7. Heat Pumps The second law of thermodynamics Heat reservoir (Clausius statement) Heat generally cannot flow spontaneously from a material at lower temperature to a material at higher temperature PUMP Can we remove energy from a cold place and deliver it to a warmer place Can we run the heat engine backward? Cold Heat pump: a device using tc energy input in the form of work to cause the transfer of heat energy from the low T Figure 3.11 A thermodynamic diagram of a heat pump A work input. W. is required to transfer an amount of to the another reservoir with energy @cold, out of a cold reservoir and a larger amount higher T shot into a hot reservoir. Because energy is conserved Q hot must equal w+ocold7. Heat Pumps Figure 3.11 A thermodynamic diagram of a heat pump. A work input, W, is required to transfer an amount of energy Qcold, out of a cold reservoir and a larger amount, Qhot, into a hot reservoir. Because energy is conserved, Qhot must equal W + Qcold. The second law of thermodynamics (Clausius statement) Heat generally cannot flow spontaneously from a material at lower temperature to a material at higher temperature. Can we remove energy from a cold place and deliver it to a warmer place ? Can we run the heat engine backward? Heat pump: a device using energy input in the form of work to cause the transfer of heat energy from the low T to the another reservoir with higher T