NOVELTY - A heat-transport system (10) has flow path portions (11) and (12) and heat source (13). The system flows down heat-transport fluid containing solvent including water, microparticles and dispersing agent which disperses microparticles in solvent, and carries out heat transport from flow path portion (11) which receives heat from heat source, to flow path portion (12) which does not receive heat from heat source. Microparticles in the heat-transport fluid gather and form aggregation along a direction, when more microparticles are flown through portion (11) than portion (12).    USE - Heat-transport system. Uses include but are not limited to inverter cooling, fuel battery cooling, secondary battery cooling, motor cooling, electronic-device element cooling, molten metal supply, floor heating and bathroom heating.    ADVANTAGE - The system has improved heat-transporting characteristics. The heat-transport fluid used in the heat-transport system has improved heat conductivity, reduced flow resistance and suppressed viscosity. The energy consumption of pump in the system is reduced.    DETAILED DESCRIPTION - A heat-transport system (10) has flow path portions (11) and (12) and heat source (13). The system flows down heat-transport fluid containing solvent including water or organic substance, microparticles dispersed in solvent, and dispersing agent which contacts the microparticles and disperses the microparticles in the solvent, and carries out heat transport from flow path portion (11) which receives heat from heat source, to flow path portion (12) which does not receive heat from heat source. Size of dispersed state of microparticles is different in the flow path portions (11) and (12). The microparticles in the heat-transport fluid gather and form aggregation along a direction, when more microparticles are flown through flow path portion (11) than the flow path portion (12).    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the heat-transport system.    Heat-transport system (10)    Flow path portions (11,12)    Heat source (13)    Pump (14)    Stirring apparatus (15)