Abstract: A heat storage composition excellent in heat storing effect contains calcium chloride hexahydrate as the main component and an appropriate amount of a nucleating agent combination for inhibiting supercooling which is composed of barium sulfide, barium chloride dihydrate and strontium chloride hexahydrate or of barium chloride dihydrate and strontium chloride hexahydrate and optionally contains an appropriate amount of a thickening agent combination composed of an ultrafine silica powder and glycerin. Latent heat storage capsules contain the above heat storage composition and are improved particularly in their structure such that improved heat storage and release effects can be produced. A temperature control apparatus can make most of the heat storage capsules in the temperature control of a hothouse or the like.

Abstract: First and second face members (12, 14) are secured to the opposite sides of a honeycomb core (16) to provide a structural wall (10). A phase change material (22) is provided within the cells (20) of the wall (10), so that the wall (10) also has the capability of storing thermal energy. The thermal wall (10) may be constructed in the form of a removable shelf (28) for a container (30). It may be constructed in the form of a fixed wall (60) of a container. Such a thermal wall (10) can be constructed to be in the form of a serving vessel, e.g. a dish (FIGS. 14 and 16), a cup (FIG. 13), or the like.

Abstract: A disposable heat storage unit comprises a hermetically sealed, heat conductive pouch containing a quantity of a latent heat substance which may be preheated to an initial temperature higher than that of its heat of fusion so that, upon cooling, it releases first its sensible heat followed by the release of the heat of fusion at a constant temperature over a sustained period of time. The unit may be placed in a container within which is positioned an article whose temperature is to be maintained at an elevated level.

Abstract: A delivering equipment with heat insulating function according to the present invention is utilized in delivering food and so on and comprises an insulated receptacle made of insulating material for storage of food and the like, a concave formed in the bottom portion within the receptacle for storage of regenerating means, and regenerating means disposed in the concave. The regenerating means is preferably comprised of a transparent case packed with regenerating material which contains higher fatty acid as a main content. The regenerating material may be of 100% of behenic acid and preferably contain 10% of cured castor oil so as to depress the solidification point of the regenerating material. Further, a delivering equipment with heat insulating function according to the present invention comprises an insulating receptacle for storage of food and so on and a heat panel with heat pipes disposed within the receptacle so as to equalize the temperature distribution in the receptacle.

Abstract: Continuous thermal energy delivery from a cyclically active thermal energy source having an ON period substantially exceeding an OFF period by passing working fluid through a central working fluid conduit passing through a containment means forming an annular chamber therewith, the annular chamber substantially filled with a liquid-solid phase change thermal energy storage material having a high specific heat in the liquid phase. During insolation, thermal energy superheats the thermal energy storage material and is conducted therethrough to heat the working fluid. During eclipse the superheated thermal energy storage material transmits heat to the working fluid and formation of solid phase of the thermal energy storage material releases heat of fusion adjacent the working fluid conduit for additional supply of heat to the working fluid. A thermal gradient is maintained across the thickness of the thermal energy storage material.

Abstract: A recipient which is filled with a storage medium which expands during phase transformation wherein the recipient is a flexible structure having a geometrical shape such that only the flexibility of the structure is required to increase its volume to compensate for the expansion of the stored medium without creating stress or stretching the walls of the structure.

Abstract: A beverage container with hollow walls and a hollow central member containing a phase-change material whose phase-change is selected to occur at the approximate temperature considered ideal for drinking, whereby the container regulates the temperature of beverage by absorbing and releasing heat from and to the beverage.

Abstract: This invention is a zone storage heat exchanger. In its most basic terms, the heat exchanger is comprised of a main body filled with an energy storage material. There is disposed within the main body a heat transfer fluid annulus for flow of the heat transfer fluid therethrough. The annulus has a hollow inner portion which is filled with an energy storage material.

Abstract: A network of adjacent aggregate containing mesh bags provides structural support to the slab or floor of a building. The network, encased in a sheath of plastic film, also functions as a path for air to be directed by a blower. The openings within the network are filled with gravel, sand or earth packs. At the perimeter of the network an air return system leads to the interior of the building. Thus, the blower can circulate air from the building interior through the network and air return system and back into the interior. Air circulating in the network can undergo heat exchange through the plastic film at the interfaces of the slab, the packs, and the underlying ground. Peripheral ground insulation minimizes lateral heat transfer. Preferably the aggregate containing mesh bags have indexing means to indicate their respective heights from above as they rest on a supportive planar surface.

Abstract: A heat accumulator is disposed in heat exchange relationship with a heating system. The accumulator includes a body of a material having a high heat capacity and a high melting point, such as iron or ceramic material. The accumulator is arranged for being heated by electrical energy during non-peak hours, or "night" energy, to a temperature much higher than the maximum temperature of the heating system. A conduit containing a fluid in a liquid phase is arranged for communication with the water system for setting the heat accumulator in heat exchange relation with the water system of the heating system. A pump is used on startup at high speed to expel water vapor from the accumulator quickly, with the pump having a reduced speed for ordinary operation following startup. The higher pump speed and low conduit volume in the heat accumulator prevents flashing of the water into water vapor during startup operation.

Abstract: This invention is a phase change heat exchange unit which is comprised of upper and lower skeletal support frames having a container for a phase change material disposed therebetween. Each of the frames has a pair of support grids which provide support for the phase change material container and provide a passage for the flow of a heat transfer fluid therethrough so that it can come into direct contact with the container.

Abstract: An improved solar apparatus for heating above 100.degree. C. is disclosed. Said apparatus comprises a solar collector means for heating a heat transferring gas, ducting means extending from said solar collector means for permitting moving of said gas past a heat storage medium whereby heat in said gas will be transferred to said heat storage medium by directly contacting said heat storage medium, flow control means provided in said ducting whereby to permit said gas to flow to said heat storage medium when said solar collector means is radiated by the sun, and to permit said gas to pass through said heat storage medium for recovery of heat therefrom when said solar collector means is not radiated by the sun.

Abstract: A eutectoid salt hydrate composition (phase change material) utilized for the storage of thermal energy at a temperature less than 50.degree. F., in which the optimal mole ratio of potassium chloride to sodium sulfate to ammonium chloride is 1:4:4.

Abstract: A thermal storage furnace system having a mixing means in fluid communication with both a thermal storage means and a thermal storage means bypass conduit for mixing both heated fluid from the thermal storage means and unheated fluid from the thermal storage means bypass conduit to provide for storage of heat in the thermal storage means at a first predetermined higher temperature than desired for heating the interior of the structure, while providing a second predetermined temperature fluid for space heating the interior of the structure by mixing the heated fluid from the thermal storage means with the unheated fluid from the thermal storage means bypass conduit.

Abstract: The present invention relates to a heat storage element having a latent heat storage material sealed in the container under a reduced pressure. This heat storage element permits effective reduction of air in the heat storage element, and therefore, heat is smoothly transferred from outside to the latent heat storage material through the wall of the container. Accordingly, a heat storage element which has a very high heat storage characteristic is realized. Furthermore, this heat storage element, having almost no air sealed in, has a large heat storage density. When this heat storage element is used in combination with an electric heater element, heat will be uniformly transferred from the electric heater element to the latent heat storage material, involving a very small risk of part of the electric heater element being overheated.

Abstract: An apparatus having a heating chamber, (combustion chamber) a heat storing means and heat transferring means of the kind used in households, commercial furnaces, heaters, boilers, etc., having a heating chamber which is spherically arranged; with ports for receiving fuels and a valve for regulating the internal pressure and temperature, allowing for excessive heat to be exhausted into a secondary heat recovery manifold. The spherical heating chamber allows the heat to radiate uniformly. Said heat is stored by mantle material. Said mantle being entirely surrounded by a crust layer and insulating means and an outside protective covering. The apparatus also having means for transferring the stored heat for heating purposes as is generally in common use.

Abstract: An improved particle, and process for producing particle, for use in the storage and retrieval of thermal energy is disclosed. The particle comprises a eutectic material core encapsulated within a high-melting, corrosion resistant material.

Abstract: This invention relates to an electrically heated radiator with heat-accumulating properties. For accumulation of heat in the night-time and for giving off the heat under determined conditions, the radiator according to the invention comprises a heat-insulating container (1) which has an inner space (2) and one or more heat accumulation vessels (3) therein. One or more electrical heating elements (4) for heating the heat accumulation vessels (3) are also housed in the container. The container (1) is surrounded by a jacket (5), so that an air gap (6) is formed around the container (1).

Abstract: This invention is a heat storage system utilizing pressure treated, high density fibrous products to capture and hold heat, particularly in passive solar applications. This heat storage means is preferably in the form of pressure treated logs or timbers which, once heated, will slowly release this heat over an extended period of time.

Abstract: A solar pond of large scale comprises an intake and a return outlet which are not fixedly disposed but are movable in the direction of water depth. The intake and the return outlet are connected through a saline water circulation loop in which necessary saline concentrations with respect to water depths of the solar pond can be efficiently obtained. This allows a solar pond with a specified saline concentration gradient to be established and repaired in a brief period.

Abstract: A double-layered thermal energy storage module comprising front and rear vertically disposed storage sections separated by a flat sheet positioned therebetween. The upper end, lower end, and sides of the storage sections are sealed except for inlet and outlet connections. Each of the storage sections are provided with a plurality of spaced-apart phase change material storage tube segments having fluid flow channel segments positioned therebetween. The segments in the front section are disposed at an opposite angle to the segments in the rear section. The ends of the tube segments in the front section communicate with ends of tube sections in the rear section. The ends of the channel segments in the front section communicate with ends of channel segments in the rear section. The tube segments are filled with a phase change material while the channel segments are filled with a heat transfer fluid.

Abstract: A heat storage device is disclosed in which grooves for supports supporting heat storage vessels, each vessel storing therein a heat storage material, are defined on the lower surface of each of the vessels so that the supports do not project from the bottom surface of each vessel.

Abstract: A reversible liquid/solid phase change composition comprising a mixture of hydrated CaCl.sub.2 and KCl in which the KCl modifies the semi-congruently melting behavior of CaCl.sub.2.6H.sub.2 O to the extent that the mixture approaches congruent melting behavior. The composition preferably includes nucleating additives to modify and suppress the supercooling properties of the liquid phase of the composition. The composition most preferably comprises an admixture of hydrated CaCl.sub.2 and KCl having an amount of NaCl and/or SrCl.sub.2.6H.sub.2 O as an additive sufficient to obtain an effectively congruently melting mixture.

Abstract: Novel catalyst for the photochemical conversion and storage of radiant energy through the conversion of strained cyclic non-conjugated carbon containing compounds to their corresponding conjugated forms comprises ionically bonding a transition metal complex having a square planar geometry and multiple sites of coordination with an anion-exchange resin. A method is provided for the preparation of the novel catalyst and comprises forming an acid salt derivative of the transition metal complex and mixing it together with an anion-exchange resin. A process wherein the novel catalyst is added to a strained cyclic non-conjugated carbon containing compound resulting in the release of heat energy through the conversion of the non-conjugated carbon containing compound to its conjugated form. A process and sealed container means wherein the non-conjugated carbon containing compound and the catalyst are in compartments and are separated until heat energy is required.

Abstract: A fireplace hood made as a massive solid structure defining the top of the firebox of the fireplace. The solid structure absorbs, stores the heat and radiates it when the fireplace is not in use. The massive structure is preferably made monolithic of a poured refractory material with internal hot gas flues open to a surface of the structure and in communication with the firebox for receiving hot gases. The hot gas flues open to a hot gas accumulator in communication with a tubular member for connection to the fireplace chimney. The fireplace has a convection tube system in its walls for heating cold air from the room in which the fireplace is disposed.

Abstract: A solar energy converter which can be used as a solar collector or for the direct mounting on a building for the heating of the interior thereof through a wall of the building has a light transmissive layer spaced from this wall and provided on its inner side with an absorptive surface at which incident solar energy is transformed into heat. One or more solar structures between this layer and the wall contain a chemico-physical phase transformation medium capable of storing latent heat when thermal energy is produced at the absorptive surface and adapted to release this heat through the wall or to a heat carrier fluid which can be passed through a space formed by the solar structure.

Abstract: A cementitious composition comprising a cementitious material and polyethylene glycol or end-capped polyethylene glycol as a phase change material, said polyethylene glycol and said end-capped polyethylene glycol having a molecular weight greater than about 400 and a heat of fusion greater than about 30 cal/g; the compositions are useful in making pre-formed building materials such as concrete blocks, brick, dry wall and the like or in making poured structures such as walls or floor pads; the glycols can be encapsulated to reduce their tendency to retard set.

Abstract: A reversible liquid/solid phase change composition for storing thermal energy. The composition comprises at least one hydrated inorganic salt selected from a salt or mixture of salts that are subject to segregation of its chemical components during repeated freezing and thawing cycles, and a surface active thickening agent in the form of a cationic surfactant and selected from an amine, salts of the amine, or a quaternary ammonium salt of the amine, wherein the thickening agent is present in the hydrated salt in an amount sufficient to form a micelle structure throughout the hydrated salt to prevent such segregation.

Abstract: Low energy demand structure with side walls, roof, and foundation is disclosed wherein the side walls have inner and outer structures, the outer structure of frame construction with very heavy insulation substantially filling the outer structure. The inner surface of the outer wall structure is provided with a panel cover to hold the insulation in place and over the panel a moisture impermeable seal is placed. The inner wall structure is of vertical frame construction and provides circulating air passages and a finish interior surface. The ceiling is of similar structure with the circulating air passages of the ceiling and walls in communication with each other. The upper portion of the structure rests on foundation walls which extend at least 3-4' below the frost line and which are faced with rigid foam insulation also extending 3-4' below the frost line.

Abstract: A thermal energy storage container is disclosed having a generally rectangular configuration. The container is made of a synthetic resinous material and is rotomolded to form a high-strength and seamless container capable of use over extended periods of time and over many freeze-thaw cycles of a thermal energy storage material contained within the container.

Abstract: The invention relates to a temperature stabilized solar reservoir for trapping sunlight and storing solar energy in the solar reservoir itself, which includes a vessel (1) with a bed of a heat storage medium (2) provided with a gelling agent, and means (3,4,5) for extracting heat from the bed. Distinguishing for the invention is that the heat storage medium is pigmented and that the pigmentation is such that the temperature of the heat storage medium is substantially constant counted in a direction downwards towards the bottom of the reservoir. Pigmentation can be carried out in several different ways, e.g. by dissolving or suspending a dye in the heat storage medium (2) or by using pigmented layers having different colors.

Abstract: A process for creating a thermal storage heat sink includes providing a mass of a salt or a salt mixture held in a hollow container having a wall made of electrically conductive material and having an insulated central electrode extending into the salt mass, installing a layer of an electrically conductive material of less density than the salt on top of and in contact with the salt mass to conduct electrical energy from the electrode to the container wall, and then heating the salt mass to a molten state by establishing an electric circuit from a power source through the electrode, the layer of conductive material and the container wall sufficient to melt the salt in contact with the conductive layer.

Abstract: A heating element includes a sealed chamber containing hydrogen gas and a source of high energy light adapted to direct such high energy light into the hydrogen in the chamber to cause disassociation of the hydrogen molecules into hydrogen atoms whereby when the hydrogen atoms recombine to produce hydrogen molecules, heat is generated to heat the container. In addition, a method of heating a container comprises the steps of filling the container with hydrogen gas, directing high energy light into the hydrogen gas to cause disassociation of the hydrogen molecules into hydrogen atoms, and allowing the hydrogen atoms to recombine to form hydrogen molecules thereby giving off heat.

Abstract: A heat storage food container provided with a thermal storage medium, such as wet sand, which retains the heat of the environment to which it has been subjected. The storage medium is provided between a gas impermeable upper shell and a lower gas impermeable thermal insulative shell. The container is adapted to be placed within microwave ovens and heated to a predetermined temperature. Subsequently, food which is prepared in the same or a different environment from which the food container is subjected is placed on the container and will remain at a suitable serving temperature for a relatively long period of time.

Abstract: Novel catalyst for the photochemical conversion and storage of radiant energy through the conversion of strained cyclic non-conjugated carbon containing compounds to their corresponding conjugated forms comprises ionically bonding a transition metal complex having a square planar geometry and multiple sites of coordination with an anion-exchange resin. A method is provided for the preparation of the novel catalyst and comprises forming an acid salt derivative of the transition metal complex and mixing it together with an anion-exchange resin. A process wherein the novel catalyst is added to a strained cyclic non-conjugated carbon containing compound resulting in the release of heat energy through the conversion of the non-conjugated carbon containing compound to its conjugated form. A process and sealed container means wherein the non-conjugated carbon containing compound and the catalyst are in compartments and are separated until heat energy is required.

Abstract: A heat storage material comprises a sodium acetate-water system containing at least 53-69% by weight sodium acetate (CH.sub.3 CO.sub.2 Na), wherein said heat storage material is mixed with a thickener comprising polyvinyl alcohol, paraffin and one or two components selected from the group consisting of formaldehyde and acetone, and has stable performance and little change of heat storage capacity even under repeated storage and release of heat.

Abstract: The solar furnace is constructed of evacuated glass block solar elements that include an interior face, or surface, of zinc. Because of this material, substantial solar radiant energy is retained and radiated to the interior of the furnace, permitting the furnace to reach temperatures of 300.degree. C. and more when located at latitudes between the 35th parallels. Evacuated insulating elements contain the furnace's heat, each element being an evacuated block with one or more preferably reflective interior panels.

Abstract: A heat storage composition comprising sodium sulfate decahydrate as main component, a supercooling inhibitor, and a solid-liquid separation inhibitor, characterized in that hydraulic calcium sulfate and/or calcium sulfate dihydrate is contained as the solid-liquid separation inhibitor in an amount of 2-15% by weight based on the whole weight of the composition, whereby the solid-liquid separation, i.e. the sedimentation of the anhydrous sodium sulfate during the phase transition, is effectively prevented and the long-term stability is improved. The long-term stability of the composition can be more improved by addition of a silica series of thickener.

Abstract: This invention is a system for passive solar heating and cooling of homes, offices and other structures whereby the entire building may be used for storage of heat or cold with both collection and storage occuring essentially without any expenditure of other sources of energy.

Abstract: A heat-storage apparatus providing for especially efficient charging and discharging of a storage medium with heat and greatly facilitating simultaneous charging and discharging of different regions of the medium. The apparatus comprises a vessel having insulating walls and containing a heat transfer fluid bath and a plurality of mobile heat storage elements, each of which contains a phase change material for the storage of heat, and which are disposed within the fluid bath in a sufficiently loose configuration to allow heat-storage elements to migrate about the vessel. A charging conduit and a discharge conduit are disposed within the vessel in the fluid bath so as to induce a migratory circulation of heat-storage elements between regions where elements are being charged and regions where elements are discharged.

Abstract: The system is composed of an aggregate mass through which air can be blown, film sheeting enveloping the mass, and apparatus for directing a flow of air from the interior of a home or other building structure through the aggregate mass and back into the interior. The slab or floor of the home rests on and is supported in part by the enveloped mass. The aggregate mass is a relatively poor conductor of heat and thus heat transfer occurs mainly between the air flowing through the mass and the slab or floor above the mass, and between the air flowing through the mass and the ground below the mass. Preferably, the air from the interior of the building structure is blown into the aggregate mass at an interior location thereof, collected around the perimeter of the enveloped aggregate mass and transferred to the interior of the building structure at peripheral locations in its interior space above but in proximity to the slab or floor. Apparatus for recovering waste heat within the home is also described.

Abstract: A halocline is maintained in open body of salt water at a depth to which a significant amount of solar radiation penetrates by inducing an upward vertical flow in the body of water sufficient to counter wind-mixing and molecular diffusion thereby establishing an ascending or rising solar lake. The upward flow is induced by injecting into the body of water a concentrate with a density greater than the density of liquid at the lower end of the halocline, the concentrate being formed by evaporating liquid drawn from the surface of the body of water. The halocline suppresses convention currents and allows solar radiation to heat the halocline as well as a layer of liquid therebelow to temperatures significantly higher than the surface temperature. Heat for useful work can be extracted from the heat storage layer beneath the halocline.

Abstract: A heat storage material which comprises CaCl.sub.2.6H.sub.2 O, as a main component, containing at least one anhydride selected from the group consisting of an anhydrous bromide and an anhydrous nitrate.

Abstract: A network of adjacent aggregate containing mesh bags provides structural support to the slab or floor of a building. The network, encased in a sheath of plastic film, also functions as a path for air to be directed by a blower. The openings within the network are filled with gravel, sand or earth packs. At the perimeter of the network an air return system leads to the interior of the building. Thus, the blower can circulate air from the building interior through the network and air return system and back into the interior. Air circulating in the network can undergo heat exchange through the plastic film at the interfaces of the slab, the packs, and the underlying ground. Peripheral ground insulation minimizes lateral heat transfer. Preferably the aggregate containing mesh bags have indexing means to indicate their respective heights from above as they rest on a supportive planar surface.

Abstract: A chemical heat pump and storage system employs sulfuric acid and water. In one form, the system includes a generator and condenser, an evaporator and absorber, aqueous acid solution storage and water storage. During a charging cycle, heat is provided to the generator from a heat source to concentrate the acid solution while heat is removed from the condenser to condense the water vapor produced in the generator. Water is then stored in the storage tank. Heat is thus stored in the form of chemical energy in the concentrated acid. The heat removed from the water vapor can be supplied to a heat load of proper temperature or can be rejected. During a discharge cycle, water in the evaporator is supplied with heat to generate water vapor, which is transmitted to the absorber where it is condensed and absorbed into the concentrated acid. Both heats of dilution and condensation of water are removed from the thus diluted acid.

Abstract: A highly effective modular passive solar energy heating unit for heating an enclosed space employs phase change heat storage material, which is optically transparent to visible light when in high-stored-energy liquid state enabling a viewer to see through clearly and which is translucent milky white when in low-stored-energy solid state for providing pleasant illumination to the enclosed space when first illuminated by sunlight in the morning. This phase change material, in a sealed container having two opposite surface areas transparent to sunlight, is polyethylene glycol having a heat of fusion of about 33 to 37 cal./gm. (4,170 to 4,670 Btu's per cubic ft.), a melting point of about 13.degree. to 25.degree. C. (55.degree. F. to 77.degree. F.), a specific gravity of about 1,125 at 20.degree. C., and desirable isotropic freezing and melting characteristics with only very modest volume change during phase change.

Abstract: Structures fabricated from modules of permeable concrete provide heat storage and transfer capability. Such structures derive solar energy directly, store it within the modules for future use in a building, or it can withdraw heat from a building and dispose of it to the sky with little utility derived energy. After erection without mortar both surfaces are coated with fiber filled mastic for strength and to enclose an air circulation system. Each module has a central bin filled with gravel and two planar ducts between each end and the central bin. Air injected into the first, from the outside end, duct removes heat from the surface, distributes the heat by uniform transverse flow to warm the gravel and exits through the third duct. Similarly, at useful times, it removes heat from the gravel and warms the interior surface. At other times and by the same process heat is removed from the interior surface and stored; later it is transferred to the exterior surface and radiated into space.

Abstract: A thermal energy storage apparatus comprising a thermally insulated tank having a bottom, side wall and roof; a plurality of spaced apart modular heat batteries inside the tank supported on load bearing thermal insulation on the tank bottom; each heat battery constituting an enclosed metal shell containing a bed of solid objects and around which objects a liquid can flow; a conduit to feed a hot or cold liquid from outside of the tank to the top of each bed in each battery; and a conduit to withdraw a hot or cold liquid from the bottom of each bed in each battery and deliver it to a destination outside of the tank.

Abstract: A stable density-stratification solar pond 10 for use in the collection and storage of solar thermal energy including a container 12 having a first section 14 characterized by an internal wall of a substantially cylindrical configuration and a second section 16 having an internal wall of a substantially truncated conical configuration surmounting the first section in coaxial alignment therewith, the second section of said container being characterized by a base of a diameter substantially equal to the diameter of the first section and a truncated apex defining a solar energy acceptance opening 20. A body 26 of immiscible liquids is disposed within the container and comprises a lower portion 28 substantially filling the first section of the container and an upper portion 30 substantially filling the second section of the container, said lower portion being an aqueous based liquid of a darker color than the upper portion and of a greater density.

Abstract: This invention relates to a latent heat accumulating greenhouse utilizing solar heat. The object of the invention is to provide a greenhouse which is simple in construction, of high efficiency for heat absorbing and capable of much absorbing and accumulating of heat. A heat accumulating chamber (B) partitioned by transparent sheets (1) is provided between the attic and a floor surface facing north in the greenhouse (A). A blower fan (2) is disposed to confront an opening (1a) provided at the lower portion in said heat accumulating chamber (B). Also, in the heat accumulating chamber (B), a heat accumulating unit (3) having a large number of light transmitting windows (32) and enclosing a phase transformation heat accumulating material (33) such as CaCl.sub.2.6H.sub.2 O, Na.sub.2 SO.sub.4.10H.sub.2 O therein is detachably suspended in a position close to windowpanes at the north side.