HEAT-TRANSFER AND PRESSURE-DROP OF SPINED PIPE IN CROSS FLOW .2. HEAT-TRANSFER STUDIES

Hot water at a temperature of about 120F (49C) circulated through a single row of aluminum (type 2024) spined pipe and transferred heat to room-temperature air in cross flow. Heat transfer was measured by performing an energy balance on the flowing water. Two sizes of spined pipe were studied, each at three different spacings. The 1/4 -in. (6.35 mm) nominal diameter pipe was spaced 1.50, 1.13, and 0.791 in. (38.1, 28.6, and 20.1 mm) and the 1/8-in. (3.18 mm) nominal diameter pipe was spaced 0.897, 0.642, and 0.542 in. (22.8, 16.3, and 13.3 mm) apart. To ensure that water flow was always turbulent, a spring was inserted in the pipe. This turbulence inducer increased the inside heat transfer coefficient by 3.6 times compared to a bare interior. A power law containing the Nusselt, Reynolds, and Prandtl numbers was used to correlate both the inside and outside heat transfer coefficients. The model of the air-side heat transfer includes spine efficiencies, which were generally above 70%. The agreement between the model and the data is within 3% in all cases. The model may be extended to the two-phase heat transfer commonly encountered in air conditioning and refrigeration by using an appropriate two-phase correlation for the inside heat transfer coefficient.

HEAT-TRANSFER AND PRESSURE-DROP OF SPINED PIPE IN CROSS FLOW .2. HEAT-TRANSFER STUDIES Conference Paper