# Welcome to Neutrium

Neutrium is a knowledge base of engineering topics, centred mainly around chemical engineering design challenges faced by engineers in their daily work. We created Neutrium to bridge the gap between theory and practice. Feel free to ask a question, leave feedback or take a look at one of our in-depth articles.

This article details the most common methods to quantify the concentration of a component in a mixture, and details how to convert between these concentrations. Concentration is commonly expressed in moles per volume, mass per volume, mass percentage, volume percentage, mole percentage and parts per million. Using density and/or molecular weight properties it is possible to convert between any of the above measures.

Viscosity is a measure of a fluids propensity to flow. There are two kinds of viscosity commonly reported, kinematic and dynamic. Dynamic viscosity is the relationship between the shear stress and the shear rate in a fluid. The Kinematic viscosity is the relationship between viscous and inertial forces in a fluid. Most common fluids are Newtonian fluids and their viscosity is constant with shear stress and shear rate. Non-Newtonian fluids are less common.

Fittings such as elbows, tees, valves and reducers represent a significant component of the pressure loss in most pipe systems. This article discusses the differences between several popular methods for determining the pressure loss through fittings. The methods discussed for fittings are: the equivalent length method, the K method (velocity head method or resistance coefficient method), the two-K method and the three-K method. In this article we also discuss method for calculating pressure loss through pipe size changes as well as control valves.

The pump affinity laws allow the prediction of centrifugal pump performance given changes to the speed of the pump or the diameter of impeller. This article presents the pump affinity laws for reference.

Power is consumed by a pump, fan or compressor in order to move and increase the pressure of a fluid. The power requirement of the pump depends on a number of factors including the pump and motor efficiency, the differential pressure and the fluid density, viscosity and flow rate. This article provides relationships to determine the required pump power.

Heat transfer coefficients characterise the transfer of thermal energy in terms of heat flow and temperature difference between two participating media. This article demonstrates how to calculate the radiative heat transfer coefficient and thermal resistance for gray, diffuse radiative exchange.

The packed bed Reynolds number is dimensionless and describes the ratio of inertial to viscous forces for fluid flow through a packed bed. It may be used to calculate the pressure drop though a packed bed via the Ergun equation or identify the boundaries of flow regimes (laminar, transitional and turbulent) in a packed bed. This article will show you how to calculate and interpret the packed bed Reynolds number.

The ideal gas law is used to relate volume, pressure and temperature for gases. The ideal gas law is an approximation and is generally more accurate at mild temperatures and pressures. The properties of gases increasingly deviate from ideal as conditions become more extreme, i.e. low temperature or high pressure. In these cases a compressibility factor may be used to correct for non-ideal behaviour when using the ideal gas relationship.

The concept of thermal resistance can be utilised to solve steady state heat transfer problems that involve series, parallel or combined series-parallel components. This article demonstrates how to calculate the total thermal resistance for such systems and how to calculate the thermal resistance for practical geometries such as a pipe wall.

The Prandtl number is a dimensionless number named after the German physicist Ludwig Prandtl. It represents the ratio of molecular diffusivity of momentum to the molecular diffusivity of heat.