PASSIVE DOWNWARD HEAT-TRANSPORT - EXPERIMENTAL RESULTS OF A TECHNICAL UNIT

A bench scale model for passive downward transport of heat has been built and tested. The heat is transported by evaporation of a fluid in an evaporator at a higher level and condensation at a lower level. The condensate is returned to the evaporator by the periodic operation of a self-actuated float valve without disconnecting the heat delivery to the evaporator. The cost of lifting the liquid back to the evaporator is a temperature difference of a few degrees centigrade between the evaporator and the heat store. The unit works under moderate pressure (a maximum of 9 bar at 85 degree C). The actual vertical distance between heat source and heat store is about 1 m; a pressure difference equivalent to a vertical distance of 15 m was introduced by two spring-loaded check valves. The system can easily be integrated with a solar heat collector working with a 2-phase fluid.