Byungseon Sean Kim

Predictions and measurements of the stack effect on indoor airborne virus transmission in a high-rise hospital building

Abstract As the viral diseases such as Severe Acute Respiratory Syndrome (SARS) and Influenza A (H1N1) occur in many countries recently, the epidemic of those influenza viruses causes many human casualties. Moreover, the second infection from infected patients particularly within general hospitals frequently takes places due to improperly hospitalized and/or quarantined patients. Accordingly, it becomes a great concern to accommodate safer ventilation system in general hospital wards against such airborne transmitted viruses. It is also a recent trend that many urban general hospitals are designed and constructed as high-rises. If a virus is transmitted through uncontrolled air movement within a hospital and then infected other patients or healthy visitors, it might be impossible to control the spread of the disease. Thus research has been preceded scrutinizing stack effect on the indoor airborne virus transmission in large hospitals by conducting both the field measurement and numerical analysis according to the outdoor temperature and the releasing vertical points of the tracer gas assumed as a viral contaminant. In the field measurement of a high-rise hospital, the indoor airflow was affected by the stack effect of vertical chute of the building. The numerical simulation was verified by comparing its prediction results and the field measurement data. In result, very high possibility has witnessed that the airborne contaminant emitted from the infected patients in the lower floors could be transported to the higher floors through the airflow driven by the stack effect.

Cooling Systems for IT Environment Heat Removal in (Internet) Data Centers

Abstract Internet Data Center (IDC) heat removal is one of the most essential yet least understood of all critical IT environment processes. The cooling of data centers has emerged as a significant challenge as the density of computing equipment increases. In this research, environmental aspects of energy consumption and load-profile were studied through the survey of domestic data centers that need all year round cooling load. The energy-using patterns of cooling system combined with real power density are compared and energy saving effects of data center is reviewed. All cooling systems use CRAC or CRAH units of some kind, which come in various capacities and remove the heat from the room. There are five heat removal methods and two common physical equipment arrangements that can be combined to create ten basic types of cooling systems. Air supply and air return systems each have three and four different configurations that can be combined to create thirteen basic types. An understanding of the many types of cooling/air distribution systems and their attributes can be used to develop guidelines for when each type should be used, and such guidelines are provided in this study for both raised floor and hard floor applications. The design criteria of cooling and air distribution systems were analyzed using quantitative data acquired by surveying 20 multi-megawatt data centers in Korea. It provides the best configurations and design criteria for different IT environments and common practices and equipment options that may increase cooling system availability.

The Influence of Ward Ventilation on Hospital Cross Infection by Varying the Location of Supply and Exhaust Air Diffuser Using CFD

Abstract The SARS virus began to appear and spread in North America and Southeast Asia in the early 2000′s, infecting and harming many people. In the process of examining the causes for the virus, studies on the airborne pathogen SARS virus and the way it spread were carried out mainly in the medical field. In the field of architecture, studies were done on the diffusion of air pollutants in buildings using gases such as CO2, N2O, or SF6, but research on virus diffusion was limited. There were also explanations of only the diffusion process without accurate information and discussion on virus characteristics. The aim of this study is to analyze the physical characteristics of airborne virus, consider the possibility of using a coupled analysis model and tracer gas for analyzing virus diffusion in building space and, based on reports of how the infection spread in a hospital where SARS patients were discovered, analyze infection risk using tracer gas density and also diffusion patterns according to the location and volume of supply diffusers and exhaust grilles. This paper can provide standards and logical principles for evaluating various alternatives for making decisions on horizontal ward placement, air supply and exhaust installation and volumes in large hospitals.

The Indoor Environment Measurement Analysis of Arcade-Type Markets in Korea

Abstract The arcade has been applied to traditional markets to improve their physical environment in Korea. However, thermal discomfort and poor indoor air quality can arise from certain physical characteristics of arcades. This study compares the indoor environments of three traditional markets after their streets have been transformed into arcades and finds the design elements affecting indoor environment. The actual temperature, humidity, air velocity, CO/CO2 and etc. in the arcades were measured. The indoor environment of the arcade was greatly influenced by its shape/size, roof materials and opening for ventilation.

Air Exchange Rate Analysis of The Arcade-Type Traditional Market Using Wind Tunnel Experiment and CFD Model

Abstract Many traditional markets in Korea have been remodeled into arcade-type malls. The openings along the arcade roof are an important design factor that makes the marketplace more comfortable, healthy, and safe. Thus, a wind tunnel test and computational fluid dynamics (CFD) model analyses have been conducted to determine the optimal openings in terms of size and location. A 1/20-scaled model for an arcade-type traditional market was constructed. Experiments were also constructed in a wind tunnel. The test variables were the opening ratios of 100% and 0% and the wind directions of 0° and 90°. In this study, to validate and quantify the air exchange rate in the model, SF6 as a tracer gas was employed. The tracer gas was released into the scaled model and the concentration of the gas within the model was monitored to predict air change rates. The gas was injected at a constant rate during the experiment and its concentration was measured with a precise gas monitor. The wind tunnel experiment was used to validate the CFD model. The results of the wind tunnel experiment were carefully reviewed and compared with the output results of the CFD model. This validated CFD model was used for many analyses, which reviewed various design parameters of the arcade roofs. Through these validations, the optimized opening design is offered.

Predicting Potential Condensation at the Inside Surface of the Glazed Curtain Wall of High-Rise Residential Buildings

Abstract Condensation on the inside surface of the curtain walls of high-rise residential buildings is an important environmental problem in Korea. The purpose of this study is to introduce a new prediction method that can analyze the occurrence hours (days) of inside-surface condensation and compare with several design alternatives under a design stage, utilizing software codes developed by the authors according to the Korean standard, and numerical simulation models such as DOE, esp-r and so on. The method consists of three parts; the first part is on a numerical simulation program that supplies the third part with input data such as weather data, indoor temperature, relative humidity and etc for 8,760 hours (8,760 hours = 1 year). Moreover, it can control building component, air-conditioning system, internal element like people, equipment and so on. The second part is on accurate U-values of the glass center and the glass edge that are received to the third part. The third part is on a software code to 1) determine the occurrence of condensation by the precedent procedure that calculates the inside-surface temperature and the dew-point temperature at the specific time and condition, and 2) sum up the occurrence hours (days) of inside-surface condensation. The application of the method is illustrated with an example of a high-rise residential building.

An interface system for computerized energy analyses for building designers

Abstract This paper describes research on a computer model for building energy simulation. The main goal of this effort has been to provide building designers a better design tool for energy optimization in their building design processes. With the rapid development in computing technology, todays expectation for computer-aided building design (CABD) systems have matured to an advanced level—to the point where designers are open to the idea of computers helping them in the thought process and not just being used to manipulate and represent geometric shapes [ J. Pohl et al., 1992 . A Computer-Based Design Environment—Implemented and Planned Extensions of the ICADS Model. Design Institute Research Report, CADRU-06-92, California Polytechnic State University, San Luis Obispo, CA.]; [ J.A. Clarke, A.D. Irving, 1988 . Building Energy Simulation: An Introduction, Energy and Buildings, 10 (1988), Elsevier, pp. 157–159.]. By its very nature, design is a multidisciplinary and creative activity which encompasses all the relevant areas to be considered during the design process. Thus, the CABD system of today is expected to be a general purpose integrated system, rather than a domain-dependent isolated graphics system [ J. Pohl, L. Myers, A. Chapman, J. Cotton, 1989 . ICADS: Working Model Version 1, Design Institute Research Report, CADRU-03-89, California Polytechnic State University, San Luis Obispo, CA.]. This research effort embodies a prototype interface system for a building energy simulation model (ENERife). This interface system is not a simple layer between user and simulation model, but rather, a general interface strategy to control simulation models and relevant databases to be integrated into CABD. The system includes a user interface module, system interface module, general database handling module, automated input processor, building matrix system, and a result analysis and recovery system.

Smoke Movement and Evacuation Time in the Arcade of a Traditional Market using Numerical Simulation

Abstract This study proposes to analyze the smoke exhausting performance and evacuation time in an arcade of a Korean traditional market. The effect of three types of ventilation opening on smoke exhausting performance was analyzed using the CFD (Computational Fluid Dynamics) method. The ventilation opening delayed the spread of smoke efficiently, and is an important design factor to control smoke movement in arcades. Also the evacuation time was analyzed according to the height of the building and increased significantly with the increase in the number of floors. Given the conditions of the study, the arcade building had to be less than three-stories considering the spread of smoke.

A Study on Thermal Environment and the Design Methods to Save Energy in Small Glass-Skin Commercial Buildings

Abstract To represent the expansion and mutual insertion of spaces by the innate transparency of glass and express new possibility of high technology, some architects apply glass to the outer skin of a building. Though glass-skin buildings economize in the lighting and heating energy in winter, these buildings which are often designed without considering solar gain in the summer and glass conduction in winter, there are many problems such as poor built environment, energy waste and so on. This study aims to provide architects with useful information by comparing with several alternatives, including double skin system etc., to save the energy as well as increase the quality of indoor environment without interfering with the expressed intention which an architect shows to the public by applying glass to the outer skin of building. As results of this study, 1) in the temperature measurements, the surface temperature of glass skin increase by 50°C in small glass-skin buildings. Therefore it makes occupants feel serious discomfort by MRT and cause the increase of cooling load. 2) It is difficult to reduce the cooling load in small glass-skin buildings with considering indoor environment and energy problems rather than heating load. To solve that problem, double skin system is applied to design method with enough intermediate space and shading devices.

Analyses on Thermal Insulation Performance of Earth-Covered Wall for Residential Underground Space by Using a Numerical Simulation Program

Abstract The purpose of this study is to provide the regional insulation criterion of earth-covered walls for underground residential buildings in Korea by using a numerical simulation program. This study was started from the idea that thermal condition of underground residential space must be closer to that of aboveground residential space. According to the result of this study, the underground temperature declines as the depth from the ground level goes deeper and closer to about 9m, and then maintain some steady value from about 9m of the depth. The minimum thermal insulation by depths was deduced by finding the U-factors that make the inside-surface temperature of the earth-covered wall closer to that of the aboveground wall.