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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. Fin performance can also be characterized by fin efficiency.
The fin material should preferably have high thermal conductivity. In most applications the fin is surrounded by a fluid in motion, [ 1 ] which heats or cools it quickly due to the large surface area, and subsequently the heat gets transferred to or from the body quickly due to the high thermal conductivity of the fin.
The number of transfer units (NTU) method is used to calculate the rate of heat transfer in heat exchangers (especially parallel flow, counter current, and cross-flow exchangers) when there is insufficient information to calculate the log mean temperature difference (LMTD). Alternatively, this method is useful for determining the expected heat ...
As heat flows through the fin, the combination of the thermal resistance of the heat sink impeding the flow and the heat lost due to convection, the temperature of the fin and, therefore, the heat transfer to the fluid, will decrease from the base to the end of the fin. Fin efficiency is defined as the actual heat transferred by the fin ...
In thermal engineering, an annular fin is a specific type of fin used in heat transfer that varies, radially, in cross-sectional area. Adding an annular fin to an object increases the amount of surface area in contact with the surrounding fluid, which increases the convective heat transfer between the object and surrounding fluid.
The Biot number is defined as: = where: is the thermal conductivity of the body [W/(m·K)]; is a convective heat transfer coefficient [W/(m 2 ·K)]; is a characteristic length [m] of the geometry considered.
For a heat engine, thermal efficiency is the ratio of the net work output to the heat input; in the case of a heat pump, thermal efficiency (known as the coefficient of performance or COP) is the ratio of net heat output (for heating), or the net heat removed (for cooling) to the energy input (external work). The efficiency of a heat engine is ...
Published experiments on MicroGroove coil performance and energy efficiency take into account the effects of fin spacing and fin design, tube diameter, and tube circuitry. [17] Tube circuitry is substantially different than for conventional coils. Coils should be optimized with respect to the number of paths between the inlet and outlet manifolds.