Flow and Heat Transfer Characteristics in a Seven Tube-Bundle Wrapped with Helical Wires

Local flow and heat transfer characteristics in a seven tube bundle helically wrapped with wires of circular cross section are obtained computationally and presented. Regions of sweeping and mixing flows and hot spots are identified from the local characteristics. Parametric investigations with varying outer diameter ratio (D/d = 3.93, 4.24 and 4.54), helical pitch ratio (P/d = 9.09, 18.18 and 30.30) and triangular pitch ratio (Pt/d = 1.28, 1.32 and 1.36) are presented for a Reynolds number range of 8,000 to 100,000. The average friction factors and Nusselt numbers show highest values for D/d = 3.93, P/d= 9.09 and Pt/d =1.36. The variation of thermal hydraulic performance ratio against the mass flow rate provides an optimum geometry for the design of heat exchanger with seven tube bundle.