Loop heat pipes (LHPs) are used in multiple terrestrial and space applications. Transient analysis of conventional and advanced loop heat pipes with complex radiators under varying conditions where the heat load and the effective sink temperature change in time can be best accomplished using Thermal Desktop™.

Over the past 15 years, the industry standard tool for thermal analysis, SINDA, has been expanded to include advanced thermodynamic and hydrodynamic solutions (“FLUINT”). With the recent culmination of the unique modeling tools, SINDA/ FLUINT has arguably become the most complete general-purpose thermohydraulic network analyzer that is available.

A cryogenic capillary pumped loop (CPL) has been developed, designed, fabricated and successfully demonstrated by test. Using no moving parts, the novel device is able to start from a supercritical state and cool a remote dissipation source to 80-90K. Design studies were conducted for integration requirements and component design optimization and prototype units were designed, fabricated and successfully tested with excellent results.

The NASA-standard thermohydraulic analyzer, SINDA/ FLUINT, has been used to model various aspects of loop heat pipe  (LHP) operation for more than 12 years. Indeed, this code has many features that were specifically designed for just such specialized tasks, and is unique in this respect.

The loop heat pipe (LHP) is known to have a lower limit on input power. Below this limit the system may not start properly creating the potential for critical payload components to overheat. The LHP becomes especially susceptible to these low power start-up failures following diode operation, intentional shut-down of the device, or very cold conditions. These limits are affected by the presence of adverse tilt, mass on the evaporator, and noncondensible gas in the working fluid.

Two-phase loops with several capillary evaporators are being developed for a variety of existing and future space applications. While modeling of loop heat pipes with one or two conventional evaporators is relatively straightforward and can be done, for example, using Excel VBA, modeling of loops with several three-port or four-port evaporators requires more specialized software such as Thermal Desktop™.