In this work, numerical simulation calculations were performed to investigate the minimum ground temperature that occurs when extracting thermal energy in a horizontal ground heat exchanger system in the Central European climate. The influence of ground thermal conductivity, heat flux extracted from the ground, periodic interruptions in the operation of the heat exchanger, periodic supply of heat energy to the ground, relative humidity of the ambient air, evaporation rate coefficient, and convective heat transfer coefficient on the ground minimum temperature were investigated. Based on the simulation, it was found that the high value of ground thermal conductivity favorably affects the operation of the installation with a ground heat exchanger. Both the reduction of the maximum heat flux taken from the ground, as well as periodic interruptions in the operation of the exchanger effectively protects the ground against excessive cooling. Further, it was found that heat supply to the ground in summer only slightly raises its minimum temperature, as well as the decrease of the relative humidity of the ambient air and evaporation rate coefficient. The change of the convective heat transfer coefficient has no significant impact on the minimum annual ground temperature.
Application of circulating fluidized bed boilers in the fuel combustion processZastosowanie kotłów z cyrkulacyjną warstwą fluidalną w procesie spalania paliw Abstract The combustion of fuels plays an important role in the field of industry and power engineering. Nowadays, a lot is being done to reduce the industry' s interference in the environment, due to ecological considerations. Not only is the fluid technology environmentally friendly, but also it is a convenient method of energy production from wide range of fuels. The article presents a summary of the most significant events in the history of fluidized bed boilers, there is also a description of construction and operation of a circulating fluidized bed boiler and its comparison with technologically similar bubbling fluidized bed boiler. The usage of diverse types of fuels is discussed and compared. Special emphasis is placed on the application of fluidized bed boilers in Polish industry.Keywords: fluidized bed, combustion, circulating fluidized bed boiler, CFB boiler Streszczenie Spalanie paliw odgrywa ważną rolę w dziedzinach przemysłu i inżynierii energetycznej. Obecnie, dokonuje się wielu starań, mających na celu zmniejszenie wpływu przemysłu na środowisko, ze względu na względy ekologiczne. Technologia fluidalna jest nie tylko przyjazna środowisku, ale także jest dogodną metodą produkcji energii z szerokiej gamy paliw. Artykuł przedstawia kilka najważniejszych wydarzeń historycznych, które przyczyniły się do rozwoju technologii fluidalnej. Umieszczono w nim opis konstrukcji i działania kotła z cyrkulacyjną warstwą fluidalną, a także jego porównanie z podobnym pod względem technologicznym kotłem z bąbelkową warstwą fluidalną. Opisane i porównane jest użycie różnych typów paliw. Szczególny nacisk położony jest na użycie kotłów fluidyzacyjnych w polskim przemyśle.Słowa kluczowe: złoże fluidalne, warstwa fliudalna, spalanie, kocioł z cyrkulacyjną warstwą fluidalną, kocioł CFB
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