Chapter 1

Introduction

1. Introduction

Peltier crystal based vaccine fridge can be a low cost low maintenance system for vaccination in remote areas due to its portable design. Before going to understand working lets first understand the components and their specifications.

1.1 Thermo electric effect

Thethermoelectric effect is the direct conversion oftemperaturedifferences to electricvoltageand vice versa. A thermoelectric device creates voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, it creates a temperature difference. At the atomic scale, an applied temperaturegradientcauses charge carriers in the material to diffuse from the hot side to the cold side. This effect can be used to generate electricity, measure temperature or change the temperature of objects. Because the direction of heating and cooling is determined by the polarity of the applied voltage, thermoelectric devices can be used as temperature controllers. The term "thermoelectric effect" encompasses three separately identified effects: theSeebeck effect,Peltier effect, andThomson effect. Textbooks may refer to it as the PeltierSeebeck effect. This separation derives from the independent discoveries of French physicist Jean Charles Athanase PeltierandBaltic Germanphysicist Thomas Johann Seebeck.Joule heating, the heat that is generated whenever a current is passed through a resistive material is related though it is not generally termed a thermoelectric effect. The PeltierSeebeck and Thomson effects arethermodynamically reversible,[1]whereas Joule heating is not.

1.2 Seebeck effect

A thermoelectric circuit composed of materials of different Seebeck coefficient (p-dopedand n-doped semiconductors), configured as a thermoelectric generator. If the load resistor at the bottom is replaced with a voltmeterthe circuit then functions as a temperature-sensingthermocouple.

TheSeebeck effectis the conversion oftemperaturedifferences directly intoelectricityand is named after theBaltic Germanphysicist Thomas Johann Seebeck, who, in 1821, discovered that a compass needle would be deflected by a closed loop formed by two different metals joined in two places, with a temperature difference between the junctions. This was because the metals responded differently to the temperature difference, creating a current loop and amagnetic field. Seebeck did not recognize there was an electric current involved, so he called the phenomenon the thermo magnetic effect. Danish physicistHans Christian rstedrectified the mistake and coined the term "thermoelectricity".

The Seebeck effect is a classic example of anelectromotive force(emf) and leads to measurable currents or voltages in the same way as any other emf. Electromotive forces modifyOhm's lawby generating currents even in the absence of voltage differences (or vice versa); the localcurrent densityis given by

Whereis the localvoltageandis the localconductivity. In general the Seebeck effect is described locally by the creation of an electromotive field

WhereSis theSeebeck coefficient(also known as thermo power), a property of the local material, and is thegradientin temperatureT.

The Seebeck coefficients generally vary as function of temperature, and depend strongly on the composition of the conductor. For ordinary materials at room temperature, the Seebeck coefficient may range in value from 100V/K to +1,000V/K (seeSeebeck coefficientarticle for more information).

If the system reaches a steady state where, then the voltage gradient is given simply by the Emf. This simple relationship, which does not depend on conductivity, is used in thethermocoupleto measure a temperature difference; an absolute temperature may be found by performing the voltage measurement at a known reference temperature. A metal of unknown composition can be classified by its thermoelectric effect if a metallic probe of known composition is kept at a constant temperature and held in contact with the unknown sample that is locally heated to the probe temperature. It is used commercially to identify metal alloys. Thermocouples in series form athermopile. Thermoelectric generatorsare used for creating power from heat differentials.

Fig 1.1 Seeback Effect

(http://en.wikipedia.org/wiki/Thermoelectric_effect)

1.3 Thomson effect

In many materials, the Seebeck coefficient is not constant in temperature, and so a spatial gradient in temperature can result in a gradient in the Seebeck coefficient. If a current is driven through this gradient then a continuous version of the Peltier effect will occur. ThisThomson effectwas predicted and subsequently observed byLord Kelvinin 1851. It describes the heating or cooling of a current-carrying conductor with a temperature gradient.

If a current densityJ is passed through a homogeneous conductor, the Thomson effect predicts a heat production rateper unit volume of:

Where the temperature gradient and K is the Thomson coefficient. The Thomson coefficient is related to the Seebeck coefficient as . This equation however neglects Joule heating and ordinary thermal conductivity.

1.4 Peltier Effect

ThePeltier effectis the presence of heating or cooling at an electrified junction of two different conductors and is named for French physicistJean Charles Athanase Peltier, who discovered it in 1834. When a current is made to flow through a junction between two conductors A and B, heat may be generated (or removed) at the junction. The Peltier heat generated at the junction per unit time,, is equal to

I

Where are the Peltier coefficients of conductor A (B), andIis the electric current (from A to B). Note that the total heat generated at the junction is not determined by the Peltier effect alone, as it may also be influenced by Joule heating and thermal gradient effects (see below).

The Peltier coefficients represent how much heat is carried per unit charge. Since charge current must be continuous across a junction, the associated heat flow will develop a discontinuity ifandare different. The Peltier effect can be considered as the back-action counterpart to the Seebeck effect (analogous to theback-emfin magnetic induction) if a simple thermoelectric circuit is closed then the Seebeck effect will drive a current, which in turn (via the Peltier effect) will always transfer heat from the hot to the cold junction. The close relationship between Peltier and Seebeck effects can be seen in the direct connection between their coefficients

A typical Peltierheat pumpdevice involves multiple junctions in series, through which a current is driven. Some of the junctions lose heat due to the Peltier effect, while others gain heat. Thermoelectricheat pumpsexploit this phenomenon, as dothermoelectric coolingdevices found in refrigerators.

Fig1.2 An inside view of a TEC (Peltier element).

The Peltier effect is one of the key phenomena (along with theThompson effect) determining the emf generated in a thermocouple used for temperature measurement. For a thermocouple of materials A and B, with one junction at a constant temperature and the other at (absolute) temperature T,

Whereis the thermocouple emf generated at the junction of materials A and B. This equation can be used to calculate the Peltier coefficient for the combination of materials A and B.

The Peltier effect is used inthermoelectric (Peltier) refrigerators or heat pumps. Such devices provide heat removal, sometimes addition, in an easily controlled and reversible device without moving parts. They have been used in space vehicles as well as in a number of small commercial devices for controlling temperature or providing refrigeration, often using semiconductor materials as the thermoelectric elements.

1.5 Thermoelectric cooling

Thermoelectric coolinguses thePeltier effectto create aheatflux between the junctions of two different types of materials. A Peltier cooler, heater, orthermoelectricheat pump is a solid-state activeheat pumpwhich transfers heat from one side of the device to the other, with consumption ofelectrical energy, depending on the direction of the current. Such an instrument is also called a Peltier device, Peltier heat pump, solid state refrigerator, or thermoelectric cooler (TEC). They can be used either for heating or for cooling (refrigeration), although in practice the main application is cooling. It can also be used as a temperature controller that either heats or cools.

The method of thermoelectric cooling (using the Peltier effect) is useful because it can cool an object without any moving pieces or other complex machinery that isolates the cooler from its ambient surroundings. The devices that are constructed to take advantage of this phenomenon are known as Peltier elements, or thermo-electric coolers (TECs). The basic ideas from the simple Peltier elements can be connected in series to construct far more complicated Peltier modules (also known as practical TECs), which have greater cooling capabilities. However, the greatest temperature difference between the heat sink and the cool region for a Peltier device is on the order of 50C.

This technology is far less commonly applied to refrigeration thanvapour-compression refrigerationis. The main advantages of a Peltier cooler (compared to a vapour-compression refrigerator) are its lack of moving parts or circulating liquid, near-infinite life and invulnerability to potential leaks, and its small size and flexible shape (form factor). Its main disadvantage is high cost and poor power efficiency. Many researchers and companies are trying to develop Peltier coolers that are both cheap and efficient.

A Peltier cooler can also be used as athermoelectric generator. When operated as a cooler, a voltage is applied across the device, and as a result, a difference in temperature will build up between the two sides.[3]When operated as a generator, one side of the device is heated to a temperature greater than the other side, and as a result, a difference in voltage will build up between the two sides (theSeebeck effect). However, a well-designed Peltier cooler will be a mediocre thermoelectric generator and vice-versa, due to different design and packaging requirements.

Fig1.3 Thermoelectric cooler

Common uses for Peltier elements include cooling computer components, especially the CPU.

1.6 MATERIAL USED FOR MAKING PELTEIR ELEMENT

The most common combination of materials in the thermocouples of Peltier elements (TECs) is the two semiconductors Bismuth and Telluride. Generally, a TEC has an array of cubes or pellets made of the semiconductors, each of which is in contact with the radiators on the hot and cold side of the Peltier element. These cubes are "doped" -- that is to say that extra impurities are added so that there are extra or fewer free electrons in each cube. The semiconductor cubes with extra free electrons (and thus carry mainly negative charge) are known as N-type semiconductors, while those with few free electrons (and carry mainly positive charge) are P-type semiconductors. The pairs of P and N semiconductor cubes are set up and connected in an array so that the pairs have an electrical series connection, but a thermal parallel connection. When a current is applied to this system (the TEC), the way the current flows through the semiconductors induces a temperature difference, and causes the heat-sink side of the Peltier element to heat up, and the cold side to cool (or cooling whatever is in thermal contact with that side).

Fig1.4 Peltier element, with ceramic plates to partially insulate the inside from the outer environment

"Normal" Peltier elements are roughly a few centimetres thick and a few millimetres or centimetres on a side. To obtain greater cooling abilities, the individual elements are connected in stacks, or they can be connected in some combination of series and parallel electrical connections.

The heat-sink side of the TEC gets very hot, so it is necessary to have a fan and/or some sort of radiator to dissipate this heat. Otherwise, the entire TEC would begin to heat up, and pieces would fuse together.

Fig 1.5 A Peltier module with a fan and radiator todissipate heat from the heat sink.

1.7 THERMOELECTRIC COOLING AND ITS ADVANTAGE OVER THE CONVENTIONAL REFRIGERATION

Refrigeration means removal of heat from a substance or space in order to bring it to a temperature lower than those of the natural surroundings. In this context, my topic, Thermoelectric Refrigeration aims at providing cooling effect by using thermoelectric effects rather than the more prevalent conventional methods like those using the vapour compression cycle or the gas compression cycle.

There are 5 thermoelectric effects and these are observed when a current is passed through a thermocouple whose junctions are at different temperatures. These phenomenons are the Seeback effect, the Peltier effect, the Joulean effect, the conduction effect, and the Thomson effect. Thermoelectric cooling, also called "Peltier Effect", is a solid-state method of heat transfer through dissimilar semiconductor materials. It is based on the thermoelectric effect known as Peltier Effect according to which if current is passed through a thermocouple, then the heat is absorbed at one junction of the thermocouple and liberated at the other junction. So by using the cold junction of the thermocouple as the evaporator, a heat sink as the condenser and a DC power source as the compressor of the refrigerator, cooling effect can be provided. The coefficient of performance of compression refrigerators decrease with the decrease of its capacity. Therefore, when it is necessary to design a refrigerator for cooling a chamber of only a few litres capacity, thermoelectric cooling is always preferable. Also for controlling the temperature of small units, thermoelectric cooling has no competition from existing refrigerators of the conventional types. The importance of thermoelectric cooling can be best understood by examining other various advantages it offers over the conventional methods of refrigeration

There is ease of interchanging the cooling and heating functions by reversing the direction of current in the thermocouple

Thermoelectric systems are vibration less and have no moving parts. Hence there is no problem of wear and noise.

There is no problem of containment and pollution because no refrigerant or chemical is used.

Since there is no bulky equipment it provides ease of miniaturization for small capacity systems.

The capacity can be controlled easily by varying the current and hence the amount of heat absorbed or evolved at the junctions.

The system is highly reliable ( with a life of > 250,000 hours)

This system also has the capacity to operate under various values of gravity (including zero gravity) and in any position.

Thus, thermoelectric cooling has a great relevance in todays time.

In vaccine fridge which is used to hold the polio vaccine various heat transfer are taken into consideration and material of the vaccine box is selected in such a way that these heat transfer minimizes. The heat transfer which are taking place generally are:

a. Conduction

On a microscopic scale, heat conduction occurs as hot, rapidly moving or vibrating atoms and molecules interact with neighbouring atoms and molecules, transferring some of their energy (heat) to these neighbouring particles. In other words, heat is transferred by conduction when adjacent atoms vibrate against one another, or as electrons move from one atom to another. Conduction is the most significant means of heat transfer within a solid or between solid objects inthermal contact. Fluidsespecially gasesare less conductive.Thermal contact conductanceis the study of heat conduction between solid bodies in contact.[9]

Steady state conduction(seeFourier's law) is a form of conduction that happens when the temperature difference driving the conduction is constant, so that after an equilibration time, the spatial distribution of temperatures in the conducting object does not change any further.[10]In steady state conduction, the amount of heat entering a section is equal to amount of heat coming out.[9]

Transient conduction(seeHeat equation) occurs when the temperature within an object changes as a function of time. Analysis of transient systems is more complex and often calls for the application of approximation theories or numerical analysis by computer.[9]

b. Convection

The flow of fluid may be forced by external processes, or sometimes (in gravitational fields) by buoyancy forces caused when thermal energy expands the fluid (for example in a fire plume), thus influencing its own transfer. The latter process is often called "natural convection". All convective processes also move heat partly by diffusion, as well. Another form of convection is forced convection. In this case the fluid is forced to flow by use of a pump, fan or other mechanical means.

Convective heat transfer, or convection, is the transfer of heat from one place to another by the movement offluids, a process that is essentially the transfer of heat viamass transfer. Bulk motion of fluid enhances heat transfer in many physical situations, such as (for example) between a solid surface and the fluid.[11]Convection is usually the dominant form of heat transfer in liquids and gases. Although sometimes discussed as a third method of heat transfer, convection is usually used to describe the combined effects of heat conduction within the fluid (diffusion) and heat transference by bulk fluid flow streaming.[12]The process of transport by fluid streaming is known as advection, but pure advection is a term that is generally associated only with mass transport in fluids, such as advection of pebbles in a river. In the case of heat transfer in fluids, where transport by advection in a fluid is always also accompanied by transport via heat diffusion (also known as heat conduction) the process of heat convection is understood to refer to the sum of heat transport by advection and diffusion/conduction.

Free, or natural, convection occurs when bulk fluid motions (steams and currents) are caused by buoyancy forces that result from density variations due to variations of temperature in the fluid.Forcedconvection is a term used when the streams and currents in the fluid are induced by external meanssuch as fans, stirrers, and pumpscreating an artificially induced convection current.

c. Radiation

Thermal radiationoccurs through avacuumor anytransparentmedium(solidorfluid). It is the transfer of energy by means ofphotonsin electromagneticgoverned by the same laws.[14]Earth's radiation balancedepends on the incoming and the outgoing thermal radiation,Earth's energy budget.Anthropogenicperturbations in the climate system are responsible for a positiveradiative forcingwhich reduces the net longwave radiation loss out toSpace.

Thermal radiationis energy emitted by matter as electromagnetic waves, due to the pool ofthermal energyin all matter with a temperature aboveabsolute zero. Thermal radiation propagates without the presence of matter through thevacuumof space.[15]

Thermal radiation is a direct result of the random movements of atoms and molecules in matter. Since these atoms and molecules are composed of charged particles (protonsandelectrons), their movement results in the emission ofelectromagnetic radiation, which carries energy away from the surface.

The Stefan-Boltzmann equation, which describes the rate of transfer of radiant energy, is as follows for an object in a vacuum:

Q=

For Radiative transfer between two objects, the equation is as follows:

Q=

Where Q is the rate of heat transfer, is theemissivity(unity for ablack body), is theStefan-Boltzmann constant, and T is the absolute temperature (in Kelvin or Rankine). Radiation is typically only important for very hot objects, or for objects with a large temperature difference.

1.8Objective

In the vaccine fridge the conduction and convection heat transfer of ice with the surrounding is resisted but the problem is with the radiation heat transfer which occur between the ice kept inside the vaccine fridge and the ambient atmosphere which is at much higher temperature than the ice due to this temperature gradient heat transfer occurs which increases the temperature of the vaccine fridge. So to avoid this heat transfer radiation heat transfer need to be minimized. By the help of Pelteir crystal we will try to maintain a temperature of 10 to 15 degree celcius in between the vaccine box and decrease the radiation heat transfer.

The objective of this project is to make a vaccine fridge based on thermoelectric cooling by the help of Pelteir crystal. This will reduce the radiation heat transfer from the walls of the vaccine fridge and will increase the life of vaccine in the fridge by Preserve the ice 3 or 4 times longer than ordinary vaccine fridge.

Chapter 2

LITERATURE REVIEW

2.1 Literature survey

[1] Friedemann Vlklein (1974) presentsthe modelling of a thermoelectric cooler, which is designed by using micromachining and thin film technology. The cooler fabrication is compatible with standard semiconductor technology. Therefore, it can be integrated in microelectronic circuits. The most important parameters of the device like cooling power, maximum temperature difference and optimum current density are calculated. By using thermoelectric thin films with high efficiency and very thin SiC/Si3N4-membranes, a cooling power of a few milliWatts or maximum temperature difference of 3050 K can be achieved.

[2]T. C. Harman,J. H. CahnandM. J. Logan(2004) used a special technique for the accurate measurement ofthermal conductivity. The method involves use of the Peltier heat to maintain a temperature gradient along the specimen. Straightforward measurements allow calculation of the absolute value of thethermoelectricpower,thermal conductivity,andelectrical resistivity.An especially useful feature of the method is that thethermoelectricfigure of merit is given in terms of the ratio of two voltages. The theory is presented for the case in which theradiative heat transferis important. The method has been tested experimentally at 300K only, butanalysissuggests that accurate measurements of thermal conductivitycan be made by this technique on lowthermal conductivitymaterialsof small dimensions up to 1000K.

[3]Eduard Zwack (1988) used a cooling device which is realized by a Peltier element and is assigned to a crystal oscillator and driven by a processor with the assistance of a temperature sensor such that the crystal exhibits one of two selected temperatures lying closest to the ambient temperature. A compensation value is stored in the memory of the processor for each of the crystal temperatures selected from an operating temperature range. This compensation value effects the compensation of the frequency deviations of the crystal oscillator that are caused by temperature fluctuations.

[4] Catherine Hildbrand (2000) presented idea using adsorptive solar refrigerator. The adsorption pair is silica gel+water. The machine does not contain any moving parts, does not consume any mechanical energy except for experimental purposes and is relatively easy to manufacture. Cylindrical tubes function as both the adsorber system and the solar collector (flat-plate, 2 m2double glazed); the condenser is air-cooled (natural convection) and the evaporator contains 40 l of water that can freeze. This ice functions as a cold storage for the cabinet (320 l).

2.2 Conclusion to Literature Review

From the above the literature survey we conclude that thermoelectric effect is an effective cooling method which can be use in vaccine box to maintain low temperature of ice for long period than the conventional one. Thermoelectric cooling is economical and requires very less current to give cooling effect which makes it suitable for solar operated. Also as thermoelectric cooler have very less movement of mechanical component its life span is more than the other refrigeration system of same size. So from all the point mention above we can give final conclusion that thermoelectric cooler are most suitable for our Pelteir based vaccine fridge.

2.3 Problem formulation

In the vaccine fridge the conduction and convection heat transfer of ice with the surrounding is resisted but the problem is with the radiation heat transfer which occur between the ice kept inside the vaccine fridge and the ambient atmosphere which is at much higher temperature than the ice due to this temperature gradient heat transfer occurs which increases the temperature of the vaccine fridge As vaccine fridge is made with a thermally insulated material so only radiation heat transfer can be the only cause melting of ice inside the box. By the use of Pelteir crystal in vaccine fridge the radiation heat transfer can be reduced by reducing the temperature gradient.

Chapter 3

Methodology

3.1 Various steps involved in making vaccine fridge using Pelteir crystal

1. Vaccine box of material is made of dimension.

2. Outer box which will cover the vaccine box of dimension is made.

3. Pelteir crystal of dimension and made of?? Semiconductor is used for cooling purpose.

4. 2dc motors are used one for exhaust fan and other for the circulating fan of 3watt each.

5. To give power to this whole setup 2 solar plate of total 6watt capacity used.

3.2 material used for making vaccine fridge using Pelteir crystal

1. To make the body minimum density fibre board used (6mm*4mm).

2. Copper pipe (6mm*8mm).

3. 3 volt dc brushed motor (2).

4. Pelteir crystal (40mm*40mm).

5. Heat sink

6. Heat sensor(tungsten filament based heat sensor)

7. MPPT (Maximum power point tracking) circuit.

8. Lead acid dry battery.(4 volts ,1.5Amphere)

9. 555 timer

10. 1M ohm potentiometer

11. Carbon film resistor (1k ohm,10k ohm,330 ohm)

12. Ceramic capacitor

13. Electrolytic capacitor

14. Copper wire used (3) for making circuit in PCB.

Description of some important parts of the vacuum fridge using Pelteir crystal

1. Solar Panel

Asolar panelis a set of solar photovoltaicmoduleselectrically connected and mounted on a supporting structure. A photovoltaic module is a packaged, connected assembly ofsolar cells. The solar panel can be used as a component of a larger photovoltaic system to generate and supply electricityin commercial and residential applications. Each module is rated by itsDCoutput power under standard test conditions (STC), and typically ranges from 100 to 320 watts. Theefficiencyof a module determines the area of a module given the same rated output - an 8% efficient 230 watt module will have twice the area of a 16% efficient 230 watt module. A single solar module can produce only a limited amount of power; most installations contain multiple modules. Aphotovoltaic systemtypically includes a panel or an array of solar modules, aninverter, and sometimes abatteryand/solar trackerand interconnection wiring.

2. Battery

A battery cell consists of two lead plates a positive plate covered with a paste of lead dioxide and a negative made of sponge lead, with an insulating material (separator) in between. The plates are enclosed in a plastic battery case and then submersed in an electrolyte consisting of water and sulphuric acid.

3. 555 Timer Circuit

ManyDC motor speed controlcircuits have been published here but this is the first one using NE555 timer IC. In addition to controlling the motors speed its direction of rotation can be also changed using this circuit.

4. MPPT Circuit

Controller's main function is to make solar power system is always in the vicinity of the maximum power generation in order to obtain maximum efficiency. MPPT stands for maximum power point tracker. Inside these controllers is a high efficiency, DC to DC voltage converter that pulls the maximum load from a solar panel and then, using a pre-programmed algorithm that accounts for temperature, charge state along with power draw, pushes the power into the battery array.

3.2 Working

Here in the setup solar plate of 6watt capacity is been used for giving power to two 3v dc motor which are used for circulation of the cold air in the body and other is used as exhaust fan for throwing out the hot air from the hot side of the crystal to the atmosphere which is acting as a heat sink. Pelteir crystal is used to make the cold atmosphere in setup .Pelteir crystal is powered by the battery which will be charged by the solar panel. Also a timer circuit is installed which after certain interval of time will turn on the current in the Pelteir crystal and maintain the temperature of the setup.

When an electrical current is applied across the junction of two dissimilar metals, heat is removed from one of the metals and transferred to the other. This is the basis of thermoelectric refrigeration. Thermoelectric modules are constructed from a series of tiny metal cubes of dissimilar exotic metals which are physically bonded together and connected electrically. When electrical current passes through the cube junctions, heat is transferred from one metal to the other. Solid-state thermoelectric modules are capable of transferring large quantities of heat when connected to a heat absorbing device on one side and a heat dissipating device on the other. The internal aluminium cold plate fins absorb heat from the contents, polio vaccine , and the thermoelectric modules transfer it to heat dissipating fins under the control panel. Here, a small fan helps to disperse the heat into the air. The system is totally environmentally friendly and contains no hazardous gases, nor pipes nor coils and no compressor. The only moving part is the small 3-volt fan. Thermoelectric modules are too expensive for normal domestic and commercial applications which run only on regular household current. They are ideally suited to recreational applications because they are lightweight, compact, and insensitive to motion or tilting, have no moving parts, and can operate directly from 6-volt batteries.

Chapter 4

Result and Discussion

4.1 Result and discussion

The system is efficient enough to maintain approximately 10 to 15 degree less temperature inside the box so that heat transmission through radiation could be minimised. In the system we are using peltier crystal as a localized cooling agent which maintains temperature as accordance with the voltage provided into it. To control the system a simplest circuit is developed which contain a programmed control or analogous control along with timer and related components.

4.1.1 Advantages of the system

1) Simplest circuitry

2) Portable and easy to carry

3) Totally non conventional energy operated

4) Due to lack of any coolant it is very cheap in maintenance

5) Easy to repair

6) Light weight and cooling remain last longer.

4.1.2 Limitations

It cannot act as a fridge without ice input, because it is used to maintain less temperature so that the ice box remain chilled and the melting rate of ice could be slowed down.

Chapter 5

Conclusion and future scope

5.1 Conclusion

By the use of Pelteir crystal we are able to reduce the radiation heat transfer between the ice in the vaccine box and ambient atmosphere and from this vaccine fridge using Pelteir crystal we can preserve polio vaccine for 4 to 6 hours more than the normal vaccine fridge. This setup is Ecofriendly, Economical and can be easily make.

5.2 Future scopes

Polio is still a very big problem for us and to eliminate it we need vaccine .these vaccine need some lower temperature otherwise they will expire. Present conventional vaccine box can only preserve vaccine for 6 hours maximum. Due to such type of constraint we cant provide vaccine to the village people where this polio problem is fatal. So by the use of this new modified vaccine box we can increase the life of vaccine and can easily provide vaccine to villages which are far away from main city. Future scope of this project is very dynamic and real life based and by implementing this project in large scale we can eliminate polio virus from all rural areas of India completely.

Chapter 6

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