A heat transfer system and related method of heat transfer is provided. The heat transfer system includes a tubular receiver positioned to receive heat from a heat source, the receiver comprising one or more enclosed tubes configured for gravity-driven flow of a particulate heat transfer fluid therethrough in a dense, unfluidized state having a particle volume fraction of at least about 25%; and at least one storage vessel in fluid communication with the tubular receiver and positioned to receive the heat transfer fluid therefrom, wherein the particulate heat transfer fluid includes a plurality of particles of a metal-containing material having a melting point of greater than 800 C, the heat transfer fluid being substantially free of a liquid component.