NFI Exam Review Questions And Complete Answers Graded A+ 2024.
Combustion Requirements (3) - Answer Air, Fuel, Heat
Complete Combustion Produces (4) - Answer Water vapor, carbon dioxide, heat, and non combustible ashes
incomplete combustion produces (3) - Answer carbon monoxide, hydrocarbons, and other gases
rate at which fuel burns is controlled by - Answer the amount of available air
air to fuel ratio is a - Answer critical factor in obtaining optimum fuel combustion
BTU - Answer British Thermal Unit, The amount of energy needed to heat one pound of water one degree Fahrenheit
wood ignites at - Answer 450-550 F
natural gas ignites at - Answer 1,150 F
propane ignites at - Answer 920-1120 F
electric spark temp - Answer 1,700 F
hot surface igniter temp - Answer 2,400 F butane lighter temp - Answer 3,200 F
stick match temp - Answer 3,000 F
cigarette temp - Answer 500-800 F
For complete combustion: air is ______ % oxygen + _____ % nitrogen - Answer 20 : 80
for complete combustion, __(QTY)__ molecules of __(PART)___ need to be mixed with ___(QTY)__ molecule of _____(PART)____ in the presence of __(PART)__ - Answer 2 oxygen : 1 fuel : heat
When complete combustion happens __(4 things)___ are released - Answer heat, carbon dioxide (C02),
water vapor (H20), and nitrogen (N)
Carbon monoxide is dangerous because (other than senseless) - Answer it mixes with blood and reduces oxygen carrying capacity
Aldehydes - Answer chemical compounds that have a strong pungent odor
Carbon monoxide is ________ when aldehydes are present - Answer present
Aldehydes result from - Answer flame impingement and through the presence of contaminated air
Efficiency formula - Answer Heat output divided by heat input (percentage of heat transferred to room)
3 Ts of efficiency - Answer Temperature, turbulence, time
Temperature (efficiency) - Answer minimum ignition temp Turbulence (efficiency) - Answer fuel must collide with oxygen molecules (refers to the degree of fuel and air mixing that occurs in combustion zone)
Time (efficiency) - Answer amount of time fuel gases remain in the high temp zone. also known as "residence time"
Heat Transfer Efficiency - Answer refers to the percentage of heat generated by combustion actually transferred to room
High heat transfer efficiency is normally associated with: (5 things) - Answer Appliance having proportionally large exterior surfaces with good heat radiating properties
Long residence time of the hot gases in the Appliance Adequate turbulence inside the appliance to property transfer heat from the fire chamber to appliance walls
Rapid heat transfer through the walls of the appliance
Adequate air movement (convection) outside
2 types of factory built fireplaces - Answer radiating and circulating
Radiant design - Answer transmits heat energy from firebox opening by direct radiation to the space in front of it. (do not have grills or louvers on the face, heat moving blowers not avail.)
circulating design - Answer adds function of heat transfer via heated air convection by circulating air around the fire chamber and releasing into space to be heated through grills and louvers
Built-in, high efficiency fireplaces - Answer contain efficient combustion and convection champers that are enclosed in an insulated metal cabinet. Can be enclosed in close proximity to combustibles
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