## Solution for Engineering Heat Transfer 2nd Edition Chapter 5, Problem 1

by William S. Janna
196 Solutions 12 Chapters 16002 Studied ISBN: 9780849321269 5 (1)

# Chapter 5, Problem Example 1 : Example 5.1. The specific heat at...

Example 5.1.

The specific heat at constant pressure is cp and at constant volume is c, Both vary with temperature for real substances. Values of specific heat are provided in the Appendix tables (B for solids, C for liquids, and D for gases). For ideal gases, it can be shown that a change in enthalpy equals the product of specific heat at constant pressure and temperature difference:

dh = c,dT

Likewise, for internal energy change of an ideal gas,

du = c,.dT

a piston and cylinder, as shown in Figure 5.3. The piston is free to move

vertically. (a) How much heat must be added to the carbon dioxide to

raise its temperature by 20 K? (b) How much heat must be added for

the same temperature increase if the piston is not free to move?

Solution 1 .

As heat is added, the CO, expands and forces the piston to move upward.

The expansion during heat addition essentially occurs at constant pressure

if the friction between the piston and cylinder is neglected. On the

other hand, for a constrained piston heat addition occurs at constant

volume. As heat is added, however, CO, nearest the walls heats first;

after mixing, due to natural convection effects, the heat is distributed uniformly

## Step-By-Step Solution

Example 5.1.

Solution 1 .

As heat is added, the CO, expands and forces the piston to move upward.

The expansion during heat addition essentially occurs at constant pressure

if the friction between the piston and cylinder is neglected. On the

other hand, for a constrained piston heat addition occurs at constant

volume. As heat is added, however, CO, nearest the walls heats first;

after mixing, due to natural convection effects, the heat is distributed uniformly