Heat transfer of 3-D printed enhanced tube and fin condenser surfaces
Choke, Chong Wai
Date of Issue2016-05-23
School of Mechanical and Aerospace Engineering
This project presents the heat transfer and hydraulic performances of tube and fin air-cooled condenser coils fabricated by Selective Laser Melting. Seven condenser coils with three different fin designs (plate fin, louvre fin and slit fin) and three different fin pitches (2.4 mm, 3.3 mm and 4.2 mm) were fabricated and a miniature wind tunnel was designed and constructed to perform experimental investigation on these condenser coils. The experimental results of various condenser coils were compared and the louvre fin condenser coil was determined to have the best heat transfer performance, with the enhancement in j factor (jH) of 34% as compared to the plate fin condenser of the same fin pitch. On the other hand, the slit fin condenser demonstrated 30.5% enhancement in heat transfer performance over the plate fin at the same fin pitch of 3.3 mm. For condenser coils of the same fin design, variation in fin pitches have also shown to affect the computed j factor. The heat transfer performance has an enhancement of 8.6% for plate fins of 2.4 mm compared to 3.3 mm fin pitch and 18.4% enhancement for slit fin of 3.3 mm compared to 4.2 mm fin pitch. Heat transfer performance is shown to increase with decreasing fin pitch. However, a different trend exists where there is a 15% enhancement for 3.3 mm fin pitch louvre fin compared to 2.4 mm fin pitch and 16% increase when 4.2 mm fin pitch is compared to the 3.3 mm fin pitch. Pressure measurements across the condenser coils at different air flow velocities were taken and the percentage in the pressure difference between the condenser coil of the same fin design but different fin pitches at the same air flow (α) were computed. For plate fins, α for the 2.4 mm fin pitch as compared to 3.3 mm fin pitch reduced from 26% to 14% as velocity increases. On the other hand, when comparing the slit fins with fin pitch of 3.3 mm to the slit fins with fin pitch of 4.2 mm, α reduced from 135% to 115% as velocity. This trend shows that α typically decreases as velocity increases. For the same fin pitch and different enhancements, α increases from 0 to 48% for louvre compared to plate and 280% to 351% increase for slit compared to plate fin condenser of 3.3 mm fin pitch. Pressure drop increase (α) is compared with heat transfer performance in order to find the best performing condenser. For the same pressure drop of 300 Pa for the 3.3 mm fin pitch condensers, there is an increase of 16% heat transfer for the slit fin condenser and 84% enhancement for the louvre fin condenser. Pressure drop must be finely tuned with j factor increase to find the best performing condenser which is 4.2 mm louvre fin condenser.
Final Year Project (FYP)
Nanyang Technological University