STEAM POWER PLANT

A steam power plant continuously converts the energy stored ill fossil fuels (coal, oil, natural gas) or fissile fuels (uranium, thorium) into shaft work and ultimately into electricity. The working fluid is water which is sometimes in the liquid phase and sometimes in the vapour phase during its cycle of operations. Figure 2.1 illustrates a fossil fulled power plant as a bulk energy converter from fuel to electricity using water as the working medium. Energy released by the burning of fuel is transferred to water in the boiler (8) to generate steam at a high pressure and temperature, which then expands in the turbine (n to a low pressure to produce shaft work. The steam leaving the turbine is condensed into water in the condenser (C) where cooling water from a river or sea circulates carrying away the heat released during condensation. The water (condensate) is then fed back to the boiler by the pump (P). and the cycle goes on repealing- . Itself. The working substance, water, thus follows along the B-T- C-P path of the cycle interacting externally as shown. Since the fluid isundergoing a cyclic 

process, there will be no net change in its internal energy over the cycle , dE = 0), and consequently, the net energy 'transferred to the unit mass of the ~uid as heat during the cycle must equal the net energy transfer as work from e fluid. 

COAL-FUELLED ELECTRICITY GENERATING UNIT

Coal is delivered to the facility-by railway wagons, barges or trucks. The coal handling system unloads the coal, stocks. reclaims. crushes and conveys it to storage silos. Coal from the silos is then pulverized to a fine powder and blown into the steam generator, where it is mixed with air and combusted (Q release energy for the generation of steam. The steam generator produces. superheats and reheats steam as it proceeds through the cycle. 

The steam turbine generator converts the thermal energy (enthalpy rise) of the superheated and reheated steam to electrical energy. Steam exhausted from the turbine is condensed to liquid in the condenser. The condensate pumps teed the water through t'he I.p. regenerative Iccdwatcr heaters to a deacrator, Boiler feed pumps move the dcacratcd liquid through the h.p. fccdwater heaters back to the steam generator. 

Forced draught (or draft) fans supply combustion air to the steam generator and the' primary air fans transport pulverized coal into the burners. Induced draught fans remove the flue gases from the furnace and exhaust them through the stack into the atmosphere. 

Cooling water for the condenser is supplied by the circulating water system, which takes the heat removed from the condenser and rejects it to cooling towers or another heat sink such as e cooling lake. river or sea. 

TURBINE FLOW METER

The turbine flow meters provide very accurate flow measurement over wide ow range. The accuracyrangs is from ±1I4 to ±112%, and the repeatability is excellent, ranging froin ±0.25% toas good as ±0.02%. The rangeability of turbine meters are generally considered to be between 10: I and 20.: I, however. in low ow ranges, it is often less than 10: 1. The military type turbine meters have hieved rangeabilities greater than I QO: 1. The turbine meters are available in SIZCS ranging from 6.35 to 60 mm and liquid flow ranges from 0.1 to over 50,000 

gallons per minute. 

The turbine meters are widely used for military applications. They are particularly useful in blending systems for the petroleum industry. They are effective in aero¬pace and airborne applications for energy-fuel and cryogenic (liquid oxygen and itrogen) flow measurements.

The magnetic-pickup coil consists of a permanent magnet with coil wind¬ings which is mounted in close proximity to the rotor but internal to the fluid channel. As each rotor blade passes the magnetic-pickup coil, it generates a volt¬age pulsewhich is a measure of the flow rate. and the total number of pulses give a measure of the total flow

RMS RESPODING AC ELECTRO VOLTMETER

Working Principle The rms (root mean square) value is the only amplitude characteristic of a waveform which does not depend on shape of the waveform. Therefore, 'the rms value is the most useful means to quantify signal amplitude in a.c. measurements. The rms value measures the ability of an a.c. signal to deliver power •to a resistive load, thus measuring the equivalent heating value of the signal. This means rms value of all a.c. waveform is equal to the d.c. value which produces the same amount of heat as the a.c. waveform' when connected to the same resistive load. 

For a d.c. voltage V, this heat is directly proportional to the amount of power dissipated in the resistance R and therefore, power

The rms value of a waveform can be measured by measuring the heat gen¬erated by the waveform in a resistive load and comparing it with the heat generated by a known d.c. voltage in an equivalent load .. Heat measurement is . done by thermal rms detectors 'which are made using small resistors with a thermocouple or thermistor attached to it. Thermal rms detectors are capable' of measuring rms values for signal frequencies in excess of a few hundred, megahertz (MHz). 

PH .MEASUREMNT

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 Have no text to check? Click "Select Samples".Thus pH, may be.defined ng negative loglrilnrnic to base I O-of the reciprocity of (he hydrogen ion concentration. It Is a measure of the acidity or alkalinity or solution. All values of acidity and alkalinity with respect to hydrogen and 

hydroxide ions can be expressed by a series of positive numbers between 0 and 14. Thus, a natural ~solution (like pure water) with [H+] = 10-7 has a pH of 7. If the pH is less than 7, the-solution is acid, if greater than 7. the solution is alkaline. Therefore. pH scale can range from Otto 14 in which the pH value lies between 0 to 7 for acidic solutions and between 7 to 14 fur alkaline solution's. 

pH measuring devices measure tho effective concentration, or activity. of the hydrogen ions and not the actual concentration. In very dilute solutions of dectrolyte the activity and concentration are identical. As the concentration of electrolyte in solution increases above 0.1 mollitre, the measured value of pH becomes a less reliable measure of the concentration of hydrogen ions. In addition, as the concentration of a solution increases, lhe degree of dissociation of the electrolyte decreases. 

LIQUID DENSITY MEASUREMENT

During gas density measurements, when variations in pressure and temperature are small, the temperature and pressure act Difficulties in THE measurement of densities of fluids are due to complexities in processes, venation of fluid dens[i.e!; witting the process, and the diverse characteristics of the process lndfluids governesses. Some of these methods arc: custom designed and applicable to special cases only. Others are very similar in principles and technology, and can be used for many different types of fluids. Presently, apart from conventional methods, many advanced techniques have been developed, for example, density meters based on electromagnetic principles, which are intelligent instrumentation systems. 

Depending on •the applications, fluid densities can be measured both .in static or dynamic forms. In general, static density measurements of fluids are well-developed, precise, and have greater resolution than most dynamic techniques. Chronometer and buoyancy are examples of static techniques that can be adapted to cover small density ranges with a resolution and precision, 

'Today, many static density measurement devices are computerized, coming with appropriate supporting hardware and software. In general, static type measurements. are employed in laboratory conditions, and dynamic methods are employed for real-time measurements where properties of fluids vary from time to time, . 

Density can also he detected indirectly through the measurement of some other process property: Measurement of boiling point elevation is one of the common methods of indirect density detection. Here resistance elements com¬pare the temperature of the boiling process sample with that of boiling water at the same pressure. The differential temperature scale for a particular 'solution can be calibrated in terms of density. This method is also used for end-point determination in evaporators. 

GAS DENSITY MEASUREMENT

Almost independently of each other. Thus, estimates of reasonable accuracy can be obtained by adding percentage temperature and pressure deviations from a given set of conditions. 

Often, density measurement of non-ideal gases arc required which do not act  ideal gases at certain conditions; such as at high pressures, low temperatures, or under saturation. Their non-ideal behavior may be accounted-for by modifying the-Ideal Gas Law with a Z factor.

The Z factor (also called comprehensibility factor) is .numerically dependent on operating conditions and can be read from generalized comprehensibility charts with . a reasonable degree of accuracy . 

Due to the above. reasons, extra care and further considerations arc necessary in gas density measurements . For example, perfect guscs contatn equal number of molecules under same 'conditions and equal volumes. Therefore, molecular weights may be a better option in density measurements. Flask methods, gas-balance methods, optical methods, X-ray methods are typical techniques employed for gas measurements. 

GALVANOMETER

The ballistic galvanometer does not show. steady deflection (as in current galvanometer) When in use owing to the transitory nature of the current passing through it. It oscillates with decreasing amplitude; the amplitude of the first deflection or swing or throw being proportional to the charge passing. The relation¬ship between charge and the deflection is given as 

Q=KO where, Q = charge in micro-coulombs 

Equation  holds good only if the discharge of the electricity through the galvanometer has been completed before any appreciable deflection of the moving system has taken place Hence, the moving system of such a galvanometer must have a large moment of inertia compared to the restoring moment due to the suspension, This is often achieved by the addition of weights 10 the moving svstern. Large moment of inertia means that the galvanometer; has a long 'period of vibration usually of the order of 20 It) 30 seconds,

The damping of the galvanometer should also be small so that the first deflection (swing) is large. After the first deflection (coil) has been observed, electromagnetic damping may be used to bring the movement rapidly to rest. A switch to short-circuit in the galvanometer is provided to save time in bringing the movement to rest. 

Other considerations in' the construction of ballistic galvanometers are that the moving coil should be free from magnetic material, and the suspension strip should be carefully chosen and mounted. The terminals, the' coil, and connections with the galvanometer should be of copper throughout to avoid thermometric effects. The suspension is non-conducting and the current is led into the deflection coil by delicate spirals of very thin copper strip. Construction and working of D' Personal (permanent magnet moving coil, PMMC) type galvanometer has already been discussed in detail.

A.C. Induction Meter

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A. C. induction-type energy meters are the most common form of meters met within everyday domestic and industrial installations. These energy meters mes sure electric energy in kilowatt hours.(kw H). The principle of these meters. is practically the same as that of the induction watt meters. There are two varieties of induction-type a.c. energy meters: 

Single phase energy meters are used tonearm- sure electric energy. in a.c, single-phase circuits.

Operating Principle In a single-phase energy meter, rotation of the disc is produced by the eddy currents due to the binned fluxes of two electromagnets. The fluxes of these two magnets are kept 90° apart to make the rotating field. 

Construction Figure.

4.15 illustrates the different parts of a single-phase energy meter.  

It consists of a light aluminium disc mounted on a steel spindle pivoted on a jeweled bottom bearing and a pin-type top bearing. The disc is arranged to revolve in the air-gap between the poles of two electromagnets  one supplied with a current proportional to the voltage of the supply and the other with a current proportional to the main current of the circuit. The braking torque is produced by one or two permanent magnets inducing eddy currents in the disc.