Abstract
It is desirable to know whether correlations for condensation in round tubes can be used for non-circular channels. To investigate this matter, a number of well-known correlations for mini and macro channels as well as some for flattened channels were compared to a database for condensation in non-circular channels. Data included square, rectangular, triangular, semi-circular, drum, N, and W shaped channels as well as flattened tubes. The data included 15 fluids, hydraulic diameter 0.067 to 1.46 mm, aspect ratio 0.14 to 7, reduced pressure 0.045 to 0.77, and mass flux from 48 to 1000 kgm−2s−1. None of the correlations worked well for flattened tubes. Data for all other shapes were best predicted by the Shah correlation with mean absolute deviation of 20.1% with 1120 data points from 22 sources. None of the other correlations was found satisfactory over the entire range.
Highlights
Mini channels are being widely used in heat exchangers including condensers because they offer several advantages including compact size, high heat transfer coefficients, and lower cost
Several correlations have been published which are stated to be applicable to circular as well as non-circular channels. These correlations use an equivalent diameter for application of non-circular channels; no other modification is made
The Shah correlation is recommended for all channel shapes except flattened tubes
Summary
Mini channels are being widely used in heat exchangers including condensers because they offer several advantages including compact size, high heat transfer coefficients, and lower cost. They reduce the amount of refrigerant in refrigeration systems and minimize environmental impact in case of leakage. Several correlations have been published which are stated to be applicable to circular as well as non-circular channels These correlations use an equivalent diameter for application of non-circular channels; no other modification is made. Notable examples of such correlations are Kim and Mudawar [1], Dorao and Fernandino [2], and Shah [3]. Several theoretical and experimental studies indicate that heat transfer in non-circular channels is higher than that in circular channels of the same equivalent diameter
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