RÉSUMÉ

The contribution deals with a model of passive buoyancy-dominated heat exchanger aimed at subsea processing of natural produced. The 3D unsteady buoyancy-induced water flow through a staggered tube bank at the Grashof number of 3×10⁵ is simulated using the full Navier-Stokes equations with no turbulence model. Direct numerical simulation of the external draft flow is combined with the simultaneous unsteady RANS modelling of the internal natural flow in plain serpentine pipes at Re = 8×10⁵ and simulation of heat conduction through the massive steel pipe wall. The paper compares water flow and external heat transfer characteristics for two cross-flow cooler configurations with the downward and upward internal flow that correspond to the counter-flow and the parallel-flow heat exchanger schemes. It was found that though there is a pronounced difference in the local characteristics, in general the gas flow direction does not influence the cooler effectiveness: the total heat output values for both the schemes considered are almost the same. The cooler performance does not depend on the inlet and outlet collector location that gives some freedom in cooler design.