A cooling coil of 1.0 ft of 304 stainless-steel tubing having an inside diameter of 0.25 in. and an outside diameter of 0.40 in. is being used to remove heat from a bath. The temperature at the inside surface of the tube is 40F and I 80F on the outside. The thermal conductivity of 304 stainless steel is a function of temperature:
where k is in btu/h*ft*F and T is in F. Calculate the heat removal in btu/s and watts.
5.3-9 Temperature of Oranges on Trees During Freezing Weather.
In orange-growing areas, the freezing of the oranges on the trees during cold noghts is of serious economic concern. If the oranges are initially at a temperature of 21.1C, calculate the center temperature of orange is exposed to air at -3.9C for 6 hours. The oranges are 102 mm in diameter and the convective coefficient is estimated as 11.4W/m2-K. The thermal conductivity k is 0.431 W/m-K and α is 4.65E-4m2/h. Neglect any latent heat effects.
A flat slab of rubber, 2.5 cm thick initially at 20°C is to be placed between two heated steel plates maintained at 140°C. The heating is to be discontinued when the temperature at the mid plane of the slab is 132°C. The rubber has a thermal conductivity of 0.16 W/mK and thermal diffusivity of 8.671x10 -6 m 2 /s. Thermal resistance from metal to rubber may be neglected. Calculate:
A) The length of the heating period, sec
B) The temperature of the rubber 0.65cm from the metal
C) The time required for the rubber to reach 132.°C at the plane specified at b).