ORIGINAL
O. Kaynakli Æ E. Pulat Æ M. Kilic
Thermal comfort during heating and cooling periods in an automobile
Received: 9 September 2003 / Published online: 17 September 2004
Springer-Verlag 2004
Abstract Most vehicles have a heating, ventilation and
air conditioning (HVAC) device to control the thermal
environments of interior of the vehicle. But, under hot
summer season or cold winter conditions, it is difficult to
achieve and maintain thermal comfort in an automobile
from the start up to the steady-state conditions. During
these transition periods, an understanding of human
thermoregulatory processes facilitates the design and
development of improved heating and cooling systems.
This study presents a model of therma l interactions
between a human body and the interior environment of
an automobile. The model is based on the heat balance
equation for human body, combined with empirical
equations defining the sweat rate and mean skin tem-
perature. Simulation has been performed by the use of
transient conditions. The effects of both heatin g and
cooling processes on the thermal comfort inside the
automobile are investigated. Results are compared with
the present measurements and available experimental
data in the literature. It is shown that the agreement
between the experimental data and the model is very
good.
List of symbols
A surface area, m
2
c
p
specific heat, J/(kg K)
CSIG cold signal
f correction factor
h heat transfer coefficient, W/(m
2
K)
i segment number
j air or fabric layers number
k conductive heat transfer coefficient, W/(m K)
L heat load, W/m
2
m body mass, kg
_
m mass flow rate from per unit area, kg/(s m
2
)
M metabolic heat production rate, W
nl number of layers covering segment
p water vapor pressure, kPa
Q heat transfer rate, W
r outer radius of fabric layer
R thermal or evaporative resistance, (m
2
K)/W
or (m
2
kPa)/W
S heat storage, W
t time, s (unless specified in minutes)
T temperature,C
TS thermal sensation
V air velocity, m/s
w skin wettedness
W humidity ratio, kgH
2
O/kg dry air
_W external work rate accomplished, W
WSIG warm signal
x thickness, mm
Greek symbols
a ratio of skin layer mass to total body mass
g permeation efficiency
Subscripts
a air
al air layer
b body
bl blood
cd conduction
cl clothing
cr core
cv convection
dif diffusion
e exposed to convective and radiant environment
ev evaporation
O. Kaynakli Æ E. Pulat Æ M. Kilic (&)
Faculty of Engineering and Architecture,
Department of Mechanical Engineering, Uludag
˘
University,
Gorukle Campus, 16059 Bursa, Turkey
E-mail: mkilic@uludag.edu.tr
Tel.: +90-224-4429183
Fax: +90-224-4428021
Heat Mass Transfer (2005) 41: 449–458
DOI 10.1007/s00231-004-0558-9