Study on the Influence and Optimization of the Venturi Effect on the Natural Ventilation of Buildings in the Xichang Area

Abstract

Natural ventilation is a way to reduce the energy consumption of building operations and improve the indoor living environment comfort. The venturi cap is designed with a roof, grille and wind deflector to intensify the natural ventilation of buildings. The structural parameters of the venturi cap were designed using an orthogonal design. Fluid analysis software was used for numerical simulation, and variance analysis was used to study the importance of seven influence factors: the width of the roof opening, the roof slope, the height of the wind deflector, the horizontal width of the wind deflector, the angle of the wind deflector, the angle of the grille, and the spacing of the grille slices. The results show that the most significant influencing factor is the width of the roof opening, while significant influence factors include the angle of the grille and the horizontal width of the wind deflector. Additionally, the optimum parameter combination for ventilation performance at the research level was put forward, with the proposed combination achieving a volume flow rate of 5.507 m3/s. The average temperature of the horizontal plane at a height of 1.2 m above the ground was 3.002 K lower than that without a venturi cap, which provides a reference for the optimization of indoor ventilation design in buildings in the Xichang area.

Full text

energies
Article
Study on the Influence and Optimization of the Venturi Effect
on the Natural Ventilation of Buildings in the Xichang Area
Lili Zhang *, Lei Tian , Qiong Shen, Fei Liu, Haolin Li, Zhuojun Dong, Jingyue Cheng, Haoru Liu
and Jiangjun Wan


Citation: Zhang, L.; Tian, L.; Shen,
Q.; Liu, F.; Li, H.; Dong, Z.; Cheng, J.;
Liu, H.; Wan, J. Study on the
Influence and Optimization of the
Venturi Effect on the Natural
Ventilation of Buildings in the
Xichang Area. Energies 2021,14, 5053.
https://doi.org/10.3390/en14165053
Academic Editor: Efstathios
E. Michaelides
Received: 28 June 2021
Accepted: 12 August 2021
Published: 17 August 2021
Publisher’s Note: MDPI stays neutral
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Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
College of Architectural and Urban-Rural Planning, Dujiangyan Campus, Sichuan Agricultural University,
Ya’an 611830, China; tianlei@stu.sicau.edu.cn (L.T.); swydong@sicau.edu.cn (Q.S.); 79013@sicau.edu.cn (F.L.);
2020225001@stu.sicau.edu.cn (H.L.); 2020325009@stu.sicau.edu.cn (Z.D.); chengjingyue@stu.sicau.edu.cn (J.C.);
liuhaoru@stu.sicau.edu.cn (H.L.); wanjiangjun@sicau.edu.cn (J.W.)
*Correspondence: 41414@sicau.edu.cn; Tel.: +86-18-280-215-370
Abstract:
Natural ventilation is a way to reduce the energy consumption of building operations
and improve the indoor living environment comfort. The venturi cap is designed with a roof, grille
and wind deflector to intensify the natural ventilation of buildings. The structural parameters of
the venturi cap were designed using an orthogonal design. Fluid analysis software was used for
numerical simulation, and variance analysis was used to study the importance of seven influence
factors: the width of the roof opening, the roof slope, the height of the wind deflector, the horizontal
width of the wind deflector, the angle of the wind deflector, the angle of the grille, and the spacing of
the grille slices. The results show that the most significant influencing factor is the width of the roof
opening, while significant influence factors include the angle of the grille and the horizontal width of
the wind deflector. Additionally, the optimum parameter combination for ventilation performance at
the research level was put forward, with the proposed combination achieving a volume flow rate of
5.507 m
3
/s. The average temperature of the horizontal plane at a height of 1.2 m above the ground
was 3.002 K lower than that without a venturi cap, which provides a reference for the optimization of
indoor ventilation design in buildings in the Xichang area.
Keywords:
natural ventilation; venturi effect; orthogonal design; numerical simulation; variance analysis
1. Introduction
1.1. The Necessity of Natural Ventilation
The construction industry has been identified as one of the most energy-intensive
industries, accounting for about 42% of global energy consumption [
1
]. The total energy
consumption of residential buildings accounts for 18% of the energy consumption in the
construction industry, and is growing at a rate of 1.5% each year [
2
]. Natural ventilation
offers great potential with respect to the energy efficiency of buildings. One of the main
measures employed to achieve indoor comfort while mitigating building energy consump-
tion is the strengthening of natural indoor ventilation [
3
]. The results reported in [
4
] suggest
that the amount of energy saved using other ventilation modes is not high, representing
only 0.03% of common natural ventilation. That is to say, the application of technology to
enhance the efficiency of natural ventilation in buildings without an external environment
is a way of saving energy in buildings [
5
]. In the construction industry, building ventilation
is one of the most important parameters to be considered in order to maintain a comfortable
indoor environment and to provide better indoor air quality [
6
]. According to research
reported by Canada’s Environmental Defense Organization, 68% of human diseases are
caused by indoor air pollution [
7
]. The best way to improve indoor air quality is to allow
enough fresh air into the building and ensure that there is a reasonable air distribution
inside the building [
8
]. In addition, the outbreaks of sick building syndrome (SBS) in
developed countries in the 1970s and 1980s, severe acute respiratory syndrome coronavirus
Energies 2021,14, 5053. https://doi.org/10.3390/en14165053 https://www.mdpi.com/journal/energies

Energies 2021,14, 5053 2 of 16
(SARS) in Asia in 2003, and Corona Virus Disease 2019 (COVID-19) that has been sweeping
the world since late 2019 have led people to think deeply about the safety and health of
their offices and living spaces, with suitable temperature and humidity being achieved in
enclosed spaces by mechanical means in modern architecture.
The total wind energy resource reserves of China at the height of 10 m above the
ground are about 4.35 billion KW, which ranks first in the world [
9
]. Considering the
abundance of wind energy resources, land use types, and landforms, and the variability
of wind energy, the regions with the most abundant sources of wind energy are the Tibet
Plateau, the Hexi Corridor, and Inner Mongolia [
10
]. Xichang is located on the Anning
River Plain of the Western Sichuan Plateau, which has the best wind resources in Sichuan
Province. The buildings in Xichang pay special attention to the ventilation of the building,
while little attention is paid to the performance of thermal insulation, which has little
impact on the residents’ living situation [
11
]. Using a venturi cap to optimize ventilation
reduces energy consumption and improves the ventilation conditions in the Xichang area,
meeting the needs of residents on an environmentally sustainable basis.
1.2. Venturi Cap
The venturi effect is an application of natural ventilation that can be employed in
both horizontal and vertical directions. Vertical applications (Figure 1) are implemented
in the form of a venturi cap. Most local buildings in Xichang have sloped roofs, which
also meet the structural requirements of venturi caps. As shown in Figure 1, the main
structure of the venturi cap comprises a sloping roof, a wind deflector, and a grille. The
sloping roof guides the airflow separated at the windward facade to the roof ridge, making
it accelerate, forming negative pressure at the openings, where the negative pressure causes
the indoor air to be sucked out. The addition of a wind deflector on the upper side of the
roof ridge can form a complete “venturi tube” structure, which can collect more incoming
outdoor air and reduce the cross-section, enhancing the acceleration effect and increasing
the adsorption capacity. (Figure 2) The grille blocks out direct sunlight, reducing heat
radiation in the summer and preventing small animals from falling through the openings.
The grille can also be closed if necessary. While protecting traditional culture, making full
use of renewable resources to create comfortable indoor environments is an indispensable
part of the protection and renewal of residential buildings. It is also one of the crucial
solutions for building energy conservation and emission reduction.
Energies 2021, 14, x FOR PEER REVIEW 2 of 17
air quality is to allow enough fresh air into the building and ensure that there is a reason-
able air distribution inside the building [8]. In addition, the outbreaks of sick building
syndrome (SBS) in developed countries in the 1970s and 1980s, severe acute respiratory
syndrome coronavirus (SARS) in Asia in 2003, and Corona Virus Disease 2019 (COVID-
19) that has been sweeping the world since late 2019 have led people to think deeply about
the safety and health of their offices and living spaces, with suitable temperature and hu-
midity being achieved in enclosed spaces by mechanical means in modern architecture.
The total wind energy resource reserves of China at the height of 10 m above the
ground are about 4.35 billion KW, which ranks first in the world [9]. Considering the
abundance of wind energy resources, land use types, and landforms, and the variability
of wind energy, the regions with the most abundant sources of wind energy are the Tibet
Plateau, the Hexi Corridor, and Inner Mongolia [10]. Xichang is located on the Anning
River Plain of the Western Sichuan Plateau, which has the best wind resources in Sichuan
Province. The buildings in Xichang pay special attention to the ventilation of the building,
while little attention is paid to the performance of thermal insulation, which has little im-
pact on the residents’ living situation [11]. Using a venturi cap to optimize ventilation
reduces energy consumption and improves the ventilation conditions in the Xichang area,
meeting the needs of residents on an environmentally sustainable basis.
1.2. Venturi Cap
The venturi effect is an application of natural ventilation that can be employed in
both horizontal and vertical directions. Vertical applications (Figure 1) are implemented
in the form of a venturi cap. Most local buildings in Xichang have sloped roofs, which also
meet the structural requirements of venturi caps. As shown in Figure 1, the main structure
of the venturi cap comprises a sloping roof, a wind deflector, and a grille. The sloping roof
guides the airflow separated at the windward facade to the roof ridge, making it acceler-
ate, forming negative pressure at the openings, where the negative pressure causes the
indoor air to be sucked out. The addition of a wind deflector on the upper side of the roof
ridge can form a complete “venturi tube” structure, which can collect more incoming out-
door air and reduce the cross-section, enhancing the acceleration effect and increasing the
adsorption capacity. (Figure 2) The grille blocks out direct sunlight, reducing heat radia-
tion in the summer and preventing small animals from falling through the openings. The
grille can also be closed if necessary. While protecting traditional culture, making full use
of renewable resources to create comfortable indoor environments is an indispensable
part of the protection and renewal of residential buildings. It is also one of the crucial
solutions for building energy conservation and emission reduction.
Figure 1. Schematic diagram of a venturi cap.
Figure 1. Schematic diagram of a venturi cap.

Energies 2021,14, 5053 3 of 16
Energies 2021, 14, x FOR PEER REVIEW 3 of 17
Figure 2. Acceleration due to the venturi effect, simulated by computational fluid dynamics
(CFD).
1.3. Research into Application of the Venturi Effect
The most representative application of the venturi effect is the venturi tube (Figure
3), which has been widely using in various fields due to its simple structure and low cost
[12]. Li et al. [13] studied the influence of the geometrical parameters of the venturi tube
on the cavitation phenomenon and microbubble generation. Shi et al. [14] conducted ex-
perimental and numerical studies on the cavitation phenomena in venturi tubes with dif-
ferent geometric shapes. Bimestre et al. [15], Zhu et al. [16], and Long et al. [17] explored
the cavitation characteristics of venturi tubes. The application of the venturi effect goes
far beyond this. Gonzalez-Perez et al. [18] enhanced the absorption of steam waste in the
absence of a mechanical compressor by using the venturi effect. Perez et al. [19–21] studied
the important role played by the venturi effect in the production of O2 from H2O2. Ji et al.
[12], Xu et al. [22], and Yu et al. [23] showed that the venturi effect could be applied to the
nozzle to improve its performance.
Figure 3. Schematic diagram of a venturi tube.
The venturi effect also plays a positive role in agricultural production. Lei et al. [24]
studied the movement of rapeseed and wheat seeds in the venturi seed feeding device
Figure 2. Acceleration due to the venturi effect, simulated by computational fluid dynamics (CFD).
1.3. Research into Application of the Venturi Effect
The most representative application of the venturi effect is the venturi tube (
Figure 3
),
which has been widely using in various fields due to its simple structure and low cost [
12
].
Li et al. [
13
] studied the influence of the geometrical parameters of the venturi tube
on the cavitation phenomenon and microbubble generation. Shi et al. [
14
] conducted
experimental and numerical studies on the cavitation phenomena in venturi tubes with
different geometric shapes. Bimestre et al. [
15
], Zhu et al. [
16
], and Long et al. [
17
] explored
the cavitation characteristics of venturi tubes. The application of the venturi effect goes
far beyond this. Gonzalez-Perez et al. [
18
] enhanced the absorption of steam waste in
the absence of a mechanical compressor by using the venturi effect. Perez et al. [
19
–
21
]
studied the important role played by the venturi effect in the production of O
2
from H
2
O
2
.
Ji et al. [
12
], Xu et al. [
22
], and Yu et al. [
23
] showed that the venturi effect could be applied
to the nozzle to improve its performance.
Energies 2021, 14, x FOR PEER REVIEW 3 of 17
Figure 2. Acceleration due to the venturi effect, simulated by computational fluid dynamics
(CFD).
1.3. Research into Application of the Venturi Effect
The most representative application of the venturi effect is the venturi tube (Figure
3), which has been widely using in various fields due to its simple structure and low cost
[12]. Li et al. [13] studied the influence of the geometrical parameters of the venturi tube
on the cavitation phenomenon and microbubble generation. Shi et al. [14] conducted ex-
perimental and numerical studies on the cavitation phenomena in venturi tubes with dif-
ferent geometric shapes. Bimestre et al. [15], Zhu et al. [16], and Long et al. [17] explored
the cavitation characteristics of venturi tubes. The application of the venturi effect goes
far beyond this. Gonzalez-Perez et al. [18] enhanced the absorption of steam waste in the
absence of a mechanical compressor by using the venturi effect. Perez et al. [19–21] studied
the important role played by the venturi effect in the production of O2 from H2O2. Ji et al.
[12], Xu et al. [22], and Yu et al. [23] showed that the venturi effect could be applied to the
nozzle to improve its performance.
Figure 3. Schematic diagram of a venturi tube.
The venturi effect also plays a positive role in agricultural production. Lei et al. [24]
studied the movement of rapeseed and wheat seeds in the venturi seed feeding device
Figure 3. Schematic diagram of a venturi tube.

Energies 2021,14, 5053 4 of 16
The venturi effect also plays a positive role in agricultural production. Lei et al. [
24
]
studied the movement of rapeseed and wheat seeds in the venturi seed feeding device and
provided suggestions for improving the operating performance of seed feeding devices.
Moreover, Quiroz-Perez et al. [
25
] used CFD simulation to find that the venturi device
was able to generate a gas–liquid flow, thus increasing the gas production in some types
of gas wells. Pan et al. [
26
] optimized the outlet of a smoke exhaust fan based on the
venturi effect using an orthogonal design, a comprehensive scoring method, and the range
analysis method, improving its smoke exhaust performance. Li [
27
] used the venturi
effect to strengthen the natural smoke exhaust. On the basis of theoretical analysis, CFD
numerical simulation, and wind tunnel experiments, a natural smoke exhaust device under
the venturi effect was designed. Oliveira, M.A.d. et al. [
28
] studied the influence of the
venturi effect on the control and suppression of vortex shedding in a slightly rough cylinder
using the discrete vortex method. Shishodia et al. [
29
] applied the venturi effect in helmet
design to improve the local airflow velocity in the gap between the head and the helmet,
increasing the thermal comfort of riders.
With decreasing cross-section area, the flow velocity in building passages increases,
as has been widely recognized and disseminated [
30
]. For integrated buildings with
narrow gaps, building installations with divergent channels at intersecting angles can
lead to the formation of the venturi effect [31]. However, Blocken et al. [32] put forward a
different view, doubting the feasibility of the venturi effect in urban wind environments,
and suggesting that the wind-blocking effect leads to increases in near-surface wind speed.
Li et al. [
33
] and Allegrini et al. [
34
] provided support for the views proposed by Blocken
et al. [
32
] on the basis of experiments. Chong. et al. [
35
] and Wang et al. [
36
] studied a
hybrid solar–wind–rain eco-roof system for buildings. The system enhanced the wind
speed before the interaction between the wind and the wind turbine located between the
roof, strengthening the effect of the wind turbine through a rational use of the venturi effect.
Ameer et al. [
37
], inspired by the venturi effect, designed a narrow roof that could increase
the wind speed when the wind passed between two obstacles on the roof. Blocken et al.
and Hooff et al. [
38
–
40
] studied the effect of venturi roofs on ventilation and analyzed the
effect of the venturi and wind-blocking effects on venturi roofs. Then, they discussed the
relationship between the width of the venturi roof and roof performance. Kumar et al. [
41
]
studied the use of the venturi effect to intensify the air pressure in the vertical void to
enhance the lateral ventilation on the leeward side of a double-load apartment building.
Li et al.
[
42
] studied the venturi effect on the effect of transverse entrains on pollutant
diffusion in a street canyon. Some studies have been devoted to finding the best window
opening to effectively regulate indoor airflow intensity by using the venturi effect [
43
–
46
].
Muhsin et al. [
47
] showed that the natural ventilation performance of multi-story residential
units could be enhanced by implementing an appropriate void structure. Wang et al. [
48
]
aimed to build a relationship between wind energy potential and the configuration of
two vertical buildings by studying the wind accumulation phenomenon of the venturi
effect in the building environment. In addition, the venturi effect was used in the design
of the escape passage in order to adsorb the airflow and generate stable air movement
in the room. This effect makes it possible to generate airflow in indoor areas such as
basements [
49
]. Paepe et al. [
50
] optimized the ventilation of a cowshed by enhancing
the venturi effect by creating an opening along the ridge and adding a wind deflector in
the cowshed. Therefore, it can be seen that the venturi effect has extensive application
prospects in regions with abundant sources of wind energy, and the development of wind
energy in the built environment will be a crucial topic for sustainable cities in the future.
1.4. Summary
To date, scholars have proposed many strategies and measures for effectively applying
the venturi effect in order to improve the convenience of our lifestyles and production
on the basis of studies of applications of the venturi effect. However, by reviewing the
research into applications of the effect, it can easily be found that that:

Energies 2021,14, 5053 5 of 16
Many scholars have performed numerous studies analyzing applications of the venturi
effect applications; however, there is no comprehensive study evaluating the degree to
which structural parameters affect the ventilation performance of the venturi effect.
Therefore, in line with the above summary, in this paper, the application of the venturi
effect in building ventilation and the influence of various parameters on ventilation effect
will be studied, and a venturi cap structure suitable for use in the Xichang area will
be proposed.
2. Methodology
2.1. Physical Model
In the early days, the Yi people in Liangshan Prefecture lived together with poultry.
Even now, this habit of habitation is still being preserved. Therefore, buildings have a
high ventilation demand. The house structure, comprising raw soil and produced through
wooden structure trusses, is a common building type for the middle class among the Yi
in Liangshan [
51
]. The building is made of columns, beams, and wooden structure roof
trusses as the frame of the house, and the components are connected. The wall is made of a
wall compacted with raw soil, with wall thickness reaching up to 350 mm [
52
]. While in-
vestigating the residential forms in the town of Huanglianguan in Xichang, scholars found
that buildings with a depth of 3500 mm–4200 mm and a face width of
5500 mm–6400 mm
account for the largest proportion in the local area [
53
]. Therefore, as shown in
Figure 4
,
this study selected buildings with sizes of 6 m
×
4 m for the study. The thickness of the
building walls was 350 mm, while the height of the cornice was 3000 mm, and the roof was
covered in wood with a thickness of 50 mm and grass much with a thickness of 30 mm. As
is shown in Table 1, the building height was related to the sloping roof and the width of
the roof opening. The venturi cap was arranged along the ridge of roof. The thickness of
the grille was 10 mm. The width of the grille was equal to the width of the gap between
the grilles, allowing the grille to close easily. There was also a door on the other wall of the
room, which was 1200 mm wide and 2000 mm high, to provide airflow from the outside.
Energies 2021, 14, x FOR PEER REVIEW 5 of 17
Many scholars have performed numerous studies analyzing applications of the ven-
turi effect applications; however, there is no comprehensive study evaluating the degree
to which structural parameters affect the ventilation performance of the venturi effect.
Therefore, in line with the above summary, in this paper, the application of the ven-
turi effect in building ventilation and the influence of various parameters on ventilation
effect will be studied, and a venturi cap structure suitable for use in the Xichang area will
be proposed.
2. Methodology
2.1. Physical Model
In the early days, the Yi people in Liangshan Prefecture lived together with poultry.
Even now, this habit of habitation is still being preserved. Therefore, buildings have a high
ventilation demand. The house structure, comprising raw soil and produced through
wooden structure trusses, is a common building type for the middle class among the Yi
in Liangshan [51]. The building is made of columns, beams, and wooden structure roof
trusses as the frame of the house, and the components are connected. The wall is made of
a wall compacted with raw soil, with wall thickness reaching up to 350 mm [52]. While
investigating the residential forms in the town of Huanglianguan in Xichang, scholars
found that buildings with a depth of 3500 mm–4200 mm and a face width of 5500 mm–
6400 mm account for the largest proportion in the local area [53]. Therefore, as shown in
Figure 4, this study selected buildings with sizes of 6 m × 4 m for the study. The thickness
of the building walls was 350 mm, while the height of the cornice was 3000 mm, and the
roof was covered in wood with a thickness of 50 mm and grass much with a thickness of
30 mm. As is shown in Table 1, the building height was related to the sloping roof and the
width of the roof opening. The venturi cap was arranged along the ridge of roof. The
thickness of the grille was 10 mm. The width of the grille was equal to the width of the
gap between the grilles, allowing the grille to close easily. There was also a door on the
other wall of the room, which was 1200 mm wide and 2000 mm high, to provide airflow
from the outside.
(a) (b)
Figure 4. Numerical model constructed by computational fluid dynamics (CFD). (a) Complete model; (b) local model.
2.2. Numerical Scheme
The orthogonal experimental design is a method used to study multiple factors at
multiple levels. It is an efficient, rapid, and economical experimental design method that
selects representative points from comprehensive tests according to the principle of or-
thogonality. This paper studies the effects of seven factors: (A) width of roof opening; (B)
roof slope; (C) height of wind deflector; (D) horizontal width of wind deflector; (E) angle
of wind deflector; (F) angle of grille; (G) spacing of grille slices. As shown in Table 1, each
Figure 4. Numerical model constructed by computational fluid dynamics (CFD). (a) Complete model; (b) local model.

Energies 2021,14, 5053 6 of 16
Table 1. Orthogonal design arrangements and results.
Scene Width of Roof
Opening (mm) Roof Slope (◦)Height of Wind
Deflector (mm)
Horizontal
Width of Wind
Deflector (mm)
Angle of Wind
Deflector (◦)
Angle of Grille
(◦)
Spacing of Grille
Slices (mm)
Building
Height (mm)
Volume Flow
Rate (m3/s)
N1 400(A1) 45(B3) 600(C3) 600(D3) 0(E1) 75(F3) 20(G1) 3843.430 3.399
N2 800(A3) 30(B2) 600(C3) 200(D1) 0(E1) 60(F2) 80(G4) 3415.690 4.563
N3 600(A2) 60(B4) 600(C3) 400(D2) 15(E2) 45(F1) 20(G1) 4392.245 3.553
N4 600(A2) 15(B1) 400(C2) 400(D2) 0(E1) 60(F2) 40(G2) 3372.690 4.576
N5 600(A2) 45(B3) 800(C4) 600(D3) 30(E3) 45(F1) 80(G4) 3793.430 4.015
N6 800(A3) 15(B1) 800(C4) 800(D4) 45(E4) 60(F2) 20(G1) 3345.900 4.297
N7 800(A3) 60(B4) 200(C1) 800(D4) 30(E3) 45(F1) 40(G2) 4305.640 3.447
N8 1000(A4) 15(B1) 600(C3) 800(D4) 15(E2) 90(F4) 80(G4) 3319.100 4.553
N9 600(A2) 45(B3) 800(C4) 800(D4) 0(E1) 90(F4) 40(G2) 3793.430 4.133
N10 1000(A4) 45(B3) 200(C1) 400(D2) 15(E2) 60(F2) 80(G4) 3693.430 4.458
N11 1000(A4) 60(B4) 400(C2) 600(D3) 30(E3) 60(F2) 20(G1) 4219.040 4.829
N12 400(A1) 15(B1) 200(C1) 200(D1) 0(E1) 45(F1) 20(G1) 3399.490 2.890
N13 1000(A4) 30(B2) 800(C4) 400(D2) 0(E1) 45(F1) 60(G3) 3386.825 4.651
N14 800(A3) 60(B4) 200(C1) 600(D3) 0(E1) 90(F4) 80(G4) 4305.640 4.105
N15 400(A1) 15(B1) 200(C1) 400(D2) 30(E3) 90(F4) 60(G3) 3399.490 3.887
N16 1000(A4) 45(B3) 200(C1) 200(D1) 45(E4) 75(F3) 40(G2) 3693.430 5.002
N17 400(A1) 60(B4) 800(C4) 200(D1) 15(E2) 60(F2) 40(G2) 4478.845 4.083
N18 400(A1) 60(B4) 800(C4) 400(D2) 45(E4) 75(F3) 80(G4) 4478.845 4.502
N19 600(A2) 60(B4) 600(C3) 200(D1) 45(E4) 90(F4) 60(G3) 4392.245 4.816
N20 1000(A4) 15(B1) 600(C3) 600(D3) 45(E4) 45(F1) 40(G2) 3319.100 4.804
N21 400(A1) 30(B2) 400(C2) 600(D3) 15(E2) 90(F4) 40(G2) 3473.425 3.888
N22 600(A2) 30(B2) 200(C1) 800(D4) 15(E2) 75(F3) 20(G1) 3444.560 4.103
N23 800(A3) 45(B3) 400(C2) 200(D1) 15(E2) 45(F1) 60(G3) 3743.430 4.628
N24 1000(A4) 30(B2) 800(C4) 200(D1) 30(E3) 90(F4) 20(G1) 3386.825 4.695
N25 800(A3) 30(B2) 600(C3) 400(D2) 30(E3) 75(F3) 40(G2) 3415.690 4.619
N26 600(A2) 15(B1) 400(C2) 200(D1) 30(E3) 75(F3) 80(G4) 3372.690 4.610
N27 800(A3) 15(B1) 800(C4) 600(D3) 15(E2) 75(F3) 60(G3) 3345.900 4.573
N28 400(A1) 45(B3) 600(C3) 800(D4) 30(E3) 60(F2) 60(G3) 3843.430 3.233
N29 600(A2) 30(B2) 200(C1) 600(D3) 45(E4) 60(F2) 60(G3) 3444.560 3.701
N30 1000(A4) 60(B4) 400(C2) 800(D4) 0(E1) 75(F3) 60(G3) 4219.040 4.431
N31 800(A3) 45(B3) 400(C2) 400(D2) 45(E4) 90(F4) 20(G1) 3743.430 4.369
N32 400(A1) 30(B2) 400(C2) 800(D4) 45(E4) 45(F1) 80(G4) 3473.425 2.370

Energies 2021,14, 5053 7 of 16
2.2. Numerical Scheme
The orthogonal experimental design is a method used to study multiple factors at
multiple levels. It is an efficient, rapid, and economical experimental design method
that selects representative points from comprehensive tests according to the principle of
orthogonality. This paper studies the effects of seven factors: (A) width of roof opening;
(B) roof slope; (C) height of wind deflector; (D) horizontal width of wind deflector; (E)
angle of wind deflector; (F) angle of grille; (G) spacing of grille slices. As shown in
Table 1
,
each factor has four different levels. Because the full factor design required 4
7
= 16,384
experiments, the orthogonal experimental design was adopted to reduce the number of
experiments and improve the experimental efficiency. Table 1shows the results of the
orthogonal experimental design using an IBM SPSS 25.0, which produced 32 simulation
scenarios. To better show the changes in these parameters, the model was decomposed
according to its structure. Figure 5shows the changes in the roof, grille, and wind deflector.
Energies 2021, 14, x FOR PEER REVIEW 8 of 17
Figure 5. Changes in various structures.
2.3. Numerical Simulation
2.3.1. Physical Properties of Building Materials and Boundary Conditions
Table 2 summarizes the physical properties of the building materials, and these ma-
terials were used to simulate the heat conduction in the structure. The grille of the venturi
cap is made of wood, while the wind deflector is made from aluminum alloy, the indoor
floor is concrete, the outdoor floor is earth, and the wall is rammed earth. All of the nec-
essary thermophysical properties of the building materials and air are assumed to be con-
stant, except for the air density, which is considered to be an ideal gas. The size of the air
domain outside the model is 50 m × 36 m × 30 m. The inlet boundary condition of the
model is velocity-inlet. The outlet is a pressure outlet, and the remaining surfaces are set
to be symmetrical. The door and grille are set to the interior. The optimization of natural
indoor ventilation in Xichang in summer is the main aspect under consideration. There-
fore, the model adopts the predominant wind direction in Xichang during summer, and
the predominant wind direction in Xichang is north–south [11]. The meteorological data
used for the weather energy of Xichang in the numerical simulation were obtained from
Chinese Standard Weather Data (CSWD) files, which were downloaded from the website
[54] and are suitable for China [55]. In the numerical simulation, the meteorological data
for summer days in the Xichang area were selected, and therefore the outside temperature
was set at 300 K and the wind speed was 3.3 m/s.
Table 2. Material properties of the venturi cap.
Material Properties Density (kg/m3) Conductivity (W/(m × k)) Specific Heat (J/(kg × k))
Adobe 1800 0.93 1010
Wood 500 0.14 2510
Al 2719 202.4 871
Concrete 2300 1.51 920
2.3.2. Grid Division
To ensure the independence of the mesh, four grid sizes were used for the experi-
ments: 1,347,614 (1#), 1,919,598 (2#), 2,269,404 (3#) and 2,651,469 (4#). Figure 6 shows the
experimental convergence results under four different meshing conditions. The difference
Figure 5. Changes in various structures.
2.3. Numerical Simulation
2.3.1. Physical Properties of Building Materials and Boundary Conditions
Table 2summarizes the physical properties of the building materials, and these
materials were used to simulate the heat conduction in the structure. The grille of the
venturi cap is made of wood, while the wind deflector is made from aluminum alloy, the
indoor floor is concrete, the outdoor floor is earth, and the wall is rammed earth. All of the
necessary thermophysical properties of the building materials and air are assumed to be
constant, except for the air density, which is considered to be an ideal gas. The size of the
air domain outside the model is 50 m
×
36 m
×
30 m. The inlet boundary condition of the
model is velocity-inlet. The outlet is a pressure outlet, and the remaining surfaces are set
to be symmetrical. The door and grille are set to the interior. The optimization of natural
indoor ventilation in Xichang in summer is the main aspect under consideration. Therefore,
the model adopts the predominant wind direction in Xichang during summer, and the
predominant wind direction in Xichang is north–south [
11
]. The meteorological data used
for the weather energy of Xichang in the numerical simulation were obtained from Chinese
Standard Weather Data (CSWD) files, which were downloaded from the website [
54
] and
are suitable for China [
55
]. In the numerical simulation, the meteorological data for summer
days in the Xichang area were selected, and therefore the outside temperature was set at
300 K and the wind speed was 3.3 m/s.

Energies 2021,14, 5053 8 of 16
Table 2. Material properties of the venturi cap.
Material Properties Density (kg/m3)Conductivity (W/(m ×k)) Specific Heat (J/(kg ×k))
Adobe 1800 0.93 1010
Wood 500 0.14 2510
Al 2719 202.4 871
Concrete 2300 1.51 920
2.3.2. Grid Division
To ensure the independence of the mesh, four grid sizes were used for the experiments:
1,347,614 (1#), 1,919,598 (2#), 2,269,404 (3#) and 2,651,469 (4#). Figure 6shows the exper-
imental convergence results under four different meshing conditions. The difference in
the volume flow rate between 1# and 2# was 40.833%, that between 2# and 3# was 1.650%,
and that between 2# and 4# was 0.259%. Finally, the partition method of 1,919,598 (2#)
was selected. In addition, as shown in Figure 7, the poly-hex core grid type was adopted
to mesh the model. The global minimum surface mesh was 48.828 mm, and the global
maximum surface mesh was 1000 mm. The local surface mesh of the door, indoor floor,
wall, and roof was set as 80 mm, and the local surface mesh of the grilles and wind deflector
was set as 20 mm. The minimum mesh volume was 20 mm, the maximum mesh volume
was 640 mm, and three layers of the boundary were set to achieve a reasonable transition
of the mesh.
Energies 2021, 14, x FOR PEER REVIEW 9 of 17
in the volume flow rate between 1# and 2# was 40.833%, that between 2# and 3# was
1.650%, and that between 2# and 4# was 0.259%. Finally, the partition method of 1,919,598
(2#) was selected. In addition, as shown in Figure 7, the poly-hex core grid type was
adopted to mesh the model. The global minimum surface mesh was 48.828 mm, and the
global maximum surface mesh was 1000 mm. The local surface mesh of the door, indoor
floor, wall, and roof was set as 80 mm, and the local surface mesh of the grilles and wind
deflector was set as 20 mm. The minimum mesh volume was 20 mm, the maximum mesh
volume was 640 mm, and three layers of the boundary were set to achieve a reasonable
transition of the mesh.
Figure 6. Volumetric flow rate under various grid sizes.
(a) (b)
Figure 7. Computational fluid dynamics (CFD) meshing (2#). (a) Volume mesh; (b) surface mesh.
2.3.3. Computational Fluid Dynamics (CFD) Theory
Numerical simulation was performed using ANSYS Fluent 2020 R2 using a finite-
volume hydrodynamics solver. The simulation follows the laws of conservation of mass,
momentum, and energy.
The mass conservation equation of the continuity equation is expressed as follows:
∂ρ
∂t +ΔρV
󰇍
󰇍

=0 (1)
Figure 6. Volumetric flow rate under various grid sizes.

Energies 2021,14, 5053 9 of 16
Energies 2021, 14, x FOR PEER REVIEW 9 of 17
in the volume flow rate between 1# and 2# was 40.833%, that between 2# and 3# was
1.650%, and that between 2# and 4# was 0.259%. Finally, the partition method of 1,919,598
(2#) was selected. In addition, as shown in Figure 7, the poly-hex core grid type was
adopted to mesh the model. The global minimum surface mesh was 48.828 mm, and the
global maximum surface mesh was 1000 mm. The local surface mesh of the door, indoor
floor, wall, and roof was set as 80 mm, and the local surface mesh of the grilles and wind
deflector was set as 20 mm. The minimum mesh volume was 20 mm, the maximum mesh
volume was 640 mm, and three layers of the boundary were set to achieve a reasonable
transition of the mesh.
Figure 6. Volumetric flow rate under various grid sizes.
(a) (b)
Figure 7. Computational fluid dynamics (CFD) meshing (2#). (a) Volume mesh; (b) surface mesh.
2.3.3. Computational Fluid Dynamics (CFD) Theory
Numerical simulation was performed using ANSYS Fluent 2020 R2 using a finite-
volume hydrodynamics solver. The simulation follows the laws of conservation of mass,
momentum, and energy.
The mass conservation equation of the continuity equation is expressed as follows:
∂ρ
∂t +ΔρV
󰇍
󰇍

=0 (1)
Figure 7. Computational fluid dynamics (CFD) meshing (2#). (a) Volume mesh; (b) surface mesh.
2.3.3. Computational Fluid Dynamics (CFD) Theory
Numerical simulation was performed using ANSYS Fluent 2020 R2 using a finite-
volume hydrodynamics solver. The simulation follows the laws of conservation of mass,
momentum, and energy.
The mass conservation equation of the continuity equation is expressed as follows:
∂ρ
∂t+∆(ρ
→
V) = 0 (1)
where
ρ
is the fluid density,
→
V
is the velocity vector, and
∆(ρ
→
V)
is the velocity divergence.
The momentum equation of viscous fluid is a mathematical expression of the law of
conservation of momentum, which is expressed as follows:
∂
∂t(ρ
→
vi) + ∆(ρ
→
v→
vi) = ∆Pi+gi−fi(2)
where
→
vi
is the velocity component in the direction of
i
;
Pi
is the surface force vector, includ-
ing static pressure and fluid viscous stress.
gi
is the volume force acting on the direction of
unit volume flow i; fiis the resistance acting in the direction of unit volume flow.
The energy conservation equation is expressed as follows:
∂
∂t(ρE)+∆→
v(ρE+p)=∆keff∆T−Σhi
→
ji+ (τeff ×
→
v) + Sh(3)
where
keff
is the effective thermal conductivity (k + k
f
) with k
f
being the thermal conduc-
tivity caused by turbulence, and
→
ji
is the diffusion flux of component
i
. The first term on
the right-hand side of the equation represents the energy transfer due to heat conduction.
The second term represents component diffusion, and the third term represents viscous
dissipation.
Sh
contains the heat of the chemical reaction and any other definable volume
heat source.
In Fluent, the solar radiation model was adopted, and solar ray tracing was activated.
Then, parameters such as latitude and longitude were set so that the computer could
automatically calculate solar radiation intensity. The wall thermal boundary was Heat Flux,
and the calculation formula for this was as follows:
Tw =(q−qrad)∆n
kS
+Ts (4)

Energies 2021,14, 5053 10 of 16
where
kS
is the heat conduction coefficient of a solid;
∆n
is the distance from the wall
surface to the center of the unit of the first layer;
Ts
is the temperature of the solid wall
surface; q is the input heat flux; and qrad is the radiant heat flux.
In the numerical simulation, the realizable K-
ε
turbulence model was selected. The
K-
ε
turbulence model is the most commonly used two-equation turbulence model [
56
]. The
realizable K-
ε
turbulence model is appropriate for complex shear flows involving rapid
strain, slight rotation, vortex, and local transition flow. Therefore, the model is suitable for
the study of indoor environments.
3. Results and Discussion
3.1. Analysis of Variance
Thirty-two scenarios were numerically simulated, and the volume flow of the venturi
cap device is shown in Table 1. Range analysis and analysis of variance (ANOVA) are
commonly used to analyze the experimental results of orthogonal design [
56
]. ANOVA
was chosen for this study, and the variance analysis table of the volume flow rate is given
(see Table 3). Based on the ANOVA performed on the results of the numerical simulation,
we obtained the optimal level for each factor. In addition, on the basis of the p-value, the
influencing factors were ranked. If a factor has a p-value less than or equal to 0.01, then
there is 99% or so probability that the factor has a highly significant impact on overall
performance. If the p-value is between 0.01 and 0.05, the probability drops, and the factor
can be regarded as having a significant impact on overall performance. If the p-value is
greater than 0.05, the effect of this factor is not significant.
Table 3. Analysis of variance (ANOVA) table for volume flow rate.
Factor pSignificance
Width of roof opening 0.001 Highly significant
Roof slope 0.737 Not significant
Height of wind deflector 0.224 Not significant
Horizontal width of wind deflector 0.043 Significant
Angle of wind deflector 0.86 Not significant
Angle of grille 0.037 Significant
Spacing of the grille slices 0.444 Not significant
On the basis of the analysis of the simulation results of the venturi cap with different
structural parameters, it can be observed that the width of the roof opening has a highly
significant impact on the volume flow rate, followed by the angle of the grille, the horizontal
width of the wind deflector, the wind deflector height, the spacing of the grille slices, the
roof slope, and the angle of the wind deflector (see Tables 1and 3). The specific order
of influence is as follows: width of roof opening > angle of grille > horizontal width of
wind deflector > height of wind deflector > spacing of grille slices > roof slope > angle of
wind deflector.
In the analysis of the orthogonal experiment results, the level of each factor can be
regarded as good if it corresponds to a larger volume of flow rate. When the width of
the roof opening, angle of the grille, horizontal width of wind deflector, height of wind
deflector, spacing of grille slices, roof slope, and angle of wind deflector were assigned
values of 1000 mm (A
4
), 15
◦
(B
1
), 800 mm (C
4
), 200 mm (D
1
), 45
◦
(E
4
), 75
◦
(F
3
), and 40 mm
(G
2
), respectively, this scenario was named N33 and the volume flow rate of the venturi
cap was 5.220 m
3
/s. As seen in Figure 8, N33 provided the maximum volume flow rate
for the indoor environment and was therefore regarded as the optimum choice among
these 33 scenarios. The velocity cloud diagram is shown in Figure 9. At the same time,
in the same scenario, without the venturi cap, the average temperature of the horizontal
plane at a height of 1.2 m above the ground was 308.836 K, while when the venturi cap was
turned on, the average temperature of the plane was 305.997 K, representing a reduction

Energies 2021,14, 5053 11 of 16
by
2.839 K
. These results show that the venturi cap plays a definite role in improving the
ventilation conditions.
Energies 2021, 14, x FOR PEER REVIEW 11 of 17
slices, the roof slope, and the angle of the wind deflector (see Tables 1 and 3). The specific
order of influence is as follows: width of roof opening > angle of grille > horizontal width
of wind deflector > height of wind deflector > spacing of grille slices > roof slope > angle
of wind deflector.
Table 3. Analysis of variance (ANOVA) table for volume flow rate.
Factor p Significance
Width of roof opening 0.001 Highly significant
Roof slope 0.737 Not significant
Height of wind deflector 0.224 Not significant
Horizontal width of wind deflector 0.043 Significant
Angle of wind deflector 0.86 Not significant
Angle of grille 0.037 Significant
Spacing of the grille slices 0.444 Not significant
In the analysis of the orthogonal experiment results, the level of each factor can be
regarded as good if it corresponds to a larger volume of flow rate. When the width of the
roof opening, angle of the grille, horizontal width of wind deflector, height of wind de-
flector, spacing of grille slices, roof slope, and angle of wind deflector were assigned val-
ues of 1000 mm (A4), 15° (B1), 800 mm (C4), 200 mm (D1), 45° (E4), 75° (F3), and 40 mm (G2),
respectively, this scenario was named N33 and the volume flow rate of the venturi cap
was 5.220 m3/s. As seen in Figure 8, N33 provided the maximum volume flow rate for the
indoor environment and was therefore regarded as the optimum choice among these 33
scenarios. The velocity cloud diagram is shown in Figure 9. At the same time, in the same
scenario, without the venturi cap, the average temperature of the horizontal plane at a
height of 1.2 m above the ground was 308.836 K, while when the venturi cap was turned
on, the average temperature of the plane was 305.997 K, representing a reduction by 2.839
K. These results show that the venturi cap plays a definite role in improving the ventila-
tion conditions.
N1
N2
N3
N4
N5
N6
N7
N8
N9
N10
N11
N12
N13
N14
N15
N16
N17
N18
N19
N20
N21
N22
N23
N24
N25
N26
N27
N28
N29
N30
N31
N32
N33
304.0
304.5
305.0
305.5
306.0
306.5
Temperature Volume flow rate
Temperature (K)
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Volume flow rate (m3/s)
Figure 8. Volumetric flow and average temperature of a horizontal plane at a height of 1.2 m above
the ground in 33 scenarios.
Figure 8.
Volumetric flow and average temperature of a horizontal plane at a height of 1.2 m above the ground in
33 scenarios.
Energies 2021, 14, x FOR PEER REVIEW 12 of 17
(a) (b)
Figure 9. Velocity cloud diagram of the N33 scenario. (a) Side view; (b) plan view.
3.2. Single Factor Study
On the basis of the results of the variance analysis, it can be seen that the only highly
significant factor affecting the effect of the venturi cap is the width of the roof opening.
The angle of the grille and the width of the wind deflector have significant effects, while
the other factors have insignificant effects. To determine the optimal design, the highly
significant factor and the significant factors were studied in these 33 scenarios.
In N33, a single factor study was carried out on the highly significant factor. Only the
width of the roof opening was changed, and the other six factors were fixed. The volumet-
ric flow rate of the venturi cap and the average temperature of the 1.2 m horizontal plane
were obtained through numerical simulation, as shown in Figure 10. When the width of
the roof opening was changed in the range between 0 mm and 2000 mm, the volume flow
rate of the venturi cap was the best at 1000 mm, with a maximum flow volume of 5.220
m3/s. This indicates that N33(A4B1C4D1E4F3G2) is still the optimal combination when the
width of the roof opening is within the range of 0 mm–2000 mm.
0 500 100 0 1500 2000
0
1
2
3
4
5
6
Volume flow rate
Temperature
The width of roof opening(mm)
Volume flow rate (m3/s)
305
306
307
308
309
310
Temperature (K)
Figure 10. Volumetric flow and temperature values for different widths of roof opening.
Single factor studies were carried out for the significant factors. Only the horizontal
width of the wind deflector was changed, and the other six factors were fixed. The volume
flow rate of the venturi cap and the average temperature of 1.2 m high horizontal plane
above the ground were obtained on the basis of numerical simulation, as shown in Figure
Figure 9. Velocity cloud diagram of the N33 scenario. (a) Side view; (b) plan view.
3.2. Single Factor Study
On the basis of the results of the variance analysis, it can be seen that the only highly
significant factor affecting the effect of the venturi cap is the width of the roof opening.
The angle of the grille and the width of the wind deflector have significant effects, while
the other factors have insignificant effects. To determine the optimal design, the highly
significant factor and the significant factors were studied in these 33 scenarios.
In N33, a single factor study was carried out on the highly significant factor. Only
the width of the roof opening was changed, and the other six factors were fixed. The
volumetric flow rate of the venturi cap and the average temperature of the 1.2 m horizontal
plane were obtained through numerical simulation, as shown in Figure 10. When the width
of the roof opening was changed in the range between 0 mm and 2000 mm, the volume
flow rate of the venturi cap was the best at 1000 mm, with a maximum flow volume of
5.220 m
3
/s. This indicates that N33(A
4
B
1
C
4
D
1
E
4
F
3
G
2
) is still the optimal combination
when the width of the roof opening is within the range of 0 mm–2000 mm.

Energies 2021,14, 5053 12 of 16
Energies 2021, 14, x FOR PEER REVIEW 12 of 17
(a) (b)
Figure 9. Velocity cloud diagram of the N33 scenario. (a) Side view; (b) plan view.
3.2. Single Factor Study
On the basis of the results of the variance analysis, it can be seen that the only highly
significant factor affecting the effect of the venturi cap is the width of the roof opening.
The angle of the grille and the width of the wind deflector have significant effects, while
the other factors have insignificant effects. To determine the optimal design, the highly
significant factor and the significant factors were studied in these 33 scenarios.
In N33, a single factor study was carried out on the highly significant factor. Only the
width of the roof opening was changed, and the other six factors were fixed. The volumet-
ric flow rate of the venturi cap and the average temperature of the 1.2 m horizontal plane
were obtained through numerical simulation, as shown in Figure 10. When the width of
the roof opening was changed in the range between 0 mm and 2000 mm, the volume flow
rate of the venturi cap was the best at 1000 mm, with a maximum flow volume of 5.220
m3/s. This indicates that N33(A4B1C4D1E4F3G2) is still the optimal combination when the
width of the roof opening is within the range of 0 mm–2000 mm.
0 500 100 0 1500 2000
0
1
2
3
4
5
6
Volume flow rate
Temperature
The width of roof opening(mm)
Volume flow rate (m3/s)
305
306
307
308
309
310
Temperature (K)
Figure 10. Volumetric flow and temperature values for different widths of roof opening.
Single factor studies were carried out for the significant factors. Only the horizontal
width of the wind deflector was changed, and the other six factors were fixed. The volume
flow rate of the venturi cap and the average temperature of 1.2 m high horizontal plane
above the ground were obtained on the basis of numerical simulation, as shown in Figure
Figure 10. Volumetric flow and temperature values for different widths of roof opening.
Single factor studies were carried out for the significant factors. Only the horizontal
width of the wind deflector was changed, and the other six factors were fixed. The
volume flow rate of the venturi cap and the average temperature of 1.2 m high horizontal
plane above the ground were obtained on the basis of numerical simulation, as shown in
Figure 11
. When the horizontal width of the wind deflector was changed in the range of
200 mm–1000 mm, the volume flow rate of the venturi cap had the best value at 400 mm,
where the volume flow rate reached a maximum of 5.507 m
3
/s. This shows that when
the horizontal width of the wind deflector was within the range of 200 mm–1000 mm, the
volume flow rate first increased and then decreased with increasing horizontal width of
the wind deflector. Similar to the analysis of the horizontal width of the wind deflector,
the angle of the grille was studied. The results are presented in Figure 12. When the grille
angle was 75◦, the volume flow rate reached its maximum value.
Energies 2021, 14, x FOR PEER REVIEW 13 of 17
11. When the horizontal width of the wind deflector was changed in the range of 200 mm–
1000 mm, the volume flow rate of the venturi cap had the best value at 400 mm, where the
volume flow rate reached a maximum of 5.507 m3/s. This shows that when the horizontal
width of the wind deflector was within the range of 200 mm–1000 mm, the volume flow
rate first increased and then decreased with increasing horizontal width of the wind de-
flector. Similar to the analysis of the horizontal width of the wind deflector, the angle of
the grille was studied. The results are presented in Figure 12. When the grille angle was
75°, the volume flow rate reached its maximum value.
0 500 1000
3
4
5
6
Volume flow rate
Temperature
The horizontal width of wind deflector(mm)
Volume flow rate (m3/s)
305
306
307
308
309
310
Temperature (K)
Figure 11. Values of volumetric flow and temperature at different horizontal widths of the wind
deflector.
20 40 60 80 100
2
3
4
5
6
Volume flow rate
Temperature
The angle of grille(°)
Volume flow rate (m3/s)
305
306
307
308
Temperature (K)
Figure 12. Volumetric flow and temperature values at different angles of grille.
On the basis of the analysis of the above parameters, N34(A4B1C4D2E4F3G2) was ob-
tained by adjusting the horizontal width of the wind deflector to 400 mm on the basis of
N33, and the maximum volume flow rate achieved was 5.507 m3/s. At the same time, in
the same scenario, without the venturi cap, the average temperature of the horizontal
plane at a height of 1.2 m above the ground in the whole building was 308.836 K, while
when the venturi cap was turned on, the average temperature of the plane was 305.834 K,
Figure 11.
Values of volumetric flow and temperature at different horizontal widths of the
wind deflector.

Energies 2021,14, 5053 13 of 16
Energies 2021, 14, x FOR PEER REVIEW 13 of 17
11. When the horizontal width of the wind deflector was changed in the range of 200 mm–
1000 mm, the volume flow rate of the venturi cap had the best value at 400 mm, where the
volume flow rate reached a maximum of 5.507 m3/s. This shows that when the horizontal
width of the wind deflector was within the range of 200 mm–1000 mm, the volume flow
rate first increased and then decreased with increasing horizontal width of the wind de-
flector. Similar to the analysis of the horizontal width of the wind deflector, the angle of
the grille was studied. The results are presented in Figure 12. When the grille angle was
75°, the volume flow rate reached its maximum value.
0 500 1000
3
4
5
6
Volume flow rate
Temperature
The horizontal width of wind deflector(mm)
Volume flow rate (m3/s)
305
306
307
308
309
310
Temperature (K)
Figure 11. Values of volumetric flow and temperature at different horizontal widths of the wind
deflector.
20 40 60 80 100
2
3
4
5
6
Volume flow rate
Temperature
The angle of grille(°)
Volume flow rate (m3/s)
305
306
307
308
Temperature (K)
Figure 12. Volumetric flow and temperature values at different angles of grille.
On the basis of the analysis of the above parameters, N34(A4B1C4D2E4F3G2) was ob-
tained by adjusting the horizontal width of the wind deflector to 400 mm on the basis of
N33, and the maximum volume flow rate achieved was 5.507 m3/s. At the same time, in
the same scenario, without the venturi cap, the average temperature of the horizontal
plane at a height of 1.2 m above the ground in the whole building was 308.836 K, while
when the venturi cap was turned on, the average temperature of the plane was 305.834 K,
Figure 12. Volumetric flow and temperature values at different angles of grille.
On the basis of the analysis of the above parameters, N34(A
4
B
1
C
4
D
2
E
4
F
3
G
2
) was
obtained by adjusting the horizontal width of the wind deflector to 400 mm on the basis of
N33, and the maximum volume flow rate achieved was 5.507 m
3
/s. At the same time, in
the same scenario, without the venturi cap, the average temperature of the horizontal plane
at a height of 1.2 m above the ground in the whole building was 308.836 K, while when
the venturi cap was turned on, the average temperature of the plane was
305.834 K
, which
is a reduction by 3.002 K. Therefore, it can be seen that the venturi cap is able to improve
the ventilation of indoor environments and reduce indoor temperatures. In summer, this
could lead to a reduction in the use of air conditioning equipment, thus achieving an
energy-saving effect.
4. Conclusions and Outlook
4.1. Conclusions
The orthogonal experimental design and variance analysis were performed using
SPSS, and the numerical simulation analysis was carried out using CFD. The feasibility
of using a venturi cap in the Xichang area was verified. The main key factors influencing
the venturi cap with respect to improving ventilation, and the degree of the effect were
obtained. An optimized combination scheme was provided within the research scope and
verified on the basis of numerical simulation. Therefore, the following conclusions can
be drawn:
1.
Variance analysis showed that the width of the roof opening had a highly significant
effect on the ventilation performance of the venturi cap, while the angle of the grille
and the horizontal width of the wind deflector had a significant impact. The height
of the wind deflector, the spacing of the grille slices, roof slope, and the angle of the
wind deflector were not significant.
2.
On the basis of the analysis of the highly significant factors and the significant factors,
it was found that the best solution was N34, that is, the width of the roof opening, the
angle of the grille, the horizontal width of wind deflector, the height of wind deflector,
the spacing of the grille slices, the roof slope and the angle of wind deflector were
assigned values of 1000 mm (A
4
), 15
◦
(B
1
), 800 mm (C
4
), 400 mm (D
2
), 45
◦
(E
4
), 75
◦
(F
3
), and 40 mm (G
2
), respectively; the volume flow rate reached 5.507 m
3
/s, and the
average temperature of the horizontal plane at a height of 1.2 m above the ground
dropped by 3.002 K.
This research on building ventilation in the Xichang area showed that the structure
is able to meet the needs of both residents and building characteristics, optimizing the

Energies 2021,14, 5053 14 of 16
ventilation conditions of local buildings while reducing indoor temperature and improving
indoor air quality.
4.2. Outlook
In this study, the length–width ratio and shape of the venturi cap were not taken
into consideration. The length of the venturi cap was set at a fixed length, and the area
was converted into the width for the purposes of research. The thickness of the grille
was also directly set at a fixed thickness, ignoring the possible influence of the change
in the thickness of the grille on the ventilation conditions. The size and location of the
air inlet were also fixed. In future research, these influencing factors should be further
analyzed in order to put forward suggestions for the better application of the venturi effect
in buildings and to provide design ideas and data references for the optimal design of
building ventilation.
China’s building energy consumption report 2020 reported that in 2018, China’s total
energy consumption was 2.147 billion tons of standard coal equivalent (tce), and its total
carbon emissions were 4.93 billion t CO
2
. Rural residential buildings account for 24% of
China’s building energy consumption and 21% of its carbon emissions, which are huge
numbers. The application of a venturi cap in architectural design can increase indoor
ventilation, bring more fresh outdoor air into the room, and reduce indoor temperature.
The reduction in the use of air-conditioning systems during the summer will help to
achieve the aim of reducing building energy consumption. Research regarding the venturi
cap could provide design ideas for the future reconstruction of old rural buildings in the
Xichang area in the future. In addition, in the context of COVID-19, indoor ventilation has
become more important. Fresh air is able to dilute any harmful substances in the air and
reduce the concentration of CO2, which is important for human health.
Author Contributions:
Conceptualization, L.Z.; Data curation, L.T.; Funding acquisition, Q.S. and
J.W.; Investigation, Z.D., H.L. (Haoru Liu) and J.W.; Methodology, L.Z., L.T., Q.S., F.L. and J.C.;
Project administration, Q.S.; Software, L.T., H.L. (Haolin Li) and J.C.; Supervision, L.Z. and Q.S.;
Visualization, L.T. and H.L. (Haolin Li); Writing—review & editing, L.Z., L.T., F.L., Z.D. and H.L.
(Haoru Liu). All authors have read and agreed to the published version of the manuscript.
Funding:
This research was funded by Sichuan Provincial Research Center for Philosophy and Social
Sciences—Sichuan Rural Development Research Center, grant number CR1908; the Chengdu Science
and Technology Bureau Soft Science Project, grant number 2019-RK00-00319-ZF; and the Soft Science
Project of Sichuan Provincial Science and Technology Department, grant number 2021JDR0076.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement:
The weather energy meteorological data of Xichang used in the numer-
ical simulation are all from CSWD files, which are downloaded from the website: https://energyplus.
net/weather-location/asia_wmo_region_2/CHN//CHN_Sichuan.Xichang.565710_CSWD (accessed
on 10 August 2020).
Acknowledgments:
We would like to thank Yukai Qin, Jiarui Yu for their help to investigate and
collect the data.
Conflicts of Interest: The authors declare no conflict of interest.
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