Degree of Freedom Analysis

This is an analysis used to set the condition where properties needs to be identified. For simplification lets take an example you want to find a movie. If you know only the name of hero there might be lot of movies in the list. If you add heroine name then the list will be narrowed down. If you add director or producer in search criteria the list will be more shorter and at a point you will find the name of movie. The point will be more defined as you have certain input conditions. For example if steam is superheated then you should know the pressure as well as temperature to get the other properties like enthalpy, entropy, specific volume and other properties. In other words you need temperature and pressure to define the system at given point. If you are working with saturated steam then you need only pressure or temperature to completely define the system.  

Suitable Units of Measurement.

Always use suitable units of measurements which are easy to comprehend. We normally use these units with in out communication. As no body will tell his age in hours and distance between two cities in feets. You will not use units of tons in your kitchen. Diameter of pipes is normally given in inches and diameter of earth is mentioned in km. 

We always try to use the unit making the intensity and size of the things understandable. Water consumption per person per day is discussed in liters/day whereas flow through canals is measured in Cusecs. The capacity of tanks is given in liters and storage of Dams is measured in MAF (million acres of feet). Similarly thickness of plates is given in mm not feets or meters. Sizes of atoms are described in angstrom (A) = 10 raise to power (-10). Dust particles are measured in Microns. 

Process Dynamics

Process Dynamics will tell us "How the System will Behave in a Given Situation". Systems are living and interacting. Dynamics will show as how (Qualitative) and up to what extent (Order of dynamics) System will respond to any Situation Faced. 

Process Dynamics tries to gives picture of real time in anticipated environments. For example if a Tank is filled with water Level "L" the pressure at the base of Tank will be "P". When the water level is lowered "l" the pressure will be reduced to "p". If there is a hole at the base of Tank the flow rate through the hole of constant diameter will be directly proportional to level of water. As the level gets lower the flow through hole will also be reduced. If we want to analyse the System "water tank with a hole" in different situations like 

1- How much time is required to get the tank empty ?

2- What will be hole size if we want to empty the system in our desired time ?

3- Are the dimensions of tank are influencing the time ?  

4- At a certain time what will be the level in tank ?

We normally require the understanding of process behavior when we want to CONTROL the process.  

Entropy

Entropy is a thermodynamic property of matter. Sometimes the idea of Entropy is misunderstood. It directly indicates the availability of energy for extraction. Entropy shows the irrecoverable part of energy. In real systems Entropy increases as process proceeds. Greater the difference between Enthalpy of input and Enthalpy of output the more efficient will be the process. This can be illustrated from H-S Diagram. If a process is said to be adiabatic (no heat losses) and no friction losses then we can say it Isentropic.   

Mass and Energy Balance

What goes in comes out, law of conservation of mass. Water in a Tank with one input and one output is easiest system to understand the mass balance. If water input is equal to water output the level in the level will remain unchanged. If input is more then output the level will rise and if the output is more then input the tank will exhaust. It seems simple but if we take example of water level in fire tube boiler then the example becomes very critical. As level control in boiler shell is the most important parameter when dealing with fire tube / smoke tube boilers. The supply should be maintained to cope with demand keeping the acceptable safe level of water in shell. The low water level is safety issue and high water level is steam quality issue (reduction in steam disengagement area). This is not simple as pressure and temperatures of the system is high.

Energy streams also follows the law of conservation. For example water heating in a paper is a good example of energy input and output. The paper will not burn as long as the no accumulation of heat in its and all the heat supplied is transferred to water. Similarly boiler operation will be safe as long as it transfers the heat of fuel combustion to water. If some part of the outside of tubes gets dry, the material of tube will be overheated and material damage can occur. The same thing can observed when you operate the electric heater rods in a low level or empty container. The supply of heater input energy remains the same (kW) but the heat recipient is air in place of water which act as insulator so same exposed area cannot transfer the heat from electric rod to air. The same energy needs a larger area to transfer heat to air and avoiding accumulation of heat in the rod itself. Here a very important parameter "Area of Heat Transfer" comes into play. 

It always starts with a simple but when conditions rise (Temperature, Pressure, Concentration, pH) throughput increases more and more variables come into play. The insignificant things becomes significant and creates impacts. For example if you transfer drinking water (say 250 ml) from a bottle in a glass it looks simple but when you have to transfer the 101 m3 (101 tons) of water to a plant many things come into play. For example lifting a glass of water (250 gms + weight of glass) for drinking is very easy but when we talk of million gallons per day lift requires external sources. Further more when this water has to interact with the systems at higher temperatures and pressures more and more variables come into play and complex models are developed which represents the real systems up to a satisfactory level.

Process conditions and interacting systems decides the stability of systems. For example one drop of bad milk can deteriorate the 10,000 liter milk tank. Minor change in the pH can disturb the whole process through changing the reaction rates.  

Standardization and Calibration

Standards are very important part of our life. For example if you buy a watch in Switzerland it will be usable anywhere on earth as time is standardized measurement. Sixty seconds in USA will be equivalent to Sixty seconds in UK. 

If we want to import any equipment  from a foreign country standards will help us in making decisions. One feet of pipe will be one feet anywhere on earth. So standards help us in ensuring the technical communication and confidence. Size of A4 will be used in all the A4 printers regardless of brands. Similarly your ATM Card will fit in every ATM machine in the world.

Calibration is comparison of something with actual standard. In daily life we also do little calibrations. Like measuring some lengths with your extended palm calibrated against standard feet.