Deutsche Forschungs- Und Versuchsanstalt Fur Luft- Und Raumfahrt E.v.

Friedrich Lindner

Kurt Scheunemann

Frank Mehlhorn

A method and apparatus for inoculating a liquid latent heat storage substance of the type convertible to the solid state on cooling is disclosed. A portion of the substance is caused to crystallize on a cooled active surface, immersed in the substance and preferably vertically arranged, whereupon the active surface is heated to fuse-off the formed crystals to release them into the liquid portion of the storage substance to thus form inoculation seeds on which further crystallization of the storage substance takes place on withdrawal of heat from same. In one described embodiment, a pair of active surfaces is provided by using a Peltier element operating with a DC source having selectively reversible polarity whereby one surface is cooled down while the other is heated and vice versa, depending on the instant polarity of the DC source. In another embodiment, the active surface is alternately heated and cooled by heat carrier medium of a heat pump circulation system drawn from the respective sections of the system in alternating fashion. Due to the formation of crystallization seeds from the heat storage substance, problems normally associated with the use of a foreign inoculation substance are avoided.

Method and apparatus for inoculating crystallization seeds into a liquid

A method is disclosed for increasing the cycle stability of a latent heat accumulator medium consisting essentially of a pure or saturated sodium sulfate salt melt. The cycle stability is increased by adding sulfuric acid to the latent heat accumulator medium in an amount of from 0.5 to 3%, by weight, based on the weight of the latent heat accumulator medium. The pH value of the latent heat accumulator medium is lowered without precipitation of impurities or the occurance of supercooling in the latent heat accumulator medium.

Increasing the cycle stability of a sodium sulfate heat exchange medium

A latent heat accumulator is disclosed including an upright container hav, in a major volume first section, a latent heat storage medium, and a passage for a heat exchange medium extending through the charge in the first section. The passage is of the type of a conduit provided with intake openings at different levels. The flow of heat exchange medium through the conduit generates low pressure at the intake openings with the result that a part of the surrounding charge of the heat storage medium is drawn into the conduit for thorough intermixing and heat transfer. The intake openings are preferably protected to prevent large solidified particles of the heat storage medium from blocking the openings or from entering the conduit. The invention improves the heat transfer capacity and reduces the charge of the heat storage medium entering the associated heat exchange circulation system while retaining a relatively simple structure of the accumulator.

Latent heat accumulator

A latent heat accumulator is disclosed including a vessel for receiving a tent heat storage medium and a circuit for a heat exchanger medium. The heat exchanger medium is immiscible with the latent heat storage medium, has a different density than the heat storage medium and is openly conveyed through the heat storage medium. The vessel contains a collecting chamber for the heat exchanger medium and has a heat exchanger arranged therein. An external heat carrier medium flows through the heat exchanger for transfer of heat between the heat carrier medium and the heat exchange medium. The accumulator is characterized in that a first heat carrier medium for adding heat and a second heat carrier medium for withdrawing heat are conveyed in the heat exchanger in separate conduit systems which are in heat-conductive contact with each other and with the surrounding heat exchanger medium.

A latent heat accumulator gives up its heat when a heat exchange medium is assed through the accumulator and around a circuit containing an external heat sink. The heat storage medium in the accumulator changes its state from liquid to solid as it gives up heat. In order to prevent heat exchange medium from being trapped by the heat storage medium as it solidifies, the exchange medium is always introduced directly into a zone where the storage medium is liquid.

Discharging a latent-heat accumulator

A method of charging and discharging a heat accumulator is disclosed, when a heat exchange medium is passed through a heat accumulator medium. The heat exchange medium can either be heated or cooled external to the heat accumulator medium. If it is heated, it gives up its heat to the accumulator medium, and in doing so changes from the gaseous to the liquid state. If it is cooled, it absorbs heat from the accumulator medium, and in doing so changes from the liquid to the gaseous state. In both cases, the opposite change of state is brought about by the heating or cooling external to the heat accumulator medium.

Method for charging or discharging a heat accumulator

A container is disclosed for storing a heat storage medium which changes ween solid and fluid states to store and release heat, characterized in that the container includes flexible walls which are displaced to vary the volume of the container in accordance with changes of the volume of the heat storage medium when in the solid state. The container includes at least one biasing device which normally biases the resilient walls toward an inwardly contracted condition for storing a first volume of the heat storage medium in the fluid state. During initial removal of heat from the medium, the medium changes from its fluid to its solid state, and upon further removal of heat from the solid medium, the density of the solid medium increases, thereby resulting in a decrease in the volume of the solid medium with the container remaining in its initial contracted condition. Upon addition of heat to the solid medium, the density of the solid medium decreases thereby resulting in an increase in volume of the solid medium and an attendant increase in volume of the container to its expanded condition.

Container for a heat storage medium

Heat exchange method and apparatus are disclosed which include the use of o non-mixable media of different temperatures that are brought in direct contact with each other to effect the transfer of heat from the heating medium to the heat storage medium. One of the media is normally a fluid and the other is preferably a substance -- such as a crystalline material -- which is operable between solid and liquid phases, whereby the latent heat produced by the phase transition is utilized in the heat exchanging process. Owing to the non-mixability of the two media, the first medium is bubbled through the second in direct heat exchanging contact when the second medium is in the liquid phase. A supply conduit including a submerged perforated portion is used to introduce the first medium within the second, an imperforate by-pass conduit being also provided for conveying the first medium in heat transfer relation through the second medium when the supply conduit is clogged by the second medium when it is in its solid phase.

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Stuttgart, Germany

Friedrich Lindner