怎样提高真空管式太阳热水器日平均热效率

衡量太阳热水器热性能的重要指标之一是日平均热效率，日平均热效率越高，相同条件下整机有效得热量就越大。我们知道平板式太阳热水器日平均热效率大都在60％以上，而全玻璃真空管太阳热水器日平均热效率只有45％（国标）左右，问题出在哪里呢？     

全玻璃真空太阳热水器的选购

对于消费者来说，全玻璃真空管太阳热水器的选购存在一定难度。因为它既不同于冰箱、洗衣机等早已进入千家万户、性能已被人们熟知的家电产品，也不同于家具、衣物等质量优劣较易判定的消费品。真空管太阳热水器的各项技术指标、性能及影响使用寿命的原材料质量等关键因素在初次购买时很难判别，往往在使用过程中才能慢慢体会。现在，市场上的真空管太阳热水器外观相似，但内在品质差别极大。选购一台优质高效、性能价格比合理的放心产品，可以从 8个方面进行对比： 一得热量 太阳热水器一年的得热量多少兆焦 (MJ)是热性能的一项主要指标。通常在日太阳总辐照度大于 17MJ／ m2条件下测定太阳热水器的得热量，再按运用地区换算成一年的得热量。得热量的多少主要取决于以下几个因素： 1 全玻璃真空集热管优劣 全玻璃真空集热管是真空管太阳热水器的核心集热部件，它的生产有三大关键技术：内、外管之间夹层高真空的获得和长久保持；具有高的太阳吸收比和低的热发射比的选择性吸收涂层；透光比高、强度大、热膨胀系数小 (即耐热冲击性能优良 )的优质硼硅玻璃 3 3材料。 全玻璃真空集热管的生产工艺复杂、技术难度大，各项性能指标在线检测困难。消费者凭肉眼几乎无法鉴别真空管的优劣，应注意选择名牌产品，例如清华阳光公司生产的北京名牌——“晒乐”牌全玻璃真空太阳集热管。 2 漫反射板材料和结构的合理性 全玻璃真空太阳集热管具有圆柱面的吸热体，往往在组装成太阳热水器时全玻璃真空集热管相隔一定距离，其背部装有反射器，以提高真空管太阳热水器的性能价格比。反射器有两种： (1)复合抛物面聚光器 (CPC)是较理想的镜面反射器，但镜面材料昂贵，以及运用过程中灰尘与树叶的覆盖，使镜反射比下降约一半，失去了优势。目前市场上有不少是用漫反射材料制成曲面反射器，费用增加而性能并未提高。 (2)平板漫反射器，具有好的性能价格比。     

玻璃真空管内插热管式太阳热水系统热性能研究

对玻璃真空管内插热管式太阳集热系统的结构特点和热性能进行了研究.通过理论分析和热性能实验,对两种热水器的日有用得热量、平均热损因数进行了分析研究,并将实验数据用最小二乘法拟合,得出较为理想的热性能曲线.理论分析与实验结果表明:玻璃真空管内插热管式热水器与全玻璃真空管式热水器相比,日有用得热量高、平均热损因数小、热容小,具有较好的高温效率特性和保温特性,为其在太阳能膜蒸馏系统上的应用研究奠定了基础.     

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。     

带内集管的分体式太阳能热水器及其实验研究

为了实现太阳能热水器和建筑的结合,设计了一种分体式全玻璃真空管太阳能热水器。它由集热器、室内储水箱、上升管和下降管组成,其集热器的每根真空管内有一个分水管,分水管通过集箱内的集管与下降管相连。与已有的太阳能热水器相比,其分水管把真空管内的冷、热水流道分开,减少了冷热水流相互干扰,提高了热水器效率,同时实现了分体式太阳能热水器系统的自然循环。实验表明,带内集管的分体式太阳能热水器比不带内集管的分体式太阳能热水器有更高的效率。     

新型太阳热水器的设计及实验

常见的太阳热水器分两种形式，平板型和全玻璃真空管式。由于平板式太阳热水器热损较大，冬季环境温度低，平板太阳热水器无法使用，所以近几年平板太阳热水器已逐步退出市场；全玻璃真空管式太阳热水器由于采用了真空绝热技术、光谱选择性吸收技术，使得真空管集热器热损低，集热效率高，     

怎样提高真空管太陽熱水器日平均热效率

衡量太阳热水器热性能的重要指标之一是日 平均热效率,日平均热效率越高,相同条件下整 机有效得热量就越大。我们知道平板式太阳热水 器日平均热效率大都在60％以上,而全玻璃真空 管太阳热水器日平均热效率只有45％(国标)左 右,问题出在哪里呢?     

三防真空管太阳热水器通过评审

2月11日,北京市新能源与可再生能源协会组织业内专家对北京市天鸣阳光太阳能科技有限公司研制的“三防真空管太阳热水器”进行了技术评审。评审结论如下:1.该公司在国家专利(ZL98206638.4)的基础上研制生产的三防真空管太阳热水器是对普通紧凑式全玻璃真空管热水器的大胆创造和改进,具有设计新颖、构思巧妙、结构简单等特点。2.该产品与普通全玻璃真空管热水器相比,具有减轻真空管结垢和沉积物生成、防止上水炸管、防止单管破裂、跑水等功能。3.该产品与普通产品相比使用安全、运行可靠,维修工作量小,附加成本低,具有显著的技术经济效益,是…     

不同朝向全玻璃真空太阳集热管的热性能比较

为了确定不同朝向全玻璃真空太阳集热管的热性能,从太阳累计辐射与真空管储水箱温差关系入手,对水平、倾斜以及垂直朝向的真空管进行了系列的试验。研究结果表明,自然循环时,不同朝向真空管具有不同的集热性能,测量日上午6:00-10:00,垂直真空管具有最高的集热性能,水平管最低,其他时间则是倾斜真空管最高,垂直管最低;倾斜真空管系统日总得热量为1.17×10~6J,水平及垂直真空管系统总得热量分别为1.12×10~6J和0.88×10~6J,各占倾斜管总得热量的96.35%和75.56%。     

上海地区应用全玻璃真空管太阳热水器的经济评估

此文根据已有资料，对全玻璃真空管太阳热水器和煤气热水器的总体使用性能进行了较实际的计算比较。结果表明，上海地区使用全玻璃真空管太阳热水器的年运行费用比煤气热水器节省４２％左右。到达１５年寿命期后，累计寿命期内节省的总费用，又可购买一台新的同型号太阳热水器。这相当于用户一次投资安装全玻璃真空管太阳热水器后，可永久使用。总体效益十分可取。欢迎读者各抒己见，展开讨论。———编者     

Study of a solar water heater using stationary V-trough collector

There are various types of solar water heater system available in the commercial market to fulfill different customers’ demand, such as flat plate collector, concentrating collector, evacuated tube collector and integrated collector storage. A cost effective cum easy fabricated V-trough solar water heater system using forced circulation system is proposed. Integrating the solar absorber with the easily fabricated V-trough reflector can improve the performance of solar water heater system. In this paper, optical analysis, experimental study and cost analysis of the stationary V-trough solar water heater system are presented in details. The experimental result has shown very promising results in both optical efficiency of V-trough reflector and the overall thermal performance of the solar water heater.     

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.     

竖管内空气强迫与自然对流换热实验

对竖直圆管内空气强迫对流换热与自然对流换热进行了实验，从量级上表明了两者的不同，由实验得到了用雷诺数表示的自然对流换热关联式，与现有的大空间自然对流换热公式作了比较。     

带有内插棒的全玻璃真空管太阳热水器的实验研究

对一种带有内插棒的全真空集热管和由其构成的热水器进行了实验研究。结果表明，该管热容小、启动快、传热和流动性好，热水器的热效率和水利用率较高，防冻抗冻性能优良。     

蜂窝热管平板式太阳能热水器的实验研究

把蜂窝技术和热管技术结合起来应用于平板式太阳能热水器，可以大大减少热损失，提高日平均效率。经多次实验证明，蜂窝热管平板式太阳能热水器的日平均效率可以比真空管式热水器的高，热损系数则要小很多，具有推广应用价值。     

Performance of a dual-purpose solar continuous adsorption system

A conceptual design and performance of a dual-purpose solar continuous adsorption system for domestic refrigeration and water heating is described. Malaysian activated carbon and methanol are used as the adsorbent–adsorbate pair. The heat rejected by the adsorber beds and condensers during the cooling process of the refrigeration part is recovered and used to heat water for the purpose of domestic consumption. In a continuous 24-h cycle, 16.9 MJ/day of heat can be recovered for heating of water in the storage tanks. In the single-purpose intermittent solar adsorption system, this heat is wasted. The total energy input to the dual-purpose system during a 24-h operation is 61.2 MJ/day and the total energy output is 50 MJ/day. The latter is made up of 44.7 MJ/day for water heating and 5.3 MJ/day for ice making. The amount of ice that can be produced is 12 kg/day. Using typical value for the efficiency of evacuated tube collector of water heating system of 65%, the following coefficient of performances (COP's) are obtained: 44% for adsorption refrigeration cycle, 73% for dual-purpose solar water heater, 9.1% for dual-purpose solar adsorption refrigeration and 82.1% for dual-purpose of both solar water heater and refrigerator.     

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.     

Performance and testing of improved natural circulation type solar water heater in Arid areas

A conventional natural circulation type solar water heater has been improved upon by eliminating the float valve and using a sealed pressure tank instead of an open tank. Performance of the improved natural circulation type solar water heater has been compared with and without solar-selective surfaces. The detailed design, fabrication and testing have been reported in this paper. The efficiency of the improved natural circulation type solar water heater with and without solar-selective surfaces is 57.5 and 51.0%, respectively.     

三维立体式太阳热水器及其集热盲区

文中给出了三维立体式太阳热水器，并由实验证明了三维立体式太阳热水器的热效率高于平板型太阳热水器，同时给出了在不同纬度地区的集热盲区的计算方法。要提高热效率，必须避开集热盲区。