Mechanical Engineering and Refrigeration Review Notes

Flashcards covering terminology and definitions from lecture notes on thermodynamics, refrigeration systems, boiler operation, fuel properties, and kinematics.

Chiller

A heat exchanger in which low-pressure refrigerant boils or vaporizes, thus absorbing heat that was removed from the refrigerated area by the cooling medium (water).

Flooded refrigeration system

A type of refrigeration system where only part of the circulated refrigerant is evaporated, with the remainder being separated from the vapor and then recirculated.

Frigorific mixture

Mixtures or substances used in laboratory methods of producing a drop in temperature, such as a mixture of ice and salt.

Reaumur Scale

A scale of temperature in which the melting point of ice is taken as $0^{\circ}$ and the boiling point of water is $80^{\circ}$.

British thermal unit (Btu)

The amount of heat energy required to raise the temperature of one pound of water one degree Fahrenheit; specifically $1/180$ of the heat required to raise the temperature of one pound of water from $32$ to $212^{\circ}F$ at a constant atmospheric pressure of $14.696\,psi$ absolute.

Critical temperature

The maximum temperature of any gas or vapor at which it may be condensed into a liquid; above this temperature, condensation is impossible regardless of the pressure applied.

Halogenated refrigerants (Freon)

A group of refrigerants developed since about 1925 to overcome the irritating or toxic effects of substances like ammonia and sulfur dioxide.

Evaporative condenser

A component that combines the functions of a cooling tower and a condenser, consisting of a casing enclosing a fan, water eliminators, refrigerant condensing coil, water pan, and spray pump.

Fouling factor

A factor used in calculating overall heat transfer through tube walls that includes the sum of the heat transfer rate of the layer of dirt and foreign material on the water side.

Refrigerant control

The standardized term used by the industry to describe any device that meters or regulates the flow of liquid refrigerant to an evaporator.

Flash steam

Steam produced from condensate passing from high-pressure systems to low-pressure systems.

Deluge system

A system employing open sprinklers attached to piping connected to a water supply, opened by the operation of a fire detection system.

Space cooling load

The rate, in $Btu/h$ or $W$, at which heat must be removed from a conditioned space to maintain a constant temperature and acceptable relative humidity.

Metabolism

The process the body uses to convert energy in food into heat and work, determining the rate at which chemical energy is converted to thermal form.

Clo units

The unit used to describe the insulating value of clothing.

Mean radiant temperature

The basic index used to describe the radiant conditions in a space; it is the mean temperature of an individual's exposed surfaces in the environment.

Hygroscopic materials

Substances that are particularly variable in the moisture content they can possess at different times.

Regain

The hygroscopic moisture content of a substance expressed as a percentage of the bone-dry-weight of the material.

Higher heating value

The heating value of a fuel if the water in the products of combustion is in the liquid state.

Coil load

The rate, in $Btu/h$ or $W$, of heat transfer at the coil, where the cooling component is the rate at which heat is removed by chilled water or absorbed by refrigerant.

Hygrometer

A mechanical or electronic humidity sensor used to measure relative humidity, dew point, or absolute humidity of ambient or moving air.

Automatic Valve

A device designed to control the flow of steam, water, or gas, functioning as a variable orifice positioned by an actuator respond to controller signals.

Surge tank

A component in a hydro plant that absorbs water hammer during load fluctuations and serves as an auxiliary reservoir during high load demands.

Coking coal

A bituminous coal containing plenty of hydrocarbons that forms lumped masses when burned, ideal for forming carbonaceous gases for ore reduction.

Flash point

The temperature to which oil has to be heated until sufficient flammable vapor is driven off to flash when brought into momentary contact with a flame.

Fire point

The temperature at which oil vapors will continue to burn when ignited.

Bloom

The color of a lubricating oil as seen by reflected light.

Carbon residue

The material left after heating an oil under specified high-temperature conditions, used as a quality control tool in refining viscous oils.

Cloud point

The temperature at which initial wax crystal formation becomes visible in oil when cooled under specific test conditions.

Pour point

The temperature at which cooled oil will just flow under specific test conditions, indicating the lowest temperature for ready flow.

Detergents

Engine oil additives used to help keep the engine clean by solubilizing and dispersing sludge, soot, and deposit precursors.

Viscosity-index improvers

Engine oil additives used to enable adequate low-temperature flow along with sufficient viscosity at high temperatures.

Acoustic velocity

The speed of sound, or the velocity at which a small pressure wave moves through a fluid.

Miniature boiler

A boiler not exceeding $405\,mm$ inside diameter, $1065\,mm$ overall length, $1.85\,m^2$ of water heating surface, and $7.03\,kg/cm^2$ maximum allowable working pressure.

Condemned boiler

A boiler that has been inspected and declared unsafe to operate or disqualified, and marked indicating its rejection.

Reinstalled boiler

A boiler removed from its original setting and re-erected at the same location or erected at a location without change of ownership.

Desuperheating

A process in which superheated steam is either restored to its saturated state or its superheated temperature is reduced.

Maximum Allowable Working Pressure (MAWP)

The maximum pressure at which a pressure vessel or boiler is permitted to operate safely.

Cyclonic Spray Scrubber

Dust removal equipment consisting of a cylindrical tank with tangential openings and a center spray manifold where gas revolves and contacts water spray to separate dust.

Trunk piston engine

An engine in which the connecting rod is directly connected to the piston wristpin, and side thrust is taken by the piston against the cylinder wall.

Surface-ignition engine

An internal combustion engine where fuel ignition is accomplished partly or entirely by heat sources other than compression, such as a hot tube, plate, or bulb.

Reciprocating pump builder's plate notation (e.g., $3 \times 4 \times 6$)

A standard stamp where the first number is the steam cylinder diameter, the second is the liquid cylinder diameter ($4\,inches$), and the third is the stroke length ($6\,inches$).

Kinematics

The science of motion that deals with the motion of bodies without reference to the forces that cause them.

Inertia

A property of matter which causes it to resist any change in its motion or state of rest.

Higher pair

A kinematic pair having point or line contact between the elements when in motion, such as a cam with a roller follower.

Elastic limit

The maximum stress to which a standardized test specimen may be subjected without permanent deformation.

Killed steel

Steel deoxidized with strong agents such as silicon or aluminum to eliminate the reaction between carbon and oxygen during solidification.

Cavitation

A phenomenon occurring in pumps when pressure goes below the vapor pressure, appearing as pitting, noise, and decreased capacity due to collapsing vapor bubbles.

Specific speed

A dimensionless value for a given impeller of a centrifugal pump that remains constant regardless of rotative speed.

Available NPSH formula

$NPSH = H_b - H_v - Z + h_f$ (where $H_b$ is surface absolute pressure head, $H_v$ is vapor pressure head, $Z$ is height, and $h_f$ is friction head loss).