EXPERIMENTAL INVESTIGATIONS OF THE EFFECTS OF TUBE BUNDLES ON BOILING HEAT TRANSFER. (1ST REPORT, EXPERIMENTAL RESULTS).

For tube bundles of flooded evaporators, boiling heat transfer coefficients are improved by upward streaming vapor bubbles. The authors try to clarify the relations between boiling heat transfer characteristics of single tubes and those of tube bundles. In this report, boiling heat transfer characteristics of low-finned-tubes are investigated, using bundles of 4 horizontal tubes in a vertical row with side walls. Experimental results are summarized as follows: (1) when the clearance between tube and side wall is larger than 5 left bracket mm right bracket , the effects of side walls on boiling heat transfer of tube bundles cannot be recognized; (2) bundle effects are affected both by the heat flux of the tube itself and by the total heat flux of the lower tubes; (3) the heat flux increase by upward streaming vapor bubbles has maximum value at wall superheat 5 left bracket K right bracket for 15 approx. 90 left bracket kW/m**2 right bracket of total heat flux of the lower tubes. Author abstract)