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The Heat Plume of a Fire

Thermodynamics

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Safety Checklist for Fire Activities

Wear appropriate Personal Protective Equipment [PPE].

100% cotton clothing; safety goggles; closed-toed shoes

Tie back loose sleeves and long hair.
Make sure a charged fire extinguisher is close. Know how to use it.
Make sure each station has a spray bottle that is filled with water.
Always be aware of the fire’s location. Never lean over the fire!
Extinguish burned materials with water before putting them in the trash. Fire is not out if there is any smoke or heat coming from the fuels.
If a fire starts on you … Stop! Drop! and Roll!

An instructor must be present for fire to be used.

(Adapted from the USFS “FireWorks Safety Poster”)

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Safety Quiz

1) What material should clothing be made of when conducting an activity with a flame/fire?

a) Polyester

b) Cotton

c) Gore-tex

d) Nylon

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Safety Quiz

2) What type of footwear must be worn when conducting experiments with fire?

a) Closed-toed shoes

b) Sandals

c) None / Going barefoot is best

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Safety Quiz

3) What should be done with loose sleeves and/or long hair before beginning an activity with flame/fire?

a) Should be tied back

b) Should be cut off

c) Should be moistened with water

d) Nothing

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Safety Quiz

4) If a charged fire extinguisher is available in the classroom, does each lab station need to have a spray bottle filled with water?

YES

NO

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Safety Quiz

5) If a student already wears glasses, do they need to wear safety glasses/goggles?

YES

NO

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Safety Quiz

6) Fire is not out if there is any smoke or heat coming from the fuels.

TRUE

FALSE

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How Is Heat Energy Transferred?

Convection - heat moves by the circulatory motion that occurs in a fluid of non-uniform temperature as a result of the variations in density and the effect of gravity

(A fluid can be a gas or a liquid)

Who can tell me one of the mechanisms that heat can be transferred? Convection, Conduction, and Radiation. Any other ways that heat can move? Okay, let’s go over the three mechanisms of heat transfer in some detail. On your worksheet, draw a diagram that depicts heat being transferred by each mechanism. Click Read the statement for convection. Heat can be transferred by hot fluids as they “expand” into the cooler fluids surrounding them (hot gases/liquids are less dense than cooler fluids, so hot gases/liquids rise and are replaced by “falling” cooler fluids. For gases in air, Earth’s atmosphere usually becomes “thinner” (less dense) as you go up in altitude, so “up” has less resistance to the expanding gases than “sideways” or “down.” Therefore, hot air generally rises. Click Here are a few examples of the convection mechanism you may already be familiar with: Click a hot air balloon; Click smoke going up through a chimney; and Click coastal breezes. Click

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How Is Heat Energy Transferred?

Conduction - heat is transferred through direct contact between atoms/molecules in materials

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How Is Heat Energy Transferred?

Radiation - heat energy can move as radiant energy (electromagnetic waves or photons)

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Objective of Activity

Your objective is to describe the shape of the heat plume produced by a single, downward-pointing match.

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Group Member Roles

Observer - will detect a change in temperature a distance from a burning match

Always begin at least 30 cm away from the burning match
The point is to detect heat, not to determine how much heat you can tolerate!
Never place hand closer than 3 cm from the flame
Never place hand directly beneath the flame

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Group Member Roles

Measurer - measures the distance from the flame to where the observer detected a change in temperature

When the observer’s hand stops because heat has been detected, measure the distance from the flame to the observer’s hand
Do not place the ruler too close to or in the flame
3 cm is the closest point allowed even if heat has not been detected

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Group Member Roles

Igniter - lights the match with a stove lighter
Recorder - records measurements
Safety Monitor - ensures that the activity is conducted safely

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Heat Plume Diagram

At each station, there is a laminated graph sheet that looks like this. Before you can finish the activity, you must make a diagram reflecting your data on this sheet. You must get the instructor’s initials on the student worksheet before moving on to answer questions. Be prepared to explain your group’s heat plume using the three heat transfer mechanisms. When you have finished the activity, be sure to clean up your group’s station appropriately; the laboratory station should be in exactly the same condition as it was when your group began the activity. Be sure all matches are out before they are disposed of; there is no smoke and no heat being released. Use the metal bucket in the activity area for match disposal. If in doubt, use the station’s spray bottle to wet the matches before putting them in the metal bucket.

STOP!

The next slide shows the heat plume of a match pointed downward. This might be good to show after students have finished. Click

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Match Pointing Downward