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Glossary: B

Back pressure
Pressure in low side of refrigerating systems; also called suction pressure or low-side pressure.

Back seating
Fluid opening/closing such as a gauge opening; to seat the joint where the valve stem goes through the valve body.

Bacteria
A form of unicellular microorganisms.

Baffle
Plate or vane used to direct movement of a fluid within a confined area.

Balance point
The point at which the heating capacity of a heat pumps equal to the heat losses of the structure it is heating.

Ball valve
A check valve that uses a ball to permit flow in one direction only.

Bar
Unit of pressure. One bar equals .9869 atmosphere (approximately one atmosphere, 14.51 psi).

Barometer
Instrument for measuring atmospheric pressure.

Bath
Liquid solution used for cleaning, plating, or maintaining a specified temperature.

Battery
Electricity-producing cells that use interaction of metals and chemicals to create electrical current flow.

Baudelot cooler
Heat exchanger in which water flows by gravity over the outside of tubes or plates.

Bearing
Low-friction device for supporting and aligning a moving part.

Bellows
Corrugated cylindrical container that moves as pressures change, or provides a seal during movement of parts.

Bellows seal
Method of sealing the valve stem. The ends of the sealing material are fastened to the bonnet and to the stem. Seal expands and contracts with the stem level.

Belt
A rubber-like, continuous loop placed between two or more pulleys to transfer rotary motion.

Bending spring
Coil spring that is placed on inside or outside of tubing to keep it from collapsing while bending.

Bernoulli's Theorem
In stream of liquid, the sum of elevation head, pressure head, and velocity remains constant along any line of flow, provided no work is done by or upon liquid on course of its flow; decreases in proportion to energy lost in flow.

Bimetal strip
Temperature regulating or indicating device that works on the principle that two dissimilar metals with unequal expansion rates, welded together, will bend as temperatures change.

Bioaerosals
Airborne microorganisms derived from viruses, bacteria, fungi, protozoa, mites, and pollen.

Blast freezer
Low-temperature evaporator that uses a fan to force air over that evaporator surface.

Bleeding
Slowly reducing the pressure of liquid or gas from a system by opening a valve slightly.

Bleed valve
Valve with small opening inside that permits a minimum fluid flow when valve is closed.

Blend
A mixture of various refrigerants.

Blown
With respect to fuses, a fuse that has been melted, breaking the electric circuit and preventing overload.

Boiler
Closed container in which a liquid may be heated and vaporized.

Boiler, high-pressure
A boiler operating with water temperature and water pressure above low-pressure boiler ratings.

Boiler horsepower
Seldom-used term equivalent to a heating capacity of 33,475 Btu/hr. (9804 watts).

Boiler, low-pressure
A boiler operating with up to 250F (121C) water temperature and 160 psi water pressure or less.

Boiling point
The temperature of a liquid at which it changes to a gas under a pressure of 14.7 psia (101.3 kPa).

Boiling temperature
Temperature at which a fluid changes form a liquid to a gas.

Bonnet
In a furnace, the sheet metal chamber where heat collects before being distributed.

Booster
Common term applied to the use of a compressor as the first stage in a cascade refrigerating system.

Bore
Diameter of a hole. Inside diameter of a cylinder.

Bourdon tube
Thin-walled tube of elastic metal flattened and bent into a circular shape that tends to straighten as inside pressure is increased. Used in pressure gauges.

Boyle's Law
Law of Physics: The volume and pressure of a gas vary inversely if the temperature remains the same. Example: If the pressure is doubled on a quantity of gas, its volume is reduced one-half. If the volume is doubled, gas has its pressure reduced by one-half.

Brazing
Method of joining metals with nonferrous (without iron) filler using heat between 800F (427C) and the melting point of base metals.

Breaker strip
Strip of wood or plastic used to cover the joint between the outside case and inside liner of the refrigerator.

Breeching
Space in hot water or steam boilers between the end of the tubing and the jacket.

Brine
Water saturated with a chemical such as salt.

British thermal unit (Btu)
Quantity of heat required to raise temperature of one pound of water one degree Fahrenheit.

Building Related Illness (BRI)
An illness caused by an airborne virus in a building.

Built-up terminal
Electrical terminal attached to a compressor dome.

Bulb, sensitive
Part of sealed fluid device that reacts to temperature. Used to measure temperature or to control a mechanism.

Bunker
Space where ice or cooling element is placed in commercial installations.

Burner
Device in which burning of fuel takes place.

Butane
Liquid hydrocarbon (C4H10) commonly used as fuel for heating purposes.

Bypass
Passage around a regular passage.

Bypass cycle
A cycle using a bypass line with either hot gas or liquid used to defrost an evaporator or for low pressure control.

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