Heat exchangers for thermal storage systems include a valve that can direct process fluid passing through the heat exchanger through supplemental heat exchanger tubing based on a temperature of the process fluid. The supplemental heat exchanger tubing can be located in areas where ice formation can occur during freezing of the storage fluid of the thermal storage system, but apart from the standard flow path for the heat exchanger. The valve can be a thermally-actuated valve. The thermally actuated valve can be set to divert flow of the process fluid to the supplemental tubing when the process fluid is at or above a melting temperature of the storage fluid. Methods can include selectively flowing process fluid through supplemental heat exchange tubing when it is at a temperature greater than the melting point of a storage material.