Refrigerant forced-convection condensation inside horizontal tubes

High vapor velocity condensation inside a tube was studied theoretically. The heat transfer coefficients were calculated by the momentum and heat transfer analogy. The Von Karman universal velocity distribution was applied to the condensate flow. Pressure drop was calculated by the Lockhart-Martinelli method and the Zivi void fraction equation. Experimental data was obtained for the flow rate from 240,000 to 485,000 lbm/ft2 hr. R-22 was condensed in a 0.493" I.D. 18 ft. long test section. The measured heat transfer coefficients agreed with the prediction within 10% except a few points in the very low quality region.Sponsored by American Society of Heating, Refrigerating and Air Conditioning Engineers DS

Innovation patterns and policy implications of ADSL penetration in Korea: A case study

Korea has been leading the world in broadband Internet access services since 1999. Based on an in-depth case analysis of the penetration of asymmetric digital subscriber line (ADSL) in Korea, the present study explores the patterns of decision making and interactions among key innovation actors, such as the government, Internet service providers, equipment providers, and content providers, using a conceptual framework wherein models of innovation systems and decision making under uncertainty are combined. The results revealed that the Korean government played a pivotal role in the creation of the ADSL-based Internet service market by providing a strong vision for this emerging service, building a coalition among various key actors, and stimulating initial market needs and supply of necessary equipment during the early period of higher uncertainty. As the level of uncertainty decreased with market evolution, however, the role of industrial actors and their market competition became more important to the rapid growth of the ADSL market. Based on these findings, policy and managerial implications are proposed.Broadband Internet access services Market uncertainty Decision making System of innovation Government policy