Lunar Gateway Crew Quarter Ventilation Configuration Assessment

In the context of human habitat inside the Lunar Gateway orbiting around the moon, this thesis has the aim of assessing the proposed ventilation system of the Private Crew Compartment, and evaluating its meeting of requirements in terms of thermal comfort and carbon dioxide concentration. Beginning with the stated architecture, the assessments have been carried out through a thermofluidic lumped parameter model that represents the pipeline ventilation system, providing the housing for astronauts with cool and fresh air. In order to build the model, the behavior of the elements has been extracted from the Idelchik’s manual and from the CFD analyses for two particular components: the wye fitting with its previous elements and the adapter from circular to flat section. The study accounts for a grid sensitivity analysis to trade off the right mesh to keep the computational cost low, introducing the Richardson extrapolation method and the grid convergence index. The goal of the CFD analysis was to find the delta pressure between each side inlet and the common outlet for the wye fitting and between the inlet and outlet of the adapter. Together with the inlet velocity, such results allowed for the computation of the loss factor. In such a way, the k-factor has been characterized for several values of flow rate, changing both the total flow rate and the split ratio between the two inlets. The loss trend of the two components has been obtained, and it has been noted in accordance with the behavior of similar components. Since no detailed model of the I-Hab ventilation line is known, its behavior has been characterized from provided data at noticeable sections in terms of the pressure loss coefficient of each element. In the first investigation, the end diffuser k-factor is calculated, and the flow rate after the middle diffuser is assumed to be the one declared by the manufacturer. In a further assessment, the middle diffuser has been introduced, starting from the original THC line geometry. Furthermore, from the conclusions of the first design assessment, other configurations have been suggested to meet the requirements. For each of them, a model has been built in the Thermal Desktop environment and simulated in all the scenarios. The simulations have also been conducted with the introduction of a solver procedure, changing design parameters to reach the target. All the simulations had the fan rotational speed and the valve opening angle as variables. In the process of testing a configuration, the first two checks have been the worst cases, hence the one with a higher heat load inside the crew quarters while maximum temperature in the module, and minimum heat load while the cabin temperature is at its minimum, respectively with the higher and lower selectable temperature inside. Whenever a working point for the configuration has been found, the configuration has been studied in detail, assessing the carbon dioxide level as well. In conclusion, it has been assessed that the first configuration cannot satisfy the requirements in both the THC line assumptions, while the other set ups are able to manage hot and cold cases and all the selectable temperatures in between, and no issue with the carbon dioxide is detected in terms of partial pressure. To move to further studies of the crew compartment ventilation system, it is paramount to have a detailed characterization of the module ventilation system where the crew quarters are attached.