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Presented by THANT ZIN WIN Department of Mechanical Engineering Technological University (Kyaukse) Mandalay Division, Myanmar

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2 Presentation Outlines 1.Introduction 2.Operating Principle of Coreless Induction Furnace 3.Important Role of Water Cooling 4.Types of Water Cooling System 5.Layout Description 6.Design Parameters of Cooling Pond 7.Pond Design Model Consideration 8.Equilibrium Temperature and Surface Heat Flux 9.Pond Design Calculation 10.Case Study 11.Cooling Pond Performance 12.Conclusion 13.Further Suggestions

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3 Introduction Core Type Coreless Type Fig 1 – Core and Coreless Type of Induction Furnace Electric Induction Furnace

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4 Operating Principle of Coreless Induction Furnace Electromagnetic induction Connect to a source of AC Create thermal energy Melt the charge Stirring action caused by molten metal Fig 2 - Simplified Cross Section of Coreless Induction Furnace

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5 Important Role of Water Cooling Fig 3 - A Sample Induction Coil with Cooling Water Water is vital to be success. Need high water quality. Flow velocity of all water circuit should be monitored. Cooling water supply temperature should not be below 25°C. Upper limit of leaving the coil should be no more than 70°C. If too cold water is allowed, condensation may be formed. Fig 4 - Sample of the Damaging Induction Coil

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6 Types of Water Cooling System The types of water cooling system are as follow: Cooling Pond System Spray Pond System Evaporative Cooling Tower – Open-circuit System Fan-radiator Closed-circuit System Water/water Heat Exchanger Dual System Dual System with Closed-circuit Cooling Tower

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7 Cooling Pond System Fig 5 – Sketch of Typical Cooling Pond System Large ground area Small investment Hot water inletCool water outlet Water surface Pond Process Description ft 3 /minCool water inlet Pumps Hot water outlet Control panel Capacitor bank Furnace 2 Furnace 1 Cooling pond (8,000 ft 3 ) Fig 6 – Schematic Diagram of Cooling Pond Model

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8 Layout Description of 0.16 ton Coreless Induction Furnace Fig 7 - Functional Layout of 0.16 ton Coreless Induction Furnace Pump Discharge Pipeline Suction Pipeline Capacitor Bank Furnace No. 1 Cooling Pond Control Panel Furnace No. 2

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9 Design Parameters of Cooling Pond The hot water or inlet temperature into the pond The cool water or outlet temperature from the pond The operating time occupied in melting The solar heat flux or solar energy identified as the main heating mechanisms The pond volume and size corresponding to the equilibrium temperature

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10 Pond Design Model Consideration Fig 8 - Illustrative Diagram of Cooling Pond Model V = volume T = temperature A = area Induction Furnaces Cooling Pond V, T Q, T T i, R H Interchange with Atmosphere Q = Outflow rate R = inflow rate TETE TbTb TaTa TdTd TsTs W

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11 Equilibrium Temperature and Surface Heat Flux Wind speed sc ss aa ar br ee cc Ground Subsurface conduction Hot water inlet Cool water outlet sr R, T o Q, T i TswTsw W2W2 TaTa TdTd TETE sn an TbTb T Sun Fig 9 – Heat Transfer Mechanisms in Cooling Pond

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12 Pond Design Calculation Known Data ◙ Relative humidity, RH = 62% ◙ Ambient air, T a = 88ºF ◙ Dew point, T d = 72ºF ◙ Hot water, T i = 91.4ºF ◙ Cold water, T o = 82.4ºF ◙ Latitude of Yangon, = N ◙ Wind speed, W = 4 mph ◙ Flow rate, Q = ft 3 /min Assumptions ◙ Steady-state (Completely mixed Pond) ◙ Inflow rate is equal to outflow rate ◙ T s = T (Completely well-mixed pond) ◙ No seepage into or from groundwater ◙ Neglect heat conduction between the surrounding soil ◙ Heat exchange occurs near the pond surface only ◙ Volume, V = constant ◙ Density, ρ = constant ◙ At time t = 0, T = 28ºC where, k r = water retention rate k T = thermal rate Pond volume Pond surface area

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13 Case Study Data for the Example ParameterSpecified Value Capacity0.16 ton Current frequency1,000 Hz Metal overheating temperature2.912°F Consumed power16 kW Dry bulb temperature88°F Relative humidity62% Wind speed4 mph Entering water temperature82.4°F Leaving water temperature91.4°F Latitude of Yangon16.45 N

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14 Cooling Pond Performance The results corroborate the fact that the most important variable on cooling pond performance is pond surface area itself, but not is volume.

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15 Conclusion Cooling system is the important part of coreless induction furnace. Cooling ponds are one of the economically competitive alternatives for removing of heat from induction furnaces. The most important influence factor on the cooling pond configurations is pond surface area.

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16 Further Suggestions ◙ Extending the baffles in the pond. ◙ Using the heat exchangers. Highly baffled pond, longitudinal baffles, rectangular discharge Highly baffled pond, lateral baffles, rectangular discharge

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18 Spray Pond System Fig - Sample Spray Pond System Use a number of nozzles Depend on relative humidity

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19 Fan-radiator Closed-circuit System Fig - Fan-radiator (closed-circuit) System Completely enclosed Loss of water is slight

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20 Water/water Heat Exchanger Dual System Fig - Dual System with Water/water Heat Exchanger More compact Easier to clean and maintain

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21 Dual System with Closed- circuit Cooling Tower Fig - Dual System with Closed-circuit Cooling Tower Slightly more expensive Lower Piping and pumping costs

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22 Types of Cooling Tower Fig - Mechanical Draft Cooling Towers Fig - Natural Draft Cooling Towers

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23 By using the following equations, The type of pond is shallow Declination angle, The hour angle, Maximum possible sunshine duration, The extraterrestrial solar radiation, Ref: Magal, B. S. (1999), Solar Power Engineering, Fourth reprint, TATA McGraw Hill Publishing Company Limited, Bombay. Cooling Pond Area and Volume Calculation

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24 Clear sky solar radiation, Equilibrium temperature by using the iterative method, The net heat flux,

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25 The net heat exchange coefficient, Normalized intake temperature, Pond cooling capacity, Required cooling pond area,

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26 By implementing to unit depth, the volume of cooling pond is Approximately, the volume is used in the construction. From the above volume and area, the relationship between the temperature and operating time is obtained as follows: Where, k r = water retention rate k T = thermal rate

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27 Solar Heat Flux sc ss aa ar ee cc sn an br sr Cloud Sun Water surface Fig – Components of Surface Heat Transfer where, n = the net heat flux into the water surface sn = the net solar (short-wave) radiation into the water surface an = the net atmospheric (long-wave) radiation from the water surface br = the back (long-wave) radiation from the water surface e = the evaporative heat flux from the water surface c = the conductive heat flux from the water surface s = the solar radiation at water surface sr = the reflected solar radiation a = the atmospheric (long-wave) radiation ar = the reflected atmospheric radiation

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