دراسة العوامل المؤثرة على أداء المبادل الحراري ذي الأنابيب الحرارية ذات فرق درجة حرارة كبير في محطة قدرة بخارية

Investigation the Factors Affecting the Performance of Heat Exchanger Heat Pipes with High Temperature Difference in Steam Power Plant

Abstract
In many of applications, such as power plants, iron factories, etc., thermal energy may be lost to ambient so, using devices such as heat pipe heat exchangers is necessary to recover this energy. In this study, a thermosiphon heat pipe heat exchanger is constructed for this purpose. The thermal performance of this exchanger is numerically (by using ANSYS-Fluent software) and experimentally investigated. This is at different filling ratios (35%, 50% and 75%) of a working fluid (DOWTHERM™ A), air velocities of (0.5, 1, 1.5, 2 and 2.5 m/s) at the condenser inlet and wide range of the evaporator inlet air temperature (160 to 320 °C). The exchanger model used in this study includes 60 copper heat pipes with square aluminum fins. The heat pipe (100 cm total length) consists of three sections namely: evaporation section (40 cm length), adiabatic section (20 cm length) and condensing section (40 cm length). The results show that the filling ratio, air velocity and evaporator air temperature have an important effect on the thermal performance of the heat exchanger. In overall, the optimum values of the filling ratio, air velocity and evaporator inlet air temperature, to obtain the best thermal performance of the exchanger, are 50%, 0.5 m/s and 320 °C respectively. Where at these values, the highest condenser air temperature and maximum exchanger effectiveness (240 °C and 74% numerically and 250 °C and 77% experimentally) are obtained. Through the comparison between the numerical and experimental results, an excellent agreement is found between them with a maximum deviation percentage does not exceed 5%.