Proceedings: Indoor Air 2002
STUDY OF AN INNOVATIVE PARTITION-TYPE PERSONAL
MODULATION AIR-CONDITIONING SYSTEM
H Chiang*, CC Su, CS Pan and FH Tsau
Energy & Resources Laboratories, Industrial Technology Research Institute, Taiwan, R.O.C
ABSTRACT
This paper proposes a new personal air-conditioning system, which modifies a common partition
used in offices to a partition-type fan-coil unit (PFCU) with inlets and outlets on its surfaces.
Chilled water is supplied as the cooling energy, and is delivered to the partitions by pipelines
incorporated into the structure. Hence, conventional air conditioning systems using ceiling-based
air diffusers for open-plan offices may be dispatched into several small individual systems
controlled by the occupants. Another advantage of the new system is that a raised floor system is
not required, so the applicability to retrofit buildings is very convenient. In this study, the
transient variations of room temperature distribution and the skin temperature of a thermal
manikin were measured in a real-scale climatic chamber. The preliminary test results of a
prototype system have shown that the PFCU system has many promising features and deserves
further development.
INDEX TERMS
PFCU, Personal air-conditioning system, manikin, temperature distribution
INTRODUCTION
For decades, personally modulating of thermal environment has always been an interesting
research topic in both industrial and academic sectors because of their benefits in increasing
thermal comfort, improving indoor air quality and reducing energy consumption. Underfloor air
distribution systems (UFAD) and task/ambient air-conditioning systems (TAC) are the wellknown applications in this field. The rapid development of these systems was mainly due to the
structural design of intelligent buildings (Caffrey, 1988). It provided the opportunity for new
development of heating, ventilation and air-condition (HVAC) technologies. Especially, the
raised floor system, a typical element of intelligent buildings, created an underfloor plenum to
deliver conditioned air to the workspaces through the terminal devices on the floor or at the
desktop. In comparison with the conventional ceiling-based air distribution systems, UFAD and
TAC system have the benefits to allow the occupant to control the volume and the direction of
the airflow to achieve more comfortable personal environment while several barriers do exist in
widespread applications. The detailed reviews of these systems can be found in the literatures,
such as Bauman and Webster (2001), Shute (1995), Heinemeier, Schiller and Benton (1990).
Using floor diffusers as the air terminal devices is the most common practice of UFAD system.
The air supply units on the raised floor can be selectively allocated in the most crucial areas for
improving thermal comfort or removing excessive cooling loads. They can also be moved to
*
Contact author email: hchiang@itri.org.tw
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Proceedings: Indoor Air 2002
other places when the reconfiguration of buildings is needed. Thus, it provides flexibilities in
terms of space and time. Nevertheless, there are still some concerns of the possible discomfort
caused by draft and vertical temperature differences. The research efforts (Matsunawa, Lizuka,
and Tanabe, 1995, Hanzawa and Nagasawa, 1990) have been introduced to improve the design of
these air distribution devices for the satisfaction of occupants.
In order to give occupants more control capability over their personal environments, desktop airconditioning (DAC) system has recently drawn great attention (Han et al., 2001, Cho, Kim and
Zaheer-uddin, 2001, Lomonaco and Miller, 1997). DAC system supplies conditioned air from
the desktop diffusers. In most cases, the supplied air is provided by an air duct connected to the
underfloor plenum with or without the drive of a local fan. Hence, it belongs to one branch of the
UFAD system, but it offers more benefits than the floor-based air distribution systems in terms of
quicker response to personal need, higher ventilation efficiency and increasing productivity.
In this paper, we propose a new personal air-conditioning system, which can further decentralize
a traditional ceiling-based fan-coil system into individual workspaces. This system changes the
partition used in offices into a localized fan-coil unit with inlets and outlets on its surfaces. Room
air, drawn in at the lower level by a small fan installed inside the partition, is cooled by an air-towater heat exchanger and then discharged into the room from the outlets at the upper level. The
air is mainly re-circulated within the workspace. If outside air is supplied to the partition through
an air duct connected to the plenum, it can substitute portion of the circulated air in the
workspace. Hence, the system is very suitable to accomplish the concepts of the personalized
ventilation proposed by Melikov, Cermak and Mayer (2001), Fanger (2001), and Hiwatashi et al.
(2000) and the dedicated outside air system by Mumma (2001) to improve the ventilation
effectiveness and the indoor air quality.
Depending on the cooling demand of the workspace, several PFCU modules can be assembled
together to divide the office space. The chilled water pipes or even the air ducts can be fitted in
the partitions and joined with several PFCU modules. The chilled water pipes are then connected
to a central chiller plant or several packaged chilling units. They can also be connected to a hot
water supply system for heating purposes. It should be noted that, in this design, a raised floor
system is not required, so its applicability to retrofit buildings is very convenient. It is especially
attractive to the markets, as the economy no longer favors the growth of building constructions.
The purpose of this paper is to justify the idea of this design. A prototype system has been built in
our laboratory to examine the aforementioned benefits and to explore the potential problems for
further improvements.
METHODS
In this study, a climatic chamber (about 4.6 x 3.7 x 2.7 cu. meters) was used to simulate a typical
workspace as shown in Figure 1. The chamber has two exterior walls adjacent to a controlled
exterior environment in 30℃ so to reflect the typical outdoor conditions in summer. The other
two interior walls are adjacent to a walkway and a test room both without air-conditioning. The
test chamber contains 480 points of T-type thermocouple forming a 3-D matrix to measure the
room temperature.
The furniture arrangement in the test chamber is illustrated in Figure 2. Five partitions with
different widths (but equal height of 1.4 m and thickness of 6 cm) were assembled to form an
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Proceedings: Indoor Air 2002
individual workspace (2.4 m x 2.5 m) in the test chamber. Among these partitions, two of them
were PFCU modules. Each contained a cooling coil and a cross-flow fan. The maximum air
volume supplied by each module was approximately 60 L/s and it corresponded to an air speed of
1.0 m/s at the outlets that has the dimensions of 60 cm in width and 10 cm in height. The water
with constant temperature of 7℃ was supplied to the cooling coils through insulated
polyethylene tubes inside the partitions.
ADJ ACENT TEST ROOM
OUTDOOR CLI MATE ZONE
OBSERVATI ON
WI NDOWS
I NDOOR WALKWAY
ADJ ACENT TEST ROOM
ORI ENTATI ON: TOP VI EW
UNI TE: CENTI METER
SCALE: NONE
SI ZE OF OFFI CE DESK:
140x60x73
SI ZE OF COMPUTER DESK:
70x49x78
OUTDOOR AI SLE
Ther e ar e 480 poi nt s of t her mocoupl es cont ai ned i n
t hi s r oom vol ume. Each cr os s mar k r epr es ent s s i x poi nt s
of t her mocoupl es ar r anged i n ver t i cal di r ect i on.
Figure 1. Floor plan of the test chamber
Figure 2. Arrangement of workspace and PFCU system under tests
A thermal manikin consisting of 16 body parts was used to simulate a human body. It should be
noted that the manikin only measures the sensible heat loss to the environment. The manikin sat
on an office chair in front of a desk. The core temperature of the manikin was controlled to 36.5
℃ and the transient skin temperature of each body part was measured. The manikin was dressed
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Proceedings: Indoor Air 2002
as in Figure 2 and the Clo value of its garment was about 0.4. A personal computer was arranged
next to the manikin to simulate an actual office set-up.
The test of PFCU modules was started from a uniform room temperature controlled at 30℃. In
the test, a parallel air conditioning system for the base cooling of the entire test room was not
considered, although some research works proposed the design concept. However, our paper is
focused upon the transient response of local environment around the manikin.
RESULTS
In order to analyze the response time of the PFCU system, several extra points of temperature
measurement were supplemented. These points were located at the inlets and outlets of the PFCU
modules, the vicinity of the manikin and the outside of the partitioned zone. The measured results
are plotted in Figure 3, accompanied with the transient variation of the mean skin temperature of
the manikin. As the system was turned on, the air temperature at supply outlets decreased rapidly
to around 19℃. The temperature of workspace around the manikin also approached to a comfort
temperature of 26℃ within 5 minutes. The mean skin temperature of the manikin reached its
steady-state temperature within 20 minutes. The transient period of the PFCU system was
comparatively shorter than the previous measurement (Hsu et al., 2000) for the traditional wallmounted air conditioners, which took about 30 minutes to reach the stable mean skin temperature
of the manikin.
36
35
32
30
Skin temperature
34
in open space
28
at inlet
26
33
in workspace
24
32
22
31
20
at outlet
18
0
500
1000
1500
2000
Average Manikin Skin Temperature (C)
Selected Temperature Points (C)
34
30
2500
Time (Sec)
Figure 3. Transient variation of the skin temperature of the manikin and some critical points
The steady-state temperature of each body part of the manikin is shown in Figure 4. The head and
the hands had the lowest temperature due to cold air blowing directly on the bare surface of the
manikin. The back and the hip had the highest skin temperature because the chair prevented heat
dissipation from these portions. The largest temperature difference among these body parts was
found to be around 2.5℃. Hence, the local discomfort resulted from the temperature difference
was not significant for the tested system.
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Proceedings: Indoor Air 2002
Figure 5 illustrates the temperature contours for the horizontal plane at the height of 1.1m (i.e. the
workspace) and the vertical plane in which the manikin sat. The supply air discharged from the
two PFCU modules can be clearly viewed in the figure and the two air streams merge at where
the manikin located. In practice, an occupant can adjust the louvers of the outlets to change the
direction of airflow upon personal preference. The figure also shows that the PFCU modules
affect only the workspace enclosed by the partitions and cause little effect to the space outside the
partitions. Therefore, the PFCU can be viewed as a personal device in an open-plan office to
satisfy individual needs of occupants for air conditioning.
36
35.5
35
34.5
34
33.5
33
32.5
32
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31
Figure 4. Steady-state skin temperature of each body part of the manikin
300
400
350
200
50
26
27
26
27
150
100
29
28
29
28
28
26 4
2
2
2 2
2 43
150
28
2245
28
100
28
27
29
30
200
Y
Z
25
25
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22
25 6
2
300
2
2245 7
250
29
27
50
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29
100
28
100
200
X
300
400
(a) Temperature contours at the horizontal
plane in height of 1.1m
200
Z
300
(b) Temperature contours at the
vertical plane where manikin sat
Figure 5. Temperature contours in test chamber
CONCLUSIONS
The paper illustrates a new personal air-conditioning system, which relies on a partition-type fancoil unit for individual comfort control. The experimental results in a laboratory test chamber
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Proceedings: Indoor Air 2002
have indicated that such a system provides two advantages: the fast response to occupant control
and the flexibility of modulating the air supply conditions. Other benefits can also be expected if
the system applies the proven technologies, such as: occupancy-based air-conditioning control,
demand control ventilation, personal ventilation, off-hours cooling supply, etc. Although the
preliminary results have shown the feasibility of this new system, some concerns relevant to
technical and ethical issues still demand further studies in the future. These include the solutions
of flexible piping, draining of condensate from cooling coil, and so on.
ACKNOWLEDGEMENTS
The authors like to express their gratitude for the support from the Department of Industrial
Technology, The Ministry of Economic Affairs, Taiwan, R.O.C.
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