DESIGN AND CONSTRUCTION OF AN INDUCTION FURNACE (COOLING SYSTEM)

1. DESIGN AND CONSTRUCTION OF AN INDUCTION FURNACE(COOLING SYSTEM) Presented by MG THANT ZIN WIN Roll No: Ph.D-M-7 Supervisors : Dr Mi Sanda Mon Daw Khin War Oo 22nd Seminar 22.12.2004

2. Review on Previous Seminar Three types of cooling system : • Cooling pond system • Spray pond system • Cooling tower system The following known data need to be determine the required size of a cooling pond. • Relative humidity • Wind velocity • Dry-bulb air temperature • Solar heat gain • Water quantity • Water inlet and outlet temperature

3. Solar Constant The solar constant (Isc) is the energy from the sun per unit time, received on a unit area of surface, perpendicular to the direction of propagation of the radiation, and at the earth’s mean distance from the sun, outside the earth’s atmosphere. Fig – The sun-earth geometry The values of solar constant are : 1353 W/m2or 1.940 cal/cm2 min 1165 kcal/h m2or 4871 kJ/m2 h or 428 BTU/h ft2

4. Direct, Diffuse, and Total Solar Radiation • Beam radiation: • Solar radiation intercepted by a surface with negligible direction change • and scattering in the atmosphere. • Diffuse radiation: • The solar radiation scattered by aerosols, dust and by Rayleigh mechanism. It does not have a unique direction. • Total radiation: • It is also called global radiation and the sum of diffuse and beam radiation. Fig – Direct, diffuse, and total solar radiation

5. Solar Radiation Geometry Basic Earth–Sun Angles: The position of a point P on the earth’s surface with respect to the sun’s rays is represented by the latitude, hour angle for the point, and the sun’s declination. = Latitude = hour angle = sun’s declination Fig – Latitude, hour angle, and sun’s declination

6. Declination The declination is the angle made by the line joining the centers of the sun and the earth with its projection of the equatorial plane. where, n = the day of the year The declination angle varies from a maximum value of + 23.45° on June 21 to a minimum value of – 23.45° on Dec. 21. Fig – Variation of declination over the year

7. Sunrise, Sunset and Day Length The hour angle corresponding to sunrise or sunset on a horizontal surface can be found from the equation. 15 Degrees of the hour angle is equivalent to 1 hour. The corresponding day length (in hour), denoted by is given by:

8. Empirical Equation for Predicting the Monthly Average Global Solar Radiation The following relation is the generally accepted modified form of the Angstrom-type regression equation, relating the monthly average daily global radiation to the average daily sunshine hours. = monthly average of the daily global radiation on a horizontal surface at a location (kJ/m2 – day) = monthly average of the daily global radiation on a horizontal surface at the same location on a clear day (kJ/m2 – day)

9. = monthly average of the sunshine hours per day at the location = monthly average of the maximum possible sunshine hours (or day length) per day at the location a, b = regression constants obtained by data fitting Calculation ofhas been simplified by the following equation. n = the Julian day number

10. For example : Estimate the average daily global radiation on a horizontal surface at Bangalore (77° 40' E, 12° 59' N) during the month of March, if the average sunshine hours per day are 9.5. At Bangalore : a = 0.18 and b = 0.64. We shall assume for the calculation of on March 16, n = 75. Using Cooper’s equation and substituting the desire values, The sunrise hour angle,

11. Day length, Angstrom equation, The average daily global radiation on horizontal surface,

12. Five Models for Regression Constant : a and b Turton’s model : Rietveld’s model : Fagbenle’s model : Fre’re’s model : McCulloch’s model : Rietveld’s model is selected for our calculation of the monthly average daily global radiation

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