Described herein are expandable center arrangements for use in a tubular reactor, such as a reformer, for enhancing heat transfer and reactor efficiency. The expandable center arrangement can include a cone being expandable in the radial direction and an expansion weight for promoting expansion of the cone. The cone and expansion weight can be slidably arranged on a center support. Expansion of the cones in the radial direction forces reactor components radially outward to an outer tube that houses the reactor components and expandable center arrangement. Expansion of reactor components towards the outer tube promotes heat for carrying out catalytic reactions.