m=ρv=10^3Kg/m^3X0.2m^3=200Kg
Q吸=cmΔt=4.2X10^3J/(Kg.℃)X200KgX(45℃-20℃)=2.1X10^6J
Q吸=Q放η
=mqη
m=Q吸/qη=2.1X10^6J÷(4.2X10^7J/kgX0.4)=0.125Kg
m=ρv=10^3Kg/m^3X0.2m^3=200Kg
Q吸=cmΔt=4.2X10^3J/(Kg.℃)X200KgX(45℃-20℃)=2.1X10^6J
Q吸=Q放η
=mqη
m=Q吸/qη=2.1X10^6J÷(4.2X10^7J/kgX0.4)=0.125Kg