Chemical Engineering English covers the language of reactors, separations and process plants — distillation, catalysts, mass transfer and process control. This free glossary lists the 60 most frequently used of the 400 Chemical Engineering terms in the Engineering English iOS app — each with IPA pronunciation and a working definition. In the app, every term also includes example sentences, translations in 21 languages, flashcards and AI conversation practice.
P&IDs, safety datasheets and process licensor documentation are written in English across the global process industry. Chemical engineers need this vocabulary to run HAZOP studies, commission units and communicate with international EPC contractors.
Last updated: July 30, 2026 · How terms are selected and ranked · 🇹🇷 Türkçesi
Quick answer: The 10 most frequently used Chemical Engineering terms in English are Chemical Reaction, Reactor, Reynolds Number, Heat Exchanger, Turbulent Flow, Convection, Heat Transfer Coefficient, Continuity Equation, Control Valve, Distributed Control System (DCS). The full Engineering English library contains 400 Chemical Engineering terms with pronunciation, example sentences, translations and flashcards.
A process in which one or more substances are transformed into different substances through the breaking and forming of chemical bonds. It is accompanied by an energy change and a measurable change in composition.
A vessel or piece of equipment designed to contain and control a chemical reaction under specified conditions of temperature, pressure, and mixing. Its geometry and internals determine contact time and heat transfer.
The Reynolds number is a dimensionless quantity that characterizes the flow regime, predicting whether flow will be laminar or turbulent. It is defined as the ratio of inertial forces to viscous forces.
A heat exchanger is a device that transfers heat between two or more fluids without mixing them. It is widely used in process plants for heating, cooling, and energy recovery.
A flow regime characterized by chaotic, random motion, eddies, and high mixing between fluid layers. It typically occurs at high Reynolds numbers and enhances heat and mass transfer.
Heat transfer through the macroscopic movement of a fluid, driven by density differences (natural convection) or external forces (forced convection). It is a dominant mode of heat transport in many process units.
The heat transfer coefficient quantifies the rate of heat transfer per unit area per unit temperature difference. It is used in sizing heat exchangers and predicting thermal performance.
The continuity equation expresses the conservation of mass in fluid flow. For incompressible flow, the product of cross-sectional area and velocity remains constant along a streamline.
A control valve is a final control element in a process control system that modulates fluid flow in response to a signal from a controller. It adjusts the flow rate to maintain a desired process variable such as pressure, temperature, or level.
A Distributed Control System (DCS) is a computerized control system for a process plant that uses distributed controllers for autonomous control while integrating supervisory data. It provides centralized operation with distributed risk and is essential for managing complex chemical processes.
A safety instrumented system is a layer of protection designed to prevent hazardous events by detecting abnormal conditions and taking automated actions. It is composed of sensors, logic solvers, and final control elements to achieve a safety function.
An actuator is a device that converts a control signal into mechanical motion. It is used to move or control a mechanism or system, such as opening a valve or adjusting a damper.
SCADA (Supervisory Control and Data Acquisition) is a system of hardware and software that monitors and controls industrial processes. It gathers real-time data from field devices and provides a centralized human-machine interface.
The final control element is the device that physically manipulates a process variable in response to a signal from a controller. It is typically a control valve, damper, or variable-speed drive that directly affects the flow, pressure, or temperature of the process.
The 4-20 mA current loop is an analog signaling standard where a transmitter outputs a current between 4 and 20 milliamperes proportional to the measured process variable, with 4 mA representing the lower range and 20 mA the upper range.
A temperature transmitter converts the signal from a temperature sensor such as a thermocouple or RTD into a standardized analog output, typically 4-20 mA, for transmission to a distributed control system.
A centrifugal pump uses a rotating impeller to increase the pressure and flow rate of a fluid. It is the most common type of pump used in chemical plants for transferring liquids.
ALARP is an acronym for As Low As Reasonably Practicable, a principle used in risk management to reduce risks to a level that is tolerable and balanced against the cost, time, and effort of further reduction.
Process safety management is a systematic framework for identifying, understanding, and controlling hazards in industrial processes to prevent major accidents involving hazardous materials. It combines engineering design, operating procedures, and management systems to ensure safe operation.
A proportionality factor in the rate law that relates the reaction rate to the concentration of reactants. It depends on temperature and is specific to each reaction.
An empirical equation that describes the temperature dependence of the rate constant, incorporating the activation energy and pre-exponential factor. It is fundamental for predicting reaction rates at varying temperatures.
A detailed step-by-step description of the sequence of elementary reactions that transform reactants into products. It includes the identification of intermediates and the rate-determining step.
A rate law is an equation relating the reaction rate to the concentrations of reactants, often raised to powers determined by the reaction mechanism. It is used to model the kinetics of a chemical reaction.
Relative volatility is a thermodynamic measure of the ease with which two components can be separated by distillation. It is defined as the ratio of the vapor pressures of the two components at a given temperature.
A straight line on a McCabe-Thiele diagram that represents the mass balance relationship between vapor and liquid compositions in a section of a distillation column. It defines the operating conditions for a given reflux ratio.
The liquid product that exits from the bottom of a distillation column, typically containing the least volatile components. It is often the heavier fraction of the feed mixture.
Raoult's law states that the partial vapor pressure of a component in an ideal solution is equal to the product of its mole fraction and its vapor pressure in the pure state. It is used to describe the vapor-liquid equilibrium of ideal mixtures.
Henry's law states that the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid. It is essential for describing gas-liquid equilibrium at low concentrations.
Fugacity is a thermodynamic property that represents the tendency of a substance to escape or leave a phase. It corrects for non-ideality in phase equilibrium calculations.
The activity coefficient accounts for deviations from ideal behavior in liquid mixtures. It is used to modify concentration in thermodynamic equations.
Gibbs free energy is a thermodynamic potential that measures the maximum reversible work that can be performed by a system at constant temperature and pressure. It indicates the spontaneity of a process.
The ideal gas law, PV = nRT, describes the relationship between pressure, volume, temperature, and amount of an ideal gas. It is a fundamental equation for estimating gas behavior under moderate conditions where intermolecular forces are negligible.
A substance that increases the rate of a chemical reaction by providing an alternative pathway with lower activation energy, without being consumed overall. It changes reaction speed but not the equilibrium position.
The speed at which reactants are consumed or products are formed, usually expressed as a change in concentration or moles per unit time and volume. It depends on temperature, concentration, and catalyst activity.
The fraction of a reactant fed to a process that is actually consumed by reaction, usually reported as a percentage. It measures how completely the limiting reactant has been used.
The amount of desired product actually obtained compared with the maximum amount predicted by stoichiometry from the feed supplied. It combines the effects of incomplete conversion and competing side reactions.
The SI base unit for amount of substance, containing a fixed number of elementary entities such as atoms or molecules. It links measurable mass to the counted particles that take part in reactions.
The quantity of a specific substance contained in a given amount of mixture, expressed per unit volume, mass, or mole. It is the driving variable in most rate and transport calculations.
A logarithmic scale that expresses how acidic or alkaline an aqueous solution is, based on hydrogen ion activity. Values below seven indicate acidity and values above seven indicate alkalinity.
A separation technique that exploits differences in volatility between components of a liquid mixture by vaporising the mixture and condensing the vapour. The condensed product is enriched in the more volatile components.
A mechanical separation in which a suspension is forced through a porous medium that retains the solid particles while allowing the fluid to pass. The retained solids form a cake whose growing resistance governs the flow rate.
The net movement of a chemical species from one location or phase to another under the influence of a concentration or chemical potential difference. It sets the rate of nearly every separation and many reaction processes.
The liquid component of a solution that dissolves the other substances present, usually being the constituent in greatest amount. Its selectivity, volatility, and toxicity decide whether it suits a given separation or reaction.
A simplified graphical representation of a chemical plant that shows the major equipment, the main material streams between units, and key operating conditions such as flow rate, temperature, and pressure. It conveys the overall concept of the process without detailing every valve or instrument.
A detailed engineering drawing that shows every pipe, valve, fitting, instrument, and control loop in a process plant, together with line sizes and equipment tags. It is the primary reference for construction, operation, and safety review.
An accounting of all material entering, leaving, accumulating in, and generated or consumed within a defined system boundary, based on the conservation of mass. It is used to determine unknown stream flows and compositions.
An accounting of all energy entering, leaving, and accumulating within a defined system, including heat, work, and the enthalpy carried by material streams. It follows from the first law of thermodynamics and is used to size heaters, coolers, and utility systems.
The discipline of automatically maintaining process variables such as temperature, pressure, level, and flow at desired values by measuring them and adjusting final control elements. It keeps a plant safe, stable, and within product specifications.
The Prandtl number is a dimensionless quantity that relates the momentum diffusivity (kinematic viscosity) to the thermal diffusivity. It indicates the relative thickness of velocity and thermal boundary layers.
Pressure drop is the decrease in fluid pressure as it flows through a pipe, valve, fitting, or equipment due to friction and changes in flow geometry. It is a key parameter for pump sizing and system design.
A measure of the total heat transfer resistance between two fluids separated by a solid wall. It combines conductive and convective resistances into a single value.
A flow regime in which fluid moves in smooth, parallel layers with no disruption between them. It occurs at low Reynolds numbers and is characterized by orderly streamlines.
A material property that measures its ability to conduct heat, defined as the heat flux per unit area per unit temperature gradient. High values indicate efficient heat transfer through the material.
A principle in fluid dynamics stating that for an inviscid, incompressible flow along a streamline, an increase in fluid velocity occurs simultaneously with a decrease in pressure or potential energy. It is derived from energy conservation.
The reduction in total mechanical energy per unit weight of fluid caused by friction and turbulence as the fluid flows through a pipe or conduit.
The rate of heat energy transfer per unit area perpendicular to the direction of heat flow, typically expressed in watts per square meter.
Shear stress is the component of stress coplanar with a material cross section. It arises from forces acting parallel to the surface, such as fluid drag on a pipe wall.
Fouling is the accumulation of unwanted deposits on heat transfer surfaces. It reduces thermal efficiency and increases pressure drop in heat exchangers.
Condensation is the phase change from vapor to liquid when the vapor is cooled below its saturation temperature. It is a key heat transfer mechanism in condensers.
Conduction is the transfer of thermal energy through a solid or stationary fluid by molecular collisions without bulk motion. It is a fundamental mode of heat transfer described by Fourier's law.
The 10 most frequently used Chemical Engineering terms in the Engineering English library are Chemical Reaction, Reactor, Reynolds Number, Heat Exchanger, Turbulent Flow, Convection, Heat Transfer Coefficient, Continuity Equation, Control Valve, Distributed Control System (DCS). This page lists the top 60 of 400 terms, ranked by usage frequency.
400. Each one includes an IPA pronunciation, a plain-English definition, a real example sentence and translations in 21 languages; the 60 most frequent are free to browse on this page.
Every term on this page shows its IPA transcription — for example Chemical Reaction is pronounced /ˈkemɪkəl riˈækʃən/, Reactor is /riˈæktər/ and Reynolds Number is /ˈrɛnəldz ˈnʌmbər/. The Engineering English app also plays audio for each term and checks your pronunciation with speech recognition.
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