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Research Article Indoor/Outdoor Airflow
and Air Quality
E-mail: Liag@xauat.edu.cn
The impact of various hood shapes, and side panel and exhaust duct
arrangements, on the performance of typical Chinese style cooking
hoods
Yujiao Zhao, Angui Li (), Penfei Tao, Ran Gao
School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, Xi’an, Shaanxi 710055, China
Abstract
In Chinese commercial kitchens, a large amount of moisture and heat is produced and must be
removed, which can require ventilation rates resulting in huge levels of energy consumption.
Excessive airflow rates can increase unnecessary energy consumption and system life-cycle costs.
For many middle and small scale commercial kitchens in China, the indoor, thermal environment
is far worse than acceptable levels. The use of an efficient kitchen hood is essential to ensure a
comfortable working environment and better energy conservation. In this study, many types of
hood shapes and side panels were developed to improve the capture efficiency of traditional
Chinese style cooking hoods. The arrangement of the exhaust ducts was also investigated. Basic
site tests and computational fluid dynamics (CFD) analysis were conducted. The simulated results
showed that increasing hood volume did not improve capture performance. However, side panels
did improve the capture efficiency, especially at higher positions. In addition, when the exhaust
opening was located at the rear of the hood, the hood capture efficiency improvement was
enhanced.
Keywords
capture efficiency,
kitchen ventilation,
indoor thermal environment,
traditional Chinese style of cooking hood
Article History
Received: 24 April 2012
Revised: 1 August 2012
Accepted: 3 September 2012
© Tsinghua University Press and
Springer-Verlag Berlin Heidelberg
2012
1 Introduction
As a result of greater understanding of the importance of
indoor air quality (IAQ) to health, comfort and productivity
of the workforce, concerns over IAQ have increased during
recent years. Working conditions are particularly demanding
in a commercial kitchen (Kosonen et al. 2006). A hot and
uncomfortable kitchen contributes to productivity loss,
employee turnover, and the eventual loss of profits for the
restaurant operator (Livchak 2005). In a commercial kitchen,
a high ventilation rate is necessary to exhaust both the com-
bustion gases and the contaminants generated by cooking.
China, with nearly 1.3 billion people, has the largest
population in the world, consuming copious quantities of
cooked foods every day. As China’s economy expands, the
catering industry is becoming an important component of
the service sector of the economy. For example, there are
currently over 51 thousand restaurants in Beijing (Beijing
Statistics Bureau 2005). In 2010, catering sales were ¥ 20 012
billion, which was two times the sales level in 2005. Great
attention should be paid to the working conditions in
Chinese commercial kitchens, and the indoor air pollution
generated by the cooking processes.
Chinese kitchens utilize quite complicated culinary skills
in delicately controlling the cooking process by varying the
heat, temperature and cooking time. China’s local dishes each
have their own typical characteristics, which are generally
divided into eight regional cuisines. Each cuisine might
involve preparing 200 to 300 dishes with variations of 24
common cooking techniques. A wide range of seasonings are
applied (Ishige 1992), especially in commercial kitchens,
and many dishes require large quantities of oil or lard for
cooking. The resulting emissions from the multitude of
different cooking techniques make a quite significant con-
tribution to indoor air pollution in China. Oils are usually
first heated to high temperatures in a wok, to reduce noxious
odors, resulting in large quantities of emissions (He and Hua
2004). The emissions include smoke, grease particles and
vapor, all of which are products of combustion, heat, and
moisture (Bramfitt 2006).
BUILD SIMUL (2010) 3: 273– 280
DOI 10.1007/s12273-012-0096-1
Zhao et al. / Building Simulation
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The use of an efficient kitchen hood is essential to
ensure provision of a healthy, comfortable and energy
efficient working environment (Kotani et al. 2009). A
number of domestic documents have recommended possible
solutions. ASHRAE Research Project RP-1202 (Swierczyna
et al. 2005) quantified the effect of the position and/or
combination of the apparatuses under an exhaust hood, on
the minimum capture and containment (C&C) rate. Effects
of side panels, front overhang, and rear seals were also
investigated. The results can help designers to optimize
the performance of commercial kitchen ventilation (CKV)
systems. Furio (1996) used experiments to evaluate the
velocity fields induced in the proximity of local exhaust
hoods with circular or rectangular (right quadrilateral)
openings. Kosonen and Mustakallio (2003) used AirPak 2.0.6
to evaluate the effect of a capture jet on the contaminant
removal efficiency of a ventilated ceiling. This jet helps to
direct heat and air impurities towards the exhaust intake.
The average contaminant level is about 50% lower with the
capture jet. Lim and Lee (2008) conducted a 3D numerical
analysis. They investigated the airow characteristics in a
kitchen with and without a separation plate set, and with
different separation plate shapes. Compared to the initial
model, which had no separation plate, there was a 1.4%–1.9%
increase in efficiency of temperature distribution, and a
9.4%–11.9% increase of CO2 concentration distribution.
Only a few studies of traditional Chinese style cooking
hoods have been published. Lai (2005) used experimental
methods to investigate side exhaust systems. The results
showed the influence of different exhaust configurations on
overall exhaust performance. In a full-scale, model kitchen,
Chiang et al. (2000) investigated side exhaust systems using
design and experimental methods. However, these studies
all focused on residential kitchens, instead of the thermal
environment typical in commercial kitchens. Few studies, if
any, have addressed the issue of how to make improvements
to the traditional Chinese style cooking hood.
The hood capture and containment rate is the basic
index for assessing the ventilation performance of a local
exhaust hood. “Hood capture and containment” is defined
in American Society for Testing and Materials, ASTM 1704
Standard Test Method (ASTM 1999) for the Performance of
Commercial Kitchen Ventilation Systems, as “the ability of
the hood to capture and contain grease laden cooking vapors,
convective heat and other products of cooking processes”.
Hood capture refers to collection and containment inside
the hood reservoir, without allowing any overflow to the
open spaces.
There aren't any threshold values for capture efficiency
in existing kitchen ventilation design guides and standards.
In design practice, the main purpose is to sufficiently extract
the convective heat and contaminants from the occupied
zone with a minimal air flow rate.
In the United States, ASTM Standard F1704-99 (Smith
et al. 1995) has provided a foundation for determining the
C&C performance of kitchen hoods. With this method,
hood C&C efficiency for different cooking processes has
been studied. One current limitation of ASTM F1704-99, is
that it was designed for exhaust-only style hoods, operating
in a laboratory with a mixing style air-conditioning system.
Applying ASTM 1704, the heat gain and C&C exhaust values
were determined for a variety of single apparatus, under
a canopy hood (Knappmiller and Schrock 1997). The
measurement method for capture efficiency under actual
room conditions was also developed，because the capture
efficiency in actual room conditions was different from that
described above (Kurabuchi et al. 2007).
In Europe, the German-based Verein Deutscher
Ingenieure (VDI) Standard 2052 (1999) is used to determine
the C&C requirements for hoods, based on the convective
airflows from cooking appliances. The standard considers
the convective heat load, the distance between the appliance
and hood, and the area of the appliance. A supply con-
figuration factor is also considered. Using a low-velocity
supply solution, for example, leads to a lower extracted
airflow rate than with traditional mixing ventilation.
Some codes (AS 2002) use an engineered procedure
for kitchen hood design. The engineered procedure is a
performance-based method that allows the utilization of
suitable technology to achieve the designated targets. The
solutions should be reviewed in the field or proven with
appropriate calculations.
There are quite a number of general local exhaust
systems, and C&C efficiency definitions for kitchen hoods
in literature (Olander et al. (2001) and Li et al. (1997));
however, there has not been much published on methods
and analysis relating to typical Chinese commercial kitchen
ventilation systems.
The capture efficiency used throughout this paper is
that of a confined flow system derived by Wolbrink and
Sarnosky (1992). In their derivation, a two-zone mixing
model is assumed as follows:
ro
cco
1cc
ηcc
-
=-
- (1)
where:
c
c=concentration of contaminant in the exhaust (kg/m3)
r
c=concentration of contaminant in the occupied zone (kg/m3)
o
c=concentration in the outdoor ambient air (kg/m3)
This is a very simple formula. It has been successfully
applied in many studies that have evaluated the performance
of range hoods. In this study, the occupied zone is defined as
Zhao et al. / Building Simulation
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1.8 m from the floor and 0.3 m from the wall or appliances.
It is assumed that this zone is perfectly mixed.
In this paper, the capture efficiency of the traditional
Chinese style cooking hood was analyzed using CFD
(computational fluid dynamics) simulations. In addition, the
design of a hood with high efficiency in a case study kitchen
was also investigated. This was supported by the site tests
undertaken in recent research by Li et al. (2012). The site
tests were conducted in a well operated, Chinese restaurant,
with seating for more than 100 people at a time.
The objective of this study was to quantify the impact that
the hood shapes, side panels and exhaust duct arrangements
had on the minimum C&C exhaust rate.
This is a logical continuation of the study by Li et al.
(2012) on the impact of ventilation systems on the efficiency
of a typical Chinese commercial kitchen. In the previous
study, it was demonstrated that the mixed ventilation system
in typical Chinese commercial kitchens, especially without
a mechanical air supply system, could not effectively remove
the waste heat and impurities.
2 Case study kitchen
The site tests were conducted in Xi’an, China, in a Chinese
commercial kitchen where various cooking techniques were
utilized. Due to the expensive initial and maintenance costs,
many middle and small scale, commercial kitchens in China
lack a mechanical air supply systems, and make-up air is
supplied by infiltration. In those cases, thermal comfort is
harder to achieve. Figure 1 shows the layout of the case study
kitchen and the measurement locations. The black range
was on-fired during the cooking mode.
The parameters of the case study kitchen are presented in
Table 1.The cooking unit was 900 mm ´1200 mm ´800 mm,
and consisted of a steamer, six heavy-duty, burner ranges
and six pots. The surface temperatures of the appliances
were about 300℃. During the investigation, the weather
was rainy and wet, with daytime temperatures near 26℃,
and 65%–75% relative humidity (RH) during both days and
nights. The wind speed, below 5 m/s, was calm to slightly
breezy, for the majority of the time.
Figure 1 shows the layout of the case study kitchen. The
cooking ranges are located in-line, against the wall, under a
wall-mounted, canopy hood, which is the typical arrangement
in a Chinese commercial kitchen. We chose to investigate
CO2 as the main contaminant in evaluating the performance
Fig. 1 The layout of the case study kitchen and the measuring points
of kitchen ventilation systems. The kitchen was divided into
three test zones. A distance encompassing 1 meter from the
cooking ranges comprised Zone 1. Zone 2 begins at the end
of Zone 1 and continues for 3 meters, and the remaining
area comprised Zone 3. The measurement points were located
at 1.5 m above the floor in each zone. The measurements
were taken before cooking and during rush hours, for both
lunch time, near noon, and dinner time, at night, in order
to reflect the differences between them. A sample was also
collected outside. Table 2 presents the indoor test results
for the case study kitchen.
The front lower edge of the hood of the kitchen overhang
is 1.8 m as measured vertically from the finished floor. The
cross profile of American or European style cooking hoods
is usually rectangular. The traditional Chinese style cooking
hoods are quite different. In order to prevent cooking
grease from adhering to the hood and then falling back into
the wok, the front lower edge of the hood is designed at a
30° angle. The photographs of the two types of hoods are
shown in Fig. 2.
The exhaust airflow rate measurement in the case study
kitchen was based on the face velocity method. In this
method, the air exhaust rate is calculated by capture velocities
and the projected area of the kitchen appliance.
The capture efficiency was studied in the case study
kitchen. CFD simulations were conducted of the different
hood shapes, side panels, exhaust duct arrangements and for
air flow rates of 6000, 8000, 10 000, 12 000 and 14 000 m3/h,
and then compared with actual measurements.
Table 1 The parameters of the case study kitchen
Dimensions of the kitchen Dimensions of the exhaust hood The number of cook Fuel used for cooking Oil used for cooking Exhaust air flow rate
Length: 10 m
Width: 8.5 m
Height: 3.5 m
Length: 8 m
Height: 0.4 m 7 Natural gas Peanut oil 8920 m3/h
Zhao et al. / Building Simulation
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3 CFD Setups
The CFD simulations in this study were conducted using
AirPak 3.0. The site tests were carried out in a separate
study (Li et al. 2012). In this investigation, the standard k-
model was employed for turbulence closure and the ideal
gas law for modeling buoyancy, respectively. The standard
wall function provided by the software was used for the
wall. All simulations were performed at a steady state. In all
cases, the segregated solver was used to obtain results for
flow, energy and turbulence throughout the computational
domain. AirPak’s surface to surface, blackbody assumption
model was utilized to calculate the radiant heat transfer
between the heat source and room surfaces.
First order upwind scheme discretization of governing
equations gives much better convergence than a second order
scheme, so in this study the first order upwind scheme was
used. The body force weighted scheme, suitable for high
Rayleigh number, natural convection flows, was used for
discretization of pressure. The pressure-velocity coupling
was achieved by a SIMPLE algorithm. In order to obtain
converged results, the specific under relaxation factors for
the segregated solver were modified.
Grid size is directly related to the quality of the predicted
result. Smaller grid size means slower convergence, but
higher predicted quality, while larger grid size often leads to
bad convergence. The case study kitchen was divided into a
hexahedral grid system, with about 1 307 936 cells and local
Table 2 Comparison between idle mode and cooking mode of case study kitchena
Test zones Zone 1 (1 m within the
cooking range） Zone 2 (3 m wide and 1 m
away from cooking range)
Zone 3 (the rest area)
Maximum 27.8/53.0 26.9/30.8 28.2/32
Minimum 26.9/31.5 24.8/29.7 22.5/30.2
Mean 27.2/42.9 25.8/30.3 25.9/30.9
Temperature (℃)
SE b 0.4/1.5 0.3/0.5 2.5/0.8
Maximum 70.3/71.5 79.8/70.2 72.8/75.8
Minimum 65.6/59.8 68.8/58.1 65.5/66.8
Mean 67.4/65.7 74.4/63.5 68.6/70.2
Relative humidity (%)
SE 1.5/2.3 2.6/3.3 3.0/4.1
Maximum 0.20/0.31 0.24/0.33 0.26/0.31
Minimum 0.09/0.13 0.12/0.04 0.02/0.05
Mean 0.16/0.21 0.16/0.19 0.13/0.16
Velocity (m/s)
SE 0.05/0.08 0.04/0.13 0.09/0.11
Maximum 673.0/2145.0 710.0/918.0 813.0/1039.0
Minimum 586.0/725.0 578.0/812.0 502.0/611.0
Mean 610.0/1530.0 655.0/873.0 632.0/907.0
CO2 concentration (ppm)
SE 21.6/21.3 26.1/35.9 24.9/18.8
a Idle mode/cooking mode
b SE: standard error
Fig. 2 Two types of cooking hood
Zhao et al. / Building Simulation
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refining mesh in critical regions. Based on grid refinement
studies, this mesh was deemed to be sufficiently fine to capture
all the concentration distribution and significant flow features.
It is important to generate high quality grid layouts near the
supply units and the heat sources (Chen and Srebric 2001).
In this study, the grid layout near the kitchen appliance and
the hood was more dense, to improve the accuracy of the
calculations. The size of the grid near the kitchen appliance
and the hood is 0.1 m´0.1 m´0.1 m, while the size of the
grid in the other region is 0.2 m´0.15 m´0.2 m.
The boundary conditions of the heat gains are determined
using the known heat flux of the kitchen appliances. The
total heat gain is 27.3 kW. In the calculation, the emission
factors utilized were based upon the surface materials. For
the surrounding walls and hearth, they were set to 0.9 and
0.21, respectively.
Commonly used boundary conditions, i.e., an inlet
boundary and a pressure boundary, were applied to the air
inlet and outlet, from the ventilation system. The air was
supplied from the lower part of interior doors, at a height
of 800 mm from the floor. The kitchen appliances were
modeled for heat gain. The pollution source in the simulations
was CO2. In the kitchen, one heavy duty burner range at
the right hand side of the cooking range, and one steamer
at the left hand side of the cooking range, were used during
cooking mode. Table 3 specifies the boundary conditions.
A diffusion-convection equation was utilized to predict the
local mass percentage of the pollution.
Commercial CFD codes normally have a default con-
vergence criterion, and when the residual is below that
criterion, convergence to the solution is assumed. In this
investigation, the convergence criteria used (1´10–4) is based
upon the recommendation of AirPak.
3.1 Hood shape specifications
Hood capture refers to getting the contaminants into the
hood reservoir, while containment refers to keeping those
products in the hood reservoir and preventing them from
spilling out.
Traditional Chinese style cooking hoods are quite
different from American or European styles. In order to fully
understand the influence of the hood volume on capture
efficiency, 21 hood shapes were investigated in this study
(shown in Fig. 3). Case 1 represents the traditional Chinese
style of cooking hood. Chinese kitchens utilize quite com-
plicated culinary skills, delicately controlling the cooking
process by varying the heat, temperature and cooking time.
A wide range of seasonings are applied (Ishige 1992),
especially in commercial kitchens, and many dishes require
large quantities of oil or lard for cooking. Therefore, the
emissions from different styles of cooking operations might
make a quite significant contribution to indoor air pollution
in China, particularly the fumes emitted from vegetable oils
utilized during stir frying or deep frying. To avoid the
captured fats running back down the hood and falling into
Table 3 The boundary conditions of the simulated cases
Temperature
(℃) Velocity
(m/s) Pressure
(Pa) Airflow rate
(m3/h) Calorific value
(kJ/h) CO2 concentration
(ppm)
Entrance 30.3 0.31 Not needed Not needed
—
300
Stair inlet 30.5 0.30 Not needed Not needed
—
300
The other inlets
—
—
—
Pressure inlet
—
—
Exhaust hood
—
—
—
9000
—
—
Exhaust at ceiling height
—
—
—
960
—
—
Heavy duty burner range
—
—
—
1.67´105 50 000
Streamer
—
—
—
—
2.15´105
—
Fig. 3 Schematic of 21 hood shapes
Zhao et al. / Building Simulation
6
the wok, the front lower edge of the hood is designed at a
30° angle, which directs captured, dripping fats down along
the edge of the hood, into a drain channel that flows to the
collection trap. The grease filter and the front edge of the
hood constitute a triangle that would affect exhaust efficiency
because of the small hood volume. American or European
style cooking hoods were represented in Case 21. The cross
profile of American or European style cooking hoods is
usually rectangular.
To represent a generic design, the case study hood did
not have additional, performance enhancing features, such
as flanges, along its perimeter.
3.2 Exhaust duct arrangement specifications
In this study, we investigated two different exhaust duct
arrangements. The exhaust opening was either in the upper
side of the hood or in the rear of the hood. In the rear
arrangement, exhaust air ducts were connected to openings
in the back wall. In the more common upper side
arrangement, exhaust air ducts were connected to openings
above the ceiling. Figure 4 presents the schematics of the
two exhaust duct arrangements.
Fig. 4 Schematic of two exhaust duct arrangements
3.3 Side panel specifications
Six different side panel configurations were evaluated during
the study, three rectangular side panel designs and three
triquetrous side panel designs. Each rectangular side panel
had one homologous partial side panel. The rectangular side
panels had vertical and horizontal dimensions of 1.1 m´
1.0 m, 0.9 m´1.0 m and 0.7 m´1.0 m. The triquetrous
side panel had equal vertical and horizontal dimensions with
the homologous rectangular side panel, and tapered from
the front upper corner to the lower rear corner, which resulted
in an edge that was homologous. A schematic of six side
panels is shown in Fig. 5.
4 Results and discussions
Average contaminant concentrations are calculated for a
9.4 m´7 m´1.8 m volume. In the calculation, the volume
over the range, and an additional 0.3 m from each side of
the appliance, was not taken into account. Figure 6 shows
the numerical model of the case study kitchen.
In the same case study kitchen, measurements reported
by Li et al. (2012) were compared with CFD simulations.
The mean temperatures ranged from 41.5 to 54.0℃ for
measurement points taken during the cooking mode. At the
same time, the mean values of CO2 concentration ranged
from 1450 to 2145 ppm during the cooking mode. This was
mainly because the indoor environment of the case study
kitchen was highly dependent on the outdoor environment,
and without a cooled air supply system, the hood was unable
to remove the waste heat effectively.
The velocity, temperature and CO2 concentrations of the
simulated results are presented in Fig. 7. The results were
verified using actual measurements, and this was supported
Fig. 5 Schematic of six side panels
Zhao et al. / Building Simulation
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Fig. 6 Schematic diagram of the simulation kitchen
Fig. 7 Comparison between measured and simulated results in the case study kitchen: (a) velocity; (b) temperature; (c) CO2 concentration
Zhao et al. / Building Simulation
8
by the site test undertaken in another study (Li et al. 2012).
Figure 7, shows good agreement between the measured
and simulated results. However, there are some differences
between them. The deviations between the measurements
and simulations can be attributed to many factors.
An efficient kitchen hood is essential for providing a
comfortable working environment and to ensure energy
conservation. Figure 8 presents a summary of the simulated
results for the 21 hood shapes. We found that the capture
efficiency ( c
η) of different hood shapes varies greatly.
Among the 21 hood shapes, the traditional Chinese, the
American, and the European styles of cooking hoods had
higher c
η values than most of the other shapes. In addition,
the exhaust duct arrangements of the hoods, whether on the
rear or on the upper side, did not have much influence on the
hood capture efficiency. Case 5 has the highest c
η value for
these conditions. Figure 8(b) shows the average concentration
of carbon dioxide in the occupied zone. In comparison with
the corresponding capture efficiency, we found that the
variation trend of the CO2 concentration was different. The
case that had higher capture efficiency (Case 13) may not
have had a lower level of CO2 concentration. The case with
the lowest value for these conditions is Case 6.
In the previous study, we thought the small hood volume
of the traditional Chinese style cooking hood would reduce
the capture efficiency, however, the simulated results showed
that increasing the hood depth did not improve the capture
performance.
Figure 9(a) illustrates the comparison of capture
efficiency between experimental and simulated results. The
experimental values were supported by the results found
in another study (Kotani et al. 2009). Although there are
about 4%–7% differences in c
η values, CFD analysis can
reproduce the trend of the measurement results. One reason
for the small difference seems to be the limitations of using
the standard k-
model. This type of flow field is like an
impinging jet problem, so the standard k-
model has an
application limit.
Figure 9 presents the relationship between the exhaust
flow rate and the measured capture efficiency ( c
η). As the
flow rate becomes larger, c
η shows the high value as expected.
From Fig. 9, we can also see that values are higher with the
side panel than without the side panel, in almost all con-
ditions, so the side panel can improve the capture efficiency.
In addition, when the exhaust opening is in the rear of the
hood, better hood capture efficiency is achieved. The C&C
efficiency was enhanced by about 20% by maintaining the
minimum exhaust flow rate and adding a side panel. When
the exhaust flow rate was increased to 14 000 m3/h, the C&C
value added was not that clear.
Figure 10 illustrates the relationship between the side
panel shape and the simulated capture efficiency. Various
capture efficiency values are shown in the simulation. In
the case of 6000 m3/h of flow rate, capture efficiency shows
higher values in the case of rectangular side panels than
for the case of triquetrous side panels. This means that the
rectangular side panels work effectively. The highest capture
efficiency was in the case of the rectangular, 0.9 m´1.0 m,
side panel. This was also true for 8000 and 10 000 m3/h.
Increasing the height of the side panel from 0.7 to 1.1 m,
Fig. 8 Simulate results of 21 hood shapes (exhaust flow rate 8000 m3/h): (a) capture efficiency; (b) CO2 concentration in the occupied zone
Zhao et al. / Building Simulation
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Fig. 9 Relationship between exhaust flow rate and capture efficiency: (a) comparison between experiment and simulated results; (b)
without side panel; (c) side panel 1; (d) side panel 2; (e) side panel 3; (f) side panel 4; (g) side panel 5; (h) side panel 6
Zhao et al. / Building Simulation
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increased the capture efficiency of rectangular and triquetrous
side panels slightly. However, in the case of 10 000 m3/h, by
increasing the height of the side panel from 0.9 to 1.1 m,
it was possible to decrease the capture efficiency of the
rectangular and triquetrous side panels. The 0.9 m´1.0 m
rectangular side panel was the best case for these conditions.
Nevertheless, as the exhaust flow rate increases, for example
in the case of 12 000 and 14 000 m3/h, this tendency changes.
In the case of 12 000 m3/h of flow rate, the 0.9 m´1.0 m
triquetrous side panel had a better performance in enhancing
the hood capture efficiency, and this tendency was the same
at 14 000 m3/h. c
η becomes higher as the side panel is set
to a higher position. Generally, we can find the triquetrous
side panels’ performance to be better with the larger exhaust
flow rates.
5 Conclusions
High efficiency exhaust hoods with many types of hood
shapes and side panels were designed and investigated in
this study, along with different exhaust duct arrangements.
Basic site tests and CFD analysis were conducted.
Fig. 10 Relationship between side panel height and capture efficiency
Zhao et al. / Building Simulation
11
The simulated results showed that the small hood volume
of traditional Chinese style cooking hoods did not reduce
the capture efficiency ( c
η). Among the 21 hood shapes
tested, traditional Chinese style cooking hoods, American
and European style cooking hoods had higher c
η values
than most of the other cases. Thus, increasing hood volumes
did not improve capture performance.
Side panels can improve the capture efficiency, especially
at higher positions. In addition, when the exhaust opening
is in the rear of the hood, the improvement in hood capture
efficiency is greater. Generally we found that the triquetrous
side panel performance was better with larger exhaust flow
rates.
Acknowledgements
Support from the National Natural Science Foundation of
China (No. 51178374) in this study is gratefully acknowledged.
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