An air conditioner takes outside air at 35°c and cools it to 15°c at a rate of 1 kg/s. estimate the amount of power needed to do this. recalculate the needed power if it is put in recirculation mode using inside air at 24°c and cools that to 15°c.

Q=20.1kW

recirculation mode=Q=9.045kW

Explanation:

Hi!

To solve this problem you must use the first law of thermodynamics that establishes the energy that enters a system is the same that must come out. Given the above we have the following equation

Q = mCp (T2-T1)

WHERE

Q = Heat removed to air

m = mass air flow = 1kg / s

Cp = specific heat of air = 1.005KJ / kg °C

T2 = air inlet temperature

T1 = air outlet temperature=15°C.

for the first case

Q=(1kg/s)(1.005KJ/kg°C)(35°C-15°C)

Q=20.1kW

for the second case( recirculation mode)

Q=(1kg/s)(1.005KJ/kg°C)(24°C-15°C)

Q=9.045kW

the warning light flashes for a second or two when the engine starts. if it stays on, there's must be something wrong with the coolant. you should never dare to continue driving when the light is on. pull over as soon as possible and shut the engine off.

hope this is what you're talking about