Speaker
Description
The LHP100K project focuses on the following temperature range of interest: 100-150 K. It encompasses the current NIR/SWIR detector operational temperature as well as the future MWIR one that could work around 100-120 K (Figure 1). Above all, this project aimed at designing, building and testing a breadboard (BB) of a LHP suitable for these uses. The whole project has been divided into 4 main steps:
1. LHP design, definition and justification
2. Breadboard manufacturing, assembly and verification tests
3. TVac test
4. Test result analysis
First of all, it has been necessary to identify the best working fluid. Out of the several candidates, methane has been retained as the most suitable working fluid for the considered use case. Namely, the LHP was expected to be operated at 5 W / 100 K and 70 W / 150 K (see Figure 2 for the Clapeyron curves of every preselected working fluid). Oxygen and argon, while having an interesting Clapeyron curve, have their critical temperature point too close from the 150 K hot operational temperature.
Methane is not in a two-phase state between 190 K and 320 K. In this range of temperature, a methane LHP will have its working fluid fully gaseous. This implies two major design drivers. First, a voluminous tank shall be added, on the vapour line, to increase the LHP overall volume and to limit the internal pressure when all the fluid is gaseous. This tank has been called “Pressure Reduced Reservoir” (PRR). Second, a secondary evaporator shall be implemented to perform the preliminary cool down of the main evaporator. As a matter of fact, above 190 K, the main evaporator is not able to run since the working fluid is fully gaseous. The secondary evaporator is thus use to cool down the main evaporator below the methane temperature critical point. To do so, the secondary evaporator shall be thermally linked to the heat sink (radiator for instance).
on the overall the LHP100K worked well.
1. First the LHP was successfully operated between 5 W / 111 K and 40 W / 150 K which is a wide range of temperature and power; although it is a reduced range in comparison with the requirements.
2. Second the heterogenous heating was tested, assessed and validated. Power has been injected on both evaporator tubes, then only one, back on two and again on only one, the other one, without significative change of operation on the overall LHP.
3. Moreover, the secondary evaporator was proven efficient: increasing the power on the secondary evaporator rapidly reduce the saturation temperature. Several watts were enough.
4. Besides the inhibition heater also was proven efficient: increasing the power on the reservoir quickly increase the saturation temperature. A few watts were sufficient.
