 students, myself Ganesh Biajlawe working as an assistant professor in Department of Mechanical Engineering, Walsh University of Technology, Singapore. In this session of thermodynamics, we will see vapor power cycle, Carnot cycle, learning outcome. At the end of this session, students will be able to describe Carnot cycle and also will be able to evaluate Carnot efficiency. There are two types of the Carnot cycles. First one is the single phase Carnot cycle and second one is the two phase Carnot cycle. We will see one by one. In the single phase Carnot cycle, generally we represent the Carnot cycle on temperature entropy plot. Remember, if you are interested to study the work interaction, try to show the cycle on the pressure volume diagram. And if you are interested for study of the heat, then adopt the temperature entropy diagram. First type of the cycle is single phase Carnot cycle. In that Carnot cycle, it is assumed that the piston and cylinder arrangement is there. There are concepts like hot body, this is the hot body and this is the cold body. Suppose, at the beginning of the Carnot cycle, hot body is brought in contract with the cylinder head. Then in the Carnot cycle, the heat supply from state 1 to 2 will follow isothermal process. The heat is supplied to the system is at isothermal. The temperature during heat addition remains constant. Carnot cycle is ideal cycle, is imaginary cycle. So all assumptions are there. The assumptions are like this. All the processes are reversible processes, there is no heat loss, friction is absent. So with these assumptions, we are going to study the Carnot cycle. After the process 2 and after completion of the heat addition, the system will be able to develop some amount of work and that work development will follow isentropic process. So 2 to 3 is isentropic work development process that is represented by W e. To have the expansion process, isentropic expansion process, one more assumption is that the time taken by this piston to move from BDC to TDC is infinite means the movement is very, very, very slow as infinite time is available, okay, so this is the next assumption. After reaching the bottom dead center, the system starts rejecting the heat and once again it will follow the isothermal heat rejection. During process 3 to 4, the heat rejection will continue from state 3 to state 4 and there won't be any decrease in the temperature as this is the theoretical process. Now next process, to have the next process, remember the heat rejection will be from this system to the cold body, this system to this cold body means we need to bring this cold body in contact with the cylinder head, so that there will be heat rejection. For heat supplied, we brought hot body in contact with the cylinder head and during heat rejection, we will remove this hot body and we will bring this cold body in contact with the cylinder head. Now fourth process for single phase Carnot cycle is the compression or pressurization process. During the pressurization or compression process, the piston will move from BDC to TDC, it will move from BDC to TDC and there will be rise in the pressure from 0.4 to 0.1. Obviously some amount of work is to be given and that is represented by suppose WC. So the Carnot cycle is from 1, 2, 3, 4, 1 and the saturation curve is, if we want we can draw the saturation curve will be somewhere here, so what is observed? The working fluid is in the single phase, it does not undergo the phase change that is why this is called single phase Carnot cycle. Now second type of Carnot cycle is two phase, two phase Carnot cycle. Once again I will show it on the TS plot, I will show it on the TS plot, temperature versus specific entropy and first of all I will draw the saturated curve, this is the saturated curve. In the two phase Carnot cycle, the fluid at the beginning of the heat supply is on the saturated liquid curve. Heat supply occurs isothermal, isobarically up to point number 2. Now what has happened here? The saturated liquid has converted into saturated vapor during the supply of heat QS. Next process is expansion process which will follow isentropic expansion from point 2 to point 3. So what happened here? The saturated vapor entered in the weight region by following the Carnot cycle. Then 3 to 4 will follow isothermal heat rejection process and fourth process is isentropic compression process. So work consumed is Wc, work rejected is, work developed is We. So here we have shown the Carnot cycle for two phase fluid, two phase fluid. Now this is quite a difficult because there is no pump available practically which will be converting the weight steel into saturated liquid during compression process that is why the practicable cycle is Rankine cycle that is to be kept in mind. Now how to calculate the efficiency? So Carnot efficiency, Carnot efficiency which is the maximum possible efficiency or theoretical efficiency is T1 minus T2 divided by T1. Now it is T1, do not get confused with the notations. T1 is the high temperature energy reservoir and T2 is low temperature energy reservoir. We could write this as Th and Tl also, so there may be confusion in the notations. So I could write Th minus Tc by Th. This is the equation which can be used for calculating the Carnot efficiency. Now this equation is applicable for single phase fluid also and for two phase fluid also. For further study you can refer fundamentals of thermodynamics by Boranke Sontek and the fundamentals of engineering thermodynamics by Moran Sherpy Rowe. Thank you.