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  • Open access
  • 8 Reads
An Exergy Based Approach to Noise Prevention in Wind Turbines: Concept and Preliminary Assessment
Unsustainable human activities and practices are polluting water supplies and emitting to the atmosphere greenhouse gases as well as compounds that erode the earth\'s protective ozone layer. The potential impact on human health and economic costs associated with global warming have motivated scientists and engineers to seek sustainable technologies. One such technology is the wind turbine, which harnesses energy from the wind. However, a significant hindrance preventing the widespread use of wind turbines is the noise they produce. This study examines flow over an object and the consequent noise generation produced by this flow-structure interaction. Flow over a cylinder has been chosen as the benchmark. The aim of this study is to correlate three main characteristic parameters of the system, namely, the generated sound pressure level, the exergy destroyed, and the normal flow velocity). The main motivation for this work is to relate the exergy destruction to the noise generated in the flow to improve understanding and to provide a correlation can be utilized to reduce or minimize the noise of wind turbines.
  • Open access
  • 7 Reads
Modelling Thermally Interacting Multiple Boreholes with Variable Heating Strength
Published: 07 November 2012 by MDPI AG in The 2nd World Sustainability Forum session Environmental Sustainability
Various heat transfer models are reported for vertical ground heat exchangers, and several basic analytical and numerical models of vertical heat exchangers are described and compared, and recent developments are discussed. To examine the effect of temperature rise in the soil surrounding a vertical ground heat exchanger on the performance of the ground heat pump, the heat transfer model that represents the temperature rise and heat flows outside the borehole is often coupled to the models inside the borehole via the borehole wall temperature. This temperature is an important factor that affects the heat delivery/removal strength of the system to/from the ground. In the current study, the results of a semi-analytical model that couples a model outside the borehole with one inside the borehole taking into account the transient borehole wall temperature is described. The results of this model for a constant borehole wall temperature are compared with those for a transient one with a numerical model. It is shown that transient borehole wall temperature results in more accurate temperatures for the circulating fluid flowing to the heat pump.