In this article we will discuss about:- 1. Formation of Steam 2. Conditions of Steam 3. Properties 4. Enthalpy. Formation of Steam: Generation of One Kg of Steam at a Given Pressure from Water Initially At 0°C: Let us decide upon the pressure under which one kg of water is to be heated. After fixing the pressure we can know [...]
Compilation of exam questions on thermal engineering for engineering students. Exam Question # 1. What is the difference between enthalpy and entropy? Ans. Enthalpy: A working substance in any state has a certain amount of internal energy. Besides, it also has some potential energy which is proportional to the absolute pressure and the specific volume i.e., to the product PV. [...]
Specific Heats of a Gas: Formula, Constant Pressure, Ratio and Heat Capacity! Specific Heats of a Gas: The specific heat capacity of a substance may be defined as the quantity of heat required to raise the temperature of unit mass of the substance by one degree. The unit of specific heat is J/kg-°C. Since this unit is small it is [...]
Liquids are heated and evaporated at constant pressure. The vapours are also superheated at constant pressure in superheaters. For this reason the entropy of vapours can be calculated from the formula for the change of entropy at constant pressure. We consider the entropy of vapour in three phases of formation. In the following topic the entropy of steam and the [...]
Thermodynamic Processes and Equations! A process is a change in the state of a gas as a result of flow of energy. During this flow a change takes place in properties of the substance such as pressure, volume, temperature and also the energy quantities such as internal energy, heat and work. The five important processes commonly dealt with in engineering [...]
In this article we will discuss about:- 1. Carnot Cycle 2. Rankine Cycle 3. Modified Rankine Cycle. For some type of heat engines (gases) heat exchange at constant temperature is impracticable and hence, Carnot cycle cannot be practicable for gas power plants. Heat exchange at constant temperature for saturated vapour also takes place at constant pressure in some devices such [...]
Classification of Thermodynamic Cycles! Thermodynamic Cycle # I. Carnot Cycle: It consists of two isothermal processes and two isentropic processes. This cycle is represented on temperature-entropy and pressure-volume diagrams as shown in fig. 2-34. Consider one kg of air at temperature T1 as the working fluid in the engine cylinder. Let point 1 (fig. 2-34) represent the state of the [...]
As in the case of gases, the vapours may also be expanded or compressed by different methods as given below: Method # 1. Constant Volume Process (fig. 3-14): An example of constant volume process is the heating of steam in a closed rigid vessel. As there is no change in volume, work done in this process is zero. By the [...]
There are four methods of determining the dryness fraction of steam. They are as mentioned below: 1. Bucket Calorimeter: This method of determining the dryness fraction of steam is not exact. The value of dryness fraction obtained by this method is lower than the actual value. The apparatus shown in fig. 3-21 consists of a copper calorimeter which is placed [...]
The two methods used to feed the pulverized fuel to the combustion chamber of the power plant: 1. Unit System 2. Central or Bin System. In unit system, each burner of the plant in fired by one or more unit pulverizers connected to the burners, while in central system, the fuel is pulverized in the central plant and then distributed [...]