Rie Takaki

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.

Performance Test of Desiccant Heating, Ventilating and Air-Conditioning System by Using Multiple Tracer Gas Dilution Method

The desiccant-based air-conditioning system consists of many heat and mass transfer components operating together with air fans. The performance test using the multiple tracer gas dilution method is important for knowing the internal and external flow rates, including the air leakages. The results of the test show the actual internal air flow rates and the sources of air leakage, and also show the interaction of air in the air-conditioned lecture room and in the mechanical room. The performance test using the multiple tracer gas dilution method in air flow and air leakages is important for a detailed evaluation of any air-conditioning system such as this desiccant-based one.

Effect of ventilation strategies for removing indoor house dust: An experimental and simulation study

House dust includes the mold spores or corpses and feces of the mite, among other things, which would cause allergies, asthma, and unspecific hypersensitivities. The possibility of having an allergic reaction to house dust is particularly high for children. In this study, experiments and simulations were performed to study the flow and diffusion fields affected by different location and shape of outlets. Two kinds of ventilation strategies were considered, i.e., ceiling exhaust and floor-level slit exhaust. In the experiments, for the two cases, the characteristics of airflow within the whole room are generally similar except for the airflow close to the outlet. Riboflavin particles were used as the house dust; the amount of particles in the ceiling exhaust was a little larger than that of the slit exhausted after particles decreased to the same level as the background. Flow and diffusion fields were investigated by computational fluid dynamics (CFD) simulations. The characteristics of airflow are similar for both experimental and simulation results. The particles with a diameter of 0.5–3.0 μm in the experimental data and calculated values showed good agreement. It was concluded that floor-level slit exhaust ventilation strategy produced less house dust in the whole room than the ceiling exhaust did.

A Study on Ventilation Systems for Removing Indoor House Dust

Abstract This study evaluated various ventilation strategies for efficiently removing house dust in the indoor environment. Experiments and simulations were performed to study the flow and diffusion fields that are affected by different locations and shapes of outlets. In this study, two kinds of ventilation strategies were considered i.e. ceiling exhaust and slit exhaust. In each case, experimental measurements showed that the characteristics of airflow within the whole room are generally similar except for airflow close to the outlet. CFD flow field and diffusion field simulations were also made. The CFD characteristics of airflow were similar to the experimental results. In the simulations, the volume–average concentration of house dust within the whole room decreased gradually. From the results, a conclusion can be drawn that the volume–average concentration of house dust within the whole room is lower in the case of slit exhaust than ceiling exhaust. After a ventilation period of 30 minutes the CFD results showed removal efficiencies for the ceiling exhaust and slit exhaust of 15% and 26% respectively at a low air change rate of 0.5 h–1, while the removal efficiencies of ceiling exhaust and slit exhaust are 51% and 57% respectively at a high air change rate of 2.5 h–1.

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.

In-Situ Performance Evaluation of the Desiccant Heating, Ventilating, and Air-Conditioning System Using Multiple Tracer Gas Dilution Method

The desiccant heating, ventilating and air-conditioning system (DHVAC) consists of many heat and mass transfer components operating together with air fans. The performance test using the multiple tracer gas dilution method is important for knowing the internal and external flow rates, including the air leakages. The results of the test show the actual internal air flow rates and the sources of air leakage, and also show the interaction of air in the air-conditioned lecture room and in the mechanical room. The performance test using the multiple tracer gas dilution method in air flow and air leakages is important for a detailed evaluation of DHVAC.

Study on Distribution and Deposition of House Dust by Different Ventilation Systems in a Full-scale Residential Room

Abstract House dust contamination has recently become an important issue in the residential indoor environment. This study evaluated ventilation systems for removing house dust efficiently in a full-scale residential room. Experiments and simulations were performed to investigate diffusion and deposition of house dust by different ventilation systems. Riboflavin particles were used as the house dust. Two kinds of ventilation systems were considered, namely ceiling exhaust and slit exhaust. In the experiments, whether high air change rate (2.5 ac/h) or low air change rate (0.75 ac/h), the amount of house dust in the ceiling exhaust was a little larger than that of the slit exhaust after house dust decreased to the same level as background. Diffusion fields were investigated by CFD simulations, the house dust with diameter of 0.5 ~ 3.0 μm in the experimental data and calculated values showed good agreement. From the data, it is shown that the removal efficiency of the slit exhaust was 5.3% and 11.1% higher than the ceiling exhaust after two hours of operation at 0.75 ac/h and 2.5 ac/h, respectively. Based on the results of this study, it is concluded that the house dust in the full-scale residential room using a slit exhaust ventilation system is lower than ceiling exhaust at both high and low air change rates.

Measurement of Ventilation Airflow Rates of 39 Houses by Three Different Methods

Abstract This paper reports on the measurement results of ventilation rates in existing occupied houses in the northern region of Japan. A total of 61 measurements were made over a period of 4 years on 39 houses. Some houses were measured once a year over the four years investigation period. The ventilation systems equipped in some of the investigated houses were improved during the course of this investigation period. The effect of the improvement on ventilation airflow volume was reported. The ventilation rates were measured by three different methods, namely constant concentration method, measurement of airflow rate at inlets/outlets and passive homogeneous emission method. Through this investigation, the measurement results indicated that the ventilation rate was insufficient in many houses and some of the ventilation systems were not operated properly. In addition, the amount of air leakage in the house envelope and the amount of air change due to occupant behaviour were also determined.