Performance evaluation of personalized ventilation personalized exhaust (PV PE) system in air conditioned healthcare settings 2

Chapter2: Literature Review This chapter consists of three parts, a holistic and critical review of PV, a review of local exhaust ventilation in the field of a ventilation type to reduce the transmission of infected air in indoor environments, the review of studies of ventilation in healthcare centers and hospitals. After summarizing in detail the three topics, knowledge gap is identified and the research motivation is discussed. 2.1 Personalized ventilation Personalized Ventilation (PV) concept, introduced by Fanger (2000), aims to supply conditioned outdoor air to the breathing zone of occupants. A lot of studies have been done to investigate how to supply as much as possible PV air to the people. 2.1.1 Air Terminal Device Melikov et al (2002) developed five different kinds of Air Terminal Device (ATD) to evaluate their performance: Movable Panel (MP), Computer Monitor Panel (CMP), Vertical Desk Grill (VDG), Horizontal Desk Grill (HDG), and Personal Environments Module (PEM) (Figure 2.1). The movable panel (MP) was positioned 0.2 m front of the manikin’s face and 0.3 m above the nose. It was adjustable in a wide range to supply personalized air. The computer monitor panel (CMP) was mounted on the monitor at a distance of 0.4 m from the edge of the desk. It was able to supply air in a changeable direction on a vertical plane. The vertical desk grill (VDG) and the horizontal desk grill (HDG) were mounted at the edge of the desk, supplying a vertical and a horizontal flow of personalized air direct to the breathing zone of the occupant. The personal environments module (PEM) consists of two nozzles mounted at the two edges of the desk and allow for changes of the direction of the personalized air in both horizontal and vertical planes. A typical office workplace, with a dimension of m X m X 2.5 m was simulated. A breathing thermal manikin was used to simulate an occupant, sitting in front of a computer at a distance of 0.15 m from the desk. Both the upright position and leaning forward position of the manikin were performed. The results showed the lowest temperature of the inhaled air was achieved by VDG. Movable panel (MP) performed well as well as it allowed for a change of airflow direction in relation to the occupant. All the ATDs were able to reduce the amount of exhaled air re-inhaled by the manikin. Figure 2.1: CMP, MP, VDG, HDG, and PEM [Melikov et al. (2002)] Different from the movable panel, a triangular plenum box (390 mm×240 mm×150 mm) with a rectangular grille opening, the round movable panel (RMP) is developed by Bolashikov et al. in 2003. It is a round front panel with an opening of Ø185 mm and a honeycomb plate attached. Bolashikov (2003) also developed a new ATD named headset. It is a rectangular supply nozzle (35 mm×8 mm) shown in Figure 2.2. The performance of both the ATDs was tested at three combinations of room air temperature and personalized air temperature: 23/23 oC, 23/20 oC and 26/20 oC respectively, and at different flow rates of personalized air, ranging from to 15 l/s for RMP and 0.18 to 0.5 l/s for Headset. Both the inhaled air quality and thermal comfort were evaluated. The results showed that inhaled air consisting of 100% personalized air could be achieved with the RMP and up to 80% with the Headset. Figure 2.2 Round movable panel [Bolashikov et al. (2003)] Figure 2.3: Headset [Bolashikov (2003)] Gao (2004) used a microphone circular outlet nozzles as the PV ATD to the experiment and simulation.The ATD is located at the microphone position beneath the chin (Figure 2.4). They conducted both experimental research and CFD modelling study of this PV ATD. Desk-edge nozzle is another type of PV ATDs, which is installed beneath the front edge of a workstation, supplying air at a proper angle (Faulkner et al, 2004). Muhic and Butala (2006) developed a personal microclimate system (PERMICS) (Figure 2.5) and demonstrated its effectiveness.Circular Perforated Panel (CPP), mounted above the computer monitor with uniformly distributed Ø5 mm holes, was used by Zhou (2005a,b), Gong (2005) and Sun (2006). Sun et al. (2006) studied High Turbulence Circular Perforated Panel (High-Tu CPP) and Low Turbulence Circular Perforated Panel (Low-Tu CPP) (Figure 2.6). The impact of turbulence on spatial distribution of the cooling effect on the facial region and whole body were investigatedthrough both experimental and subjective studies. They concluded low turbulence intensity is preferred in order to achieve greater facial cooling effect,larger range of velocities at the face area andcooler facial thermal sensation. Arm attached ATD (Figure 2.7) is another type of air terminal devices developed by Melikovet al. (2007). The ATD was attached to an arm that could be rotated around its vertical axis. Thus, the ATD itself was movable in vertical plan and the direction of the personalized flow was allowed for changing in horizontal plan. This design allowed the occupant direct the personalized flow at a preferred angle as well as the target velocity at his/her face or body. Figure 2.4:Microphone circular outlet nozzles [Gao (2004)] Figure 2.5 Personal microclimate system (PERMICS) [Muhic and Butala (2006)] Figure 2.6 Low-Tu and high-Tu Circular Perforated Panel (CPP) [Sun et al. (2006)] Figure 2.7 Arm attached ATD [Melikov et al. (2007)] Amei et al. (2007) utilized four different types of Task Ambient ATDs: 3DU+, PEM, TU, and RCU to investigate the effect of Task Airconditioning systems on thermal comfort in a climate chamber. The Task Air conditioning system ATDs used in the experiments are shown in Figure 2.8. TU was installed to the back surface of a desk. Isothermal airflow was supplied from the front edge of the desk. The direction of the air could be adjusted from horizontal (0–90 degree). PEM had a desktop diffuser with a mixing box under the desk and a radiant heat panel. It allowed occupants to control the temperature of supplied air by mixing primary air and ambient air in a mixing box. 3DU+ is non-isothermal Task Air-conditioning ATD. It has a flexible duct which allows user to adjust its position and angle freely. It is arranged along the partitions and blows out air mainly from behind a user. RCU is developed on the basis of 3DU+, which supplies air to the user’s backwith tripod stand located behind user. The ATD position can be automatically adjusted by using remote control of surveillance camera platform. The ATD is able to move in a range of 17o upward, 27o downward and 310o in horizontal range. Figure 2.8 TAC systems: (a) 3DU+, (b) PEM (non-isothermal airflow desktop-based Personal Environmental Module), (c) TU (isothermal airflow under-desk task unit), (d) RCU (remote control unit). [Amei et al. (2007)] Niu et al. (2007) developed a chair-based personalized ventilation system as shown in Figure 2.9. It is proposed that it can potentially be applied in theatres, cinemas, lecture halls, aircrafts, and even offices. Experiments were conducted to compare eight different ATDs and it was found that up to 80% of the inhaled air could be composed of conditioned PV air with a supply flow rate of less than 3.0 l/s. Perceived air quality improved greatly by serving cool air directly to the breathing zone. Feelings of irritation and local drafts could be eliminated by proper designs. PV air with a temperature below that of room air was able to bring “a cool head” and increased thermal comfort in comparison with mixing ventilation. Figure 2.9 A ventilation seat with an adjustable personalized air supply nozzle. [Niu et al. (2007)] Conceiçao et al. (2010) equipped the classroom desks with PV ATDs. As shown in Figure 2.10, each PV system is equipped with one air terminal device located above the desk writing area, in front to the trunk area (incident in the trunk area), and other located below the desk writing area, in front to the legs area (incident in the knees area). Each air terminal device, made in plastic material, had a circular exit area around of 48 cm2. Figure. 2.10 Classroom desks with PV ATDs [Conceiçao et al. (2010)] Russo and Khalifa (2010) developed a novel co-flow PV nozzle (Figure 2.11) that extends the clean air “potential” core of the PV jet farther into the breathing zone. The CFD simulation results showed that this kind of Co-flow PV nozzle is far superior to a single round PV nozzle. Yang et al (2010a) developed ceiling mounted personalized ventilation ATDs (Figures 2.12& 2.13), which could avoid ducting for supply of fresh air to each workplace and thus improves indoor aesthetics and have a better room layout.The ATD, made of aluminium with a round outlet of a diameter of 95 mm, was mounted on the ceiling above the occupant. The nozzle was connected to the ductwork with a diameter of 160 mm on the other side. The total length of the nozzle was 140 mm. High momentum of the PV air was used for this type of ATD so as to keep the core region of personalized airflow as long as possible.The ATD was able to supply air at low turbulence intensity, which helps reduce heat transfer and mass mixing between personalized air and room air so as to supply maximum cool and fresh air to the breathing zone. The ATDs installed on the ceiling are well above each workplace/occupantin conjunction with mixing ventilation. They conducted both subjective and objective studies of this newly developed PV ATD and found that ceiling mounted PV system can improve thermal sensation, perceived air quality, and inhaled air temperature. Moreover, they analysed the energy saving potential of ceiling mounted PV system in conjunction with mixing ventilation in hot and humid climate and concluded that ceiling mounted PV system could decrease the total energy consumption comparing with mixing ventilation plus desk fans. Pantelic & Tham (2010) designed a desktop PV (DPV) air terminal device (Figure 2.14), the openings of which covered only the top half of the DPV ATD front surface. There were 30 supply openings (5 vertical x horizontal) and each opening on the front surface is circular with a diameter of mm. Lower half of the DTV ATD (80 mm from the table surface) was designed without any openings to avoid interaction of PV air flow and obstacles on the surface of the table. Figure 2.11 Novel Co-flow PV nozzle and its entrainment process. [Russo &Khalifa (2010)] 10 higher location of exhaust outlets in a room seems to more efficiently remove fine particles and gaseous pollutants from human exhalation with a higher temperature than the ambient air. An exhaust at the bottom of a room seems more efficient in removing large particles. Figure2.27 Four different arrangements of supply diffusers and exhausts in the tested downward ventilation system [Qian et al. (2008)] In 2006, Cheong and Phua conducted a research on the ventilation design strategy for effective removal of pollutant in the isolation room of a hospital. In Strategy 1, the isolation room has two air supply diffusers and two extract grilles mounted on the ceiling. Strategy retains the air supply diffusers in Strategy but relocates the two extract grilles to the wall behind the bed at 0.3 m above the floor level. Strategy has the same layout as Strategy except the ceiling diffusers are replaced by supply grilles and relocated closer to the wall behind the bed. The results of Strategy show the best pollutant removal 49 efficiency with the supply air grilles delivering a laminar flow of outside air to the occupant with minimal entrainment of the air in the room. Ho et al. (2009) investigated the air velocity, temperature, and contaminant transport in an air-conditioned operating room. It is found that airflow pattern significantly affects the performance of both contaminant removal and thermal comfort. They concluded that the horizontal location of the supply grilles has significant effects on thermal comfort while that ofthe exhaust grilles does not. For an overall design, considering the performance of the room on both contaminant removal and thermal comfort, it can be concluded that the closer the supply grilles to the centre of the room, the better the performance is. Figure 2.28 Model of an operating room [Ho et al. (2009)] 50 Neilsen et al. (2010) studied the risk of cross-infection in a hospital ward with downward ventilation system. The research found that the location of the return openings plays an important role for the distribution of the exhaled contaminant (tracer gas) in the room. Textile partitions, which are often used in hospital wards, not decrease the risk of cross-infection in this special air distribution case. They could even increase the risk to the healthcare personnel. Figure 2.29 The full-scale room simulating a hospital ward. A: room with one exhaust opening. B: room with four exhaust openings. C: room with movable textile partition [Nielsen et al. (2010)] Villafruela et al. (2013) used computational fluid dynamics (CFD) to evaluate the ability of the ventilation system to minimize the risk of infection in the rooms of isolated infectious patients. They analyzed the influence of the position of the air inlets and outlets and concluded that the position of the air inlets and outlets has a great influence on the quality of the ventilation. And for a grille air diffuser, a ventilation strategy in which the air exhaust is performed through the ceiling just above the patient and the air supply is introduced in the ceiling in front of the bed provides good contaminant change efficiency and a low risk of infection. However, if the contaminant is emitted in a recirculation zone its removal is less effective. 51 Figure 2.30 Isometric view of the room with the position of the air inlets and outlets [Villafruela et al. (2013)] Balocco and Lio (2011) used numerical transient simulations to investigate the air flow patterns, distribution and velocity, and the particulate dispersion inside an existing typical hospitalization room. The results highlight that the positioning of the air-supply inlets in the ceiling and the exhaust vents at opposite side of the room and in the ceiling, provides an up-draft effect and efficient infection control. 52 Figure 2.31. Isolation room – the 3D model with air diffusers location (high air inlet diffuser A, return air diffusers B, C and D), beds with the head of the two patients [Balocco and Lio (2011)] 2.4 Knowledge Gap Studies related to PV and Local Exhaust Ventilation are summarized. 2.4.1 Personalized Ventilation Performance From the literature review, the personalized ventilation system has been found to provide more conditioned outdoor air in the breathing zone to improve inhaled air quality, and also to provide cooling effect especially in the facial area. Energy efficiency of PV system has been reported compared to conventional ceiling supply system. Skwarczynski et al. (2010) suggested that PV with increased facially applied air movement at high relative humidity can be considered for energy savings strategy. Yang et al. (2010) concluded that the use of PV with ceiling mounted ATD in conjunction with mixing ventilation at room air temperature of 26° C will lead to useof substantially less energy in comparison with energy used withmixing ventilation at 26° C and 28°C and desk fans. However, two major draw backs were identified from studies of PV system. They are: 1) Inability to prevent the spread of contaminated air; and 53 2) Most of the PV ATDs are always fixed or have little flexibility to rotate/move. Inability to prevent the spread of contaminated air The primary aim of a PV system is to supply conditioned outdoor air to the breathing zone to enhance thermal comfort and inhaled air quality. 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. Especially in UFAD and DV ventilation, the exhaled air of the infected manikin was reported to be able to penetrate a longer distance, which may lead to a higher infection risk. (Qian et al. 2006; Gao et al., 2008; Shen et al. 2013). Cermak and Melikov (2007) concluded that the use of PV may cause mixing of contaminants generated in its vicinity, such as exhaled air. He et al. (2010) also demonstrated that PV would enhance the level of exhaled particles mixingunder DV and UFAD much stronger than under MV. For the studies on simulation of particles in exhaled air, the concentration profile of particles with diameter smaller than 0.8 µm is similar with the profile of gas (Gao et al., 2008; He et al., 2010). Meanwhile, the peak of aerosol size distribution in exhaled breath was between 0.8 and 0.9 µm when the diameter range 0.5-20 µm was measured (Johnson and Morawska, 2009). With a wider size range to be examined, the peak size distribution was found at around 0.07 µm, and an additional broad and strong peak was found between 0.2 and 0.5 µm (Holmgren et al., 2010). Thus, the study of exhaled droplets can be simplified as gas when doing simulation in the research. Most of the PV ATDs are always fixed or have little flexibility to rotate/move According to literature review on different types of PV ATD prototypes, it is found that current researches on PV and PV ATD prototypes never consider the occupants’ moving around the desk while they still remain seated. However, the ATDs are always fixed or have little flexibility to rotate/move. The PV performance and inhaled air quality depend largely on the distance 54 between PV ATD and occupants and the fresh air core region relative to the occupants. During working hours, occupants will move around the desk while still sitting in chair from time to time instead of sitting still in front of the PV ATD as simulated in previously conducted experiments. This leads to a requirement for a more flexible strategy for the fixed PV ATDs. 2.4.2 Local Exhaust Ventilation System Local Exhaust Ventilation (LEV) is a system that uses extract ventilation to prevent or reduce the level of airborne hazardous substances from being inhaledby people in the workplace, which has been used in industry for many years. The pollutants are drawn away from a process 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 or having first been cleaned 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. The literature review in the utilization of LEV in indoor environment only found studies that focus on 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 considered the combination of PV and LEV in healthcare settings. 2.4.3 Personalized Ventilation (PV) – Personalized Exhaust (PE) system in healthcare settings The above two limitations of PV systems lead to the introduction of combining PV and the local exhaust, which is named PV-PE system in this study. As a newly developed ventilation system, the performance of PV-PE system has not yet been evaluated. In the PV-PE system, while the seated Healthy Person is moving around within the confines of his/her consultation desk, the supply direction of the PV air is supposed to change according to the position of the chair influenced by its integral PE devices. Melikov et al. (2007) demonstrated that the inhaled air quality measured by thermal manikin does not change when the personalized flow from a circular air terminal device 55 (RMP) was supplied from front, left, right and above. This conclusion further supports the idea of a PV-PE system to pull the PV air always towards the breathing zone from different relative position. In terms of the airborne contamination control strategy, there are two main methods of ventilation: dilution ventilation which provides a flow of air into and out of the working area and does not give any control at the source of the contamination, and LEV which intercepts the contamination as soon as it is generated and removes it from the working area before it can be inhaled. By combining the Personalized Ventilation and Local Exhaust Ventilation, the two strategies are taken into consideration at the same time so that the exhaled air from the person can be exhausted via the local exhaust before mixing with the room air, as shown in Figure2.32. Figure 2.32 Advantage of adding PE to a PV system The experience in 2003 with Severe Acute Respiratory Syndrome (SARS) and the H1N1 in 2009 highlighted the issue of aerosol transmission, especially the short range between healthcare workers and their patients. A lot of studies have been conducted regarding the effects of ventilation system on the infection risk in a healthcare facility. However, the literature regarding the effects of ventilation system on the infection risk studies in a healthcare facility mainly focus on the design of different locations of background supply 56 and exhaust in multiple-bed hospital wards, isolation wards, operating theatres. Two aspects are identified from studies of infectious control in healthcare settings which are worth further research. They are: a. The study of aerosol transmission between Healthy Person (doctors, nurses, etc.) and people with undiagnosed infectious diseases during normal consultation and simple medical check-up process before the Infected Personare diagnosed and are warded in a hospital; and b. The utilization of PV and PE in healthcare settings. 2.5 Motivation Hospital and healthcare facilities have different indoor environment due to the function and health needs of its occupants. Currently, most ventilation studies revolve around specialized areas such as operating rooms and isolation rooms. However, the normal consultation procedure and simple check-up procedure between a Healthy Person and an Infected Person may pose a risk of the transmission of infectious diseases. Since 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, an integrated ventilation system aiming to create a microclimate helping to prevent the spread of exhaled contaminated air is proposed. The main sources of air supply for consultation rooms in most hospitals are mechanical ventilation. Mixing ventilation, displacement ventilation, underfloor air distribution system as well as downward ventilation systems were studied by researchers. However, none of them is very efficient in terms of protecting healthy persons while removing the contaminant air. Personalized ventilation has been introduced in indoor environment for more than a decade. The main purpose of using a PV system is to supply fresh air to an occupant. Thus, the idea of incorporating the PV system into the ventilation system inside the consultation rooms in hospital would be helpful for protecting a healthy person. In addition, the infected person keeps exhaling 57 contaminated air into the surroundings. It would be a good source control strategy if a ventilation system could exhaust the contaminated air before it mixes with the room air. Hence, the personalized exhaust system is introduced. The design of this ventilation system proposed in this study will create a complex air flow around a human being -the thermal plume, a thin layer of air or ‘boundary layer’ that adheres closely to the body surface, the personalized air, the respiratory air, the air created by the suction of personalized exhaust and the background ventilation air. Experiments are designed to test and evaluate the performance of the novel Personalized Ventilation-Personalized Exhaust system. 2.6 Objectives In order to realize the advantages of PV system and have a more flexible system to increase the inhaled air quality and prevent the transmission of exhaled pollutant air, the Personalized Ventilation (PV) – Personalized Exhaust (PE) system is explored. The scope of this study is to explore a newly-developed PE device, working together with a PV device and to evaluate the feasibility of this novel system in healthcare settings and its performance with two different kinds of ambient ventilation type: Mixing Ventilation (MV) and Displacement Ventilation (DV). The objectives of this study are described 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 58 2b Infected Person seated under two different configurations by the side of the seated Healthy Person 2c Healthy Person standing facing the seated Infected Person Evaluate the potential for energy savings using the most optimal PV- PE configuration from objectives1 and 2. 2.7 Hypothesis Based on the literature review, the following hypotheses are developed to meet the above research objectives: Hypothesis 1: Combined PV and PE system can enhance the inhaled air quality by pulling the PV conditioned outdoor air towards the HP when the HP is moving around his/her desk. Hypothesis 2: Combined PV and PE system for HP can achieve the highest Personalized Exposure Effectiveness (PEE). Hypothesis 3: PV for HP helps to reduce the exposure from IP Hypothesis 4: PE for IP helps reduce the exposure for HP • 4a: Top-PE is better than shoulder-PE • 4b: In the presence of PE for IP, DV system leads to a better exposure reduction than MV system Hypothesis 5: PE for IP with PV for HP provides the best exposure reduction; PE for IP is more effective than PV for HP. Hypothesis 6: With MV, the highest exposure case among the cases studied is when HP and IP are at 45 degrees to each other, while with DV, the highest exposure is when HP is standing, facing the seated IP. 59 60 Instit ute   Aut hor       Tongj i,   Slove China   nia   Portu   gal   Berk  eley   Japa   n   Polan   d,De Polan nmar d,De k   Japa nmar   n   k   Den     mark   Den   mark   Singa   pore   Leba non      Sing apor Singa e   pore   Singa pore   Hong   Kong   Hong   Kong   Tongj i,   Singa China   pore   Syrac use   Syrac   use   City     Univ Tsing ersity   hua   of  NY   Hong       Kong     Hong   Kong   Hong   Kong   Syrac use   Syrac   use   Den   mark   Slova   Den   mark   Slova   Den  mark   Den mark   Den mark   Czec h     P P Backgroun V   E   d   Ventilatio     M D U D n   V   V   F o   A w v     v   T r P T E o   o h n p l e e i l r r c u m g s   v   t  a  y   a   l         n   a  t v   c  n       o   a     t m l  r v   f  y   o  s    a v   n r i  s  t    s     m         i  s v       s v   i v       o  n   v     v   v             v   v     v     v                 v   v                     v           v   v     v     v               v   v   v                                   v     v         v     v   v                                 v     v     v   v   v           v         v                           V   Niu   v       v                                     v         v   Ga o   Pan teli Kha c   lifa   Kha lifa   Ric hm Zha ond   o   Li   v     v   v   v       v         v         v       v                     v   v       v     D   n w v   v   v    a       r   d         v       V   e v        n        t i        l a v         t   v      i o     v    n   v       Ma kho Tha ul   m   Yan g   Yan g   Niu   v     Ga o   But ala   Con ceiç Fau ao   lkn Tan er   abe   Kac zm Kac arc zm zyk   Kat arc o   zyk   Mel iko Mel v   iko Li   v   v     V     V     V     v     v     v     v     v       v     Applicatio n   A i r   q  u a   l  i tv   y   v   O f f i c v   e s   v   v   v   v   v   v   v     v     A i r c r  a f   t     C l a s s  r o   o v   m   I A P F   Q C I   L , P      C     T           v               v                             v               v               v               v             v           v           H o s p i  t a   l  s   Evaluation  index     Metho dology   P No E rm E   ali ze d      co   nc   en    tra   tio   n         C o n ce nt  ra ti   o  n   u   ni  fo  r m  it y     in  d ex                           V e n til at v   io n     ef  fe ct   iv  e  n e  ss   P Po E llu I   ta nt   ex    p   os   ur    e     re   d    uc    ti o    n   v                     M a ni ki n-­‐  b as   e  d   e   q  ui  va le  nt   te   m  p er  at ur  e                     A i r   c h  a n   g  e  v   e  f  f e  c t   i  v e  n e  s s                 v     E x p o s  u r e   r e d u c t i o n   P oll ut a nt    re m ov al   ef v fic ie nc y   T r a c e  r  v   g  a s   v   S u b j e  c t   i  v e     C F D     v       v       v         v   v   v     v   v       v         v       v   v                 v   v               v     v           v     v   v   v     v                 v         v   v                     v     v   v   v     v       v                     v                     v     v         Objective       v           v           v                                 v   v     v           v                                           v           V               v                       v       v     v   Li       v   v     v     v           v                     v   v       v       Li                           v       v     v   Da ng   Da ng   Mel iko Hal v   von Bol ˇov ash a´   Hal iko von v   Sch ˇov iav a´   Sch on   iav Mel on   iko Zíte v   k   v       v         v     v           v     v     v           v             v       v                     v     v           v             v     v   v                       v     v         v     v                       v               v   v     v       v       v   v   v       v                   v             v       v     v   v   v                                               v         v   v   v       v                   v             v       v     v               v   v   v                                     v     v               v     v                       v               v   v           v           v           v   v                 v       v   v   v           v   v           v                           v     v         61   v     62       63                     64 [...]... is uniformly maintained at 23 .5 °C Yang et (20 10) al 21 °C; 23 .5°C; 26 °C 26 °C ; 23 .5°C The use of PV with ceiling mounted ATD in conjunction with mixing ventilation at room air temperature of 26 °C will lead to substantial energy saving compared with energy used with mixing ventilation at 26 °C and 28 °C and desk fans for providing thermal comfort at each workplace Li et (20 10) al 22 °C 26 °C and UFAD... 20 05) 26 °C 23 °C; 26 °C A warmer room temperature at 26 °C with a PV air at 23 °C could: 1) Lower breathing temperature than a room air temperature 26 at 23 °C without PV 2) Reduce space cooling load compared with a conventional system in which the space is typically maintained at 23 °C Gong et al 21 °C; (20 05, 20 06) 23 .5 °C; 26 °C 23 .5 °C; 26 °C Air movement is preferred even when the room air temperature... below 26 °C Local air velocities ranging from 0.3 to 0.45 m/s is preferred with an ambient temperature of 23 °C, 0.3 to 0.9 m/s are preferred with an ambient temperature of 26 °C Yang et (20 10) al 21 °C; 23 .5 °C; 26 °C 26 °C ; 23 .5 °C A warmer space temperature, such as 26 °C, with PV air of 23 .5 °C, can reduce space cooling load by spot cooling in comparison with total mixing airconditioning system in. .. rejecting exhaled air from the flow or air that may subsequently be inhaled (Melikov, 20 04) The design of personalized air should avoid mixing with exhalation, and also avoid the exhalation which will be inhaled again 2. 1.4 Study of temperature combination of PV supply air and background air According to American Society of Heating, Refrigerating, and Airconditioning Engineers (ASHRAE Standard 55 -20 10)... Equation 2. 1, which is expressed as the percentage of PVair in the inhaled air εp = C I ,O − C I C I ,O − C PV (Eq 2. 1) Where CI,0 is the concentration of tracer gas in the room air, CI is the concentration of tracer gas in the inhaled air, CPV is concentration of tracer gas in the PV air This index is equal to one when 100% PV air is inhaled and it is equal to zero if no PV air is inhaled Since the... energy saving consideration A summary of temperature combination studies of PV and background ventilation is listed in Table 2. 1 25 Table 2. 1: Temperature combination studies of PV and background ventilation Researchers PV air supply Background temperature air temperature Main results Kaczmarczyk 20 °C et al (20 02a, 23 °C b) 23 °C Best condition in regard to perceived air quality, perception of freshness... and intensity of SBS symptoms was when PV air was at 20 °C Zeng et (20 03) al 20 °C; 23 °C; 26 °C 23 °C; 26 °C; 28 °C; The personalized air temperature only affected the perceived air quality at the first 30 minutes of the experiments Zeng et (20 05) al 23 °C; 23 °C 26 °C PEE (εp) depends more onthe distance between PV ATD outlet and the occupant’s breathing zone than onthe PV air flow rate Melikov (20 04)... and Melikov (20 10b) to investigate the impact of disturbances due to walking person on the performance of ‘‘ductless’’ personalized ventilation in conjunction with displacement ventilation They found that the walking person introduced mixing in the room and therefore the concentration of the exhaled air inhaled by the polluting manikin increased He et al (20 11) investigated the transmission of respiratory... the air was perfectly mixed, divided by the average age of air where occupants breathe Sincethe average age of air exiting the room is the same as the age of air that 15 would occur throughout the room if the indoor air were perfectly mixed, the ACE can be also defined as the exhaust- air age divided by the average age of air in breathing zone of heated manikins The value indicates the improvement of. .. heated) placed on the table in front of the polluting manikin The results show that the use of personalized ventilation causes mixing and increases the concentration of tracer gas at a lower level However, the personalized ventilation may increase mixing and transportation of pollution generated in the vicinity of its supply ATD and in general will decrease the quality of the inhaled air More research was . mm) shown in Figure 2. 2. The performance of both the ATDs was tested at three combinations of room air temperature and personalized air temperature: 23 /23 o C, 23 /20 o C and 26 /20 o C respectively,. air is conditioned 100% outdoor air which is free of tracer gas. The concentration of tracer gas in inhaled air, the air exhaust from the room, at several sampling points in the room and in. of air in breathing zone of heated manikins. The value indicates the improvement of fresh air that is delivered to the inhalation zone in comparisonto well-mixed ventilation. The exhaust- air