# Intro CoolProp is a opensource library for material properties with wrappers for many languages and platforms. # Access REFPROP form coolprop ```python import CoolProp.CoolProp as Cp # tell where refprop is located Cp.set_config_string(Cp.ALTERNATIVE_REFPROP_PATH, "C:\\Program Files (x86)\\REFPROP\\") Cp.PropsSI('D','P', 101325, 'T', 300, 'REFPROP::Water') # Refprop water Cp.PropsSI('D','P', 101325, 'T', 300, 'Water') # coolprop water ``` you can also set `ALTERNATIVE_REFPROP_PATH` environmental variable The following are fluid properties commonly encountered while working in Fluid Mechanics. Also included is a simple snippet that shows how to get properties of water using [[CoolProp]] and [[REFPROP]] # Fluid Properties ## 1. Density Density $\rho$ is the mass per unit volume of the fluid. ### 1.1. Unit Conversion $1 kg/m^3 = 0.001 g/cm^3= 1/16.018 lbm/ft^3 = 1/(16.018*1728) lbm/in^3 $ ### 1.2. CoolProp SI Units ```python Cp.PropsSI("D", "P", 101325, "T", 300, "Water") # Density of water at 101325 Pa and 300 K is 996.556935...kg/m^3 ``` ### 1.3. REFPROP English Units ```Excel =Density("Water","TP","E",80.33, 14.6959) "62.21301706 lbm/ft^3" ``` ## 2. Specific Weight *do not confuse with Specific Gravity Specific weight is the weight (force exerted under gravity) per unit volume of the fluid. Units are $N/m^3$ or $lbf/ft^3$. It is denoted by $\gamma$ $\gamma = \rho g$ Where $g$ is the gravitational constant at the location (typically 9.81 $m/s^2$ or 32.174 $ft/s^2$) ## 3. Specific volume Specific volume is inverse of density $v=\frac{1}{\rho}$ ## 4. Specific Gravity Specific gravity is the ratio of density of a substance to density of water. It is denoted by $SG$ $SG= \frac{\rho_{liquid}}{\rho_{water}}$ ### 4.1. API Gravity API gravity is used in the oil industry to measure specific gravity. It is a measure of how heavy or light a petroleum liquid is compared to water. If API >10, it floats on water and if API<10 it sinks. It is usually calulated at standard conditions of 60°F $API\ gravity = \frac{141.5}{SG}-131.5$ ## 5. Specific Heat Specific heat is the amount of heat that must be applied to a substance to increase the temperature of a unit mass by one degree. Typical units are $J/kg.°C$ or $BTU/lbm.°F$ ### 5.1. Gases Gases have two types of specific heat depending on how the heat is added - constant volume $c_v$ - constant pressure $c_p$ Since $c_p$ is based on a constant pressure process $c_p = \frac{\partial h}{\partial T}$ where, $h$ is the enthalpy of the fluid. and since $c_v$ is based on a constant volume process $c_v=\frac{\partial u}{\partial T}$ where, $u$ is the enthalpy of the fluid. #### 5.1.1. Gas Constant Difference getween cp and cv gives the [[#Gas Constant|gas constant]] R $c_p-c_v=R$ #### 5.1.2. Specific heat Ratio Ratio of specific heat is denoted by a greek symbol $\gamma$ $\gamma = \frac{c_p}{c_v}$ ### 5.2. CoolProp SI Units ```python # c_p using c_p Cp.PropsSI('C','P',101325,'T',300,'Air') # you can use C, CPMASS, or Cpmass # c_p using derivative Cp.PropsSI('d(Hmass)/d(T)|P','P',101325,'T',300,'Air') # 1006.3739...J/kg-K # c_v using c_v Cp.PropsSI('CVMASS','P',101325,'T',300,'Air') # you can use CVMASS, or Cvmass # 717.9715...J/kg-K ``` ### 5.3. REFPROP English Units ```Excel =Cp("Air","TP","E",80.33, 14.6959) =Cv("Air","TP","E",80.33, 14.6959) ``` ## 6. Viscosity ### 6.1. Absolute (Dynamic) Viscosity Absolute viscosity $\mu$ is the proportionality factor relating fluid shear stress and rate of deformation $\tau = \mu \frac{\partial u}{\partial y}$ where, - $\tau$ is shear stress - $\frac{\partial u}{\partial y}$ is rate of change of deformation. i.e.delta change in velocty per delta change in distance normal to the wall Units of absolute viscosity are $kg/m.s$ or $N.s/m^2$ or $Pa.s$ or $lbm/ft.s$ or $lbf/ft^2.s$ #### 6.1.1. Conversion - $lbf/ft^2.s$ is also called $Reyn$ - $0.1 kg/m.s$ is $1Poise$ - Viscosity of water is ~ $0.01 Poise$ or $0.001 kg/m.s$ or $6.7304\times10^{-4}\ lbm/ft.s$ #### 6.1.2. CoolProp SI Units ```python Cp.PropsSI('V','P',101325,'T',300,'Water') ``` #### 6.1.3. REFPROP English Units ```Excel =Viscosity("Water","TP","E",80.33, 14.6959) "result- 6.73042E-04 lbm/ft-s" ``` Note: Using SI units in REFPROP gives viscosity in $\micro Pa-s$ ### 6.2. Kinematic Viscosity Kinematic viscosity is dynamic viscosity divided by density. Measurement of kinematic viscosity is more accurate than measuring dynamic viscosity. Kinematic viscosity is measured by the noting the time required to pass a given volume of fluid under its own head through a small diameter tube. A *Saybolt viscosimeter* is most commonly used. Units of kinematic viscosity are $m^2/s$ or $centistokes$ or $ft^2/s$ $1\ stoke = 1\ cm^2/s$ ## 7. Heat of Vaporization & Fusion Fusion - heat necessary to change a unit mass of liquid into solid state at constant temerature. Vaporization - heat necessary to change a unit mass of solid or liquid into gaseous state at constant temerature. ## 8. Bulk Modulus Bulk modulus $\beta$ is a measure of fluid compressibility. It can be calculate adiabatic or iso thermal $\beta = -V\left(\frac{\partial \rho }{\partial V}\right)$ #### 8.1.1. REFPROP English Units ```Excel =AdiabaticCompressibilty("Air","TP","E",80.33, 14.6959) units are 1/psia ``` ## 9. Volumetric Thermal Expansion Coefficient $\beta$ is volumetric thermal expansion coefficient (volume expansivity in [[REFPROP]]) i.e. fractional change in density to a change in temperature at constant pressure $\beta = -\frac{1}{\rho}\left(\frac{\partial \rho }{\partial T}\right)_p$ ideal gas $\rho=p/RT$ and the above equation reduces to $\beta=\frac{1}{T}$ #### 9.1.1. REFPROP English Units ```Excel =VolumeExpansivity("Air","TP","E",80.33, 14.6959) units are 1/°R ```