Performance and testing of large-size solar water heater cum solar cooker

The performance of a novel device has been tested. The device can be used as a collector cum storage type solar water heater during the winter, and, with minor adjustments, it can be used as a hot-box solar cooker. The device can provide hot water at 50–60°C in the evening, which can be maintained at 40–45°C until the following morning. It can also be used for cooking food for about 40 people. The efficiencies of the device as a solar water heater and as a solar cooker have been found to be 67.7% and 29.8%, respectively. The payback period varies between 1.64 to 5.90 years depending on the fuel it replaces. The payback periods are of increasing length with respect to the fuels firewood, coal, electricity, LPG and kerosene.     

The performance of a cylindrical solar water heater

A cylindrical solar water heater is designed and manufactured in the Department of Mechanical Engineering, University of Bahrain. It consists of a cylindrical tube made from high quality glass having a length of 0.8, 0.14 m outer diameter and a thickness of 6 mm. A copper coil tube in the shape of spiral rings, with the tube inner diameter of 2 mm and outer diameter of 3.175 mm, painted black, serves as a collector to the incident solar energy on the cylinder wall. The thermal performance was evaluated extensively throughout the months of March and April 2002; a maximum temperature difference of 27.8 °C between inlet and outlet of the solar water heater at a mass flow rate of 9 kg/h was achieved. The efficiency of the cylindrical solar water heater was calculated. The maximum value during the experimental period was found to be 41.8%. This reveals a good capability of the system to convert solar energy to heat which can be used for heating water. An economic analysis has reveals that the cylindrical solar water heater compared with the flat plate collector is cost effective.     

Year round performance of a cylindrical solar water heater

A cylindrical collector-cum-storage type solar water heater has been designed, developed and tested. Its year round performance has been carried out and reported in this paper. The heater can provide 50 litres of hot water at 50–60°C in the afternoon and a temperature of 35°C can be retained till the next day for early morning use. The heater receives approximately 30% more radiation as compared to a flat surface. The economics of the heater has been worked out and it has been found that the cost can be recovered within one year.     

Design and performance studies on a solar room heater

Almost all the research and development of solar heating has been directed towards large and expensive buildings in areas where conventional fuel and electricity are plentiful and cheap. Keeping this in mind a solar room heater capable of heating single rooms to comfortable level has been designed and tested for two winter seasons at Roorkee. Simple design curves for finding out the absorber size, for a given heating load for a number of Indian cities, and panel size for the specified requirement are developed and discussed. Water is used as a heat storage media and hot water is stored in a number of storage panels placed inside the room near the wall. Radiative and convective heat losses from the surface of panels heat the room air. Temperature distribution in the experimental and office room with and without heating it along with the ambient air temperature and solar insolation are measured and discussed. It is concluded that conventional rooms can be conveniently heated to comfortable levels by solar energy.     

Design and thermal performance of a matrix solar air heater

In this communication we describe the design of a matrix air heater. The performance of the heater has been tested under constant flow conditions on two days separated by an interval of 20 days. The efficiency is seen to be reduced to an average of 27.4% from an initial value of about 38.9%.     

Design and performance of a roof integrated solar air heater

This paper discusses the design and construction of a roof integrated solar air heater used in a space heating system for a well insulated house located in Melbourne, Australia. The design of the house and the heat storage system is not discussed and details may be obtained elswhere [1]. The space heating system consists of an array of solar air heaters coupled to a rockbed thermal store located under the floor of the house, such that the rooms are heated by radiation and convection from the floor.     

Long-term thermal performance of a two-phase thermosyphon solar water heater

This article investigates experimentally the long-term thermal performance of a two-phase thermosyphon solar water heater and compares the results with the conventional systems. Experimental investigations are conducted to obtain the system thermal efficiencies from the hourly, daily and long-term performance tests. Different heat transfer mechanisms, including natural convection, geyser boiling, nucleate boiling and film-wise condensation, are observed in the two-phase thermosyphon solar water heater while solar radiation varies. The thermal performance of the proposed system is compared with that of four conventional solar water heaters. Results show that the proposed system achieves system characteristic efficiency 18% higher than that of the conventional systems by reducing heat loss for the two-phase thermosyphon solar water heater.     

Design and thermal performance evaluation of a novel solar air heater

In the present scenario, numerous applications perform on solar energy for cooking, heating and cooling, and power generation, globally. Solar air heaters are one of these applications purposely used for, drying, timber seasoning and space heating. In the present work, a solar air heater (SAH) has been designed to produce a good exhaust temperature for long hours especially in the case of poor ambient conditions or during off sunshine hours. A mixture of desert and granular carbon in the ratio of 4:6 has been used as thermal heat storage inside the SAH. Two halogen lights of 300 W are used to increase the exhaust temperature of the SAH by placing them in the inlet and outlet ducts. All the experiments have conducted on natural and forced convection for performance evaluation on two similar design solar air heaters (with and without heat storage). The comparisons are made with two similar design solar air heaters carrying desert and granular carbon, as an individual heat storing media, to find out an optimum design of a SAH with long term heating. The thermal efficiencies of the novel SAH range from 18.04% to 20.78% of natural convection and 52.21%–80.05% with forced convection.     

Energy conservation and field performance of a natural circulation type solar water heater

A natural circulation type solar water heater has been fabricated and installed at the CAZRI Guest House. Its field performance has been evaluated. The heater provides 2001 of hot water at 50–60 °C at all times. This solar water heater is economical.     

Measured performance of a solar water heater with a parallel tube polymer absorber

We performed calibrated side-by-side measurements of the thermal performance of solar water heaters with spaced polypropylene tube absorbers in identical glazed and insulated collector boxes. This was to determine the influence of tube spacing and tube height above the back insulation. A low flow rate (4.32 g s⁻¹ m⁻²) was used. As the number of tubes (spaced over the same aperture) is increased by 76.3% (from 38 to 67), the mean mid day efficiency increases by only 12.9% (7.4 percentage points), from 57.2% to 64.6%. It may therefore be more cost effective to use fewer, more widely spaced tubes. As tube height h above the insulation increased from the lowest value (3 mm) to the next (8 mm), the thermal efficiency dropped 1.4 percentage points. From h = 8 to 28 mm, the efficiency was almost independent of h.     

Analysis and performance of a low-cost solar heater

One of the alternatives to reduce the consumption of electricity for heating water is by popularizing the use of solar energy. This work contributes with studies on a Low-Cost Solar Heater (LCSH), a new concept of solar water heater made entirely of polymeric materials, which requires a relatively low investment and is user-assembled. The solar collector, which absorbs solar energy and transfers it to water in the form of heat, is composed of uncovered flat panels of rigid PVC. The storage tank that holds the water heated during the day is made of polyethylene coated with polystyrene. The results of the LCSH were compared with those of a conventional solar heater composed of a glass-covered copper collector and a stainless steel storage tank. The efficiency of the systems was evaluated by measuring the incident solar radiation and water temperature with the systems operating naturally (thermosiphon). The heat loss in the hot water storage tanks was measured to estimate the thermal performance of the solar heaters. Considering that the target temperature for the heated water is slightly above the ambient temperature, the results indicated that the LCSH showed a satisfactory global heat transfer coefficient for storage tanks and that it attained an excellent thermal performance, although it is not as efficient as the conventional heater.     

Design and thermal performance of an ICS solar water heater based on three parabolic sections

An integrated collector storage (ICS) consisting of a single cylindrical horizontal tank placed in a reflector composed of three parabolic branches is designed and geometric characteristics are determined. The suggested design aims to cover the need of hot water of a family composed of four persons. Based on this target, its geometric characteristics: reflector geometry, aperture, reflector length, are derived.The comparison between this system and two other systems of solar water heater, composed of a storage tank with asymmetrical CPC and symmetrical CPC, shows important thermal performances despite the simplicity and the little cost of our collector. The first experimental results are given and its comparison with the theoretical results demonstrates a good agreement.     

“看不见”的太阳能热水器

太阳能热水器已经走进千家万户,但其市场仍主要在农村和小城镇,城市市场的份额相对较小。其原因在于在城市高楼大厦上安装太阳能热水器被安装场地和城市建筑美观要求所局限。随着我国城市现代化、农村城镇化进程的加快,住宅建筑形式也向多样化发展,普通落水式太阳能热水器的安装局限性开始显现,甚至有的小区楼顶已经不允许安装,这对太阳能热水器与建筑的结合提出了更高要求。因而,太阳能与建筑一体化成为打破这一瓶颈的有效解决方案。     

太阳热水器技术讲座(三)家用太阳热水器

太阳热水器(或称太阳热水装置)根据用途可分为家用热水器和太阳热水系统(或称太阳热水工程)。严格来说，应按国标GB／18713—2002规定来区分，即水箱容水量在0．6t以下的太阳热水器称之为家用太阳热水器．而水箱容量大于0．6t的太阳热水器称之为太阳热水系统。     

Year-round performance of an improved collector-cum-storage type solar water heater

Systematic studies have been carried out on collector-cum-storage type solar water heaters, and efforts were made to minimise heat losses so that this type of water heater can be used for getting hot water at 40°–45°C for taking baths in the early morning hours of the next day. This paper reports year round performace, the performance equation and economics of this new improved solar water heater. This heater can supply 100 litres of hot water at 60°–70°C in the afternoon, and 40°–45°C temperature can be retained till next day morning. Its efficiency is 70.1%.     

平板型太阳能热水器性能试验及其模拟对比

以TRNSYS程序为平台,对平板型太阳能热水器进行了模拟研究,TRNSYS模拟结果与试验结果的吻合较好。试验显示,不同天气下日总辐照量对太阳能热水器日平均效率的影响不大,日总辐照量在5.3～22.2 MJ时,系统热效率稳定在52%左右。文章分析了典型天气条件下系统日平均有用能量输出与辅助能量的关系,为太阳能热水器辅助热源与集热面积的优化配置提供参考。     

Year round performance of thermosyphon solar water heater in Benghazi

The relative merits of a thermosyphon heater for domestic water heating are brought to light with special emphasis to Libyan weather conditions. The experimental performance of this type of heater was studied by the authors for a brief period and reported in an earlier study. In the present study, year-round experimental performance is reported. Measurements performed all over the year showed that water is heated to a maximum temperature of 66°C while the minimum temperature during six months was as high as 50°C. The picture is no less bright from an overall efficiency point of view. Efficiency ranges as high as 40 to 50%. Hourly measurements on various days showed that the water temperature has an increasing trend, irrespective of the fluctuating solar radiation pattern on a cloudy day.     

太阳热水器技术讲座(五)太阳热水器的生产

1平板太阳集热器的生产平板太阳集热器是平板太阳热水器的关键部件,它的产品质量直接影响热水器的性能,其生产成本约占热水器总成本的1/2。根据吸热板的断面结构形状来看,平板集热器有管板式、翼管式、扁盒式、扁方式、塑料圆管式、铜铝复合式等(图1),还有蛇形管式和热管式。集热器吸热板的长宽尺寸应按照国家标准GB/T6424—1997的规定加以选择。吸热板的进水口和出水口的设置基本可分为4出口(外循环)和3出口(内循环)2类,如图2所示。(1)吸热板的生产吸热板的生产要根据吸热板的材料及其工质通道与板的结合方式确定加工工艺。例如:不锈钢扁…     

Forced circulation solar water heater performance prediction by TRNSYS and ANN

The design and applicability of solar water heating systems requires a satisfactory prediction of collector outlet water temperature and the useful energy delivered over a wide range of climatic conditions. Transient system simulation program is extensively used for this purpose, and recently artificial neural networks have also been considered. This article presents the results of a study carried out to compare the performance prediction by these two methods in a tropical location under different climatic conditions. Experimental collector outlet temperature, storage tank temperatures and the useful energy values were compared with the results of the simulation by these two methods. Hourly and daily values under different conditions were also compared. Details of the experimental set up and observations, the modeling procedure used and the statistical measures to compare the capabilities of the two methods under clear, partly cloudy, and cloudy conditions have been described. The prediction of both the methods are found to be good for both hourly and daily estimations, and the specific requirements for satisfactory performance prediction of each of the methods have been detailed.