First Law of Thermodynamics Summary

• The First Law of Thermodynamics states that energy can neither be
created nor destroyed, only altered in form.


• In analyzing an open system using the First Law of Thermodynamics, the energy into the system is equal to the energy leaving the system.

• If the fluid passes through various processes and then eventually returns to the same state it began with, the system is said to have undergone a cyclic process. The first law is used to analyze a cyclic process.


• The energy entering any component is equal to the energy leaving that component at steady state.

• The amount of energy transferred across a heat exchanger is dependent
upon the temperature of the fluid entering the heat exchanger from both
sides and the flow rates of the fluids.

• A T-s diagram can be used to represent thermodynamic processes.