Background

Solar domestic hot water systems heat water by receiving sun's radiant energy using solar thermal collectors. Solar collectors absorb the sun's rays and convert them to heat. This heat is then absorbed by the working fluid, which passes through the collector and may be stored or used directly. Since solar collectors are the most important part of solar water heating systems, this study offers some techniques to improve their efficiency.

Method

In this experimental study, the thermal efficiency of a vacuum tube solar collector was improved using three types of absorber tubes. Nanofluid of silica/water-ethylene glycol was incorporated inside the absorber tubes. Experimental data including instantaneous inlet and outlet temperatures, ambient temperature and solar radiation were measured. Comparisons were performed between the thermal performance of spiral-tube as well as helical-coil and U-tube.

Findings

Experimental results revealed that the use of both spiral and helical-coil tubes improved the efficiency significantly, in which the helical-coil tubes performed much better. In addition, in the absence of nano-additives, economic calculations revealed that using spiral and helical-coil tubes increased the cost by 60% and 72%. In the case of nanofluid, the use of nanofluids in the helical coil intensified the cost by 3.4 times.

中文翻译：

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介绍两种考虑经济标准的提高真空U型管太阳能集热器效率的方案

背景

太阳能家用热水系统通过使用太阳能集热器接收太阳辐射能来加热水。太阳能集热器吸收太阳光线并将其转化为热量。然后这些热量被工作流体吸收，工作流体通过收集器并可以直接储存或使用。由于太阳能集热器是太阳能热水系统中最重要的部分，因此本研究提供了一些提高其效率的技术。

方法

在这项实验研究中，使用三种类型的吸收管提高了真空管太阳能集热器的热效率。二氧化硅/水-乙二醇纳米流体被加入吸收管内。测量了包括瞬时入口和出口温度、环境温度和太阳辐射在内的实验数据。对螺旋管以及螺旋盘管和 U 型管的热性能进行了比较。

发现

实验结果表明，同时使用螺旋管和螺旋盘管显着提高了效率，其中螺旋盘管的性能要好得多。此外，在没有纳米添加剂的情况下，经济计算表明，使用螺旋管和螺旋盘管会使成本增加 60% 和 72%。在纳米流体的情况下，在螺旋线圈中使用纳米流体使成本增加了 3.4 倍。