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[en] In a typical solar water heating system, cold water is replenished into the storage tank as soon as the load is served. However, it is possible to determine the water replenishment profile (i.e., the quantity of the cold makeup water to be supplied to the storage tank over a day) that optimizes the overall system. In this paper, the effect of water replenishment on the system sizing is studied and a novel strategy for water replenishment is proposed to improve the design and performance of solar water heating systems. Based on an analytical technique, an approximate water replenishment profile is proposed to size a solar water heating system near-optimally. The problem is analyzed using a methodology called design space approach. Design space of a solar water heating system identifies all possible and feasible designs on a collector area vs. storage volume diagram. For illustration of the proposed methodology, an example problem is solved. It is observed that the annualized system cost can be reduced by 13.7%. For the cost-optimal system configuration, a reduction of 12.7% in the collector area and 10.2% reduction in the storage volume are observed. The proposed methodology is particularly important and advantageous for large commercial and industrial solar water heating systems
[en] The title survey was carried out to acquire a detailed overview of the activities of Dutch energy utilities on the application of solar energy, in particular the use of solar water heaters. This report contains a summarized overview of the survey results. The results for each energy utility are published in a separate appendix, which is not available to the public. 1 fig., 10 tabs., 3 appendices
[en] Solar plants are increasingly used not only for hot tap water heating but also for the assistance of space heating. These plants produce much more energy in summer than needed, which often results in stagnation. Because of stagnation-temperatures of todays selective collectors up to 200 deg. C, the collector fluid evaporates. In several plants a high noise level and a vibration of the plant during this evaporation phase is reported. This is due to the occurrence of water hammers in the system, when liquid collector fluid passes areas where the fluid was already evaporated and superheated. The remaining vapor bubbles deflate rapidly and the liquid phases collide with high velocity, which results in a rapid pressure increase. This paper describes the theory of condensate-induced water hammers and conditions of solar plants, under which this can happen. A simulation model for the evaporation phase of the collector is presented to give a deeper understanding about the influences of solar radiation, the size of the tubing, and the size of the expansion device on the process of the evaporation. Three hydraulic layouts of the collector area are discussed for there possibilities producing water hammers. (au)
[en] This article reports on the UN Environment Programme's (UNEP's) work in supporting the banking and financing sector by creating clean energy finance markets in developing countries. Details are given of the shifting of cash markets to credit, financing solar home systems in India, solar thermal lending in Tunisia, the financing of hotel based solar water heating in Morocco, and the Green Village Credit initiatives in the Yunnan province of China. The importance of providing banks with information needed to gain awareness and experience of renewable energy systems is stressed. The fundamentals of a bank engagement programme, financial catalysts, structuring market oriented approaches, and linking bank lending to policy making are discussed along with the need to shift to credit enhancements to help banks set up their first loan portfolios
[en] The results of numerical research on the determination of the temperature value of the internal surface of the heat-removing channel (HRC) walls of the light-absorbing heat-exchange panels (LAHPs) with the tubeon- sheet and thin-parallelepiped form of flat-plate solar water-heating collectors (FPSWHCs) are presented. The research method is based on compilation of the system of the balance equations for the light-absorbing plate (LAP) and HRCs of the LAHPs of the studied types and their designs with respect to the desired parameter. A practical example of calculation of the determination of the temperature value of the internal surface of the HRC wall of the tube-on-sheet LAHP, where the results of experimental research on the determination of the specific thermal efficiency of the mean-quality FPSWHC in full-scale terms, as well as laboratory and numerical research on determination of the optical and thermotechnical indicators of the copper tube-on-sheet LAHP.
[en] Several sites were visited to monitor stonemason exposure to respirable crystalline silica (RCS), inhalable dust and respirable dust. At all sites, exposure to RCS exceeded the Workplace Exposure Limit of 0.1 mg/m3 8-hour TWA. There was therefore a continuing high risk of workers developing silicosis unless the appropriate measures were instigated to prevent or control exposure. Exposure control was ineffective at all sites e.g. water wall extraction systems were not well designed. There was evidence that foreign workers were at a greater exposure risk. But even with appropriate controls to mitigate exposure to RCS it may not be possible to sustain exposure to below 0.1 mg/m3 8-hour TWA without on-going HSE intervention.
[en] The paper presents the results of numerical investigations for determining the relationship between the replacement factor of heat load of passive solar heating passive systems and the thermal resistance of their collecting-accumulating walls. The calculations are carried out by using average daily meteorological information. (author)
[en] An instability theoretical model for multi-channel system had been developed by building one-dimensional homogeneous model and adopting nonlinear analysis for two-phase flow in vertical single pipe, supplied by Clausse and Lahey. With the same parameters as the experiment, two-phase flow density wave oscillation in parallel inclined inner ribbed pipes was analyzed and solved in this paper. The variation of the working fluid inlet velocity perturbation with time was found using the time domain method. The criteria of density wave oscillation were defined according to the convergence or divergence of the velocity. The pulse cycle of calculated results was mostly between 5 and 16 seconds, which was quite similar to the data between 7 and 19 seconds in the experiment. It is shown that the calculated results have a good agreement with the experimental data. Therefore, the method can be used to determine whether the incidence of density wave instabilities. It can also provide a reference for the safety parameters of the water wall in the supercritical pressure boiler. (authors)
[en] Supercritical Circulating Fluidized Bed (CFB) boiler becomes an important development trend for coal-fired power plant and thermal-hydraulic analysis is a key factor for the design and operation of water wall. According to the boiler structure and furnace-sided heat flux, the water wall system of a 600 MW supercritical CFB boiler is treated in this paper as a flow network consisting of series-parallel loops, pressure grids and connecting tubes. A mathematical model for predicting the thermal-hydraulic characteristics in boiler heating surface is based on the mass, momentum and energy conservation equations of these components, which introduces numerous empirical correlations available for heat transfer and hydraulic resistance calculation. Mass flux distribution and pressure drop data in the water wall at 30%, 75% and 100% of the boiler maximum continuous rating (BMCR) are obtained by iteratively solving the model. Simultaneity, outlet vapor temperatures and metal temperatures in water wall tubes are estimated. The results show good heat transfer performance and low flow resistance, which implies that the water wall design of supercritical CFB boiler is applicable. - Highlights: → We proposed a model for thermal-hydraulic analysis of boiler heating surface. → The model is applied in a 600 MW supercritical CFB boiler. → We explore the pressure drop, mass flux and temperature distribution in water wall. → The operating safety of boiler is estimated. → The results show good heat transfer performance and low flow resistance.
[en] In order to solve the problem of removing inhaled particle caused by the combustion source, the dynamics characteristics of the inhaled particle in additional temperature field have to be studied. The dynamics characteristics of the inhaled particle in temperature field are measured in designed and processed a rectangle experiment channel by the PDA instrument. This method is visual. The dynamic characteristic of the particle at 0.15 mm near by water wall surface in boundary layer can be measured through the direction change of beam of PDA light. The movement rules of the inhaled particle in the additional temperature field are obtained through the experiment. The experiment results show that the thermophoresis force has strong influence on the particle which diameter is about 6 μm and the experience formulas are put forward to calculate the thermophoresis deposition efficiency. The thermophoresis deposition efficiency formulas obtained from this experiment is consistent with Batchelor and Shen formulas. The research shows that the PM2.5 thermophoresis deposition efficiency is direct proportion to the temperature ratio between the inlet temperature and the water wall surface but is not the temperature difference in the rectangle channel