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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

Critical heat flux of R134a boiling flow in the circumferentially non-uniformly heated helically coiled tubes

Get access (open in a dialog) DOI: 10.1615/IHTC16.mpf.024352
pages 6601-6615

Abstract

The critical heat flux (CHF) characteristics of R134a boiling flow in helically coiled tubes under circumferentially uniform and non-uniform heating conditions were experimentally investigated in this paper. The experiments were performed with three helically coiled tubes made of stainless steel tubes (SUS304) with inner diameters of 8 mm. The rations between the maximum and the average heat flux (qmax/qavg) were 1.0, 1.2 and 1.4 respectively. The inlet system pressures ranges from 0.8 to 1.1 MPa, mass flux from 190 to 400 kg/(m2·s), and heat flux from 15 to 55 kW/m2. The wall temperature distributions were measured in the axial and circumferential directions. The effect of inlet quality and mass flux on CHF in helically coiled tubes under uniform and non-uniform heating conditions was investigated. The results show that the average CHF decreased with the increasing of inlet quality both in uniform and non-uniform heating conditions. However, the influence of the mass flux on the average CHF in the non-uniformly heated tubes was different from that in the uniformly heated tubes, which was mainly attributed to the change of temperature distribution by the non-uniform heating method, and thus changed the peritubular location of the dryout taking place. In addition, the circumferential maximum CHF was higher than that in the uniformly heated tubes. The average CHF in the non-uniformly heated tubes was higher than that in the uniformly heated tubes when the mass flux was lower than 220 kg/(m2·s). On the contrary, the average CHF was lower in the non-uniformly heated tubes when the mass flux was higher than 280 kg/(m2·s).