Performance evaluation of personalized ventilation personalized exhaust (PV PE) system in air conditioned healthcare settings 3

Chapter 3 Research Methodology
3.1 Overview of Research Methodology
The research methodology involves a combination of experiments and CFD
simulations in order to achieve the objectives stated in Section 3.1. This is
summarized in Figure 3.21. Tracer gas measurements are taken to evaluate the
effectiveness of the novel PV-PE system in enhancing the inhaled air quality
and in reducing the transmission of infections. Potential for energy savings is
evaluated using CFD simulations to perform a few lower flow rates from 4 l/s
to 9 l/s of PE.

The experimental facilities are described in Section 3.4. The design of
experiments and the indices used to evaluate the effectiveness of the PV-PE
system are discussed in Section 3.5.

3.2 Experimental Facilities
3.2.1 Experimental Chamber
3.2.1.1 Indoor Environmental Chamber
The closed space is to simulate a typical health-care consultation room with
one Healthy Person (HP) and one Infected Person (IP). The experiments are
conducted in an Indoor Environmental Chamber, 6.6 m (L) × 3.7 m (W) × 2.7
m (H), in the School of Design and Environment, NUS, as shown in Figure 3.1.


Figure 3.1: Schematic layout of the Indoor Environmental Chamber
The Indoor Environmental Chamber is situated in a laboratory, measuring 9.6
m (L) × 7 m (W) × 2.7 m (H) in size and is fitted with two large fixed glass
windows, 1.5 m (W) × 1.2 m (H), along one of the larger walls. Three sides of
the chamber were enclosed by an annular space, which minimized external
environmental interferences. The fourth side of the chamber adjoined a control
room, which was controlled at the same temperature as the chamber.
There are two air conditioning systems that serve the Indoor Environmental

Chamber. The primary system serving the chamber comprises a Fan Coil Unit
(FCU) that supplies conditioned outdoor air (Fresh Air) through the PV air
terminal device. The secondary system consists of an Air Handling Unit
(AHU), which delivers conditioned recirculated air as the ambient or
background MV/DV system. The primary system contains a main duct that
terminates into a plenum box, from which six branch ducts originate and enter
the chamber through openings in the wall. The conditioned outdoor air is then
delivered to the occupant through PV air terminal devices. The ambient
cooling to the chamber is served by re-circulated air stream, which is
conditioned in the AHU and distributed by ceiling-based re-circulated air duct.
Two main ceiling supply diffusers controlled by a Variable Air Volume
System (VAV) box controller are centrally and symmetrically located at the
suspended ceiling of the chamber. Another two floor-standing semi-circular
displacement ventilation supply diffusers are also centrally and symmetrically
located at the two ends of the chamber. Two diagonally located ducted return
grilles extract the return air from the chamber. The background supply air
diffusers and the return grilles are shown in Figure 3.2.

Figure 3.2: Four-way supply diffuser (left), Floor-standing, low-velocity,
semi-circular DV supply unit (middle) and return grille (right) in the
Indoor Environmental Chamber
The space temperature was controlled by adjusting the off-coil temperature
and fan speed using the computer control system in the control room to
achieve the desired room conditions for each experiment. The air-conditioning
systems in Indoor Environmental Chamber are shown in Figure 3.3.

Figure 3.3 Schematic layout of Indoor Environmental Chamber and its
air-conditioning system

3.2.1.2 Breathing Thermal Manikin

A Breathing Thermal Manikin (BTM) (P. T. Teknik Limited, Denmark), as
shown in Figure 3.4, is employed throughout this doctoral research and is
primarily used to simulate an Infected Person (IP) in a healthcare environment.
However, in the case of the experiments for Objective 1 involving the
investigation of the ability of the PV-PE system to pull the PV air towards the
Healthy Person (HP), the BTM is used to represent the HP. For all other
experiments involving Objectives 2 and 3, the BTM is used for IP. The BTM
is shaped as a 1.68 m tall female, placed in a sitting position. The BTM has 26
body segments which can be heated to maintain the manikin surface at the
same skin temperature of a human being in thermal comfort. Since the
experiments simulate tropical conditions, the manikin is dressed in a clothing
ensemble corresponding to a typical level of approximately 0.5 clo, which is a
typical level of attire in air conditioning space in the tropics. The joints of the
manikin are movable and adjustable so that the manikin can be placed into the
right postures. There is an artificial lung system inside the thermal manikin
which enables the manikin to breathe so that it can simulate an Infected Person
who exhales the contaminated air. To simulate the normal breathing under
light work, the pulmonary ventilation volume is set consisting of 2.5 s
inhalation, 2.5 s exhalation and 1s pause. The pulmonary ventilation is 8.4
l/min, with a 10 times per minute breathing cycle. 8.4 l/min corresponds to the
breathing rate of an adult at a metabolic level during general light work
(Huang, 1977)The pulmonary ventilation is 8.4 l/min, or 0.84 l per breath. The
instantaneous ventilation is calculated at 0.84 l / 2.5 s = 0.336 l/s = 20.16
l/min.

BTM breathing mode consisted of exhalation through the mouth and
inhalation through the nose. The exhaled air is heated to 34 °C. The breathing
thermal manikin was controlled by a software that has four control modes,
namely, measuring only surface temperature of the body segments, constant
fixed surface temperature, constant heat flux from each body segment and heat

loss from manikin’s body following the well-known comfort equation as
shown in Equation 3.1 (Fanger 1972). During the experiments, the comfort
mode was used.
T
eq
= 36.4 – C(Q
t
) (Eq. 3.1)
Where:
t
s
- The skin surface temperature, [°C];
Q
t
- The rate of heat loss, [W/m
2
];
36.4 - the deep body temperature, [°C]; and
C - A constant depending on clothing, posture, chamber characteristics, etc
[m
2
· °C/W].


Figure 3.4 Breathing thermal manikin (left) and the control software
(right)

3.2.1.3 Thermal Manikin
The human body is not only a source of contaminants but also a heat source. A
study by Murakami (2004) concluded that the microenvironment around a

human body directly affects the quality of air exhaled and inhaled by a person.
The thermal plume generates an upward flow around the human body that
makes the air from below the head go up and reach the inhalation area. In
order to simulate this kind of thermal plumes generated by the difference of
temperature between the skin and the room air around a Healthy Person (HP),
a thermal manikin is used. The thermal manikin is shaped as a 1.78 m tall
male, which can be placed in both standing and sitting position. The thermal
manikin is wrapped with heating element in its head, arms, legs and torso to
provide heating to these surfaces so as to represent a more realistic human
body as shown in Figure 3.5. The thermal manikin temperature is controlled
by three parts: head and torso, arms, and legs. The temperature difference
between the set point and the one the control box targeted is 0.1 degree. The
accuracy of the temperature control system is around ± 5%.

Figure 3.5 Thermal manikin (left) and the control box (right)

3.2.1.4 Tracer-gas Analyser
Multi tracer gas techniques using sulphur hexafluoride (SF
6
) and Nitrous
Oxide (N
2
O) will be used to evaluate the performance of the PV-PE system. A
Multipoint Sampler INNOVA and INNOVA 1412 Multi-gas Analyzer (Figure
3.6) are used to measure the concentrations of sulphur hexafluoride (SF
6
) and
N
2
O at sampling points. Up to 12 tubes connect each channel on the

INNOVA multipoint sampler to the respective sampling point. The 12
channels converge into one: a three-way valve then directs the gas sample to a
gas monitor for analysis, or vents it to the waste-air outlet for purging the
sampling lines. While the gas monitor is measuring the sample, the next
sample line is purged. The gas monitor used together with the multipoint
sampler is INNOVA 1412. It utilizes photo acoustic infrared detection method
to determine the presence and amount of tracer gas present in the air. The
monitoring system is easily operated through either the front panel or the PC
software and is equipped with two standard interfaces: IEEE-488 and RS-232
(optional JV 0901 converter RS-232 to USB. These enable the monitor to be
integrated into automated process systems. Innova AirTech instruments
application software type 7300 was used to control all of the sampling and
monitoring functions remotely. The data was also recorded in this software.

Figure 3.6: INNOVA Multipoint Sampler and Multi-gas Monitor
3.2.1.5 Temperature, Relative Humidity, and Turbulence Intensity
Measurement Devices
The background air supply and return temperatures were recorded by HOBO
meters (Figure 3.7).


Figure 3.7 HOBO meter
Dantec Dynamics comfort Sense system, as shown in Figure3.8, is used to
measure the mean air velocity, temperature, turbulence intensity and Daft
Rating (DR) in the chamber. The Comfort Sense system consists of a main
frame with input channels for up to 16 probes. The omnidirectional probes
measure both air velocity and temperature. The software delivers statistical
results based on user-defined measurement cycles.

Figure3.8 Dantec Dynamics Comfort Sense System

As a summary, Table 3.1 shows the overview of the instruments required to
measure the parameters in this study. It also indicates the degree of accuracy
of each instrument of the data collected.
Table 3.1 Instrumentations
Parameter
Instrument
Accuracy
Room air temperature, mean velocity
and draft rating
Dantec Dynamics comfort
Sense system
Vel ± 0.02m/s
Temp ±1% of
readings
Return air temperature
HOBO meter
± 5%
Concentration of N
2
O, SF
6

Photo acoustic spectrometer
multi-gas analyzer
± 2%
Local air mean velocity, turbulence
intensity and draft rating
Dantec Dynamics comfort
Sense system
Vel ± 0.02m/s

Temp ±1% of
readings



3.3 Experimental Design
3.3.1 Ventilation Systems
The experiments are designed to simulate a consultation room in a healthcare
setting (such as hospitals or clinics) in tropical climates. It will involve three
different parts of the air distribution system.

The first part is the background air conditioning and air distribution system,
which is either MV or DV in the Indoor Environmental Chamber. The control
system in the control room is capable of switching between ceiling supply MV
system and DV system. The ceiling supply MV diffusers provide a typical
mixing ventilation air flow pattern in the chamber based on the Coanda
principle. The space temperature is controlled using a space thermostat in the
main supply duct. During the experiments, the ambient air temperature in the
chamber is maintained at 23°C.

The second part is the PV system that distributes 100% conditioned outdoor
air through the PV Air Terminal Device (ATD). Only one PV ATD is used in
this study: Round Movable Panel (RMP), which is shown in Figure 3.9. The
outlet of the ATD is a 100 mm diameter perforated panel with 50% free area
ratio. A perforated flow equalizer with 50 mm diameter is installed inside the
conical shaped cap of the ATD. It supplies PV air at 23°C and two different
flow rates (5 l/s and10 l/s). The PV air flow through each PV ATD is
individually controlled through the computer control system.

Figure 3.9 Round Movable Panel (RMP) PV ATD

The third part is the Personalized Exhaust (PE) system. Two types of PE
integrated chair are fabricated. One is called shoulder-PE, which has two local
exhaust devices with an adjustable opening integrated with the chair. These
chair PE devices are located behind and in the upper part of the chair. The
other one is called Top-PE, which has the inlet (suction) opening of the PE
device raised and extended well above a seated person so that the suction is
directly above a seated person’s head. The PE device is able to move up and
down in a range so as to be always at the optimal position according to the
height of the person. Each PE device is connected to a three speed external
rotor motor by the soft duct so as to exhaust the air out of the Indoor
Environmental Chamber. Flow rates through the PE devices, controlled by the
motor and the damper at 10 l/s and 20 l/s, provides a fairly comprehensive
assessment of the inhaled air quality in the microenvironment created by the
combination of PV ATD and PE. The shoulder-PE, top-PE and motor are
shown in Figure 3.10.











Figure 3.10 Top-PE (up-left), Shoulder-PE (Up- right) and the motor
(bottom)

The PE outlet is made of aluminium, with a round outlet having an inner
diameter of 95 mm. The PE has a damper inside. During the experiments, the
top-PE will be located 0.12 m above the manikin’ head while the shoulder-PE
is located 0.06 m away from the manikin’s face as shown in Figure 3.11. The
approximate location was chosen according to the CFD simulation to ensure
the micro-environment it created or covered could exhaust the exhaled air.
Before the start of the experiments, a smoke generator was also used to choose
the exact location for PE.


Figure 3.11 Location of Top-PE (left) and location of Shoulder-PE (right)

3.3.2Evaluation of the novel PV-PE system in terms of enhanced delivery
of PV air to the Healthy Person
It has been demonstrated that PV has a better performance in terms of
improving occupants’ Inhaled Air Quality (IAQ) in comparison with Total
Volume (TV) system alone (Melikov, 2004; Li et al. 2009). However, the PV
air terminal devices are almost fixed or have little flexibility to move. The
Healthy Person (HP) is likely to move out of the PV air range when he/she is
moving around the desk while remaining seated. 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 the shoulder-PE in terms of assisting in
pulling the PV air flow towards the seated person. Thus, in the case of a seated
person moving within certain limits in the workstation area, the shoulder-PE
will serve to act as a directional control for the PV air plume. The
experimental design of this study is to examine the possible effective range of
the PV-PE system in terms of pulling the PV air towards the occupants. For
this purpose, measurements of various parameters namely distance between
PV and PE devices, PV flow rate, PE flow rate and relative positions of PV

and PE devices, are conducted in the chamber. Furthermore, experiments will
be carried out in both MV and DV modes to examine the influence of different
background ventilation systems on the local air flow pattern with PV-PE
system, which is an important factor to be considered when designing PV-PE
systems.

During the experiments, the supply air temperature from MV or DV was set at
20 °C in order to achieve the room air temperature of 23 °C. The air change
rate (ACH) was 6. PV air was kept at 23°C. The position of PV ATD was
fixed, supplying PV air at a flow rate of 5 l/s or 10 l/s. The Breathing Thermal
Manikin is kept seated in the chair. In order to simulate a typical working
person at his/her desk, the chair was able to move around. When the chair
moves, the integrated PE device and the thermal manikin would also move
together with the chair. In this study, the chair is moved longitudinally to let
the Breathing Thermal Manikin be positioned at 0.2, 0.3 and 0.4 m from the
PV ATD; as well as moving in an arc, leaving from the thermal manikin
center line as 30°, 45° and 60°. The positions of the Breathing Thermal
Manikin during this study are shown in Figure 3.12.

Figure 3.12 Positions of the breathing thermal manikin
Considering the energy usage, draught discomfort, and the potential noise
level, a lower PE flow rate is always preferred. Previous CFD simulation show
that the shoulder-PE device is able to increase the amount of PV air in the
inhaled air of an occupant without causing high air velocity around facial area
at a flow rate up to 30 l/s (Yang & Sekhar, 2011). In this study, the PE flow
rate changes from 0 l/s to 10 l/s to 20 l/s. Details of the experimental
conditions are listed in Table 3.2.
Table 3.2. Experimental conditions
Cases
Background

ventilation
PV flow rate
(l/s)
PE flow rate
(l/s)
1
MV
5
0
2
MV
5
10
3
MV
5
20
4
MV
10
0
5
MV
10
10
6
MV
10
20
7

DV
5
0
8
DV
5
10
9
DV
5
20
10
DV
10
0
11
DV
10
10
12
DV
10
20

Tracer gas (SF
6
) measurements are performed to investigate the performance
of the PV-PE system in terms of the ability to pull the PV air towards the
occupant. The tracer gas is dosed in the air long before it entered the chamber
to achieve complete mixing of the tracer gas with the air supplied to the Indoor

Environmental Chamber as shown in Figure 3.13.


Figure 3.13 Tracer gas SF
6
cylinder and valve (left) and dosing point
(right)
SF
6
was dosed until the concentration measured in the chamber increased to
above 50 ppm in the return/exhaust air. The first results of tracer gas
concentration measurement used to analyze the performance of the system
with regard to inhaled air quality was taken when the concentration in the
return/exhaust air dropped to 50 ppm. The personalized air is kept free of
thetracer gas. The concentration of SF
6
is measured in the air inhaled by the
thermal manikin, in the air supplied to the chamber, in the return grill at
ceiling level, and in the air supplied by the PV system. The chamber is well
sealed to avoid any air/gas leakage. The samples in each sequence are
analysed one after another in a loop. Each location is sampled at least 10 times
to make reliable statistical analyses. The results of tracer gas concentration
measurement are averaged and analysed to examine the performance of
thesystem with regard to inhaled air quality. An index defined as Personal
Exposure Effectiveness (PEE) was calculated to evaluate the PV-PE system.
The PEE index expresses the percentage of personalized air in inhaled air. It is
derived from the following equation (Melikov et al., 2002):
(Eq. 3.2)
Where C
I,0

is the concentration of tracer gas in inhaled air without PV (ppm),
C
PV
is the concentration of the tracer gas in personalized air (ppm),which is 0
since the PV is supplying conditioned outdoor air, C
I
is the concentration of
the tracer gas in the inhaled air when PV is used (ppm). When PV is in use and
PE is not activated, the numerator of Equation 3.2 represents the reduction in
the concentration of the tracer gas in the inhaled air due to the supply of
conditioned outdoor air by PV and thus the PEE shows the effectiveness of PV
in terms of supplying PV air to the occupants; and PEE expresses the
effectiveness of PV-PE as a whole system when both PV and PE are activated.
This index is equal to one if the inhaled air consists of 100% of the PV air and
equal to zero if no PV air is inhaled. When PE is used, its effects are indirectly
assessed by the index since PE might cause the concentration of the tracer gas
in the inhaled air to reduce by pulling the PV air towards the zone of
inhalation.

The room air temperature, mean velocity and Draft Rating are recorded at
heights of 0.5 m, 1.25 m and 1.7 m using the DANTEC instrument as shown
in Figure 3.14a. The local air mean velocity, turbulence intensity and Draft
Rating of the inhaled air are recorded in the inhaled air region at heights of
1.35 m as shown in Figure 3.14b. The local air mean velocity, turbulence
intensity and Draft Rating of the face region is also recorded at a height of 1.4
m just besides the neck/ear region.

PVOI
IOI
CC

CC
p
−
−
=
,
,
ε

a). Set up of the DANTEC instrument for room air velocity and Draft
Rating


b) Set up of the DANTEC instrumentfor local air velocity and Draft
Rating
Figure 3.14 Set up of the DANTEC instrument

3.3.3 Evaluation of the novel PV-PE system in terms of preventing the
transmission of exhaled contaminated air during normal consultation
process
The normal consultation procedure between a Healthy Person (HP) and an
Infected Person (IP) may pose a risk of the transmission of infectious diseases.
In order to exhaust the exhaled contaminated air before it mixes with the room
air, experiments are designed to explore the two types of PE in terms of
preventing the airborne transmission disease during normal consultation
procedure. In this case, the Breathing Thermal Manikin and the Thermal
Manikin are sitting face to face at the center of the Indoor Environmental
Chamber with a distance of 0.6 m as shown in Figure 3.15. During the
experiments, the room air temperature and PV air temperature are kept at 23°C.

Infected Person Healthy Person Infected Person Healthy Person

Figure 3.15 Positions of the thermal manikins

Measurements of various parameters namely PV flow rate for Healthy Person,
PE flow rate for Infected Person, and PE flow rate for Healthy Person, are
conducted in the chamber. Details of the experimental conditions are listed in
Table 3.3. Each case is carried out in both MV and DV modes to examine the
influence of different background ventilation systems on the local air flow
pattern with PV-PE system, which is an important factor to be considered
when designing PV-PE systems.

Table 3.3. Experimental conditions
Cases
Figure (Plan)
Figure (Elevation)
PE
flow
rate
for IP
(l/s)
PV
flow
rate
for HP
(l/s)
PE
flow
rate
for HP

(l/s)
A (Base case)


0
0
0
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5



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5
0
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!



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5
20
AIpHp
!"#$
!

0
5
20
AIpHp
10



0
10
0
AIpHp
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!"



0
10
20
AIpHp
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10
20
AIp

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Hp


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0
0
AIp
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Hp


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0
0
AIp
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Hp
5


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5
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Hp
5

10
5
0
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Hp
!!!"
!



10
5
20
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Hp
!!"
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10
5
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10

10
10
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Hp
10



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10
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Hp
!!!"
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10
10
20
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Hp
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10
10
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0
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Hp


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0
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20

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Two types of tracer gas are used during the experiments. SF
6
is dosed in the
supply air of the background air distribution system i.e. ceiling supply MV or
the DV system, and will represent a contaminant release into the room air. In
order to have the tracer gas well mixed with the supply air, the tracer gas is
dosed in the air before it entered the chamber. The PV air is conditioned 100%
outdoor air without any tracer gas. The exhaled air from the Breathing
Thermal Manikin (Infected Person) is also marked using the second tracer gas
N
2
O, which is used by Qian et al. (2006). The air exhaled from the mouth of
the Breathing Thermal Manikin is heated to 34°C (Hoppe, 1981). The heated

air is exhaled through the mouth and room ambient air inhaled through the
nose, so that a shortcut of exhaled air containing a tracer gas to the inhaled air
can be avoided. The dosing set-up consisted of a gas cylinder, 2-step reduction
valve, and a mass flow controller as shown in Figure 3.16.The mass flow
controller has a regulated range of 0 to 50 ml/min. During the experiments, 50
ml/min is set for both SF
6
and N
2
O.





Figure 3.16 Tracer gas dosing set-up: N
2
O cylinder (Top-left), N
2
O valve
(Top-right), SF
6
cylinder and valve (bottom-left), mass flow controller
(bottom-right)

Several tracer gas sampling points shown in Figure 3.17 are distributed and
include the following:

1. Inhaled air - At the upper lip at a distance of 5 mm from the face of the
HEALTHY MANIKIN or Healthy Person, as reported by Melikov and

Kaczmarczyk, (2007), air sampled at the upper lip at a distance <0.01 m from
the face will ensure measurement of pollution concentration as those measured
in the inhaled air.
2. Exhaled air - Just inside the mouth of the INFECTED MANIKIN or
Infected Person
3. Inside the background air supply duct
4. Inside the background air return duct
5. Outside the Indoor Environmental Chamber

The locations of the sampling points are shown as S1 to S5 in Figure 3.18. A
gas monitor based on a photo-acoustic infrared detection method is used to
measure tracer gas concentration. As the Infected Manikin keeps exhaling
contaminated air (N
2
O), and the background system cools the Indoor
Environmental Chamber with 90% recycled air which also consists of N
2
O.
The concentration of tracer gas inside the chamber will keep increasing and as
a result there is no steady-state condition reached. Since the experiments are to
simulate the normal consultation procedure between a Healthy Person and an
Infected Person, the tracer gas dosing is started in each experiment as the
Infected Person enters and is seated. The experimental duration is 30 minutes
which is about the same as maximum consultation time. Readings are taken at
10 minutes, 20 minutes and 30 minutes. At the end of each experiment, the
dosing system is shut down. However, all the heat sources in the chamber
including the Thermal Manikin and the Breathing Thermal Manikin remained
in operation to maintain the thermal environment in the chamber. The next
experiment starts until the gas concentration decayed to the level same as that
in the atmosphere detected by sampling point outside the Indoor

Environmental Chamber.




Figure 3.17 Tracer gas sampling points