Pulsating Heat Pipes Used for Thermal Control of Electronics on Surveillance Systems

Abstract

Surveillance systems have proven to be important applications for high performance thermal control devices, especially the passive ones using heat pipe technology. With the growing need for heat dissipation presented by this type of system, usually hybrid solutions are designed, which include both liquid cooling and passive two-phase thermal control. This last one is usually applied when the heat source is located far from the heat sink and the use of liquid cooling or any other active thermal control system is not possible due to the lack of available space for integration. Since most of the surveillance systems being designed today require thermal control devices that operate under adverse orientation, some restrictions apply. Therefore, the technology that is currently used and disseminated for aerospace missions can find many other applications on surveillance systems for defense purposes. With severe restrictions regarding available space for integration of common thermal control devices, the design and application of pulsating heat pipes become the most indicated solution for the present investigation. Previous investigations have demonstrated that pulsating heat pipes configured as an open loop can operate on adverse conditions, promoting the heat transport from the source to the sink with good reliability. Based on this fact, this investigation is focused on presenting the thermal management of electronic components of a surveillance system being done by pulsating heat pipes configured as open loops. Despite the relatively high temperature difference between the heat source and sink, the open loop pulsating heat pipe is able to transportthe rejected heat from the electronic components to a remote heat dissipation area, while keeping their temperatures within the required range established by the project. The operation of the pulsating heat pipes have proven to be stable and reliable, meeting the project's expectations for thermal control. Nomenclature A = Heat transfer area (m 2 ) C calc = Calculated thermal conductance for the PHP (W/°C) C Cu = Solid copper bar thermal conductance (W/°C) k Cu = Thermal conductivity of copper (W/m°C) L eff = Effective length (m) Q = Heat load (W) η = Ratio of conductance T cond = Average temperature at the condenser (°C) T evap = Average temperature at the evaporator (°C)