Systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more

ASHRAE - American Society of Heating, Refrigerating and Air-Conditioning Engineers

ASHRAE Standards

Air - Altitude, Density and Specific Volume

The density and the specific volume of air varies with the elevation above sea level

Air Change Rate

How to calculate air change rates - air change rate equations in imperial and SI units

Air Change Rates for typical Rooms and Buildings

Fresh air requirements - recommended air change rates - ACH - for some typical rooms and buildings - auditoriums, kitchens, churches and more

Air Curtains and Air Screens

Air curtains or air screens in open doorways are used to keep acceptable indoor comfort in buildings

Air Duct Velocity Diagram

Air flow volume, duct size, velocity and dynamic pressure

Air Ducts Friction Loss Diagram

Major loss diagram air ducts - SI units

Air Ducts Friction Loss Diagram

Major loss diagram air ducts - Imperial units ranging 10 - 100 000 cfm

Air Ducts Friction Loss Diagram

Major loss diagram air ducts - Imperial units ranging 10 000 - 400 000 cfm

Air Ducts Minor Loss Coefficient Diagrams

Minor loss coefficient diagrams for air ductwork, bends, expansions, inlets and outletsĀ  - SI units

Air Flow and Velocities due to Natural Draft

Air flow - volume and velocity - due to stack or flue effect caused by indoor hot and outdoor cold temperature difference

Air Heating Systems

Using air to heat buildings - temperature rise diagram

Air Intakes and Outlets

Ventilation systems - air intakes and outlets and rules of thumbs

Air Required to Remove Moisture

Required air flow to remove moisture from a room

Air Return Intakes - Sizes and Capacities

Sizes and capacities of air return intakes

Air Velocities in Ducts

Recommended maximum air velocities in ventilation ducts

Air-Duct Sizing

Air flow and required duct area

Area per Person

Common area per person in buildings - values can in general be used calculating indoor climate loads

Belt driven Fans - Motor and Fan Speed

Speed of Fan versus Speed of Motor with Belt Drives

Belts - Length and Speed of Belt

Length and speed of belt, belt gearing

Carbon Dioxide Concentration in Rooms

The carbon dioxide concentration in rooms can be used to indicate air quality and ventilation system efficiency

Carbon Monoxide - Health Effects

Exposure health effects of Carbon Monoxide - CO

Circular Duct Sizes

Dimensions of circular ventilation air ducts

Classification of Ventilation Dampers

Dampers in ventilation systems may be classified according function, construction or leakage class

Classification of Ventilation Systems

Ventilation systems can be classified by functions, distribution strategies or by ventilation principles

Clean Rooms - Federal Standard 209

Clean rooms are maintained virtually free of contaminants such as dust or bacteria

Clean Rooms - ISO Standard 14644

Clean room class limits according ISO Standard 14644-1

Colebrook Equation

Calculate friction loss coefficients in pipes, tubes and ducts

Converting Round Duct Diameter to Area

Converting round duct areas to square feet and square meters

Design of Ventilation Systems

A design procedure of ventilation systems, with air flow rates, heat and cooling loads, air shifts according occupants, air supply principles

Duct Velocity

Calculate velocities in circular and rectangular ducts - imperial and SI-units - online calculator

Ductwork Sheet Metal Gauges

Sheet metal gauges used in ductwork

Equal Friction Method

The equal friction method of sizing ducts is easy and straightforward to use

Equation of Mechanical Energy

The equation of mechanical energy in terms of Energy per Unit Mass, Energy per Unit Volume and Energy per Unit Weight involving head

Equivalent Diameter

Convert rectangular and oval duct geometry to a equivalent circular diameter - online calculator with imperial and SI-units

Evacuation of Air - minimum Capture Velocities to avoid Pollution products transferred to the Room

Capture velocity to avoid pollution products from galvanic baths, spray painting boxes and more contaminating the surrounding room and environment

Exhaust Hoods

Sizing exhaust hoods - air volume flow and capture velocities - online exhaust hood calculator

Exhaust Outlets - Capture Air Velocities

Capture air velocities in front of exhaust outlets - online exhaust outlet velocity calculator

Fan Affinity Laws

Affinity laws can be used to calculate volume capacity, head or power consumption - when speed or rpm, and wheel diameters are changed

Fan Capacity Diagrams

Pressure or head - air flow volume - fan capacity diagrams

Fan Class Limits - AMCA

Fan construction classes established by AMCA

Fan Inlet - Suction Pressure and Air Density

High suction pressure at the fan inlet decreases the density of air - should be corrected for proper fan selection

Fan Motors - Starting Torques

A fan motor must be capable not only of driving the fan at operating speed, but also be capable of accelerating the fan wheel to operating speed

Fan Troubleshooting

Guide to troubleshooting fan problems

Fans - Air and Brake Horsepower

AHP - Air Horse Power, and BHP - Brake Horse Power

Fans - Efficiency and Power Consumption

Power consumption and typical efficiencies of fans

Fans - Influence of Air Temperature and Air Density on Volume Flow, Pressure Head and Power Consumption

The temperature and density of air will influence on volume flow, pressure head and power consumption of fans compared with manufacturing data

Fans and Capacity Control

Modulating fans and their capacities

Filter Arrestance and Efficiency

Air filter efficiency and arrestance

Free Area Ventilation

Ventilation required for attic areas

Friction Loss - Temperature and Pressure

Friction loss in air ducts depends on actual temperature and air pressure

Friction Loss in Ducts

Friction loss or major loss in ducts - equations and online calculator for rectangular and circular ducts - imperial units

Garage Ventilation

Exhaust ventilation from garages and workshops

Gas Vent Termination - Clearance Tolerance

Clearance tolerance per roof slope for gas vent terminations - vent caps

HVAC Damper

Pressure Loss

HVAC Diagram - Online Drawing

Draw HVAC diagrams - Online with the Google Drive drawing tool

Heat Recovery Efficiency

Classification of heat recovery efficiencies - temperature efficiency, moisture efficiency and enthalpy efficiency - online heat exchanger efficiency calculator


Ventilation and heat-recovery calculations, sensible and latent heat - online calculators - imperial units

Heater and Coolers in Ventilation Systems

Basic equations of heat transfer and selecting criteria of heaters and coolers


Classification of Humidifiers - sprayed coils, spinning discs and steam humidifiers

Hydraulic Diameter

Hydraulic diameter of ducts and tubes

Hydraulic Diameter of Rectangular Ducts

Rectangular ducts and hydraulic diameter

Indoor Design Conditions - Industrial Products and Production Processes

Recommended indoor temperature and humidity for some common industrial products and production processes

Indoor Design Temperatures

Recommended indoor temperatures summer and winter

Industrial Environments - Selecting Ventilation Systems

A quick selection guide for ventilation systems and principles in industrial environments

Major loss in Ducts, Tubes and Pipes

Major loss - head loss or pressure loss - due to friction in ducts, pipes and tubes

Minimum Outdoor Makeup Air

ASHRAE Standard 62-2004 Ventilation for Acceptable Indoor Air Quality

Minor Loss Coefficients for Air Duct Components

Minor loss - pressure or head loss - coefficients for air duct distribution systems components

Minor Loss Resistance in Ventilation Ducts

Air velocity, minor loss coefficient and minor loss in ventilation ductworks

Odor Intensity from Persons

Room volume, ventilation and odor intensity from persons

Odor from Persons - Required Ventilation

Odor and smell - required air ventilation

Online Air Duct Calculator

Online calculator to compute the friction loss in air ducts

Pollution Concentration in Rooms

Concentration of a pollution in a limited space as a room depends on the amount of polluted material spread in the room, the supply of fresh air, the outlets position and construction, the principles used for supply and outlet from the space, the fluid flow in the space ..

Pressure Drop in Ventilation Components

Pressure drops in some common ventilation system components like dampers, filters, heaters, coolers

Pumps, Compressors, Blowers and Fans

Comparing pumps, compressors, blowers and fans

Recommended Air Velocities in Ducts

Ducts and recommended air velocities

Recommended Relative Humidity in Production and Process Environments

Recommended Relative Humidity - RH - in production and process environments like libraries, breweries, storages and more

Rectangular Air Ducts Velocity Diagram

Velocity diagram rectangular air ducts

Rectangular Duct Sizes

Dimensions of common rectangular air ducts used in ventilation systems

Rectangular and Circular HVAC Ducts - Equivalent Diameter

Equivalent diameters for rectangular and circular ducts - air flows between 100 - 50,000 cfm

Rooms and Rates of Outdoor Make Up Air

Recommended rates of outdoor make up air in some common types of rooms - banks, assembly halls, hotels and many more

Roughness & Surface Coefficients of Ventilation Ducts

Surface coefficients to calculate friction and major pressure loss in ventilation ducts - concrete, galvanized steel, corroded steel and more

STP - Standard Temperature and Pressure & NTP - Normal Temperature and Pressure

The definition of STP - Standard Temperature and Pressure and NTP - Normal Temperature and Pressure

Scrubber Basics

In a wet scrubber process air is drawn through a mist of water made by spray nozzles, then through separators where water droplets with dust and particles are removed

Selecting Ventilation System in Comfort Environments

A quick selection guide of ventilation system in comfort environments

Sizing Circular Ducts

A rough guide to maximum air volume capacity of circular ducts in comfort, industrial and high speed ventilation systems

Sizing Ducts

The ductwork of ventilation systems are often sized with either the Velocity, the Constant Pressure Loss (or Equal Friction Loss) - or the Static Pressure Recovery Methods

Space required for Ventilation and Air Conditioning Equipment

Required size of ventilation and air conditioning rooms according DIN 1946

Spiral Pipe

Standard dimensions spiral ducts - imperial units

Stack or Flue Effect

Stack or flue effect produced when outdoor temperature is lower than indoor temperature

Supporting Ductwork

Ductwork support and recommended spacing between hangers

Types of Fans

Axial and propeller fans, centrifugal (radial) fans, mixed flow fans and cross flow fans

Types of Fans and Range of Capacities

Centrifugal, Axial, Propeller fans and range of capacities

U-Tube Manometer

The inclined and vertical u-tube manometers are inexpensive and common in differential pressure measurements of flow meters like pitot tubes, orifices and nozzles

Velocities in Ventilation Ducts

Recommended velocities in ventilation ducts

Ventilation Efficiency

The efficiency of a ventilation system may be related to temperature or pollution concentrations

Ventilation Filters

Classification of air filters used in ventilation systems

Ventilation Principles

Some commonly used ventilation principles - the short cut, mixed air, displacement and piston principle

Weights of Round Spiral Elbows

Ductwork - weight of galvanized round spiral elbows

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