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New materials and structures are applied in order to maintain the engineering products more and more efficient. Different types of thermal analysis/modelling of such materials and structures are also needed for the proper planning or design. The thermal analysis/modelling processes are supported by many commercial codes but in some cases, the experts might have applied a self-developed method also. The success of the analysis/modelling depends on many factors, but the basis is the correct application of the heat conduction theory which is more important in case of transient thermal processes. As the used tools are more and more powerful, the users pay less attention to the theory background, according to the author experience. It seems that the long tradition of the inconsistent application of the temperature-dependent thermal diffusivity is continuing, even strengthened by the increased availability of data of the temperature-dependent thermal properties. Regarding the origination of the thermal diffusivity, this might lead to the misinterpretation or misunderstanding of the nonlinear heat conduction problem solution procedures. This paper calls attention to avoid this, shows what kind of mistakes might occur related to this widely observable practice, summarizes the proper application and interprets where and how one could find room for the temperature-dependent thermal diffusivity. [ABSTRACT FROM AUTHOR]

From both environmental and energy-saving points of view, solar heating and cooling systems have recently proven themselves in the commercial world as the environmentally friendly and sustainable energy systems which can replace the systems powered by conventional sources of energy such as fossil fuels and electricity. In the present paper, the research contributions conducted on solar absorption cooling systems, integrated with different auxiliary energy devices, are comprehensively reviewed and discussed. Also, various cooling systems integrated with solar technologies, i.e., flat-plate collector, evacuated tube collector, compound parabolic collector and parabolic trough collector, are reviewed. The survey and comparison are carried out in terms of some crucial parameters such as coefficient of performance, annual energy consumption and payback period. Further, this work briefly presents and discusses some possible opportunities for future works from the efficiency viewpoint. [ABSTRACT FROM AUTHOR]