High Performance Heat Storage and Dissipation Technology

High power solid state laser systems operating in a pulse mode dissipate the transient and excessively large waste heat from the laser diode arrays and gain material. The heat storage option using Phase Change Materials (PCMs) has been considered to manage such peak heat loads not relying on oversized systems for real-time cooling. However, the PCM heat storage systems suffer from the low heat storage densities and poor thermal conductivities of the conventional PCMs, consequently requiring large PCM volumes housed in thermal conductors such as aluminum or graphite foams. We developed a high performance metal hydride heat storage system for efficient and passive acquisition, storage, transport and dissipation of the transient, high heat flux heat from the high power solid state laser systems. The greater volumetric heat storage capacity of metal hydrides than the conventional PCMs can be translated into very compact systems with shorter heat transfer paths and therefore less thermal resistance. Other exclusive properties of the metal hydride materials consist of fast thermal response and active cooling capability required for the precision temperature control and transient high heat flux cooling. This paper discusses the operating principle and heat storage performance results of the metal hydride heat storage system through system analysis and prototype testing. The results revealed the superior heat storage performance of the metal hydride system to a conventional PCM system in terms of temperature excursion and system volume requirement. NOMENCLATURE Dp particle diameter ( m) E energy (J) H/M hydrogen concentration in metal (or alloy) H hydrogen atom M metal (alloy) atom p pressure (atm) Q heat flow rate (W) R universal gas constant (=8.314kJ/kmole-K) T temperature (K) t time (s) V volume (liter) x non-stoichiometric constant Greek α, β metal hydride phases f H ∆ heat of formation (kJ/H2-kgmole) f S ∆ standard entropy of formation (kJ/H2-kgmole-K) Subscripts A, B metal hydride reactors c cooling f formation or final h high i initial l low MH metal hydride p particle r release s heat source or stored Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.