A5-m × 6-m × 8-m room is to be heated by an electrical resistance heater placed in a short duct in the room.

initially, the room is at 15°c, and the local atmospheric pressure is 98 kpa.

the room is losing heat steadily to the outside at a rate of 200 kj/min.

a 300-w fan circulates the air steadily through the duct and the electric heater at an average mass flow rate of 50 kg/min.

the duct can be assumed to be adiabatic, and there is no air leaking in or out of the room.

if it takes 13 min for the room air to reach an average temperature of 25°c, find

(a) the power rating of the electric heater

(b) the temperature rise that the air experiences each time it passes through the heater.

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.

What precautions should you take to prevent injuries when dealing with heavy loads?

The mass flow rate of the fluid remains constant in all steady flow process. a)- true b)- false