Energy Transfer

ENERGY TRANSFER BY WORK (Cont’d)• Work done per unit time is called power and is denotedW (Figure 3-8). The unit of power is kJ/s or kW• Heat and work are directional quantities; requires thespecification of both the magnitude and direction; signconvention• Heat transfer to a system and work done by a systemare positive; heat transfer from a system and work doneon a system are negative• Use this intuitive approach in this book as it eliminatesthe need to adopt a formal sign conventionEnergy Transfer 7© Copyright 2005 Prof. Arun S. Mujumdar.