Analysis of Different Shape Ventilation Elements for Protective
Clothing
ALEXANDER JANUSHEVSKIS1, SANJAY RAJNI VEJANAND1, AGRIS GULEVSKIS2
1Institute of Mechanics and Mechanical Engineering
Riga Technical University.
6b, Kipsalas Street, Riga, LV-1048,
LATVIA
2Ekasol Ltd. 15, Jauna Street, Ropazi, LV-2135,
LATVIA
Key-Words: - flow simulation, protective jacket, ventilation element, heat transfer
Received: June 15, 2021. Revised: June 21, 2022. Accepted: July 12, 2022. Published: August 29, 2022.
1 Introduction
Even in the temperate climate zone, the rise in
average temperature brought on by climate change
has raised the demand for additional outdoor
cooling of the human body. The human body
produces a substantial quantity of heat in hotter
environments or under heavy physical load
conditions, which must be expelled from the body to
avoid dangerous overheating [1]. When human body
temperature goes above specific point, sweating
starts, this phenomenon occurs due the body's
natural thermoregulation, as the heat emitted by the
body is used by the evaporation of the liquid [2].
The circulation of air and the relative humidity at
the body's surface determine the evaporation
intensity. To improve perspiration in the airspace
between the body and clothing, moist air or even
saturated vapour must be evacuated from the body
[3]. There are many venting methods for clothing
[4], including various vents, the use of mesh fabric
in various areas of clothing, and others, but they
often do not fully ensure efficient air exchange and
safety from various of external environmental
conditions. For an instance, the mesh fabric offers
effective body cooling and air circulation but is not
resistant to radiations of sun, insect bites, or other
mechanical effects, which can be crucial for various
clothing items in hot environmental conditions.
Commonly utilized breathable fabrics offer enough
air permeability but usually inadequate body
ventilation and mechanical shielding, for instance
against several insect species like mosquitoes,
which are transmitters of many hazardous diseases
(e.g., dengue, malaria). Contrary, wearing garments
made of thick textiles that offer sufficient protection
against insects, greatly raises the danger of
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DOI: 10.37394/232013.2022.17.14
Alexander Janushevskis, Sanjay Rajni Vejanand, Agris Gulevskis
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Abstract: People's thermoregulation may be hampered by exposure to extreme temperatures. Because of this, it
is crucial to consider how fabric cooling and ventilation may affect human comfort while designing clothing.
There is a demand on the market for more effective technical solutions and materials to be used in the external
part of protective gear, while also ensuring the necessary ventilation even in warm environmental conditions
and during heavy physical load. This is due to the growing interest in the market for efficient protection of the
human body against exposure to extreme weather conditions. In this article a simple elliptical model of the body
and the jacket is used to reduce the complexity of the problem. Five different shapes of ventilation elements
named as E1 to E5 are designed for the study and the numerical results for the pressure, temperature and heat
flux are calculated using SolidWorks Flow Simulation at three different inlet air velocity of 2, 5 and 8 m/s. The
acquired results display interesting flow patterns and how the ventilation elements' shapes might influence the
flow at various wind velocities. The results are compared and analyzed in terms of heat flux, pressure difference
and temperature difference. The main objective is to determine which element's geometrical shape gives the
smallest flow energy losses in the cell flow channel. If the pressure difference is higher, flow energy losses will
also be high, and if the flow energy losses are higher, the body cooling decreases. The obtained results show
that pressure difference increases gradually with the increasing inlet velocity. Moreover, results also indicates
how different shapes of ventilation elements can affect the flow, pressure difference and flow energy losses.
Based on analysis of obtained simulation results the most perspective ventilation element is proposed.
overheating of the body. There is necessity to
use composite materials for protective apparel that
will protect the body mechanically and enhance
airflow between the body and the garment [5, 6].
The weight of the protective gear is not greatly
increased while the essential ergonomic properties
and aesthetic value are maintained by combining the
essential characteristics of fabric (for example,
elasticity, optimal weight to strength ratio) [7].
When dense fabric is used to ensure mechanical
protection of the body against extreme weather
conditions like sun radiations, dust, rain, insect
access and their bites, the outer part of apparel may
not have enough air permeability. As a result, warm,
moist air may build up at the body, causing
discomfort or even the possibility of overheating of
the body. To enhance air exchange, multiple
closable vents and open areas of garments have been
developed [8]. However, this only results in a partial
improvement in air exchange. The primary aspect
of established approach is that it effectively protects
the human body from the effects of extreme climatic
conditions, ensuring the necessary air
permeability under-clothing ventilation, and
lowering the risk of overheating [9]. In order to
meet the objective, different ventilation elements are
designed, and a complex task of shape optimization
of the element is carried out. There is a need for
more effective technical solutions and materials to
be used in the external part of protective suits, while
also helping to ensure the required air circulation
even in warm environmental conditions and during
heavy physical load. This is due to the growing
market interest in efficient human body protection
against effects of extreme weather conditions.
2 Model for Ventilation Analysis
Fig. 1: Model design [10]
There are five different shaped ventilation elements
are used in this study to analyze and compare the
effectivity of each form. The shape and names of
each ventilation elements are depicted in fig 2. The
location of the ventilation element in relation to the
jacket's inlet hole is indicated by a circle in the fig 2.
The shape of element E4 and E5 is circular with
different curvature, the main difference is that E4
has the position when element is attached tangent to
the inlet hole, while E5 is attached concentric to the
inlet hole.
Fig. 2: Ventilation elements
In this study results are obtained in SolidWorks
internal flow simulation tool. The study is
conducted at intake air speeds of 2, 5, and 8 m/s. In
the initial boundary conditions, air temperature of
20 °C and environmental pressure of 101325 Pa, are
set as standard values for the investigation. At the
beginning of the simulation, distinct materials with
particular material properties are assigned to the
jacket and body. For all the ventilation elements,
same material properties as of jacket is considered
in the study. These materials properties are listed in
table 1. The normal body temperature is set at 36.5
°C. It is also considered that human body generates
200 W of heat under normal walking condition [11].
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To reduce the complexity of the problem in this
study, a simple elliptical shape model of the jacket
and body are designed and assembled such that the
body remains in center and jacket over it with a
uniform gap of 2.2 mm in between. The schematic
drawing of the model is shown in the figure 1. There
is a single inlet ventilation hole of 2 mm diameter
in front side and ten outlet holes of 4 mm diameter
at the back side of the jacket.
Table 1. Material properties
Material property
Human
body
Jacket
Average density [kg/m3]
985
1420
Specific heat [J/kg. K]
3600 [12]
1140
Thermal conductivity
[W/m. K]
0.21 [13]
0.261
3 Results and Discussion
The Flow Simulation study was performed with all
the elements having the same set of values as
discussed in the previous chapter, and the results are
presented for the physical time of 5 seconds. Since
this is a transient process, allowing longer physical
time in the investigation will lead to longer
computational time to obtain the solution.
Moreover, difference in the obtained results would
be almost same at any specific time; hence, to
reduce computational time, smaller physical time of
5 seconds is selected for the study.
Element
Velocity [m/s]
E1
2
5
8
E2
2
5
8
E3
2
5
8
2
Pressure Plots
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E4
5
8
E5
2
5
8
Fig. 3: Flow trajectories
Above fig 3, shows pressure distribution for each
ventilation element at different inlet velocities. In
order to compare the pressure distribution for all
mentioned cases, an equal scale is used in each
pressure plots, and the corresponding pressure
values are listed in Table 2. The right column image
in fig 3, is an enlarged view close to the ventilation
hole to show how ventilation elements affect the
flow route as well as pressure distribution at various
air velocities. The left column picture is an
isometric view of the pressure distribution over the
entire model with the same color scale for easy
comparison.
Velocity [m/s]
2
5
8
Fig. 4: Surface temperature for E1
The temperature plots for ventilation element E1
are presented in the fig 4, where left column shows
temperature distribution over the entire solid body
model, while right column is zoom view near the
ventilation hole for easy visualization of
temperature distribution near the ventilation hole. In
a similar manner, temperature plots for other
ventilation elements are examined, and
obtained values of results are listed in Table 2. The
temperature plots make it clear evident that when
inflow velocity increases from 2 to 8 m/s, the
cooling coverage area grows closer to the
ventilation hole. This pattern is also true in case of
other mentioned ventilation elements. To make
comparisons and visualizations simple, an equal
scale is used here.
Temperature Plots
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Fig. 5: Flux plot for element E1 at 2 m/s
In fig 5, Body-1/Boss-Extrude1 and
Jacket_Elliptical-1 are references to the human
body and jacket model respectively, while the
Default Fluid Subdomain refers to the study fluid
(air). The Outer Domain, in the flux plot depicts the
amount of heat lost into the environment. As
illustrated in figure 5, the flux plots are used to
compute the rate of heat transfer in each case and
obtained values for the respective elements are
listed in the Table 2.
Table 2. Numerical values of results
Elements
Inlet
Velocity
[m/s]
Values
Pressure
[Pa]
Temperature
[◦C]
E1
2
Max
101329.45
36.50
Min
101325.22
30.64
Avg.
101328.06
36.50
5
Max
101336.79
36.50
Min
101325.25
29.30
Avg.
101328.06
36.50
8
Max
101349.03
36.50
Min
101321.09
28.74
Avg.
101328.09
36.50
E2
2
Max
101329.01
36.50
Min
101325.22
32.78
Avg.
101328.05
36.50
5
Max
101333.80
36.50
Min
101325.24
31.77
Avg.
101328.04
36.50
8
Max
101342.91
36.50
Min
101323.10
31.17
Avg.
101328.09
36.50
2
Max
101329.28
36.50
Min
101325.22
33.01
Avg.
101328.05
36.50
Max
101335.30
36.50
E3
5
Min
101325.16
31.86
Avg.
101328.11
36.50
8
Max
101344.94
36.50
Min
101321.96
31.21
Avg.
101328.12
36.50
E4
2
Max
101329.25
36.50
Min
101325.19
32.69
Avg.
101328.01
36.50
5
Max
101335.55
36.50
Min
101325.24
31.62
Avg.
101328.03
36.50
8
Max
101347.70
36.50
Min
101322.24
31.22
Avg.
101328.04
36.50
E5
2
Max
101329.28
36.50
Min
101325.26
33.35
Avg.
101328.04
36.50
5
Max
101332.25
36.50
Min
101325.27
32.89
Avg.
101328.06
36.50
8
Max
101338.54
36.50
Min
101325.14
32.77
Avg.
101328.08
36.50
Table 2 shows detail values of obtained results,
Max, Min and Avg in the table refers to the
maximum, minimum and average values of the
results respectively. The given value of temperature
shows surface temperature of the body. The pressure
and temperature differences are calculated from the
maximum and minimum values listed in table 2,
while the heat flux is calculated from the flux plot as
shown in fig 5. These obtained values of heat
transfer, pressure and temperature differences are
used for comparing effectivity of ventilation
elements and proposing most effective ventilation
element.
Fig. 6: Pressure difference v/s velocity
0
5
10
15
20
25
30
2 5 8
Pressure Difference [Pa]
Inlet velocity [m/s]
E1
E2
E3
E4
E5
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Fig. 7: Temperature difference (ΔT) v/s velocity
Fig. 8: Heat flux v/s velocity
Figure 6 indicates that all ventilation elements
exhibit a steady rise in pressure difference from
lower to higher air velocities. All elements initially
exhibit nearly identical pressure differences at lower
velocities of 2 m/s, but at 5 and 8 m/s, this gap
steadily increases. Moreover, results with element
E5 shows the lowest pressure difference of all the
elements, which indicates better performance since
the flow would be more uniform with less
pressure variations. The element E5 produces a
more gradual temperature variation with
the increased velocity, which can be observed in fig
7, this results in less temperature swings due to air
fluctuation and better comfort of the body. In the
figure 8, mentioned values of heat flux is the total
amount of heat transfer from body to jacket through
the fluid for each element at different velocity.
Since there is unit ventilation system in this
investigation, heat transfer is nearly identical for all
the cases. This is a crucial factor since a higher rate
of heat transmission leads to increased
body cooling.
4 Conclusion
The primary goal of this study was to determine
which geometrical configuration of ventilation
elements results in the lowest flow energy losses in
the cell flow channel and may provide better
cooling. From the obtained results and its
comparison, it can be said that it is very important to
consider the system's operating parameters to select
the appropriate component, because some elements
may work well at lower speeds but may not perform
effectively at higher velocities. It is also evident
from the results analysis that element E5 provides
lowest pressure difference and smaller energy losses
at the inlet flow channel than other mentioned
elements in the study. A smaller pressure difference
results in more uniform flow throughout the system
and less flow fluctuations and when you have less
fluctuations in the flow, energy losses are also
small, which ultimately provide better cooling of the
system. Moreover, E5 offers more gradual
temperature difference at different inlet velocities,
resulting in less variations of temperature due to air
fluctuation. As a person moves in different
directions, the air intake through the protective
jacket's vents may come from various sides and
angles, which may result in flow fluctuations. If
there are higher temperature variations at different
air velocities, it may cause higher temperature at
one point and lower at other, which may create
discomfort of the body.
Considering all the results and analysis points,
element E5 is the most suitable of all the mentioned
ventilation elements in the study, which could
provide better cooling and comfort of the body.
Predicting fluid flow and selecting effective element
design is a complex task but it is possible through
proper optimization and simulation analysis as
mentioned in this study. In addition, the created
models can be utilized for comparing ventilation
effectiveness analysis, enabling further research,
such as improving the positioning of various
ventilation elements on protective garments.
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Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
Policy)
-Sanjay Vejanand carried out flow simulation and
results analysis.
-Alexander Janushevskis gave contribution to
problem statement and development of common 3D
model as well as results interpretation.
-Agris Gulevskis gave contribution in development
of detail shapes of ventilation elements and
comparison of numerical results.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
This publication has been produced with the support
of the Doctoral Grant Programme of Riga Technical
University, project No. 2-00338.
Creative Commons Attribution License 4.0
(Attribution 4.0 International, CC BY 4.0)
This article is published under the terms of the
Creative Commons Attribution License 4.0
https://creativecommons.org/licenses/by/4.0/deed.en
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DOI: 10.37394/232013.2022.17.14
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