heat transfer through fins

experimental work by fins

1. Presented to :- Prof K. M. Pandey Presented by :- PRASANT( 18-22-114) HEAT TRANSFER THROUGH FINS

2. C ontents Introduction working principle Method of increase heat transfer Type of design Type of fins straight fin annular fin trapazoidal fin Advantage Disadvantage Application Fin performance Result and discussion heat transfer performance Effect of flowrate Conclusion

3. Introduction Fins are generally used to enhance the heat transfer from a given surface Addition of fins can increase the heat transfer from the surface by several folds In many engineering situation, means are often sought to improve heat dissipation from a surface to its surrounding Whenever the available surface is found inadequate transfer the required quantity of heat with available temperature drop and convective heat transfer coefficient, extended surfaces or fins are used . By increasing the surface area in contact with air or providing fins By increasing the heat transfer coefficient the surface By increasing the temperature difference between hot and cold bodies

4. WORKING PRINCIPLE In many engineering application, large quantities of heat have to be dissipated from small areas. The fins increases the effective area of the surface thereby increasing the heat transfer by convection . In other words, the shape of fins must be optimized such that the heat transfer density is maximized when the space and the materials used for the finned surfaces are constraints.

5. METHODS TO INCREASE HEAT TRANSFER RATE By increasing the surface area in contact with air or providing fins. By increasing the heat transfer coefficient for the surface . By increasing the temp of the hot surface or by increasing the temperature difference between hot and cold bodies

6. TYPES BY DESIGN The fins are designed and manufactured in many shapes and forms. They manufactured in different geometries, depending upon the practical applications . The ribs attached along the length of a tubes are called longitudinal fins. The concentric annular disc around a tube are termed as circular or annular fins Pin fins or spines are rods protrading from a surface.

7. TYPES OF FINS

8. Straight Fins A straight fin is any extended surface that is attach to plane wall it may be uniform cross sectional area or its cross sectional area varies with the distance x from the wall

9. Annular Fins An annular fin is one that is circumferentially attached to the cylinder and its cross section varies with radius from the wall of the cylinder.

10. Trap e zoidal Fins Heat transfer by convection between a surface and the fluid surrounding can be increased by attaching to the surface thin metallic strips.

11. A D V AN T A G E S By using the fins, heat transfer rate can be increased without any preventive maintenance. It is the cheapest way for increasing the heat transferring rate from the hot bodies .

12. DISADVANTAGES We know that the length of fins is directly proportional to the heat transferring rate. But the larger length is may be cause of bending in the fins and also increases the weight of engine. Therefore the overall efficiency will goes to decrease . We know that the length of fins is directly proportional to the heat transferring rate. But the larger length is may be cause of bending in the fins

13. APPLICATIONS Common applications of finned surfaces are with c ooling of electronics components Condensers and economizers of thermal power plants Radiators for automobiles Dry type cooling towers Air cooled cylinders of compressors, IC engines Evaporators and condensers of refrigeration and air conditioning system. Electric motor and transformers

14. Fin performance can be described in three different ways. 1:- The first is fin effectiveness. It is the ratio of the fin heat transfer rate to the heat transfer rate of the object if it had no fin. The formula for this is where is the fin cross- sectional area at the base 2:- Fin performance can also be characterized by fin efficiency. This is the ratio of the fin heat transfer rate to the heat transfer rate of the fin if the entire fin were at the base temperature. in this equation is equal to the surface area of the fin Fin efficiency will always be less than one

15. 3:- The third way fin performance can be described is with overall surface efficiency. is the total area and is the sum of the heat transfer rates of all where the fins.

16. comparison of the different types of extended surfaces using heat transfer/pressure drop as the figure of merit.

17. S hows that, from a purely size standpoint, pin fins offer the smallest design for the best heat transfer while straight fins are the most inefficient from a heat transfer and smallest size constraint.

18. Results and Discussion Heat Transfer Performance The heat transfer performance of the heat exchanger was evaluated in terms of dimensionless parameter Nusselt number. The main purpose was to test the effects of geometric (tube arrangement , fin shape and tube inclination angle) and flow parameters on the heat transfer performance of compact flat tube-and-fin heat exchanger.

19. Effects of flowrate S hows variation of Nusselt number for plain fins against Reynolds number for inline configuration. The presented result shows that as the flow rate increases so does the Nusselt number. Moreover, it shows that the Nusselt number is directly proportional to the flowrate . This means the increase in the air velocity yields increment in the convection heat transfer of the heat exchanger. Results with similar trend has been seen from the simulation work The increasing trend is seen due to the better mixing of flow.

20. Conclusion From this study, it was found that the rectangular fin has the highest heat transfer performance compared to wavy and plain fin where wavy fin is higher than plain fin. Rectangular fin produces the highest heat transfer performances due to the interruption done by the staggered surfaces to the flow and temperature boundary layers along the flow orientation. The hydraulic performance has the similar trend where rectangular has the highest pressure drop compared to wavy and plain fin. This is due the interruption that wavy and rectangular fin geometry does to the flow of air. The pressure drop of plain fin is low compared to complex design of wavy and rectangular fin. Wavy and rectangular fin despite having higher heat transfer performance, they have a greater drawback in higher pressure drop. On the other hand, rectangular fin is suited for any application which prioritises thermal performance over hydraulic performance or efficiency.

21. THANK YOU