67880901 Automobile Ac by Utilising Waste Heat Gases

A

SEMINAR REPORT ON

Automobile Ac by Utilising Waste Heat & Gases SUBMITED IN THE PARTIAL FULFILLMENT OF THE REQEUTREMENT FOR THE AWARD OF DEGREE OF

BACHELOR OF TECHNOLOGY IN MECHANICAL ENGINEERING

SUBMITTED TO: YUDHISTAR SAINI HEAD OF DEPARTMENT MECHANICAL ENGINEERING

SUBMITTED BY: ASHWANI DUBEY ROLL NO. 09ESTME013 IV YEAR VIII SEMESTER  

DEPARTMENT OF MECHANICAL ENGINEERING STANI MEMORIAL COLLEGE OF ENGINEERING & TECHNOLOGY SESSION- 2012 – 2013

PREFACE

A very important element in curriculum of an Engineering student is the SEMINAR. This is a part of the curriculum of the STANI MEMORIAL COLLEGE OF ENGINEERING & TECH.ForB.Tech. course. As we are the students of Mechanical Engineering so the SEMINAR at Automobile-Ac by-Utilising-Waste-Heat-Gases  by-Utilising-Waste-Heat-Gases has been been particularly beneficial beneficial for us.

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ACKNOWLEDGEMENT

The Seminar Report on Automobile-Ac-by-Utilising-Waste-Heat-Gases hasbeen a unique experience for me instead of routine and momentary exercise. It has leap to new field of  acquiring knowledge andlearning. I am deeply in debuted to Mr. T.C.JAIN (Principal ) whose guidance and feedback during the course of the study helped me not only in bringing out his report successfully but also provided a real insight into student matter. I am also thankful for being so helpful and providing us with valuable instructions and study material and also for kind cooperation and help and all other employers who help me in providing various data and information that were needed to accomplish the end result. My heartily thanks to to Mr. YUDHISTAR SAINI, HEAD OF DEPARTMENT DEPARTMENT MECHANICAL SMCET, JAIPURfor all kind of help help they have Granted in absence of which which the report would have not been possible.

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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 condi conditio tionin ning g syste system m which which most most of the A/C vehicles vehicles use is the ‘vapou ‘vapourr Compre Compressi ssion on 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 increasing brake specific fuel 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 Aqua Ammo Ammoni niaa sys syste tem m and and 2. Lithiu Lithium m Bromid Bromidee water water syste system m

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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, car, the flow of air around around moving moving car and relative relatively ly large large glass glass area area in the passeng passenger  er  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 Maximum power is required required when the car is running 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 High oper operat atin ing g cost cost,, sinc sincee fuel fuel econ econom omy y is affe affect cted ed,, high high main mainte tena nanc ncee cost cost,, cost costly ly refrigerant. 3.CFC’s (Chlorofluorocarbon) (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.

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ENGINE The internal combustion combustion engine is an engine in which the combuston of fuel and an oxidizer  oxidizer  (typically air) occurs in a confined space called a combustion chamber. This exothermic reaction create createss gases gases at high high tempre tempretur turee and, and, pressu pressure re which which are permit permitted ted to expand expand.. Intern Internal al combustion engines are defined by the useful work that is performed by the expanding hot gases acting directly to cause the movement of solid parts of the engine. The The term term Intern Internal al Combus Combustio tion n Engine Engine (ICE) (ICE) is often often used used to refer refer to an engine engine in which which combustion is intermittent, such as a Wankel engine or a reciprocating piston engine in which there there is contro controlle lled d moveme movement nt of piston pistons, s, cranks cranks,, cams, cams, or rods. rods. Howeve However, r, conti continuo nuous us combustion engines such as jet engines, most rockets, and many gas turbines are also classified as types of internal combustion engines. This contrasts with external combustion engines such as steam engines and stirling engines that use a separate combustion chamber to heat a separate working fluid which then in turn does work, for example, by moving a piston or a turbine. A huge number of different designs for internal combustion engines exist, each with different stren strength gthss and weakne weaknesse sses. s. Altho Although ugh they'r they'ree used used for many many differ different ent purpos purposes, es, intern internal al combustion engines particularly see use in mobile applications such as cars, aircraft, and even handheld applications: all where their ability to use an energy-dense fuel (especiallyfossil fuels) to deliver a high power-to-weight ratio is particularly advantageous.

 Applications

The motion of internal combustion engines is usually performed by the controlled movement of   pistons, cranks, rods, rods, rotors, or even the entire engine engine itself. Internal combustion engines are most commonly used for mobile propulsion in vehicles and  portable machinery. In mobile equipment, internal combustion is advantageous since it can  provide high power-to-weight ratios together with excellent fuelenergy density. Generally using fossil fuel(mainly petroleum), these engines have appeared in transport in almost all vehicles (automobiles, trucks, trucks, motorcycles, boats, and in a wide variety of of aircrafts and locomotives). These vehicles, when they are not hybrid, are called All-Petroleum Internal Combustion Engine Vehicles (APICEVs) or All Fossil Fuel Internal Combustion Vehicles (AFFICEVs). Internal combustion engines appear in the form of gas turbines as well where a very high power  is required, such as injet aircraft, helicoptores, and large ships. They are also frequently used for  electric generator and by industry. 6

Operation

Four-stroke cycle (or Otto cycle) 1.Intake 2.compression 3.power  4. exhaust

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 Basic process

Internal combustion engines have 4 basic steps: •

Intake

Combustible mixtures are emplaced in the combustion chamber  •

Compression

The mixtures are placed under pressure •

Combustion/Expansion

The The mixtur mixturee is burnt, burnt, almost almost invari invariabl ably y a defla deflagra gratio tion, n, althou although gh a few system systemss involv involvee detonation. The hot mixture is expanded, pressing on and moving parts of the engine and  performing useful work. work. •

Exhaust

The cooled combustion products are exhausted Many engines overlap these steps in time, jet engines do all steps simultaneously at different  parts of the engines. engines. Some internal combustion engines have extra steps. steps.

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Combustion

All internal combustion engines depend on the exothermic chemical process ofcombustion: the reaction of afuel, typically with oxygen from the air—although other oxidizers such as nitrous oxide may be employed. The combustion process typically results in the production of a great quantity of heat, as well as the production of steam and carbon dioxide and other chemicals at very high temperature; the temperature reached is determined by the chemical make up of the fuel and oxidisers . The most common modern fuels are ar e made up of hydrocarbons and are derived mostly fromfossil fuels. fuels. Becaus Becausee of this, this, vehicl vehicles es that that uses uses this this energy energy are called called All-Fo All-Fossi ssill Fuel Fuel Intern Internal al Combustio Combustion n Engine Vehicles Vehicles (AFFICEVs). (AFFICEVs). Fossil fuels include include dieselfuel dieselfuel,, gasoline gasoline and  petrolieum gas, and the rarer use ofpropane. Except for the fuel delivery components, most internal combustion engines that are designed for gasoline use can run on natural gas or  liquefied petroleum gases without

major modifications. Liquid Liquid and gaseousbiofuels gaseousbiofuels such as ethanol and biodiesel (a form of diesel fuel that is produced from crops that yield triglycerides such as soybean oil), can also be used. Some engines with appropriate modifications can also run on hydrogengas. All internal combustion engines must achieve ignition in their cylinders to create combustion. Typically engines use either a spark ignition(SI)method or a compression ignition(CI) system. In the past, other methods using hot tubes or flames have been used. Gasoline Ignition Process Gasoline engine ignition systems generally rely on a combination of a lead-acid battery and an induction coil to provide a high-voltage electrical spark to ignite the air-fuel mix in the engine's cylinders. This battery is recharged during operation using an electricity-generating device such as an alternator or generator driven by the engine. Gasoline engines take in a mixture of air and gasoline and compress it to not more than 185 psi, then use a spark plug to ignite the mixture when it is compressed by the piston head in each cylinder. Diesel Ignition Process Diesel engines and HCCI engines, rely solely on heat and pressure created by the engine in its compression process for ignition. The compression level that occurs is usually twice or more than than a gaso gasoli line ne engi engine ne.. Dies Diesel el engi engine ness will will take take in air air only only,, and and shor shortl tly y befo before re peak  peak  compression, a small quantity of diesel fuel is sprayed into the cylinder via a fuel injector that allows the fuel to instantly ignite. HCCI type engines will take in both air 

and fuel but continue to rely on an unaided auto-combustion process, due to higher pressures and heat. This is also why diesel and HCCI engines are more susceptible to cold-starting issues, although they will run just as well in cold weather once started. Light duty diesel engines in automobiles and light trucks employ glow plugs that pre-heat the combustion chamber just 9

 before starting to reduce no-start conditions in cold weather. Most diesels also have a battery and charging system; nevertheless, this system is secondary and is added by manufacturers as a luxury for the ease of starting, turning fuel on and off (which can also be done via a switch or  mechanical apparatus), and for running auxiliary electrical components and accessories. Most new engines rely on electrical and electronic control systems that also control the combustion  process to increase efficiency efficiency and reduce emissions. emissions.

 Measures of engine performance performance

Engine types vary greatly in a number of different ways: •

•

Energy effeciency fuel/propellant consumption (brake specific fuel consumtion for shaft engines, thrust specific fuel consumption for jet engines)

•

 power to weight ratio ratio

•

thrust to weight ratio

•

torque curves(for shaft engines)

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 Energy Efficiency

Once ignited and burnt, the combustion products—hot gases—have more available thermal energy than the original compressed fuel-air mixture (which had higherchemical energy). The available energy is manifested as high tempreture and pressure that can be translated into work   by the engine. In a reciprocating engine, the high-pressure gases inside the cylinders drive the engine's pistons.

Once the available energy has been removed, the remaining hot gases are vented (often by opening a valve or exposing the exhaust outlet) and this allows the piston to return to its  previous position position (top dead center, or TDC). The piston can can then proceed to the next phase of its cycle, cycle, which varies between between engines. engines. Any heat that isn't translate translated d into work is normally normally considered a waste product and is removed from the engine either by an air or liquid cooling system. Engine efficiency can be discussed in a number of ways but it usually involves a comparison of  the total chemical energy in the fuels, and the useful energy abstracted from the fuels in the form of kinetic energy. The most fundamental and abstract discussion of engine efficiency is the thermodynamic limit for abstracting energy from the fuel defined by a thermodynamic cycle. The The most most compre comprehen hensiv sivee is the the empiri empirical cal fuel fuel econom economy y of the total total engine engine system system for  accomplishing a desired task; for example, the miles per gallon accumulated. Internal combustion engines are primarily heat engines and as such the phenomenon that limits their efficiency is described by

thermodynamic cycles. None of these cycles exceed the limit defined by the Carnot cycle which states that the overall efficiency is dictated by the difference between the lower and upper  operating temperatures of the engine. A terrestrial engine is usually and fundamentally limited  by the upper thermal stability derived from the material used to make up the engine. All metals and alloys eventually melt or decompose and there is significant researching into ceramic materials that can be made with higher thermal stabilities and desirable structural properties. Higher thermal stability allows for greater temperature difference between the lower and upper  operating temperatures—thus greater thermodynamic efficiency. The thermodynamic limits assume that the engine is operating in ideal conditions. A frictionless world, ideal gases, perfect insulators, and operation at infinite time. The real world is substantially more complex and all the complexities reduce the efficiency. In addition, real engines run best at specific loads and rates as described by their power curve. For example, a car  cruising on a highway is usually operating significantly below its ideal load, because the engine is designed for the higher loads desired for rapid acceleration. The applications of engines are used as contributed drag on the total system reducing overall efficiency, such as wind resistance designs for vehicles. These and many other losses result in an engines' real-world fuel economy 11

that is usually measured in the units of miles per gallon (or kilometers per liter) f or automobiles. The miles in, "MPG" represents a meaningful amount of work and the volume of hydrocarbon implies a standard energy content. Most steel engines have a thermodynamic limit of 37%. Even when aided with turbochargers and stock efficiency aids, most engines retain an average efficiency of about 18%-20%.

There are many inventions concerned with increasing the efficiency of IC-Engines. In general, practical engines are always compromised by trade-offs between different properties such as efficienc efficiency, y, weight, weight, power, power, heat, heat, response, response, exhaust exhaust emissions, emissions, or noise. noise. Sometimes Sometimes economy also plays a role in not only in the cost of manufacturing the engine itself, but also manufacturing and distributing the fuel. Increasing the engines' efficiency brings better fuel economy but only if the fuel cost per energy content is the same.

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 Seebeck effect 

The See beck effect is the conversion of temperature temperature differences directly directly into electricity. electricity. Seebeck discovered that a compass needle would be deflected when a closed loop was formed of two metals joined in two places with a temperature difference between the junctions. This is because the metals respond differently to the temperature difference, which creates a current loop, which produces a magnetic field. Seebeck, however, at this time did not recognize there was an electric current involved, so he called the phenomenon the thermomagnetic effect, thinking that the two metals became magnetically polarized by the temperature gradient. The Danish physicist Hans Christia Ørsted played a vital role in explaining and conceiving the term "thermoelectricity".

The effect is that a voltage, the thermoelectric EMF, is created in the presence of a temperature difference between two different metals or semiconductors. This causes a continuous current in the conductors if they form a complete loop. The voltage created is of the order of several microvolts per kelvin difference. One such combination, copper-constantan, copper-constantan, has a Seebeck  coefficient of 41 microvolts per kelvin at room temperature. In the circuit:

(which can be in several different configurations and be governed by the same equations), the voltage developed can be derived from:

SA and SB are the Seebeck coefficients (also called thermoelectric power or thermopower) of the metals A and B as a function of temperature, and T 1 and T2 are the temperatures of the two  junctions. The Seebeck coefficients

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are non-linear as a function of temperature, and depend on the conductors' absolute temperature, material, and molecular structure. If the Seebeck coefficients are effectively constant for the measured temperature range, the above formula can be approximated as:

The Seebeck effect is commonly used in a device called a thermocouple (because it is made from a coupling or junction of materials, usually metals) to m easure a temperature difference directly or to measure an absolute temperature by setting one end to a known temperature. Several thermocouples when connected in series are called a thermopile, which is sometimes constructed in order to increase the output voltage since the voltage induced over each individual couple is small. This is also the principle at work behind thermal diodes and thermoelectric generators (such as radioisotope thermoelectric thermoelectric generators or RTGs) which are used for creating power from heat differentials. The Seebeck effect is due to two effects: charge carrier diffusion and phonon drag (described  below). If both connections connections are held at the same temperature, temperature, but one connection connection is periodically opened and closed, an AC voltage is measured, which is also temperature dependent.

This application of the Kelvin probe is sometimes used to argue that the underlying physics only needs one junction. And this effect is still visible if the wires only come close, but do not touch, thus no diffusion is needed.

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Thermopower 

The thermopower, or thermoelectric power, or Seebeck coefficient of a material measure the magnitude of an induced thermoelectric voltage in response to a temperature difference across that material. The thermopower has units of (V / K), though in practice it is more common to use microvolts per kelvin. Values in the hundreds of μV/K, negative or positive, are typical of  good thermoelectric materials. The term thermopower is a misnomer since it measures the voltage or electric field induced in response to a temperature difference, not the electric power. An applied temperature difference causes charged carriers in the material, whether they are electrons or holes, to diffuse from the hot side to the cold side, similar to a classical gas that expands when heated. Mobile charged carriers migrating to the cold side leave behind their  oppositely charged and immobile nuclei at the hot side thus giving rise to a thermoelectric voltage (thermoelectric refers to the fact that the voltage is created by a temperature difference). Since a separation of charges also creates an electric potential, the buildup of 

charged carriers onto the cold side eventually ceases at some maximum value since there exists an equal amount of charged carriers drifting back to the hot side as a result of the electric field at equilibrium. Only an increase in the temperature difference can resume a buildup of more charge carriers on the cold side and thus lead to an increase in the thermoelectric voltage. Incidentally the thermopower also measures the entropy per charge carrier in the material. To be more specific, the partial molar electronic heat capacity is said to equal the absolute thermoelectric power multiplied by the negative of Faraday's constant.

The thermopower of a material, represented by S (or sometimes by α), depends on the material's temperature and crystal structure. Typically metals have small thermopowers because most have half-filled bands. Electrons (negative charges) and holes (positive charges) both contribute to the induced thermoelectric voltage thus canceling each other's contribution to that voltage and making it small. In contrast, semiconductors can be doped with an excess amount of  electrons or holes and thus can have large positive or negative values of the thermopower  depending on the charge of the excess carriers. The sign of the thermopower can determine which charged carriers dominate the electric transport in both metals and semiconductors.

If the temperature difference ΔT between the two ends of a material is small, then the thermopower of a material is defined (approximately) as:

and a thermoelectric voltage ΔV is seen at the terminals. This can also be written in relation to the electric field E and the temperature gradient the approximate equation:

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, by

In practice one rarely measures the absolute thermopower of the material of interest. This is  because electrodes attached attached to a voltmeter must be be placed onto the material in order to measure the thermoelectric voltage. The temperature gradient then also typically induces a thermoelectric voltage across one leg of the measurement electrodes. Therefore the measured thermopower  includes a contribution from the thermopower of the material of interest and the material of the measurement electrodes. The measured thermopower is then a contribution from both and can be written as:

Superconductors have zero thermopower since the charged carriers produce no entropy. This allows a direct measurement of the absolute thermopower of the material of interest, since it is the thermopower of the entire thermocouple as well. In addition, a measurement of the Thomson coefficient, μ, of a material can also yield the thermopower through the relation:

The thermopower is an important material parameter that determines the efficiency of a thermoelectric material. A larger induced thermoelectric voltage for a given temperature gradient will lead to a larger efficiency. Ideally one would want very large thermopower values since only a small amount of heat is then necessary to create a large voltage. This voltage can then be used to provide power.

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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

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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.

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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

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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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5.OPERATING THE SYSTEM 

As we know that ‘VARS’ is a heat operated refrigerating machine in which heat is supplied to the generator. So this required heat we will supply from the ‘waste heat’ (coolant loss and exhaust) which is our center of focus. So we have to distribute the exhaust gases and the coolant to all the system whenever necessary to satisfy the cold and hot air conditioning and flexibility of operation in various possible mode.

For this there are two types of circuits. 1) Cool Coolan antt cir circu cuit it 2) Exha Exhaus ustt cir circu cuit it 1.Coolant Circuit: -

In vapour absorption refrigeration system, there is necessity of cooling of absorber and condenser, which is achieved by water-cooling. The water is supplied to this system by radiator  and heat gained by the cooling water from the engine is utilized in generator and heater. The systematic arrangement is shown in the given fig. The coolant circuit in various modes of operations is given below: I.

Norm Normal al runn runnin ing g with with A/C A/C OFF. OFF.

Circuit: - (Radiator - V3-Engine – V2 – Radiator) Valve position: a) V2---0-1  b) V3---0-1 II. II.

Norma Normall run runni ning ng with with A/C A/C ON. ON.

i. For summer summer ( or high high surrou surroundin nding g temperat temperature) ure) Circuit Circuit :-( Radiator-V Radiator-V3-Con 3-Condense denserr – Absorber-R Absorber-Recti ectifier-N fier-N.R.V.-E .R.V.-Engin ngine-V2 e-V2-Gene -Generator rator- N.R.V-Radiator) Valve position 20

a) V2---0-2  b) V3---0-2 ii. For winter winter (or low low surroun surrounding ding temperatur temperature) e) Circuit: - (Radiator –V3 Engine-V2-Heater-N.R.V.-Radiator) Valve position a) V2---0-3  b) V3---0-1 2.Exhaust Circuit: -

We are using the waste exhaust gas heat to the generator and heater and then the exhaust gas is exhaus exhausted ted to atmosp atmosphe here. re. Distri Distribu butio tion n of the the gas to the the genera generator tor,, heater heater and the atmosphere is maintained by exhaust circuit whenever necessary. The exhaust gas be either fed to the heater during winter or the generator during the summer or bypassed to the atmosphere. Exhaust Circuit: A. Normal Normal runn running ing with with A/C OFF. OFF. Circuit: - (Engine V1 to atm.) Valve position V1---0-1 B. Normal Normal runnin running g with with A/C A/C ON ON a) For summer summer (or (or high high temperatu temperature re of of surroun surrounding ding)) Circuit: - (Engine V1 generator N.R.V. to atm.) Valve position V1---0-2  b) For winter (or low temperature temperature of surrounding) Circuit: - (Engine V1 generator N.R.V. to atm.) Valve position V1---0-3

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AIR CONDITIONING SYSTEM The outside air flows through the damper and mixes up with the recirculated air (which is obtained from the conditioned space.) The mixed air passes through a filter to remove dirt, dust and other impurities. In summer air conditioning, conditioning, the cooling coil operates to cool the air to the desired value. The dehumidification is obtained by operating the cooling coil at a temp lower  than the dew point temperature (apparatus due point). In winter the cooling coil is made in operative and the heating coil operates to heat the air. The schematic arrangement can be shown  by fig.6 7.INSTALLATION 

For the design of the complete system the requirements are: 1) Engine Engine manual (suppli (supplied ed by the manufacture) manufacture) containi containing ng all details details about about the engine engine  performance and characteristics, characteristics, especially cooling cooling and exhaust. 2) Determ Determin ining ing the coolin cooling g capaci capacity ty required required for a partic particul ular ar vehicl vehiclee in a partic particula ular  r  region, considering the year round meteorological conditions conditions the various parameters of  the air – conditioner can be defined.

The year round air –conditioning can be achieved by the system which is required in the cities like New Delhi where it is too cold in winter and quit hot in summer. Thus by knowing the amount of waste heat available (usable) and the cooling capacity, various component of the system can be designed. To get rough idea, let us see the heat available (usable) and the cooling capacity, various components capacity required for a car as 2TR let’s find the heat requirement for a certain aqua ammonia system.

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Case Study of SI Engine 4-Stroke, 6-cylinder (7.5 cm bore and 9-stroke) Rpm=3300 Fuel consumption

= 0.3 kg/min

c.v.

=42000 kJ/min

Jacket water flow rate Q

= 65 kg/min

Temperature rise

= 12/C

Ventilate air blown up

= 14 kg/min

Enters at 10/C and leaves at 65/C (Engine in insulated box) B . P. Heat input

= 42.55 kW (100%) = 0.3 * 42000 = 12600 KJ/min

i.

Heat equivalent to B.P.

= 42.55 * 60 = 2553 KJ/min

ii. He H eat in cooling water

= (65*4.1868*12) = 3266 KJ/min (25.9%)

iii. He H eat in ventilating air

= 14*1.055*55 =774 KJ/min. (6.14%)

iv. Heat to exhaus exhaustt and Other losses

= 6007 KJ/min (47.66%)

So heat available for VARS

= Heat in cooling water + Heat in exhaust = 3266 + 6007 = 9273 KJ/min. (73.59%)

Let us assume that the effectiveness of heat exchangers be 0.7  Net heat available

=

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6491.1 KJ/min

Case Study Of An Aqua- Ammonia System Now a case study of aqua-ammonia aqua-ammonia system is asIn an aqua ammonia vapour absorption system the following data is available: Temperature of weak solution in generator

=100degr.C

Temperature of strong solution admitted to generator

=80 degr. C

Temperature of condenser = Temperature of absorber

=40 degr.C

Temperature rise in evaporator

=10 degr.C

Analysis for 2 tonn refrigeration capacity: (Mass flow of ammonia through evaporator) m = 2*3.5/h4-h3 = 7/1600-535 = 0.00657/kg/sec. i. Heat suppl supplied ied per per kg.of ammonia ammonia in the generat generator  or  = h12-ha =1840-(-425) =2265kj/kg(ammonia) Q (kJ/sec)

= 0.066*2265 =14.75 kJ/sec

ii. Heat Heat rejec rejected ted in the the abso absorbe rbed d per per sec. sec. Qa

=mr (h4-ha) =0.0066(1600+425) =13.3 kJ/sec

iii. iii.

Degass Degassing ing C5-Cw C5-Cw C7-C8 C7-C8 = 0.46-0.4 0.46-0.4 =0.06 kg/kg of aqua

iv.

Heat rejected rejected in deflimator deflimator (cooler (cooler after generator) generator) =mr (h12-h1) =0.0066(1840-1630) =1.38

v.

Heat Heat reje reject cted ed in cond conden ense ser  r  24

Qc

=mr (h1-h2) =0.0066(1630-535) =7.197

vi.

Consideri Considering ng the enthalp enthalpy y balance balance across across the heat heat exchange exchanger, r, we can write, write,

Heat lost by weak solution = Heat gain by strong solution For 1kg ammonia entering into the absorber mw kg of weak solution is entering then ms=mw+1 mw (h8-h9) =(mw+1)(h7-h6); mw (350-120) = (mw+1)(260-70) 40 mw = 190 mw = 4.75 kg/kg of ammonia ms (strong solution handled by the pump)= mw+1 =4.75+1 =5.75 kg/kg of ammonia =0.0066 * 5.75 =0.037 kg/sec vii. c.o.p. Qe/Qg = h4-h3/Q9=1600-535/2265 h4-h3/Q9=1600-535/2265=0.47 =0.47 viii. Energetic ne is given by  Ne = Qe/Qg [Tg/Te (Te-Te/Tq-Te)] (Te-Te/Tq-Te)] =0.47(100+273/10+273)(40-10/100-40) =31% Heat supplied

=4.75kj/sec.

Heat rejected in absorber

=3.3kj/sec.

Heat rejected

=7.197

Heat rejected in deflimator

=1.38

Heat supplied

=14.75kj/sec.

Heat rejected

=13.3+7.197 25

Heat rejected in condenser

=7.197

Heat rejected in deflimator

=1.38

Heat supplied

=14.75kj/sec.

Heat rejected

=13.3+7.197 =20.49kj/sec

Heat supplied

=885kj/min

Heat rejected

=1229.82kj/min

Heat available

=3266+6007

Considering ef effectiveness

=0.7=2286+4204 =6490kj/min

Heat required

=885kj/min.

Thus we see that a large amount of heat is available and our requirement is lesser. The system here described is simple basic. It can be further improved and made sophisticated by using various control systems and relays. A basic control system is shown in f ig. 7 Apart from the new design of vehicles installing (VARS), the existing vehicles can also  be equipped with this this system and by studying studying the make of particular particular a proper placed can be found out for erecting the system and tracing various circuits.

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CONTROLLING THE SYSTEM

The exhaust coolant circuit is controlled by 3 valves V1, V2 and V3. The valve V1 operates the exhaust circuit and the valves V2 &V3 operate the coolant circuit where valve V3 is two way valves and other two V1 and V2 are three way valves. The combination of position of valve for  different conditions are as shown below: V1

V2

V3

A/C OFF

A/C OFF

1

1

1

A/C ON

Summer

2

2

2

A/C ON

Winter

3

3

1

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ERECTION

By studying the manual of the particular vehicle, an appropriate place can be found out for the erection of the system for existing vehicles and for newer design, it is to be already taken into consideration. The condenser, expander, absorber and evaporator should be kept away from the engine as possible because the engine evolves at high temp. The conditioned air supply and distribution system remains the same as in the existing A/C vehicles.

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ADVANTAGES ADVANTAGES OF VARS OVER VCRS

1) No moving moving parts so, quiet quiet in operation, operation, subjecte subjected d to little little wear, low maintenan maintenance ce cost. The The  pump required quite small small power in comparison with with compressor. 2) Larg Largee cap capac acit ity. y. 3) Excellent Excellent part part load efficiency efficiency and and almost constan constantt c.o.p. of the system system over a wide range range of  load. 4) Automa Automatic tic capa capacit city y contro controll is easy. easy. 5) Smalle Smallerr space space per unit unit capa capacit city. y. 6) No har harm m to the the ozo ozone ne lay layer er.. 7) Inex Inexpe pens nsiv ivee refri refrige gera rant nt.. 8) Leakage Leakage can be be easily easily detected detected in case case of aqua aqua ammonia ammonia system. system. 9) It can can reduce reduce the global global warming warming of of atmosph atmosphere. ere.

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CONCLUSION

Thus we have seen that the VARS is efficient in every respect, and can be successfully implemented with better designs and sophistication. sophistication. Now it is the task of the up coming engineers to overcome the hurdles in the way if any and make our country’s people enjoy the comfort and luxury of A/C and fuel will also be saved to a greater extent which would have been consumed in excess by the (VARS) air conditioner.

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REFERENCES



Basic Refrigeration and Air conditioningconditioning- P.N. Anathnarayan



Refrigeration and air conditioning – C.P. Arora



A course in Refrigeration and Air-conditioning- S.C.Arora, S.Domkundwar 



Thermodynamics and Heat Engines- R.Yadav



A course in Internal Combustion Engines – M.L. Mathur, R.P. Sharma



Automobile Engineering –R.B. Gupta



A Text Book of Refrigeration And Air Conditioning –R.S. Khurmi & S.K. Gupta



WWW.Beyond2000.com (concept)



www.google.com

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