Question

A stone kiln has been built with 10 cm thick terracotta plates, stacked to form a working space of 3.8 m deep by 10 m in diameter. The pit is fitted with a limestone plug with a vent hole in the center. The stone plug is 5 cm thick. a. (15 pts) The interior of the pit is heated to 850°C. The surroundings are at 20°C. How much heat is lost through the walls of the kiln? b. (15 pts) How much heat is lost through the stone plug? c. (20 pts) If you find that you are having to add 950 kJ/s of heat to maintain the temperature, what is the heat lost by convection (and removing water, etc.)?

Answer 1

Given t = 10cm = 3.8m Dia = 10m = Y = 5m Surrounding temperature = 20% Pit temperature = psóc Total heat lous = 950 ley's = 950 kW r2 = "itt K = 5.7 ) = 0.3 Wimki → Thermal resistance (R In ca). 2nku In ( 51] 2X1X0.343.8 = 2.675x1013 klw R= 2.675x103 klw -> A1 = 20 c - 850c = – 830 Heat transterred (Q) - 41 - 2675xto? R -830 =-310280 W 2-675x10-3 Conductive Given = - 310.28 kW heat loss = 310.28 kW. total beat lom = 950 kw. = Convective beat lors = Total heat loys - Conductive heat lors 950 - 310.28 cs Scanned with -639-72 kw CamScanner 1 Conductive heat loss = 639.72 kW