Review on the European Strategies for Energy-Efficient Buildings
Reduction of the energy consumption in the building stock is an essential part of the sustainability strategies of the European Union on economy, environment and Climate Change. Operation and use of the residential and tertiary sector buildings are responsible for roughly 40% of the total final energy consumed in its Member States. This demand is supplied mainly from the imported fossil fuels. Energy-efficiency of buildings has grown to one of the main mechanisms in pursuits to alter the negative trends of growing consumption that would lead to an increase of the import dependence and increase of greenhouse gas emissions. In recent years, the European policy has shown signs of success but the targets seem to have been set as too ambitious. A review on the energy-efficiency strategies is presented in this paper in order to propose an explanation for the delay. It has been identified as insufficient links between statistics on the energy supply and the energy demand in various parts of the existing building...
The effect of a thin foil on the heat losses behind a radiator
This thesis work is the study of the effect of an aluminium foil on the losses that produced by a radiator, situated under a window, through the wall behind it. The reason behind this topic is due to the energy problem and the different goals that governments have set up to try to reduce the use of energy. For example, more specifically a Swedish national goal is to decrease the energy use of the built stock with 50% by 2050. For this purpose, an experimental set-up was built in the University of Gavle, Sweden. The arrangement was composed by a radiator and a window facing a climate chamber. A total of twenty-one temperatures and two heat fluxes in the exterior wall were measured in the set-up. Ten different measurement scenarios with different radiator temperature, 40°C, 50°C and 60°C; two different distance between the radiator and the wall, 5 and 9 centimetres and with and without the aluminium foil, were performed. With the experimental results, a CFD model was validated. Two different models were done, first a 2D model and afterwards a 3D model. For the turbulence, the chosen model was standard k-e model. There were 54 cases simulated with the 2D model and the 3D model was used just for validation. The cases had different variables such as radiator temperature, outdoor temperature and wall insulation. With these cases, analysis of the effectiveness of the presence of an aluminium foil behind the radiator is performed to evaluate if there is a significant reduction of the losses. The results showed with both methods that the aluminium foil reduces the losses of the wall behind the radiator. The savings varied depending on the boundary conditions of the case and it were obtained a maximum of 4% and a minimum of 1,3%.
Investigation of scatter radiation of non-circular X-ray scan trajectories
Modern interventional X-ray devices are highly maneuverable and allow complex 3D imaging trajectories. New scan trajectories enable not only optimized object sampling but also introduce new approaches for dynamic 3D imaging. In this paper, we investigated the scatter radiation of two different scan trajectories. The scatter radiation was sampled by a rail setup with dosimeters at defined positions. After data analysis, contour maps were generated which show for four exemplary heights the scatter radiation distribution. The alternative scan trajectory showed smaller dose exposures at heights correlated to upper torso and head areas of a model physician. Keywords—Image acquisition, alternative scan trajectory, circular tomosynthesis, scatter radiation distribution