Scaling up and optimization of hydrogen compressor and storage systems using simulation software

The hydrogen absorption/desorption behavior is highly dependent on the temperature distribution within the metal hydride. Cylindrical cells contain the metal hydride material, which is in powder form. Several such cells are placed in a “shell-and-tube heat exchanger” type of arrangement within a bigger cylindrical container to form the overall compressor system. The thermal management of such a system is commonly done through the circulation of a thermal medium, such as water, steam, air or any other medium at accurately controlled thermal and flow conditions to provide the required heating or cooling power. GRZ technologies has developed a numerical procedure to simulate a range of systems using ANSYS Fluent and in-house developed models. The compressor or storage geometry is modeled parametrically, meshed and simulated. The spatial distribution of temperature and flow field are obtained from the numerical simulation (see Figure 1) for the case of an industrial-scale hydrogen compressor. The thermal medium flow velocity and distribution plays an important role in determining the temperature distribution within the metal hydride and eventually the compressor’s performance. Using the parametric model, various options for reducing manufacturing and operating costs can be explored, while achieving the required hydrogen delivery pressure, flow rate and capacity.

With Ansys Fluent, GRZ technologies was able to establish a versatile and robust numerical process for evaluation of the design of a metal hydride-based hydrogen system. This drastically reduces the development cycle of new products by enabling the targeted optimization of relevant design and operating parameters. Ultimately, the detailed insights obtained through numerical simulations allow significant reduction in manufacturing and operating costs of the developed systems. In addition, it provides a solid foundation for the development and refinement of various reduced-order computationally efficient models.

The numerical method described above can be used for many thermal and chemical technologies with similar physics. With Ansys Fluent, the thermal compression process is simulated, and the relevant evaluation parameters are quantified. The numerical results are interpreted based on the evaluation parameters defined, e.g., the maximum metal hydride temperature (see Figure 2), and an appropriate course of action is determined to optimize the design. The coolant flow path is optimized by varying design parameters (e.g., tube arrangement) to improve performance (e.g., minimize pumping power) while maintaining certain requirements (e.g., minimum temperature non-uniformities). After achieving the optimum design, the operating limits (e.g., coolant flow rates) of the compressor are determined where the target compression rates are achieved. Novel mathematical models describing the thermal compression and storage processes can also be tested and evaluated.