A) A gas-fired heat exchanger uses gas with energy value of 40MJ / m^3 at a rate of 0.4 m^3/h and produces 50kg/h of water at a temperature of 70^oC from feed water at 20^oC. The rest of the question is in the picture attached.PLZ help?
2 Answers
I got this
Explanation:
Let us calculate amount of heat required to raise the temperature of feed water at
Mass of water used in one hour
Rise in temperature
Useful heat
=>Q_u=50xx(4.19xx10^3)xx50
=>Q_u=10475000\ J
Heat produced by the gas in the heat exchanger in one hour
Q_p=0.4xx(40xx10^6)
=>Q_p=16000000\ J
Thermal efficiency of the heat exchanger
eta=10475000/16000000=0.65 , rounded to two decimal places.
Thermal efficiency
Explanation:
Start by working out how much energy is required to heat 50 kg of water from
Specific heat capacity of water =
so 50 kg raised 50 degrees will need
Energy
Energy/hr in from gas
so thermal efficiency is