 Hello students, myself Ganesh Biyaglavi working as an assistant professor in department of Mechanical Engineering, Valchin Institute of Technology, Sallapur. In this session, we will see fins that is extended surfaces. In part first, its introduction and types. Finning outcome. At the end of this session, students will be able to explain need of fins and classification that is the types of fins. Here, we will see first introduction of fins and types of fins. Now, what is fins? So, in heat transfer, as we know, we required to enhance the heat from either the surface to the fluid or vice versa. So, what is done? If this is the plane surface, which has temperature T s, surrounding temperature T infinity. Suppose this surface has area A. Now, the transfer of heat from surface to surrounding will occur when T s is greater than T infinity. Now, this mode of heat transfer is the convective mode, which will follow the equation Q is equal to H A delta T means T s minus T infinity. Now, as we know, to enhance this heat transfer rate, convective heat transfer rate, either we required to increase the H or increase the T s or T infinity. Now, in the convective heat transfer, there are limitations for increasing the H. Now, H means convective heat transfer coefficient, which depends upon the free convection and forced convection. Up to certain extent, by increasing the velocity of a fluid, velocity of the fluid will get maximum H, when that there is need to search for the alternative of enhanced heat transfer. So, this has some limitation. Second option to make this maximum is to increase the T s. As we know, the T s that is a surface will have the same temperature, isothermal temperature, which is not in our hand. It depends upon the application. For example, in the condenser, the condenser pressure is constant means the tube which is used for the condenser will have the constant temperature. So, this also we cannot change that is increased. Third option is surrounding fluid temperature. Surrounding temperature, once again we cannot change, we cannot increase the atmospheric temperature. It changes from time to time. So, this is the unsteady state temperature of the atmosphere. Now, increase in Q is possible only if we will increase the surface area. So, now, it is fixed that Q can be increased by changing the surface area. Now, how to increase the surface area? So, what we will do? We will start soldering such type of surfaces. So, you can call this as the extension, extension of surface. Suppose, this is the base plate, this is the base on this base plate. We have increased the surface of this base plate by either casting this extended surface as the integral part of the base surface. So, this surface area has been increased by 1, 2, 3. Back side will be 4. This side will be 5 sides. This extended surface is known as fin. So, it is clear now that the extended surface increases the surface area and we will get the enhanced heat transfer. Such surfaces are known as fins. Now, applications as just now we have seen for the heat exchanger fins are used like condenser, second EO operator, third radiator and so on. For the domestic refrigerator also on the back side, the condenser tubes are there. These are the copper condenser tubes. Suppose, this is the inlet, this is the outlet. How to increase the surface area? So, small diameter wires are attached to these tubes. These are also called fins. So, these are few applications. We can consider second application as heat sink used in the CPU, in the CPU processor needs to be cooled. So, suppose this is the processor chip, on this processor chip vertical such type of rectangular fins are attached. With these few examples, we will move to the application of fins. We will see different types of fins. First one is rectangular fin. For the study of the fins, we will consider this vertical surface as the base surface. If I put such type of rectangle in isometric sketch, such type of plate whose cross section is rectangle is attached to this base surface whose temperature is T naught is known as rectangular type of the fin. Now, you can increase the number of fins. Suppose this is the one, then here you can put a second and so on. In second type of the fin that is a trapezoidal trapezoidal type fin, on this base surface instead of rectangular cross section, we can connect the trapezoidal fin. In the third type of the fin that is helical fin, suppose there is a cylinder which needs to increase the heat transfer, then like these helical plates, we can connect to the base surface. So, here this is the base surface whose temperature is T s. These are the helical fins. In the fourth type circumferential fins, suppose this is the cylinder, you will find this application in the cold storage EO operator, where on this EO operator tube through which the refrigerant is flowing which has low temperature, the difference between the discs, such type of discs are connected. So, the cooling rate gets enhanced. In the fifth type of the fin, we are calling it as a longitudinal fin. On this cylindrical surface, longitudinal fins are connected. These are the longitudinal fins. So, we can occupy the complete circumference of the cylinder. So, these are the types of the fins. For further study, you can refer the fundamentals of heat and mass transfer by Frank in Kropera and David Wille publication. Thank you.