热损，用消耗的电能扣除热损后即得到加热水所消耗的电能Qw；之后将待测相变材料或其构件浸没在水中，将水浴温度调到T1,并从该温度均匀加热到T2，同时利用热流片测出通过水浴各壁面的热损，消耗的总电能扣除相应的热损后即得加热水和相变材料或其构件所消耗的电能Qw＋pom;Qw＋pom减去Qw即为相奕材料或其构件从温度T1升高到T2所吸收的热能，即相变材料或其构件在温度区间[T1，T2]上的贮热能力。利用该方法对一种定形相变材料的贮热能力的测试结果与DSC分析的结果相差不到2％，还利用该方法对颗粒状定形相变材料与混凝土共混成型的贮热构件的贮热能力进行了测试。     

不锈钢太阳能贮热水箱的缝隙腐蚀

该文通过对不同地区使用中的不锈钢太阳能贮热水箱选取解剖，进行宏、微观检验，研究探索了常年处于含氯离子的水介质中的不锈钢热水箱最常见的腐蚀类型及规律。试验证明，在水中有高浓度氯离子的地区，304不锈钢贮热水箱最主要的腐蚀形式为缝隙腐蚀（或点腐蚀）一类电化学腐蚀，因腐蚀速度较快，对水箱的使用寿命威胁较大。选用抗点蚀能力更强的含Mo不锈钢并避免采用有缝隙的焊接接头形式将会有效地提高贮热水箱的使用寿命。     

风力致热系统中贮热装置性能的实验研究

介绍了贮热装置的主要相变材料（５２＃精石蜡）和主要传热元件（重力式热管），讨论了这种贮热装置总贮热量和换热能力的实验测试，探讨了贮热室相变材料的温度对贮热效率的影响。     

太阳能固—固相变贮热

本文评述了作为新型太阳能贮热材料的多元醇类（ＰＥ、ＰＧ、ＮＰＧ）及其二元体系的固－固相变贮热性能的研究情况。     

太阳池水合盐相变贮热的探讨

太阳池水合盐相变贮热能形成梯度层，既显热贮热又相变贮热，具有跨季大容量单一体系热贮存的特点，全年热循环仅３－５次。可以采用溶解盐粒子等办法使相变材料贮热能力再生，讨论了几种水合盐的相律和溶解度，为选择适用于太阳池的相变材料提供参考。     

管内流体流动管外PCM发生相变的贮能系统热性能研究

建立了分析空调贮能系统中管内流体流动管外PCM发生相变的相变的贮能器热性能的数学模型，并进行了数值计算。其中，把传热流体看作是沿轴向的—维无粘流动，对PCM相变过程的求解用显热容法。计算结果与文献中的计算结果吻合较好。所得结论对该类贮能系统的设计和性能优化有一定指导作用。     

聚光太阳灶用金属相变贮能装置的研究

研究了聚光太阳灶用高温金属相变贮能装置。贮能材料为铝基或锌基合金。当太阳辐射强度为1.3kW/m~2时,在面积为2m~2的聚光灶上该贮能装置可加热到650℃—700℃,贮能装置可将4kg水煮沸。     

净化贮氢器

净化贮氢器是利用贮氢材料同时纯化和贮存氢气的装置，器体采用铝合金。原料氢纯度≥９９．０％，充入压力２．０ＭＰａ，吸氢２ｈ时，可连续释放高纯氢１８００Ｌ以上，不加热室温下工作压力０．５ＭＰａ，流量＞１０００ｃｍ＾３／ｍｉｎ可连续使用。文内介绍了吸放氢原理，工艺流程，试验方法，技术规格。     

脂肪酸二元体系相变贮热性能的研究

用差示扫描量热法研究了月桂酸－棕酸和月桂酸－硬脂酸两个二元体系的固－液相变,发现它们都具有良好的贮热性能,因而是一类有前途的相变贮热材料。     

Experimental investigation on a combined sensible and latent heat storage system integrated with constant/varying (solar) heat sources

The objective of the present work is to investigate experimentally the thermal behavior of a packed bed of combined sensible and latent heat thermal energy storage (TES) unit. A TES unit is designed, constructed and integrated with constant temperature bath/solar collector to study the performance of the storage unit. The TES unit contains paraffin as phase change material (PCM) filled in spherical capsules, which are packed in an insulated cylindrical storage tank. The water used as heat transfer fluid (HTF) to transfer heat from the constant temperature bath/solar collector to the TES tank also acts as sensible heat storage (SHS) material. Charging experiments are carried out at constant and varying (solar energy) inlet fluid temperatures to examine the effects of inlet fluid temperature and flow rate of HTF on the performance of the storage unit. Discharging experiments are carried out by both continuous and batchwise processes to recover the stored heat. The significance of time wise variation of HTF and PCM temperatures during charging and discharging processes is discussed in detail and the performance parameters such as instantaneous heat stored and cumulative heat stored are also studied. The performance of the present system is compared with that of the conventional SHS system. It is found from the discharging experiments that the combined storage system employing batchwise discharging of hot water from the TES tank is best suited for applications where the requirement is intermittent.     

Numerical simulation of underground seasonal cold energy storage for a 10 MW solar thermal power plant in north-western China using TRNSYS

This paper aims to explore an efficient, cost-effective, and water-saving seasonal cold energy storage technique based on borehole heat exchangers to cool the condenser water in a 10 MW solar thermal power plant. The proposed seasonal cooling mechanism is designed for the areas under typical weather conditions to utilize the low ambient temperature during the winter season and to store cold energy. The main objective of this paper is to utilize the storage unit in the peak summer months to cool the condenser water and to replace the dry cooling system. Using the simulation platform transient system simulation program (TRNSYS), the borehole thermal energy storage (BTES) system model has been developed and the dynamic capacity of the system in the charging and discharging mode of cold energy for one-year operation is studied. The typical meteorological year (TMY) data of Dunhuang, Gansu province, in north-western China, is utilized to determine the lowest ambient temperature and operation time of the system to store cold energy. The proposed seasonal cooling system is capable of enhancing the efficiency of a solar thermal power plant up to 1.54% and 2.74% in comparison with the water-cooled condenser system and air-cooled condenser system respectively. The techno-economic assessment of the proposed technique also supports its integration with the condenser unit in the solar thermal power plant. This technique has also a great potential to save the water in desert areas.     

Experimental and numerical investigation on solar parabolic trough collector integrated with thermal energy storage unit

Solar parabolic trough collector (PTC) is the best recognized and commercial‐industrial‐scale, high temperature generation technology available today, and studies to assess its performance will add further impetus in improving these systems. The present work deals with numerical and experimental investigations to study the performance of a small‐scale solar PTC integrated with thermal energy storage system. Aperture area of PTC is 7.5 m², and capacity of thermal energy storage is 60 L. Paraffin has been used as phase change material and water as heat transfer fluid, which also acts as sensible heat storage medium. Experiments have been carried out to investigate the effect of mass flow rate on useful heat gain, thermal efficiency and energy collected/stored. A numerical model has been developed for the receiver/heat collecting element (HCE) based on one dimensional heat transfer equations to study temperature distribution, heat fluxes and thermal losses. Partial differential equations (PDE) obtained from mass and energy balance across HCE are discretized for transient conditions and solved for real time solar flux density values and other physical conditions of the present system. Convective and radiative heat transfers occurring in the HCE are also accounted in this study. Performance parameters obtained from this model are compared with experimental results, and it is found that agreement is good within 10% deviations. These deviations could be due to variations in incident solar radiation fed as input to the numerical model. System thermal efficiency is mainly influenced by heat gain and solar flux density whereas thermal loss is significantly influenced by concentrated solar radiation, receiver tube temperature and heat gained by heat transfer fluid. Copyright © 2016 John Wiley & Sons, Ltd.     

High temperature latent heat thermal energy storage using heat pipes

A thermal network model is developed and used to analyze heat transfer in a high temperature latent heat thermal energy storage unit for solar thermal electricity generation. Specifically, the benefits of inserting multiple heat pipes between a heat transfer fluid and a phase change material (PCM) are of interest. Two storage configurations are considered; one with PCM surrounding a tube that conveys the heat transfer fluid, and the second with the PCM contained within a tube over which the heat transfer fluid flows. Both melting and solidification are simulated. It is demonstrated that adding heat pipes enhances thermal performance, which is quantified in terms of dimensionless heat pipe effectiveness.     

Negative buoyant plume model for solar domestic hot water tank systems incorporating a vertical inlet

Thermal stratification in solar energy storage tanks plays an important role in enhancing the performance of solar domestic hot water systems. The mixing that occurs when hot fluid from the solar collector enters the top of the tank is detrimental to the stratification. Mathematical models that are used for system analysis must therefore be able to capture the effects of this inlet jet mixing in order to accurately predict system performance. This paper presents a computational study of the heat transfer and fluid flow in a thermal storage tank of a solar domestic hot water system with a vertical inlet under negative buoyant plume conditions. The effects of parameters such as the fluid inlet velocity and temperature as well as inlet pipe diameter on the thermal mixing were considered. The work culminated in the development of a one-dimensional empirical model capable of predicting the transient axial temperature distribution inside the thermal storage tank. Predictions from the new model were in good agreement with both experimental data and detailed computational fluid dynamics predictions.     

Heat Transfer Enhancement for PCM Thermal Energy Storage in Triplex Tube Heat Exchanger

Thermal energy storage is critical for reducing the discrepancy between energy supply and energy demand, as well as for improving the efficiency of solar thermal energy systems. Among the different types of thermal energy storage, phase-change materials (PCM) thermal energy storage has gained significant attention recently because of its high energy density per unit mass/volume at nearly constant temperature. This study experimentally investigates the using of a triplex tube heat exchanger (TTHX) with PCM in the middle tube as the thermal energy storage to power a liquid desiccant air-conditioning system. Four longitudinal fins were welded to each of the inner and middle tubes as a heat transfer enhancement in the TTHX to improve the thermal performance of the thermal energy storage. The average temperature of the PCM during the melting process in the TTHX with and without fins was compared. The PCM temperature gradients in the angular direction were analyzed to study the effect of the natural convection in the melting process of the thermal storage. The energy storage efficiency of the TTHX was determined. Results indicated that there was a considerable enhancement in the melting rate by using fins in the TTHX thermal storage. The PCM melting time is reduced to 86% by increasing of the inlet heat transfer fluid. The average heat storage efficiency calculated from experimental data for all the PCMs is 71.8%, meaning that 28.2% of the heat actually was lost.     

Comparison of energy and exergy efficiencies of an underground solar thermal storage system

In this experimental study, solar energy was stored daily using the volcanic material with the sensible heat technique. The external heat collection unit consisted of 27 m² of south‐facing solar air collectors mounted at a 55° tilt angle. The dimensions of the packed‐bed heat storage unit were 6 × 2 × 0.6 m deep. The packed‐bed heat storage unit was built under the soil. The heat storage unit was filled with 6480 kg of volcanic material. Energy and exergy analyses were applied in order to evaluate the system efficiency. During the charging periods, the average daily rates of thermal energy and exergy stored in the heat storage unit were 1242 and 36.33 W, respectively. Since the rate of exergy depends on the temperature of the heat transfer fluid and surrounding, the rate of exergy increased as the difference between the inlet and outlet temperatures of the heat transfer fluid increased during the charging periods. It was found that the average daily net energy and exergy efficiencies in the charging periods were 39.7 and 2.03%, respectively. The average daily net energy efficiency of the heat storage system remained nearly constant during the charging periods. The maximum energy and exergy efficiencies of the heat storage system were 52.9 and 4.9%, respectively. Copyright © 2004 John Wiley & Sons, Ltd.     

Energy analysis of space solar dynamic heat receivers

Energy analysis of space solar dynamic heat receivers employing solid–liquid phase change storage is developed. The heat receiver is a critical component of a solar dynamic system. Phase change thermal energy storage is used in the heat receiver. The energy analysis presented here can be used to understand the energy transfer in the heat receiver and thermal energy storage in phase change materials (PCM). The heat receiver cavity radiation mathematical model and the working fluid tube heat model are established. Energy loss, energy absorbed by gas, the latent and sensible thermal energy storage in PCM, maximum tube temperature, gas outlet temperature and liquid PCM fraction were calculated. The results are analyzed and could be used in heat receiver design.     

太阳辐射填料床储热特性研究

针对给定太阳日辐射曲线,研究集成蓄热单元的太阳光热系统的整体能量的动态转化特性及关键参数影响规律。结果表明：填料床总储热量与传热流体进口流速呈非线性变化,当传热流体进口流速 u_f =0.006 m/s时,填料床总储热量最大;在给定填料总容量和u_f =0.006 m/s的条件下,填料床高径比为5的填料床具有更高的储热能力;在该计算条件下,u_f =0.006 m/s、填料床高径比为5及填料量相对值为1时,太阳光热能实现最大程度上的转化和储存。     

Numerical analysis of latent heat thermal energy storage using encapsulated phase change material for solar thermal power plant

Thermal energy storage improves the load stability and efficiency of solar thermal power plants by reducing fluctuations and intermittency inherent to solar radiation. This paper presents a numerical study on the transient response of packed bed latent heat thermal energy storage system in removing fluctuations in the heat transfer fluid (HTF) temperature during the charging and discharging period. The packed bed consisting of spherical shaped encapsulated phase change materials (PCMs) is integrated in an organic Rankine cycle-based solar thermal power plant for electricity generation. A comprehensive numerical model is developed using flow equations for HTF and two-temperature non-equilibrium energy equation for heat transfer, coupled with enthalpy method to account for phase change in PCM. Systematic parametric studies are performed to understand the effect of mass flow rate, inlet charging system, storage system dimension and encapsulation of the shell diameter on the dynamic behaviour of the storage system. The overall effectiveness and transient temperature difference in HTF temperature in a cycle are computed for different geometrical and operational parameters to evaluate the system performance. It is found that the ability of the latent heat thermal energy storage system to store and release energy is significantly improved by increasing mass flow rate and inlet charging temperature. The transient variation in the HTF temperature can be effectively reduced by decreasing porosity.