calculate the power in watts that must be supplied to a 40-gallon electric water heater to raise the temperature of a tank of water from 50 degrees to 150 degrees in 2 hours. assume that no heat is wasted.( 1 gallo= 8 1/3 pounds) calculate the cost of heating the water at $0.04 per kilo watt per hour?
thanks and can you show me a solution too
again thanks a lot.
2007-09-07 12:42:14 · 1 answers · asked by nic 5 in Science & Mathematics ➔ Engineering
I'll help you set up the problem, but you'll have to finish your homework yourself.
1 BTU is the amount of heat required to raise the temperature of 1 lb of water 1 °F.
40 gallons x 8.33 lbs / gallon = 333 lbs.
ΔT = 150 - 50 = 100 °F
Raise 333 lbs of water 100 °F = _____ BTU's.
You can heat the water for two hours, so divide the energy needs by 2 hours. The resulting units are BTU's / hr.
1 watt is approximately 3.41 BTU/hr.
1 kW = 1000 watts.
___ kW x 2 hours = ____ kWh.
Cost to heat water is ___ kWh x $0.04 = $____
2007-09-07 13:55:55 · answer #1 · answered by Thomas C 6 · 3⤊ 0⤋