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ISSN Печать: 1065-5131
ISSN Онлайн: 1563-5074
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In-Tube Evaporation of HCFC-22 with Enhanced Tubes
Краткое описание
The purpose of this study is to present highly accurate, comprehensive in-tube evaporation data on several commercially available internally enhanced tubes. Data is presented for the two most popular sizes for use by designers of high-efficiency heat-exchange equipment. The experiments were performed over a wide heat-flux range to ensure that the data were applicable for many uses.
In support of this purpose, seven copper tubes were tested with pure HCFC-22 in a water to refrigerant counter-flow heat exchanger to determine their in-tube boiling characteristics and pressure drops at approximately ARI (Air-Conditioning and Refrigeration Institute, Arlington, Virginia, U.S.A.) conditions. Three 9.53 mm (0.375 inch) outside diameter tubes were tested: one with 60 internal ridges and a helix angle of 18°, one with 72 straight internal ridges (no helix), and one with a smooth internal surface. Four 15.88 mm (0.625 inch) outside diameter tubes were tested: one with 60 internal ridges, one with 75 internal ridges, one corrugated, and one with a smooth internal surface.
A typical rifled tube profile is shown in the micrograph of Figure 1. It consists of equally spaced fins that are typically characterized by their height, base width, and shape. Heat exchanger designers specify these tubes by outside diameter, ridge height, number of fins, helix angle, and bottom wall thickness, as defined in Figure 2. The dimensions of the 9.53 mm tubes are listed in Table 1. The dimensions of the 15.88 mm tubes are listed in Table 2.
The results indicated that the 9.53 mm tube with 60 ridges and an 18° helix angle and the 15.88 mm tube with 75 internal ridges and a 23° helix angle angle, (Turbo-A® and 75 ridge Turbo-DX® as manufactured by Wolverine Tube, Inc.), give the highest heat transfer enhancements for the respective tube sizes considered in this test program.
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