PPT Slide

Example: Electric heater is often used in houses to provide heating during winter

months. It consists of a simple duct with coiled resistance wires as shown. Consider

a 20 kW heating system such that the air enters at 100 kPa and 17° C with a mass

flow rate of 2 kg/s. If it is known that the air leaves the duct with an exit temperature

of 27° C (same pressure), determine the heat loss from the duct.

dEg/dt=20 kW

Heat loss dQ/dt=?

To=27° C

To=17° C

Assume: steady state, negligible

KE and PE changes, air can be

considered as idea gas