Along, cylindrical, electrical heating element of diameter d = 10 mm, thermal conductivity k = 240 w/m-k, density rho = 2700 kg/m^3, and specific heat c_p = 900 j/kgk is installed in a duct for which air moves in cross flow over the heater at a temperature and velocity of 27 degree c and 10 m/s, respectively.

a. neglecting radiation, estimate the steady state surface temperature when, per unit length of the heater, electrical energy is being dissipated at a rate of 1000 w/m.

b. if the heater is activated from an initial temperature of 27 degree c, estimate the time required for the surface temperature to come within 10 degree c of the steady state value.

Amass of m 1.5 kg of steam is contained in a closed rigid container. initially the pressure and temperature of the steam are: p 1.5 mpa and t 240°c (superheated state), respectively. then the temperature drops to t2= 100°c as the result of heat transfer to the surroundings. determine: a) quality of the steam at the end of the process, b) heat transfer with the surroundings. for: p1.5 mpa and t 240°c: enthalpy of superheated vapour is 2900 kj/kg, specific volume of superheated vapour is 0. 1483 m/kg, while for t 100°c: enthalpy of saturated liquid water is 419kj/kg, specific volume of saturated liquid water is 0.001043m/kg, enthalpy of saturated vapour is 2676 kj/kg, specific volume of saturated vapour is 1.672 m/kg and pressure is 0.1 mpa.

Two technicians are discussing the intake air temperature (iat) sensor. technician a says that the computer uses the iat sensor as a backup to the engine coolant temperature (ect) sensor. technician b says that the powertrain control module (pcm) will subtract the calculated amount of fuel if the air measures hot. who is correct

Fluids at rest possess no flow energy. a)- true b)- false