HVAC FINAL EXAM 2023 WITH QUESTIONS AND ANSWERS

HVAC FINAL EXAM 2023 WITH QUESTIONS AND ANSWERS Heat Transfer - ANSWER Moves from one substance to another as well as between molecules of a substance, temperature is the driving force Temperature - ANSWER The level of heat or heat intensity, measured with thermometers Heat - ANSWER Is the motion of molecules, and travels from a warm substance to a cold substance Conduction - ANSWER Energy travelling from one molecule to another, involves direct contact Radiation - ANSWER Passes through air and heats the first solid object it comes in contact with Sensible Heat - ANSWER Heat transfer that results in the change of temperature of a substance Convection - ANSWER Used to move heat from one location to another, and is energy travelling through a fluid from one substance to another Latent Heat - ANSWER Results in the change in state of a substance, its energy is stored when a liquid turns to gas, and released when a gas turns to a liquid. Specific Heat - ANSWER The amount of heat necessary to raise the temperature of 1lb of a substance 1 degree F. Matter - ANSWER A substance that occupies space and has mass, and is made up of atoms Mass - ANSWER Is the property of matter that responds to gravitational attraction. Density - ANSWER Describes a substance's mass to volume relationship Specific Gravity - ANSWER Is a unitless number because it is the density of a substance divided by the density of water. Water is used as a comparison. The density of water is 62.4 lb/ft^3 which equals 1, anything greater than 1 will sink anything less will sink. Specific Volume - ANSWER Indicates the volume that each pound of a gas occupies,when air is heated it volume increases and whens its cooled its volume decreases, one pound of clean dry air has a total volume of 13.33 ft^3. Law of conservation of energy - ANSWER States that energy is neither created or destroyed but can be converted from one form to another. One ton of refrigeration - ANSWER Is the amount of heat required to melt 1 ton of ice in a 24 hour period Temperature/Pressure Relationship - ANSWER Correlates the vapor pressure and the boiling point of water and is the basis for controlling a system's temperature. Refrigeration Process - ANSWER The boiling point of water can be changed and controlled by controlling the vapor pressure above the water Superheated - ANSWER A liquid under pressure above its boiling point without vaporization, is found my subtracting the evaporator outlet temp by the evaporator saturation temp. Low superheat means overfed coil high superheat means starved coil. should be 8-12 degrees of overall temprature for outlet inlet should be 10-20 degrees F. Saturated - ANSWER When the change of state is occurring and when the refrigerant is at equilibrium, and both liquid and gas are present. Subcooled - ANSWER Liquid cooler than the condensing saturation temperature. Refrigerant - ANSWER A substance that can be changed easily to a vapor by boiling it and then changed to a liquid by condensing it Evaporator - ANSWER Absorbs heat into the system, and turns the liquid refrigerant from the metering device to a vapor. Must be a temperature that is cooler than the air to be cooled, usually 10-20 degrees cooler in refrigeration and 35 degrees F cooler in air conditioning, Compressor - ANSWER Pumps heat through the system, and reduces the pressure on the low pressure side of the system and increases the pressure on the high pressure side Condenser - ANSWER Rejects heat, and take the high pressure gas from the compressor and turns the refrigerant into a liquid which gives off heat to the outside air, should be 30 degrees warmer than the outside air Metering Device (Expansion Device) - ANSWER Holds back the flow of