ISSN:0145-7632    

DOI:10.1080/01457639308939807

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Local heat transfer and pressure drop were measured from the corrugated portion of the bottom wall of a rectangular channel where the opposite top wall took one of the three following constructions: (1) plane; (2) couered with corrugations making an in-phase arrangement with the bottom wall; (3) couered with corrugations making an out-of-phase arrangement with the bottom wall. There were a total of seven corrugations, and the corrugation geometry was sinusoidal. Measurements were performed for three different aspect ratios (corrugation height / channel height), and Reynolds numbers ranged from 22,000 to 52,000 in the turbulent region. Heated-coating liquid crystal technique was used for temperature measurements. The highest local Nusselt number was detected on the second corrugation regardless of Reynolds number, aspect ratio, or geometry. Higher Reynolds numbers and higher aspect ratios had similar effects, increasing local heal transfer coefficient. At the higher Reynolds numbers and with higher aspect ratios, two local minima were detected for the Nusselt numbers on each corrugation. Heat transfer results turned out almost the same whether the channel was couered with in-phase or out-of-phase corrugations; pressure drop was higher for the out-of-phase arrangements.

ISSN:0145-7632    

DOI:10.1080/01457639308939808

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This article describes experimental study and calculation on steam condensation heat transfer and pressure drop in a plate condenser. Based on the results, it presents a formula expressing the relation of condensation heat transfer and having obuious physical meaning. Several important points affecting steam condensation heat transfer in plate condensers are analyzed. The Lockhart-Martinelli model is extended to two-phase nonadiabatic flow for calculation of frictional pressure drop in plate condensers.

ISSN:0145-7632    

DOI:10.1080/01457639308939809

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Current practice in the ammonia industry is to use plain tubes. This article demonstrates that the coefficient of performance (COP) can be increased by about 11% using tubes with ammonia-side enhancement and by about 26% using tubes with ammonia-side and water-side enhancement. Further improvements with respect to energy and cost are possible with the compact heat exchanger types—plate-frame and plate-fin—because they can be optimized for the system conditions for each application. These findings are based on experimentally determined overall heat transfer coefficients that were obtained for candidate heat exchangers for the Ocean Thermal Energy Conversion (OTEC) program.

ISSN:0145-7632    

DOI:10.1080/01457639308939810

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This article presents river-water fouling rates at 12 Tennessee Valley Authority (TVA) power plant condensers, nine of which were retubed with a commercially available enhanced tube. Four were located on the Cumberland River, six on the Ohio, and two on the Clinch River. The overall heat transfer coefficients were calculated from logged field data taken over periods extending from 1 to 10 years. The fouling resistances were next calculated with the separate resistance method and with a bundle correction factor to the condensing, single-tube Nusselt prediction. The bundle correction factor was determined for each condenser using the data taken within 1000 hours after each cleaning. With the use of this new bundle factor method, fouling rate data can be obtained even with variable operating conditions.

ISSN:0145-7632    

DOI:10.1080/01457639308939811

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This wet suit material testing program provides a quantitative thermal conductivity and heat transfer analysis, and comparison of various materials used in skin diving and SCUBA diving. Thermal resistance represents the primary subject examined, but due to compressibility of the baseline materials and its effect on heat transfer, this program also examines compression at simulated depth. This article reports the empirical heat transfer coefficients for both thermal conductivity and convection. Due to the limitations of the test apparatus, this analysis must restrict the convection evaluation to an approximately 20-cm-height, free-convection model. As a consequence, this model best simulates the overall heat transfer coefficient of a diver hovering in a horizontal position. This program also includes evaluations of some nonstandard materials in an effort to identify alternative wet suit materials.

ISSN:0145-7632    

DOI:10.1080/01457639308939812

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor