Thermal analysis of an open window bus used & Effect of design
modification in bus on thermal comfort to passengers.
A Project Report
submitted in the partial fulfillment of the requirements
for the award of the degree of
Bachelors of Technology
In
Mechanical Engineering
By
Vinayak Gupta
200447
Vaibhav Tonk
200445
Pawan Pant
200426
Rudraksh Dabral
200432
Under the guidance of
Dr Pawan Kumar Pant
Assistant professor
Department of mechanical engineering
DEPARTMENT OF MECHANICAL ENGINEERING
G. B. PANT INSTITUTE OF ENGINEERING AND TECHNOLOGY,
PAURI GARHWAL UTTARAKHAND, 246194
JUNE 2022
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DEPARTMENT OF MECHANICAL ENGINEERING G.B.P.I.E.T.
PAURI GARHWAL
GOVIND BALLABH PANT INSTITUTE OF
ENGINEERING AND TECHNOLOGY PAURI
(GARHWAL)
CERTIFICATE
Dated:……/………/………….
We hereby certify that the work which is being presented in this report entitled
“Thermal analysis of an open window bus used & Effect of design modification in bus on
thermal comfort to passengers.”, in partial fulfillment of the requirements for the award of
the Degree of Bachelor of Technology, is an authentic record of work by us. The matter
embodied in this work has not been submitted to any other University/ Institute for the award
of any degree.
(Vinayak Gupta)
(Vaibhav Tonk)
(Pawan Pant)
(Rudraksh Dabral)
This is to certify that the above statement made by the above students is correct to the best of
my knowledge.
(Dr Pawan Kumar Pant)
The Bachelor of Technology (B.Tech) viva voice examination of the above students
have been held on ...…./.……/…………..
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DEPARTMENT OF MECHANICAL ENGINEERING G.B.P.I.E.T.
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ACKNOWLEDGEMENT
We express aur deep sense of gratitude and reverence to Dr Pawan Kumar Pant, our guide,
for his continuous and valuable suggestions at all stages during the initial course of this work.
His helpful and placid nature give us the real pleasure of working with him. He encouraged and
motivated us during the making of this project.
Special thanks to Dr. Ashutosh Gupta, Head of the Department, Mechanical Engineering
for his valuable corporation, encouragement, and sport
Last but not the least we are thankful to one and all who helped us in making this project
VINAYAK GUPTA (200447)
(……………………………)
VAIBHAV TONK (200445)
(……………………………)
PAWAN PANT (200426)
(……………………………)
RUDRAKSH DABRAL (200432)
(……………………………)
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DEPARTMENT OF MECHANICAL ENGINEERING G.B.P.I.E.T.
PAURI GARHWAL
ABSTRACT
Open Window buses without Air-conditioning are a major mode of urban and intercity
transport in most countries. High occupancy combined with hot and humid makes travel
uncomfortable. In this study the temperature changes that occur through the bus has been
studied that could be the basis for low cost and economically budget friendly methods of
increasing passenger comfort. By using the actual bus dimensions that travels through the area
of Delhi during high summer seasons and in simulations we visualize the temperature changes
for a bus travelling to Delhi with the surrounding temperature of 38°C. The temperatures at
Delhi occurs during the month of April or late May or sometimes in early June. In simulation
we took the velocity conditions of 40 km/hr. numerical simulations were performed at Actual
Reynolds number. The Heat comes inside from the Front and Rear Windows.
For the Temperature analysis, we have found the results of bus through making contours at
different planes. We also make the results at each passenger seats and extracts the result of their
Total Temperature, Total Surface Heat Flux, Surface Heat Coefficient and their individual
Nusselt Numbers. Then at last we will be going to do some design modifications so that the
travelling in Delhi in humid regions becomes more comfortable and cheaper to buy.
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DEPARTMENT OF MECHANICAL ENGINEERING G.B.P.I.E.T.
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Contents
Description
Page No.
CERTIFICATE
ii
ACKNOWLEDGEMENT
iii
ABSTRACT
iv
LIST OF FIGURES
v
Chapter 1: Introduction and Literature Survey
1.1 Introduction
01
1.2 Literature Survey
02
1.3 Conclusion of Literature Survey
04
1.4 Objectives
04
Chapter 2: Experimental work
2.1 Geometrical Details
05
2.2 Passenger Nomenclature
06
2.3 Computational Domain and Boundary Conditions
06
2.4 Meshing
07
Chapter 3: Results and discussion
3.1 Thermal Analysis
08
3.2 Total Temperature at each seat
11
3.3 Surface heat transfer coefficient at each seat
12
3.4 Surface Nusselt Number at each seat
12
References
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DEPARTMENT OF MECHANICAL ENGINEERING G.B.P.I.E.T.
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LIST OF FIGURES
Description
Page No.
1.1 Picture of a typical non-airconditioned bus with open windows
01
2.1 Geometric Details
05
2.2 Passenger Nomenclature
06
2.3 Computational Domain
06
2.4 Meshing of the domain
07
3.1 Plane XZ passes through middle of face
08
3.2 Plane XZ passes through middle of the passenger
08
3.3 Plane XZ passes through middle of Passenger’s Seat
09
3.4 Plane XZ passes through Lower position of seat
10
3.5 Plane YZ on driver, row 2, row 4, row 6, row 8 and end passengers
10
3.6 Total Temperature at each seat
11
3.7 Surface Heat Transfer Coefficient at each seat
12
3.8 Surface Nusselt Number at each seat
12
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DEPARTMENT OF MECHANICAL ENGINEERING G.B.P.I.E.T.
PAURI GARHWAL
CHAPTER 1
INTRODUCTION
1.1 INTRODUCTION
The bus is a major mode of public transport in most countries of the world, especially in
urban areas. On per passenger per kilometre basis, the fuel economy is better and
emissions are lower than either the automobile or motorized two-wheelers. A picture of
a typical urban bus in Delhi is seen in figure 1.1.
Figure 1.1 Picture of a typical non-airconditioned bus with open windows.
It consists of a box-shaped passenger compartment mounted on a chassis powered by a
compressed natural gas (CNG) or alternately diesel fuelled engine. The compartment has
two passenger doors (figure 1), a driver’s door and an emergency door. A continuous
row of windows is provided on both sides, that includes the doors in closed position also.
While in motion, the passenger door(s) may or may not be fully open. Individual
passengers adjust the window openings to suit their needs. Some buses have one or two
adjustable openings on the roof ostensibly for augmenting air circulation (figure 1).
Almost all buses whether owned/operated by private or public enterprises, are not
airconditioned, primarily to keep fares low. Consequently, the windows and doors are
kept open so that air circulation induced by the motion of the bus will result in better
comfort.
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DEPARTMENT OF MECHANICAL ENGINEERING G.B.P.I.E.T.
PAURI GARHWAL
Although viewed as essential, bus services and buses are generally looked down upon
for a variety of reasons. Passenger amenities in buses, such as seats and standing space,
are inadequate and uncomfortable; they are noisy and vibrate. The climate of large
regions in India, as also elsewhere in the world, is characterized by high ambient
temperatures as well as high humidity for many months in a year. This aspect coupled
with high passenger occupancy, also termed packing density, results in poor comfort
levels inside the bus as quantified by air temperature, humidity and velocity. Window
seats are at a premium and some passengers prefer traveling on the foot board or standing
in the open doorway. This aspect is one of the major contributors to the perception of bus
travel as uncomfortable.
1.2 LITERATURE SURVEY
1.2.1 Closed Window Bus
❑ M. C.G. Silva et. al (1997) found that the measured values of velocity and air
temperature in most of the space corresponding to the occupied zone by a seated
passenger were found to be within the ranges prescribed by thermal comfort
standards for summer conditions.
❑ K.W. Mui et. al (2005) found that the in-bus environmental quality varied
depending on the ambient environment by natural ventilation as well as the
induced infiltration through windows. As the buses are traveling in the green
country-side environment, the in-bus environment would be more pleasant with
the induced fresh air
❑ Ka Wing Shek (2007) found that an in-bus comfortable commuting environment
was examined and modeled including passengers' sensation and satisfaction
towards thermal comfort and air quality. Both physical parameters measurement
and passenger surveys were conducted.
❑ Tzu-Ping Lin (2009) found that in the investigation of behaviors frequently
adopted by passengers for thermal adaptation, it was found that short haul
passengers tend to choose behavior’s, such as adjustment of air outlets, that can
immediately relieve the thermal discomfort resulting from sudden temperature
changes when moving from vehicles to outdoors. Long-haul passengers prefer to
draw the drapes to eliminate the discomfort resulting from exposure to solar
radiation on long-haul journeys.
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DEPARTMENT OF MECHANICAL ENGINEERING G.B.P.I.E.T.
PAURI GARHWAL
❑ Shengwei Zhu (2009) found that based on both our numerical and field
investigation on the bus environment, there is a need to further study and identify
ventilation strategies and alternate air distribution methods in order to improve
the ventilation efficiency in this important microenvironment.
❑ Kai Zhang (2014) found that the mean age of total samples is 27.94. It can be
seen that with the decrease of mean age or mean health, people tend to yield worse
bus comfort. The numbers in the top of Fig. 3 told us the means and standard
deviations of OBC (S) measured by male and female.
❑ Hans WigÖ (2016) found that the difference in MTV scores between subjects in
the two velocity conditions, measured after the last high velocity pulse, did follow
the expected decay over time. Ten minutes after the last high velocity pulse the
difference in MTV scores was not significant, this suggests that the time between
the high velocity pulses should be 10 to 15 minutes at those temperature and air
speed conditions.
❑ Mihaela Simion (2016) found that the thermal comfort inside the vehicle differs
significantly from buildings. The air temperature is correlated to a greater extent
with relative air humidity, and they influence the thermal comfort of the
passenger.
❑ Şaban Ünal (2017) found that the air conditioning system for a bus should be
selected considering a number of parameters, including passenger capacity, local
climatic conditions, and fuel consumption. It is possible to determine whether a
selected air conditioning system provides desired performance through testing.
This study examines how to verify experimentally whether a bus air conditioning
system meets design and comfort requirements.
❑ Fei Li et. al (2017) found that the proposed CFD-based method assigned the
actual relative pressures to a certain percentage of boundary cells according to the
effective area ratio of the gap boundaries. It was a trade-off between the computer
capacity and basic need for describing geometry. This method can predict the
airflow rate from the window gap infiltration and the results agree well with
experimental data.
❑ K.B. Velt (2017) found that that passengers in a city bus perceived the
temperature of 22.5 C in a city bus as ‘slightly warm’ during a November ride
with ambient temperatures of about 13.4 C. A simple regression model indicated
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DEPARTMENT OF MECHANICAL ENGINEERING G.B.P.I.E.T.
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an optimal bus temperature of 20.9 C to achieve a status of neutral thermal
sensation.
❑ Xiaoxuan Zhu (2018) found that reducing or adding to the air output did not
change the PM10 concentration but did shorten the time taken to reach a steady
state. However, reducing or adding to the air output did lessen the perception of
the airflow for passengers and reduced the temperature in the cabin.
1.2.2
Open Window Bus
❑ S R Kale et. al (2007) found that the studies show that flow inside a bus with
open windows is complex. Outside air enters the bus from the rear windows,
moves forward relative to the bus at about 1/10th the bus speed and exits from
the front windows
❑ M.M. Yelmule and S.R. Kale (2009) found that the combination of open
windows, an open front slot, open slots on the roof at middle and rear, and open
slots on the rear side at top and middle, result in the significant drag reduction (up
to 29%) and, simultaneously enhance through flow (up to 65%).
❑ Pant et. al (2023) found that Pant et al already design modification introduce and
enhance the velocity at the face. But no thermal analysis on an open window bus.
1.3 CONCLUSION OF LITERATURE SURVEY
After analysing the key findings from literature survey, it is concluded that Pant et. al has
done velocity flow analysis on the open window bus but no thermal analysis has been
done on same flow conditions. We also find major differences between Closed vehicle
and Open window vehicles based on their visualization and numerical simulations. We
also get to know that the flow inside an open window bus is complex.
1.4 OBJECTIVES
1. Thermal analysis of an open window bus used by pant et.al
2. To Propose design modification to enhance Thermal comfort on passengers.
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DEPARTMENT OF MECHANICAL ENGINEERING G.B.P.I.E.T.
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CHAPTER 2
EXPERIMENTAL WORK
2.1 GEOMETRIC DETAILS
The outer frame of bus is 10.5m×2.5m×1.9m (L×W×H) in dimensions. This bus contains
8 windows including 2 smaller size windows from the left side and 6 windows from the
right side of the bus (total of 14 windows). The LW signifies the Left Window and RW
signifies the Right Window. The gap between RW5 and RW6 and ahead of RW1 is the
position for the doorways. There are two doorways to enter the bus. The doorways are
not shown because the bus is in moving condition and in this case generally the doorways
are closed or no flow of velocity occurs. The seating capacity for this bus is 59 adding
the seat for the Driver. The seating arrangement and geometric structure for the bus is
shown in figure 2.1. The Dimensions of windows, seats, doors, the outer dimensions,
inner dimensions, etc all are taken according to the actual bus which travels to Delhi.
Figure 2.1 Geometrical Details
.
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DEPARTMENT OF MECHANICAL ENGINEERING G.B.P.I.E.T.
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2.2 PASSENGER NOMENCLATURE
Figure 2.2 Passenger Nomenclature
The figure 2.2 shows the arrangement of seats which is seen in this bus. This seating
arrangement is taken according to the actual bus which is shown in figure 2.1. Along the
column, the seating number changes and along the row, the Seating alphabet changes.
By using this allocation of seats, we have found out the results at each seat.
2.3 COMPUTATIONAL DOMAIN AND BOUNDARY CONDITION
We have made a domain which the bus is 5.26 H times away from velocity inlet and
13.37 H times ahead of pressure outlet. The domain is 8.42 H times wide and 4.21 H
times high. The ‘H’ signifies the height of the bus.
Figure 2.3 Computational Domain
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The Boundaries as shown in figure 4 is labelled as
Velocity Inlet: It is the boundary at which the Velocity of fluid enters the domain. The
fluid we have chosen is air with a speed of 40 km/hr
Pressure Outlet: this is the boundary at which the fluid exits.
Top wall: This boundary is at the top of the domain. It is no slip wall.
Side wall: These walls are at the sides of the domain. These are also no slip walls.
Ground: this is taken as a ground for the bus and it is the bottom of the domain. This is
also a no slip wall.
Windows/ Slots: At these voids the air enters inside the bus.
Bus Surface: These are the outer structure of the bus. This is also a no slip wall.
No slip walls are the Boundaries at which the velocity of the fluid at the wall is zero. The
fluid particles in direct contact with the wall do not slide or move relative to the wall.
They are stationary. This condition is essential for understanding and modeling the
behavior of the fluids near solid surfaces.
2.4 MESHING OF THE DOMAIN
Meshing is the process of analyzing the domain region according to our need. For this
domain, we have implemented hex cone meshing. Hex cone meshing refers to a specific
method of generating hexahedral element within three-dimensional mesh for
computational domain. We require three refinement zones to generate mesh in the entire
domain. The cell concentration inside the bus and wake region are dense because we
want to get more accurate results in these areas. After the meshing is done, we get the
result like as seen in figure 5.
Figure 2.4 Meshing of the Domain
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CHAPTER 3
RESULTS AND DISCUSSIONS
3.1 THERMAL ANALYSIS
3.1.1 Case 1: when plane XZ is at middle of the face.
Figure 3.1 Plane XZ passes through the middle of the face.
This result is made by using Ansys Fluent (CFD). We made a XZ plane and using
coordinates we lifted the plane from origin to middle of the face of the passenger. When
we observe the plane, we find that from driver seats to 3rd row passengers, the
Temperature range is between 315K to 318K. While the middle row passenger and end
passengers feels the same way around as driver and front row passengers. But for area
where middle passengers and end passengers where there is a gap between two rows the
temperature range is between 313K to 310K.
3.1.2 Case 2: When Plane XZ is at the Middle of the passenger.
Figure 3.2 When Plane XZ passes through the middle of Passenger.
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For this case, the plane is XZ plane and using the coordinates we lifted the plane from
origin to middle of the seating passenger. In this case, we observe that the region around
each passenger has Temperature range between 315K to 318K. Front row passenger
might feel little more uncomfortable situation as temperature is at 320K or above in
nearby area. For the end row passengers where there is a gap between two rows the
temperature range is between 310K to 313K.
3.1.3 Case 3: When plane XZ passes through middle of passenger seat.
Figure 3.3 When plane XZ is at the middle of passenger seat.
For this case, the XZ plane is made and placed it from origin to the middle of passenger’s
seat. When we observe this case, we get to know that the front row passengers sitting
may feel more uncomfortable as the temperature ranges can move above 320K. The end
passenger sitting can feel less temperature as compared to front region passengers. The
range is between 315 to 318 K. This result also shows that this position is the most
uncomfortable position for the passengers to travel with respect to temperature.
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3.1.4 Case 4: When Plane XZ is at the lower position of seats.
Figure 3.4. When plane XZ is at the lower position of seats.
In this case, XZ plane is made and using the coordinates we placed the plane at the
positions of the legs. we observe that almost all the passenger feels the same temperature
conditions at the lower part of the body i.e., all passenger feels around the temperature
range between 315K to 318K.
3.1.5 Case 5: When Plane YZ is at Driver, row 2, row 4, row 6, row 8 and End
Passengers.
Figure 3.5 When Plane YZ is at Driver, row 2, row 4, row 6, row 8, End Passengers.
For this case, we make 6 YZ planes and placed them leaving one row of passengers.
This placing is done so that the calculations can become easier. We observe that the
driver feels the temperature range between 315K to 318K. Row 2 passengers feels the
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same heat as the driver feels but the gaps between the seats has less temperature range.
In case of row 4 passengers, they feel more comfortable than the driver and the row 2
passengers with temperature range between 313K to 315K. Row 6 and 8 passengers
feels less temperature than row passenger 4 with a temperature range between 310K to
313K. At last, the end passengers feel most comfort than any other passengers.
3.2 TOTAL TEMPERATURE AT EACH SEAT
Figure 3.6 Total temperature at each seat in degree (°C)
This contour is made by the help of using Tec plot software. Firstly, we found all the
temperatures by making the clip plane at the front, rear, left, right and top and find its
total temperature at each plane at their faces. The reason for making plane in the face as
it is the most sensitive part of the body. The body feels most uncomforted when the heat
strikes the face. Then we average all the results of the total temperature at each plane
and found the result for each seat. Then the final result is shown in figure 3.6.
After getting results for every seat, we observed that the driver seat felt the temperature
around 41°C. For the front row passengers, the temperature is the same as we see in case
of driver. For row 2 passengers, the temperature is little more as compared to front row
passengers. For the 3rd row passengers, the temperature feels little less than the row 2
passengers. Now after row 3, the temperature slightly decreases till the end. But the
average temperature at each row will be the same between 40-41°C. There is no much
difference in the temperature while comparing the seats.
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3.3 SURFACE HEAT TRANSFER COEFFICIENT AT EACH SEAT
Figure 3.7 Surface heat transfer coefficient at each seat (W/m2K).
We used the same method for finding the results of the surface heat transfer at each seat
as we have done on total temperature at each seat. After getting the result, we observe
that the middle row and end row passengers which are sitting near the windows feels
most heat as compared to the passenger away from the windows. We also find that the
passengers sitting at the front seats feels less heat as compared to middle row seated
passenger. The Driver also feels same amount of heat as front row passenger feels. Figure
3.8 shows the results for surface heat transfer coefficient at each seat.
3.3 SURFACE NUSSELT NUMBER AT EACH SEAT
Figure 3.8 Surface Nusselt number at each seat
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DEPARTMENT OF MECHANICAL ENGINEERING G.B.P.I.E.T.
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We used the same method for finding the results of the surface Nusselt Number at each
seat as we have done on total temperature at each seat. When we see the results, we get
to know that the Nusselt Number at each seat depicts the same results as for surface heat
transfer coefficient. the middle row and end row passengers which are sitting near the
windows feels most heat as compared to the passenger away from the windows. We also
find that the passengers sitting at the front seats feels less heat as compared to middle
row seated passenger. The Driver also feels same amount of heat as front row passenger
feels. Figure 3.9 shows the results for surface Nusselt Number at each seat.
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REFERENCES
1. Yelmule, M.M., Kale, S.R. and Veeravali, S.V., “Aerodynamics of a bus with Open Windows.”,
Int. J. Heavy Vehicles Systems, Vol. 16, No. 4 (2009).
2. Kale S.R., Veeravalli S.V., Punekar H.D., Yelmule M.M., “Air flow through a nonairconditioned bus with open windows”, Sãdhanã Vol. 32, part 4, (August 2007), pp. 347-363.
3. Conceição E.Z.E, Silva M.C.G, Viegas D.X, “Airflow around a passenger seated in a bus”,
HVAC&R Research Vol. 3, No. 4, (October 1997).
4. Mui K.W, Shek K.W, “Influence of in-tunnel environment to in-bus air quality and thermal
condition in Hong Kong.”, ELSEVIER (2005).
5. Chan Wai Tin, Shek Ka Wing, “Combined comfort model of thermal comfort and air quality on
buses in Hong Kong.”, ELSEVIER (2007).
6. Lin Tzu-Ping, Hwang Ruey-Lung, Huang Kuo- Tsang, Sun Chen-Yi, Huang Ying-Che,
“Passenger Thermal Perceptions, thermal comfort requirements, and adaptations in short-and
long-haul vehicles.”, Springer (2009).
7. Spengler John, Zhu Shengwei, Demokritou Philip, “Experimental and numerical investigation of
micro-environmental conditions in public transportation buses.”, ELSEVIER (2010).
8. Zhang Fangzhou, Zhou Kan, Zhang Kai, “Evaluating bus transit performance of Chinese cities”.,
ELSEVIER (2014).
9. Oz H. Ridvan, Pala Uzeyir, “An Investigation comfort inside a bus during heating period within
a climatic chamber.”, ELSEVIER (2015)
10. Wigö Hans, “Effects of Intermittent Air Velocity on Thermal and draught perception during
transient conditions.”, International Journal of Ventilation Vol.7, No.1 (2016).
11. Unguresan Paula, Socaciu Lavinia, Simion Mihaela, “Factors which influence the thermal
comfort inside of vehicles.”, ELSEVIER (2016).
12. Ünal Şaban, “An Experimental study on a bus Air Conditioner to determine its conformity to
design and comfort conditions.”, Yildiz Technical University Press Vol. 3 No.1 pp 10891101(2017).
13. Velt K.B, Daanen H.A.M, “Optimal Bus Temperature for Thermal Comfort during a cool day.”,
ELSEVIER (2017).
14. Zhu Xiaoxuan, Lei Li, Wang Xingshen, Zhang Yinghui, “Air Quality and passenger comfort in
an air-conditioned bus micro-environment.”, Springer (2018).
15. Zhu Xiaoxuan, Lei Li, Han Jitian, Wang Peng, Liang Fushun, Wang Xingshen, “Passenger
comfort and ozone pollution exposure in an air-conditioned bus microenvironment.”, Springer
(2020).
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16. Mathal Varghese, Das Asimanshu, Bailey Jeffrey.A, Breuer Kenneth, “Airflows inside
passenger cars and implications for airborne disease transmission.” Science Advances (2021).
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