Abstract:

The flow and heat-transfer characteristics of a new type of heat-transfer enhancement element , namely , the twisted tape as the tube bundle support , are analyzed. A shell-side periodic unit channel model is developed to conduct the numerical simulation and experimental investigation of the heat transfer enhanced with smooth tube bun-dle supports. The RNG κ-ε two-equation turbulent model is then adopted to simulate the fluid and temperature fields in a unit channel. In the simulation , the SIMPLEC algorithm is used to solve the coupling between the pre-ssure and the velocity , and an enhanced wall treatment is employed to solve the near-wall flow and heat transfer. Moreover , the integrated thermal performances of both the ring and the twisted-tape supports are compared. The re-sults demonstrate that (1) the twisted tape produces a helical flow , which results in the disruption of the continuous and stable fluid and enhances the heat transfer effectively , (2) the two types of twisted-tape supports have better heat-transfer enhancement and more pressure drop than the ring support , (3) the integrated thermal performance of the ring support is stronger than those of the twisted tapes with small twist ratio because the latter have a higher forrn-pressure drop , and (4) the structural parameters of twisted tapes show crucial influence on their thermal per-forrnance.

Key words: heat exchanger, twisted tape, heat-transfer enhancement, numerical simulation, pressure drop