MODULE 5 Heating Production Equipment and Systems
The calculation examples are shown in an accordion-style display. Some questions are accompanied by equations and/or tables for quick reference. Solve the problem on your own and then click on the question to view the solution. This will help you make sense of the work as you read through the problem-solving process.
1.
If gas is available at $0.50 per therm and #2 oil is available at $1.00 per gallon, which will be the more, economical fuel source on the basis of cost per Btu (assume equal efficiencies)?
A therm of gas contains 100,000 Btu for $0.50, or 200,000 Btu per dollar. A gallon of oil contains 143,000 Btu for $1.00. Gas will be more economical.
2.
If gas is available at $0.50 per therm and the efficiency of utilization is 80%, what is the net cost of heating energy in dollars per million Btu?
One million Btu will require 1,000,000 ⁄ (0.80 x 100,000) , or 12.5 therms. At $0.50 per therm, the cost per million is 12.5 × $0.50, or $6.25.
3.
If electric is available at $0.1 per kWh, what is the cost of electric for heating in dollars per million Btu?
One million Btu will require 1,000,000⁄ 3413 , or 293 kWh. At $0.10 per kWh, the cost of 1,000,000 Btu is $0.10 × 293, or $29.30.
4.
What is the natural draft (in. w.c.) created by a chimney 120 feet tall with a mean chimney temperature of 400°F and the ambient temperature of 65°F?
The draft D t is 0.69 in. water column.