Heat transfer enhancement during downward laminar flow condensation of R134a in vertical smooth and microfin tubes

บทความในวารสาร

ผู้เขียน/บรรณาธิการ

กลุ่มสาขาการวิจัยเชิงกลยุทธ์

ไม่พบข้อมูลที่เกี่ยวข้อง

รายละเอียดสำหรับงานพิมพ์

รายชื่อผู้แต่ง: Dalkili็ A.S., Teke I., Wongwises S.

ปีที่เผยแพร่ (ค.ศ.): 2012

Volume number: 32

Issue number: 1

หน้าแรก: 19

หน้าสุดท้าย: 31

จำนวนหน้า: 13

นอก: 1300-3615

eISSN: 1300-3615

URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-84880209550&partnerID=40&md5=1901b40f8c36d0aab2b84b0096bdf302

ภาษา: English-Great Britain (EN-GB)

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บทคัดย่อ

This paper presents an experimental comparison of the laminar film condensation heat transfer coefficients of R134a in vertical smooth and micro-fin tubes having inner diameters of 7 mm and lengths of 500 mm. Condensation experiments were performed at a mass flux of 29 kg m-2 s-1. The pressures were between 0.8 and 0.9 MPa. The original smooth tube heat transfer model was modified by a well-known friction factor to account for the heat transfer enhancement effects due to the presence of micro-fins on the internal wall surface during annular flow regime conditions. Alterations of the local heat transfer coefficient, and condensation rate along the tube length during downward condensing film were determined, considering the effects of the temperature difference between the saturation temperature and the inner wall temperature of the test tubes, and the condensing temperature on these items. The results show that the interfacial shear stress is found to have significance for the laminar condensation heat transfer of R134a under the given conditions due to its better predictive performance than the classical solution neglecting the interfacial shear stress effect. A comparison of the condensation heat transfer coefficients was also done according to the condensing pressures. New empirical correlations of the condensation heat transfer coefficient belonging to the test tubes are proposed for practical applications. ฉ 2012 TIIBTD Prriintted iin Turrkey.

คำสำคัญ

Annular flow, Nusselt theory