Charge dynamics of a low-pressure natural gas accumulator with solid adsorbent, novel thermosyphon and recirculation loop

Abstract

The efficiency of the adsorption natural gas (ANG) tanks depends on their possibilities of accumulating the gas during a short period of time inside porous materials (adsorbents) at a high density and low pressure. This work is aimed at ensuring a fast charging of the ANG accumulator using both active (recirculation loop) and passive (finned thermosyphon) thermal management systems in sorbent bed. This approach makes it possible to stimulate gas adsorption and avoid the rise of temperature in the storage tank due to the enthalpy of adsorption.The paper describes a recirculation charging of a thermally controlled gas accumulator in the 195–350 K temperature range and pressures up to 5 MPa at the stationary filling station. Numerical results are presented for a promising low-pressure storage tank, packed with activated carbon fibrous material and furnished a thermosyphon heat exchanger and gas inlet and outlet tubes for recirculation loop. Modeling is performed using the commercial finite volume flow solver Fluent on ANSYS. It is showed that the hybrid cooling technology determines feasibility of ANG tank and guarantees a high gas mass under dynamic conditions.Two designs of novel thermosyphons with long horizontal evaporators were developed for sorbent bed cooling applications:a loop thermosyphon with porous coating of the evaporator annular channel (LTPE), and vapordynamic thermosyphon (VDT) with wickless annular channels in the evaporator and condenser. The finned evaporators in both cases were designed to interface with sorbent bed of the storage tank. The thermal characteristics of the thermosyphons have been experimental investigated and analyzed.