An Analytical Study of Cooling Pond System for Coreless Induction Furnace Presented by THANT ZIN WIN Department of Mechanical Engineering Technological University (Kyaukse) Mandalay Division, Myanmar thantm7@gmail.com MG THANT ZIN WIN

Presentation Outlines Introduction Operating Principle of Coreless Induction Furnace Important Role of Water Cooling Types of Water Cooling System Layout Description Design Parameters of Cooling Pond Pond Design Model Consideration Equilibrium Temperature and Surface Heat Flux Pond Design Calculation Case Study Cooling Pond Performance Conclusion Further Suggestions MG THANT ZIN WIN

Introduction Electric Induction Furnace Core Type Coreless Type Fig 1 – Core and Coreless Type of Induction Furnace MG THANT ZIN WIN

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 MG THANT ZIN WIN

Important Role of Water Cooling Water is vital to be success. Need high water quality. Flow velocity of all water circuit should be monitored. Fig 3 - A Sample Induction Coil with Cooling Water 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 MG THANT ZIN WIN

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 MG THANT ZIN WIN

Cooling Pond System Process Description Large ground area Hot water inlet Cool water outlet Water surface Pond Large ground area Small investment Fig 5 – Sketch of Typical Cooling Pond System Process Description 24.33 ft3/min Cool water inlet Pumps Hot water outlet Control panel Capacitor bank Furnace 2 Furnace 1 Cooling pond (8,000 ft3) Fig 6 – Schematic Diagram of Cooling Pond Model MG THANT ZIN WIN

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

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 MG THANT ZIN WIN

Pond Design Model Consideration Ta Interchange with Atmosphere Cooling Pond Td H V = volume T = temperature A = area W Q, T Ti, R Ts V, T TE Q = Outflow rate R = inflow rate Tb Induction Furnaces Fig 8 - Illustrative Diagram of Cooling Pond Model MG THANT ZIN WIN

Equilibrium Temperature and Surface Heat Flux Wind speed sc s a ar br e c Ground Subsurface conduction Hot water inlet Cool water outlet sr R, To Q, Ti Tsw W2 Ta Td TE sn an Tb T Sun Fig 9 – Heat Transfer Mechanisms in Cooling Pond

Pond Design Calculation Known Data Relative humidity, RH = 62% Ambient air, Ta = 88ºF Dew point, Td = 72ºF Hot water, Ti = 91.4ºF Cold water, To = 82.4ºF Latitude of Yangon, = 16.45 N Wind speed, W = 4 mph Flow rate, Q = 24.37 ft3/min Assumptions Steady-state (Completely mixed Pond) Inflow rate is equal to outflow rate Ts = 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 Pond volume Pond surface area where, kr = water retention rate kT = thermal rate MG THANT ZIN WIN

Case Study Data for the Example Parameter Specified Value Capacity 0.16 ton Current frequency 1,000 Hz Metal overheating temperature 2.912°F Consumed power 16 kW Dry bulb temperature 88°F Relative humidity 62% Wind speed 4 mph Entering water temperature 82.4°F Leaving water temperature 91.4°F Latitude of Yangon 16.45 N

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.

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. MG THANT ZIN WIN

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

MG THANT ZIN WIN

Fig - Sample Spray Pond System Use a number of nozzles Depend on relative humidity MG THANT ZIN WIN

Fan-radiator Closed-circuit System Fig - Fan-radiator (closed-circuit) System Completely enclosed Loss of water is slight MG THANT ZIN WIN

Water/water Heat Exchanger Dual System Fig - Dual System with Water/water Heat Exchanger More compact Easier to clean and maintain MG THANT ZIN WIN

Dual System with Closed-circuit Cooling Tower Fig - Dual System with Closed-circuit Cooling Tower Slightly more expensive Lower Piping and pumping costs MG THANT ZIN WIN

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

Cooling Pond Area and Volume Calculation 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. MG THANT ZIN WIN

Clear sky solar radiation, Equilibrium temperature by using the iterative method, The net heat flux, MG THANT ZIN WIN

The net heat exchange coefficient, Normalized intake temperature, Pond cooling capacity, Required cooling pond area, MG THANT ZIN WIN

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, kr = water retention rate kT = thermal rate MG THANT ZIN WIN

Solar Heat Flux Sun Cloud Fig – Components of Surface Heat Transfer sc br e c Cloud sr a ar s Water surface sn an 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 MG THANT ZIN WIN