The demand for N95 masks (3M) for protection against the new coronavirus COVID-19 has been rapidly increasing at hospitals and medical institutions. However, there is a limit to the increase in its production and the shortage of these products is becoming a serious concern. To this end, the possibility of reusing N95 masks after appropriate decontamination is being discussed. As of June 2020, the decontamination effect of hydrogen peroxide on COVID-19 was confirmed in a small-scale experiment in a small chamber, but there are no guidelines for the large-scale decontamination of large numbers of N95 masks. The specification to upscale for practical operation e.g., treating 10,000 masks/day is not open to the public. Against this background, this study aimed to investigate a large-scale and efficient decontamination method for the reuse of N95 masks by numerical analysis and to provide basic information/data for the development of decontamination guidelines under contract with the Centers for Disease Control and Prevention (US CDC). The overarching objective of this study was to answer to this practical question “How to design a mask decontamination facility using VHP?” by a mathematical model using computational fluid dynamics (CFD). In this paper (Part 1), a typical marine transportation container with 20 feet size and 40 feet size were used as a closed chamber and the container was filled with vaporized hydrogen peroxide (VHP). We performed numerical sensitivity analyses for cases where a large number of N95 masks are decontaminated by filling the container with VHP. The elapsed time from the start of decontamination till a steady-state VHP concentration is reached, the distribution of VHP in the containers, and the adsorption flux of VHP on N95 mask surfaces were precisely analysed to discuss uniform and efficient decontamination methods.

In recent years, there has been a growing interest in energy conservation and reduction of CO2 emissions throughout the life cycle of buildings, and as an effective means, operational improvement using data stored in a building automation and control system(BACS) is widely recognized. Heat pumps for air conditioning systems, which consume the most amount of energy in a building, are expensive building equipment. In addition, they are operated for a long time in the life cycle of the building. Therefore, maintenance to sustain their efficiency is very important. Against this background, this study analyzed long-term BACS data of heat pumps, examined the methods of "Unification of conditions to be able to compare" and "Set standards for comparison" for the degree of aging, and proposed a method that enables a quantitative evaluation. Specifically, Section 1 analyzes the attributes of the heat source equipment within the scope of this study, Section 2 investigates a method to compare the efficiencies of heat pumps in order to unify comparison conditions, Section 3 focuses on standards for comparing the efficiency of heat source equipment, Section 4 evaluates the degree of aging using the proposed method and reflects the findings of Sections 2 and 3, and Section 5 performs a trial evaluation of the maintenance effect using the proposed method. The scope of analysis is BACS data for centrifugal refrigerators (n = 63) and air heat source heat pumps (n = 24) (approximately 11 years on average), which are maintained at the manufacturer's recommended level. As a result, the following findings were obtained. (1) The variability ratio of COP was defined as an index for evaluating the degree of deterioration by a trend analysis of the explanatory variables used in the multiple regression equation. After examining the interval for calculating the variability ratio of COP, it was concluded that an interval of 100 h is appropriate. (2) For the data period used for the multiple regression analysis, it was shown that the data of the entire period was suitable to evaluate the change in the efficiency over time. In contrast, when the period is limited, it becomes easy to detect operation changes within the period. Additionally, this indicates the possibility that this method can be used for fault detection. (3) When evaluating the degree of deterioration using the variability ratio of COP, the effects of explanatory variables varied depending on the model, and the fluctuation range of the variability ratio of COP depended on the fluctuation range of the explanatory variables. (4) As a result of the evaluation, the variability ratio of COP of the centrifugal refrigerators and the air heat source heat pumps was generally within the ± 10% range, and as a median value, no aging was observed within the scope of analysis. (5) In order to evaluate the performance change due to maintenance using the proposed method, a comparison was drawn with a total of 257 maintenance records (brush cleaning, chemical cleaning, O/H). As a result, an approximately 2/3 improvement was observed before and after maintenance. This fact verifies the hypothesis that “there is a possibility that the condition after maintenance is maintained close to the condition at the time of installation, regardless of whether it is good or bad, by performing maintenance”.

Against the background of tight supply and demand in the power system, it is expected that demand response (DR) control will be conducted on the demand side in order to maintain the balance of the system. This study aimed to calculate and estimate the effect of DR control using a detailed simulation to investigate optimal DR control. In this report, an integrated system simulation of air conditioning and building was constructed using the module method that considers each part of HVAC as an individual component. The convergence calculation of water and air circuits based on the bisection method was included in the proposed simulation. Additionally, actual automatic air conditioning control logics were incorporated to enable the reproduction of the control behavior. In particular, the VAV control logic, which is commonly used in commercial buildings, and PI control, which used to control the value of the target variable to the set-point were implemented. In addition, a case study was conducted in a virtual standard floor of an office building with two HVAC systems divided into a parameter zone and an interior zone to compare the reduction in power demand and changes in the indoor thermal environment with respect to the baseline calculated with six assumed DR control categories. As a result, the category of shut down HP was the most effective at reducing electricity demand while simultaneously increasing the PMV index. Moreover, relationships between different control strategies in the same category were established. Finally, it was revealed out that some strategies cannot realize DR control properly during the DR control period. The results confirmed that by using the simulation developed in this study, the effect of DR control can be determined more accurately.

Natural ventilation is effective for saving energy. However, the indoor thermal environment with natural ventilation varies widely by external wind and the position of opening areas. This study aimed to establish the operation of a natural ventilation system in a high-rise office building with voids. This paper presents the distribution of the natural ventilation performance within the office building obtained by CFD analysis, which is evaluated based on the indoor temperature and local mean age of air for each external wind speed, opening area, and position of void.

In recent years, due to increasing global environmental consideration, the demand for further energy saving and promotion of the ZEB transition in newly constructed and existing office buildings is increasing. In this sense, the radiation air-conditioning system has received considerable attention because of it can realize a high level of comfort with a small amount of heat loads. However, there are only a few cases in which the radiant air conditioning system has been used for ZEB modification, and an improvement effect has been shown. Therefore, this study aimed to show the effectiveness of introducing a radiant air-conditioning system, which is an energy saving technology for ZEB conversion, to existing middle and small type office buildings (T building). In this paper, first, the prediction accuracy of CFD analysis was verified by comparison with actual measurement results. Then, we conducted a detailed evaluation of the thermal environment in the current work space and conducted a case study on the assumption that the heat insulation of the skin and the introduction of the radiation air-conditioning system were implemented. Compared with the conventional air-conditioning system, the temperature distribution on the horizontal and vertical surfaces was made uniform, and the temperature difference between the top and bottom was eliminated; thus the effectiveness of the radiation air-conditioning system by renovation was confirmed.

With an increase in the number of extremely hot days, the wet-bulb globe temperature (WBGT) is increasingly being used as an index of health management to prevent heatstroke at outdoor events and construction sites in the middle of the summer. WBGT is composed of natural wet-bulb, globe, and dry-bulb temperatures. However, these parameters are not estimated directly in numerical simulations such as CFD. Therefore, in order to predict WBGT by numerical simulation, it is necessary to convert simulation outputs such as air temperature, humidity, wind velocity, and radiative heat fluxes into natural wet-bulb and globe temperature. However, conversion formulas used in the general air-conditioning field are not based on whether the outdoor environment is greatly affected by solar radiation and wind velocity; therefore, the value of WBGT can be underestimated by using these formulas. In this paper, a conversion method based on the heat balance equation of the thermometer is proposed, and the effect of different conversion formulas on WBGT is discussed. In a case study, the calculation results based on the heat balance equation indicated a higher value of WBGT compared with that obtained using conventional methods.

Influenza viruses and noroviruses are the most common causes of respiratory and gastrointestinal infections. Viruses are tiny protein particles that cannot self-propagate, but they carry genetic materials (DNA and RNA) that can negatively affect humans if they infect them. Viruses are small in size (30-300 nm) and can reach deep into the respiratory tract and into the alveoli. On the contrary, bacteria as well as viruses may also affect the severity of the disease after virus infection. This report summarizes the characteristics of viruses, the route of infection, humidity and airflow around a toilet.