Integrated Air Conditioning for Automobiles Using Waste Heat

International Journal of Advanced Research in Technology, Engineering and Science (A Bimonthly
Open Access Online Journal) Volume2, Issue2, March‐April, 2015. ISSN: 2349‐7173 (Online).

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Integrated Air Conditioning Unit for
Automobiles
Debi Prasad Sahoo
_________________________________________
Abstract
In this paper, the investigation was made for the utilization
of waste heat in an improvised manner, so that the total
power of the automobile is not going to change and the fuel
efficiency is going to be enhanced. Here the use of vapor
absorption refrigeration system for the air conditioning
system was proposed and analyzed. This system was taken as
it can run on very low grade energy, such as waste heat of
the exhaust gas. The recent trend is to use the vapor
compression refrigeration system, where the principal part is
the compressor, which takes the power from the engine or
from auxiliary power unit and hence the fuel consumption
rate is increased. In the recent global scenario reducing the
fuel consumption is the main research area. The cooling
load of the automobile is estimated about 1.37 TR and the
measured cop value for the proposed model is varied from
0.85 to 1.04.
Here the main problem definition is to design an air
conditioning system which runs on exhaust gas waste heat
by exchanging with the refrigerant R134-a inside a
generator which is the replacement of the compressor in a
vapor absorption refrigeration system. The calculation
related to the design of proposed shell and tube heat
exchanger i.e. the generator for the model is carried out and
the rest design is theoretical study and proposed model to be
implemented in large scale after prototype model testing.
__________________________________________________
Key words: Generator, COP, Exhaust Gas, Waste Energy,
Cooling Load, R134-a, Vapor Compression Refrigeration,
Vapor Absorption Refrigeration.
_________________________________________________
Introduction:
Use of alternate fuel and use of electric vehicle is a major
research topic in recent years. But getting the required power
and torque out put is not up to the mark as of Internal
Combustion Engines.
Almost all the automobiles are using the air conditioning
system now-a-days, which directly increased the fuel
consumption rate as they are using the vapor compression
refrigeration system. So if we can reduce the fuel consumption
from the air conditioning units, then we can reduce the fuel
consumption up to some extent.
In Internal Combustion Engines most of the heat is carried out
by the exhaust gases and that to use of cooling system in an
automobile. All this energy can be used effectively to run
some other systems in an automobile. Here in this model an
effort was given to run an air conditioning system of an
automobile by the use of waste heat from the engine which is
basically called the vapor absorption refrigeration system.
The refrigerant is stored or absorbed inside an absorber and
then it is taken by a centrifugal pump which either runned by
the exhaust gas like a turbo charged pump or driven by engine
power which consumes very less power in comparison to the
compressor and then it is taken inside the generator which is
actually a heat exchanger where the heat exchanged with the
exhaust gas i.e. a shell and tube heat exchanger and then the
high pressure vapor refrigerant is passed to the condenser,
which is actually the air cooled type inside the radiator and
then the high pressure liquid is passed through an expansion
valve, where the pressure is actually going to reduce
drastically and then the low pressure low temperature liquid
passed to the evaporator, where the heat is taken by the
refrigerant from the system and cools the system and
atmospheric air is blown over the evaporator coils and the
cool air is sent inside the cabin space for the purpose of
cooling of compartment. This is the actual process of the
proposed model of the air conditioning system.
The available literatures that are conducted for the auto air
conditioner using waste heat energy are
Robert and Frosch [01] investigated the auto air conditioner
utilizing the waste heat from motor and solar heat.
AlQdah and Sameh Alsaqoor and Al-Jarrah [02] investigated
the auto air conditioner generation using exhaust waste energy
from a diesel engine.
Frank et al [03] designed a heat generating device for an
automobile to use for an absorption air conditioning system
including temperature control.
Alhusein Inayatallah [04] designed a simple aqua –ammonia
absorption system for automobile air conditioning system
using waste heat from a spark ignition engine.

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International Journal of Advanced Research in Technology, Engineering and Science (A Bimonthly Open Access
Online Journal) Volume2, Issue2, March‐April, 2015. ISSN: 2349‐7173 (Online).


Now-a-days HFC-134 a ( R-134 a) is used as the refrigerant in
all new vehicles as it does not contain chlorine and is
environmentally friendly.
HFC-134 a (R-134 a) colorless, odorless, non-flammable and
non corrosive. At normal atmospheric pressure it will boil or
evaporate at -26.9˚C. However boiling point can be changed
by controlling the pressure, it will boil at higher temperature,
when subjected to higher pressure.
Literature Review:
As per Khaled AlQdah, Sameh Alsaqoor, Assem Al-Jarrah
International Journal of Thermal & Environmental
Engineering,Volume 3, No. 2 (2011) 87-93
Analysis and design of an automobile air conditioner was
made by utilizing the available diesel engine exhaust waste
energy to provide the required heat for the generator.
Because automotive air conditioning is one of the most
equipment that heavily uses CFC compounds, and the
leakage of CFCs from such air conditioners affect the
environment, the absorption cycle was found to be an ideal
option. Cooling load for the automobile has been estimated
and found to be within acceptable ranges which are about
1.37 TR. The reported results show that the COP values
directly proportional with increasing generator and
evaporator temperatures. Measured COP values of the
proposed model varied between 0.85 and 1.04.
The generator was designed and fabricated for optimal
performance and could be rapidly transfer to the
industrial applications, The system was found to be
applicable and ready to produce the required conditioning
effect without any additional load to the engine The
proposed system decreases vehicle operating costs and
environmental pollution caused by the heating system as
well as causing a lower global warming. Simple
experiments were carried out to examine the performance
of the generator heat shown the benefit of exhaust gases as
an alternative heating source.
As per Christy V Vazhappilly, Trijo Tharayil, A.P.Nagarajan
International Journal of Engineering Research and
Application, Vol. 3, Issue 5, Sep-Oct 2013, pp.63-67
A breadboard prototype of an absorption system for
refrigeration using heat from the exhaust-gases is to be
designed, built and tested. In the commercial vapour
absorption refrigeration system a heating coil generator
system has been employed to vaporize the ammonia
refrigerant. In the present work, the heating coil generator
system has been replaced by the frame plate type heat
exchanger. The exhaust gases from the IC engine have been
utilized to vaporize the ammonia refrigerant. The available
heat in the exhaust gases has to be estimated based on actual
I.C-Engine driving cycles. The frame plate type heat exchanger
has to be modeled and flow analysis inside the heat exchanger
has to be analyzed. In addition, the recoverable energy of the
exhaust gases is to be analyzed for representative Internal
Combustion Engine.
As per M. Joseph Stalin, S. Mathana Krishnan, G. Vinoth
Kumar,International Journal of Advances in Engineering &
Technology, July 2012.
As the energy demand in our day to day life escalates
significantly, there are plenty of energies are shuffled in the
universe. Energies are put in an order of low grade and high
grade energies. The regeneration of low grade energy into
some beneficial work is a fantastic job. One such low
grade energy is heat energy. So it is imperative that a
significant and concrete effort should be taken for using heat
energy through waste heat recovery. This paper concentrates
on the theoretical analysis of production of hot water and
reduction of LPG gas using air conditioner waste heat. Now a
day, Air Conditioner is a banal device which occupies most of
our condominium for our comforts. An attempt has been
taken to recover waste heat rejected by the 1 TR air
conditioning systems. For this water cooled condenser is



exerted and the water is promulgated by the pump until our
desired temperature is acquired. Then the hot water is
accumulated in insulated tank for our use. The result of the
paper shows that the temperature of hot water, time required for
attaining that temperature for the necessary volume of water
and the reduction of LPG gas by using hot water is also
confabulated. Factors like supply and demand, condenser coil
design are pondered and theoretically calculated and the
corresponding graphs are drawn. Finally this could be the
surrogate for water heater and it fulfils all the applications of
Hot water.
As per Gogineni. Prudhvi, Gada.Vinay, G.Suresh Babu,
International Journal of Engineering and Advanced
Technology (IJEAT), ISSN: 2249 – 8958, Volume-2, Issue-4,
April 2013
Most internal combustion engines are fluid cooled using
either air (a gaseous fluid) or a liquid coolant run through a
heat exchanger (radiator) cooled by air.
In air cooling system, heat is carried away by the air
flowing over and around the cylinder. Here fins are cast on
the cylinder head and cylinder barrel which provide
additional conductive and radiating surface. In w a t e r -
cooling system of c o o l i n g engines, the cylinder walls
and heads are provided with jacket through which the
cooling liquid can circulate.
An internal combustion engine produces power by burning
fuel within the cylinders; therefore, it is often referred to as
a "heat engine." However, only about25% of the heat is
converted to useful power. What happens to the remaining
75 percent? Thirty to thirty five percent of the heat
produced in the combustion chambers by the burning fuel
are dissipated by the cooling system along with the
lubrication and fuel systems. Forty to forty- five percent of
the heat produced passes out with the exhaust gases. If this
heat were not removed quickly, overheating and
extensive damage would result. Valves would burn and warp,
lubricating oil would break down, pistons and bearing
would overheat and seize, and the engine would soon stop.
The necessity for cooling may be emphasized by considering
the total heat developed by an ordinary six-cylinder engine.
As per I. Horuz, Journal of Energy Engineering / August
The refrigeration units currently used in road transport
vehicles are pre- dominantly of the vapor compression
refrigeration (VCR) type, in which the vapor compressor
requires an input of energy in the form of work. In small
systems, the compressor work input can be obtained via
a belt drive from the main propulsion engine, while in
large systems the compressor is normally driven by a
dedicated internal combustion (IC) engine
The efficiency of such an IC engine is 35 – 40%, meaning
that only about one-third of the energy in the fuel used
is converted to useful work. This means that the
remaining 60 – 65% of the primary energy is rejected to
the environment by cooling water/lubricant losses of
approximately 28 – 30%, exhaust gas losses of
approximately 30 – 32%, and the remainder by radiation,
etc. The same is true for the considerably more
powerful main propulsion engines of the road vehicle.
In the vapor absorption refrigeration (VAR) system, a
physicochemical process replaces the mechanical process
of the VCR system by using energy in the form of heat
rather than mechanical work. The main advantages of
this system lie in the possibility of using the energy in
hot waste gases.
This study investigates the performance of a VAR unit
utilizing the waste heat in the exhaust gases from a
turbocharged diesel engine that is used to represent the
main propulsion unit of a road vehicle. If such a system
could be used to provide refrigeration, there would be no
need for the IC engine and the compressor of the VCR
system. There would also be a corresponding reduction in
exhaust gas pollution.



Design and analysis of the model:
The generator is used to produce the same effect that of the
compressor in the vapor compression refrigeration system. It
is used to extract and transfer maximum amount of heat from
the exhaust gases and is used to evaporate the refrigerant R-
134-a.
It is designed to have capacity of 4.6 KW with temperature
around 90˚ C, pressure 31 bar.
Assuming the overall heat transfer coefficient, mass flow rate
and specific heat are constant and there is no loss of heat to
the atmosphere. The external heat transfer area required can
be calculated.
The external heat transfer area is calculated by [17]
Q U A ∆LMTD
A
Q
U ∆LMTD
Where,
U = Overall heat transfer co-efficient, which can be
calculated, neglecting the fouling factor by [11]
1
U

1
hi

ro
ri

1
ho
ln
ro
ri

ro
Ks
Where,
hi = inside heat transfer co-efficient
ho = outside heat transfer co-efficient
ri= inside diameter
ro= outside diameter
Ks = thermal conductivity for steel
Q = heat capacity of the generator
ΔLMTD = Log mean temperature difference, which can be
calculated by [18]
∆LMTD θm
θ1‐θ2
ln
θ1
θ2
Where,
θ1 &  θ
TEi = temperature of exhaust gas at inlet
TEo = temperature of exhaust gas at outlet
TRi = temperature of refrigerant at inlet
TRo = temperature of refrigerant at outlet
∆LMTD θm
240° 30° 200° 90°
ln
240° 30°
200° 90°
154.64
For finding the inside heat transfer coefficient, Nusselt
number can be used,

The flow inside the generator will be two-phase flow. This
equation can be used for finding out the Nusselt number by
[2]
0.06
.

.
.
From [2,18] it was found to be
1246.549
25.4763
For flow outside tubes , the following equation can be used
from [2,18]
   .
.
Where,
C & n are constant depending upon Re i.e. Reynold’s Number
Kg = thermal conductivity of exhaust gas
By using the procedure from [17,19], we can obtain
Fig: - Schematic Diagram for Design of Tubes
2 & 1.5
   0.5 .
If 2 , then

Where,
Vg = velocity of exhaust gases through generator
V∞ = velocity of the exhaust gases while entering the
generator
D = outer diameter of the tube



Let’s consider the following conditions for the purpose of the
calculation and finding out the area required for the generator.
Generator material = steel
Tube inner diameter = 15 mm
Tube outer diameter = 19 mm = D
2 38 &
1.5 28.5
   0.5 .
34.2
2   2 34.2 19 30.4
38 19 19
2
Then as per [2]
V∞ is 7 m /sec and Vg = 14 m/sec
0.35
.
0.370
Pr∞ = Prandtls number at fluid temperature = 0.703
Prs = Prandtls number at surface temperature = 0.705
N=0.6 and C = 0.370
At T = 237 ˚ C, Pr = 0.69
From Silva and Costa [20], the properties for the exhaust gas
can be found to be
ρg = 0.694 kg/m3
μg = 2.74 x 10-5
N S/ m2
Kg = 0.037915 W/m ˚C
Vg = 14 m/sec
By calculation using the formulas from []
Reynolds number = Re =

0.694 14   0.019
2.74 10
6737.37
Therefore; the Nusselt number will be found out using
NU 0.37 6737.370.6
0.690.36

0.703
0.705
0.25
64.11
now, 127.93
now,
Ksteel = 42 W/ m2
˚C, Qg = 4.6 kW, ho = 127.93 W/ m2
˚C, hi =
25.4763 k W/ m2
˚C
Substituting the values in the equation of U, we will get
1
U

1
25.4763 10

0.019
0.015

1
127.93
ln
0.019
0.015

0.019
42
126.37 ⁄
Therefore.
A
4.6 10
126.37 154.64
0.235
So the area required is 0.235 m2
Some results based on the RPM and Exhaust temperature and
Qg , given below
Effect of diesel engine speed on the exhaust gas temperature
Effect of diesel engine speed on the exhaust heat generation



Effect of diesel engine exhaust gas temperature on heat
generation
Conclusion:
Here in this paper a sincere trial was made to find out the
generator area for the vapor absorption refrigeration system
using waste heat of exhaust gas of the diesel engine. The
waste heat energy available in exhaust gas is directly
proportional to the engine speed and exhaust gas flow rate.
The study can be implemented for the mass production of this
type of air conditioning system to be runned by exhaust gas
heat of the automobile.
Reference:
[1] Robert A. Frosch. Automotive Absorption Air
Conditioner Utilizing Solar And Motor Waste Heat, United
States Patent 1980; 4:307,575
[2] Khaled AlQdah, Sameh Alsaqoor, Assem Al-Jarrah
International Journal of Thermal & Environmental
Engineering,Volume 3, No. 2 (2011) 87-93
[3] Frank F, Nekola, Trenton, Fla. Heat Generator for Use
with an Absorption Air Conditioning System For
Automobiles, United State Paten1990; 5: 49-82
[4] Alhusein M, Inayatullah G. Automobile Vapor
Absorption Air Conditioning System. Journal of Mu'tah for
Research and studies 1994; 9: 251-269.
[5] Gui-ping Lin Xiu-gan Yuan Zhi-guang Mei.The
Feasibility Study of the Waste Heat Air- Conditioning
System for Automobile. Journal of Thermal Scienc1986; 3
[6] Al-Aqeeli N, Gandhidasan P. The use of an open
cycle absorption system in automobile as an alternative to
CFC. Proceeding the 6th Saudi Engineering Conference,
KFUPM, Dhahran, December 2002.
[7] Shah Alam. Proposed model for utilizing exhaust heat
to run automobile air-conditioner. Proceeding of the
International Conference on Sustainable Energy and
Environment. Bangkok, Thailand, November, 2006
[8] Viji. V., N. Ashok Kumar, Theoretical Design of an
Automobile Adsorption Air Conditioner, 10th
National
Conference on Technological Trends (NCTT09) 6-7 Nov
2009.
[9] R.J. Yadav, R.S. Verma, Effective Utilization Waste
from Diesel Genset to Run Air-Conditioning Plant.
[10] I. Horuz. Vapor Absorption Refrigeration in Road
Transport Vehicle. Journal of Energy Engineering. Vol-
125, 2 August 1999
[11] Arora, C.P: Refrigeration and Air Conditioning.
Tata McGraw-Hill: New Delhi ,1981.
[12] Auto Air Conditioning, A SHRAE Applications
Handbook , 1995; 87-89
[13] Ruth, D. W. Simulation and Modeling of Automobile
Comfort Cooling Requirements. ASHRAE Journal 1975;
5-53
[14] Multerer B, Burton R. L. Alternative Technologies for
Automobile Air Conditioning, July 1991
[15] Bejan, A: Advanced Engineering Thermodynamics.
John Wiley and Sons, :NewYork, 1988
[16] Chapman, A.J: Heat Transfer.4th
Ed, Collier-
Macmillan Co, 1984
[17] Ibrahim O.M., Klein S.A. Thermodynamic Properties
of Ammonia-Water Mixtures. ASHRAE Transactions from
1993 Winter Meeting, Chicago, lllinois, 1495-99:1495-
1502. 1993
[18] Rajput, R.K., Heat and Mass Transfer, S. Chand, New
Delhi, 2011
[19] Davis E.J, David M.M. Two-phase gas liquid
convection heat transfer, 1 and EC fundamentals , 1964;3:
111-118
[20] Silva. C.M, Costa . M and. Farias. Evaluation of SI
engine exhaust gas emissions upstream and downstream of
the catalytic converter. Journal of Energy Conversion and
Management 2006; 47 : 2811–2828
Address of Author:
Debi Prasad Sahoo, Lecturer in Mechanical Engineering,
Government College of Engineering, Keonjhar.

Integrated Air Conditioning for Automobiles Using Waste Heat

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