INTRODUCTON

1.INTRODUCTION1.1IntroductionA calorimeter is a device used for calorimetry, the science of measuring the heat of chemical reactions or physical changes as well as heat capacity. The word calorimeter is derived from the Latin word calor, meaning heat. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the enthalpy change per mole of a substance A in a reaction between two liquids A and B, the liquids are added to a calorimeter and the initial and final (after the reaction has finished) temperatures are noted. Multiplying the temperature change by the mass and specific heat capacities of the liquids gives a value for the energy given off during the reaction (assuming the reaction was exothermic.). Dividing the energy change by how many moles of X were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

1.2Types of CalorimeterA reaction calorimeter is a calorimeter in which a chemical reaction is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter 1.2.1Heat flow calorimetryThe cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat flow coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

1.2.2Heat balance calorimetryThe cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

1.2.3Power CompensationPower compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

1.2.4Constant FluxConstant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialist control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

1.2.5Bomb calorimetersA bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel, as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water ( ca.2000 ml)before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burnt. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid. After the temperature rise has been measured, the excess pressure in the bomb is released.

1.2.5Constant-Pressure CalorimeterA constant-pressure calorimeter measures the change in enthalpy of a reaction occurring in solution during which the atmospheric pressure remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested Styrofoam cups and holes through which a thermometer and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides insulation.Then

Cp = (W * DH / (M * DT))where

DH = Enthalpy of solution

DT = Change of temperature

W = weight of solute

M = molecular weight of solute

1.2.7Differential Scanning CalorimeterIn a differential scanning calorimeter (DSC), heat flow into a sampleusually contained in a small aluminium capsule or 'pan'is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a heat flux DSC, both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate dT/dt = is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its heat capacity Cp. The difference in flow dq/dt induces a small temperature difference T across the slab. This temperature difference is measured using a thermocouple. The heat capacity can in principle be determined from this signal Note that this formula (equivalent to Newton's law of heat flow) is analogous to, and much older than, Ohm's law of electric flow V = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak. From the integral of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in polymer characterization.

A modulated temperature differential scanning calorimeter (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate

1.2.8X-ray Microcalorimeter

Figure1.1X ray Microcalorimeter

In 1982, a new approach to non-dispersive X-ray spectroscopy, based on the measurement of heat rather than charge, was proposed by Moseley et al. (1984). The detector, and X-ray microcalorimeter, works by sensing the heat pulses generated by X-ray photons when they are absorbed and thermalized. The temperature increase is directly proportional to photon energy. This invention combines high detector efficiency with high energy resolution, mainly achievable because of the low temperature of operation. Microcalorimeters have a low-heat-capacity mass that absorbs incident X-ray (UV, visible, or near IR) photons, a weak link to a low-temperature heat sink which provides the thermal isolation needed for a temperature rise to occur, and a thermometer to measure change in temperature. Following these ideas, a large development effort started. The first astronomical spacecraft that was designed, built and launched with embarqued cryogenic microcalorimeters was Astro-E2. NASA as well as ESA have plans for future missions (Constellation-X and XEUS, respectively) that will use some sort of micro-calorimeters.

1.3Theoretical BackgroundCalorimetry is the study of heat transfer during physical and chemical processes. A heat transfer is always connected to a transport of energy. The total energy of a system is called internal energy U,which is defined as the total kinetic and potential energy of the molecules in the system.Here by the system we mean the part of the world under observation. The system may be able to interact with its sorroundings, i.e the region outside the system where the measurments take place. Depending on the boundaries between the system and its sorrundings the system can be characterized. A system is called open if matter can be exchanged with its sorroundings and called closed otherwsie. Independent of the ability to exchange matter is the capacity to exchange energy. Energy can be exchanged in terms of mechanical work (e.g by expansion) or by the heat transfer. In the latter, the system is called diathermic if heat transfer is permitted, and adiabatic otherwsie. A system which has neither thermal nor mechanical contact with its sorrundings is called an isolated system.1.4Conclusion In this chapter we disscussed how heat can be measured using Calorimeter, what are the types of Calorimeter and how each type used to measured heat energy, comparison between each type and how theritical we can use Calorimeter.

2.

2.1Block Diagram of Bomb Calorimeter

Figure 2.1Block diagram

2.2Explanation of Various Blocks

2.2.1Sample cup Sample cup Is basically the cup used to put the sample for measuring its calorific value

2.2.2 Bomb with oxygen The sample cup is the part of the bomb containing oxygen .the oxygen bomb also contains the fuse wires which will be used in the combustion.

2.2.3Temperature measurement There is also a thermometer immersed in the calorimeter in order to measure the temperature.

2.2.3 Level detector The level sensors are attached in the calorimeter bucket in order to maintain the water level in the calorimeter bucket.

2.2.4 PLC All the equipments assembled in the calorimeter are controlled by the PLC.

2.2.5Inner & Outer Bath The Inner and outer baths are used to maintain the temperature of the bomb calorimeter.

2.3 Flow Chart

2.4Procedure Handle the calorimetric apparatus with great care. There is a hazard of electrical shock or of a short circuit from the exposed terminals. It is necessary to keep the working space clean and dry. The bomb is expensive and should be handled with care. In particular, be very careful not to scratch or dent any of the closure surfaces. When the bomb is dismantled its various parts should be placed gently on a clean, paper towel. Always place the lid to the calorimeter apparatus on its stand when it is not in place on the apparatus. Be especially careful when moving the lid, not to break the long thermometer or to bend the stirring shaft. When the bomb head is not in the bomb, it should be carefully placed on the bomb head support stand. Check the condition of the bomb. The bomb must be clean and dry, with no bits of iron wire in the terminals. Make sure that the jacket is completely empty and that the inside of the calorimeter is dry. 2.4.1Preparing the Sample Cut about a 10 cm length of the fuse wire, making sure that it is free of kinks or sharp bends. Accurately weigh the piece of fuse wire (use an analytical balance). Prepare pellets of the samples to be used. The pellets should be 0.8 0.1 g for the benzoic acid (a prepressed pellet may be used if available) and 0.5 0.1 g for naphthalene. Your lab instructor will show you how to use the pellet press. Weigh the pellet accurately. If the pellet is too large, shave it to the desired weight with a spatula. Reweigh the pellet, if necessary. Handle the pellet and wire very carefully after weighing.

2.4.2Ignition System

The cover of the oxygen bomb contains ignition terminals which are connected to the fuse wire in order to initiate combustion of the fuel sample inside the oxygen bomb. The lead wires from the ignition system are connected to the ignition terminals of the oxygen bomb after it is submerged in water in the calorimeter bucket. The circuit contains an ignition switch and an indicator light. In order to initiate combustion (fire the bomb), the switch is pressed held down until the indicator light goes out.

Figure2.1Diagram showing the steps for attaching the fuse wire to the electrodes in the bomb.

Figure 2.2Photograph of the bomb head, where fuse wires are to be attached. 2.4.3Installing the Bomb Head Take care not to disturb the sample when moving the bomb head from the support stand to the bomb cylinder. Slide the head into the cylinder and push it down as far as it will go. Set the screw cap on the cylinder and turn it down firmly by hand. Do not use a wrench. Hand tightening is sufficient to obtain a tight seal. Check for electrical continuity with an ohmmeter. The resistance between the two leads on the outside of the calorimeter should be quite low.2.4.4Filling the bomb with oxygen Press the fitting on the end of the oxygen hose into the inlet valve socket and the tighten the knurled union nut finger tight. Line up the fittings carefully before tightening, since misaligning the threads may damage them. Close the control valve on the filling apparatus. Then slowly open or "crack" the oxygen cylinder valve not more than one quarter turn. Open the filling connection control valve slowly and watch the outlet pressure gauge. When the bomb pressure rises to the desired filling pressure of 18-20 atm, close the control valve. Release the pressure in the bomb by slowly opening the knurled vent valve on the bomb head. This is done to flush out the atmospheric nitrogen in the bomb. Close the vent valve and refill the bomb to the desired pressure. The bomb inlet check valve will automatically close when the oxygen supply is shut off, leaving the bomb pressurized to the highest indicated pressure. DO NOT VENT THE BOMB. Release the residual pressure in the connecting hose by pushing downward on the lever attached to the relief valve. The gauge pressure should now return to zero. Remove the oxygen filling connection. Again, check for electrical continuity.

3.Hardware & Software3.1Hardware

PLC

PT100 Sensors

Relays

Solenoid

Resistors

Diode

Transformer

Capacitors

DC Motor

3.2Software

Syswin 3.43.3The Pt100 Sensor3.3.1Description Pt100 is the common abbreviation for the most common type of resistance temperature sensor used in industry.

It has a specified resistance of 100.00 ohms at 0C and is made of Platinum which has an accurately defined resistance vs. temperature characteristic. There are two minor variations, the most common giving 138.50 ohms at 100C (DIN standard) and the other giving 139.00 ohms at 100C (popular in Japan). It is most important to know which you are using when ordering or calibrating instrumentation.

Because accurate tables of resistance v. temperature are available it is common practice to calibrate instruments using precision decade boxes from table values.

Pt100 sensors were originally made with platinum wire wound on a ceramic former but are now made more cheaply by depositing a platinum film onto a ceramic substrate.

Typical accuracies are 0.2%, 0.1% and 0.05% of value at 0C. The higher the accuracy the higher the price.

Note that there are two error characteristics, an offset error (ie. how far out it is at 0C) and a span or gain error (ie. how the resistance change with temperature agrees with the theoretical figure). The gain error depends on the offset error and the impurities in the platinum.

These sensors are also made in 200, 500, and 1000 ohms values. Although the sensors are sold loose, it is usual to buy them made up into stainless steel probes for insertion into processes.

3.3.2Temperature Characteristics Pt100 elements are specified over a temperature range of -200C to 850C however the actual operating temperature is determined by the construction of the probe into which they are incorporated. Typical low cost probes are made by soldering the Pt100 to PVC or silicon insulated copper wires. Obviously these are limited by the maximum temperature of the insulation. For higher temperature work the Pt100 is silver soldered or crimped onto mineral insulated wires and embedded in an insulating medium such as aluminium oxide powder.

At higher temperatures the platinum film can slowly evaporate which permanently changes the resistance of the sensor.

3.3.3Errors The low resistance of the Pt100 means that lead resistance can introduce noticeable errors. Lead resistance introduces two errors, an offset error caused by the lead resistance itself (which can be trimmed out) and a change in lead resistance with temperature (which cannot be trimmed out). These can both be overcome by the use of 3-wire and 4-wire compensation circuits.

Most probes are made in 3-wire configuration with one wire attached to one terminal and two wires attached to the other. In a bridge circuit the two wires end up in opposite arms of the bridge and their resistances cancel.

Note that 3-wire compensation is theoretically perfect only in constant current bridges. Constant voltage bridges are only perfect when the bridge is balanced, however in most cases the error is insignificant.

For two wire operation (normally very short cables) the twin wires are usually joined together. Another cause of error is internal self heating. Because a current must be passed through the sensor to obtain a voltage signal for the electronics there is a small amount of power generated which causes the sensor to warm up and thereby changing its resistance. A large current will give a nice big signal for the electronics but also a larger self heating error. A small current reduces this error but lower drift electronics is required to minimize errors from the circuit. The best trade off depends on the application however generally currents of the order of 1mA or less are typically used. Self heating errors are larger when measuring gas temperatures because of the poorer heat dissipation from the sensor.

The resistance/temperature characteristic of a Pt100 is not linear although for many applications the error is acceptable without correction.

A typical example 0C = 100ohm, 50C = 119.4ohm, 100C = 138.5ohm. Calibrating an instrument such that 0C = 0% and 100C = 100% will give a reading at 50C = 50.4%.

There are several differing techniques for correcting the non-linearity of a Pt100 sensor including break point linearizers, and look up tables, but a simple technique is to slightly vary the current through the sensor as its value changes. Careful component selection can reduce the error by a factor of 10 or better.

3.3.4Disadvantages Most people regard the major disadvantages of the Pt100 sensor over other industrial sensors, such as thermocouples, as response time and physical strength.

Modern Pt100 sensors are now so small and light that the response time no longer depends on the sensor itself. The response time of a Pt100 in a stainless steel sheath will be almost identical to that of an insulated thermocouple in an identical sheath because the thermal characteristics of the sheath are the major contributing factor.

The physical strength of a thermocouple is still superior but a Pt100 sensor properly packed in aluminiun oxide in a stainless steel sheath should withstand everything short of a direct blow from a hammer.

3.3.5Comparison of Sensors THERMOCOUPLEPT100THERMISTORSOLID STATE DEVICES

OPERATING RANGEVery wide Type T can go down below -200C. Type W5 can approach 1800CWide -200C to 600CNarrow. Typically -40C to 300CVery narrow Typically -40C to 125C

PRICEGenerally inexpensive although type R & S use expensive platinum wire.Fairly inexpensiveLow accuracy types very inexpensive - high accuracy types more expensive than Pt100Inexpensive

ACCURACYModerateExcellentPoor to excellentModerate

LINEARITYPoorGoodTerribleVery good

PHYSICAL STRENGTHExcellentPoor to very good - Depends on probe constructionPoor to very good - Depends on probe constructionGood to very good - Depends on probe construction

3.4 Solid State Relay Solid State Relays (SSRs) are switching devices consisting of electronic components. The term "Solid State" means that these relays do not incorporate any moving parts in the load switching circuit.

4.DC MOTORS

4.1 History and Development

Figure 4.1Jedlik's electric car of 1828.The principle of conversion of electrical energy into mechanical energy by electromagnetic means was demonstrated by the British scientist Michael Faraday in 1821 and consisted of a free-hanging wire dipping into a pool of mercury. A permanent magnet was placed in the middle of the pool of mercury. When a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a circular magnetic field around the wire. This motor is often demonstrated in school physics classes, but brine (salt water) is sometimes used in place of the toxic mercury. This is the simplest form of a class of electric motors called homopolar motors. A later refinement is the Barlow's Wheel. These were demonstration devices, unsuited to practical applications due to limited power.

The first real electric motor, using electromagnets for both stationary and rotating parts, was demonstrated by nyos Jedlik in 1828 Hungary. He built an electric-motor propelled vehicle in 1828.[1]The first English commutator-type direct-current electric motor capable of a practical application was invented by the British scientist William Sturgeon in 1832. Following Sturgeon's work, a commutator-type direct-current electric motor made with the intention of commercial use was built by the American Thomas Davenport and patented in 1837. Although several of these motors were built and used to operate equipment such as a printing press, due to the high cost of primary battery power, the motors were commercially unsuccessful and Davenport went bankrupt. Several inventors followed Sturgeon in the development of DC motors but all encountered the same cost issues with primary battery power. No electricity distribution had been developed at the time. Like Sturgeon's motor, there was no practical commercial market for these motors.

The modern DC motor was invented by accident in 1873, when Znobe Gramme connected the dynamo he had invented to a second similar unit, driving it as a motor. The Gramme machine was the first electric motor that was successful in the industry.

In 1888 Nikola Tesla invented the first practicable AC motor and with it the polyphase power transmission system. Tesla continued his work on the AC motor in the years to follow at the Westinghouse company.

4.2Categorization of Electric MotorsThe classic division of electric motors has been that of Alternating Current (AC) types vs Direct Current (DC) types. This is more a de facto convention, rather than a rigid distinction. For example, many classic DC motors run on AC power, these motors being referred to as universal motors.

The ongoing trend toward electronic control further muddles the distinction, as modern drivers have moved the commutator out of the motor shell. For this new breed of motor, driver circuits are relied upon to generate sinusoidal AC drive currents, or some approximation of. The two best examples are the brushless DC motor and the stepping motor, both being poly-phase AC motors requiring external electronic control.

Considering all rotating (or linear) electric motors require synchronism between a moving magnetic field and a moving current sheet for average torque production, there is a clearer distinction between an asynchronous motor and synchronous types. An asynchronous motor requires slip between the moving magnetic field and a winding set to induce current in the winding set by mutual inductance; the most ubiquitous example being the common AC induction motor which must slip in order to generate torque. In the synchronous types, induction (or slip) is not a requisite for magnetic field or current production (eg. permanent magnet motors, synchronous brush-less wound-rotor doubly-fed electric machine).

4.3Comparison of Motor TypesTypeAdvantagesDisadvantagesTypical ApplicationTypical Drive

AC Induction(Shaded Pole)Least expensiveLong lifehigh powerRotation slips from frequencyLow starting torqueFansUni/Poly-phase AC

AC Induction(split-phase capacitor)High powerhigh starting torqueRotation slips from frequencyAppliancesUni/Poly-phase AC

AC SynchronousRotation in-sync with freqlong-life (alternator)More expensiveClocksAudio turntablestape drivesUni/Poly-phase AC

Stepper DCPrecision positioningHigh holding torqueRequires a controllerPositioning in printers and floppy drivesMultiphase DC

Brushless DC electric motorLong lifespanlow maintenanceHigh efficiencyHigh initial costRequires a controllerHard drivesCD/DVD playerselectric vehiclesMultiphase DC

Brushed DC electric motorLow initial costSimple speed control (Dynamo)High maintenance (brushes)Low lifespanTreadmill exercisersautomotive startersDirect (PWM)

[2]

4.4Torque Capability of Motor TypesWhen optimally designed for a given active current (i.e., torque current), voltage, pole-pair number, excitation frequency (i.e., synchronous speed), and core flux density, all categories of electric motors or generators will exhibit virtually the same maximum continuous shaft torque (i.e., operating torque) within a given physical size of electromagnetic core. Some applications require bursts of torque beyond the maximum operating torque, such as short bursts of torque to accelerate an electric vehicle from standstill. Always limited by magnetic core saturation or safe operating temperature rise and voltage, the capacity for torque bursts beyond the maximum operating torque differs significantly between categories of electric motors or generators.

Note Capacity for bursts of torque should not be confused with Field Weakening capability inherent in fully electromagnetic electric machines (Permanent Magnet (PM) electric machine are excluded). Field Weakening, which is not readily available with PM electric machines, allows an electric machine to operate beyond the designed frequency of excitation without electrical damage.

Electric machines without a transformer circuit topology, such as Field-Wound (i.e., electromagnet) or Permanent Magnet (PM) Synchronous electric machines cannot realize bursts of torque higher than the maximum designed torque without saturating the magnetic core and rendering any increase in current (i.e., torque) as useless. Furthermore, the permanent magnet assembly of PM synchronous electric machines can be irreparably damaged, if bursts of torque exceeding the maximum operating torque rating are attempted.

Electric machines with a transformer circuit topology, such Induction (i.e., asynchronous) electric machines, Induction Doubly-Fed electric machines, and Induction or Synchronous Wound-Rotor Doubly-Fed (WRDF) electric machines, exhibit very high bursts of torque because the active current (i.e., Magneto-Motive-Force or the product of current and winding-turns) induced on either side of the transformer oppose each other and as a result, the active current contributes nothing to the transformer coupled magnetic core flux density, which would otherwise lead to core saturation.

Electric machines that rely on Induction or Asynchronous principles short-circuit one port of the transformer circuit and as a result, the reactive impedance of the transformer circuit becomes dominant as slip increases, which limits the magnitude of active (i.e., real) current. Still, bursts of torque that are two to three times higher than the maximum design torque are realizable.

The Synchronous WRDF electric machine is the only electric machine with a truly dual ported transformer circuit topology (i.e., both ports independently excited with no short-circuited port). The dual ported transformer circuit topology is known to be unstable and requires a multiphase slip-ring-brush assembly to propagate limited power to the rotor winding set. If a precision means were available to instantaneously control torque angle and slip for synchronous operation during motoring or generating while simultaneously providing brushless power to the rotor winding set (see Brushless wound-rotor doubly-fed electric machine), the active current of the Synchronous WRDF electric machine would be independent of the reactive impedance of the transformer circuit and bursts of torque significantly higher than the maximum operating torque and far beyond the practical capability of any other type of electric machine would be realizable. Torque bursts greater than eight times operating torque have been calculated.

4.5DC MotorsA DC motor is designed to run on DC electric power. Two examples of pure DC designs are Michael Faraday's homopolar motor (which is uncommon), and the ball bearing motor, which is (so far) a novelty. By far the most common DC motor types are the brushed and brushless types, which use internal and external commutation respectively to create an oscillating AC current from the DC source -- so they are not purely DC machines in a strict sense.

4.6Brushed DC motorsThe classic DC motor design generates an oscillating current in a wound rotor with a split ring commutator, and either a wound or permanent magnet stator. A rotor consists of a coil wound around a rotor which is then powered by any type of battery.

Many of the limitations of the classic commutator DC motor are due to the need for brushes to press against the commutator. This creates friction. At higher speeds, brushes have increasing difficulty in maintaining contact. Brushes may bounce off the irregularities in the commutator surface, creating sparks. This limits the maximum speed of the machine. The current density per unit area of the brushes limits the output of the motor. The imperfect electric contact also causes electrical noise. Brushes eventually wear out and require replacement, and the commutator itself is subject to wear and maintenance. The commutator assembly on a large machine is a costly element, requiring precision assembly of many parts. There are three types of DC motor 1. DC series motor

2. DC shunt motor

3. DC compound motor - there are also two types

a. Cumulative compound

b. Differentially compounded

4.7Brushless DC motorsSome of the problems of the brushed DC motor are eliminated in the brushless design. In this motor, the mechanical "rotating switch" or commutator/brushgear assembly is replaced by an external electronic switch synchronised to the rotor's position. Brushless motors are typically 85-90% efficient, whereas DC motors with brushgear are typically 75-80% efficient.

Midway between ordinary DC motors and stepper motors lies the realm of the brushless DC motor. Built in a fashion very similar to stepper motors, these often use a permanent magnet external rotor, three phases of driving coils, one or more Hall effect sensors to sense the position of the rotor, and the associated drive electronics. The coils are activated, one phase after the other, by the drive electronics as cued by the signals from the Hall effect sensors. In effect, they act as three-phase synchronous motors containing their own variable-frequency drive electronics. A specialized class of brushless DC motor controllers utilize EMF feedback through the main phase connections instead of Hall effect sensors to determine position and velocity. These motors are used extensively in electric radio-controlled vehicles. When configured with the magnets on the outside, these are referred to by modelists as outrunner motors.

Brushless DC motors are commonly used where precise speed control is necessary, as in computer disk drives or in video cassette recorders, the spindles within CD, CD-ROM (etc.) drives, and mechanisms within office products such as fans, laser printers and photocopiers. They have several advantages over conventional motors Compared to AC fans using shaded-pole motors, they are very efficient, running much cooler than the equivalent AC motors. This cool operation leads to much-improved life of the fan's bearings.

Without a commutator to wear out, the life of a DC brushless motor can be significantly longer compared to a DC motor using brushes and a commutator. Commutation also tends to cause a great deal of electrical and RF noise; without a commutator or brushes, a brushless motor may be used in electrically sensitive devices like audio equipment or computers.

The same Hall effect sensors that provide the commutation can also provide a convenient tachometer signal for closed-loop control (servo-controlled) applications. In fans, the tachometer signal can be used to derive a "fan OK" signal.

The motor can be easily synchronized to an internal or external clock, leading to precise speed control.

Brushless motors have no chance of sparking, unlike brushed motors, making them better suited to environments with volatile chemicals and fuels. Also, sparking generates ozone which can accumulate in poorly ventilated buildings risking harm to occupants' health.

Brushless motors are usually used in small equipment such as computers and are generally used to get rid of unwanted heat.

They are also very quiet motors which is an advantage if being used in equipment that is affected by vibrations.

Modern DC brushless motors range in power from a fraction of a watt to many kilowatts. Larger brushless motors up to about 100 kW rating are used in electric vehicles. They also find significant use in high-performance electric model aircraft.

4.8Coreless or Ironless DC MotorsNothing in the design of any of the motors described above requires that the iron (steel) portions of the rotor actually rotate; torque is exerted only on the windings of the electromagnets. Taking advantage of this fact is the coreless or ironless DC motor, a specialized form of a brush or brushless DC motor. Optimized for rapid acceleration, these motors have a rotor that is constructed without any iron core. The rotor can take the form of a winding-filled cylinder inside the stator magnets, a basket surrounding the stator magnets, or a flat pancake (possibly formed on a printed wiring board) running between upper and lower stator magnets. The windings are typically stabilized by being impregnated with Electrical epoxy potting systems. Filled epoxies that have moderate mixed viscosity and a long gel time. These systems are highlighted by low shrinkage and low exotherm. Typically UL 1446 recognized as a potting compound for use up to 180C (Class H) UL File No. E 210549.

Because the rotor is much lighter in weight (mass) than a conventional rotor formed from copper windings on steel laminations, the rotor can accelerate much more rapidly, often achieving a mechanical time constant under 1 ms. This is especially true if the windings use aluminum rather than the heavier copper. But because there is no metal mass in the rotor to act as a heat sink, even small coreless motors must often be cooled by forced air.

These motors were commonly used to drive the capstan(s) of magnetic tape drives and are still widely used in high-performance servo-controlled systems, like radio-controlled vehicles/aircraft, humanoid robotic systems, industrial automation, medical devices, etc.

4.9Universal MotorsA variant of the wound field DC motor is the universal motor. The name derives from the fact that it may use AC or DC supply current, although in practice they are nearly always used with AC supplies. The principle is that in a wound field DC motor the current in both the field and the armature (and hence the resultant magnetic fields) will alternate (reverse polarity) at the same time, and hence the mechanical force generated is always in the same direction. In practice, the motor must be specially designed to cope with the AC (impedance must be taken into account, as must the pulsating force), and the resultant motor is generally less efficient than an equivalent pure DC motor.

Operating at normal power line frequencies, the maximum output of universal motors is limited and motors exceeding one kilowatt (about 1.3 horsepower) are rare. But universal motors also form the basis of the traditional railway traction motor in electric railways. In this application, to keep their electrical efficiency high, they were operated from very low frequency AC supplies, with 25 and 16.7 hertz (Hz) operation being common. Because they are universal motors, locomotives using this design were also commonly capable of operating from a third rail powered by DC.

The advantage of the universal motor is that AC supplies may be used on motors which have the typical characteristics of DC motors, specifically high starting torque and very compact design if high running speeds are used. The negative aspect is the maintenance and short life problems caused by the commutator. As a result such motors are usually used in AC devices such as food mixers and power tools which are used only intermittently. Continuous speed control of a universal motor running on AC is easily obtained by use of a thyristor circuit, while stepped speed control can be accomplished using multiple taps on the field coil. Household blenders that advertise many speeds frequently combine a field coil with several taps and a diode that can be inserted in series with the motor (causing the motor to run on half-wave rectified AC).

Universal motors generally run at high speeds, making them useful for appliances such as blenders, vacuum cleaners, and hair dryers where high RPM operation is desirable. They are also commonly used in portable power tools, such as drills, circular and jig saws, where the motor's characteristics work well. Many vacuum cleaner and weed trimmer motors exceed 10,000 RPM, while Dremel and other similar miniature grinders will often exceed 30,000 RPM.

Motor damage may occur due to overspeeding (running at an RPM in excess of design limits) if the unit is operated with no significant load. On larger motors, sudden loss of load is to be avoided, and the possibility of such an occurrence is incorporated into the motor's protection and control schemes. In smaller applications, a fan blade attached to the shaft often acts as an artificial load to limit the motor speed to a safe value, as well as a means to circulate cooling airflow over the armature and field windings.

With the very low cost of semiconductor rectifiers, some applications that would have previously used a universal motor now use a pure DC motor, sometimes with a permanent magnet field.

5.Programmable Logic Controller5.1Introduction Automation is the use of control system such as computers to control industrial machinery and process replacing human resource. Special hardened computers known as Programmable Logic Controllers (PLC) are frequently used to synchronize the flow of inputs from (physical) sensors and events with flow a tight control of almost any industrial process.

5.2DefinitionIt is a programmable solid state device which is used for the replacement of counters, timers, relays etc. It is an automation method using relay technology.

Figure 5.1PLC

Programmable Logic is a controller which stores instructions to command a device such as valve, to which it is connected to start up, operate a shutdown.

A Programmable Logic Controller is small computer use for automation of real world processes, such as control of machinery on factory assembly lines. The PLC usually uses a microprocessor. The program can often control complex sequencing and it often written by engineers.

Figure 5.2Applications of PLC

5.3Features of PLC 5.3.1Robust A Programmable Logic Controller is a specialized controller use to control machine and processes. It therefore shares common turns with typical PCs like central processing unit, memory, software and communications. Unlike a personal computer through the PLC is designed to survive in rugged industrial atmosphere and to be very flexible in how it interfaces with inputs and outputs to the real world.

5.3.2Variable Sizes PLCs come in many shapes and sizes. They can be so small as to fit in your shirt pocket while more involve control systems required large PLC racks. Smaller PLCs are typically designed with fixed I/O points for our consideration; we will look at the more modular rack based systems. It is called modular because the rack can accept many different types of I/O modules that simply slides in to the rack and plugged in.

5.3.3Alteration of Desktop PCs The functionality of the PLC has evolved over the years to include typical relay control, sophisticated motion control, process control, distributed control systems and complex networking. Today, the line between a general purpose programmable computer and a PLC is thinning. The data handling, storage, processing power and communication capabilities of some modern PLCs are approximately equivalent to desktop computers. PLCs functionality, combined with remote I/O hardware, allows a general purpose desktop computer to overlap some PLCs in certain applications.

5.3.4Components of PLC

The components that make a PLC work, can be divided into three areas 1. The power supply and rack.

2. The central processing unit (CPU)

3. The input/output (I/O) section.

Figure 5.3Components of PLC

The Power Supply and Rack The rack is the component that holds every thing together. Depending on the need of the control system it can be ordered in different sizes to hold more modules.

Figure 5.4Power supply

The power supply plugs in to the rack as well and supplies a regulated DC power to the other modules that plug into the rack. The most popular power supply works with 24Vdc sources.

Central Processing Unit The brain of the whole PLC is the CPU module. This module is typically lives in the slot beside the power supply. The CPU consists of a microprocessor, memory chip, and other integrated circuits to control logic, monitoring, and communications. The CPU has different operating modes. The CPU is then placed in run mode so that it can execute the program and operate the process. Since a PLC is a dedicated controller it will only process this one program over and over again. One cycle through the program is called a scan time and involves reading the inputs from the other modules, executing the logic based on these inputs and then updated the outputs accordingly. The scan time happens very quickly (in the range of 1/1000th of a second.) The memory in the CPU stores the program while also holding the status of the I/O and providing a means to store values.

Figure 5.5C.P.U

Input/Output System The input/output system provides the physical connection between the equipment and the PLC. Opening the doors on an I/O card reveals a terminal strip where the devices connect.

Figure 5.6I/Os

Inputs Input devices can consist of digital and analog devices. A digital input card handles discrete devices, which give a signal that is either on or off such as a push button, limit switch, sensors or selector switches. And analog input card converts a voltage or current (e.g. a signal that can be any where from 0 to 20mA) into a digitally equivalent number that can be understood by the PLC.

Figue 5.7I/P O/P Mechanism

Outputs Output devices can also consist of digital or analog types. A digital output card either turns a device on or off such as lights, LEDs, small motors and relays. An analog output card will convert a digital number sent by the CPU to its real world voltage or current. Typical outputs signals can range from 0 to 10volts dc. Or 4 to 20mA and are used to drive mass flow controllers, pressure regulators and position control.

5.3PLC Compared With Other Control Systems PLC is well adapted to a certain range of automation tasks. There are typically industrial processes in manufacturing where the cost of developing and maintain the automation system is highly relative to the total cost of the automation, and where changes to the system would be expected during its operational life. PLC contain everything needed to handle high power loads right out of the box, very little electrical design is required and the design problem centers on expressing the desired sequence of operation in ladder logic (or function chart) notation. PLC applications are typically highly customize systems so the cost of the PLC is low compared to the cost of contracting a designer for a specific, one time only design. On the other hand in the case of mass produce goods, customize control systems quickly pay for themselves due to the lower cost of the components, which can be optimally chosen instead of a generic solution. A micro controller based design would be appreciate where hundreds or thousands of units will be produced and so the development cost (design of power supplies and Input, Output hardware) can be spread over many sales, and where the end user would not need to alter the control.

5.3 Advantages of plc Smaller physical size than hard-wire solutions

Easier and faster to make changes

PLCs have integrated diagnostics and override functions

Diagnostics are centrally available

Applications can be immediately documented

Applications can be duplicated faster and less expensively

5.4 Solenoid valve A solenoid valve is an electromechanical valve for use with liquid or gas controlled by running or stopping an electrical current through a solenoid, which is a coil of wire, thus changing the state of the valve. The operation of a solenoid valve is similar to that of a light switch, but typically controls the flow of air or water, whereas a light switch typically controls the flow of electricity. Solenoid valves may have two or more ports in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports. Multiple solenoid valves can be placed together on a manifold.

Fig 5.8. Solenoid ValveSolenoid valves are the most frequently used control elements in fluidics. Their tasks are to shut off, release, dose, distribute or mix fluids.

5.5.1. ADVANTAGES They are found in many application areas. Solenoids offer

fast and safe switching

high reliability

long service life

good medium compatibility of the materials used

low control power and compact designCONCLUSION

The BOMB CALORIMETER is equipment, which is one of the major inventions to find out the calorific value of a given fuel.

The automation of this project was not an easy task but we are very much thankful to almighty ALLAH who helped us a lot in this project and off course the other people like our internal and external who guided us throughout the project.

6.1. FUTURE RECOMMENDATION 6.1.1. Human Machine Interface (HMI) The term user interface is often used in the context of computer systems and electronic devices. The user interface of a mechanical system, a vehicle or an industrial installation is sometimes referred to as the human-machine interface (HMI). Yet another term used is "operator-interface console" (OIC).

Fig 6.1. HMI view

The design of a user interface affects the amount of effort the user must expend to provide input for the system and to interpret the output of the system, and how much effort it takes to learn how to do this.

6.1.1.1. TYPES OF HMI 1.Touch interfaces are graphical user interfaces using a touch screen display as a combined input and output device. Used in many types of industrial processes and machines, self-service machines etc.

2.Attentive user interfaces manage the user attention deciding when to interrupt the user, the kind of warnings, and the level of detail of the messages presented to the user.

3.Batch interfaces are non-interactive user interfaces, where the user specifies all the details of the batch job in advance to batch processing, and receives the output when all the processing is done. The computer does not prompt for further input after the processing has started.

6.1.2. Programmable Automation Controller (PAC) To serve by expanding machine and industrial control system development needs, leading automation companies have created a new class of industrial controllers known as PACs. PACs combine programmable logic controller (PLC) ruggedness with PC functionality under open, flexible software architecture. With these controllers, you can build advanced systems incorporating software capabilities such as advanced control, communication, data logging, and signal processing with rugged hardware performing logic, motion, process control, and vision.

It is a compact controller that combines the features and capabilities of a PC-based control system with that of a typical programmable logic controller (PLC). PACs are most often used in industrial settings for process control, data acquisition, remote equipment monitoring, machine vision, and motion control. Additionally, because they function and communicate over popular network interface protocols. PACs are able to transfer data from the machines they control to other machines and components in a networked control system or to application software and databases.

Fig 6.2. A bank of Programmable Automation Controllers mounted on input/output (I/O) racks

PAC - PLC Comparison Generally, PACs and PLCs serve the same purpose. Both are primarily used to perform automation, process control, and data acquisition functions such as digital and analog control, serial string handling, PID, motion control, and machine vision. The parameters within which PACs operate to achieve this, however, sometimes run counter to how a PLC functions.

Unlike PLCs, PACS offer open, modular architectures, the rationale being that because most industrial applications are customized, the control hardware used for them needs to allow engineers to pick and choose the other components in the control system architecture without having to worry whether or not they will be compatible with the controller.

PACs and PLCs are also programmed differently. PLCs are often programmed in ladder logic, a graphical programming language resembling the rails and rungs of ladders that is designed to emulate old electrical relay wiring diagrams. PAC control programs are usually developed with more generic software tools that permit the designed program to be shared across several different machines, processors, HMI terminals or other components in the control system architecture.

Fig 6.3. Closeup of a Programmable Automation Controller

Reference WEBSITES [1] http //www.google.com

[2] http //www.shimadzu.com

[3] http //www.wikipedia.com

[4] http //www.howstuffworks.com.

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LEVEL CHECK BY SENSOR

IF FULL

STIRRER ON

MAINTAIN TEMP BY USING HOT/COLD WATER

IF TEMP MAINTAIN

PUT WATER IN INNER BATH FROM OUTER BATH

IF WATER IS FULL

NO

YES

NO

YES

_1292975531.vsdIF WATER IS FULL

STOP SOLINOID

COMPARISON OF INNER AND OUTER BATH WATER TEMP

IF BOTH TEMP EQUAL

NICKEL WIRE START CONDUCTION

BURN THE SAMPLE BY NICKEL WIRE

TEMPERATURE OF INNER BATH INCREASE

TEMPERATURE OF OUTER BATH INCREASE BY PLC

CONTROL OUTER BATH TEMP AND MAKE IT EQUAL TO INNER BATH TEMP

NO

YES

NO

YES

_1292975632.vsdIF THE TEMP OF INNER BATH INCREASE

CONVERT IT INTO CALORIFIC VALUE

CALCULATE T

NOTE THE FINAL TEMP OF INNER BATH

DISPLAY

DRAIN INNER AND OUTER BATH

STOP

YES

NO

_1292974937.vsdSTART

SAMPLE PUT IN SAMPLE CUP

CALORIMETER

CONNECT WITH NICKEL WIRE

BOMB

PRESS START BUTTON

OXYGEN