 Hello, I am Ganesh Biyagalai working as an assistant professor in Department of Mechanical Engineering, Valchin Institute of Technology, Solapur. In this session of a vapor compression cycle, we will see methods to improve COP, learning outcome. At the end of this session, students will be able to illustrate regenerative vapor compression cycle and derive COP. In the previous session, we have seen subcooled VCC, superheated VCC. Now we will go for the regenerative VCC. These are the three methods for improving the COP. In the regenerative VCC, there is heat exchanger. To this heat exchanger, there will be flow of low pressure, low temperature, vapor refrigerant and the counter flow fluid has high pressure, high temperature properties. Now this regenerative heat exchanger is connected to EO operator. The outlet of EO operator is given to inlet of heat exchanger. This is EO operator. This heat exchanger, regenerative heat exchanger is connected to the compressor. So here we are going to modify simple VCC to get the regenerative VCC cycle. Outlet of compressor, outlet of compressor, superheated refrigerant in the same manner as that of the simple VCC will flow through the condenser. In the condenser, there will be condensation of superheated vapor into saturated VCC. Then this condenser is connected to the regenerative heat exchanger. This high pressure, high temperature refrigerant will do the heat transfer, will reject the heat. So this sub cooled refrigerant will undergo the expansion process that is throttling process. So this becomes the schematic diagram of vapor to vapor or regenerative heat exchanger. Now we will give the notation 1 to outlet of vapor refrigerant of the EO operator. The refrigerant leaving the EO operator will consider it is dry and saturated vapor. As it has low pressure, low temperature, it will gain the heat from the counter flowing high pressure, high temperature liquid refrigerant. So high pressure, high temperature refrigerant is rejecting heat to same refrigerant because this is closed cycle and in the regenerative heat exchanger single refrigerant is used. So there will be heat exchange between high pressure, high temperature refrigerant coming from the condenser to low temperature, low pressure counter flowing vapor refrigerant. That is why this is the counter flow type of the heat exchanger. Now 1 to 1 dash will be heat gain by the low pressure refrigerant. Then there will be compression from 1 dash to 2 actual cycle I will show on the pH plot. 2 to 3 will be the isobaric condensation process. Then at the same state this liquid refrigerant will enter into the heat exchanger and there will be decrease in the heat from 3 to 3 dash. At 3 dash refrigerant will undergo the throttling process, its pressure will get decreased from condenser pressure to E operator pressure I will use notation 4 dash for the heat exchanger meanwhile you consider it as a 4. Now this process will show on the pH plot, on the pH plot. So this is the pH plot, this is the saturation curve. We have drawn in the previous session the saturated VCC curve and the notations were 1, 2, 3, 4. These notations were used. Now for saturated VCC the vapour leaving the E operator is at 1 which is saturated vapour. As we will use the regenerative heat exchanger this refrigerant will gain the heat in the pipe from 1 to 1 dash. This much amount of the connection connected pipe will be inside the heat exchanger. We can make the assumption the pipe which connects the E operator and heat exchanger is perfectly insulated. So heat transfer is possible inside the heat exchanger only that is why heat gain from 1 to 1 dash from 1 to 1 dash by the low pressure low temperature vapour refrigerant will happen in the heat exchanger. And this process already can you recall 1 to 1 dash in which type of the COP improvement method we have seen. Yes this is the super heating 1 to 1 dash. At 1 dash the superheated refrigerant will enter into the compressor and there will be compression from 1 dash to 2 dash. This is the new compression process. Then at 2 dash now this more superheated refrigerant will undergo the condensation process from 2 dash to 3, 2 dash to 3 in the condenser assuming the pipe which connects the condenser and the heat exchanger is perfectly insulated, perfectly insulated. The heat transfer will occur inside the heat exchanger from 3 to 3 dash that is why because of heat rejection because of heat rejection below the saturated liquid curve there will be subcoiling process from 3 to 3 dash. Then at 3 dash there will be throttling process there will be throttling process and at 4 dash more liquid refrigerant, more wet refrigerant having lower dryness fraction will enter into the EU operator and will get more refrigerating effect. So by using the regenerated heat exchanger simultaneously we will get the superheating and subcoiling process. Now what is its effect on the COP? For theoretical VCC, theoretical VCC we had written COP is equal to refrigerating effect divided by work consumption and the refrigerating effect was H1 minus H4 divided by H2 minus H1. Now for new refrigerating effect that is by using the regenerated heat exchanger will get new COP denoted by dash which is equal to new refrigerating effect divided by new work consumption which is equal to there is increase in the refrigerating effect H1 dash minus H4 dash divided by there is increase in the work consumption H2 dash minus H1 dash. Now using the heat exchanger regenerated heat exchanger there is improvement in the refrigerating effect and at the same time there is increase or improvement in the work consumption. So numerator and denominator both terms are increasing. So the prediction of COP depends on the type of refrigerant used in the VCC. Now how many types of refrigerants are there? N number of types like 1, 3, 4, 8, R 22, R 7, 1, 7. So depending upon their thermodynamic properties the COP may increase or decrease. So it is found for most of the refrigerants the COP increases. So by using simple device this heat exchanger we can manufacture it by fabrication methods take a simple sheet, make a enclosure, in that enclosure just to put either single tube which is flowing without opening to the heat exchanger another counter flowing pipe we can open it here means this low pressure low temperature refrigerant will come in direct contact with the counter flowing vapor refrigerant. So by placing this simple heat exchanger we will get improvement in the COP. For further study you can refer refrigeration and air conditioning by CP Aurora and WF Stoker. Thank you.