Jinkyun Cho

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.

Power and Heat Load of IT Equipment Projections for New Data Center`s HVAC System Design

ABSTRACT:The cooling of data centers has emerged as a significant challenge as the density of IT equipment increased. With the rapid increasing of heat load and cooling system, predictions for electronics power trends have been closely watched. A data center power density projection is needed so that IT organizations can develop data centers with adequate cooling for reasonable lifetimes. This paper will discuss the need for something more than processor and equipment power trend projections which have overestimated the required infrastructure for customers. This projection will use data from a survey of actual enterprise data centers and the ASHRAE projections to formulate a data center server heat load trend projection. Keywords:Data center(데이터센터), Power trend(전력량 경향), IT server heat load(IT서버 발열), Rack server(랙 서버), Blade server(블레이드 서버) †Corresponding author Tel.: +82-2-2145-6999; fax: +82-2-2145-7660 E-mail address: jinkyun.cho@samsung.com 1. 서 론 1.1 연구의 배경전 세계적으로 클라우드 데이터센터 프로젝트가 화두다. 최근 데이터센터의 전력은 IT장비의 기술발전에 따라 가파른 증가추세를 보이고 있으며 이와 동시에 IT서버에서 발생하는 발열도 지속적으로 증가하고 있다. 서버발열이 증가하면 이를 제거해야 하는 냉각시스템의 용량이 증가하고 에너지 사용량도 직접적인 영향을 받는다. 2000년 이후 IDC와 클라우드 데이터센터 등장으로 x86 기반의 다수의 서버가 대량으로 검색서버로 사용되고 있으며 이러한 볼륨서버가 데이터센터의 68% 전력을 소모하고 있다.

Effective Opening Area and Installation Location of Windows for Single Sided Natural Ventilation in High-rise Residences

Abstract This study introduces a plan to improve ventilation effectiveness through an appropriate operable window opening area and partitioning/placement to promote natural ventilation based on unit location and elevation. To predict the natural ventilation performance of a high-rise building, a total of 800 ventilation rate data were calculated according to the unit location, elevation and opening area (2.5%, 5.0%, 7.5% and 10% of the floor area at 8 locations and 25 different elevations) by using a network ventilation simulation. A CFD-based wind tunnel simulation, based on 5 alternative cases, was implemented to analyze the efficiency based on operable window partitioning/placement under the single-sided ventilation condition. The interpretation room is situated in a relatively sheltered location and wind tunnel trials were carried out in order to visualize the resultant local wind pattern around the room for a prevailing wind direction. This investigation also revealed that wind effects can either reinforce or oppose each other. This was verified by tracking the airflow patterns through a room at a range of window positions.

Experimental investigation on hygrothermal behaviour and the surface condensation risk of a data centre

Condensation under the floor slabs of office rooms adjoining data centres is a serious concern because thermal comfort and information and communications technology equipment are both sensitive to high humidity levels. Surface condensation risk depends mainly on the surface energy balance and moisture content of ambient air. This paper describes an evaluation method for assessing condensation risk of indoor environment conditions and the effect of remedial measures and presents a strategy to solve the condensation risk problems using experimental measurements and numerical simulations. The condensation risks due to air temperature and humidity were calculated for two zones between information and communications technology server rooms and office areas. We analysed the structural insulation performance and space cooling conditions, supply air temperature of the information and communications technology server rooms. The change in indoor temperature of non-information and communications technology spaces was predicted to find the cause of the condensation state. The results show that application of floor slab insulation and high supply air temperature by the computer room air-conditioning unit can substantially increase the lowest temperature of the interior surfaces and the temperature factor and reduce indoor relative humidity, thus preventing surface condensation in the non-information and communications technology spaces adjacent to the information and communications technology server rooms.