 Hello, I am Ganesh Pyaglavi, working as an assistant professor in Department of Mechanical Engineering, Valchin Institute of Technology, Solapur. In this session, we will see vapor compression cycle actual learning outcome. At the end of this session, students will be able to describe actual vapor compression cycle and derive actual COP. In the previous sessions, we have studied the schematic diagram of vapor compression cycle. We have shown VCC on pH diagram. Now if we will consider the practical considerations into account, then this dotted line derives representing theoretical cycle will get modified into actual one. In actual VCC, the pressure drop caused due to the friction between the refrigerant and the tube wall is considered. Then there will be wire drawing process. The practical compression process, practical condensation process, all these parameters are considered. So we will start with the inlet to the compressor. For theoretical VCC, the assumption was the refrigerant leaving to evaporator was at saturated state that is point this point. Now practically there will be heat gain by this saturated refrigerant or vapor refrigerant present inside the evaporator. It will take the heat from the surrounding because the evaporator will be connected to the compressor by means of tube. That heat gain will increase the enthalpy of the vapor refrigerant, thereby there is also decrease in the pressure. We will see this at the time of the evaporation. But the first point is the gain in the heat that is why there is super heating of the vapor refrigerant from this point that is suppose point 1 dash to point 1. So superheated vapor will enter into the compressor which will get compressed actually. So here 1 to 2 is the actual compression process while for theoretical VCC the compression was yes recall yes it is isentropic compression process but for actual VCC it is actual compression process. So depending upon the specific heats there will be the value of the compression index. Now this point 2 is the actual compression process. So at point 2 the more superheated vapor refrigerant is leaving the compressor. For theoretical the exit refrigerant temperature was at this point. So there is more superheating caused due to practical considerations. Now the refrigerant leaving the compressor is to be condensed back to the liquid phase. For theoretical condensation process this was isobaric condensation process from suppose this 2 dash point to this suppose 3 dash point this was constant pressure that is isobaric condensation process in which the heat was rejected by the refrigerant to the surrounding. But practically as there is a superheating from point number 2 to this saturated point there will be some pressure drop that will be inclination it will be shown if I will enlarge much more this figure then there will be inclined line from 2 to saturated curve further the refrigerant will enter into the weight region and further pressure drop will occur because of the friction between this liquid or weight refrigerant and the tube. Then it will leave at saturated liquid condition for the theoretical VCC but for the actual VCC it will enter into the superheated region because of further continuation in the heat rejection by the refrigerant to the surrounding. So point number 3 is representing actual exit condition of subcooled liquid refrigerant from the condenser. Now we can install P1 pressure gauge to the suction of compressor, P2 pressure gauge at outlet of the compressor, P3 pressure gauge at outlet of the condenser and the decrease in the pressure can be calculated as P2 minus P3 which can be represented by del P delta P condensation which will be difference between P2 minus P3. Now in the actual VCC also here we are making the assumption of the expansion process as throttling process. In the throttling process isenthalpic expansion is assumed that is why we have drawn 3 to 4 line as parallel line to the pressure or constant isenthalpic line that is H3 is equal to H4. Now for saturated VCC the refrigerant entering into the evaporator was suppose at this 4 dash, 4 dash why for actual as there is more subcooling it will enter into the evaporator having lower drainage fraction than theoretical which may be beneficial as there is increase in the refrigerating effect. Constructionally evaporator and condenser are of the same shape the construction of the condenser evaporator will be same that is why there are evaporator tubes as that of condenser tubes. So when this wet refrigerant or neglecting this of flashing of the liquid refrigerant I can call this as a liquid refrigerant which enters into the evaporator will gain the heat from the surrounding which is to be cooled. Because of that the flow of liquid refrigerant through the tube the pressure will be decreasing. There will be decrease in the pressure of refrigerant when it flows through the evaporator. We can also measure the decrease in the pressure or pressure loss or pressure drop in the evaporator by taking the difference of P4 minus P1. So theoretically the refrigerant is to be leaving the evaporator at a saturated but as evaporator is connected to the compressor there is heat gain and that pipe leads to pressure loss of the vapor refrigerant that is why point 1 is below the evaporator theoretical pressure. Now this pressure drop is to be considered while designing the evaporator for example we requires temperature in the evaporator minus 20 degree Celsius and it leaves at minus 22 degree Celsius. Then this pressure drop is to be considered for maintaining minus 20 degree Celsius accordingly the pressure ratio is decided and this minus 22 or minus 2 degree Celsius difference is considered while designing the evaporator. Now the actual VCC considering all the practical considerations will be 1, 2, 3, 4, 1 this is the actual VCC. More accurate curve can be plotted on the PH chart of that particular refrigerant by installing n number of pressure gauges. For example this is the schematic representation of actual condensation for which there were only 2 pressure gauges. I can increase the number of pressure gauges for example this is suppose 1st, 2nd, 3rd, 4th and up to n number then I can locate those points along with the corresponding temperature on the PH chart and I can draw the smooth line from those points for getting the actual condensation. Same method is applicable to EO operation. So this is the actual VCC and for comparison purpose you can consider the schematic diagram of theoretical VCC. I can represent the VCC on PH chart. So suppose this is 1, 2, 2 is the isentropic compression 2, 2, 3 is the isobaric condensation 3 to 4 is the isentropic expansion 4 to 1 is the refrigerating effect. Now measure the actual pressures and temperature, locate the point at inlet to compressor, outlet to compressor, outlet of condenser, inlet to the EO operator and simply join those points you will get the actual VCC. For further study you can refer refrigeration and air conditioning by CPR Aura and WF Stoker. Thank you.