Vapor Compression Refrigeration Loop with Spray Cooling for High Heat Flux Thermal Control

Laser diodes are the key component in many space-based applications ranging from communication systems to optical sensors/detectors. Laser diode emitters however dissipate large amounts of waste heat of their own from the small footprint of the device. As a result, the dissipating heat flux from the laser diodes can reach a level as high as 1kW/cm2. The performance and reliability of laser diode arrays can degrade severely if the waste heat is not properly managed. Indeed temperature control is critical when the laser diode arrays are used for pumping a solid-state laser such as Nd:YAG. The solid-state laser has a narrow absorption bandwidth and requires a narrow pump source. Any variation in temperature throughout the array will cause the emitters to emit different wavelengths, thus increasing the bandwidth of the array. Spray cooling is probably the only available thermal control technology capable of dispersing heat fluxes of this extreme level (>200W/cm2). Spray cooling is a heat removal method by an evaporative heat transfer process. In this research project, a novel concept that combines a conventional refrigeration cycle and spray cooling technique into one system is proposed as the solution to extremely high heat flux problems.