强制循环式太阳能热水系统的优化

强制循环式太阳能热水系统的优化杨汇涛，顾海燕，杨延柱家用太阳能热水器通常采用自然循环式，而对于集体用大规模太阳能热水系统，则需采用定温放水直流式或强制循环式，以便于安排庞大的贮热水箱和降低成本。一般强制循环式太阳能热水系统采用图１所示的图１强制循环式...     

双水箱太阳能热水系统的水位关系研究

为了解决工程中常因双水箱太阳能热水系统的设计不当造成的水箱溢水等问题,论文基于强制循环式双水箱太阳能热水系统,通过分析研究系统运行中双水箱的水位变化,给出了两水箱间可能出现的最大水位差与连通管管径之间的函数关系。同时,对应用示例的计算与分析,给出了相应的预留空间大小、连接管管径以及各相关管口的高度位置。本研究对于工程上设计确定双水箱预留空间大小、连通管管径、各相关管口的高度位置具有理论指导意义。     

循环式热水器

循环式热水器基本上可分为自然循环和强迫循环两大类。自然循环热水器如图1所示。它的循环动力是靠热水系统中,冷热水比重不同而产生的热虹吸压头来维持的,所以储热水箱必须高于集热器的上集管。经过一段时间的循环运行,水箱内的水被加热到使用温度。     

强制循环太阳能热水系统的改进

强制循环太阳能热水系统的改进江苏省太阳能研究所杨廷柱，扬汇涛，顾海燕，孙学刚，薛长松小规模的家用太阳能热水器通常采用自然循环式，而对于集体用大规模的太阳能热水系统，则须采用定温放水直流式或强制循环形式。一般强制循环太阳能热水系统如图１所示。阳光照射在...     

太阳能-空气源热泵热水系统多水箱设计方案的优化与能效分析

该文针对高校宿舍热水系统，为提高其经济效益与减排效果提出加入夜间蓄热水箱和热泵机组缓冲水箱的两种多水箱太阳能-空气源热泵热水系统，分别设计优化运行策略。选取水箱体积、集热器面积、倾角以及热泵功率等参数为优化变量，并确定生命周期成本年值与全年运行碳排放量为目标函数，通过对单水箱、双水箱和三水箱热水系统在逐月电耗、电费、太阳能保证率以及平均系统COP等方面的研究与分析，发现三水箱热水系统比传统单水箱全年能节省电耗约3.86%，省电费22.35%，太阳能保证率提高33.32%，平均系统COP提高45.70%，生命周期成本年值降低5.07%，碳排放量减少3.72%，效率提升4.65%。     

太阳热水器

太阳热水器是目前太阳能热利用中最常见的一种装置,经济效益比较明显,正在迅速推广应用。太阳热水器能够将太阳能转换成热能,并用来生产热水,供生产和生活之用。它主要由平板集热器、蓄水箱和连接管道等部件组成,按其系统中水的流动情况,太阳热水器可以分为三类:循环式、直流式和闷晒式。一、循环式循环式太阳热水器按其形成水循环的动力,又可分为自然循环式和强制循环式两种。     

几种太阳能热水器系统

平板太阳能集热器可利用太阳的热能来产生热水。它结构简单,制作容易,使用方便,是人们容易认识并乐于采用的一种太阳能利用设备。平板集热器生产热水,还必须设置一个贮热水箱,于是,平板集热器、贮热水箱及连接这两者的管道、阀门、水泵、控温器等就组成了一个完整的太阳能热水系统。其中,平板集热器的作用为采集热能,并把热能传递给水。贮水箱的作用则是贮存采集到的热能(表现为热水)。由于贮水箱与集热器是分开的两个设备,因而其间的连接管道及管道上的阀门就是必不可少的了。至于是否采用水泵和控温器可视需要而定。太阳能热水系统类型较多,现仅介绍几种采用平板型集热器的热水系统及其运行方式。一、强迫循环太阳能热水系统强迫循环太阳能热水系统主要由集热器、贮水箱、水泵、控温器与管道组成(图1)。水从贮水箱底部流     

强制循环太阳能供热水系统的理论研究

利用热力学分析方法,建立了强制循环太阳能供热水系统容积水箱的数学物理模型,为太阳能供热水系统的实际工程设计和系统性能的改善提供一定的理论指导。     

太阳能蓄热分层水箱数值模拟优化分析

蓄热水箱能够存储和调配能量。将蓄热水箱应用到太阳能热水系统中,可以弥补太阳能的不稳定性和不连续性,有效地提高太阳能热水系统的热利用率。文章基于小型太阳能热水系统,建立蓄热水箱物理模型,应用Fluent软件模拟分析了各个工况下蓄热水箱的温度分层情况,从而寻求较优的温度分层。分析结果表明:当热水入口质量流量小于2.8 kg/s时,蓄热水箱的温度分层比较明显;当热水入口质量流量大于2.8 kg/s时,随着热水入口质量流量逐渐增大,蓄热水箱温度分层越来越不明显;热水入口温度与水箱初始温度对于蓄热水箱温度分层影响不大;当热水入口质量流量为2.8 kg/s时,存在最佳热水入口直径(9 mm),此时蓄热水箱冷、热水不发生混合,蓄热水箱的热利用率较高。     

专利信息

封闭式家用太阳能热水器本发明的目的是提供一种不需补给水箱和浮球阀的自然循环式家用太阳能热水器。它由集热器、热水箱、管道及支架组成。热水箱密封,补给水管是与冷水源直通的水管,供热水管上接有闸阀。本发明的热     

Transient performance of closed loop solar water heating system with heat exchanger

The present paper deals with an analysis of a forced circulation closed loop solar water heating system; withdrawal of hot water of constant flow rate from a storage tank through a heat exchanger is considered. The effect of flow rate and heat exchanger length on the performance has also been discussed for a typical set of parameters and for a typical cold day in Delhi (26 January 1980).     

Transient analysis of closed loop solar water heating system (effect of heat exchangers)

This paper presents a general and more realistic model of the transient behaviour of a forced circulation solar water heating system with and without heat exchangers in the collector loop and storage tank. The analysis has been presented for a constant flow mode. The effects of heat exchanger length and various water heating system parameters on its performance have been studied. Numerical calculations have been made for a typical cold day (26 January 1980) at Delhi.     

Optimal flow control of a forced circulation solar water heating system with energy storage units and connecting pipes

This paper focuses on pump flow rate optimization for forced circulation solar water heating systems with pipes. The system consists of: an array of flat plate solar collectors, two storage tanks for the circulation fluid and water, a heat exchanger, two pumps, and connecting pipes. The storage tanks operate in the fully mixed regime to avoid thermal stratification. The pipes are considered as separated components in the system so as to account for their thermal effects. The objective is to determine optimal flow rates in the primary and secondary loops in order to maximize energy transfer to the circulation fluid storage tank, while reaching user defined temperatures in the water storage tank to increase thermal comfort. A model is developed using mainly the first and second laws of thermodynamics. The model is used to maximize the difference between the energy extracted from the solar collector and the combined sum of the energy extracted by the heat exchanger and corresponding energies used by the pumps in the primary and secondary loops. The objective function maximizes the overall system energy gain whilst minimizing the sum of the energy extracted by the heat exchanger and corresponding pump energy in the secondary loop to conserve stored energy and meet the user requirement of water tank temperatures. A case study is shown to illustrate the effects of the model. When compared to other flow control techniques, in particular the most suitable energy efficient control strategy, the results of this study show a 7.82% increase in the amount of energy extracted. The results also show system thermal losses ranging between 5.54% and 7.34% for the different control strategies due to connecting pipe losses.     

Transient analysis of forced circulation solar water heating system

This paper presents a transient analysis of a solar water heating system with forced circulation. Two modes of hot water retrieval have been taken into account viz direct from the tank and through a heat exchanger placed in the tank. Analysis has been presented both for constant flow and constant collection temperature modes. Effects of heat exchanger length and time of starting hot water retrieval on the system performance have also been studied. Numerical calculations have been made for a typical cold day (26 January, 1980) at Delhi.     

两种太阳能集热器的瞬时效率对比分析

对强制循环全玻璃真空管太阳能热水系统和强制循环热管式真空管太阳能热水系统的瞬时效率进行了对比分析,发现全玻璃真空管热水系统的效率曲线的斜率大于热管式真空管热水系统,这说明两种热水系统在运行温度相同时,热管式真空管的热损失较小,瞬时效率较高,有较好的高温特性和保温特性,并且热管式真空管太阳集热器的集热效率波动较小,能稳定在较高的水平。     

Forced versus natural circulation solar water heaters: A comparative performance study

An experimental study has been carried out to compare the performance of natural and forced circulation domestic solar water heaters. Several measurments have been made for the two cases which included; the collector water inlet and outlet temperatures, the mass flow rate, the tank temperature, the ambient temperature and the solar insolation. The main parameters for the solar collector are calculated for the natural and forced circulation systems. These included; the top, back, and overall loss coefficients, the heat removal factor, the efficiency factor, the useful energy gain and the instantaneous efficiency. The comparison showed that the efficiency of the forced circulation system could be 35 to 80% higher.     

Refrigerant-charged integrated solar water heater

The performance of two R-11-charged integrated solar water heater collectors was investigated experimentally for forced and natural circulation water flows. The heat transfer from the refrigerant loop to the hot water storage tank took place through a condenser of novel design integrated within the collector frame. The effect of the condenser inclination on the system efficiency was remarkable for natural circulation water flow but had no significant effect for forced circulation flow. The difference in thermal response between the refrigerant and water loops caused buildup of stored energy in the condenser. This energy affected the buoyancy forces and generated flow pulsation that caused a harmonic-like variation of the system efficiency. This effect vanished with forced water circulation flow. The system efficiency varied between 20 and 50% depending on the solar insolation.     

Transient analysis of parallel plate forced circulation solar water heating system

In this paper, a transient analysis of a forced circulation solar water heating system with and without heat exchangers in the collector loop and storage tank has been presented for a parallel flat plate collector. The effect of various water heating system parameters on its performance have been studied. Numerical calculations have been made for a typical cold day viz. 26 January 1980 in Delhi.     

Optimal design of a forced circulation solar water heating system for a residential unit in cold climate using TRNSYS

An indirect forced circulation solar water heating systems using a flat-plate collector is modeled for domestic hot water requirements of a single-family residential unit in Montreal, Canada. All necessary design parameters are studied and the optimum values are determined using TRNSYS simulation program. The solar fraction of the entire system is used as the optimization parameter. Design parameters of both the system and the collector were optimized that include collector area, fluid type, collector mass flow rate, storage tank volume and height, heat exchanger effectiveness, size and length of connecting pipes, absorber plate material and thickness, number and size of the riser tubes, tube spacing, and the collector’s aspect ratio. The results show that by utilizing solar energy, the designed system could provide 83-97% and 30-62% of the hot water demands in summer and winter, respectively. It is also determined that even a locally made non-selective-coated collector can supply about 54% of the annual water heating energy requirement by solar energy.     

Study on performance of solar assisted air source heat pump systems for hot water production in Hong Kong

This paper reports the investigation results on application of the solar assisted air source heat pump systems for hot water production in Hong Kong. A mathematical model of the system is developed to predict its operating performance under specified weather conditions. The optimum flow rate from the load water tank to the condenser is proposed considering both the appropriate outlet water temperature and system performance. The effect of various parameters, including circulation flow rate, solar collector area, tilt angle of solar collector array and initial water temperature in the preheating solar tank is investigated, and the results show that the system performance is governed strongly by the change of circulation flow rate, solar collector area and initial water temperature in the preheating solar tank.