MechanicalIntermediate
Fan Affinity Laws
Estimate how fan airflow, pressure, and shaft power change with rotational speed when fan geometry and air density remain similar.
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HVAC, air systems, hydronic systems, pumps, fans, heat transfer, controls, testing, and commissioning calculations.
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84 reviewed tools are available in this collection.
MechanicalIntermediate
Pump Affinity Laws
Estimate pump flow, head, and shaft power at a different rotational speed for the same impeller and a similar system.
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Airflow, Velocity & Area
Calculate required duct cross-sectional area and an equivalent round diameter from airflow and average velocity.
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Equivalent Round Duct
Estimate the round duct diameter with approximately the same friction rate as a rectangular duct at equal airflow.
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Pipe Flow & Velocity
Calculate average liquid velocity from volumetric flow and actual pipe inside diameter.
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Hydronic Pressure Loss
Estimate straight-pipe and minor pressure losses with Darcy–Weisbach using actual fluid properties and a summed fitting-loss coefficient.
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Airside Sensible Heat
Estimate sensible airside capacity from airflow, dry-bulb temperature difference, air density, and specific heat.
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Water-Side Heat Transfer
Estimate hydronic heat transfer from fluid flow, temperature difference, and a user-entered fluid factor.
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Fan Air Horsepower
Calculate useful air power from fan airflow and fan pressure.
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Fan Brake Horsepower
Estimate required fan shaft power from airflow, fan pressure, and entered fan efficiency.
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Fan Efficiency
Calculate fan efficiency by dividing useful air power by measured shaft power.
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Belt-Drive Fan RPM
Estimate driven fan speed from motor speed, sheave pitch diameters, and entered belt slip.
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Fan Density Correction
Correct fan pressure and shaft power between actual and reference air densities at the same flow and speed.
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Fan System Curve
Project a quadratic fan-system pressure at a target airflow from one known operating point.
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Fan Wheel-Diameter Change
Estimate flow, pressure, and power changes for geometrically similar fans at the same rotational speed.
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Fan Static Pressure
Calculate fan static pressure from fan total pressure and outlet velocity pressure.
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Fan Total Pressure
Calculate fan total-pressure rise from inlet and outlet static and velocity pressures.
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Fan Turndown
Calculate fan flow turndown, minimum-flow percentage, speed ratio, and ideal affinity-law power fraction.
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Pump Total Dynamic Head
Calculate pump total dynamic head from pressure, elevation, and velocity-head differences between suction and discharge measurement planes.
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Pump Water Horsepower
Calculate hydraulic power imparted to a liquid from flow, head, and specific gravity.
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Pump Efficiency
Calculate pump efficiency by dividing hydraulic output power by measured shaft input power.
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Pump System Curve
Project total system head at a target flow using an entered static head and one known operating point.
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NPSH Available
Estimate source-boundary net positive suction head available from absolute liquid-surface pressure, vapor pressure, static suction head, and suction-line losses.
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Hydronic Fill Pressure
Calculate minimum cold fill pressure from elevation, fluid specific gravity, and required pressure at the system high point.
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Building Static Pressure
Calculate liquid static pressure produced by a vertical fluid column.
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Valve Authority
Calculate control-valve authority from valve pressure drop and the pressure drop of the remaining controlled circuit.
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Pump Power and Energy
Estimate pump electrical input power, operating energy, and energy-consumption cost from flow, head, efficiencies, and runtime.
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Differential-Pressure Flow Estimate
Estimate flow through a fixed differential-pressure device from a known reference flow and pressure drop.
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Round Duct Sizing
Calculate a preliminary round duct diameter from airflow and target average velocity.
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Rectangular Duct Sizing
Calculate preliminary rectangular duct dimensions from airflow, target velocity, and width-to-height aspect ratio.
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Equal-Friction Duct
Estimate round duct diameter from airflow and target friction rate using a standard-air empirical relationship.
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Duct Pressure Loss
Calculate straight-duct pressure loss with Darcy–Weisbach from hydraulic diameter, length, velocity, air density, and friction factor.
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Duct Fitting Loss
Calculate fitting pressure loss from an entered loss coefficient and local velocity pressure.
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Total External Static Pressure
Sum entered external air-system component pressure losses on a consistent static-pressure basis.
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Pitot-Tube Airflow
Calculate air velocity and airflow from average velocity pressure, air density, and clear duct area.
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Air Changes per Hour
Calculate air changes per hour from volumetric airflow and room volume.
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Duct Leakage Percentage
Calculate measured duct leakage as a percentage of an entered reference airflow.
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Duct Traverse Averaging
Average eight entered velocity readings and calculate airflow from clear duct area.
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Darcy–Weisbach Pipe Loss
Calculate liquid velocity, Reynolds number, Darcy friction factor, and straight-pipe pressure loss from actual fluid and pipe properties.
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Hazen–Williams Pipe Loss
Calculate water-pipe friction head and pressure loss using the Hazen–Williams empirical relationship.
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Pipe and Fitting Equivalent Length
Sum straight pipe and entered fitting equivalent lengths for preliminary pressure-loss calculations.
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Total Hydronic Pressure Loss
Sum entered pipe, fitting, valve, coil, strainer, heat-exchanger, and other hydronic pressure losses.
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Control-Valve Cv
Calculate required liquid valve flow coefficient Cv from flow, pressure drop, and specific gravity.
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Glycol Correction
Estimate required glycol-solution flow for the same heat duty and temperature difference from entered fluid density and specific heat.
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Hydronic System Volume
Estimate total hydronic volume from one representative pipe segment plus entered equipment and miscellaneous volume.
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Expansion-Tank Preliminary Sizing
Estimate diaphragm-tank volume from system volume, entered fluid expansion, and initial and maximum absolute pressure relationships.
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Pipe Insulation Surface Temperature
Estimate insulated-pipe outer-surface temperature and heat transfer per unit length with cylindrical conduction and outside convection.
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Pipe Condensation Risk
Compare pipe or insulation surface temperature with ambient dew point and an entered safety margin.
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Airside Total Heat
Calculate total airside heat transfer from airflow, air density, and moist-air enthalpy difference.
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Chilled-Water Tonnage
Calculate chilled-water load from flow, temperature difference, and a user-entered fluid factor.
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Heating-Water Capacity
Calculate heating-water capacity from flow, temperature difference, and an entered fluid factor.
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Required Airflow
Calculate airflow required for a sensible load using temperature difference and a user-entered air constant.
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Required Water Flow
Calculate required hydronic flow from load, temperature difference, and an entered fluid factor.
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Chiller Capacity
Calculate evaporator capacity from liquid flow, density, specific heat, and entering/leaving temperature.
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Boiler Efficiency
Calculate direct thermal efficiency from useful heat output and fuel input on a consistent basis.
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Heat-Recovery Effectiveness
Calculate supply-side sensible heat-recovery effectiveness from three dry-bulb temperatures.
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Psychrometric Properties
Calculate humidity ratio, moist-air enthalpy, dew point, and vapor pressure from dry-bulb temperature, relative humidity, and pressure.
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Mixed-Air Conditions
Calculate mixed-air dry-bulb temperature, humidity ratio, and enthalpy from outdoor and return moist-air states.
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Outdoor-Air Percentage by Temperature
Estimate outdoor-air percentage from outdoor, return, and mixed dry-bulb temperatures.
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Dew Point
Estimate air dew-point temperature from dry-bulb temperature and relative humidity.
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Surface Condensation Risk
Calculate the surface-temperature margin above air dew point from dry-bulb temperature and relative humidity.
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Humidification Load
Calculate required moisture addition from airflow, dry-air density, and humidity-ratio increase.
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Condensate Generation
Calculate airside condensate generation from dry-air mass flow and humidity-ratio decrease.
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Economizer Evaluation
Evaluate outdoor-air dry-bulb and enthalpy against return air and user-entered economizer limits.
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Cooling-Coil Sensible Heat Ratio
Calculate sensible heat ratio from sensible and total cooling capacity.
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Coil Approach Temperature
Calculate leaving-air approach above entering-fluid temperature for a cooling coil.
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Heat-Exchanger Effectiveness
Calculate heat-exchanger effectiveness from hot- and cold-side inlet/outlet temperatures and capacity rates.
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Coefficient of Performance
Calculate equipment COP from useful thermal capacity and electrical input power.
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AHU Performance
Calculate measured air-handler total-capacity magnitude, heat-transfer direction, and percent of entered design capacity from airflow and moist-air enthalpy difference.
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VAV Box Performance
Compare measured VAV airflow with design, minimum, and maximum airflow references.
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Chiller kW per Ton
Calculate chiller kW per refrigeration ton and COP from capacity and electrical input.
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Cooling-Tower Approach and Range
Calculate tower approach, range, and temperature effectiveness from hot water, cold water, and entering wet-bulb temperature.
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Boiler Turndown
Calculate boiler input turndown ratio from maximum and minimum stable firing rates.
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Filter Pressure-Drop Trend
Calculate the fraction of a filter pressure-drop allowance consumed between clean and final limits.
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Control-Valve Flow Verification
Compare measured liquid flow with a square-root flow prediction from reference and measured pressure drop.
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Damper Position–Airflow Comparison
Compare measured airflow percentage with commanded damper position as a diagnostic screen.
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Sensor Offset and Span
Calculate low-point offset, high-point offset, and span error from two reference and two sensor readings.
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PID Response Metrics
Calculate percent overshoot, peak time, settling time, and final error for a documented control response.
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Actuator Stroke Time
Normalize a measured partial actuator movement to an equivalent full-stroke time and compare it with rated time.
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Runtime and Cycling
Calculate runtime percentage, cycles per hour, and average on-time from an observation interval.
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Fan Energy Use
Calculate fan electrical energy from input power, runtime, and average load factor.
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Pump Energy Use
Calculate pump electrical energy from input power, runtime, and average load factor.
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Chiller Energy Use
Calculate chiller electrical energy from cooling capacity, kW/ton, runtime, and load factor.
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Boiler Fuel Use
Calculate boiler fuel-energy use from useful output rate, efficiency, and runtime.
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Explore the resource roadmap- Fans and air systems
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