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56 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What is absolute zero in C and F? |
-273 C -460 F Theoretical |
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What is the boiling point of water at sea level? |
100 C 212 F |
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What is atmospheric pressure at sea level? |
29.92 in HG 14.696 psia |
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What equation converts C to F? |
F= (1.8xC)+32 |
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What are the respective names of the absolute temperature scales for both F and C? |
F >>> Rankine scale C >>> Kelvin scale |
Named after inventors |
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True or false? 0 deg F on the Kelvin scale refers to absolute 0 and is also the temperature at which molecular motion stops altogether. |
False! 0 deg F does not belong on the Kelvin scale. |
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True or false? 0 deg C on the Kelvin scale refers to absolute 0 and is also the temperature at which molecular motion stops altogether. |
True |
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What is the first law of thermodynamics? |
Energy can neither be created nor destroyed |
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1 BTU refers to exactly how much heat energy? |
One BTU is the heat energy required to raise the temperature of 1 lb of water by 1 deg F |
Think beer/ pint |
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True or False? Convection is the only form of heat transfer that can occur in space? |
False! |
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True or False? Radiation is the only form of heat transfer that can occur in space? |
True! It does not rely on transfer of energy from one particle to another. Therefore this form of energy can travel in a vacuum |
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What is the rate at which radiant energy diminishes? |
Radiation diminishes by the inverse of the square of the distance travelled |
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What is the latent heat of vaporization/condensation for 1 lb of water/steam at 212 deg F? |
970.3 BTU per lb It refers to how much latent heat energy needs to be removed/added to create state change at this temperature |
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What is the term that refers to the energy required to create state change between solids and liquids? |
Latent heat of fusion |
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What is the significance of this value? 144 BTU |
144 BTU is the latent heat of fusion for water. We would require 144 btu of latent heat to change 1 lb of ice to a liquid at 32 deg f at sea level Or would need to remove 144 BTU of latent heat from 1 lb of water to change state to a solid at 32 deg F at sea level |
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What does the term superheating refer to? |
When you continue to raise the temperature (add sensible heat) to a substance that is already 100% saturated vapour (more simply: raising the temp beyond the boiling point) |
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How many BTU are required to change water (ice) from 0 deg f to 32 deg f ? |
16 BTU sensible heat 0.5 BTU per 1 deg f when below freezing point |
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How many BTU are required to change 1 lb of water (vapour) from 212 deg f to 250 deg f ? |
19 BTU 0.5 BTU per 1 lb when in its vapour state (superheating) |
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Specific heat refers to: |
The BTU per lb of a substance to change its temperature by 1 deg f |
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At sea level and approximately _______ deg F the mercury in a barometer will level out at _______ inches HG |
70 deg f 29.92 in HG |
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At sea level and approximately _______ deg F the mercury in a barometer will level out at _______ inches HG |
70 deg f 29.92 in HG |
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A typical field use barometer with a bellow is known as a ____________ barometer |
Aneroid |
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What is the conversion factor for psi to in HG? |
1 psi = 2” HG Round to 2 2.036 29.92/14.696 |
29.92/14.696 |
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Your refrigeration gauges utilize a _____________ gauge known as the low side that reads ___________ & ___________ atmospheric pressure. The high side gauge reads up to ________ psi |
Compound gauge Above & below 500 |
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Refrigeration gauges are dialed in to 0 PSIG which stands for _________________________. This starting point is also attuned to ____________ |
Pounds per square inch gauge pressure Atmospheric pressure 14.696 psi |
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PSIA refers to ____________________ and can be calculated by taking a gauge reading and adding ________ psi |
Pound per square inch absolute 14.696 |
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PSIA refers to ____________________ and can be calculated by taking a gauge reading and adding ________ psi |
Pound per square inch absolute 14.696 |
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Name the 4 temperature scales |
Celsius Fahrenheit Celsius absolute Fahrenheit absolute |
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True or false? Convection is the transfer of heat through a fluid |
True Liquid or vapour state….commonly understood via vapour state |
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What is the working component of a compound gauge that allows the needle to indicate pressures |
Bourdon tube |
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Specific gravity is the property used to compare ___________________ of various substances |
Density |
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Specific gravity is the property used to compare ___________________ of various substances |
Density |
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True or false? The British system measures density of substances by their weight per cubic meter |
False Cubic foot is used in the British system to measure density of substances |
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What is the concept behind Boyle’s law? |
The volume of a specific substance varies inversely with the absolute (psia) pressure assuming the temperature remains constant. In other words : Original pressure (P1) x original volume (V1) = new pressure (p2) x new volume (v2) |
Think of boiling water by only decreasing the pressure…I.o.w. Take the water way up into the sky and watch it boil at room temperature….the pressure dropped and the volume of the substance (water) increased |
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What is the concept behind Charles’ law? |
Charles law states that at a constant pressure the volume of a gas varies directly with the absolute temperature I.o.w Original Volume (V1) / Original Temperature (T1) = New volume (V2) / New temperature (T2) |
Think Charles dickens…guy was a real dick. Making the most obvious law possible and naming it after himself…but seriously his name was actually Jacques Charles |
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What is Dalton’s Law? |
That the total pressure of a confined mixture of gases is the sum of the pressures of each of the gases in the mixture |
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What is Dalton’s Law? |
That the total pressure of a confined mixture of gases is the sum of the pressures of each of the gases in the mixture |
Problem with having more than one doll in your life… the pressure just keeps adding up! |
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What is the general law of perfect gas? |
P1 x V1 / T1 = P2 x V2 / T2 |
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What is the difference between medium temperature and low temperature in the HVAC industry ? |
Medium temp is typically considered 35-45 deg f Low temp is below 0 deg f (also known as the food hardening zone) |
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What is the rate of flow you should you use with nitrogen while brazing? What else should be done before brazing? |
Before brazing, purge lines with nitrogen in direction of refrigerant flow. Remove shraeder cores Use 2-5 SCFH (standard cubic feet per hour) |
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True or false? Flux is required for brazing copper to copper |
False The phosphorus in the sil fos rods acts as a flux on the copper. And these systems are better off without too much. |
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What is 1 ton of cooling equivalent to in BTU? |
288,000 BTU OR The latent heat energy required to melt 2000 lb of ICE at 32 deg f (144x2000) |
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What is a refrigerant? |
A substance that can readily be vaporized from a liquid and condensed from a vapour without altering its characteristics |
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When does equilibrium occur referring to a refrigerant? What is another name we give refrigerant in this state? |
During a state change the refrigerant is considered to be in a state of equilibrium. It is also called saturated at this point Present in both vapour and liquid form |
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What is the average specific heat of air? |
0.24 |
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What is the density of water? |
Density: 62 lb/cu ft |
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What is the specific gravity of water? |
1.0 |
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What is the density of water? |
Density: 62 lb/cu ft |
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What is the specific gravity of water? |
1.0 |
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What is the equation for finding specific gravity for any substance? |
Take the density of the substance and Divide it by the density of water (62 lb/cu ft) I.e. wood (38 lb per cu ft): 38/62= 0.6 I.e. iron (480 lb per cu ft): 480/62=7.7 |
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What is the latent heat of sublimation of CO2? |
248 Btu/lb |
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What unit is used to measure relative humidity? |
Grains per pound (grains of water) I.e. 110 gr/lb at 70 deg f is 100% RH |
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What is the boiling point of water in Rankine? |
672 |
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What is the equation for converting psia into vacuum Inches mercury? |
Psia= 15-(“HG/2) |
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How do you determine the specific volume of a substance? |
Specific volume = 1 divided by specific density Formula works in the other direction as well… they are inverse (this is boyles law) Specific density = 1 divided by specific volume |
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What do the following numbers relate to?: - 660 - 273 - 460 - 970 - 180 - 62 |
660 is horsepower (660 lb lifted to 50 ft in 1 min) = 33,000 lb/ft/min 273 is Kelvin scale -273 absolute zero -460 Rankine scale absolute zero - 970 latent heat of vaporization of water - 180 degrees of sensible heat between 32 and 212 deg f - 62 lb/cu ft is the density of water |
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