Therefore the overall efficiency will go to decrease. But the larger length is may be cause of bending in the fins and also increases the weight of the engine. We know that the length of the fins is directly proportional to the heat-transferring rate. It is the cheapest way for increasing the heat transferring rate from the hot bodies. By using the fins, the heat transfer rate can be increased without any preventive maintenance.It is okay to apply fins on both surfaces of pipes or tubes when HTC of fluid on the inner and the outer surface is comparable in magnitude. HTC of the fluid inside the cylinder is higher than the HTC of fluid on the outer surface of the cylinder.There is no increase in the surface area from which heat will be transferred to the surrounding.What would be the use of fins inside the cylinders? They simply won’t help to cool down the engine as So, there is a need of fins on the outer surface of the cylinder as you have to transfer heat energy from the engine to the surrounding (else the engine will wear out quickly). Which means 60% of energy is being dissipated to the surrounding. Now, efficiency for internal combustion engines of on-road vehicles is less than 40%. The temperature difference between the fin(s) and the fluid to which they are exposed.Įffectiveness and efficiency depend on the medium in which fins are being used.Heat transfer coefficient (HTC) of fluid to which they are exposed,.Convective heat transfer can be expressed as the product of the following, Heat transfer through a fin occurs through convective heat transfer. Fins are not provided on the inner surface of the cylinder : The desire is to have this ration as large as possible while keeping the additional cost of adding the fins as low as possible. In other words, this quantity tells us how much extra heat is being transferred by the fin. This ratio will always be smaller than one fin efficiency Equation Fin effectivenessįin effectiveness is the ratio of heat transfer from the fin to the heat transfer if the fin wasn’t existing. Therefore, adding too many fins on a surface may actually decrease the overall heat transfer when the decrease in h offsets any gain resulting from the increase in the surface area.įin efficiency is the ratio of heat transfer from the actual fin to the heat transfer of an imaginary fin of the same geometry and same conditions but with an infinite conductivity (In other words, if the entire fin surface was in a temperature equal to that of the fin base).The value of h is usually much lower at the fin base than it is at the fin tip because the fluid is surrounded by solid surfaces near the base, which seriously disrupt its motion to the point of “suffocating” it, while the fluid near the fin tip has little contact with a solid surface and thus encounters little resistance to flow.We recognize that the convection heat transfer coefficient h, in general, varies along the fin as well as its circumference, and its value at a point is a strong function of the fluid motion at that point.We also assume the convection heat transfer coefficient h to be constant and uniform over the entire surface of the fin for convenience in the analysis.In the analysis of fins, we consider steady operation with no heat generation in the fin, and we assume the thermal conductivity k of the material to remain constant.Hence the fins have practical importance because it gives maximum heat flow per unit mass with ease of manufacture. Triangular fins are attractive, since for an equal heat transfer it requires much less volume than rectangular fins. Rectangular fin and triangular fins are straight fins. The fins increase the effective area of a surface thereby increasing the heat transfer by convection. ![]() ![]() In many engineering applications large quantities of heat needed to be dissipated from small areas. ![]() The heat-conducting through solids, walls, or boundaries has to be continuously dissipated to the surroundings or environment to maintain the system in a steady-state condition.Heat transfer by convection between a surface and the fluid surrounding can be increased by attaching to the surface called fins.Fins are the extended surfaces designed to Increase heat transfer rate for a fixed surface temperature, or lower surface temperature for a fixed heat transfer rate.Fins are not provided on the inner surface of the cylinder :.
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