Experimental performance of ammonia-charged micro heat pipe array for energy saving

•Micro heat pipe array charged with ammonia is experimentally investigated.•The micro heat pipe array achieves excellent heat transfer capacity of 175 W.•A maximum equivalent thermal conductivity of 7.06 × 105 W/(m∙K) is obtained.•The tilt angle effect of the micro heat pipe array on its performance is studied.•Temperature tolerance test indicates that this structure can undergo 120 °C. Energy is required to be transported effectively during energy exploration, storage and utilization. Micro heat pipe array is a high efficient heat transfer device. Ammonia is promising working medium for micro heat pipe array due to its outstanding thermophysical parameters. However, there are no ammonia-charged micro heat pipe arrays being investigated up to now. In this paper, ammonia-charged micro heat pipe arrays were experimentally studied to enhance the heat transfer capability for energy saving and efficient utilization in practical applications. With dimensions of 520 mm × 20 mm × 2 mm, the micro heat pipe array reached a high heat transfer capability of 175 W, corresponding to an equivalent thermal conductivity of 7.06 × 105 W/(m∙K). Furthermore, the influence of the tilt angle of the micro heat pipe array on the heat transfer characteristics was studied and analyzed. With the increase of the tilt angle, it tended to achieve higher heat transfer capacity due to higher pressure head generated by gravity. Moreover, temperature tolerance test of a shorter micro heat pipe array was conducted and it could operate steadily and reliably under 120 °C, corresponding to a pressure of 92 bar. The experimental results demonstrated that ammonia could make great improvements for energy systems based on micro heat pipe arrays in various applications.