No abstract

Full-scale metal solar collectors and solar collectors fabricated from polymeric materials are studied in present research. Honeycomb multichannel plates made from polycarbonate were chosen to create a polymeric solar collector. Polymeric collector is 67.8% lighter than metal solar collector. It was experimentally shown that the efficiency of a polymeric collector is 7-14% lower than a traditional collector. An ecologically based Life Cycle Assessment showed the advantages of the application of polymeric materials in the construction of solar collectors.

Full-scale traditional metal solar collectors and solar collector specimens fabricated from polymeric materials were investigated in the present study. A polymeric collector is 67.8% lighter than a traditional metal solar collector, and a metal solar collector with transparent plastic covering is 40.3% lighter than a traditional metal solar collector. Honeycomb multichannel plates made from polycarbonate were chosen to create a polymeric solar collector. A test rig for the natural circulation of the working fluid in a solar collector was built for a comparative experimental investigation of various solar collectors operating at ambient conditions. It was shown experimentally that the efficiency of a polymeric collector is 8-15% lower than the efficiency of a traditional collector.

Full-scale metal solar collectors and solar collectors fabricated from polymeric materials are studied in present research. Honeycomb multichannel plates made from polycarbonate were chosen to create a polymeric solar collector. Polymeric collector is 67.8% lighter than metal solar collector. It was experimentally shown that the efficiency of a polymeric collector is 7-14% lower than a traditional collector. An ecologically based Life Cycle Assessment showed the advantages of the application of polymeric materials in the construction of solar collectors.

Разработаны схемные решения тепло-массообменных аппаратов с подвижной псевдоожиженной насадкой «газ-жидкость-твердое тело» для испарительного охлаждения сред (испарительные охладители воды – градирни и охладители воздуха) и многофункциональных солнечных систем тепло- хладоснабжения и кондиционирования воздуха, основанных на открытом абсорбционном цикле с непрямой регенерацией абсорбента. В осушительном и охладительном контурах солнечных систем также используются тепло-массообменные аппараты с подвижной насадкой. Решения для тепло-массообменных аппаратов с подвижной насадкой «газ-жидкость-твердое тело» разработаны в нескольких основных вариантах, в частности, с возможностью размещения теплообменника непосредственно в объеме псевдоожиженного слоя насадки: испарительные охладители воздуха непрямого типа (НИОг) и испарительные охладители жидкости (НИОж) охладительного контура солнечных систем; абсорбер-осушитель воздушного потока и десорбер-регенератор осушительного контура солнечных систем. Выполнен цикл экспериментальных исследований особенностей псевдоожижения подвижной насадки как для варианта со свободным подвижным псевдоожиженным слоем насадки, так и в варианте с размещением теплообменника непосредственно в объеме псевдоожиженного слоя насадки. Исследовалось влияние высоты стационарного слоя элементов насадки, геометрических параметров опорно-распределительной решетки, начальных параметров воздушного потока, поступающего в тепло-массообменный аппарат. На основе цикла теоретических и экспериментальных исследований выработаны практические рекомендации по определению оптимальных геометрических параметров основных элементов аппаратуры и режимных параметров работы тепло-массообменных аппаратов в автономном режиме и в составе солнечных абсорбционных систем.

Concerning the construction of a solar water-thermal collector – the analysis of the applied polymeric materials has been performed in relation to manufacturing of its main parts – the heat absorber and the transparent cover. The use of polymers in the construction of the solar water-thermal collector allows one to lower the manufacturing costs, make the collector light-weight and reduce its price. An analytical review based on the domestic and foreign research and development, published in scientific journals over the past few years, which the authors hope shall be a useful reading in the design-engineering departments responsible for constructing the polymeric solar collectors is the goal of the present work, along with the comparative analysis provided further on the collectors’ efficiency for making a choice of material and the solar energy capture systems’ testing methodology. As the fundamental direction of further improvement of the polymeric solar collectors, the authors aim at: elimination of the air gap between the heat absorber and the transparent cover, leading to construction of a monoblock solar collector; optimization of the heat absorber’s and the transparent cover’s flow channels in solar water-thermal collectors, which concern their compages as well as the size and geometry of the hydraulic collector; optimization of the transparent cover’s channels size as the means of air circulation, which lowers summary heat losses in solar water-thermal collectors; studying the evenness of the heating agent’s distribution in the heat absorber’s channels out in the field, to pursue the improvements in efficiency of the solar water-thermal collectors, and to avoid the heat shock of a solar water-thermal collector’s structural elements upon uneven warming-up. In the present work the analysis has been performed on the summary heat losses (convective and radiation losses realized from the solar collector’s heated-up elements) which depend on a polymeric solar collector’s operating conditions and geometrics as well as on a solar energy capture system’s external environment; a tryout facility has been built, affording a comparative analysis of various solutions; and the main objectives of further research in the field of polymeric solar collectors, particularly, the questions on improvement of their assembly realisation, and reliability of multifunctional solar energy capture systems have been formulated.

No abstract

Low-temperature nitriding of steels is usually carried out in the temperature range of development of reversible temper brittleness. The holding time at these temperatures significantly exceeds the holding time during normal tempering, which can negatively affect the properties of steel. The article considers theories that explain the processes occurring in steels in the temper brittleness temperature range. It may be concluded that views linking the embrittlement of steel with alloying elements such as nickel in its content are not confirmed by the experiments; at the same time ideas based on classical views about the diffusion of chemical elements explain the processes in steel better.