Final Project Report

Bharati Vidyapeeth’s College of Engineering A-4,Paschim Vihar New Delhi-110063 Guru Gobind singh Indraprastha University, Delhi-06 (2007-2011)

Compressor-less Portable Refrigerator Submitted in partial fulfillment of requirements for the award of the degree of Bachelor of Technology in Electrical and Electronics Engineering.

Guide: Prof. Sudha David

Submitted By Karan Sharma(0601154907) Yash Kumar (0081154907) Bhaskar Sharma(0851154907) Vasu Luthra (0331154907)

CERTIFICATE This is to certify that the project report titled “Compressor-less Portable Refrigerator” has been submitted by the following students :

Karan Sharma

0601154907

Yash Kumar

0081154907

Vasu Luthra

0331154907

Bhaskar Sharma

0851154907

in partial fulfillment of the requirement for the award of the B.Tech. degree in Electrical & Electronics Engineering (EEE) at Bharati VIdyapeeth’s College of Engineering, GGSIP University, Delhi. Date: Project Guide

Prof. Sudha David [EEE Dept.] (Bharati Vidyapeeth’s College of Engineering)

ACKNOWLEDGEMENT We would like to articulate our profound gratitude and indebtedness to the project guide Prof. Sudha David, who has always been a constant motivation and guiding factor throughout the project time in and out as well. It has been a great pleasure for us to get an opportunity to work under her and complete the project successfully. An undertaking of this nature could never have been attempted with our reference to and inspiration from the works of others whose details are mentioned in references section. We acknowledge our indebtedness to all of them.

Karan Sharma (0601154907)

Yash Kumar (0081154907)

Bhaskar Sharma (0851154907)

Vasu Luthra (0331154907)

AIM: To design and implement a compressor-less portable refrigerator. MOTIVATION: This project is the first step in the development of an electric field refrigeration unit. Cooling devices in the future may lose their compressor and coils of piping to become solid state.

INDEX

INTRODUCTION

From keeping our veggies fresh, to storing our favorite ice creams and juices, refrigerators have become essential for modern day living. The first refrigerators, so to say, were built as ice houses. These buildings consisted of man-made underground chambers, which were built close to natural sources of winter ice such as freshwater lakes. During winter, this ice and snow would be packed into the ice house along with straw or sawdust that was used for insulation. The ice house kept the ice intact for several months on end, even through summer. Many countries claim to be the home of the refrigerator. Over the years, refrigerator technology has evolved in leaps and bounds. One of the first home refrigeration units was installed at Biltmore Estate in North Carolina in around 1895. That same year, the first commercial refrigeration unit was opened by the Vestey Brothers in London. Modern day refrigerators primarily work on electric power, although some of the older models use gas as a source of energy. Today, a domestic refrigerator is present in 99.5% of American homes. It works using phase change heat pumps operating in a refrigeration cycle. An industrial refrigerator is simply a refrigerator used in an industrial setting, usually in a restaurant or supermarket where large quantities of food stocks are stored. They may consist of a cooling compartment (a larger refrigerator), a freezing compartment (a freezer) or both. The dual compartment was introduced commercially by General Electric in 1939. Some refrigerators are now divided into four zones for the storage of different types of food at different temperature.

Conventional cooling systems Refrigerators or air conditioners — rely on the properties of gases to cool and most systems use the change in density of gases at changing pressures to cool. The coolants commonly used are either harmful to people or the environment. Freon, one of the fluorochlorocarbons banned because of the damage it did to the ozone layer, was the most commonly used refrigerant. Now, a variety of coolants is available. Nevertheless, all have problems and require energy-eating compressors and lots of heating coils.

BLOCK DIAGRAM

LIST of Components 1. Insulating box 2. DC Battery 3. Aluminum Container 4. Selector Switch 5. Exhaust Fan 6. AC power Supply 7. Pelteir Junction Apparatus

Material used for insulation  The material used for the assembly components deserves careful thought. The heat sink and cold side mounting surface should be made out of materials that have a high thermal conductivity (i.e., copper or aluminum) to promote heat transfer.



However, insulation and assembly hardware should be made of materials that have low thermal conductivity (i.e., polyurethane foam and stainless steel) to reduce heat loss.

 Environmental concerns such as humidity and condensation on the cold side can be alleviated by using proper sealing methods. A perimeter seal (Figure 4) protects the couples from contact with water or gases, eliminating corrosion and thermal and electrical shorts that can damage the thermoelectric module. Materials used to built thermocouples. 

Silicon, Bismuth, Nickel ,Cobalt ,Palladium, Platinum, Uranium, Copper, Manganese, Titanium, Mercury, Lead , Tin, Chromium, Molybdenum ,Rhodinium ,Iridium ,Gold ,Silver, Aluminum, Zinc, Tungsten, Cadmium Iron, Arsenic, Tellurium, Germanium

Theoretical Principle PELTIER EFFECT The thermoelectric refrigerator works on the PELTIER effect that The Peltier–Seebeck effect, or thermoelectric effect, is the direct conversion of thermal differentials to electric voltage and vice versa. Related effects are the Thomson effect and Joule heating. The Peltier–Seebeck and Thomson effects are reversible (in fact, the Peltier and Seebeck effects are reversals of one another); Joule heating cannot be reversible under the laws of thermodynamics.

Seebeck effect

 The Seebeck effect is the conversion of temperature differences directly into

electricity. This effect was first discovered, accidentally, by the German physicist Thomas Johann Seebeck in 1821, who found that a voltage existed between two ends of a metal bar when a temperature difference ΔT existed in the bar.  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 to flow in the conductors if they form a complete loop. The voltage created is of the order of several microvolt per degree difference.

Thermo-electric cooling  Thermoelectric coolers are solid state heat pumps used in applications where temperature stabilization, temperature cycling, or cooling below ambient are required.  There are many products using thermoelectric coolers, including CCD cameras (charge coupled device), laser diodes, microprocessors, blood analyzers and portable picnic coolers.  The typical thermoelectric module is manufactured using two thin ceramic wafers with a series of P and N doped bismuth-telluride semiconductor material sandwiched between them

 The N type material has an excess of electrons, while the P type material has a deficit of electrons. One P and one N make up a couple, as shown in Figure 1. The thermoelectric couples are electrically in series and thermally in parallel. A thermoelectric module can contain one to several hundred couples.

Designing of thermal emf refrigeration Th = Tamb + (O) *(Qh) where TH=The temperature of hot side Tamb=The ambient temperature O=thermal resistance of heat exch Qh=heat realeased heat released to the hot side of the thermoelectric (watts). Qh = Qc + Pin Where Qh = the heat released to the hot side of the thermoelectric (watts). Qc = the heat absorbed from the cold side (watts). Pin = the electrical input power to the thermoelectric (watts).  The temperature difference across the thermoelectric (T) relates to Th and Tc according to Equation 

T = Th – Tc

 The thermoelectric performance curves in Figures 2 and 3 show the relationship between T and the other parameters.

 Estimating Qc, the heat load in watts absorbed from the cold side is difficult, because all thermal loads in the design must be considered. Among these thermal loads are:  Active:

I2R

heat

load

from

the

electronic

devices

Any load generated by a chemical reaction  Passive: Radiation (heat loss between two close objects with different temperatures) Convection (heat loss through the air, where the air has a different temperature than the

object)

Insulation

Losses

Conduction

Losses

(heat

loss

through

leads,

screws,

etc.)

Transient Load (time required to change the temperature of an object)  As the thermoelectric operates, the current flowing through it has two effects:  (1) the Peltier Effect (cooling) and  (2) the Joulian Effect (heating).  We know that joulian effect is proportional to the squire of the current so heating effect will dominates the cooling effect that why we can not increase the current to a maximum value called Imax for themo-electric. 

The thermal resistance of the heat sink causes a temperature rise above ambient. If the thermal resistance of the heat sink is unknown, then estimates of acceptable temperature rise above ambient are:

 Natural Convection20°C to 40°C  Forced Convection10°C to 15°C  Liquid Cooling2°C to 5°C (rise above the liquid coolant temperature)

 As we have done our design on a Melcor thermoelectric . The specifications for the are(these specifications are at Th = 25°C): 1. Qmax = 51.4 watts 2. Vmax = 15.4 volts 3. Imax = 6.0 amps 4. Tmax

=

67°C

To determine if this thermoelectric is appropriate for this application, it must be shown that the parameters T and Qc are within the boundaries of the performance curves. 5. Our main aim to maintain the temperature of container 5°C which contain 16 litres of air in 0.5minute. we know 1000litres =1m3 16 litres=0.016 m3 density of air=1.293 kg/m3. mass of air =0.016*1.293=0.020688kg specific heat of air=1kJ/Kg°k As

Q=m*s*(th-tc)=0.020688*1000*(35-5)=620.64 J

this is maintain in 0.5minutes so Required power=620.64/(0.5*60)=22 watts (As we assume that the ambient temperature Tamb=25c the rise in the temperature due to sink resistance is 10c

So final temperature will be =25+10=35c)

Performance Curve (T vs. Qc)

Performance Curve (T vs. Voltage )

So by the graph maximum current = 3.6amp . Corresponding voltage by graph between temperature and voltage Voltage=10v Now we will determine the corresponding value of temperature by these values of current and voltage. We know that the temperature at hot side Th = Tamb + (O) *(Qh) Value of heat released at hot side Qh = Qc + Pin Now Pin that is the input power to produce this effect is Pin=V*I V=10volt I=3.6amp Pin=10*3.6=36watt And Qh=Qc+Pin =22+36 =58 watts And

Th= Tc +Rcon*Qh

Now the temperature is also rise due to its convective resistance , we assume that the convective resistance of the sink is 0.15°C So

Th=25+0.15*58=33.7°C

The calculated Th is close enough to the original estimate of Th, to conclude that the CP1.4-127-06L thermoelectric will work in the given application

Single Stage vs. Multistage  Given the hot side temperature, the cold side temperature and the heat load, a suitable thermoelectric can be chosen. If T across the thermoelectric is less than 55°C, then a single stage thermoelectric is sufficient. The theoretical maximum temperature difference for a single stage thermoelectric is between 65°C and 70°C. If T is greater than 55°C, then a multistage thermoelectric should be considered. A multistage thermoelectric achieves a high T by stacking as many as six or seven single stage thermoelectric on top of each other.

Applications 1. Domestic Household Refrigerator

2. Commercial Cold Storage 3. Cooling Tower of Nuclear Power Plant 4. Small size ice boxes in vehicles

Future Developments 1. Ferro

electric polymers trifluoroethylene) and chlorofluoroethylene.

polarpolymers include poly(vinylidene

poly(vinylidene fluoridefluoride-trifluoroethylene)-

2. Magnetic field refrigeration, but electricity is more convenient. 3. Flat panel refrigerator. 4.

References 1. Qiming

Zhang, distinguished professor of electrical engineering Penn State researchers.

2. Article Source: http://EzineArticles.com/253045 3. The U.S. Department of Energy.