Nonlinear Model Identification Adaptive Heater Control Design for Loop Heat Pipes

Loop Heat Pipes (LHP) are complex, thermodynamic heat transport systems for the thermal control of temperature-sensitive systems with locally separated heat sources and heat sinks. Through evaporation and condensation of a working fluid, the two-phase LHP achieves a high heat transfer coefficient. The LHP operating temperature strongly depends on the heat load and the sink temperature. Therefore, an additional control heater on the compensation chamber is used to keep a desired operating temperature under changing operating conditions. Compared to the commonly used PID controller, the temperature control performance of the control heater is improved by a nonlinear model identification adaptive control design. Unknown time-variant model parameters are estimated online to improve the model accuracy. The temperature prediction is validated with experimental data from a LHP test bench. The presented nonlinear control algorithm is implemented and tested in a numerical simulation of the LHP.