真空玻璃盖板热管平板式太阳能热水器的研制

介绍了研究成功的采用真空玻璃盖板的热管平板式太阳能热水器,测试了其性能,并与全玻璃真空管太阳能热水器和蜂窝热管太阳能热水器进行了比较。实测得到,真空玻璃盖板热管平板式热水器的日平均效率比后两分别大13．3％和6．5％,平均热损系数比后两分别小52．5％和21．5％。真空玻璃盖板平板式太阳能热水器性能优越,有很好的应用前景。     

平板式与真空管式太阳热水器热性能分析比较

在太阳热水器中依据吸热体的形状,可将其分为平板式太阳热水器和真空管式太阳热水器两大类。由于吸热体形状的不同,导致这两类热水器在热性能上各有差异。在家用太阳热水器热性能测试的国标中,热性能指标主要有日平均效率η d、平均热损系数 UL和非稳态效率方程。其中,日平均效率η d描述了在正常天气状况 (晴天 )下,一日内在热水器采光面上接收到的太阳辐射量中转化为提高水箱水温的热量的百分比;平均热损系数则反映了在无日照等条件下,热水器整体的保温性能;而非稳态效率是上述的热转换效率在不同时点的体现,非稳态效率方程则是…     

热管在太阳能热利用技术中的应用

作为一种高效传热元件，热管具有优良的特性，在许多领域已得到了广泛的应用。文章论述了热管技术在太阳集热器、太阳真空集热管以及其它太阳能热利用方面的应用和发展。     

阳台用热管式真空管太阳热水器

对于城镇高楼住宅的居民来说,如何安装太阳热水器,一直是人们十分关心的问题。经过多种方案比较,我们认为最现实的方案是将太阳热水器安装在楼房朝南的阳台上,其关键是热水器的性能要优越,外型美观,能跟建筑结合。热管式真空管太阳集热器是我国太阳能行业中颇具特色...     

分体式太阳热水器的热特性

分体式太阳热水器的热特性李元哲现有太阳热水器用于楼房住宅，一般只能安装在楼顶。但对高层住宅和不少多层住宅来说，楼顶往往不能或不足以安装足够的热水器，其余能开发利用的地方只有楼房的南立面。而在南立面安装的热水器，必须满足在能提供足够热水的前提下，不占或...     

选择性吸收黑铬涂层及其应用

从世界范围来看，主流的太阳热水器总体上可分为真空管式和平板式两大类，因为客观上它们各有其优劣势，所以二者将在消费市场上共存将是不争的事实。真空管式太阳热水器在我国家用市场有优势；而平板式太阳集热器以其优异的性价比和承压好被选为系统工程和。太阳能与建筑相结合。方案的理想产品，目前它在国外太阳能市场占有很大优势。     

与建筑结合的几种真空管太阳集热器

由于多数太阳热水器属于“事后安装”且品种规格各异，因此造成杂乱无章的无序状态，极大地影响了原建筑的整体外观形象，甚至影响到整个城市的建筑风貌。这一问题如果得不到很好的解决，势必会影响到太阳热水器的普及和推广。本文着重介绍北京桑达公司生产的几种真空集热管产品在国内外与建筑结合的成功范例。     

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，     

太阳热水器的新起点--全玻璃热管真空集热管研制成功

为了降低成本,解决直接走水的真空管太阳热水器在玻璃管内结垢、管子易炸裂及在严寒地区使用会冻结的问题,北京清华索兰环能技术研究所在１９９８年成功地研制出热管与玻璃真空管合为一体的全玻璃热管真空集热管,用该管可以替代金属热管真空集热管。其外径与一般玻璃真...     

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。     

Effect of amount of fluid charge in thermal performance of loop heat pipe

Loop heat pipes (LHPs) are two‐phase thermal control system, which works only by heat from its cooling target. In order to utilize the LHPs in various fields, it is required to be smaller, more reliable, and higher in performance. In the present study, a miniature LHP has been fabricated, and the effect of the amount of working fluid charged on thermal performance of the LHPs has been investigated. Tests were conducted including start‐up, and power step up, as function of the amount of working fluid. The test results showed that under‐charging the working fluid caused start‐up failure, while over‐charging the working fluid made the LHP less stable. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/htj.20306     

太阳能用低温无机工质热管的试验方法

阐述了以无机元素为传热工质,工作范围为40～200℃的太阳能用低温热管的试验方法。试验方法给出了试验条件、要求和仪器设备。通过对数千支热管试验数据的归纳、整理、分析,确定了热管的启动性能,等温性能和耐高、低温性能等技术指标,经过在太阳能热水器和太阳能集热工程中的实际运行表明,可以满足使用要求。     

Steady flow and heat transfer of a Sisko fluid in annular pipe

The flow and heat transfer problem of a Sisko fluid in an annular pipe is considered. The governing nonlinear equation of an incompressible Sisko fluid is modelled. Both analytical and numerical solutions of the governing nonlinear problem are presented. The analytical solutions are developed using homotopy analysis method (HAM) and for the numerical solutions the finite difference method in combination with an iterative scheme is used. A comparison between the analytical and the numerical solutions is presented. Moreover, the shear-thinning and shear-thickening behaviors of the non-Newtonian Sisko fluid are discussed through several graphs and a comparison is also made with the Newtonian fluid.     

Numerical prediction of fluid flow and heat transfer in a wavy pipe

IntroductionA pipe with periodically converging-divergingcross-section is one Of the sevens devices employed forenhancing the heat and mass tusfer efficiency. Thenuid flow, to the now passages with a periodicallyvaling cross-section, attains a folly develOPed acmethat differs fundamentally from that for a convelltionalconstant-area flow channel. In the periodically vwigcross-seCtions, the ac developed VelM field repeatsitSelf at cormsponding edal locations in successivecycles. The change of…     

Mathematical modeling of an arterial heat pipe with excess fluid charge

The capillary heat transfer limit of an arterial heat pipe is studied. A mathematical model accounting for excess fluid charge is developed. The model is based on one-dimensional conservation equations. Two interrelated dryout mechanisms are considered in the model: the first one takes into account the capillary limit along the heat pipe length and the second along the heat pipe circumference. The model predictions are compared with measurement results. The effects of uncertainties in the fluid charge and critical geometric parameters on the heat transfer limit calculations are studied. The importance of the meniscus contact angle on the results is discussed. It is demonstrated that the proposed mathematical model can be used to make conservative predictions for the capillary heat transfer limit of an arterial heat pipe.     

Influence of filling ratio and working fluid thermal properties on starting up and heat transferring performance of closed loop plate oscillating heat pipe with parallel channels

Using ethanol or acetone as the working fluid, the performance of starting up and heat transfer of closed-loop plate oscillating heat pipe with parallel channels(POHP-PC) were experimentally investigated by varying filling ratio, inclination, working fluids and heating power. The performance of the tested pulsating heat pipe was mainly evaluated by thermal resistance and wall temperature. Heating copper block and cold water bath were adopted in the experimental investigations. It was found that oscillating heat pipe with filling ratio of 50% started up earlier than that with 70% when heating input was 159.4 W, however, it has similar starting up performance with filling ratio of 50% as compared to 70% on the condition of heat input of 205.4 W. And heat pipe with filling ratio of 10% could not start up but directly transit to dry burning. A reasonable filling ratio range of 35%-70% was needed in order to achieve better performance, and there are different optimal filling ratios with different heating inputs- the more heating input, the higher optimal filling ratio, and vice versa. However, the dry burning appeared easily with low filling ratio, especially at very low filling ratio, such as 10%. And higher filling ratio, such as 70%, resulted in higher heat transfer( dry burning) limit. With filling ratio of 70% and inclination of 75°, oscillating heat pipe with acetone started up with heating input of just 24 W, but for ethanol, it needed to be achieved 68 W, Furthermore, the start time with acetone was similar as compared to that with ethanol. For steady operating state, the heating input with acetone was about 80 W, but it transited to dry burning state when heating input was greater than 160 W. However, for ethanol, the heating input was in vicinity of 160 W. Furthermore, thermal resistance with acetone was lower than that with ethanol at the same heating input of 120 W.     

Longitudinal heat transfer enhanced by fluid oscillation in a circular pipe with conductive wall

The longitudinal heat transfer in capillary pipes is enhanced by fluid oscillation. The analytical solution to this phenomenon was obtained considering the wall thermal conductivity. Based on this solution, the effects of wall conductivity and thickness were investigated for the case of large amplitude of fluid motion. The longitudinal heat transfer through the fluid part was more enhanced in highly conductive thick pipes. This is because the region where the heat is transferred backwards is smaller in these pipe sections. The direction of longitudinal heat transfer depends on the phase difference of temporary change between the velocity and temperature; it depends on whether or not the difference exceeds π/2. From this point of view, the most effective wall regarding this problem is presented, where the wall temperature does not change preserving the mean temperature of the location during the oscillation. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(2): 129–139, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10126     

An experimental evaluation of R11 as a heat pump working fluid in comparison with some other working fluids

A water to water heat pump specially designed and instrumented for research has been used to determine the actual coefficients of performance of R11 for condensing temperatures in the range 70°C to 104°C. 101 experimental points were obtained and these lie on a smooth curve with a standard deviation of 6.32 per cent. The results are compared with data previously obtained for R12, R22, R12B1 and R114 on the same equipment. R11 with its relatively high critical temperature of 198°C is potentially an attractive working fluid provided that it can be operated in conjunction with a lubricant which does not facilitate thermal breakdown.     

The photochemical heat pipe

The performance of a solar collector system for high temperature heat delivery based on a photochromic reaction is discussed. The system consists of a non-focusing collector and a reactor integrated into a flow system. In the collector, kept close to ambient temperature, the chemical potential of the photochromic system is increased through an endothermic photochemical reaction and is used to drive the reverse thermal reaction taking place in the reactor at a high temperature. No separation of the photoproducts is involved. Accordingly, the highest temperature at which heat can be delivered from the reactor is determined by the maximum attainable photostationary state in the collector and not, as in a conventional flat-plate collector, by heat-loss from the collector to the surroundings. Accordingly, the highest temperature at which heat can be delivered from the reactor is determined by the maximum attainable photostationary state in the collector and not, as in a conventional flat-plate collector, by heat-loss from the collector to the surroundings. The functioning of the device is exemplified by calculations for a model system utilizing the photodissociation of gaseous nitrosylchloride. The results show that it should be possible to build a system which, on a clear day, delivers about 100 W heat at temperature above 200°C for each m² collector area. A tenfold reduction in the radiation flux density of the incident light will only slightly reduce output efficiency.