Injiniringar Termodinamika: Gajeruwa da Abubuwa
Fundamentals of engineering thermodynamics tana da muhimmanci a karkashin zama duniya mafi yawa, tun daga cikin ziyarar tasirin kayan aiki, na'urar abincin, zuwa takalma darasi.
Abubuwa masu muhimmanci a kawo neman tasirin na'urar abinci su ne waɗannan kamar binciken ƙarin, ci gaba kan rawa, cost of production, and assessment of the effect on environmental. Ingini a yanzu suna yi amfani da konceptin thermodynamics don duba kuma jin daɗi abubuwa masu ingantaccen dalilin bayan hankali da kuma alaƙar da mutane.
Ilmin thermodynamics ya faru daga zamanin 19th century. Daga nan akwai ilimi da ingini suna yi amfani da ita da yanayin da yawa har zuwa yanzu.
Fundamentals of Thermodynamics
Kalmomin thermodynamics ana samu daga kalmomin Greek theme (yana nufin heat) and dynamics (yana nufin force). Professionals in engineering suna son lura da systems da kuma abubuwan da suke fitowa da ma'ada.
Concepts/Definitions used in this section are helpful for readers in understanding the concept of engineering thermodynamics (sometimes referred to as Heat-Power Engineering)
System, Surrounding and Universe
A system is something which we want to study and interested in, thus the first step is to fix precisely the objective of system study. The objective system study can be improving the efficiency of the system or to reduce the losses etc. Example of System can be to analyze the refrigeration cycle in cold storage plant or to analyze the Rankine cycle in a power plant.
A system is defined as a definite mass of pure substance bounded by a closed or flexible surface; similarly, the composition of matter inside the system can be fixed or variable depending upon the cycle.
System dimensions are not necessarily constant (like air in a compressor is compressed by a piston) it can be variable (like an inflated balloon). The matter which interacts with the system externally is called Surrounding and the Universe is the outcome of system and surrounding.
The element which separates the system from its surrounding is called boundary. The boundary of the system can be fixed or in motion.
The interaction between the system and the surrounding takes place by crossing the boundary and thus plays a very important role in thermodynamics (i.e. heat and power engineering).
Types of System in Thermodynamics
There are two basic types of systems in thermodynamics:
Closed System or Control Mass: is associated with the definite quantity of man atter. Unlike an open system, in a closed system, there is no mass flow of matter occurs across the boundary of the system. There is also a special type of closed system which does not interact and isolated itself from the surrounding is called an isolated system.
Control Volume (Open System): Control volume is limited to a region of space through which mass and energy can flow and cross the boundary of the system. The boundary of an open system is called a controlled surface; this controlled surface can be actual or unreal.
Examples of control volume are types of equipment that involve the flow of mass to cross the boundary of the system such as the flow of water through pumps, steam flow in turbines and air flow through air compressors.
Microscopic Thermodynamics
The microscopic approach in thermodynamics is also called statistical thermodynamics and is associated with the structure of matter and the objective of the statistical thermodynamics is to characterize the average behavior of the particle making up the system of interest and in turn, used this information to observe the macroscopic behavior of the system.
Thermodynamics Property, States and Process
Thermodynamic Property
A thermodynamic property is a macroscopic characteristic of a system. The value of a property can be assigned at any given time without the knowledge of previous value and its behavior.
Extensive Property
Properties that are dependent on mass are called extensive properties and its value for the overall system is the summation of its values for the parts into which the system is divided. Examples of extensive property are Volume, Energy, and Mass. Extensive property depends upon the size of a system and it can change with time.
Intensive Property
In contrast to the extensive property, an intensive property is not mass dependent and non additive in nature and does not depend upon on the total size of the system. It can vary at different places within the system at any moment. Examples of intensive property are pressure and temperature.
Thermodynamic State
A state is defined as the condition of a system which is best described by its properties. The mass enclosed in a system can be found in a variety of the unique conditions, called state. There are relations among the properties of a system but the state can be specified by providing the value of a subset of the properties.
Thermodynamic Process
Thermodynamic processes are the conversion of one state to another state. If the value of the macroscopic property of the in a system at two different time are identical then the system is said to be in a same state at that time. Steady state condition of the system is achieved if none of its properties changes with respect to time.
System Equilibrium Cycle
A thermodynamic system equilibrium cycle is a sequential process that starts and terminates with the condition of the same state. When the cycle completes then it’s all properties are having the same value what they were at the beginning. All cycles that repeats regularly plays a vital role in many areas of application, like the circulation of condensate in a thermal power generating station executes a cycle.
Working Substance
Theory of matter is helpful in understanding the concept of energy. Matter is known for its mass, volume and space and irrespective of its structure and nature it has certain characteristics like consistency and reliability. Matter is made from a large number of particles called molecules. One can find matters of Solid, liquid or gas everywhere.
In solid matter, molecules are close to each other and strongly bounded and cannot able to move freely. Thus large force required to change its shape.
Molecules in a liquid matter are not firmly held and thus a very small force is sufficient to keep the molecules together.
In a gaseous state the molecules moves randomly and freely as if it is in an unbound state then it moves very fast irrespective of its adjacent molecules. Compressibility is associated with gases, are having plenty of empty spaces between the connecting molecules. Energy is the reason for the matter to exist in different phases.
Pure Substance
Material of solo chemical structure or homogeneity in variant chemical structure is known as pure substances. Material can exist in a single phase like liquid or can also exist in more than one phase in equilibrium with each other. A uniform mixture of gases having similar chemical composition is also termed as a pure substance.
The importance of pure substance is in the determination of properties of the working substance at different conditions of pressure and temperature.
Example: For pure substance like water can be described fully by two sovereign intensive properties termed as pressure and temperature. Another pure substance is air in the gaseous state. But for non homogenous substance, more than two properties are required to describe the state.
Thermodynamic Equilibrium
In mechanics, equilibrium is said to have reached when we equalises the opposing forces. But the meaning of thermodynamic equilibrium is different and far reaching as it involves balancing act for many other influences (between and system and surrounding) apart from balancing opposing forces). In order to attain the complete equilibrium with in a system, one need to fulfil the condition for mechanical, thermal, phase and chemical equilibrium.
In this section, we are limiting our discussion to thermodynamic equilibrium. Emphasis on having equilibrium states and its change from one equilibrium to another is best described by Classical Thermodynamics.
If the state is fixed then the system is said to be in equilibrium. Intensive properties like pressure and temperature to be accurately measured in order to assign the state. A system is said to be in thermodynamic equilibrium if its intensive properties not changes on account of very little disturbance.
Under this situation, the system is in complete stability with the restraints offered by the surroundings.
Actual and Quasi-equilibrium Process
