Heat pipe array for planar cooling of rotating radar systems

This paper presents a planar cooling strategy for rotating radar systems using heat pipe technology. The proposed design uses six 1 m long heat pipes in parallel oriented in an evaporator-down modus at an elevation angle of 85 deg. An analytical model based on conventional heat pipe limits is used to predict the performance taking into account both gravitational and centrifugal forces. The heat pipe array is mounted on a rotating platform of which both the mounting angle w.r.t. the rotational arm and rotational speed can be varied. The radial distance w.r.t. the rotational axis was set at 0.5 m. The setup was tested in an environmental chamber to simulate higher ambient temperatures as well. Moreover, measurements were conducted by varying the heat sink airflow rates. The performance was determined by the temperature gradient across the planar structure. Successful heat pipe operation and experimental performances were determined for a number of application parameters. At higher rotational speeds, the influence of centrifugal forces that may assist or hinder the working fluid circulation became discernible. For higher rotational frequencies, the mounting angle proved to be of (minor) influence on the performance in agreement with the developed model. The current design was validated for effective planar cooling of a rotating radar system for planar heat loads up to 1000 W. Temperature gradients across the planar structure remain below critical limits and overall thermal resistances from planar to ambient air conditions of 0.040 K/W and below were observed.