We examined the air flow distribution through a residential indoor air conditioning heat exchanger. The test heat exchanger was a finned tube, A-shaped coil outfitted with a condensation collection pan required for a horizontal installation configuration. We examined the air flow distribution approaching and exiting the coil at two different air flow rates and two humidity levels. Our dry coil PIV measurements indicate that the presence of the condensation collection pan impedes air flow through the lower slab of the coil causing approximately 20 % more air flow through the upper slab than the lower slab. Also, the measurements uncovered some portions of the coil where the flow is blocked by the mounting brackets. The wet coil tests showed that the presence of water on the surface of the coil causes a large increase in the resistance to air flow through the coil, but the water concentration was not uniformly dispersed throughout the coil. The air flow distribution was not largely affected by the overall flow rate of air, except in the wet coil tests where the water concentration on the coil changed with air velocity. We also developed a CFD model of the flow through the test coil, based on a momentum resistance modeling approach. For the cases studied, the CFD results matched approximately 90 % of the measured data within 15 % for the upper slab and 20 % for the lower slab of the coil.
Citation: Technical Note (NIST TN) - 1651Report Number:
NIST Pub Series: Technical Note (NIST TN)
Pub Type: NIST Pubs
Air Flow Distribution, Residential Air Conditioning Coil, Particle Image Velocimetry (PIV), Computational Fluid Dynamics (CFD)