1. 1 st Integrated Seminar 16.2.2004 DESIGN AND CONSTRUCTION OF AN INDUCTION FURNACE (COOLING SYSTEM) Presented by MG THANT ZIN WIN Roll No: Ph.D-M-7 Supervisors : Dr Mi Sandar Mon Daw Khin War Oo

2. Cooling Systems for Electric Induction Furnace Cooling Pond System Open-circuit System with Evaporative Cooling Tower Spray Pond System Fan-radiator (Closed-circuit) System Dual System with Water/Water Heat Exchanger Dual System with Closed-circuit Cooling Tower

3. Cooling Pond System It is used in UNIDO induction furnace. Advantages Simplicity Small investment Low noise control Disadvantages Large ground area Less effective in warm ambient conditions Not suitable for continuous thermal duty

4. Open-circuit System with Evaporative Cooling Tower Furnace and Ancillaries Buffer Tank Pump Cooling Tower Fig – Open-circuit system with evaporative cooling tower

5. Types of Cooling Tower Mechanical Draft Cooling Tower Natural Circulation Cooling Tower Induced Draft Forced Draft CounterflowCrossflow AtmosphericNatural Draft

6. (a) Induced Draft (b) Forced Draft (c) Atmospheric (d) Natural Draft (e) Counterflow (f) Crossflow Fig - Common Types of Cooling Tower

7. Mechanical Draft Counterflow Cooling Tower Inlet Air Outlet Air Water Function Principles Fig – Illustration of a counterflow tower Inlet Air

8. Cooling Tower Theory Heat is transferred from water drops to the surrounding air by the transfer of sensible and latent heat. Fig – Water drop with interfacial film

9. Merkel Equation Tower characteristic value, where, K = mass transfer coefficient, lb water/ (h.ft 2 ) a = contact area, ft 2 /ft 3 tower volume V = active cooling volume, ft 3 /ft 2 of plan area L = water rate, lb/ (h.ft 2 ) h w = enthalpy of air-water vapor-mixture at bulk water temperature, Btu/lb dry air h a = enthalpy of air-water vapor-mixture at wet bulb temperature, Btu/lb dry air

10. Graphical Representation of Tower Characteristic Fig – Cooling tower process heat balance (Markey Co)

11. Chebyshev Method Using Numerical Integration where,

12. Example Calculation KaV/L = ?, Hot water = 105°F, Cold water = 85°F, Ambient web bulb temperature = 78°F, L/G = 0.97 From air-water vapor-mixture tables, h 1 (entering air) at 78°F wet bulb temperature = 41.58 Btu/lb h 2 (leaving air) = 41.58 + 0.97(105-85) = 60.98 Btu/lb

13. Problem Solving T, °Fh water h air h w -h a 1/Δh T 2 = 85 T 2 + 0.1(20) = 87 T 2 + 0.4(20) = 93 T 1 - 0.4(20) = 97 T 1 - 0.1(20) = 103 T1 = 105 49.43 51.93 60.25 66.55 77.34 81.34 h 1 = 41.58 h 1 + 0.1 L/G (20) = 43.52 h 1 + 0.4 L/G (20) = 49.34 h 2 - 0.4 L/G (20) = 53.22 h 2 - 0.1 L/G (20) = 59.04 h 2 = 60.98 Δh 1 = 8.41 Δh 2 = 10.91 Δh 3 = 13.33 Δh 4 = 18.30 0.119 0.092 0.075 0.055 0.341

14. Nomograph Method Hot water = 100°F, Cold water = 80°F, Wet bulb temp: = 70°F, L/G = 1 So, (KaV)/L = 1.42 # Fig - Nomograph of cooling tower characteristics [Wood and Belts, Engineer, 189(4912), 337 (1950)]

15. Summary for Cooling Towers 1.A change in wet bulb temperature (due to atmospheric conditions) will not change the tower characteristic (KaV/L). 2.A change in the cooling range will not change KaV/L. 3.Only a change in the L/G ratio will change KaV/L.