Hindawi Publishing Corporation
Journal of Textiles
Volume 2014, Article ID 925320, 7 pages
http://dx.doi.org/10.1155/2014/925320
Research Article
A Design Tool for Clothing Applications:
Wind Resistant Fabric Layers and Permeable Vents
Phillip Gibson,1 Michael Sieber,1 Jerry Bieszczad,2 John Gagne,2
David Fogg,2 and Jintu Fan3
1
U.S. Army Natick Soldier Research, Development, and Engineering Center, Natick, MA 01760, USA
Creare, Inc., Hanover, NH 03755, USA
3
Cornell University, Ithaca, NY 14850, USA
2
Correspondence should be addressed to Phillip Gibson; [email protected]
Received 16 July 2014; Revised 30 October 2014; Accepted 1 November 2014; Published 18 November 2014
Academic Editor: Jiri Militky
Copyright © 2014 Phillip Gibson et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
A computational clothing design tool is used to examine the effects of different clothing design features upon performance.
Computational predictions of total heat and mass transfer coefficients of the clothing design tool showed good agreement with
experimental measurements obtained using a sweating thermal manikin for four different clothing systems, as well as for the
unclothed bare manikin. The specific clothing design features examined in this work are the size and placement of air-permeable
fabric vents in a protective suit composed primarily of a fabric-laminated polymer film layer. The air-permeable vents were shown
to provide additional ventilation and to significantly decrease both the total thermal insulation and the water vapor resistance of
the protective suit.
1. Introduction
Windproof and wind resistant clothing layers are important
in applications such as cold weather clothing and military
chemical and biological protective ensembles. Completely
windproof clothing provides protection from heat loss due
to air penetration in cold conditions but can also become
very uncomfortable when the wearer is working hard and
generating a lot of heat and sweat. The same situation arises
in protective clothing—some ventilation through the fabric
layers can be very helpful in mitigating heat stress and
extending wear time. Design tools that allow simultaneous
assessment of factors such as wind penetration, heat transfer,
moisture transport, and permeation of toxic substances can
assist in developing new clothing systems that strike a good
balance between protection and comfort.
We have shown previously that the wind resistance
and aerosol filtration properties of clothing layers can be
controlled by varying the deposition of electrospun fiber
membranes onto textile substrates [1], as shown in Figure 1.
Since nanofiber layers make it possible to control air flow
resistance over several orders of magnitude without affecting
other clothing properties, we are interested in the resulting consequences of using these materials in new clothing
designs. Electrospun elastomeric polyurethane membranes
are now used in commercial outerwear fabrics such as
“NeoShell” by Polartec, Inc., and take advantage of this ability
to “tune” air flow through the fabric without significantly
affecting other properties such as thermal insulation or water
vapor diffusion (breathability). These materials may be used
for either an entire clothing item, such as jacket or pants,
or incorporated into permeable “vents,” where the more
permeable fabric in certain areas of the garment provides
increased ventilation.
2. Approach
A protective clothing design tool under development by
Creare, Inc., for the U.S. military provides a physicsbased computational framework for iterative modification
2
Journal of Textiles
Air flow resistance (m−1 )
1010
109
108
107
10−4
10−3
10−2
Electrospun coating level (kg/m2 )
10−1
Figure 1: Air flow resistance of fabric layer modified by electrospun fiber coating level [1].
Primary clothing properties
(steady state):
Air flow resistance
Water vapor diffusion resistance
Thermal resistance
Clothing system:
Layers, gaps, vents,
closures, patches
Environment:
Temperature, humidity,
wind speed, thermal radiation
Body geometry:
Body segment size/diameter,
body surface temperature
Cylinders mapped to more realistic clothed image
Figure 2: Typical IP SPM simulation.
and assessment of protective clothing systems [2]. Creare’s
Individual Protection System Performance Model (IP SPM)
is built on a foundation of advanced computational fluid
dynamic and experimental results, but the software itself is
purposefully simplified to allow nonexpert users to modify
clothing designs and assess the consequences of various
clothing aspects such as fit, closures, interfaces, material
properties, and layering, upon comfort and protection. The IP
SPM model treats the clothed human body as an assemblage
of fabric-covered cylinders, although the graphical user interface maps clothing layers onto a more anatomically correct
human figure, as shown in Figure 2. Computational models
that include more detailed human and clothing geometry are
possible [3] and in fact are used as some of the guides for the
IP SPM software, but too much detail has been found to add
an unneeded level of complexity for a user-friendly design
tool, especially for nonexpert users.
In this study we focus upon the use of the IP SPM tool
to assess the relative importance of changing the air flow
resistance of fabric layers or permeable vent sections upon the
calculated total heat transfer resistance of the clothing system.
Several recent experimental papers have discussed the tradeoffs between fabric air flow resistance, clothing vents, and the
interaction with air flow due to external wind or body motion
[4–6].
3. Results and Discussion
3.1. Comparison of IP SPM Predictions with Thermal Manikin
Measurements. The Creare IP SPM can be configured to
simulate a thermal manikin, which is an important tool in
clothing comfort research. Figure 3 shows baseline comparison results for the IP SPM thermal manikin calculated overall
heat transfer coefficients as compared to some empirical
correlations obtained with humans [7] and thermal manikins
[8], as well as computational and analytical results from
heated cylinders [9].
Journal of Textiles
3
Thermal resistance (m2 -∘ C/W)
0.4
0.3
0.2
0.1
0
0
2
4
6
Wind speed (m/s)
8
10
Heat transfer coefficient from standing human [6]
Thermal manikin correlation [7]
Correlation from literature for bare cylinder in cross-flow [ 8]
CFD calculation for bare cylinder in cross-flow [8]
Calculated from SPM bare manikin model
Figure 3: Overall heat transfer coefficient of IP SPM thermal manikin as a function of wind speed.
0.30
0.25
0.25
0.20
0.20
Rt (m2 -∘ C/W)
Rt (m2 -∘ C/W)
0.30
0.15
0.15
0.10
0.10
0.05
0.00
0.05
0
2
4
6
Wind speed (mph)
Nude: IP SPM
Ensemble A: IP SPM
8
10
Ensemble B: IP SPM
Ensemble C: IP SPM
(a) IP SPM
0.00
0
2
4
6
Wind speed (mph)
Nude: experimental
Ensemble A: experimental
8
10
Ensemble B: experimental
Ensemble C: experimental
(b) Thermal manikin
Figure 4: Comparison of thermal insulation for the nude manikin and three clothing ensembles: (a) IP SPM model results versus (b)
experimental thermal manikin results.
Figure 3 shows an underprediction of bare manikin
values at low wind speeds when radiative heat transfer is
included in the IP SPM model; when this is removed from
the calculation (ℎrad of 4.5 W/m2 -∘ C), the IP SPM results
show good agreement with the convective-only heat transfer
calculations from [8] shown in Figure 3.
IP SPM predictions can be compared to experimental
thermal manikin results. Inputs to the IP SPM model require
clothing thermal resistance, water vapor diffusion resistance,
and air flow resistance for the fabric and some information
on the fit (space between the fabric and the body surface),
tightness of the closures and seams, and the extent of coverage
of the fabric over different sections of the body. Figure 4
shows a comparison of IP SPM predictions to experimental
results obtained by a thermal manikin [10, 11] for both
the bare (nude) condition and for three separate clothing
ensembles on the manikin.
As shown in Figure 4, the performance rankings between
the ensembles were correctly replicated by the IP SPM
predictions, for both the overall thermal resistance (shown
4
Journal of Textiles
1
Thermal resistance (m2 -∘ C/W)
Fabric air flow resistance (RD ) = 1 × 109 m−1
RD = 1 × 108
RD = 1 × 107
0.1
RD = 1 × 106
Bare cylinder (no fabric layer)
0.01
1
2
5
10
Wind speed (m/s)
Figure 5: Overall heat transfer resistance of fabric-covered cylinders in cross-flow conditions at various wind speeds [9].
0.20
Thermal resistance (m2 -∘ C/W)
Fabric air flow resistance (RD ) = 1 × 109 m−1
RD = 1 × 108
0.15
RD = 1 × 107
RD = 1 × 106
0.10
0.05
Bare SPM manikin (no fabric layer)
0
0
2
4
6
Wind speed (m/s)
8
10
Figure 6: Individual protection system performance model (IP SPM) predictions for variable air flow resistance of fabric layer.
in Figure 3) and evaporative resistances (not shown). This
is an important result because it indicates that in situations
where the exact experimental configurations are not known
or defined, the IP SPM can still be used to determine relative
garment rankings for thermal performance using nominal
configuration values (e.g., for garment fit).
3.2. Effect of Fabric Air Flow Resistance on Clothing System
Thermal Resistance. The IP SPM purposefully simplifies the
clothing/body model to be an assemblage of fabric-covered
cylinders. For a practical design tool, it has been found that
faithful reproduction of body geometry, along with details of
fabric folds, drape, and fit, can quickly make a computational
tool such as this only usable by dedicated experts. Previous
computational simulations of fabric-covered cylinders as an
analog to the human body [9] examined the effect of varying
only the fabric air flow resistance (all other properties kept
constant) and calculated the overall heat and mass transfer
coefficient, as shown in Figure 5.
The IP SPM allows a very similar computation to be
carried out for a more realistic clothing and body geometry.
The IP SPM is configured to simulate a set of wind-resistant
clothing (jacket and pants) that only varies the single property
of air flow resistance. A similar relationship thermal resistance as a function of external wind speed as was shown in
Figure 5 is shown in Figure 6 for the IP SPM model. Air flow
resistance is more important at high wind speeds, and once
the fabric becomes “wind-proof,” any further increase in air
flow resistance does not significantly affect heat transfer.
An example of the use of the IP SPM to examine some
simple clothing design variations is shown in Figure 7. Suit
A and suit B vary only in the air flow resistance of the jacket
Journal of Textiles
5
Wind speed (m/s)
15
30
Suit C (jacket and pants
with high air flow resistance,
1 × 109 m−1 , with looser fit)
40
0.02
Suit B (jacket changed to
high air flow resistance,
1 × 109 m−1 )
1.0
0.01
0.5
0
Suit A (jacket and pants with
Bare SPM
low air flow resistance,
thermal manikin 1 × 107 m−1 )
0
5
10
Wind speed (mi/h)
15
Thermal resistance (m2 -∘ C/W)
Thermal insulation (Clo)
1.5
0
0
20
Figure 7: Use of IP SPM to examine effect of fabric air flow resistance on overall thermal insulation.
Clothing properties (steady state)
Impermeable
mask, gloves,
and boots
(black)
Polymer film
laminate on
hood, torso,
pants
Airpermeable
vent fabric
on outer
torso, inner
arm, outer
leg
Polymer film laminate:
Thermal resistance = 0.005 m2 -K/W
Evaporative resistance = 15.4 m2 -Pa/W
Air flow resistance (impermeable, windproof)
Air permeable vent fabric:
Thermal resistance = 0.005 m2 -K/W
Evaporative resistance = 2.94 m2 -Pa/W
Air flow resistance varies:
1.38 × 108 m−1 (10 CFM)
4.60 × 107 m−1 (30 CFM)
2.76 × 107 m−1 (50 CFM)
Baseline chemical protective uniform fabric:
Thermal resistance = 0.034 m2 -K/W
Evaporative resistance = 9.20 m2 -Pa/W
Air flow resistance = 2.16 × 108 m−1 (6.4 CFM)
Baseline combat uniform fabric:
Thermal resistance = 0.017 m2 -K/W
Evaporative resistance = 3.14 m2 -Pa/W
Air flow resistance = 3.45 × 107 m−1 (40 CFM)
Figure 8: IPM SPM simulation to vary air flow resistance of permeable fabric vents in a membrane suit.
(causing slightly more heat loss at higher air flow conditions
for the less-permeable jacket). Suit C is wind-resistant, and
also has a much looser fit which traps more air under the
clothing, resulting in increased thermal insulation properties
for that configuration.
3.3. Effect of Permeable Fabric Vents on Thermal and Water
Vapor Resistance. An example of a more detailed design
study was performed with the IP SPM to examine the effect
of incorporating permeable fabric vents into a chemicalprotective suit that is primarily composed of a solid polymer
membrane that provides chemical protection, yet allows
some water vapor transport for comfort. It is anticipated that
such a complete membrane-based suit will not allow enough
ventilation by itself but must incorporate a venting strategy
of some kind. One solution would be to incorporate separate
vent panels composed of a more air-permeable fabric into the
membrane-based suit.
Figure 8 shows the basic IP SPM setup for this simulation.
Large air-permeable fabric vents are incorporated into the
protective suit, and the vent fabric air flow resistance is varied
in a systematic way. The suit also incorporates a protective
hood, mask, boots, and gloves, which are impermeable to
both air and water vapor. For comparison purposes, results
are also modeled for the polymer film laminate suit with no
vents incorporated into the design and two other baseline
cases of a suit made up of a standard chemical protective
uniform fabric and a standard combat uniform fabric. The
additional case of the nude manikin simulation was also
modeled, to provide a reference point for how much each
clothing system decreases thermal and evaporative transfer
from the human body.
6
Journal of Textiles
Wind speed (m/s)
0.5
0
2
4
6
8
0.4
0.3
0.2
0.1
0
0
5
10
Wind speed (mph)
15
20
Baseline chemical protective uniform
Polymer film laminate suit (no vents)
Polymer film laminate suit, large vents on arms, torso,
and legs (50 CFM)
Polymer film laminate suit, large vents on arms, torso,
and legs (30 CFM)
Polymer film laminate suit, large vents on arms, torso,
and legs (10 CFM)
Baseline combat uniform
Unclothed manikin baseline
Figure 9: Overall IP SPM manikin thermal resistance.
Figures 9 and 10 show the simulation result for these cases
described in Figure 8. Figure 9 shows the overall thermal
resistance of the IP SPM thermal manikin, over a range of air
flows from 0.5 to 20 mph. For the IP SPM manikin thermal
resistance, all the designs incorporating the polymer film
laminate (vented or unvented) showed very little differences,
since the thermal resistance of the fabric itself is minimal.
However, there are large differences between the polymer film
laminate suit and the baseline chemical protective uniform,
which is a much thicker material, with a higher measured
thermal resistance, which impedes dry heat transfer from
the body to the environment. The baseline combat uniform
shows a lower thermal resistance at higher wind speeds, as
a consequence of its lower air flow resistance (higher air
permeability), as opposed to the polymer film laminate fabric,
which is impermeable to wind. For overall IP SPM manikin
thermal resistance, the large air-permeable fabric vents on the
arms, torso, and legs do not make an appreciable difference to
the thermal comfort of this suit design.
Figure 10 shows the overall evaporative resistance of the
IP SPM manikin, over a range of air flows from 0.5 to 20 mph.
For the evaporative case, there are significant differences
between the different suit designs and fabrics. It is still the case
that none of the polymer film laminate suit designs approach
the performance of either the baseline combat uniform or the
nude manikin, but the incorporation of air-permeable fabric
vents does favorably impact the performance of the polymer
film laminate suit. The unvented polymer film laminate
suit has the highest evaporative resistance of any of the
suits modeled. As the vent fabric air permeability increases,
Total evaporative resistance Ret (m2 -Pa/W)
Total thermal resistance Rct (m2 -K/W)
Wind speed (m/s)
0.08
0
2
4
6
8
0.06
0.04
0.02
0
0
5
10
Wind speed (mph)
15
20
Polymer film laminate suit (no vents)
Polymer film laminate suit, large vents on arms, torso,
and legs (10 CFM)
Polymer film laminate suit, large vents on arms, torso,
and legs (30 CFM)
Polymer film laminate suit, large vents on arms, torso,
and legs (50 CFM)
Baseline chemical protective uniform
Baseline combat uniform
Unclothed manikin baseline
Figure 10: Overall IP SPM manikin evaporative resistance.
the polymer film laminate suit becomes progressively better,
and the design incorporating fabric vents with an air flow
resistance of 2.8 × 107 m−1 (50 CFM) has the best performance, approaching the evaporative resistance of the baseline
chemical protective uniform, which is entirely air-permeable.
4. Conclusions
Simplified clothing design tools would greatly enhance our
ability to iteratively vary clothing design features and examine
the consequences for comfort and protection. Further verification and validation with experimental thermal manikin
measurements will be required for a variety of clothing
ensembles, so that results predicted with the model can be
used as a reliable design tool in the future.
Conflict of Interests
Jerry Bieszczad, John Gagne, and David Fogg are employed
by the commercial entity, Creare, Inc., which developed the
computational software mentioned in the paper.
Acknowledgment
Funding for this work was provided by the United States
Defense Threat Reduction Agency.
Journal of Textiles
References
[1] P. Gibson, H. Schreuder-Gibson, and D. Rivin, “Transport properties of porous membranes based on electrospun nanofibers,”
Colloids and Surfaces A: Physicochemical and Engineering
Aspects, vol. 187-188, pp. 469–481, 2001.
[2] J. Bieszczad, “Physics-based modeling and test methods for
improving aerosol protection and reducing thermal burden
of IPE,” in Proceedings of the Chemical and Biological Defense
Science and Technology Conference, Las Vegas, Nev, USA,
November 2011.
[3] P. Gibson, J. Barry, R. Hill, P. Brasser, M. Sober, and C. Kleijn,
“Computational modeling of clothing performance,” in Thermal
and Moisture Transport in Fibrous Materials, N. Pan and P.
Gibson, Eds., pp. 542–559, Woodhead Publishing, Cambridge,
UK, 2006.
[4] M. P. Morrissey and R. M. Rossi, “The effect of wind, body
movement and garment adjustments on the effective thermal
resistance of clothing with low and high air permeability
insulation,” Textile Research Journal, vol. 84, no. 6, pp. 583–592,
2014.
[5] Y. Ke, G. Havenith, X. Zhang, X. Li, and J. Li, “Effects of wind
and clothing apertures on local clothing ventilation rates and
thermal insulation,” Textile Research Journal, vol. 84, no. 9, pp.
941–952, 2014.
[6] M. P. Morrissey and R. M. Rossi, “The influence of fabric air permeability on the efficacy of ventilation features,” International
Journal of Clothing Science and Technology, vol. 25, no. 6, pp.
440–450, 2013.
[7] U. Danielsson, “Windchill and the risk of tissue freezing,”
Journal of Applied Physiology, vol. 81, no. 6, pp. 2666–2673, 1996.
[8] A. V. M. Oliveira, A. R. Gaspar, S. C. Francisco, and D. A.
Quintela, “Convective heat transfer from a nude body under
calm conditions: assessment of the effects of walking with a
thermal manikin,” International Journal of Biometeorology, vol.
56, no. 2, pp. 319–332, 2012.
[9] P. Gibson, “Modeling heat and mass transfer from fabriccovered cylinders,” Journal of Engineered Fibers and Fabrics, vol.
4, no. 1, pp. 1–8, 2009.
[10] J. Fan and X. Qian, “New functions and applications of Walter,
the sweating fabric manikin,” European Journal of Applied
Physiology, vol. 92, no. 6, pp. 641–644, 2004.
[11] J. Fan and Y. S. Chen, “Measurement of clothing thermal insulation and moisture vapour resistance using a novel perspiring
fabric thermal manikin,” Measurement Science and Technology,
vol. 13, no. 7, pp. 1115–1123, 2002.
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