The special fluid flow and heat transfer characteristics of supercritical CO_2 in a horizontal double-pipe heat exchanger have been numerically investigated. The AKN k-epsilon model was selected to model the turbulent flow and heat transfer of supercritical fluid. In conjugate heat transfer process, there exists obvious heat transfer deterioration on the top wall for horizontal flow. The region of heat transfer deterioration expands with the increased G_(shell) or T_(shell.0,) and the influence of on conjugate heat transfer is greater than that of G_(Shell). The high-temperature fluid will gather near the top region. The intensity and position of the secondary flow can represent the turbulence heat transfer. When the supercritical fluid temperature is much higher than T_(pc), buoyancy force can be omitted, but it can not been neglected even under relatively high mass flux.
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