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Information Seminar Paper

Title

ROUGHNESS EFFECTS ON NUCLEATE POOL BOILING OF WATER ON HORIZONTAL STAINLESS STEEL CYLINDER

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Abstract

 NUCLEATE BOILING HEAT TRANSFER (NBHT) HAS BEEN CONSIDERED AN EFFECTIVE WAY TO REMOVE THE HIGHER HEAT FLUX AT A GIVEN TEMPERATURE DIFFERENCE COMPARED WITH A SINGLE PHASE HEAT TRANSFER.THE PRESENT STUDY IS AN EXPERIMENTAL INVESTIGATION OF ROUGHNESS EFFECTS ON NUCLEATE POOL BOILING OF WATER ON HORIZONTAL STAINLESS STEEL CYLINDER. THE CYLINDERS WERE TREATED BY DIFFERENT SAND PAPER GRIT SIZES TO ACHIEVE DIFFERENT SURFACE ROUGHNESS. THE AVERAGE SURFACE ROUGHNESS OF THE SEX SAMPLES WAS 0.98, 0.81, 0.65, 0.48, 0.24 AND 0.08 MM, RESPECTIVELY. THE EXPERIMENTS WERE PERFORMED IN THE HEAT FLUX RANGE OF 5 TO 110 KWM-2. THE HEAT TRANSFER COEFFICIENT WAS CALCULATED BY MEASURING WALL SUPERHEAT OF THE SAMPLES AND THE INPUT HEAT FLUX. THE RESULTS SHOW SIGNIFICANT IMPROVEMENT OF HEAT TRANSFER COEFFICIENT AS THE SURFACE ROUGHNESS IS INCREASED. THE EXPERIMENTAL DATA SHOW THAT BUBBLE DEPARTURE FREQUENCY AND NUCLEATION SITE DENSITY INCREASE AND BUBBLE DEPARTURE DIAMETER DECREASES WITH INCREASING THE SURFACE ROUGHNESS. A NEW MODEL FOR THE PREDICTION OF HEAT TRANSFER COEFFICIENT IS PROPOSED, WHICH PREDICTS THE EXPERIMENTAL DATA WITH A SATISFACTORY ACCURACY.

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