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International Heat Transfer Conference 12

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Compound heat transfer enhancement by a combination of spirally corrugated tubes with a twisted tape

Ventsislav D. Zimparov
Gabrovo Technical University, 4 Hadji Dimitar Strasse, 5300 Gabrovo, Bulgaria

Valentin Metodiev Petkov
Gabrovo Technical University, 4, Hadji Dimitar, Str. 5300 Gabrovo, Bulgaria

DOI: 10.1615/IHTC12.5230
6 pages

Abstrakt

Heat transfer and isothermal friction pressure drop results have been obtained experimentally for two three - start and one single-start spirally corrugated tubes combined with five twisted-tape inserts with different relative pitches in the range of Reynolds number 4×103 - 6×104. The characteristic parameters of the tubes are: height-to-diameter ratio, e/Di = 0.0375 , 0.0434 and 0.0414; and pitch-to-hight of corrugation ratio p/e = 8.97, 8.74 and 8.70. The relative pitches of the twisted tapes are: H/Di = 7.7, 6.25, 3.95, 2.95, 2.4. Significantly higher friction factor and inside heat transfer coefficients than those of the smooth tube under the same operating conditions have been observed. Extended performance evaluation criteria (PEC) equations for enhanced heat transfer surfaces have been used to assess the multiplicative effect. Thermodynamic optimum can be defined by minimizing the entropy generation number compared with the relative increase of heat transfer rate or relative reduction of heat transfer area.

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