Staying Warm in the Winter

Canadian winters are characterized by long, dark, and very cold nights. To stay warm we generally heat our homes with natural gas, home heating oil, or electricity. In most cities and towns natural gas in the most common fuel used for home heating.

Natural gas has the advantage of being a clean burning fuel, and unlike heating oil, natural gas does not require on-site storage facilities since it is pumped directly into our homes under pressure, in much the same way that city water is pumped into our homes.

Energy For Heating

Natural Gas *

There are three reactions shown below, all representing the combustion of methane, but each describing the process differently. For our purposes, the third (mass) equation is the most important.

One molecule of methane plus two molecules of oxygen will burn to produce two molecules of water, one molecule of carbon dioxide, and heat.


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Molecular equation

Word Equation

Mass equation

Transparency Master		 Methane is slightly less dense than air. At standard atmospheric pressure and temperature one cubic metre of air has a mass of about 1 kilogram. Methane gas is slightly less than 1 kilogram per cubic metre.

Natural gas is generally purchased by the cubic metre.

The graph to the left uses an approximate density of 0.7kg/m3 for methane for conversion from kilograms of fuel to cubic metres of fuel.

Activity 1

Answer Key

Home Heating Oil *

There are three reactions shown below, all representing the combustion of heating oil, but each describing the process differently. For our purposes, the third (mass) equation is the most important.

Two molecular segments (-CH2-) of heating oil (primarily light paraffins) plus three molecules of oxygen will burn to produce two molecules of water, two molecules of carbon dioxide, and heat.


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Molecular equation

Word Equation

Mass equation

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The chart uses a specific gravity for heating oil of approximately 0.9		 Petroleum-based fuels are complex blends of various hydrocarbon molecules.

Each blend is formulated for a specific application. That is why one should never swap conventional gasoline and diesel fuel or kerosene and naphtha gas. Even within each of these types of fuels there are different blends.

The fact that there are numerous molecular blends of even common heating oil, it is difficult to characterize the combustion of heating oil by a single molecule.

Luckily iso-paraffins are common in heating oil and do in fact serve to provide a good model for the combustion characteristics of heating oil.

Activity 2

Answer Key

Wood


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Dry Hardwood 1 cord = 3.6m3		 Wood is a complex material. Its specific gravity ranges from less than 0.1 (dry balsa) to more than 1.0 (green oak).

The great range is partially due to the cellular structure of the wood and partially due to its water content.

The amount of energy extracted from burning wood depends greatly upon the dryness of the wood, the species of the wood and the efficiency of the furnace.

In general, dry hardwoods burned in high efficency "air-tight" furnaces yield the most efficient energy extraction from the burning process, however, the burning usually takes place more slowly than in an air enriched environment.

The former process (air-tight) provides the best efficiency, the latter (air enriched) provides the most heat in the shortest possible time..but it is very inefficient.
* Footnote: Fossil fuels are a complex blend of hundreds of kinds of hydrocarbon molecules. The molecules and molecular segments which are used in these examples are the most abundant in the fuel being described, and as such, represent a good approximation of the entire combustion process.

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