Nucleate pool boiling, film boiling and single-phase free convection at pressures up to the critical state. IB. Integral heat transfer from the outer surface of horizontal copper cylinders in single-phased free convection and comparison with nucleate and film boiling.

Ebullitión libre nucleada, ebullición pelicular y convección libre monofásica a presiones próximas al estado crítico. IB. Transmisión integral de calor de la superficie externa de cilindros horizontales de cobre a refrigerantes en convección libre monofásica y comparación con ebullición nucleada y pelicular.

Author(s) : GORENFLO D., BAUMHÖGGER E., WINDMANN T., et al.

Type of article: Article

Summary

Transcritical working cycles for refrigerants have led to increased interest in heat transfer near the critical state. In general, experimental results for this region differ significantly from those far from it because some fluid properties vary much more there than at a greater distance. In this paper, measurements for two-phase and single-phase free convective heat transfer from an electrically heated copper tube with 25 mm OD to refrigerant R125 are discussed for fluid states very close to the critical point and far from it. It is shown that heat transfer for film boiling slightly below and for free convection slightly above the critical pressure is very similar. The new, and also previous, experimental data for nucleate boiling, film boiling, and single-phase free convection are compared with calculated results between atmospheric and critical pressure. It can be concluded that the principle of corresponding states in its simplest form is very well suited to transfer the results to other refrigerants.

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Pages: 30-40 (9 p.)

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