compressor less refrigerator.doc

8/10/2019 compressor less refrigerator.doc

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AIM: -Compressor less Refrigerator

Objective: -1. To fabricate an aluminum assembly container inside the

plastic Jar/Can suitable to store food stuff inside.

2. To make a space (at any one side of the above encloses to

fit !"#T$"R J%&CT$'& !!RT%) in this *ith no air

gap remains open.

+. To fi, a small e,haust air fan at the outer surface above

the !"#T$"R -unction appratus.

. To fabricate assemble a 12 0 C !o*er supply to

provide po*er )ource for this *hole set up and battery

charging (optional.

. To Connect a change over s*itch for polarity reversing

for cooling heating effect inside the enclose assembly.

3or making compressor less refrigerator *e use !"#T$"R J%&CT$'&

method. To make a space (at any one side of the above encloses to fit

!"#T$"R J%&CT$'& !!RT%) in this *ith no air gap remains open.

To fabricate assemble a 12 0 C !o*er supply.


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BLOCK DIAGRAM


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SPECIFICATION

0olume4

15litres

0oltage4

C 1206 C 1778270

!o*er consumption4

C4 Cold mode4 9:;/8272:;/827


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PELTIER EFFECT

INTRODUCTION

The !eltier?)eebeck 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 !eltier?)eebeck and

Thomson effects are reversible (in fact@ the !eltier and )eebeck effects are

reversals of one another6 Joule heating cannot be reversible under the la*s

of thermodynamics.

Seebeck effect

The )eebeck effect is the conversion of temperature differences directly into

electricity. This effect *as first discovered@ accidentally@ by the Aerman

physicist Thomas Johann )eebeck in 1921@ *ho found that a voltage e,isted

bet*een t*o ends of a metal bar *hen a temperature difference BT e,isted

in the bar.

=e also discovered that a compass needle *ould be deflected *hen a closed

loop *as formed of t*o metals *ith a temperature difference bet*een the-unctions. This is because the metals respond differently to the temperature

difference@ *hich creates a current loop@ *hich produces a magnetic field.

The effect is that a voltage@ the thermoelectric "3@ is created in the

presence of a temperature difference bet*een t*o different metals or

semiconductors. This causes a continuous current to flo* in the conductors

if they form a complete loop. The voltage created is of the order of several

microvolts per degree difference.


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$n the circuit4

(*hich can be in several different configurations and be governed by the

same eDuations@ the voltage developed can be derived from4

)and )Eare the )eebeck coefficients(also called thermoelectric po*eror

thermopo*er of the metals and E@ and T1and T2are the temperatures ofthe t*o -unctions. The )eebeck coefficients are non8linear@ and depend on

the conductorsF absolute temperature@ material@ and molecular structure. $f

the )eebeck coefficients are effectively constant for the measured

temperature range@ the above formula can be appro,imated as4

Thus@ a thermocouple *orks by measuring the difference in potential caused

by the dissimilar *ires. $t can be used to measure a temperature differencedirectly@ or to measure an absolute temperature@ by setting one end to a

kno*n temperature. )everal thermocouples in series are called a thermopile.

This is also the principle at *ork behind thermal diodes and thermoelectric

generators (such as radioisotope thermoelectric generators or RTAs *hich

are used for creating po*er from heat differentials.
http://en.wikipedia.org/wiki/Seebeck_coefficienthttp://en.wikipedia.org/wiki/Thermoelectric_powerhttp://en.wikipedia.org/wiki/Thermopowerhttp://en.wikipedia.org/wiki/Seebeck_coefficienthttp://en.wikipedia.org/wiki/Thermoelectric_powerhttp://en.wikipedia.org/wiki/Thermopower


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The )eebeck effect is due to t*o effects4 charge carrier diffusion and phonon

drag. $f both connections are held at the same temperature@ but one

connection is periodically opened and closed@ an C voltage is measured@

*hich is also temperature dependent. This application of the Gelvin probe is

sometimes used to argue that the underlying physics does only need one

-unction. nd this effect is still visible if the *ires only come close@ but do

not touch@ thus no diffusion is needed.

The!"#"$e

The thermopo*er@ or thermoelectric po*er@ or )eebeck coefficient of a

material is a measure of the magnitude of an induced thermoelectric voltage

in response to a temperature difference across that material. The

thermopo*er has units of (0 / G. The term thermopo*er is a misnomersince it measures the voltage or electric field (not the electric po*er

induced in response to a temperature difference. n applied temperature

difference causes charged carriers in the material@ *hether they are electrons

or holes@ to diffuse from the hot side to the cold side@ similar to a classical

gas that e,pands *hen heated. obile 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. )ince a

separation of charges also creates an electric potential@ the buildup ofcharged carriers onto the cold side eventually ceases at some ma,imum

value since there e,ists an eDual amount of charged carriers drifting back to

the hot side as a result of the electric field at eDuilibrium. 'nly 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.

$ncidentally the thermopo*er also measures the entropy per charge carrier in

the material.

An Introduction toThermoelectric Coolers


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Sara Godfrey, Melcor Corporation

3igure 14 Cross )ection of a Typical T" Couple

I%t"&'cti"%

Thermoelectric coolers are solid state heat pumps used in applications *here

temperature stabiliHation@ temperature cycling@ or cooling belo* ambient are

reDuired. There are many products using thermoelectric coolers@ including

CC cameras (charge coupled device@ laser diodes@ microprocessors@ blood

analyHers and portable picnic coolers. This article discusses the theory

behind the thermoelectric cooler@ along *ith the thermal and electrical

parameters involved.

("$ the The!"e)ectic *"k+ , , ,

Thermoelectrics are based on the !eltier "ffect@ discovered in 19+@ by

*hich C current applied across t*o dissimilar materials causes a

temperature differential. The !eltier "ffect is one of the three thermoelectric

effects@ the other t*o are kno*n as the )eebeck "ffect and Thomson "ffect.

:hereas the last t*o effects act on a single conductor@ the !eltier "ffect is a

typical -unction phenomenon. The three effects are connected to each other

by a simple relationship.

PO*ER SUPPL

$n flo* in one direction only. :hen the anode of the diode is positive

*ith respect to its cathode@ it is for*ard biased@ allo*ing current to flo*. Eut

*hen its anode is negative *ith alternating current the electron flo* is


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alternate@ i.e. the electron flo* increases to ma,imum in one direction@

decreases back to Hero. $t then increases in the other direction and then

decreases to Hero again. irect current flo*s in one direction only. Rectifier

converts alternating current to respect to the cathode@ it is reverse biased and

does not allo* current to flo*. This unidirectional property of the diode is

useful for rectification. single diode arranged back8to8back might allo*

the electrons to flo* during positive half cycles only and suppress the

negative half cycles. ouble diodes arranged back8to8back might act as full

*ave rectifiers as they may allo* the electron flo* during both positive and

negative half cycles. 3our diodes can be arranged to make a full *ave bridge

rectifier. ifferent types of filter circuits are used to smooth out the

pulsations in amplitude of the output voltage from a rectifier. The property

of capacitor to oppose any change in the voltage applied across them by

storing energy in the electric field of the capacitor and of inductors to oppose

any change in the current flo*ing through them by storing energy in themagnetic field of coil may be utiliHed. To remove pulsation of the direct

current obtained from the rectifier@ different types of combination of

capacitor@ inductors and resistors may be also be used to increase to action of

filtering.

NEED OF PO*ER SUPPL

!erhaps all of you are a*are that a Ipo*er supply is a primaryreDuirement for the ITest Eench of a home e,perimenters mini lab.

battery eliminator can eliminate or replace the batteries of solid8state

electronic eDuipment and the eDuipment thus can be operated by 2+7v .C.

mains instead of the batteries or dry cells. &o*adays@ the use of commercial

battery eliminator or po*er supply unit has become increasingly popular as

po*er source for household appliances like transreceivers@ record player@

cassette players@ digital clock etc.

TRANSFORMER

PRINCIPLE OF THE TRANSFORMER:-


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Two coils are wound over a Core such that they are

magnetically coupled. The two coils are known as the

primary and secondary windings.

In a Transformer,an iron core is used. The couplingbetween the coils is source of making a path for the

magnetic ux to link both the coils. A core as in g.2 is used

and the coils are wound on the limbs of the core. ecause of

high permeability of iron! the ux path for the ux is only in

the iron and hence the ux links both windings. "ence there

is very little #leakage ux$. This term leakage ux denotes

the part of the ux! which does not link both the coils! i.e.!

when coupling is not perfect. %n the high fre&uency

transformers! ferrite core is used. The transformers may be

step'up! step'down! fre&uency matching! sound output!

amplier driver etc. The basic principles of all the

transformers are same.

MINIATURE TRANSFRMER


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CN!ENTINA" #$ER TRANSFRMER

(EAT SINK

he.t +i%k (or he.t+i%k is an environment or ob-ect that absorbs and

dissipates heat from another ob-ect using thermal contact (either direct or

radiant. =eat sinks are used in a *ide range of applications *herever

efficient heat dissipation is reDuired6 ma-or e,amples include refrigeration@

heat engines@ cooling electronic devicesand lasers.

C!% heat sink *ith fan attached

DIODE

The simplest semiconductor device is made up of asandwich of ('type semiconducting material! with contactsprovided to connect the p'and n'type layers to an externalcircuit. This is a )unction *iode. %f the positive terminal of thebattery is connected to the p'type material +cathode, andthe negative terminal to the -'type material +Anode,! a large
http://en.wikipedia.org/wiki/Thermal_contacthttp://en.wikipedia.org/wiki/Refrigerationhttp://en.wikipedia.org/wiki/Heat_engineshttp://en.wikipedia.org/wiki/Thermal_management_of_electronic_devices_and_systemshttp://en.wikipedia.org/wiki/Laserhttp://en.wikipedia.org/wiki/Image:AMD_heatsink_and_fan.jpghttp://en.wikipedia.org/wiki/Image:Flow-vector-heat-sink-fluid-WBG.jpghttp://en.wikipedia.org/wiki/Thermal_contacthttp://en.wikipedia.org/wiki/Refrigerationhttp://en.wikipedia.org/wiki/Heat_engineshttp://en.wikipedia.org/wiki/Thermal_management_of_electronic_devices_and_systemshttp://en.wikipedia.org/wiki/Laser


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current will ow. This is called forward current or forwardbiased.

%f the connections are reversed! a very little current willow. This is because under this condition! the p'type

material will accept the electrons from the negative terminalof the battery and the -'type material will give up its freeelectrons to the battery! resulting in the state of electricale&uilibrium since the -'type material has no more electrons.

Thus there will be a small current to ow and the diode iscalled everse biased.

Thus the *iode allows direct current to pass only in onedirection while blocking it in the other direction. (ower

diodes are used in concerting AC into *C. %n this! current willow freely during the rst half cycle +forward biased, andpractically not at all during the other half cycle +reversebiased,. This makes the diode an e/ective rectier! whichconvert ac into pulsating dc. 0ignal diodes are used in radiocircuits for detection. 1ener diodes are used in the circuit tocontrol the voltage.

PROPELLER

propeller is essentially a type of fan *hich transmits po*er by converting

rotational motion into thrust for propulsion of a vehicle such as an aircraft@

ship@ or submarine through a fluid such as *ater or air@ by rotating t*o or


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more t*isted blades about a central shaft@ in a manner analogous to rotating

a scre* through a solid. The blades of a propeller act as rotating *ings (the

blades of a propeller are in fact *ings or airfoils@ and produce force through

application of both EernoulliFs principle and &e*tonFs third la*@ generating a

difference in pressure bet*een the for*ard and rear surfaces of the airfoil8

shaped blades and by accelerating a mass of air rear*ard.

Rotating the =amilton )tandard =57 propeller on a %) &avy "!8+"

'rionFs number four engine as part of pre8flight checks. The 'rion is an anti8

submarine *arfare aircraft

S'!!./

lthough there is a variety of applications that use thermoelectric devices@

all of them are based on the same principle. :hen designing a

thermoelectric application@ it is important that all of the relevant electrical


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and thermal parameters be incorporated into the design process. 'nce these

factors are considered@ a suitable thermoelectric device can be selected based

on the guidelines presented in this article.

Refee%ce+

1. #evine@ ..@ )olid )tate Cooling *ith Thermoelectrics@ "lectronic

!ackaging !roduction@ &ov. 1K9K.

2. elcor Corporation@ Thermoelectric =andbook@ )ept.@ 1KK.

+. Ro*e@ . .@ CRC =andbook of Thermoelectrics@ CRC !ress@ $nc.@ 1KK.. )mythe@ Robert@ Thermoelectric coolers take the heat out of todayFs hot

chips@ "lectronic !roducts@

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