Question 1 A horizontal "hot air blower" consists of a fan, an electrical heating element and a nozzle Cool air Hot air Fan Heater Nozde The power input to the fan is 50 J/s and the power input to the heating element is 1.44 kJ/s. The air enters the fan with negligible velocity at a pressure of 1 bar and a temperature of 20 °C, the volumetric flow rate being 0.5 m³ /min. After passing over the heating element, the air leaves the nozzle with a velocity of 25 m/s and a pressure of 1.1 bar. Treating the complete arrangement as a steady flow system and ignoring any heat loss from the system, determine: (a) The mass flow rate of air entering the fan in kg per second (b) The kinetic energy of the air leaving the nozzle per second (c) The change in enthalpy of the air occurring per second between entering the fan and leaving the nozzle (d) The temperature of the air as it leaves the nozzle. (e) The density of the air as it leaves the nozzle (f) The flow area at the nozzle exit. Take R = 0.287 kJ/kgK and cp = 1.005 kJ/kgK %3D %3D

Question 1 A horizontal "hot air blower" consists of a fan, an electrical heating element and a nozzle Cool air Hot air Fan Heater Nozde The power input to the fan is 50 J/s and the power input to the heating element is 1.44 kJ/s. The air enters the fan with negligible velocity at a pressure of 1 bar and a temperature of 20 °C, the volumetric flow rate being 0.5 m³ /min. After passing over the heating element, the air leaves the nozzle with a velocity of 25 m/s and a pressure of 1.1 bar. Treating the complete arrangement as a steady flow system and ignoring any heat loss from the system, determine: (a) The mass flow rate of air entering the fan in kg per second (b) The kinetic energy of the air leaving the nozzle per second (c) The change in enthalpy of the air occurring per second between entering the fan and leaving the nozzle (d) The temperature of the air as it leaves the nozzle. (e) The density of the air as it leaves the nozzle (f) The flow area at the nozzle exit. Take R = 0.287 kJ/kgK and cp = 1.005 kJ/kgK %3D %3D

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter6: Forced Convection Over Exterior Surfaces

Section: Chapter Questions

Problem 6.8P

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