The progress in environmental investigations such as the analysis of building arrangements in an urban environment could not have been expanded without the use of computational fluid dynamics (CFD) as a research tool. The rapid development of numerical models results in improved correlations to results obtained with real data. Unfortunately, the computational domain discretization is a crucial step in CFD analysis which significantly influences the accuracy of the generated results. Hence an innovative approach to computational domain discretization using polyhedral elements is proposed. The results are compared to commonly applied tetrahedral and hexahedral elements as well as experimental results of particle image velocimetry (PIV). The performed research proves that the proposed method is promising as it allows for the reduction of both the numerical diffusion of the mesh as well as the time cost of preparing the model for calculation. In consequence, the presented approach allows for better results in less time.
Energy efficiency is one of the most important topics nowadays. It is strictly related to the problem of energy demand, energy policy, environmental pollution, and economic issues. Because of the technological development, using more advanced processes in almost every part of industry, and increasing demands both for a high standard of living and simplification of processes, the energy demand is growing. This can be observed, e.g., in the building sector – air conditioning is present in almost every new building and people expect high quality thermal conditions. Energy efficiency can be increased and operation costs reduced by using waste heat in other processes. One of the possibilities is to use sorption chillers to produce cool and desalinated water. The paper presents the results of experimental study carried out on three-bed adsorption chiller with desalination, using silica gel and water as the working pair. The chiller was equipped with plate-fin tube heat exchanger filled with silica gel with a grain size of 0.5-1.5 mm. The laboratory test stand included one evaporator, one condenser, and three separate tanks for water, desalinated water, and brine, respectively. The test stand scheme and description were presented. All results were obtained during a few hours test with stable temperature conditions in the range of: 55-85°C for the heating water.
The interrelation between fuzzy logic and cluster renewal approaches for heat transfer modeling in a circulating fluidized bed (CFB) has been established based on a local furnace data. The furnace data have been measured in a 1296 t/h CFB boiler with low level of flue gas recirculation. In the present study, the bed temperature and suspension density were treated as experimental variables along the furnace height. The measured bed temperature and suspension density were varied in the range of 1131-1156 K and 1.93-6.32 kg/m 3 , respectively. Using the heat transfer coefficient for commercial CFB combustor, two empirical heat transfer correlation were developed in terms of important operating parameters including bed temperature and also suspension density. The fuzzy logic results were found to be in good agreement with the corresponding experimental heat transfer data obtained based on cluster renewal approach. The predicted bed-to-wall heat transfer coefficient covered a range of 109-241 W/(m 2 K) and 111-240 W/(m 2 K), for fuzzy logic and cluster renewal approach respectively. The divergence in calculated heat flux recovery along the furnace height between fuzzy logic and cluster renewal approach did not exceeded ±2%.
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