 Hello, I am Ganesh Biyagalai working as an assistant professor in Department of Mechanical Engineering, Valjean Institute of Technology, Solapur. In this session of a vapor compression cycle, we will see introduction of VCC, Learning Outcome. At the end of this session, students will be able to describe vapor compression cycle, express the formula for condenser heat, compression work and COP. In the vapor compression cycle, in short, we will be using VCC stands for vapor compression cycle or system. This is the basic cycle, which is used in the field of HVAC. In VCC, there are four devices are there. First one is the compressor followed by condenser, expansion ball, evaporator. Now, this is the symbol for compressor. The function of compressor is to compress the vapor refrigerant. For theoretical VCC cycle, the inlet to the compressor is assumed as saturated vapor. So, compressor will compress dry and saturated refrigerant vapor into superheated vapor. After studying this schematic diagram, we will plot the cycle on pH diagram. Now, this superheated steam is passed through the condenser. The condenser may be tube-in-tube type, shell-in-tube type or shell-in-coil type. So, second device is the condenser. As the superheated vapor will flow through the condenser tubes, there will be heat rejection to the surrounding. So, total amount of heat rejected by the superheated refrigerant is denoted by QC. Now, obviously, the condensation process will be isobaric process means constant pressure heat rejection process. After passing through the condenser tubes, the superheated vapor refrigerant will undergo the desuperhating process. Consider up to this 2 dash, there is a desuperhating process and from 2 dash to 3 is the condensation process means for theoretical VCC, at state 3, we will get saturated liquid refrigerant. Now, this process which is from outlet of compressor to outlet of condenser is isobaric has high pressure or condenser pressure. The pressure possessed by this refrigerant is high. This pressure is to be reduced up to designed EO operator temperature. That is why we required one expansion wall. Now, there are different types of the expansion walls. First one is very simple capillary tube, second one is the thermostatic expansion wall, automatic expansion wall, internally expansion wall, externally equalized expansion wall. So, these are the types of the expansion walls. Compression process was isentropic compression process. The condensation process was isobaric condensation process, but here in the expansion wall the type of process takes place is known as isentropic. So, the enthalpy during expansion process that is throttling process remains same. That is why the saturated liquid will undergo the throttling process and outlet of expansion wall will get low pressure wet refrigerant. So, this wet refrigerant will possess the low pressure low pressure and depending upon the design temperature it will have that low temperature. Now, we can pass this LP LT refrigerant through the EO operator through the EO operator. Now, the types of the EO operators are same as that of the condenser except flooded type of the EO operator or dry expansion type of the EO operator. So, this is the EO operator which is surrounded by this EO operator coils, EO operator coils. So, when this liquid refrigerant starts flowing through the EO operator it absorbs heat from the product to be cooled which is kept in the EO operator. For domestic refrigerator we are calling this EO operator as freezer. So, what we are doing we are keeping the ice creams or any water for freezing purpose in the freezer. Once the heat absorbed by this liquid refrigerant will be which type of the heat can you recall if there is a change in phase of the refrigerant then the type of heat will be either sensible or latent heat. So, please recall yes it is a latent heat. So, more amount of heat will be absorbed by this liquid refrigerant which is at low pressure low temperature from the stored product. This is nothing but the refrigerating effect denoted by QR. So, to achieve this refrigerating effect the work supplied to the compressor is WC. Now, this EO operator is directly connected to the compressor. So this is known as vapor compression cycle. So, this is the schematic diagram which we have studied now. Now we will move to the pH diagram to pH diagram because it becomes very easy if we will plot this cycle on pressure versus enthalpy pressure versus enthalpy. It has a saturated curve like this shape this is the high pressure. We use the notation condenser pressure PC the pressure in the EO operator is low. So, notation will use PE stands for EO operator pressure so this is the EO operator pressure. Point number one that is the state of the refrigerant at inlet to the compressor is dry and saturated. So, for theoretical VCC we will assume the state of refrigerant at outlet of EO operator or to inlet compressor is dry and saturated. So, 1 to 2 will be isentropic compression process 1 to 2 is the isentropic compression process then the superheated vapor refrigerant will enter into the condenser because of its high temperature it starts de superheating by rejecting heat to the surrounding from point number 2 to 2 dash. This is the tentative point I have shown here so 2 to 2 dash is the de superheating process then from 2 dash to 3 2 dash to 3 is the condensation process here the phase will change from saturated vapor to saturated liquid. During that process that is from 2 to 3 the condenser is going to reject heat to the surrounding as the surrounding temperature will be lower than the condenser temperature. Accordingly you have to design the condenser temperature condenser pressure nothing but the pressure ratio of the compressor. Now, we got the liquid refrigerant at outlet of the condenser as this is the closed cycle we required to reduce its pressure that is why this is the expansion wall. In the expansion wall there will be throttling process the enthalpy will remain same there will be pressure drop from condenser pressure to evaporator pressure. So, 3 to 4 is the isentropic expansion process in this process there will be some loss of liquid refrigerant and 4 to 1 is the refrigerating effect. Now, from this diagram I can write the equations for compressor work which is equal to difference in the enthalpy that is H 2 minus H 1 heat rejected by condenser is equal to H 2 minus H 3 thus I can derive the COP theoretical COP of the refrigerator which is equal to refrigerating effect refrigerating effect divided by work consumption. Here the refrigerating effect is during the E operation which occurs in the E operator. So, which is the difference between H 1 minus H 4. So, COP COP of the refrigerator will be equal to H 1 minus H 4 by H 2 minus H 1 this is the theoretical COP of the refrigerator. If we will assume this as the heat pump then just I have to replace Q R by Q C then it will become then it will become COP of heat pump will be equal to Q C divided by W C. So, this is all about vapor compression cycle for further study you can refer refrigeration and air conditioning by C P Rora and W F Stoker. Thank you.