Boltzmann's Constant

Boltzmann's Constant (k) is a relation of macroscopic and microscopic properties. It is a physical constant relating energy at the individual particle level with temperature.

Where R is ideal gas law constant.

Avogadro Number.

The accepted value in SI units is 1.38064852(79)×10−23 m2 kg s-2 K-1

It has same dimensions as that of Entropy. 

Thermodynamic Cycles

1- Thermodynamic Power Cycle

Heat Flows from Higher Temperature to Lower Temperature and Work is an output.  

1a- Vapor Power Cycle (Vapor is the main Working Fluid)

      Carnot Cycle 
      Ideal Cycle, Indicating the maximum possible efficiency between two temperature reservoirs. It is a hypothetical cycle assuming processes are isentropic and adiabatic. Which can be seen on T-S Diagram of Carnot Cycles. The concept of entropy is not available in the Carnot Cycle. 

Actual Situation

Isentropic expansion will result in increase in moisture content which is harmful for turbine blades. Isentropic compression of mixture requires more work input. 

      Rankine Cycle

It is an idealized cycle for heat engines. The Rankine Cycle is much more practical then the Carnot Cycle because the working fluid typically exists as a single phase (liquid or vapor) for the two pressure change processes. 

1b- Gas Power Cycle (Gas/Air is main Working Fluid)

      Brayton Cycle

      Otto Cycle

      Diesel Cycle

2- Heat Pump / Refrigeration Cycle

Heat Flows from Lower Temperature to Higher Temperature through input of Work. 

Thumb Rules

Velocity at Pump Inlet and Outlet

1- Velocity should not exceed 1.8 m/sec [5.9 ft/sec] at Suction Pipe

2- Velocity should not exceed 2.5 m/sec [8.2 ft/sec] at Discharge Pipe

3-Velocity below 0.5 m/sec [1.64 ft/sec] give rise to sediments

4-Velocity above 5.0 m/sec [16.4 ft/sec] give rise to abrasion

API Gravity

Specific Gravity

The term specific gravity, symbolized sp gr, refers to the ratio of the density of a solid or liquid to the density of water at 4 degrees Celsius. The term can also refer to the ratio of the density of a gas to the density of dry air at standard temperature and pressure, although this specification is less often used. Specific gravity is a dimensionless quantity; that is, it is not expressed in units.

API gravity is calculated using the specific gravity of an oil, which is nothing more than the ratio of its density to that of water (density of the oil/density of water). Specific gravity for API calculations is always determined at 60 degrees Fahrenheit.  API gravity is found as follows:

Though API values do not have units, they are often referred to as degrees. So the API gravity of West Texas Intermediate is said to be 39.6 degrees. API gravity moves inversely to density, which means the denser an oil is, the lower its API gravity will be. An API of 10 is equivalent to water, which means any oil with an API above 10 will float on water while any with an API below 10 will sink.

The API gravity is used to classify oils as light, medium, heavy, or extra heavy. As the “weight” of an oil is the largest determinant of its market value, API gravity is exceptionally important. The API values for each “weight” are as follows:

Light – API > 31.1

Medium – API  between 22.3 and 31.1

Heavy – API < 22.3

Extra Heavy – API < 10.0

Viscosity

Viscosity is the resistance of a fluid to flow. Virtually all fluids have viscosity which generally changes as a function of temperature; although different types of fluids exhibit different types of fluid–shear velocity dependencies.

“When a fluid or semisolid is subjected to a constant shearing force it flows, i.e., it deforms continuously at a velocity that increases as the applied shearing force increases.” Viscosity quantifies the resistance of the fluid to flow

Introduction

Viscosity is a quantitative measure of fluid’s resistance to flow (shear stress) at a given temperature. This resistance arises from the attractive forces between the molecules of the fluid. A fluid will only flow if enough energy is supplied to overcome these forces.

Dynamic Viscosity / Viscosity

The dynamic viscosity (η) of a fluid is a quantitative measure of the resistance it offers to relative shearing motion.
Dynamic viscosity, which is also referred to as absolute viscosity, or just viscosity, is the quantitative expression of a fluid’s resistance to flow (shear). Fluid dynamicists, chemical engineers and mechanical engineers commonly consider the use of the Greek letter mu (µ) as the symbol to denote dynamic viscosity.

Units

The SI unit is pascal-second [Pa.s] or millipascal-second [mPa.s]:

    1 Pa.s = 1000 mPa.s
    The SI unit is named after Blaise Pascal.

Other commonly used units are poise [P] or centipoise [cP]:

    1 P = 100 cP
    This unit is named after Jean Poiseuille

    1 cP = 1 mPa.s = 0.001 Pa.s = 0.01 P

However, the most common expression is centipoise (cP), which is mainly used in ASTM standards.

Kinematic Viscosity

It is defined as the ratio of absolute viscosity to the density of fluid. Kinematic viscosity describes a substance's flow behavior under the influence of Earth's gravity. It is dynamic viscosity divided by density ρ, rho, which is defined as mass per volume. The quantity mass carries the gravitational influence. Kinematic viscosity is sometimes called the diffusivity of momentum.

        ν= η/ρ

Units

The SI unit is square-meters per second  [m2/s] or square-millimeters per second [mm2/s]:

    1 m2/s = 1 000 000 mm2/s

Other commonly used units are stokes [St] or centistokes [cSt]:

    1 St = 100 cSt

This unit is named after George G. Stokes.

    1 cSt = 1 mm2/s

 It should be noted that water (H2O) at 20 degrees centigrade is about 1 cSt.

Relation of Kinematic Viscosity with Dynamic Viscosity

Limitations

The above equation holds only when

1-Fluid is Newtonian

2-Specific Gravity Remains the Same

Application

Liquids are generally considered viscous if viscosity is more then 40 centipoise (cp). Centrifugal pumps are not recommended for fluid having viscosity more then 300 centipoise (cp).

The viscosity of liquids decreases with increase the  temperature. Typically 2% per degree C. For some materials (fruit juices) the Temperature effect follows an Arrhenius relationship. 

Viscosity of gases increases with the increase the temperature.