The 150-mm-thick wall of a gas-fired furnace is con- structed of fireclay brick (k = 1.5 w/m⋅k, rho = 2600 kg/m3, cp = 1000 j/kg ⋅ k) and is well insulated at its outer surface. the wall is at a uniform initial tempera- ture of 20°c, when the burners are fired and the inner surface is exposed to products of combustion for which t[infinity] = 950°c and h = 100 w/m2 ⋅ k. (a) how long does it take for the outer surface of the wall to reach a temperature of 750 degree c?

(b) plot the temperature distribution in the wall at the foregoing time.

Apump is used to circulate hot water in a home heating system. water enters the well-insulated pump operating at steady state at a rate of 0.42 gal/min. the inlet pressure and temperature are 14.7 lbf/in.2, and 180°f, respectively; at the exit the pressure is 60 lbf/in.2 the pump requires 1/15 hp of power input. water can be modeled as an incompressible substance with constant density of 60.58 lb/ft3 and constant specific heat of 1 btu/lb or. neglecting kinetic and potential energy effects, determine the temperature change, in °r, as the water flows through the pump.

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?

During a steady flow process, the change of energy with respect to time is zero. a)- true b)- false