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Research Papers: Flows in Complex Systems

Numerical Investigation of Ventilation and Human Thermoregulation for Predicting Thermal Comfort of a Rider Wearing Ventilated Helmet

[+] Author and Article Information
Bhagwat Singh Shishodia

Applied Mechanics Department,
Indian Institute of Technology Delhi,
New Delhi 110016, India
e-mail: bhagwat.shishodia@gmail.com

Sanjeev Sanghi

Applied Mechanics Department,
Indian Institute of Technology Delhi,
New Delhi 110016, India
e-mail: sanghi@am.iitd.ac.in

Puneet Mahajan

Applied Mechanics Department,
Indian Institute of Technology Delhi,
New Delhi 110016, India
e-mail: mahajan@am.iitd.ac.in

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received May 16, 2016; final manuscript received January 28, 2017; published online April 6, 2017. Assoc. Editor: Elias Balaras.

J. Fluids Eng 139(6), 061103 (Apr 06, 2017) (13 pages) Paper No: FE-16-1311; doi: 10.1115/1.4036084 History: Received May 16, 2016; Revised January 28, 2017

Effectiveness of ventilated helmets in providing thermal comfort to a motorcycle rider is studied. Computational fluid dynamics (CFD) simulations of human thermoregulation system and the air flow in the air gap of a full-face motorcycle helmet are carried out. The thermal comfort of a rider is predicted using apparent temperature (AT) and wet-bulb global temperature (WBGT) heat indices. The effect of an increase in ambient temperature and relative humidity (RH) of air on the air flow and temperature in the region above the head is studied to predict the thermal comfort of the rider wearing full-face helmets. The effect of increasing the air gap between the head and the helmet is also studied. The results are then compared with the conditions when the rider is not wearing helmet. It is observed that the ventilated helmet is effective in providing thermal comfort to the rider only if the ambient air temperature is less than normal body temperature. For air temperature higher than the body temperature, vents do not provide any cooling to the head and the nonventilated helmet is more comfortable. Furthermore, CFD simulations are performed to investigate the effect of increase in RH in the ambient air on the thermal comfort of the rider. The increase in RH of air from 50% to 90% at a fixed ambient air temperature leads to an increase in AT and WBGT, indicating reduced thermal comfort of the rider.

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References

Figures

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Fig. 1

Conceptual figure of 65-node thermoregulation system [13]

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Fig. 2

Flowchart of JOS–CFD calculation [14]

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Fig. 3

Boundary conditions used for CFD and JOS human thermoregulations simulations

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Fig. 4

Head–helmet arrangement and mesh in the air gap of three-dimensional hemispherical model of helmet

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Fig. 5

Computational domain and boundary conditions for three-dimensional hemispherical head–helmet arrangement

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Fig. 6

Grid independence for three-dimensional hemispherical head–helmet arrangement

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Fig. 7

Comparison of x-velocities on a vertical line at the center of the air gap at the top of head in a hemispherical helmet

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Fig. 8

Front view of rider wearing helmet for condition: (a) helmet without vent and (b) helmet with three air vents in front

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Fig. 9

Computational domain for CFD simulation of air flow and human thermoregulation

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Fig. 10

Distribution of y+ near the rider's head

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Fig. 11

Pseudo head surface 1 mm away from head in the air gap

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Fig. 12

Qualitative comparison of velocity magnitude in the air gap at the central plane of helmet for the conditions for inlet velocity of 15 m/s at the domain inlet: (a) 2 mm raised helmet, (b) 6 mm raised helmet, (c) ventilated and 6 mm raised helmet, and (d) no helmet

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Fig. 13

Comparison of air flow at the exit in ventilated (a) and nonventilated helmet (b)

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Fig. 14

Qulatitative comparison of temperature in the air gap of helmet at central plane for the conditions when air entered domain with air inlet temperature of 30 °C: (a) 2 mm raised helmet, (b) 6 mm raised helmet, (c) ventilated and 6 mm raised helmet, and (d) no helmet

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Fig. 15

Magnitude of velocity contours on a surface 1 mm away from head, when the air inlet velocity is 15 m/s for the conditions: (a) 2 mm raised helmet and (b) 6 mm raised helmet, (c) ventilated and 6 mm raised helmet, and (d) no helmet

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Fig. 16

Temperature contours on a surface 1 mm away from head, when the air inlet temperature is 30 °C for the following conditions: (a) 2 mm raised helmet, (b) 6 mm raised helmet, (c) ventilated and 6 mm raised helmet, and (d) no helmet

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Fig. 17

Comparison of average values of (a) temperature, (b) AT, and (c) WBGT on a surface 1 mm away from head (X-axis represents the air inlet temperature in  °C)

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Fig. 18

Effect of increases in RH of air on average values of (a) temperature, (b) AT, and (c) WBGT heat indices on a surface 1 mm away from head

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