Determination of the heat transfer coefficient in air cooled condenser used at biomass power plants

Abstract

Introduction: The project of biomass power plants (EC) in Cuba has as limitation the access to water required by the condensation facilities. Air Cooled Condenser (ACC) is the most widely used solution worldwide to reduce the high rates of water consumption in condensation systems and make the location of the power plant more flexible. In the ACC the working agent pressure is affected by environmental conditions, which produces losses of performance and power. There is currently no method available to estimate the influence of pressure on the heat transfer coefficient in ACC. The objective of the research was to determine which would be the range of operation more adequate regarding pressures and to determine analytically the cause of this problem. Methods: A thematic method of superposition of crossed variables (Breshnetzov) is used to establish a correlation that is capable of predicting the influence of pressure on the heat transfer coefficient in ACC. Results and discussion: By means of crossed superposition is defined the dependence between pressure, heat transfer coefficient and environmental conditions. The combinations of these variables generate two non-homogeneous expressions, which allow us to predict this relationship with adequate fit. As some conclusions, the ACC pressure is inversely proportional to heat transfer coefficient in potency 0,176; decreasing this in 0,95 % for each kPa of increment in the back pressure of steam turbine. The proposal model was correlated with data of 714 ACC facilities, was verified that the mean deviation is ± 35,2 % in 92,4 % of available data.