First Law and Energy Conversion

first law of thermodynamics

for all adiabatic processes between two specified states of a closed system, the net work done is the same regardless of the nature of the closed system and the details of the process

energy balanace

energy in - energy out = total change in energy of the system

energy change of a system

total change in energy = final energy - initial energy

= change in internal energy + change in kinetic energy + change in potential energy

is energy a property

yes, therefore the energy change is zero if the state of the system does not change

mechanisms of energy transfer

heat transfer, work transfer, mass flow (unless it is a closed mass system)

change in energy for a cycle

change in energy = 0

therefore Q = W

efficiency

indicates how well and energy conversion or transfer process is accomplished

efficiency = desired output/required input

heating value of fuel (HV)

the amount of heat released when a unit amount of fuel at room temperature is completely burned and the combustion products are cooled to the room temperature

generator

a device that converts mechanical energy to electrical energy

generator efficiency

the ration of the electrical power output to the mechanical power output

thermal efficiency of a power plant

the ratio of the net mechanical output to the rate of heat input

products of the combustion of fuel

carbon dioxide, nitrogen oxides, carbon monoxide, sulfur dioxide

benefits of energy-efficient appliances

helps the environment by reducing the amount of pollutants emitted to the atmosphere during the combustion of fuel