Experiments on elliptic sections in one- and two-row arrangements of plate fin and tube heat exchangers

Abstract

Abstract In order to determine average transfer coefficients for plate fin and elliptic tube exchangers, mass transfer experiments were performed using the naphthalene sublimation technique. By means of the heat and mass transfer analogy, the average coefficients of mass transfer can be easily converted to heat transfer results. In accordance with the analogy, the experimental conditions, with naphthalene plates forming the rectangular channel of the exchanger, simulated isothermal fins. Since in practical situations the fins are not isothermal, one can rationalize such a fact by using the concept of fin efficiency, which is a common procedure in heat transfer calculations. The transfer coefficients of the present research were compared with those for circular tube exchangers, found in the pertinent literature, and the comparison revealed no major differences. This is a positive outcome, since the use of elliptic tubes, as it will be shown, reduces substantially the pressure drop in the rectangular channel and increases the fin efficiency improving the transfer characteristics. The mass transfer measurements were performed by weighing the naphthalene pieces before and after a data run characterized by the flow Reynolds number. The Reynolds number range was 150–1300. The present results are directly applicable to air conditioning devices.