In a parallel type temperature-stratified thermal energy storage tank, connecting holes are provided on the tank partition walls to equalize the ratios of the stored heat to the heat storage capacity among the parallel connected tanks. In this study, we used a mixing model for the parallel type temperature-stratified thermal energy storage tank, and verified it experimentally using two parallel connected storage tanks. The results of calculating the tank water temperature profile uniformly using 0.70 as the discharge coefficient of the connecting hole, agreed well with the experimental results, although the discharge coefficients identified by the experiments ranged from 0.55 to 0.85. A relational equation for the connecting hole conditions and non-dimensional water density difference in between parallel connected tanks was obtained after theoretical analysis. In order to verify the validity of the connecting hole design method using the relational equation and to clarify its scope of application, simulations of parallel connected tanks were conducted using the mixing model. We propose a design method for the connecting hole based on an acceptable difference in the non-dimensional heat storage amount between parallel connected tanks.
In preperation for real-time pricing in the future, we consider a control method to adjust the trade-off between economics and room temperature comfort of the building multi-type air conditioners installed in the entire building. In this control method, a candidate permutation of the power limitation command given to each outdoor unit is searched, but the search space increases exponentially with the number of outdoor units. The calculation time becomes a problem in large-scale facilities with several dozen outdoor units. In this research, we propose a new search method for large-scale permutation based on practical judgment using the distribution characteristic of the search space and a parallel search algorithm. A search simulation is performed using this method, and the facility scale at which the proposed method can be applied considering both economic constraints and system constraints is clarified. As a result, it is shown that RTP adaptive control using the proposed method is possible for up to 30 outdoor units, a total floor area of 4000m<sup>2</sup> to 8000m<sup>2</sup>, and buildings with 5 to 10 stories. It is also shown that the search for the large-scale permutation can be completed within 98% of the total time, i.e., within 30 seconds of the search time limit’ by the proposed method, and the control cycle is established.
In recent years, while using less water to flush toilets has been encouraged, there have been concerns about the degradation of the carrying performance of horizontal drainpipes and stagnant wastewater in the pipes. In this experimental study, horizontal drainpipes having pipe diameters of 75A, 100A, 125A and 150A are used, and different factors such as pipe gradient, flow rate, and waste type are applied under various conditions to the pipes, while small amounts of water are drained through the pipes to deliberately degrade the carrying performance thereof. The study aims to identify the influence of these factors on the carrying performance and to acquire some basic knowledge from the experiment results, which is conducive to the design of horizontal drainpipes. Using a hypothetical case where a water-saving toilet is connected to a drainage pipe system, and clean water and wastewater are drained separately at low volumes and low flow rates, this report clarifies the flow-velocity relationship between clean water and the wastewater as well as the drainage conditions that keep wastewater flowing again after the wastewater has stagnated in the horizontal drainpipe. Moreover, by applying some of the hardest piping conditions that affect the carrying performance, the influence of two important factors, namely low drainage flow rate and pipe gradient, on the carrying performance are examined.
Solar chimney, which is a natural ventilation device that enhances the stack effect due to solar radiation has been studied for decades, by using an experimental method, a Computational Fluid Dynamics (CFD) method, and a multi-zone model method. However, the field measurement data of actual buildings with a solar chimney seem to be insufficient. The aim of this study is to accumulate the knowledge about solar chimneys, and to establish a prediction and estimation method for the natural ventilation performance. The performance of the solar chimney at an actual city hall with a natural ventilation system is presented in this paper. The airflow rate and air change time per hour (ACH) were estimated in the spring of 2018, and were compared with the values predicted during the designing phase; it was found that the estimated ACH was approximately 10 h<sup>-1</sup>, which was 1.5 times the predicted value. The airflow rate and ACH were averaged each month; in April 2018, the averaged airflow rate through the solar chimneys was 1,424m<sup>3</sup> min<sup>-1</sup>. In addition, the frequency distributions of ventilation rate through the solar chimney, i.e. the usage level of the solar chimney were obtained.