Jump to main content.

Module 2: Characteristics of Gases - Heat Capacity and Enthalpy - Practice Problems

Features

Instructions:: Work these problems on a sheet of paper and check your answers against those provided below.

#1: A gas mixture has a heat capacity of 10 Btu/(lb mole °F). How much heat is needed to increase the temperature of a 1,000 SCFM gas stream of this mixture by 500°F?

: Answer: 12,974 Btu/min; Solution:

#2: How much heat is needed to increase the temperature of 1.0 lb_m of oxygen from 200°F to 300°F? For enthalpy data, see Appendix A.

: Answer: 22.5 Btu; Solution:

In Appendix A, find the enthalpy of oxygen at 200°F and 300°F.
Calculate the amount of heat (enthalpy) required to heat 1.0 lb_m of oxygen from 200°F to 300°F.

#3: A VOC-laden air stream of 4,425 SCFM entering a thermal incinerator is at a temperature of 200°F. How much heat is needed to preheat the gas stream to 1,400°F to ensure oxidation of the VOC material? In solving the problem, use the enthalpy data for air and ignore the organic compounds present at levels less than 1,000 ppm (<0.1% volume). Use an average molecular weight of 29 lb_m/lb mole for the air stream. For enthalpy data, see Appendix A.

: Answer: 102,913 Btu/min; Solution:

Calculate the mass flow rate of air, in lb_m/min.
Calculate the enthalpy of the air at 1,400°F (interpolate value from Appendix A using the data provided for 1,000°F and 1,500°F).
Calculate the enthalpy change for air from 200°F to 1,400°F. For enthalpy data, see Appendix A.

#4: How much heat is required to heat 10,000 SCFM of nitrogen from 400°F to 2,000°F?

: Answer: 318,280 Btu/min; Solution:; Solve this problem using the following equation:

Use Appendix A to find the enthalpies of nitrogen at 400°F and 2,000°F.
Convert the gas flow rate to mass flow rate for nitrogen.
Calculate the total change in enthalpy during heating.

Return To Lesson
Heat Capacity and Enthalpy

Next Lesson
Viscosity

APTI Virtual Classroom

Local Navigation

Jump to main content.