Experimental Performance Evaluation of Multi-Row, Plate Finned-Tube, Direct Expansion Air Cooling and Dehumidifying Coils
Turaga, M.
1989
Thesis, Ph.D. (Building), Centre for Building Studies, Concordia University, Supervisors: P. Fazio, S.Lin
Turaga, M., (1989), Experimental Performance Evaluation of Multi-Row, Plate Finned-Tube, Direct Expansion Air Cooling and Dehumidifying Coils, Thesis, Ph.D. (Building), Centre for Building Studies, Concordia University, Supervisors: P. Fazio, S.Lin.
| Abstract: |
| Experimental studies are conducted on Plate finned-tube, Direct-Expansion (DX), air cooling and dehumidifying heat exchangers to determine the effects of significant coil geometric parameters and the fluid flow parameters on the coil performance. Tests are conducted on ten (10) coils with varied fin densities (3.1 to 5.5 fins/cm) and tube rows (3 to 8) under both dry and wet surface conditions for the air-side. Such studies, on the performance of DX-coils for comfort air conditioning applications, are very limited in the open literature. Correlations for the average heat transfer and pressure drop factors for the working fluids (air and refrigerant) are developed from the experimental data; such correlations for refrigerant in DX-coils are very limited in the present literature. Regression analysis is used to determine the influential coil geometric parameters on the heat exchanger performance. In the range of the air flow Reynolds number considered (300 $<$ Re$/sb[/rm a]$ $<$ 1500), the air-side average heat transfer and pressure drop factors (for both dry and wet surface conditions) are found to be independent of the number of tube rows and decrease when the fin density increases (for a given Reynolds number). The refrigerant-side average Nusselt number (Nu$/sb[/rm r]$) is found to be an increasing linear function of the two-phase heat transfer parameter $/rm (Re/sbsp [r,l][2]/ K/sb[f])$ and the corresponding pressure drop factor (f$/sb[/rm r]$) is found to be decreasing linear function of the two-phase pressure drop parameter $/rm (Re/sb[r,l]/K/sb[f])$. The presence of oil (about 2% by weight), is found to increase both the average Nusselt number (by 30 to 40%) and the average pressure drop factor (by 25%), compared to the corresponding oil free flow. A method for selection of DX-coils is developed from the correlations for prediction of the average heat transfer and pressure drop factors. This selection method may be used for estimation of the part-load performance of DX-coils. |
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