Transcript INDUSTRY DEFINED PROBLEM AUTOMATIC …

DEPARTMENT OF MECHANICAL
ENGINEERING
PROJECT PRESENTATION
REFRIGERATION USING WASTE HEAT
IN CARS
KAVINESH.E
DHAMOTHARAN.D
MANOBALAN.A
JOSAN PRAJAI PAUL.P
GUIDE: NALLASAMY.P
( LECTURER PSG COLL OF TECH,CBE)
ABSTRACT
Quite often, people’s own desire for comfort
increases the burden on environment, the use of
private cars and air conditioning units in them
are an example of this. These add comfort to the
people, increasing the burden on environment. In
this project we have tried to give positive life
cycle environmental impact by reducing the
emission of exhaust gas. This reduction is
achieved using vapor absorption cycle instead of
vapor compression cycle and refrigerant motors
instead of electric motors that is normally being
used.
LITERATURE SURVEY:
At present vapor compression
system is widely being used in
automobiles for refrigeration
purpose. The major
disadvantages of this system
are
•Compressor runs by the
power from engine
crankshaft, thus reducing the
efficiency of the engine
•Use of refrigerant increases
the cost and has
environmental impact
•Use of electric motors for
fans and pumps increases the
load on the engine
ENERGY LOSSES IN A VECHILE
• Only about 15 percent of the energy from the fuel you
put in your tank gets used to move your car down
the road or run useful accessories, such as air
conditioning. The rest of the energy is lost to engine
and driveline inefficiencies and idling.
LITHIUM BROMIDE:
•
Being a salt, lithium bromide does not exert any
pressure and does not boil off when heated. Thus
there is no need of rectifier to separate out the
absorbent vapor from the refrigerant vapor.
• The rate of absorption of water vapor comes down as
temperature of the solution increases. The
concentration of a solution does not change with
temperature, its concentration comes down. This is
because the weight of the total solution has increased
on absorbing water, but salt content has not changed.
A stronger solution can absorb more water vapor
than a solution of lower concentration.
WORKING
IN ABSORBER AND GENERATOR
• The evaporator and absorber are
inter-connected. So the refrigerant
vapor formed in the evaporator is
absorbed by the absorbent in the
absorber thereby maintaining the
refrigerant vapor pressure in the
evaporator at the low level required
for continuous vaporization of liquid
refrigerator to obtain refrigeration.
To recover the refrigerant from the
absorbent it is pumped from the
absorber to the generator, where it
is heated using steam or hot water.
In condenser, evaporator
• On getting heated the absorbent releases
the refrigerant vapor as a high
temperature/pressure vapor. It passes to
the comparatively cooler condenser
where it is condensed. The liquid
refrigerant then passes on to the
evaporator thus completing the
refrigerant cycle. The absorbent flows
back from the generator to the absorber
• Here the condenser is replaced by the
radiator of the vehicle . When the air
cooler is not switched on the hot coolant
water flows into it,when the AC is
switched on it acts as a condensor for the
unit
SCHEMATIC REPRESENTATION OF THE
ABSORPTION CYCLE
HEAT EXCHANGERS USED
• Additionally three heat
exchangers are used
• When the absorbent absorbs
water from evaporator, the
absorbent gets heated. This
heat is transferred thro a heat
exchanger to preheat the cold
water from absorber
• Hot coolant water from
engine is used to heat the
generator solution
• Exhaust gas is used to heat
the refrigerant to run motors
OPERATING CONDITIONS:
• Generator solution temperature = 990C
• Generator solution strength= 63.3%
• Generator solution vapor
pressure=76.2mmHgabs
• Condensing temperature=460C
• Condensing pressure of refrigerant=76.2mmHg
abs
• Absorber solution temperature=38.30C
• Absorber solution strength=59.5%
• Absorber solution vapor pressure=6.35mmHg
• Evaporator temperature=4.440C
• Evaporator refrigerant vapor
pressure=6.35mm(0.25”)Hg abs
DRIVING MOTORS
Frequently, refrigerant
turbines
are
not
considered because their
high work to volume ratio
but it can be used to
increase the efficiency. The
heating chamber takes the
heat from the exhaust gas,
making the refrigerant to
do useful work. After
expansion the refrigerant is
condensed to liquid state so
that on repeating the cycle
the heat transfer would be
max
ADVANTAGES VAPOR ABSORBTION CYCLE
• except for two small centrifugal pumps, there are
no moving parts so less number of moving parts
• step less capacity control down to 0%capacity
which is not possible with reciprocating machines
and centrifugals
• No Freon used
• no recharging cost of refrigerant ,which will be
quite substantial and inevitable in vapor
compression cycle
• low working pressure
ADVANTAGES OF REFRIGERANT
MOTORS:
• may be loaded until full standstill
• overload safe
• torque increase at mounting load
• low installation cost
• maintenance friendly
• high power density
• can be sterilized
LIMITATIONS OF ABSORPTION CYCLE
• low COP
• high heat rejection factor, so requirement of
higher cooling tower and pump capacities
• corrosive nature of lithium bromide corrodes the
heat exchanger
LIMITATIONS OF AIR MOTORS
• total used energy
• noise level
• maintenance intervals
FUTURE SCOPE:
• Condensed liquid refrigerant from the condenser
can be used for refrigeration by passing the
same through capillary tube and then to
evaporator
• All the accessories of a vehicle can be made to
run with the power obtained from refrigerant
turbine, so as to reduce the energy loss of 2.2%
REFERENCES
• Basic Refrigeration and Air Conditioning
- P N Ananthanarayanan
•
Thermodynamics a practical approach
- Yunus Cengel
•
Innovative ACR magazine
September - October 2008
•
www.Wikipedia.org
•
www.howstuffworks.com