Glossary - Letter H

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(from the Greek halieus, fisherman) - Adjective that designates what is related to fishing (example: fishery reserves). Feminine noun: halieutics is the set of disciplines dealing with fishing issues.


In the field of statistical thermodynamics today, heat refers to the transfer of the thermal agitation of the particles making up matter. It is what happens, for example, when two materials of different temperatures come into contact: the hotter material releases energy to the cooler material in the form of heat, a process known as heat (thermal) transfer. Care should be taken to avoid confusing heat, or thermal energy transfer, with temperature. Temperature is a state function. It reflects on a macroscopic scale the microscopic agitation, or kinetic energy, of the particles of a material or system.

Heat Pipe

A heat pipe is a device that conducts heat. Discovered in 1930, it employs a closed system containing a fluid in vapor-liquid equilibrium. At the hot interface of a heat pipe, the device absorbs the heat emitted by a source through evaporation (changing the liquid to vapor). The vapor produced travels along the heat pipe to the cold interface and condenses back into a liquid, releasing the latent heat. The liquid then returns to the hot interface through gravity or capillary action. Heat pipes have much higher thermal conductivity than common metals such as copper or aluminum.

Heat Pump

A low-energy pump that moves heat from a heat source at a lower temperature to a heat sink at a higher temperature. It acts as a heating system when its purpose is to warm the heat sink or a cooling system when the objective is to cool the heat source. There are many different types of heat pump.

Heat Transfer Fluid

A heat transfer fluid is used to transfer heat from point A to point B. It is used in solar thermal collectors, thermal power plants, cooling systems in car engines, refrigerators, air-conditioning modules, etc.

Heavy Fuel Oil

Heavy fuel oil is high-viscosity liquid fuel, used in big diesel ship engines or as a thermal power plant fuel. It is produced from the heavy cuts obtained during atmospheric distillation, which is the first processing crude oil undergoes when it enters a refinery.

Home Automation

Refers to all the automation and programming processes used in homes. It covers four areas: energy savings (temperature control, running appliances during off-peak hours, etc.), convenience (rolling shutters, garage doors, starting coffee makers at set times, etc.), security (alarms, cameras, remote surveillance, etc.) and health (remote monitoring, remote medical consultation, etc.).

Horizontal Drilling

A type of directional drilling across a formation, at a 90-degree angle. It is significantly more expensive than vertical drilling, but is used when this would be ineffective: thin reservoir layers, thin oil column, highly viscous oil or unconventional deposits such as shale gas.

Hubbert Peak Theory (Peak Oil)

Theory developed by Dr. M. King Hubbert in the 1940s that says that for any given geographical area, from an individual region or country to the planet as a whole, the rate of natural resource (especially oil) production tends to follow a bell-shaped curve over time. According to Hubbert and today’s complex models, production starts at zero and grows, rises to a peak that can never be surpassed, and then declines to depletion.

Humic acid

A complex mixture of molecules produced by the decay of dead plant matter. It is a major component of humus, the organic portion of soil.


A hydrate is a compound formed by the addition of water to another molecule. Hydrates have a crystalline structure, which means that they are solid. In its operations, the oil industry comes across gas hydrates, also known as clathrate hydrates. One of the most frequent is methane hydrate (CH4, nH20), the formation of which must be avoided during production operations at all costs as it can block the flow of hydrocarbons and cause very serious accidents. Huge amounts of natural methane hydrate are trapped in the upper layers of certain oceanic sediment, forming a natural carbon sink that is notable for its instability.

Hydraulic Fracturing

Method of enhancing the productivity of oil or gas reservoirs with low permeability. It involves injecting pressurized water into the reservoir layer, creating a network of cracks in order to improve extraction. Chemicals can be added to the water, such as hydrochloric acid to dissolve carbonates, hydrofluoric acid to dissolve silica, and sand or glass beads to hold the newly created cracks open.


Organic compound consisting of carbon and hydrogen. Hydrocarbons are the principal constituents of crude oil, natural gas and petroleum products.


Refining process that converts heavy hydrocarbons into lighter, low-sulfur products in the presence of hydrogen.

Hydrodesulfurization (Sulfur Recovery)

A refining process to sharply reduce the sulfur content of fuels such as jet and diesel. Removing the sulfur from fuels is a major public health goal, because its combustion releases sulfur dioxide (SO2) that irritates the respiratory tract and causes acid rain harmful to plants. Hydrodesulfurization recovers the sulfur by causing the hydrocarbons to react with hydrogen and produce hydrogen sulfide (H2S) at high temperature and pressure (> 350°C and 34 bar), in the presence of nickel-cobalt or nickel-molybdenum catalysts.


The simplest and lightest atom, the most abundant element in the universe.


Chemical process that splits a molecule by the addition of water.


Marine equivalent of a geophone (device that converts acoustic waves into electrical signals). Hydrophones are combined to form streamers that are towed by seismic vessels to record these signals.