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ABSTRACT
HEATING AND AIR CONDITIONING
Today, ventilation, heating, and air conditioning systems are very important elements for providing passenger comfort. Ventilation and heating systems are standard equipment on all passenger vehicles and air conditioning for nearly all.
The large number of vehicles with air conditioning plus recent changes in the methods used to cool a vehicle and to service the system makes a basic knowledge of air conditioning systems a must for automotive technicians.
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ENVIRONMENTAL FRIENDLY REFRIGERATION &
AIR CONDITIONING SYSTEM
SUBJECT:
AUTOMOBILE A/C BY UTILISING
WASTE HEAT & GASES
PRESENTED BY:
MS. KIRAN G. HORE
MS JYOTI S. KOTECHA
(MECHANICAL ENGINEERING)
ABSTRACT
It is the established fact that only about 30% of heat supplied by the fuel is converted into useful work, in case of internal combustion (I.C) engines and the rest is going waste to the atmosphere in the form of coolant losses (35%) and exhaust gas losses (35%). The conventional air conditioning system which most of the A/C vehicles use is the ‘vapour Compression refrigeration system ‘, in which the compressor needs mechanical work that is Higher-grade energy is then taken directly from the engine crankshaft. Thus it ultimately reduces the brake power (B.P.) available and increasing brake specific fuel consumption.
The ‘vapour absorption refrigeration system ‘utilizes the waste heat as it does not involve any compressor and hence not require great mechanical work instead of that it works directly on the heat energy i.e. .low grade energy.
Thus by making proper use of lost heat (about 60 –70% of total heat). The conventional air conditioning can be replaced with this system and the same effect can be experienced. The common vapour absorption refrigeration systems, which are in practice, are
1. Aqua Ammonia system and
2. Lithium Bromide water system
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Presented by:
K.A.FENU
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HEATING AND AIR-CONDITIONING
INTRODUCTION
Today ventilation, heating and air-conditioning systems are very important elements for providing passenger comfort.
Ventilation and heating systems are standard equipment on all passenger vehicles and air-conditioning the standard on some and available for nearly all.
The large number of vehicle with air conditioning plus recent changes in the methods used to cool a vehicle and to service the systems makes a basic knowledge of air-conditioning system.
VENTILATION SYSTEM
The ventilation system is to provide outside air to the passenger compartment.
Among the several systems used to vent air to the passenger compartment flow-through system is the most common.
In this the ram air flows into the car when it is moving.
When the car is not moving , a steady flow of ram air can be produced by the heater fan.
AUTOMOTIVE HEATING SYSTEM
It has been designed to handle with cooling system.
The primary function is to provide comfortable temperature.
The primary component of the system are Heat core, Heater control valve, The blower motor and the fan.
HEATER CONTROL VALVE
It controls the flow of coolant into the heater core from the engine.
In a closed position, the valve allows no flow of hot coolant to the heater core, keeping it cool.
In a open position, the allow heated coolant to circulate through the heater core.
The blower motor is located in heater housing assembly, it is used to ensure air circulate through out the system. It speed is controlled by multiposition switch.
THEORY OF AIR-CONDITIONING
All air conditioning system are based on three thee fundamental law of nature.
HEAT FLOW : Greater the temperature difference between the object, greater the heat flow.
HEAT ABSORBTION: When changes from one state to another, absorption or rejection of heat takes place.
PRESSURE AND BOILING POINTS: The greater the pressure on a substance, such as a liquid, changes its boiling point.
Greater the pressure higher the boiling point and lesser the pressure lower is the boiling point.
REFRIGERANTS IN AIR CONDITIONING SYSTEM
The substance used to remove heat from the inside of an air conditioned vehicle is called the refrigerant.
Older refrigerant used in AC was R-12.
The latest AC system uses R-134a,this refrigerant may also referred to as SUVA.
It is an efficient then.
AIR CONDITIONING SYSTEM AND ITS COMPONENT
COMPRESSOR
CONDENSER
EVAPORATOR
RECEIVER/DRYER
COMPRESSOR
The compressor is heart of automotive AC system. It separates the high pressure and low pressure sides of the system.
The primary function is to draw the low pressure and low temperature vapor from the evaporator and compress this vapor into high-temperature, high pressure vapor.
The secondary function is to circulate the refrigerant through the AC system
It is driven by the engines crankshaft via a drive belt.
Types of compressor
PISTON COMPRESSOR: This type of compressor can have its piston arranged in an in-line, axial, radial or V-design.
On the intake stroke, the refrigerant from the low side of the system is drawn into the compressor.
During compression stroke, the refigerant is compressed.
This increase both the pressure and the temperature of the heat carrying refrigerant.
ROTARY VANE COMPRESSOR: It does not have any piston. It consist of a rotor with several vanes and carefully shaped housing
As the compressor shaft rotates, the vanes and housing foam chamber. The refrigerant is drawn through the suction port in this chimer, which becomes smaller as the rotor runs.
The discharged port is located at the point where the gas is completely compressed.
CONDENSER
The condenser consists of coiled refrigerant tubing mounted in series of thin cooling fins.
The purpose of condenser is to condense the high pressure, high temperature vapor coming from the compressor.
It is achieved when the refrigerant vapor enters the inlet of condenser and hot vapor passes down to the condenser coil.
This process causes a large quantity of heat to be transferred to the outside air and the refrigerant to change from a high-pressure hot vapor to high-pressure warm liquid.
RECEIVER/DRYER
It is a storage tank for refrigerant from the condenser.
Its upper part consist of ca bag of DESICCANT.
The lower portion contains a mesh screen to absorb impurities.
EVAPORATOR
It consist of a refrigerant coil mounted in a series of thin cooling fins.
Upon receiving refrigerant dryer, heat from the core surface is lost to the boiling and vaporizing refrigerant, which is cooler than the core ,thereby, cooling the core.
The air passing over the evaporator loses its heat to cooler surface of the core, there by cooling the air inside the car.
REFRIGERANT LINES
Three major refrigerant lines: suction, liquid and discharge.
Suction lines are located between the outlet side of the evaporator and inlet side of the compressor.
The liquid lines connect the condenser to the receiver and receiver to the inlet of the expansion valve.
CONCLUSION
In the busy world of today comfort plays a very important role in a man’s life.
In the olden days men had to adjust to the surroundings but in modern life science has developed a lot that surroundings adjust to the men’s needs , i. e passenger comfort.
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PRESENTED BY:
MS. KIRAN G. HORE
MS JYOTI S. KOTECHA
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1. ABSTRACT
It is the established fact that only about 30% of heat supplied by the fuel is converted into useful work, in case of internal combustion (I.C) engines and the rest is going waste to the atmosphere in the form of coolant losses (35%) and exhaust gas losses (35%). The conventional air conditioning system which most of the A/C vehicles use is the ‘vapour Compression refrigeration system ‘, in which the compressor needs mechanical work that is Higher-grade energy is then taken directly from the engine crankshaft. Thus it ultimately reduces the brake power (B.P.) available and increasing brake specific fuel consumption.
The ‘vapour absorption refrigeration system ‘utilizes the waste heat as it does not involve any compressor and hence not require great mechanical work instead of that it works directly on the heat energy i.e. .low grade energy.
Thus by making proper use of lost heat (about 60 –70% of total heat). The conventional air conditioning can be replaced with this system and the same effect can be experienced. The common vapour absorption refrigeration systems, which are in practice, are
1. Aqua Ammonia system and
2. Lithium Bromide water system
2.EXISITING AIR-CONDITIONING SYSTEM
The use of air conditioner for transport purpose may be a luxury in India but it is commonly used in foreign countries .In comparison to domestic air-conditioning a very large amount of air-conditioning capacity is required for a car. This is due to metal construction of the car, the flow of air around moving car and relatively large glass area in the passenger compartment. Typically, a car A/C system capacity may be between 1 to 4 tons. The system works on Vapour Compression Refrigeration System (VCRS) and the compressor consumes large amount of engine brake power (1 to 10 h.p.) as it is directly driven by the engine. This affects the fuel economy severely. A loss in economy level of the order of 1 to 1.5 km/liter can occur due to the use A/C. Maximum power is required when the car is running at maximum speed under high ambient temperature conditions. Apart far from this VCRS has got certain drawback, which limits its extensive use among common car owner.
DRAWBACKS
1. High initial cost.
2. High operating cost, since fuel economy is affected, high maintenance cost, costly refrigerant.
3. CFC’s (Chlorofluorocarbon) if leaks out of the system causes great damage to the ozone layer.
4. If the car’s reserve power is less, it can affect its acceleration.
5. Overloading and overheating of the engine takes place.
3. THE AUTOMOBILE ENGINE
The prime mover of the automobile (I.C. engine) is a heat engine, which can convert only a fraction of the total heat of fuel into the useful work.
20 to30 % for SI engines
30 to 36% for CI engines
The remaining heat is lost to the atmosphere through the coolant and exhaust. Heat balance is given in the below table: -
%AGE OF FUEL ENERGY
S.I. C.I.
To power 26 31
To coolant 30 26
To exhaust 32 30
Radiation 12 13
Also refer the fig. 1
Thus we have about 60% of heat which is going waste. So, with such a small efficiency of the heat engine. Obviously it is not worthwhile for a common man to install such an A/C in his car.
4. AN ALTERNATIVE TO THIS SYTEM
The concept is to use this otherwise going waste heat, for air-conditioning with the aid of Vapour Absorption System (VARS) which does not affect the engine power. It need no maintenance and is environment friendly.
VARS is a ‘heat operated refrigeration machine ‘ in which the compressor is replaced by the combination of absorber and generator. A solution known as the absorbent (e.g. water in case of A qua-ammonia system) which has an affinity for the ‘refrigerant’ used (i.e. ammonia) is circulated between the absorber and the generator by a pump (solution pump). I n this system, the low pressure ammonia vapour living the evaporator, enters the absorber where it is absorbed by the low temperature water in the absorber .The water has the ability to absorb very large quantity of ammonia vapour and the solution thus formed, is known as Aqua-ammonia. The absorption of ammonia vapour lowers the pressure in the absorber, which in turn draws more ammonia vapour from the evaporator and thus raises the temperature of solution. Some form of cooling arrangement (usually water-cooling) is employed in the absorber to remove the heat of solution evolved there. This is necessary in order to increase the absorption capacity of water. The liquid pump pumps the strong solution thus formed in the absorber to the generator. The pump increases the pressure of the solution upto 10bar. The strong solution of ammonia in generator is heated by heat of coolant and the exhaust gases, which are waste in atmosphere without any use and the heat, wasted in cooling of engine. During the heating process, the ammonia vapour is driven of the solution at high pressure leaving behind the hot weak ammonia solution in the generator. The weak ammonia solution flows back to the absorber at low pressure after passing through the reducing valve. But then also the ammonia vapour contains some particles of water. If these unwanted water particles are not removed before entering into the condenser, they will enter into the expansion valve where they freeze and choke the pipeline. In order to remove these unwanted
particles flowing to the condenser, an analyzer is used. The analyzer may be built as an integral part of the generator or made as a separate piece of equipment. It consists of a series trays mounted above the generator. The strong solution from the absorber and the aqua from the rectifier are introduced at the top of analyzer and flow downward over the trays and into the generator. In this way, considerable liquid surface area is exposed to the vapour rising from the generator. The vapour is cooled and most of the water vapour condenses. So, that mainly ammonia vapour, leaves the top of the analyzer. Since the aqua is heated by the vapour, less the generator is condensed in the condenser to high-pressure liquid ammonia. This liquid ammonia is passed to the expansion valve through a receiver and then to the evaporator. This evaporator is made up of number of tubes, which is installed in the cabin of automobile. The function of compressor is performed by the absorbent in the absorber, and the generator performs the function of compression and discharge. The complete system is schematically represented in the fig. 2.
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