Reconsider Prob. 4–34. Using EES (or other) software, investigate the effect of the initial temperature of the balls on the annealing time and the total rate of heat transfer. Let the temperature vary from 500°C to 1000°C. Plot the time and the total rate of heat transfer as a function of the initial temperature, and discuss the results.

Data From Problem 34

Carbon steel balls (ρ = 7833 kg/m³, k = 54 W/m · K, c_p = 0.465 kJ/kg·°C, and a = 1.474 × 1026 m²/s) 8 mm in diameter are annealed by heating them first to 900°C in a furnace and then allowing them to cool slowly to 100°C in ambient air at 35°C. If the average heat transfer coefficient is 75 W/m² · K, determine how long the annealing process will take. If 2500 balls are to be annealed per hour, determine the total rate of heat transfer from the balls to the ambient air.

Transcribed Image Text:

Furnace 900°C Air, 35°C -Steel ball 100°C