Chapter 3, Problem 3.42P

A 5.0-cm-diameter cylinder is heated to a temperature of 200°C, and air at 30 °C forced across it at a velocity of 50 m/s (h = 180 W/m2 K). If the surface emissivity is 0.7, calculate the total heat loss per unit length if the walls of the enclosing room are at 10 °C. Comment on your calculation.

A 5.0-cm-diameter cylinder is heated to a temperature of 200 oC, and air at 30 oC forced across it at a velocity of 50 m/s (h = 180 W/m2K). If the surface emissivity is 0.7, calculate the total heat loss per unit length if the walls of the enclosing room are at 10 oC. Comment on your calculation. COMPLETE SOLUTION

In addition , the space between the upper cap, the lower cap, and the cylindrical wall is filled with linear insulating material of permeability u.

Natural Convection Cooling of an Orange.An orange 102 mm in diameter having a surface temperature of 21.1°C is placed on an open shelf in a refrigerator held at4.4°C. Calculate the heat loss by natural convection, neglecting radiation. As an approximation, the simplified equation for vertical planes can be used withLreplaced by the radius of the sphere (M1). For a more accurate correlation, see (S2).

A cylindrical storage tank with diameter of 4m and a length of 10 m will hold a fluid whose temperature must be maintained at 347k. in order to size the heater required for the tank the following worst-case scenario is considered: Ambient temperature=-20 wind speed=20m/s tank wall temperature=347k what size (kW) heater will be needed?

A long steel rod 0.305 m in diameter is initially at a temperature of 588 K. It is immersed in an oil bath maintained at 311 K. The surface convective coefficient is 125 W/m2 -K. Calculate the temperature at the center of the rod after 1 h. The average physical properties of the steel are k = 38 W/m-K and α = 0.0381 m2/h.

The author and his then 6-year-old son have conducted the following experiment to determine the thermal conductivity of a hot dog. They first boiled water in a large pan and measured the temperature of the boiling water to be 94°C, which is not surprising, since they live at an elevation of about 1650 m in Reno, Nevada. They then took a hot dog that is 12.5 cm long and 2.2 cm in diameter and inserted a thermocouple into the midpoint of the hot dog and another thermocouple just under the skin. They waited until both thermocouples read 20°C, which is the ambient temperature. They then dropped the hot dog into boiling water and observed the changes in both temperatures. Exactly 2 min after the hot dog was dropped into the boiling water, they recorded the center and the surface temperatures to be 59°C and 88°C, respectively. The density of the hot dog can be taken to be 980 kg/m3, which is slightly less than the density of water, since the hot dog was observed to be floating in water while…

1. The boiling temperature of water is 100 °C. If you put boiling water in a mugplaced at the table top, you observed that after some time the water cools down,decreasing the temperature of water in the mug. Why is this so? Explain using theZeroth Law of Thermodynamics. What happens to objects when temperature increases? For instance, a jar cover an be removed by putting the cover in hot water. Why is this so?

An inventor wants to increase the efficiency of wood-burning stoves by reducing the energy lost through the exhaust stack. he proposes to accomplish this by attaching fins to the outer surface of the chimney, as shown schematically on the picture. the fins are attached circumferentially to the stack, having a base of 0,5cm, 2cm long perpendicular to the surface, and 6cm long in the vertical direction. the surface temperature of the stack is 500 C and the surrounding temperature is 20 C for this initial thermal design, assume that each fin loses heat by natural convection with a convection heat transfer coefficient of 10W/m^2 K. select a suitable material for the fin and discuss the manner of attachment as well as the effect of contact resistance