### Control Volume Heat Transfer - Thermodynamics

**Thermodynamics Directory**** | Heat Transfer Directory**

*Control Volume Heat Transfer*

A *control volume *is a fixed region in space chosen for the thermodynamic study of mass andenergy balances for flowing systems. The boundary of the control volume may be a real orimaginary envelope. The *control surface *is the boundary of the control volume.

In fluid mechanics and thermodynamics , a **control volume **is a mathematical abstraction employed in the process of creating mathematical models of physical processes. In an inertial frame of reference , it is a volume fixed in space or moving with constant velocity through which the fluid ( gas or liquid ) flows. The surface enclosing the control volume is referred to as the **control surface **.

At steady state , a control volume can be thought of as an arbitrary volume in which the mass of the fluid remains constant. As fluid moves through the control volume, the mass entering the control volume is equal to the mass leaving the control volume. At steady state , and in the absence of work and heat transfer, the energy within the control volume remains constant. It is analogous to the classical mechanics concept of the free body diagram .