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Abstract: Experimental and theoretical investigations of water-side fouling have been performed inside four corrugated plate heat exchangers. They have different geometric parameters, such as plate height, plate spacing, and plate angle. Fouling experiments including particulate fouling tests and composite particulate and precipitation fouling tests have been performed. The tests are primarily focused on the effects of concentration and average velocity. Scanning electron microscope (SEM) was used to investigate the microscopic structures of composite fouling. Heat transfer coefficients and friction factors have been obtained in clean tests. The plate heat exchanger with the largest d e and height to pitch ratio shows the best anti-fouling performance. The Von-Karman analogy was used to obtain mass transfer coefficient to develop appropriate semi-theoretical fouling correlations; The wall shear stress is obtained from the pressure drop. The model predictions agree well with experimental data. [Copyright &y& Elsevier]

Abstract: An experimental investigation was performed for single-phase flow and condensation characteristics inside five micro-fin tubes with the same outer diameter 5mm and helix angle 18°. Data are for mass fluxes ranging from about 200 to 650kg/m2 s. The nominal saturation temperature is 320K, with inlet and outlet qualities of 0.8 and 0.1, respectively. The results suggest that Tube 4 has the highest condensation heat transfer coefficient and also the highest condensation pressure drop penalty, while Tube 5 has the highest enhancement ratio due to its lowest pressure drop penalty and intermediate heat transfer coefficient. Condensation heat transfer coefficient flattens out gradually as G decreases when G <400kg/(m2 s) for Tube 2 and Tube 4. This nonlinear mass-flux effect may be explained by the complex interactions between micro-fins and fluid, including liquid drainage by surface tension and interfacial turbulence. In addition, the experimental data was analyzed using seven existing pressure-drop correlations and four heat-transfer models to verify their respective accuracies. [Copyright &y& Elsevier]

Abstract: This study focuses on the thermodynamic analysis of saturated vapor flowing slowly onto and condensing on an elliptical tube with variable wall temperature. An entropy generation minimization (EGM), technique is applied as a unique measure to study the thermodynamic losses caused by heat transfer and film-flow friction for the laminar film condensation on a non-isothermal horizontal elliptical tube. The results provide us how the geometric parameter ellipticity and the amplitude of non-isothermal wall temperature variation affect entropy generation during filmwise condensation heat-transfer process. The optimal design can be achieved by analyzing entropy generation in film condensation on a horizontal elliptical tube with further account for the amplitude of non-isothermal wall temperature variation. [Copyright &y& Elsevier]

Abstract: This paper aims to perform thermodynamic analysis of saturated vapor flowing slowly onto and condensing on an elliptical cylinder. This analysis provides us how the geometric parameter-ellipticity affects entropy generation during film-wise condensation heat transfer process. The results observe that local condensate film thickness decreases with an increase in ellipticity of a cylinder. From the first law point of view, the local heat transfer coefficient enhances as ellipticity increases. Meanwhile, from the second law point of view, entropy generation increases with increasing the value of ellipticity. We derive an expression for entropy generation, which accounts for the combined action of the specified irreversibilities. The result demonstrates that thermal irreversibility dominates over film flow friction irreversibility. Finally, an expression of minimizing entropy generation in laminar film condensation heat transfer is obtained. [Copyright &y& Elsevier]