Problem 2. Electric Heating of a Room An air-tight room contains 80 kg of air, and a 2-kW baseboard electric resistance heater in the room is turned on and kept on for 15 min. Calculate the temperature rise of air at the end of 15 min.

The rise in temperature after 15mins is (ΔT)=°c

Explanation:

The solution is obtained from energy balance;

W=M x Cv x ΔT

where;

W(workdone)=quantity of energy in joules

Workdone=Power x Time

Power=2kw

Time=15mins=15 x 60=900secs

Workdone=2 x 900=1800KJ

Cv=Specific heat capacity of air= 0.718 kJ/kg.K

M=Mass of air=80kg

ΔT= change in temperature in °C

therefore;

ΔT=

ΔT=

ΔT=

ΔT=°c

The temperature rise of air at the end of 15 min is °C

Explanation:

Data

=0.718

We can use energy balance to solve the problem.

The energy balance stated that:

Δ

Δ

Δ

we can now make ΔT the subject of the formula

ΔT

substitute the values

ΔT

ΔT=°C

1

explanation:

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explanation: