CHAPTER 4 The First Law of Thermodynamics – Pipe Flow and Unsteady Flow Processes

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-8 FIGURE 4-46 Pipe or duct flow may involve more than one form of work at the same time.

Unsteady Flow Processes Mass balance: m in – m out = Δm system Assume uniform flow process –The fluid flow at any inlet or exit is uniform and steady. –Therefore, fluid properties do not change with time or position over the cross section. –If they do, then average them.

Unsteady Flow Processes Energy balance : E in – E out = ΔE system If i is for inlet and e is for exit, and If 1 is for before and 2 is for after: Then, whittle it down! What happens if the inlets and exits are closed? What is left?

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4-9 FIGURE 4-53 Schematic for Example 4– 17.