Glossary of Power Engineering Terms
H
| Term | Definition |
|---|---|
| HALF SECTION |
Used when only half of the view is to be drawn in section and the other half is not. |
| HALOGEN |
A compound consisting of chlorine, bromine, iodine and fluorine. |
| HALON EXTINGUISHERS |
A gaseous extinguishing agent that does not leave residue after discharge. It works on the principle of removing the air for combustion thus extinguishing the fire. |
| HANDHOLE |
An opening into a boiler drum or vessel that is much smaller than the manhole and is used for cleaning and inspection purposes. |
| HARDNESS |
A property that causes the material to resist indentation or abrasion. |
| HAZARDOUS WASTE |
Defined in WHMIS as a controlled product that is intended for disposal or is sold for recycling or recovery. |
| HEAD PRESSURE |
The static pressure of a fluid expressed in terms of the height of a column of the fluid. |
| HEADER |
A pipe that collects steam or water from or distributes it to a number locations. |
| HEADS |
The ends which close off the ends of the boiler shell; may also be referred to as 'end plates' or, in fire tube boilers, as 'tube sheets'. |
| HEAT |
A form of thermal energy due to the activity of the molecules in a mass and that can be transferred from one body to another. |
| HEAT EXCHANGER |
Anything that transfers heat from one substance to another without allowing the substances to mix. |
| HEAT OF CONDENSATION |
Latent heat given up in changing from a gas to a liquid. |
| HEAT OF FUSION |
Latent heat absorbed in changing from a solid to a liquid. |
| HEAT PUMP |
A heat transfer device that uses the heat rejected by a refrigeration process to provide heat. A combined cooling and heating unit. |
| HEAT RECOVERY SYSTEM |
Equipment that is installed to reclaim heat that is normally lost during the blow-down process. |
| HEAT TRANSFER |
The movement or transfer of heat from one medium to another. |
| HEATING LOAD |
The amount of heat lost by a building through walls, roof, windows, doors, etc. |
| HEATING SURFACE |
Parts of a boiler through which heat is transferred, from the combustion of fuel, to water or steam; the part of the boiler that has heat and combustion gases on one side and water or steam on the other. |
| HEATING VALUE |
The amount of heat stored in a unit mass of fuel (kJ/kg). |
| HEAVY WATER |
Water used as a cooling medium in a CANDU nuclear reactor; The hydrogen atoms that make up the water have an atomic weight of 2 due to the presence of a neutron in the nucleus. |
| HERMETICALLY SEALED UNIT |
A refrigerating unit in which the compressor and compressor motor are sealed in the same housing, with no external shaft or shaft seal and the compressor motor operating in the refrigerant atmosphere. |
| HERTZ (HZ) |
The SI unit of frequency equal to one cycle per second. |
| HIGH PRESSURE STEAM BOILER |
A steam boiler operating at pressures above 103 kPa. |
| HIGH SIDE |
The sections of a refrigeration system which operate at the high discharge pressure of a compressor or pump i.e. Condenser. |
| HIGHEST COMMON FACTOR (HCF) |
The highest factor in which all numbers in a group can be divided into evenly without a remainder. |
| HOG FUEL |
Waste wood used for fuel consisting mostly of bark and wood particles. |
| HOIST |
A mechanical device used for raising and lowering heavy loads. |
| HORIZONTAL |
Lines parallel to the horizon and at right angles to a vertical plane. |
| HORIZONTAL MISALIGNMENT |
Parallel or angular misalignment between two shafts as viewed from above (plan view). |
| HOT DECK |
The section of a mixed air zoning system containing the heating elements. |