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MEASUR-Tools-Suite v1.0.11
The MEASUR Tools Suite is a collection of industrial efficiency calculations written in C++ and with bindings for compilation to WebAssembly.
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This page documents the fundamental physical constants used throughout the MEASUR Tools Suite for heat transfer, thermodynamic, and energy calculations. Constants are provided in both SI (Standard International) and U.S. Customary units to support various engineering applications.
The constants are organized by unit system and include:
All constants are defined with appropriate units and source references where applicable.
The following constants are defined in Standard International (SI) units:
| Constant Name | Symbol | Value | Unit | Description |
|---|---|---|---|---|
| Stefan-Boltzmann constant | \(\sigma\) | \(\qty{5.670374419e-8}{ \watt\per\meter\squared\kelvin\tothe{4}}\) | physics::si::kStefanBoltzmann | Radiation heat transfer constant |
| Standard water density at 4°C | \(\rho_w\) | \(\qty{1000.0}{ \kilogram\per\meter\cubed}\) | physics::si::kWaterDensityBase | Base density for water property calculations |
The following constants are defined in U.S. Customary units:
| Constant Name | Symbol | Value | Unit | Description |
|---|---|---|---|---|
| Stefan-Boltzmann constant | \(\sigma\) | \(\qty{1.713441e-9}{ \btu\per\hour\foot\squared\degreeRankine\tothe{4}}\) | physics::us::kStefanBoltzmann | Radiation heat transfer constant (see [2]) |
| Water boiling point | \(T_{boil}\) | \(\qty{212.0}{ \degreeFahrenheit}\) | physics::us::kWaterBoilingPointF | Standard atmospheric pressure boiling point |
| Specific heat of water vapor | \(C_{p,vapor}\) | \(\qty{0.481}{ \btu\per\pound\degreeFahrenheit}\) | physics::us::kSpecificHeatWaterVapor | Specific heat capacity of water vapor |
| Latent heat of evaporation | \(H_{evap}\) | \(\qty{970.0}{ \btu\per\pound}\) | physics::us::kWaterEvaporation | Heat required for water phase change |
| Standard gas temperature | \(T_{std}\) | \(\qty{520.0}{ \degreeRankine}\) | physics::us::kStandardGasTemperatureR | Reference temperature (60°F + 460) for gas calculations |
| Ambient reference temperature | \(T_{amb}\) | \(\qty{60.0}{ \degreeFahrenheit}\) | physics::us::kAmbientTemperatureF | Standard ambient temperature for calculations |
| Base specific heat of air | \(C_{p,air,base}\) | \(\qty{0.017828518}{ \btu\per\pound\degreeFahrenheit}\) | physics::us::kSpecificHeatAirBase | Base value for exhaust gas calculations |
| Specific heat temperature coefficient | \(C_{p,air,coeff}\) | \(\qty{0.000002556}{ \btu\per\pound\degreeFahrenheit\per\degreeFahrenheit}\) | physics::us::kSpecificHeatAirCoeff | Temperature-dependent coefficient |
| Air correction base | - | \(\qty{-1.078913827}{ \btu\per\pound}\) | physics::us::kAirCorrectionBase | Correction term for exhaust gas calculations |
The following constants are used for converting between different unit systems:
| Constant Name | Symbol | Value | Unit | Description |
|---|---|---|---|---|
| Fahrenheit to Rankine offset | - | \(\qty{459.67}{ \degreeRankine}\) | physics::conversions::kFahrenheitToRankineOffset | Add to °F to get °R |
| Hours per day | - | 24.0 | \([\unit{\unitless}]\) | physics::conversions::kHoursPerDay | Time conversion factor | | Minutes per hour | - | 60.0 | \([\unit{\unitless}]\) | physics::conversions::kMinutesPerHour | Time conversion factor | | Kilowatt to BTU/hr | - | \(\qty{3412.136247820839}{ \btu\per\hour\per\kilowatt}\) | physics::conversions::kKilowattToBtuPerHour | Energy conversion factor | | kg/m³ to lb/gal | - | \(\qty{0.0083454}{ \pound\per\gallon\per\kilogram\per\meter\cubed}\) | physics::conversions::kKgPerM3ToLbPerGal | Density conversion factor |
\begin{equation}\label{eq:fahrenheit-to-rankine-const} T_R = T_F + 459.67\end{equation}
\begin{equation}\label{eq:fahrenheit-to-celsius-const} T_C = \frac{5}{9}(T_F - 32)\end{equation}
| \(T_R\) | Temperature in degrees Rankine \([\unit{ \degreeRankine}]\) |
| \(T_F\) | Temperature in degrees Fahrenheit \([\unit{ \degreeFahrenheit}]\) |
| \(T_C\) | Temperature in degrees Celsius \([\unit{ \degreeCelsius}]\) |
1.9.8