A fluid purification device is provided. The fluid purification device includes a heat-transfer bed comprising a heat storage material, a first plenum attached to a first opening of the heat-transfer bed, and a second plenum attached to a second opening of the heat-transfer bed arranged on opposite sides of the heat-transfer bed. The first and second plenums alternatingly supply a fluid to the heat-transfer bed such that the fluid heats up and reacts while flowing through the heat storage material, and the other plenum drains the reacted fluid. The first plenum extends lengthwise along a first spatial direction. A heat blocking element arranged in the first plenum is spaced apart from the heat-transfer bed and from a housing of the first plenum, extends beyond the first opening, and lowers a speed of the fluid entering the heat-transfer bed toward the middle of the heat-transfer bed along the first spatial direction to cause an angled flow of the fluid through the heat storage material to lateral side portions of the heat-transfer bed.