MCC HVAC MIDTERM EXAM QUESTIONS WITH 100 % CORRECT ANSWERS | VERIFIED

List at least five factors that must be controlled if a comfortable indoor environment is to be maintained. - Answer-The factors that must be controlled include temperature, humidity, air motion, dust, bacteria, odors, toxic gases, and ionization. ((Ref: 1/1)) Describe in simple terms the basic process by which a refrigerant transfers heat energy. - Answer-A refrigerant is used to transfer heat when it changes states. When liquid refrigerant evaporates into a vapor, heat is absorbed by the vapor. When refrigerant vapor is condensed into a liquid, heat is rejected from the refrigerant. ((Ref: 2/3)) In your own words, state the first law of thermodynamics. - Answer-Energy can neither be created nor destroyed, but can be changed from one form into another. ((Ref: 3/2)) Define work. - Answer-A force moving an object in the direction of the force. ((Ref: 3/3)) One horsepower (1 hp) of mechanical energy is equivalent to ______watts of electrical energy, and one watt (1 W) of electrical energy is equivalent to ________ Btu of heat energy. - Answer-746 Watts, 3.413 Btu ((Ref: 3/4, 5)) In your own words, state the second law of thermodynamics. - Answer-A temperature difference must exist between two materials in order for heat energy to travel. ((Ref: 3/7))Heat always travels from a(n) _____ material to a(n) ______ material. - Answer-Higher-temperature, lower-temperature. ((Ref: 37-4/1)) Temperature is a measurement of heat _____. British thermal units and calories are measurements of heat _____. - Answer-Intensity, quantity ((Ref: 5/1)) What is the difference between latent heat and sensible heat? - Answer-Latent heat causes a change in the state of a substance without a change in its temperature. Sensible heat causes a change in the temperature of substance without a change in its state. ((Ref: 6/1)) The latent heat of _____ causes a change in phase from vapor to liquid. The latent heat of _____ causes a change in phase from liquid to vapor. - Answer-Condensation, vaporization. ((Ref: 6/1)) What is specific heat? - Answer-Specific heat is the energy required to raise the temperature of 1 lb of a substance by 1 degree F. ((Ref: 6/3)) What is superheat? - Answer-Superheat is energy that raises the temperature of a vapor above its saturation temperature. ((Ref: 6/4)) Convert 68 degrees F to an equivalent Celsius temperature. - Answer-68 degrees minus 32, divided by 1.8 = 20 degrees Celsius((Ref: 7/2)) Convert 25 degrees Celsius to an equivalent Fahrenheit temperature. - Answer-25 times 1.8, plus 32 ((Ref: 7/2)) Absolute zero on the Fahrenheit scale is _____ ^0F - Answer--460 degrees F ((Ref: 7/2)) Define pressure - Answer-Force per unit of area. ((Ref: 8/2)) One atmosphere of pressure (atmospheric pressure at sea level) is equivalent to _____ psia. - Answer-14.696 psia