ISSN Online: 2377-424X
ISBN Print: 978-1-56700-421-2
International Heat Transfer Conference 15
Measurements of Heat Transfer Coefficients to Cylinders in Shallow Bubble Columns
Abstract
High heat transfer coefficients and large interfacial areas make bubble columns ideal for dehumidification.
However, the effect of geometry on the heat transfer coefficients outside cooling coils in shallow bubble
columns, such as those used in multi-stage bubble column dehumidifiers, is poorly understood. The generally-overlooked entry and coalescing regions become important in shallow bubble columns, and there is disagreement
on the effects of the coil and column diameters. In this paper, a method is presented for measuring the
heat transfer coefficient between coil and liquid in a shallow bubble column. Horizontal cylindrical probes are
used to measure the heat transfer coefficient over a range of velocities. The liquid depth and the diameter,
height, and horizontal position of the cylinder are also varied. Existing correlations for tall columns tend
to underpredict the heat transfer coefficient and do not account for all effects of geometry. The highest heat
transfer coefficients (above 8000 W/m2−K) are recorded on cylinders placed 4 cm high. No significant effect of cylinder diameter is observed. Based on the results, recommendations are made regarding bubble column
dehumidifier design.