PROJECT PRESENTATION REFRIGERATION USING WASTE HEAT IN CARS 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