Ryuichiro Yoshie

Cross Comparisons of CFD Results of Wind Environment at Pedestrian Level around a High-rise Building and within a Building Complex

Recently, prediction of the wind environment around a high-rise building using Computational Fluid Dynamics (CFD) has been carried out at the practical design stage. However, very few studies have examined the accuracy of CFD including the velocity distribution at pedestrian level. Thus, a working group for CFD prediction of the wind environment around a building was organized by the Architectural Institute of Japan (AIJ). This group consisted of researchers from several universities and private companies. In the first stage of the project, the working group planned to carry out cross comparison of CFD results of flow around a single high-rise building model placed within the surface boundary layer and flow within a building complex in an actual urban area obtained from various numerical methods. This was done in order to clarify the major factors affecting prediction accuracy. This paper presents the results of this comparison.

Synergization of Clean Energy Utilization, Clean Technology Development and Controlled Clean Environment Through Thermally Activated Desiccant Cooling System

The global problems of energy supply and demand, climatic change due to artificial global warming, and providing economical and clean human comfortable condition are a complex issue. These problems have become globally political, economical and technological in the center stage of global arena. Utilization of alternative energy resources which are clean and green, hand in hand with the development of alternative clean and green technologies can indeed reduce the global and environmental problems. This paper invasions the idea of harnessing the power of clean energy resources and of developing clean technology for the production of clean environmental conditions. Synergization of clean energy resources, clean technologies and production of clean environment is implemented through the thermally activated desiccant cooling system. The experimental facility is constructed which consists of thermal energy system, desiccant cooling system and the artificially controlled environmental conditions for experimental evaluation purposes. Preliminary experimental investigation is being undertaken to evaluate the performance of the thermal energy system and of the desiccant cooling system. Based on the results, thermal energy system is functioning to its expectations. However, the desiccant cooling system still needs improvement to optimize its cooling capacity. With this study, practical combination of clean energy utilization and of clean technology development for the production of clean environment is possible through proper design and implementation.Copyright

Initial Operation and Performance Evaluation of the Developed Solar Thermal and Electric Desiccant Cooling System

The system in this article was operated for electric heating and thermal storage, thermal storage and desiccant cooling, three days of controlled system operation, and a one-day actual outdoor air conditions operation. Results show that almost 9 h of electric heating is needed to store sufficient thermal energy and that same thermal stored energy is barely enough to support the desiccant cooling operation for only 7 h. It is also shown that excess thermal energy in the tank from the previous days operation cannot support the early-hour desiccant cooling the following day.

Cross Comparisons of CFD Results of Wind and Dispersion Fields for MUST Experiment: Evaluation Exercises by AIJ

In order to apply Computational Fluid Dynamics (CFD) techniques to estimate pollutant dispersion in urban areas, it is important to assess the performance of numerical models used to estimate these phenomena. Recently, the MUST (Mock Urban Setting Test) has often been adopted as a test case for evaluating numerical models for micro-scale urban meteorology. This paper presents the results of model evaluation exercises carried out using MUST based on the Architectural Institute of Japan (AIJ) experience. The results of model evaluation exercises conducted by AIJ are broadly consistent with the results obtained by the COST group. However, the variety of results by each computation can be minimized by setting standard computational conditions. All computations including both RANS and LES show good agreement with wind experiment data. In general, LES cases show comparable accuracy to RANS in predicting U and W. However, LES shows better agreement than RANS in TKE and concentration.

Numerical Evaluation and Optimization of the Combined Solar Thermal and Electric Desiccant Cooling System

Novel solar thermal desiccant cooling system has been developed. Experimental operation and evaluation of the system was conducted. System optimization and parametric investigation are so important for the improvement of system performance. However, inasmuch as evaluation through experimentation is time consuming and very expensive, numerical model is made and developed for the system. The developed model is implemented in TRNSYS program. The model is validated using the experimental data of the system. Based on the result of the numerical evaluation is conducted the area of the installed solar collector area must be reduced to 8m2 . The needed electric heater heating operation is 2 hours. Reduction of the solar collector inclination angle to 30° improved the solar energy collection. Improvement of the desiccant wheel dehumidification rate increased the system total performance. Increasing the heat exchanger (HEX 2) efficiency lowered the supply air temperature with improvement of system performance. Reduction of the system electric energy consumption increased the system electric COP (ECOP). These results of the study are of great importance for the improvement of the design of the developed system, operational procedure, and performance. The relationship and effects of the variables in the study are applicable for other researches seeking the effects of the operational parameters for the solar thermal desiccant cooling system design and processes.Copyright

Advanced Environmental Wind Engineering

The paper gives an overview of the design process for natural ventilation. It concentrates on the technical procedures that are available to the designer. The overall process is discussed in terms of four stages. For the first stage, the factors that determine the feasibility or otherwise of natural ventilation are outlined. In the second stage, the various ventilation strategies are considered. The remaining two stages involve quantitative design procedures. Prior to describing these procedures, the physical mechanisms of natural ventilation are summarised.

FLOW VELOCITY AND SURFACE TEMPERATURE EFFECTS ON CONVECTIVE HEAT TRANSFER COEFFICIENT FROM URBAN CANOPY SURFACES BY NUMERICAL SIMULATION

Mathematical modeling of water quality in rivers is an important tool for the planning and management of water resources. Nevertheless, the available models frequently show structural and functional limitations. With the objective of reducing these drawbacks, a new model has been developed to simulate water quality in rivers under unsteady conditions; this model runs on the Vensim PLE ® software and can also be operated for steady-state conditions. The following eighteen water quality variables can be simulated: DO, BODc, organic nitrogen (No), ammonia nitrogen (Na), nitrite (Ni), nitrate (Nn), organic and inorganic phosphorus (Fo and Fi, respectively), inorganic solids (Si), phytoplankton (F), zooplankton (Z), bottom algae (A), detritus (D), total coliforms (TC), alkalinity (Al.), total inorganic carbon (TIC), pH, and temperature (T). Methane as well as nitrogen and phosphorus compounds that are present in the aerobic and anaerobic layers of the sediment can also be simulated. Several scenarios were generated for computational simulations produced using the new model by using the QUAL2K program, and, when possible, analytical solutions. The results obtained using the new model strongly supported the results from the QUAL family and analytical solutions.

Wind Tunnel Experiment and Large Eddy Simulation of Pollutant/Thermal Dispersion in Non-isothermal Turbulent Boundary Layer

This chapter firstly describes the necessity of validation study of CFD in relation to pollutant/thermal dispersion in urban areas by comparing CFD results with reliable wind tunnel experimental data. The second section explains a technique for simultaneously measuring fluctuating velocity, temperature, and concentration in non-isothermal turbulent layers. The third section introduces examples of pollutant/thermal dispersion experiments in non-isothermal turbulent boundary layers with different atmospheric stability conditions. This measurement technique was used for the wind tunnel experiments. The fourth section reviews various methods for generating inflow turbulence for large eddy simulation and shows some calculated results by large eddy simulation of pollutant/thermal dispersion that target the wind tunnel experiments mentioned above with the experimental data.

Application of Desiccant Heating, Ventilating, and Air-Conditioning System in Different Climatic Conditions of East Asia Using Silica Gel (SiO 2 ) and Titanium Dioxide (TiO 2 ) Materials

This chapter shows the numerical investigation of the developed solar–DHVAC system applied in the East Asian climatic conditions with two different desiccant wheel coating materials—the Silica Gel (SiO2) and the Titanium Dioxide (TiO2). The system was applied in temperate climate (Beijing and Tokyo), subtropical climate (Taipei and Hong Kong) and tropical climate (Manila and Singapore). The study showed that the specification of the solar–DHVAC system varies depending on the climatic conditions. In the comparison of the two materials, it was found that the TiO2 can support lower indoor temperature and humidity ratio than the SiO2 with the same specification of the solar thermal system and DHVAC system. In general, the solar–DHVAC system can provide the required indoor temperature and humidity ratio. However, for the hot and humid climate such as in tropical, large size of the solar thermal system is needed. In addition, higher volumetric flow of air to support the high cooling load is required.

Exergetic Performance of the Desiccant Heating, Ventilating, and Air-Conditioning (DHVAC) System

The developed desiccant heating, ventilating and air-conditioning (DHVAC) system was evaluated using the exergetic method under controlled environmental conditions to determine the performances of the whole system and its components. Percentage contributions of exergy destruction of system components at different regeneration temperatures and reference temperatures were determined. Exergy destruction coefficient of different components at different regeneration and reference temperatures was presented. It was shown that exergetic performances varied with respect to the regeneration and reference temperatures. The exergetic performances based on thermal, electric, total exergy input, first definition and second definition efficiencies were shown. Based on the results, reference and regeneration temperatures affected the determination of the system performances and its components. It was shown that air heating coil (AHC), air fans and desiccant wheel (DW) contributed to large percentage of exergy destruction. Hence, the mentioned components should be given attention for further improvement in the system performances.