Information and Definitions 
Used Equation


Dimensional Analysis


Atmospheric Pressure

Atmospheric pressure is the force exerted by the weight of the Earth's atmosphere on a surface. It is measured as the weight of the air column above a given area, typically in pascals (Pa) or atmospheres (atm). At sea level, the standard atmospheric pressure is approximately 101.3 kPa. This pressure decreases with altitude as the air becomes less dense. Atmospheric pressure influences weather patterns and is crucial in various engineering applications, such as designing structures to withstand pressure differences and in fluid mechanics, where it affects the behavior of gases and liquids in open and closed systems.

Beta Ratio

Beta Ratio is the ratio between the line inner diameter to bore size of the orifice. The flow coefficient is found to be stable between beta ratio of 0.2 to 0.7 below which the uncertainty in flow measurement increases. An orifice plate beta ratio of 0.6 means that the orifice plate bore diameter is 60% of the pipe internal diameter.

Critical Pressure Ratio

The critical pressure ratio is the ratio of downstream pressure to upstream pressure at which the flow in a nozzle or pipe becomes choked, meaning the flow reaches the speed of sound and cannot increase despite further decreases in downstream pressure. For a given gas, it occurs when the flow velocity reaches Mach 1 at the narrowest point (throat) of the nozzle. Beyond this point, further reduction in downstream pressure does not increase mass flow rate. It is mathematically expressed as a function of specific heat ratios and is crucial in designing turbines, compressors, and nozzles.

Density

Density is the relation of mass and volume.The density of a material varies with temperature and pressure. This variation is typically small for solids and liquids but much greater for gases. Density, for engineers, is defined as the mass of a material per unit volume, commonly expressed as kilograms per cubic meter (kg/m3) or grams per cubic centimeter (g/cm3). It measures how compact or heavy a substance is for a given volume. Mathematically, density (?) is calculated using the formula ? = mass/volume. Engineers use this property to evaluate material behavior under various conditions, influencing design decisions in areas like fluid dynamics, structural engineering, and material selection. It is crucial in applications like buoyancy, stability, and strength where weight and material distribution directly impact performance.

Discharge Coefficient

The discharge coefficient is a dimensionless number used to characterise the flow and pressure loss behaviour of nozzles and orifices in fluid systems.It depends on the orifice shape. The discharge coefficient can be obtained for any differentialpressure meter and any installation by calibrating it in a flowing fluid: for a particular orifice meter the discharge coefficient is a function of the Reynolds number. Over many years of experiment it has been found that the discharge coefficient can be predicted within a defined uncertainty provided that the orifice meter (i.e. the orifice plate and pipework) are constructed within the standards. If the discharge coefficient is to be used for an orifice meter without calibrating it in a flowing fluid, the discharge coefficient is usually taken from a published discharge coefficient equation. Therefore, the discharge coefficient equation is very important for orifice plates: an error of 0.1 % in discharge coefficient gives an error of 0.1 % in many flow measurements of natural gas. ISO 51671:2003 provides an equation for the orifice discharge coefficient calculation, Cd, as a function of Beta Ratio, Reynolds number, L1 and L2, where L1 is the distance of the upstream pressure tap from the orifice plate and L2 is the distance of the downstream pressure tap from the orifice plate.

Dynamic Viscosity

Viscosity is the measure of a fluid's resistance to flow. Dynamic viscosity is a measure of internal resistance.It measures the tangential force per unit area required to move one horizontal plane with respect to an other plane. It is commonly expressed, particularly in ASTM standards, as centipoise (cP) since the latter is equal to the SI multiple millipascal seconds (mPa s).The viscosity of a fluid is highly temperature dependent.

Expansion Factor

The expansion factor in orifice flow refers to the ratio of the actual flow area of the orifice to the area of a hypothetical ideal orifice that would produce the same mass flow rate under identical conditions. It accounts for the effects of compressibility and real gas behavior, which can cause deviations from ideal flow predictions. The expansion factor is crucial in engineering calculations for designing and analyzing orifice plates, as it adjusts for changes in flow characteristics due to pressure and temperature variations, ensuring accurate measurement and control in fluid systems.

Flow

Mass of a substance which passes per unit of time. Mass flow in Kg/s units, flowing through the pipe. Flow, in engineering, refers to the streamlined and efficient movement of resources, energy, or materials through a system or process. It involves optimizing the sequence and management of tasks to reduce waste, minimize delays, and ensure continuous progress. In fluid dynamics, flow describes the behavior of liquids or gases in motion, governed by factors such as pressure, velocity, and viscosity. Engineers study flow to enhance system performance, improve product design, and increase operational efficiency. By understanding flow, engineers can design more effective processes in industries like manufacturing, construction, and transportation, while ensuring safety and sustainability.

Fluid

Fluid Name or Composition. Fluid is called a type of continuous medium formed by some substance whose molecules have only a weak force of attraction. A fluid is a set of particles that are held together by weak cohesive forces and the walls of a container; The term encompasses liquids and gases.

Leakage Time

Leakage Time in engineering refers to the duration it takes for a system, such as a pressure vessel, pipeline, or sealed compartment, to lose a certain amount of pressure or fluid due to leaks. This parameter is crucial for assessing the integrity and performance of systems that must maintain specific pressure or containment levels. Leakage Time is typically measured under controlled conditions and helps identify the rate at which a system loses air, gas, or liquid. Accurate assessment is critical in applications like hydraulic systems, fuel tanks, and HVAC systems, where maintaining tight seals is essential for safety and efficiency.

Mass Flow

Mass flow, in engineering, refers to the movement of mass through a given system or boundary over time. It quantifies the rate at which mass is transferred, often expressed in kilograms per second (kg/s). This concept is crucial in systems involving fluid dynamics, such as in pipelines, engines, or heat exchangers. Mass flow is calculated as the product of fluid density, velocity, and crosssectional area through which the fluid moves. Understanding mass flow is vital for optimizing processes like energy transfer, fluid transport, and thermodynamic efficiency in industrial, mechanical, and aerospace applications.

Match Flow Regime

Match Flow Regime types in engineering refer to the categorization of fluid flow patterns within a system based on how they interact with various components, like pipes or channels. These regimes include laminar flow, where fluid moves in smooth, orderly layers; turbulent flow, characterized by chaotic, irregular motion; and transitional flow, which fluctuates between laminar and turbulent states. Each regime impacts pressure drop, heat transfer, and overall system efficiency differently. Understanding these regimes is crucial for designing and optimizing systems like pipelines, heat exchangers, and reactors to ensure effective and efficient operation.

Match Number

In engineering, the Flow Match Number (FMN) is a dimensionless parameter used to characterize the degree of similarity between two or more fluid flow patterns in a system. It quantifies how well the flow characteristics, such as velocity profiles and turbulence levels, match between different components or conditions. The FMN helps engineers assess the effectiveness of flow distribution, optimize system design, and ensure uniform performance across various parts of the system. By comparing FMNs, engineers can identify inconsistencies and make adjustments to improve the overall efficiency and reliability of fluid handling systems.

Molecular Weight

Molecular weight, also called molecular mass, is the total mass of a molecule, calculated as the sum of the atomic masses of all atoms in the molecule. It is expressed in atomic mass units (amu) or grams per mole (g/mol). For engineers, molecular weight is crucial in chemical process calculations, such as determining the stoichiometric proportions in reactions, material properties, and designing chemical processes. It helps estimate the quantity of reactants or products and influences the behavior of materials, such as viscosity, diffusion, and reaction rates in processes involving gases, liquids, or polymers.

Orifice Diameter

Orifice diameter refers to the internal diameter of an opening or passage through which fluids or gases flow in engineering systems. It is a critical parameter in devices like orifice plates, nozzles, or valves, where it controls the flow rate, pressure drop, and velocity of the medium passing through. The size of the orifice diameter directly affects the discharge coefficient and flow characteristics. Engineers use precise calculations based on the orifice diameter to design systems for optimal fluid dynamics in applications such as pipelines, HVAC systems, and fluid control mechanisms. Accurate measurement is crucial for ensuring efficiency and system performance.

Pipe Diameter

Inside diameter of the pipe. All process calculations are based on the volume of the pipe which is the function of internal diameter of the pipe. As per standards, any pipe is specified by two nondimensional numbers Nominal Diameter (in Inches as per American Standards or mm as per European standards) and Schedule (40, 80, 160,...). The outer diameter of the pipe is the diameter of outer surface of the pipe.

Plant, Area and Notes

Information Referred to the physical installation of the instrument. Plant and Process Area where the instrument is installed. Notes about the instrument.

Pressure Drop

Pressure drop refers to the reduction in pressure as a fluid (liquid or gas) flows through a pipe, valve, fitting, or other flowrestricting component in a system. It occurs due to friction between the fluid and the walls of the conduit, as well as turbulence, bends, or changes in flow area. Factors influencing pressure drop include fluid velocity, viscosity, pipe roughness, and length. In engineering, controlling pressure drop is important for system efficiency and performance, as excessive pressure loss can lead to higher energy consumption, reduced flow rates, and potential equipment failure.

Pressure In

Considering the direction of the fluid, we define P1 as the pressure (gauge or absolut) existing in the pipeline before the restriction orifice. Pressure has two effects on volume. The higher pressure makes the gas denser so less volume flows through the meter. However, when the volume is expanded to base pressure, the volume is increased.

Pressure Ratio

Flow Pressure Ratio (FPR) is a dimensionless parameter used in engineering to describe the relationship between the pressure of a fluid entering a system and the pressure of the fluid exiting the system. It is defined as the ratio of the inlet pressure (P_in) to the outlet pressure (P_out). FPR is critical in assessing the efficiency and performance of various systems, such as pumps, turbines, and compressors. A higher FPR indicates a greater pressure drop through the system, which can affect the system's operational stability and efficiency. Understanding FPR helps engineers optimize system design and performance.Pressure Ratio at which the discarge coefficient determined has the value C.

Ratio of Sp.Heats

Ratio of the heat capacity at constant pressure (CP) to heat capacity at constant volume (CV). It is sometimes also known as the isentropic expansion factor and is denoted by ? (gamma) for an ideal gas or ? (kappa), the isentropic exponent for a real gas.

Reynolds (ReD) and Reynolds Flow Regime

The Reynolds number (Re) is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations. At low Reynolds numbers, flows tend to be dominated by laminar (sheetlike) flow, while at high Reynolds numbers turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow.

State of Matter

In engineering, a state of matter refers to the distinct forms that different phases of matter take on, characterized by varying properties such as density, shape, and volume. The primary states are solid, liquid, and gas, each defined by the arrangement and energy of particles. Solids have fixed shapes and volumes due to tightly packed particles, liquids have fixed volumes but take the shape of their containers due to loosely packed particles, and gases expand to fill their containers as particles move freely and are widely spaced. Additionally, plasma is another state observed at extremely high temperatures where ionized particles prevail.

Tagname

Tagname of the instrument. This is the identifier of the field device, which is normally given to the location and function of the instrument.

Temperature

Operating Temperature of the fluid in Celsius units. The flowing temperature is normally measured downstream from the orifice and must represent the average temperature of the flowing stream in degrees Celsius. Temperature has two effects on volume. A higher temperature means a less dense gas and higher flows, but when this higher flow is corrected to base temperature, the base flow is less.

Velocity in pipe

Velocity in a pipe refers to the speed at which a fluid (liquid or gas) flows through the pipe. It is determined by the flow rate (volume of fluid passing per unit time) and the pipe's crosssectional area. The relationship is governed by the equation V=Q/A , where V is velocity, Q is flow rate, and A is the pipe's crosssectional area. Velocity affects factors such as pressure drop, turbulence, and energy losses. High velocity can cause erosion and noise, while low velocity may lead to sedimentation or inefficient flow.

Volumetric Flow

Volumetric flow refers to the volume of fluid passing through a given crosssectional area per unit time. It is commonly measured in cubic meters per second (m3/s) or liters per minute (L/min) and is crucial in fluid dynamics, piping systems, and various engineering applications. The volumetric flow rate (Q) can be calculated using the equation Q = A v, where A is the crosssectional area of the flow, and v is the velocity of the fluid. This parameter is important in determining the efficiency of fluid transport systems, like pumps and pipelines.
