Compare and contrast piloted ignition and autoignition

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Reference no: EM131172128

Question 1. When a thermally thick solid is exposed to heat, we expect a(n):

slight rise in temperature incurred to both sides of the fuel surface due to the fast transfer and dissipation of the imposed heat flux on one side and transferred to the other.

substantial increase in temperature on the side facing the imposed heat flux, and the opposite side will incur a slower increase in temperature.

substantial increase in temperature on the opposite side, and the side facing the imposed heat flux will incur a slow increase in temperature.

immediate decrease in temperature incurred to both sides of the fuel surface due to the fast transfer and dissipation of the imposed heat flux on one side and transferred to the other.

Question 2. A shift from counterflow to concurrent flame spread will occur when the angle of incline increases past:

25

Question 3. What is spontaneous ignition?

The minimum temperature required for ignition of fuel gases under specific test conditions.

The temperature required to produce the lower flammable limit.

The temperature at which oxidation reactions will initiate within fuel/air mixtures without an outside pilot source.

A self-heating process with a significant increase in the rate of temperature rise, which continues to ignition.

Question 4. Radiant heat is emitted in what direction from the source?

90

180

270

360

Question 5. When the exposed fuel item only receives a portion of the radiant heat transfer from the burning item, this along with the distance between the objects is known as what?

The configuration/view factor

A heat shadow

A protected area

The exposure/line of sight factor

Question 6. Which of the following terms describes an instability that occurs when heat generation exceeds heat loss within the material?

Thermal runaway

Thermal resistance

Thermally unbalanced

Thermal Inertia

Question 7. Which of the following is the primary mode of heat transfer during combustion?

Conduction

Convection

Radiation

Heat flux

Question 8. Which of the following is NOT included in the convection heat transfer coefficient?

Fluid properties

Surface geometry

Nature of the fluid motion

Convective heat release

Question 9. Which of the following was NOT among the most common reported ignition sources cited in Chapter 11?

Cooking equipment

Heating equipment

Hair care devices

Electrical

Question 10. What is the term that describes energy transferred by the bulk motion of the fluid?

Advection

Conduction

Laminar flow

Convection.

Question 11. Describe the manner by which convection and radiation affect the spread of a freely burning fire.

Your response should be at least 75 words in length.

Question 12. Compare and contrast piloted ignition and autoignition.

Your response should be at least 75 words in length.

Question 13. A vertical sheet of cotton fabric, 0.5 mm thick, is immersed in a stream of hot air at 200ºC. Calculate how long it will take to reach 100ºC if the heat transfer coefficient is h = 20 W/m2K, r = 300 kg/m3 and c = 1,400 J/kg. Assume the initial temperature to be 25ºC (adapted from Drysdale, 1998).

Your answer should show your calculations and your answer must include the proper units.

Reference no: EM131172128

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