air enters a pipe at 25 °C, 100 kPa with a volumetric flow rate of 23 m3/h. On the outer pipe surface is an electrical resistor covered with insulation. With a voltage of 120 V, the resistor draws a current of 4 amps. Assuming the ideal gas model with cp = 1.005 kJ/kg - K for air and ignoring kinetic and potential energy effects, determine i. the mass flow rate of the air, in kg/h ii. the temperature of the air at the exit, in °C
Use the following conversions where necessary:1hp = 745.7W; ρwater = 1000 kg/m3; ρmercury = 13600 kg/m3; 1 atm = 101.325 kPa; Cp (water) = 4.18 kJ/kg °C; g = 9.81m/s2;
For properties of air, use R = 0.287 kJ/kg K; Cv (air) = 0.718 kJ/kg K; Cp (air) =1.005 kJ/kg K
air enters a pipe at 25 °C, 100 kPa with a volumetric flow rate of 23 m3/h. On the outer pipe surface is an electrical resistor covered with insulation. With a voltage of 120 V, the resistor draws a current of 4 amps. Assuming the ideal gas model with cp = 1.005 kJ/kg - K for air and ignoring kinetic and potential energy effects, determine
i. the mass flow rate of the air, in kg/h
ii. the temperature of the air at the exit, in °C
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