Thermal comfort evaluation inside a car parked under sun and shadow using a thermal manikin

Abstract

During the summer, vehicle passengers may reach a comfort state, if the sun direct solar radiation do not affect them. Human body parts exposed to the sun, experience a high uncomfortable state which have a direct impact to the global sensation of the all body. The purpose of this study is to deepen the knowledge about the thermal phenomena that occur in cabin and its effects to the thermal state experienced by the driver during a summer sunny. This way we compare temperatures, humidity and Equivalent Temperature (t eq ) index acquired with an advanced thermal manikin for 3 scenarios. Results reveals that for a direct solar radiation of 500 Wm ⁻² temperature inside of the car rise with 10°C. Also, the values of t eq for the manikin parts exposed exceed value of 36°C leading to a very hot thermal state for all body.

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IOP Conference Series: Earth and Environmental Science
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Thermal comfort evaluation inside a car parked under sun and shadow
using a thermal manikin
To cite this article: P A Danca et al 2021 IOP Conf. Ser.: Earth Environ. Sci. 664 012064
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The 7th Conference of the Sustainable Solutions for Energy and Environment
IOP Conf. Series: Earth and Environmental Science 664 (2021) 012064
IOP Publishing
doi:10.1088/1755-1315/664/1/012064
1
Thermal comfort evaluation inside a car parked under sun
and shadow using a thermal manikin
P A Danca1,2, I. Nastase1, C. Croitoru1, F. Bode1,3 and M. Sandu1
1CAMBI Research Center, Technical University of Civil Engineering Bucharest, 021414
Bucharest, Romania
2National Institute for R&D in Electric Engineering ICPE-CA, Department of Renewable Energy Sources
and Energy Efficiency, 313 Splaiul Unirii, 030138 Bucharest, Romania
3Technical University of Cluj Napoca, Department of Mechanical Engineering 400020 Cluj -
Napoca, Romania
Correspondence: paul.danca09@gmail.com
Abstract. During the summer, vehicle passengers may reach a comfort state, if the sun direct
solar radiation do not affect them. Human body parts exposed to the sun, experience a high
uncomfortable state which have a direct impact to the global sensation of the all body. The
purpose of this study is to deepen the knowledge about the thermal phenomena that occur in
cabin and its effects to the thermal state experienced by the driver during a summer sunny. This
way we compare temperatures, humidity and Equivalent Temperature (teq) index acquired with
an advanced thermal manikin for 3 scenarios. Results reveals that for a direct solar radiation of
500 Wm−2 temperature inside of the car rise with 10°C. Also, the values of teq for the manikin
parts exposed exceed value of 36°C leading to a very hot thermal state for all body.
1. Introduction
The most common comfort evaluation index was developed by Fanger [1]and results from equation with
six parameters (air temperature, air velocity, mean radian temperature, relative humidity, clothing
insulation and metabolic rate). From these air temperature is considered to be the most influent. Situation
change when human body is exposed to the solar radiation. Direct solar radiation is potent determinant
of comfort. In winter it may, on balance, result in a pleasant sensation if the ambient air temperature or
MRT is low. In the summer, solar radiation falling directly on a person significantly affects their
perception of thermal comfort [2]. One of the situations where people are exposed frequently to the solar
radiation is when they are using vehicles. Adding to this other aspects as lack of space, asymmetry of
radiation, low temperature and high velocity introduced by the ventilation system make vehicle
environment far complex than those from the buildings. In the last years were performed many studies
with this thematic. One of these was made by Hodder [3], he performed investigation of the solar
radiation effects over the thermal sensation votes of the human subjects. They were exposed to four
levels of simulated solar radiation: 0, 200, 400 and 600 Wm−2. Results reveals that with every increase
of simulated solar radiation, the value of thermal comfort increase with a point on PMV scale, after 30
minutes of exposure. There was a tendency for the lower legs and feet to be slightly cooler than the
upper regions of the body. This could be due to these parts of the body being shielded from the direct
radiation.

The 7th Conference of the Sustainable Solutions for Energy and Environment
IOP Conf. Series: Earth and Environmental Science 664 (2021) 012064
IOP Publishing
doi:10.1088/1755-1315/664/1/012064
2
In the summer, direct solar radiation can create asymmetry radiation by heating some of surfaces from
car as, dashboard, seats, steering wheel.
Our research team has performed different experimental numerical studies [4-13] in order to deepen the
knowledge of the phenomena that occur inside the vehicle cabin, and to show the effects of different
setups over the thermal state. Based on the previous experiences, in this study we intended to show the
effects of solar radiation over cabin environment and over the manikin thermal state
2. Measurement protocol and equipment
Three measurement sessions were performed inside of Renault Megane hatchback car from Figure 1 as
fallowing: session I in a hall to avoid solar radiation; session II outside at the shadow; and session III in
full sun. Used vehicle have an air conditioning system with manual control system. Conditioned air was
introduced by the dashboard diffusers. Each measurement lasting 45 minutes and the inlet air flowrate
was change as fallowing: first 15 minutes a total mass flow rate of 0,033 kg/s, after 15 minutes with a
total mass flow rate of 0,052 kg/s and during the last 15 minutes total mass flow rate of 0,067 kg/s of
cold air. These three value of mass flow rate correspond to the first three positions of the air speed
regulator of the ventilation system. More details of the determination of these values can be seen in [12,
13]. Outside, experimental car was placed with the front to the west, front seats and left side of the car
being exposed to direct sun radiation.
Figure 1 Vehicle placed inside and outside during the measurement sessions
Inside of the car 8 thermocouples was placed on the fallowing surfaces: driver side window, passenger
side window, windshield, dashboard, center outlet, left side outlet, ceiling and floor. In cabin center
temperature and humidity was recorded with a FHA646-E1 probe manufactured by Ahlborn. Another
two AX-DT200 wireless probes were placed at the chest level of the back passengers.
Solar radiation was recorded with a Pyranometer Almemo FLA 628S probe, placed on the car during
the acquisition. More details of used probes and data loggers are in Table 1

The 7th Conference of the Sustainable Solutions for Energy and Environment
IOP Conf. Series: Earth and Environmental Science 664 (2021) 012064
IOP Publishing
doi:10.1088/1755-1315/664/1/012064
3
Table 1 Equipment used during the measurement sessions
Equipment
Parameter
Range
Accuracy
Data logger Almemo 710
-
-
- AA precision class
Data logger Almemo 2690
-
-
- AA precision class
Pyranometer Almemo FLA
628S
Global radiation
0 to 1500 W/m2
- cosine effect <3% of measured value (0 to 80 °
inclination)
- azimuth effect <3% of measured value
temperature influence <1% of measured value (-20 to +
40 °C)
AX-DT200 AXIOMET
Temperature
-20...70°C
- ±0,3°C
Humidity
0...100% RH
- ±2%
Thermocouple type K
Temperature
–60 to +175°C
±0.1°C
Capacitive humidity sensor
Type FHA646-E1
Temperature,
Relative
Humidity
–20 to +60°C
5...98% RH
± 2% RH at nominal temperature
Before each measurement session, vehicle engine was turned on for 30 minutes to warm up it.
Even the three measurement sessions were performed in external uncontrolled conditions, outside
temperature variation during the three measurement sessions in presented in Figure 2. It can be observed
there is small difference of 2-3°C which is more visible to the end of those 45 minutes.
Figure 2 Exterior temperature variation
In our study, the teq values are calculated with an advanced thermal manikin with 79 zone independently
controlled and neuro-fuzzy control. The manikin was developed in our laboratory with the support of
Mechatronics Department of the National Institute of Aerospace Research Elie Carafoli. The thermal
manikin was designed for both seated and standing postures. The size of the manikin is defined by the
standard skin surface of a human of 1.8 m² [14, 15]. The equivalent temperature that represents an
indication of thermal comfort is obtained by evaluating the power consumption of a region of the
manikin (see equation 1). Due to the pwm (pulse with modulation) control signal which commutes on
and off between maximum and minimum voltage, the power consumed by the thermostatic system was
calculated by creating a calibration slope between pwm duty-cycle and the power calculated as a point
by point mean of a single pulse period. The voltage drop on the patch was calculated differentially by
measuring with the Hantek DSO5102P oscilloscope the voltage drops on the whole circuit from which
it was subtracted the voltage drop on the transistors. The current consumed by the patch was measured
with TH5A current transducer.
𝜽𝒆𝒄𝒉 = 𝜽𝒓𝒆𝒈 −𝑷
𝑺∗ 𝒉𝒄𝒂𝒍 (1)
where:
θech - equivalent temperature;
θreg - mean temperature of surface region calculated using a sliding average over a pre-set period;
S - surface area of manikin’s region;

The 7th Conference of the Sustainable Solutions for Energy and Environment
IOP Conf. Series: Earth and Environmental Science 664 (2021) 012064
IOP Publishing
doi:10.1088/1755-1315/664/1/012064
4
P - mean power consumption calculated using a sliding average over a pre-set period;
hcal - convection coefficient calculated with equation (4) at constant environment temperature (θech) of
24 ºC and manikin’s surface temperature controlled at 34 ºC.
Figure 3 Thermal manikin placed in the driver place.
The 79 zones were grouped in 16 zones fallowing the prescription of the standard [16]. The manikin
was placed on the place of the driver, with the left hand on the steering wheel and left hand on the
gearshift as is showing in Figure 3. The imposed temperature of the manikin was 34 °C. In order to
stabilizes the temperature on the surface of the manikin, it was turned on around 20 minutes.
3. Results and discussions
When the car was placed on the hall, mean temperature measured in the center of the car is 25°C for the
first 15 minutes, 23,5°C for the second 15 minutes and 20,5°C for the last 15 minutes. When the car was
placed at the shadow temperatures recorded in center are with 5°C higher than from the hall. Sun
presents increase temperature with 6-7°C in center of the car, comparing with the case with car in
shadow. The difference of 5°C between the first two cases is explain by the fact that the car was placed
in the son for some hours before the measurement.
Figure 4 Temperature variation in center of the car
Passenger and driver windows temperature variation are drowned in Figure 5. Blue line is the window
variation in hall. We choose to represent only the driver window, because there is no significant
difference between the left and right window in hall. We can see there is a insignificant difference of
windows temperatures at shadow. In session III driver window was exposed to direct solar radiation,
that warming it to 55°C. In this case passenger window temperature was around 40°C. Comparing the
two recorded temperature we can say solar radiation is leading to an asymmetric radiation inside cabin.

The 7th Conference of the Sustainable Solutions for Energy and Environment
IOP Conf. Series: Earth and Environmental Science 664 (2021) 012064
IOP Publishing
doi:10.1088/1755-1315/664/1/012064
5
Figure 5 temperatures of the left and right windows when the car
Dashboard temperature reached the value of 40°C at the end of the second 15 minutes see Figure 6 with
car exposed to sun. After another 15 minutes decrease to 35°C. There is a tendency to decrease
dashboard temperature in the last 15 minutes when fan speed is on the third position and the airflow
introduced by climatization system is 0,067 kg/s.
Figure 6 Dashboard temperature variation
In a previous study [12] we saw that the temperature at the inlets is different due to the heat exchanged
trough the pipes placed inside the dashboard, each pipe having different shape and length. These
differences are more evident in Figure 7 andFigure 8 where are presented air temperatures introduced
trough left side and center inlet. The difference reach 15°C between cases in hall and outside, while
between the two sessions made outside, the difference is insignificant. This is because the session with
the car at the shadow was made after the car was placed in the sun for 3 hours.
Figure 7 Air temperature at the left side inlet

The 7th Conference of the Sustainable Solutions for Energy and Environment
IOP Conf. Series: Earth and Environmental Science 664 (2021) 012064
IOP Publishing
doi:10.1088/1755-1315/664/1/012064
6
Figure 8 Air temperature at the center inlet
In Table 2 are presented teq achieved with the manikin. Can be notified that, although, at the shadow,
cold air provided by ventilation system lead to a cool sensation for arms, with vehicle in sun it
improves equivalent temperature value by decreasing it from 41,3 °C for V1 to 37,5 °C to V3. This
decrease can be seen also at the level of chest, head, left hand and pelvic region. On a other hand,
temperature of manikin’s back remained stable, with a small difference between session I and other
two. It may be explained by the temperature stored by the seat, from the sun prior measurement
sessions. Table 2 Equivalent temperature recorded with the thermal manikin.
Velocity step
V1
V2
V3
Mass flow rate introduced
0,033 kg/s
0,052 kg/s
0,067 kg/s
Body part
Hall
Shadow
Sun
Hall
Shadow
Sun
Hall
Shadow
Sun
1. Right foot
22,7
27,7
28,3
21,3
25,5
28,1
21,4
25,2
28,3
2. Right leg
17,6
36,4
37,3
18,6
35,7
37,0
18,7
35,1
36,6
3. Right thigh
22,5
32,4
33,9
22,6
31,5
34,9
23,2
31,0
33,9
4. Left foot
22,8
26,3
27,6
21,3
24,5
27,4
22,9
26,3
27,7
5. Left leg
21,6
30,3
31,8
21,8
29,3
31,5
22,2
28,6
30,8
6. Left thigh
22,8
33,7
38,2
23,1
31,2
38,6
23,3
31,1
36,1
7. Right hand
22,9
34,2
35,1
21,1
33,5
36,7
22,0
32,0
35,6
8. Right arm
21,2
31,1
33,8
22,1
30,3
36,0
23,6
26,6
33,5
9. Right upper arm
18,0
25,4
35,7
16,6
23,9
34,9
18,6
20,0
31,7
10. Left hand
19,8
34,1
38,6
10,0
32,0
39,1
9,5
30,7
36,3
11. Left arm
23,8
32,2
36,1
23,4
30,7
36,7
23,5
28,8
35,0
12. Left upper arm
21,1
35,2
41,3
20,4
33,2
39,2
21,1
31,1
37,5
13. Head
23,7
34,4
41,1
23,4
27,3
38,4
23,1
24,3
34,3
14. Pelvic region
25,6
32,6
35,1
22,2
32,2
34,8
18,2
31,8
33,8
15. Chest
24,1
33,6
40,7
20,5
29,8
39,2
18,6
29,1
36,2
16. Back
28,9
34,4
35,0
28,6
34,1
35,0
27,7
33,5
34,6
These results are presented in another format in Figure 9. In these diagrams with 1, 2, 3, 4 and 5 are
represented comfort sensations corresponding to too cold, cold but comfortable, neutral, warm but
comfortable, too hot thermal sensations. To each sensation is corresponding different ranges of teq
values specific for each zone. This ranges are presented in ISO 14505-2 [16]. When experimental car
was placed at the sun (session III), left hand, left upper arm, head and chest, have the highest teq due to
the solar radiation “falling” on these parts. At the shadow (session II), after the car was parked in the
sun, teq values of those parts decrease, but remain still greater compared to session I. The principal
reason is higher temperature recorded in air and on the surfaces.
We can see that during the first session majority of the equivalent temperatures achieved shows a
comfortable or cold but comfortable thermal state. There is an exception in case back part due to seat
isolation, this sensation is maintained also in the other two sessions. When experimental vehicle was
placed in the sun, we have tattily different thermal state. Recorded teq value reveals a “to hot” thermal
sensation. This conclusion is similar with Hodder [3]. According to his study, after 30 minute of
exposure to a solar radiation of 600 Wm−2, subjects vote was “hot” on a Thermal Sensation Vote
scale, with the remark, solar lamps was turned on at the beginning of data acquisition. However, for
the third fan velocity position, body parts exposed to sun have a tendency of decreasing if teq values.

The 7th Conference of the Sustainable Solutions for Energy and Environment
IOP Conf. Series: Earth and Environmental Science 664 (2021) 012064
IOP Publishing
doi:10.1088/1755-1315/664/1/012064
7
Equivalent temperatures at the foot and calf do not have a significant changes, and high values
recorded during sessions II and III are based on the high temperature of the air from cabin. Foots and
lower legs are the only parts where the solar radiation does not” fall”. For all the other body parts we
can note great differences from a session to another.
Figure 9 teq votes recorded and the comfort zones conform to the standard ISO 14505-2[16]
4. Conclusion
Solar radiation is a very important factor which affects directly thermal sensation of the human body
parts who are exposed, and indirect the other parts by heating some of the vehicle elements leading to a
high air temperature and a different temperature of the interior element of the car. A secondary effect is
related to the temperature introduced by the ventilation system. Direct solar radiation heats the
dashboard. Conditioned air passes trough the ducts from the dashboard, taking a part of the heat. It may
make the conditioning system more inefficient and lead to a longer time until the comfortable thermal
state is reach.

The 7th Conference of the Sustainable Solutions for Energy and Environment
IOP Conf. Series: Earth and Environmental Science 664 (2021) 012064
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doi:10.1088/1755-1315/664/1/012064
8
Acknowledgement
This work was supported by the grant Innovative system to extend the range of electric vehicles
at improved thermal comfort – XTREME, PN-III-P2-2.1-PED2019-4249 and by a grant of the
Romanian National Authority for Scientific Research, CNCS, UEFISCDI, Project code: PN-III-P2-2.1-
PTE-2019-0394.
References
1. Fanger, P.O., ed. Thermal Comfort-Analysis and Applications in Environmental Engineering. ed. C.D.T.
Press. 1970.
2. Lyons, P. and D. Arasteh, Window Performance for Human Thermal Comfort, in ASHRAE
Winter Meeting, ASHRAE, Editor. 2000, ASHRAE Dallas.
3. Hodder, S.G. and K. Parsons, The effects of solar radiation on thermal comfort. Int J
Biometeorol, 2007. 51: p. 233–250.
4. Vartires, A., A. Dogeanu, and P. Danca, The human thermal comfort evaluation inside the
passenger compartment. Air pollution and climate change, 2015. Energy and Clean
Technologies Conference Proceedings: p. 8.
5. Danca, P. and A. Vartires, Thermal comfort assessment using human subjects; . Machines,
Technologies, Materials International Journal, International Journal for Science, technics and
innovations for the industry, 2015(9/2015): p. 4.
6. Danca, P., A. Vartires, and A. Dogeanu, An Overview of Current Methods for Thermal Comfort
Assessment in Vehicle Cabin. Energy Procedia, 2016. 85: p. 162-169.
7. Bode, F., et al. The influence of the Inlet angle of vehicle air diffuser on the thermal comfort of
passengers. in 2017 International Conference on ENERGY and ENVIRONMENT (CIEM).
2017.
8. Danca, P., et al., On the Possibility of CFD Modeling of the Indoor Environment in a Vehicle.
Energy Procedia, 2017. 112: p. 656-663.
9. Danca, P., et al., CFD simulation of a cabin thermal environment with and without human body
– thermal comfort evaluation. E3S Web Conf., 2018. 32: p. 01018.
10. Horobet, T., et al., Preliminary research on virtual thermal comfort of automobile occupants.
E3S Web Conf., 2018. 32: p. 01022.
11. Danca, P.A., Ventilation strategies for improving the indoor environment quality in vehicles.
2018, University Rennes 1: France. p. 250.
12. Danca, P., et al., Experimental study of thermal comfort in a vehicle cabin during the summer
season. E3S Web Conf., 2019. 111: p. 01048.
13. Dancă, P., et al., Experimental and numerical study of the air distribution inside a car cabin.
E3S Web Conf., 2019. 85: p. 02014.
14. A. DOGEANU, et al., Conception of a real human shaped thermal manikin for comfort
assesment, in PhD & DLA Symposium Pesc, Hungary. 2012.
15. I.Ursu, et al. Advanced Thermal Manikin Prototype with Neuro-fuzzy Control System. in
Proceedings of the 4th International Conference On Building Energy & Environment 2018.
2018. Melborne, Australia: Conference On Building Energy & Environment - COBEE2018,
Melbourne Australia, (1st Feb 2018).
16. 14505-2, I., Ergonomics of the thermal environment - Evaluation of thermal environments in
vehicles - Part 2: Determination of equivalent temperature in ISO 14505-2:2006. 2006.