PERFORMANCE EVALUATION OF PERSONALIZED VENTILATION PERSONALIZED EXHAUST (PV-PE) SYSTEM IN AIR-CONDITIONED HEALTHCARE SETTINGS YANG JUNJING (Bachelor of Eng., Tongji University; Master of Science, University of Reading) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF BUILDING NATIONAL UNIVERSITY OF SINGAPORE 2013 Declaration i Acknowledgements I would like to acknowledge and extend my heartfelt gratitude to the following individuals who have made the completion of this thesis possible. Firstly I would like to express my deepest acknowledgement to my supervisor Professor S.C. Sekhar for his vital guidance, constant support, valuable advice and encouragement. He was also very accommodating in allowing me freedom to pursue my interests which were out of my research scope. I feel lucky to have been one of his PhD students. I am also grateful to my thesis committee members: A/P Cheong Kok Wai, David, and A/P Benny Raphael, whose doors are always open, for freely sharing with me their valuable knowledge, experience and expertise on any issues related to my research. I would like to thank Professor A.K. Melikov from DTU for his suggestions and comments for the Qulify Exam Report of my PhD study which gives me ideas for experimental design. I want to thank Ms.Wu Wei Yi, Mr Zaini bin Wahid, Mr. Tan Cheow Beng, Mr. Tan Seng Tee for assisting with the laboratory equipment and instruments during the experiments in my research. I am grateful to Dr. Jovan Pantelic and Dr. Wang Junhong for sharing their knowledge about CFD simulation. I also wish to thank Dr. Li Ruixin and Huang Shuguang for sharing their experience during the experiments. Gratitude goes out to the National University of Singapore for funding this effort and providing much needed apparatus during the course of this thesis. ii Lastly, I would like to express my sincere gratitude to my husband, my daughter and my parents for their understanding, support and unconditional love. Singapore, Final submission May 2014 Yang Junjing iii Contents   Word did not find any entries for your table of contents. In your document, select the words to include in the table of contents, and then on the Home tab, under Styles, click a heading style. Repeat for each heading that you want to include, and then insert the table of contents in your document. To manually create a table of contents, on the Document Elements tab, under Table of Contents, point to a style and then click the down arrow button. Click one of the styles under Manual Table of Contents, and then type the entries manually. iv Summary Severe Acute Respiratory Syndrome, H1N1 and other flu-related outbreaks in recent times have highlighted the issue of short-range aerosol transmission between healthcare workers and the patients. Concerns about the ventilation system design in healthcare centres in the field of control of airborne transmission of infection have become topical and important. Personalized Ventilation (PV) has been introduced in indoor air distribution for more than a decade and the concept involves delivering 100% conditioned outdoor air directly to the occupant breathing zone. The primary aim of a PV system is to supply fresh air to the breathing zone to enhance Inhaled Air Quality. At the same time, it can also be seen as a solution to prevent the spread of contaminated air. Whilst a conventional PV system would fulfil most of these requirements, it may not be able to adequately prevent the spread of contaminated air as the PV air would go past an infected person and mix with the room air. In order to maximize the advantages of a PV system in delivering personalized air to the breathing zone, it is interesting to explore the use of a personalized exhaust (PE) device that is integrated with the chair and assists in pulling the PV air flow towards the seated person. Not only is the inhaled air quality improved further but the exhaled contaminated air is extracted locally and its spread into the room air is minimized by adding the local exhaust working together with the PV system. Experimental study using two types of tracer gases have been conducted to evaluate the performance of this novel PV-PE system in conjunction with two different background ventilation systems. Two types of PE: top-PE and shoulder-PE are evaluated and four different arrangements between the Healthy Person and the Infected Person were studied. Three indices: Personalized Exposure Effectiveness; Intake Fraction; and Exposure Reduction were used to evaluate the system. The main hypothesis is that the Top-PE is better than Shoulder-PE and in the presence of PE for patient, Displacement Ventilation system leads to a better exposure reduction than Mixing Ventilation system. v The results indicate that there is a good potential for improving inhaled air quality by having the combined PV-PE system to pull the clean air towards the seated person, especially under displacement ventilation. When the PE is set at 10 l/s, the PEE of l/s PV and 10 l/s PV are 27% and 50% higher with DV than MV at the nearest position (0.2 m and degree) respectively. It is also seen that this kind of personalized exhaust can prevent the spread of contaminated air by exhausting the exhaled air directly before it mixes with the room air; especially the top-PE has a better performance than shoulder-PE. Furthermore, the use of PE is a more efficient way to protect the healthy person than using PV. After using the top-PE for infected manikin while switching off the PV for healthy manikin, a more than 70% reduction of exposure is found under MV and more than 75% for DV. However, the Healthy Manikin only enjoys about 25% reduction in exposure to the Infected manikin exhaled contaminated air when PV fresh air is at l/s, and 55% if the PV flow rate is increased to 10 l/s. This thesis contributes to the knowledge of ventilation systems by addressing a few limitations of PV systems as well as controlling the short range aerosol transmission between healthcare workers and patients in healthcare settings. vi List of Tables No table of figures entries found. 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Click one of vii the styles under Manual Table of Contents, and then type the entries manually. Nomenclature Abbreviations ACE Air Change Effectiveness ACH Air Change Rate AHU Air Handling Units ASHRAE American Society of Heating, Refrigerating and AirConditioning AQI Air-Quality Index ATD Air Terminal Device BTM Breathing Thermal Manikin CFD Computational Fluid Dynamic CMP Computer Monitor Panel CPP Circular Perforated Panel CSP Computer Simulated Person CTM Computational Thermal Manikin CV Central Ventilation DDV Desk Displacement Ventilation viii DPV Desktop Personalized Ventilation DR Draught Rating DV Displacement Ventilation FCU Fan Coil Unit HBIVCU Hospital Bed Integrated Ventilation and Cleaning Unit HDG Horizontal Desk Grill HEPA High-Efficiency Particulate Air HP Healthy Person HVAC Heating Ventilation and Air Conditioning IAQ Inhaled Air Quality ICAS Infection Control at Source iF Intake Fraction IP Infected Person ISO International Organization for Standardization LEV Local Exhaust Ventilation MV Mixing Ventilation PE Personalized Exhaust PEE Personal Exposure Effectiveness PEI Personal Exposure Index PER Pollutant Exposure Reduction Efficiency PEM Personal Environment Module PRE Pollutant Removal Efficiency PV Personalized Ventilation RH Relative Humidity RMP Round Movable Panel RNG Re-Normalisation Group SARS Severe Acute Respiratory Syndrome SBS Sick Building Syndrome SHPV Seat Headrest Personalized Ventilation SIMPLE Semi-Implicit Method for Pressure-Linked Equations TAC Task-Ambient Conditioning TAM Task Air Module ix TV Total Volume Ventilation UFAD Under Floor Air Distribution VDG Vertical desk grill Symbols Δt Temperature Difference C Constant dependent on clothing, body posture, chamber characteristicsand thermal resistance offset of the skin surface temperature control system (K.m2/W) C∞ Contaminant concentration in the outdoor supply air (ppm) CI Contaminant concentration in the inhaled air of a person (ppm) CPV Concentration of the tracer gas in personalized air (ppm) CR Contaminant concentration in the exhaust/return air (ppm) Ca Tracer gas concentration of ambient air Ch Inhaled tracer gas concentration for the Healthy Manikin Ci Exhaled tracer gas concentration from the Infected Manikin Cpvpe off Tracer gas (N2O) concentration in the inhaled air of the Healthy Person when both the PV and PE are turned off x Con Tracer gas (N2O) concentration with the particular PV or PE or both turned on D Hydraulic diameter (m) I Turbulence intensity (%) k Turbulent kinetic energy (m2/s2) L Flow rate(l/s) Mp Mass flow rates of inhalation for the healthy manikin (kg/s) MI Mass flow rate of exhalation for the infected manikin (kg/s) Qt T VF,L Dry heat loss Temperature (°C) Fresh air volume (l) VL Inhaled air volume (l) t*eq Manikin-based equivalent temperature in reference conditions (°C) t0 Supply air temperature (°C) teq Manikin-based equivalent temperature in an actual environment (°C) ɛ Turbulent kinetic energy dissipation rate (m2/s3) ɛp Personal exposure effectiveness (dimensionless) ɛe Personal exposure index (dimensionless) ηPER Pollutant exposure reduction efficiency (%) Φ Diameter τ Reynolds stress (kg/m/s2) τ Return age of the return/exhaust air(s) τbl Average age of air at the breathing level(s) y+ Near wall distance unit (dimensionless) xi xii Chapter 1: Introduction 1.1 Background and motivation With Several Severe Acute Respiratory Syndrome outbreaks, SARS in 2003, Pandemic Influenza A (H1N1/2009), and the more recent Influenza A (H5N1) in 2010, concerns about the airborne transmission of infection have become important. During the epidemics of Severe Acute Respiratory Syndrome (SARS) in China, 917 out of 4698 infected person were hospital/healthcare workers; this has highlighted the issue of short range aerosol transmission between healthcare workers and the patients. Li et al. (2007) reviewed the evidence for the effects of ventilation on the transmission of infectious diseases. They concluded that there was good evidence (as demonstrated by the contemporary technology available at the time of the studies) for aerosol transmission influenced by ventilation factors in outbreaks involving measles, chickenpox, the pneumococcus (Streptococcus pneumonia), SARS-CoV, tuberculosis, influenza and smallpox. Therefore, ventilation systems in healthcare environments should be carefully designed to reduce the risk of aerosol transmission, in particular those causing respiratory and gastrointestinal infection. Mixing ventilation, displacement ventilation and under-floor air distribution (UFAD) are at present the methods most applied in mechanically ventilated healthcare centers. Mixing ventilation involves mixing of the high momentum supply air with room air completely so that the temperature is uniform either in the entire space or in a specific zone of the space. It is able to provide uniform air quality in rooms and relatively great freedom in terms of interior decoration. However, the supply air at a low contaminant concentration is mixed with the contaminated room air by the time it reaches the inhalation zone of the healthy person. Displacement ventilation involves the supply of cool air at a low velocity through air inlets that are installed in the lower portion of the room, at the wall or floor. While it has been shown to provide occupants with better air quality and has good energy saving potential, the risk of drafts and contaminant issues have been raised. Another ventilation approach is the under-floor air distribution (UFAD) concept. The basic idea of the UFAD system is to supply air through a pressurized plenum to the occupants’ area. UFAD has the potential to increase the flexibility of space subdivision and reduce the zone sensible 13 load by not conditioning the upper part of the zone (Eng., 2009). However, despite all the advantages of UFAD, there are some disadvantages, such as cold feet and draft discomfort. Under UFAD, mixing ventilation and displacement ventilation systems, the fresh air cannot be delivered into the occupants’ breathing zone. Hence, the personalized ventilation concept was introduced in indoor air distribution more than a decade ago. It supplies clean, cool and dry outdoor air at low turbulence directly to the breathing zone of occupants. Different types of PV air terminal devices have been developed and their performance evaluated. The ability to provide local cooling and thereby enhance thermal comfort as well as improve inhaled air quality has been examined together with different types of background ventilation systems. It has been demonstrated that PV system is able to improve indoor air quality and potentially increase occupants’ satisfaction (Melikov et al, 2002; Kaczmarczyk et al., 2004; Sekhar et al, 2005; Gong et al, 2006; Yang et al, 2010a; Li et al, 2010). Despite all the advantages of PV, there are some disadvantages. The PV ATDs are typically either fixed in a place or have little flexibility to rotate and move. However, the inhaled air quality and thermal sensation depend on the distance between PV ATD and human being. Once the occupant starts moving around the desk, the distribution of personalized air cannot change accordingly. Although personal control was introduced to allow occupants to change the flow rate according to their preference, the angles and direction could not be manually adjusted easily, especially for some ATD such as vertical desk grille (VDG). In order to maximize the advantages of a PV system in delivering personalized air to the breathing zone at all times, it is interesting to explore the use of a localized exhaust device that is integrated with the chair and assists in pulling the PV air flow always towards the chair i.e. the seated person. Thus, in the case of a seated person moving within certain limits around the workstation, the chair integrated localized exhaust device will serve to provide directional control for the PV air plume. A certain minimum gauge pressure of the localized exhaust system is necessary to be able to divert the personalized air within the range of movement of the seated person. And most importantly, in the context of airborne infection control, it is critical that the ventilation system is able to extract the contaminated exhaled air immediately and 14 within the shortest possible time. This will minimize the spread of the contaminated air into the room air. Studies have found that normal breathing can produce respirable contaminated droplets (Edwards et al., 2004). Gao et al. (2008) found that PV has the possibility to increase the intake fraction of exhaled air and droplets from other occupants. In order to prevent or minimize the spread of contaminated air exhaled by occupants efficiently, the ideal strategy is to exhaust the exhaled air as much as possible right around the infected person. Local Exhaust Ventilation (LEV) is not a new concept, it is a system that uses extract ventilation to prevent or reduce the level of airborne hazardous substances from being breathed by people in the workplace, which has been used in industry for many years. The pollutants are drawn away from the source so that the hazardous substances are less likely to be inhaled by working people. The LEV has been reported with good performance of protecting workers in some industry by extracting air and discharging the air into the atmosphere, sometimes having it cleaned first to make it safe for release. However, limited studies have considered LEV as a ventilation type to reduce the transmission of infectious air in indoor rooms and spaces, such as wards in hospitals and air planes (Kwan et al. 2008; Melikov et al. 2010; Dygert & Dang, 2010, 2011; Zítek et al. 2010). So far no study has evaluated the combination of PV and LEV in healthcare settings. In the field of ventilation design in healthcare centers and hospitals, a lot of studies have been conducted to minimize both the short-range and long-range airborne infection routes (Cheong & Phua, 2006; Qian et al. 2008; Ho et al., 2009; Balocco & Lio, 2011; Nielsen et al., 2010;Villafruela et al., 2013). However, most healthcare ventilation system studies focus on specialized areas such as ward, operating rooms and isolation rooms. In real situations, a normal consultation room is the first place an infected person would stay before he/she will be diagnosed as infected and kept in an isolation room. Thus, the consultation procedure and simple check-up procedure in the consultation room may pose a risk of transmission of infectious diseases. The movement of the airborne particles and contaminated exhaled air around a person is partly governed by that person’s ‘microenvironment’ and partly by the airflow around the microenvironment. The idea of a novel PV-PE system aiming to create a microclimate helping to prevent the spread of exhaled contaminated air is supported by this observation. 15 1.2 Research Objectives This study aims at exploring the two types of newly-developed local exhaust devices, ― top-PE and shoulder-PE, which work together with PV to provide a Healthy Person with conditioned outdoor air for enhanced thermal comfort and inhaled air quality, and minimizing the contaminated exhaled air as well as small droplets from spreading into the room in healthcare settings. The objectives are stated as follows: Evaluate the potential of a PE device to enhance the performance of a PV device in terms of pulling the PV conditioned outdoor air towards a Healthy Person. Determine the effectiveness of airborne infection control of the combined PV-PE system in conjunction with background MV or DV systems in terms of the localized extraction of the contaminated exhaled air from an Infected Person in healthcare settings 2a Infected Person seated facing the seated Healthy Person 2b Infected Person seated under two different configurations by the side of the seated Healthy Person 2c Healthy Person standing by the side of the seated Infected Person Evaluate the potential for energy savings using the most optimal PV-PE configuration from objectives and 1.3 Structure of Thesis This study is in the field of ventilation but results from this study have application on control of airborne infection disease transmission in healthcare centres and hospitals. The structure of the thesis in each chapter is described briefly as follows: Chapter One introduces the background of the recent awareness of the effect of ventilation on airborne infection control and different types of conventional mechanical ventilation systems, and the motivation of the study. 16 Chapter Two is the literature review. This study is not independent of, but based on, previous research on PV system, local exhaust system in the field of reducing the transmission of infectious air in indoor environments, ventilation in healthcare centers and hospitals. After summarizing in detail the three topics, knowledge gap will be identified which give a general overview towards the motivation of this study. Chapter Three states the research methodology. It consists of three different sets of experiments and the details of how the experiments are designed, the types of instruments used, the experimental conditions and test procedures, data collection method. Chapter Four describes the preliminary study. The preliminary study comprised two pilot studies, which were conducted with a few parametric variations to find ways to make the experimental set-up more optimal. Chapter Five describes the influence of combined PV-PE for a Healthy Person on the ability to change the profile of PV conditioned outdoor air when the person is moving around his/her desk while remain seated. The influence of distance between PV ATD and seated person and the angle between the PV ATD centre line the breathing zone were studied. Chapter Six (and Appendix and 2) documents the potential protection of a Healthy Person (HP) from exhaled contaminated air from an Infected Manikin (Infected Person) by using a PE for Infected Person (IP) and PV-PE for the Healthy Person. A normal consultation procedure in healthcare settings with one IP sitting facing the HP was studied under Mixing Ventilation and Displacement Ventilation. The exposure of the Healthy Person was studied with two types of PE with two different flow rates. Chapter Seven documents the potential protection of a Healthy Person from exhaled contaminated air from an Infected Manikin (Infected Person) by only using a PE for Infected Person with either Mixing Ventilation or Displacement Ventilation system. Three different position arrangements with closer distance between the Healthy Person and the Infected Person were considered to simulate the simple sampling or medical check-up procedure. The exposure of the Healthy Person was compared 17 between the three arrangements with and without PE. The exposure was also recorded with two types of PE with two different flow rates. Chapter Eight describes simulations of the Indoor Environmental Chamber using CFD. Model was first validated by comparing the results from CFD and the experiments. More flow rates are investigated using CFD simulation to evaluate the potential for energy savings using the most optimal PV-PE configuration from experiments. Chapter Nine contains the conclusions and recommendations. The objectives are reviewed and the hypotheses are verified. Limitations of this study are stated and practical implementation of the novel PV-PE system is discussed. In particular, the contributions of this research are briefly discussed. Lastly, some suggestions for further research and the development of ventilation system for PV-PE system and airborne infection transmission control are given.   18 [...]... Chapter 1: Introduction 1. 1 Background and motivation With Several Severe Acute Respiratory Syndrome outbreaks, SARS in 2003, Pandemic Influenza A (H1N1/2009), and the more recent Influenza A (H5N1) in 2 010 , concerns about the airborne transmission of infection have become important During the epidemics of Severe Acute Respiratory Syndrome (SARS) in China, 917 out of 4698 infected person were hospital /healthcare. .. Healthy Person with conditioned outdoor air for enhanced thermal comfort and inhaled air quality, and minimizing the contaminated exhaled air as well as small droplets from spreading into the room in healthcare settings The objectives are stated as follows: 1 Evaluate the potential of a PE device to enhance the performance of a PV device in terms of pulling the PV conditioned outdoor air towards a Healthy... Person 2 Determine the effectiveness of airborne infection control of the combined PV-PE system in conjunction with background MV or DV systems in terms of the localized extraction of the contaminated exhaled air from an Infected Person in healthcare settings 2a Infected Person seated facing the seated Healthy Person 2b Infected Person seated under two different configurations by the side of the seated... divert the personalized air within the range of movement of the seated person And most importantly, in the context of airborne infection control, it is critical that the ventilation system is able to extract the contaminated exhaled air immediately and 14 within the shortest possible time This will minimize the spread of the contaminated air into the room air Studies have found that normal breathing can... the combination of PV and LEV in healthcare settings In the field of ventilation design in healthcare centers and hospitals, a lot of studies have been conducted to minimize both the short-range and long-range airborne infection routes (Cheong & Phua, 2006; Qian et al 2008; Ho et al., 2009; Balocco & Lio, 2 011 ; Nielsen et al., 2 010 ;Villafruela et al., 2 013 ) However, most healthcare ventilation system. .. One introduces the background of the recent awareness of the effect of ventilation on airborne infection control and different types of conventional mechanical ventilation systems, and the motivation of the study 16 Chapter Two is the literature review This study is not independent of, but based on, previous research on PV system, local exhaust system in the field of reducing the transmission of infectious... Concentration of the tracer gas in personalized air (ppm) CR Contaminant concentration in the exhaust/ return air (ppm) Ca Tracer gas concentration of ambient air Ch Inhaled tracer gas concentration for the Healthy Manikin Ci Exhaled tracer gas concentration from the Infected Manikin Cpvpe off Tracer gas (N2O) concentration in the inhaled air of the Healthy Person when both the PV and PE are turned off x Con... some industry by extracting air and discharging the air into the atmosphere, sometimes having it cleaned first to make it safe for release However, limited studies have considered LEV as a ventilation type to reduce the transmission of infectious air in indoor rooms and spaces, such as wards in hospitals and air planes (Kwan et al 2008; Melikov et al 2 010 ; Dygert & Dang, 2 010 , 2 011 ; Zítek et al 2 010 )... exhaust device that is integrated with the chair and assists in pulling the PV air flow always towards the chair i.e the seated person Thus, in the case of a seated person moving within certain limits around the workstation, the chair integrated localized exhaust device will serve to provide directional control for the PV air plume A certain minimum gauge pressure of the localized exhaust system is necessary... discomfort Under UFAD, mixing ventilation and displacement ventilation systems, the fresh air cannot be delivered into the occupants’ breathing zone Hence, the personalized ventilation concept was introduced in indoor air distribution more than a decade ago It supplies clean, cool and dry outdoor air at low turbulence directly to the breathing zone of occupants Different types of PV air terminal devices have . PERFORMANCE EVALUATION OF PERSONALIZED VENTILATION - PERSONALIZED EXHAUST (PV- PE) SYSTEM IN AIR- CONDITIONED HEALTHCARE SETTINGS YANG JUNJING (Bachelor of. on PV system, local exhaust system in the field of reducing the transmission of infectious air in indoor environments, ventilation in healthcare centers and hospitals. After summarizing in detail. advantages of a PV system in delivering personalized air to the breathing zone, it is interesting to explore the use of a personalized exhaust (PE) device that is integrated with the chair and