What is the change in the internal energy, in btu/lbm, of air as its temperature changes from 100 to 200°f? is there any difference if the temperature were to change from 0 to 100°f? the constant-volume specific heat of air at room temperature is cv = 0.171 btu/lbm·r. consider the variation of specific heat with temperature. cv = 0.1725 btu/lbm·r at 150°f and cv = 0.1712 btu/lbm·r at 50°f.