Local and Average Transfer Coefficients for Developing Laminar Flow Between Parallel Flat Plates

Abstract

Local and average mass transfer coefficients in the entrance region between parallel flat plates were experimentally determined. The mass transfer experiments were performed using the naphthalene sublimation technique. In accordance with the analogy between heat and mass transfer, the experimental conditions simulated the heat transfer situation characterized by laminar flow in a parallel plate channel, one wall being isothermal and the other insulated, The temperature and velocity fields were simultaneously developing. Results were obtained for Reynolds numbers from 100 to 1500 and plate length-to-equivalent diameter ratios from 5 to 20. By use of the reciprocal of the Graetz number as an independent variable, the data for the various test runs could be brought together. The experimental results were compared with analytical predictions and a very good agreement was observed. Overall mass transfer results were measured with a precision balance and compared with the integral local values; the two methods gave results that agree to within a few percent (typically 2%).