THERMAL EFFICIENCY OF COMPACT HEAT EXCHANGERS USING FINNED PIPES WITH INCLINED FINS

The thermal efficiency of two compact heat exchangers using finned pipes with inclined fins, 45° respect the axial axis, was obtained experimentally in the Thermal Hydraulics Applied Engineering Laboratory, the results are presented in this paper. The relationship between the fin diameter and the pipe diameter was D/d = 2. The pipes arrangements were in one row and square in two rows, with a total of ten pipes. The total area of heat exchangers was approximately 1 m². All necessary thermal parameters (inlet/outlet temperatures, mass flows, etc.) for the heat balance in the proposed heat exchangers were determined for different air velocities (Re = 4 10³ - 7 10⁴) and one constant thermal charge provided by a hot water flow of 1 1pm. As a result, a correlations for the heat transfer calculus of the type Nu = c Reⁿ were obtained. The experimental results were compared against the analytical results for a heat exchanger with straight conventional fins with equivalent area. We found out that the two compact heat exchangers using finned pipes with inclined fins are more efficient from 8% to 54%. Other interesting fact is that the proposed units are up to 29% more compact.