AU667289B2 - Heat accumulating material and its use - Google Patents

Description

'DATE 16/03/93 APPLN. ID 84317/91 111111IIIII IIIW!lIhIIiII AOJP DATE 27/05/93 PCT NUMBER PCT/SU91/00173 (51) MewcgynapoJAHaa imacCcu~bHmicaHa ()Hop eiap~ouymaIH: WO 93/04 137 u~o6peTe_'nsn 5: CO9K 5/02, G12B Al (43) IXaTa meac~lyHapoJ~Hofi 17/06, EO4B 1/74, A62D 1/00 Hy6AhHiCaIXHuI1: 4 m~apra 1993 (04.03.93) (21) Hoxep meaIynapROAHOf aanHai: PCT/SU91/0017 6302 j.3oorjBuccaj.5 c. 17 (SU) [MO- ROZ. Ella Mikhailovna. Novosibirsk BOrTA- Ill c k C 3 (SU) [BOGDA- 3irsk BOP- SU/SU]; HOBOC11- A ~CB. I (SU) [BOGna, Novosibirsk CXC\CJ aeBHa [SU/SU]; CmsenL1HHjicoro, Aueaa, A. 5/2 (SU) MMERCE AND "Ro i i- r-c"C C(LI, 0 eficHi naTeHT), C_"E Ve_ Ci"JQ6-'k~' CA, CH (eBponamirr), DK (eBvHfi IaTeHT), FR ~xnfi namirr), GR C or~emoMCxIiif naTeHT), IT VITSKY, Emmanuil Aronovich, Novosibirsk (SU)I. TeiRT), MC (esponeficlceii naTeliT), NL (enponefiixl HAPMOH BajieHmji HmcojzaeBHM [SU/SU]; HOBOCH- na~reir), SE (enponeficjuaii naTeffi), US, 6Hic 630072, yaz. Boeso~cicoro, 1, ice. I (SU) [PAR- MONj, Valentin Nikolaevich, Novosibirsk (SU)I. Ouy6Aumionaua MOP03 Dims Msxain~oB~a ;HoBocm6Hpcix W ao~ Anu (54) Title: HEAT ACCUMULATING MATERIAL AND ITS USE (54) Ha3aamie Hao6peTeimui TErMJOAKKYMYJIHPYIOIIJHR MATEPHAJI 14 EPo HPHMEHEHH4E Iree (57) Abstract A heat accumulating material is proposed, consisting of a thermally inert matrix which is a substance with open pores, and of a thermosensitive working substance which is a hygroscopic substance capable of reversible processes of dehydrationhydration. A heat accumulating material is intended for use as an agent for cooling and heating of a gaseous (air) medium, an agent for thermostatic conditioning and protection against heating of articles or construction structures, for example, elements of radioelectronic devices, as well as a fire suppressing means.

HEAT-ACCUMULAT,ING MATERIAL AND USE THEREOF Field of the Invention The present invention relates to the field of materials for:accumulating heat using salt hydrates, and more particularly to a heat-accumulating material containing a thermally inert matrix and salt crystallohydrates as a working substance.

The invention solves the problem of termperature control for gas streams and solid bodies; it is intended for using in private life and technological processes such as conditioning and heating living and working premises, thermostating articles heating whereof is undesirable, as well as for extinguishing fires.

Prior art The most simple and well-khown heat-accumulating material is water. An extremely high heat capacity of water (1 qal/g grade) ensures trice as much heat storage at the same meass in water accumulators as that in accumulators based, for example, on rocky ground. However, in terms of a volume unit the difference is levelled due to different densities of.water and rock.

Hereinbelow it will be shown that when passing to specific heat-accumulating materials such as phase change materials.

PCM, the advantage of solid-phase systems becomes still more substantial. The accumulation of heat by solid bodies have been studied and realized in a great number of patents. US Patent No. 4,708,812 by J.C. Hatfield and A.W. Va discloses in detail theoretical and practical problems of heat accumulation in PCM systems based on processes of melting and crystallizing of solid materials.

In such systems substancep from the' salt crystallohydrates group are used. In Table 1 there are presented reference date on melting temperatures of crystallohydrates.

i Table 1 Melting points and latent melting heats of some crystallohydrates Salt Melting Latent apoint °C melting References Sheat cal/g 1 23 4 S40 I

C.

j Al 2 1 .2 3 4 Na 2 CrO. 10 H 2 0 23 39 Handbook Chemistry Na2 SO4 10 H 0 31 51.3 and Physics Na 2

S

2 0 3 5 H 2 0 48 47.8 33 ed., p. 19'16-1 Na2HPO 4 10'H20 ,36 66.8 Chemical.'Rubber CaCl 2 6 H20 29 40.7 Publishing Co., Cleveland, Ohio f As clear from the Table, in most cases the malting points noticeably exceed the level of physiologically comfortable temperatures In all the cases the latent melting heat of the salts is not high and enables a small amount of heat per unit of the accumulator workingi substances (about tens kcal/kg mass) to be stored.

As the prototype EP 0,034,710 has been selected which discloses a composition for heat accumulation close to the claimed one. In the cited Patent the salt crystallohydrates, in particular CaC1 2 6 H 2 0'are distributed in a hydraulically hardening ceramic (cement) matrix.

According to the prototype, the cement matrix'is a porous body formed as a result of hydrolysis of cement particles of S3 4 1 relatively large sizes (about 10 -10 nm) forming interparticle capillaries of the same order Of sizes, and therein salt macroparticles also of the same sizes are crystallized. Having such sizes of pores and particles the-cement matrix keep the salt melt (prevents displacement) due to the capillary forces, however doe not affect the working heat-accumulating substance properties.

Insofar as this is a typical example of a'phase change accumulator (PCM), advantages and disadvantages thereof are characteristic for a great number of patents based on this *principle.

An accumulator is an obligatory element of any energy system wherein generation and consumption of energy resources are,.not synchronized (see W. Twidell, A.D. Weir, Renewable ing relation ts >t >t is always valid for this system. Depending on the purpose of a heat accumulator, it is characterized by a numnber'of properties: 1. Accumulation temperature. In a first approximation it may be assume that the lower the temperature (ta) the higher the accumulator quality (the priice is lower and the accessibility of heat being accumulated Is higher). However, insofar as ta t, the characteristics of the heat consumers should be taken into account. In view of a great variety of such consumers, t a is to be a controllable parameter. Of a special interest are accumulation system with an operating temperature of about 20 0 C, close a physiologically'comfortable one for a human being. Such accumulators can serve as a basis for devices combining functions of a conditioner (cooling air at a temperature over the optimal one) and a heater at a temperature below the optimal one. And in this case the excess heat stored by an accumulator when cooling air, is realized for its heating.

*pecific energy capacity of an accumulator is also its main characteristic. The amount of heat stored per unit of volume (or mass) of an accumulator substance defines the operating cycle duration, dimensionsi and the energy capacity of the apparatus.

3. Time of heat storage. Insofar as natural (climatic) periods of superoptimal and low temperatures are separated in time, it is necessary for an accumulator to be able to keep the stored heat for a long time (hours in case of a daily cycle of operationand many days in case of a seasonal cycle of operation).

4. Stability, non-toxicity, cost. Essential requirements td the accumulator substances is their stability in case of a multicycle operation, non-toxicity, availability, and alow cost.

The combination of these requirements makes it possible to evaluate both the present state of the :art and the claimed technical solutions.

Considered herei;relow are results'attained according to the prototype and similar developments from the point ofv-iw S" 1 Arr of the above-mentioned properties of heat accumulators.

1. In heat accumulators based on PCM-systems the problem of temperature control of phase change (t has been successa fully'solved. For that purpose mixtures of salts forming eutectics were employed. For example, according to the prototype it is a mixture of Na2SO 10 H20 and NaCI H20. Ba changing the ratio of components in the mixture it is possible to vary t a from +7 to +220C.

2. As shown in the Table above, the latent heat of crystallohydrates melting is rather low (tens of calories per gram) which markedly increases the amount of the required heat-accumulating material and defines the dimensions of heat-accumulating systems.

3. Another consequence of the low energy capacity of conventional PCM materials is a restricted time of storing the accumulated heat. The real time of heat storing is defined by the speed of PCM cooling which depends on the amount of heat accumulated in the material and the heat isolation efficiency.

In view of the limited'character of both these factors, the duration of heat storing in the accumulator cannot be long.

Accordingly, in terms of the 2 main indices (energy capacity and time of keeping the stored heat) heat-accumulating materials based on PCM do not meet the main requirements. And it is because of these very reasons that a wide practical use of many PCM-systems is limited.

It should be noted here that these disadvantages are caused by the very principle of PCM-systems action and cannot be eliminated by some structural improvements of conventional accumulating systems.

For solving this problem it-is necessary to substantially increase '(about an order of magnitude) an endothermal effect' when accumulating heat. Any endothermal effect is defined by breakage of solid-phase substance particles bonds. Its value depends on the energy of these bonds. In case of PCM-systems there occurs the breakage of most weak intermolecular bonds resulting in a low latent melting heat.

.'To substantially increase the amount of heat being accumulated, it is necessary to pass to breaking strong intramol-.., k o :TI 5 cular bonds, for example, dehydration (partial or complete re,moval of chemically bonded water from salts crystallohydrates) (Table 1).

'The,preerit ,invention is directed to stating and solving a problem'of a radical improvement of heat-accumulating materials: an'essential increase (order of magnitude) of'the energy capacity while increasing the time of'storing the.accumulated' heat.

Given hereinbelow is the description of the problem solution the creation of novel systems based on chemical conversions of'substances and obtantion of the ddsired materials cal- S' led'as chemical heat accumulators, CHA.

In the CHA-system working substance a process of a salt chemical decomposition is effected. For instance, in'case .of CaCIl 6 H20 this reaction is: 2 2 SCaCl 6H CaC12 2H20 '410 q.

The decomposition process is endothermal. Thereat 'consumption is associated with water splitting off and subsequent i evaporating. It is, naturally, proportional to the numberof water moles being splitted off, the endoeffect per mole, and'a number of a working substance moles in volume or weight unit of CHA. For CaC1 2 6H 2 0 this vjalue is readily found.

The endoeffect, the change, of a crystallohydrate formation heat per mole of H 2 0, is equal on the average, in terms of the cited data, to 74 kcal/mol.H 2 0. Insofar as the own heat of water formation L H H 0 -58 ]cal/mol is also involved here, just, the'difference of these values 74-58 kcal/mol 16 kcal/ mol, i.e. the interaction (binding) energy of water molecule in.the ciystallohydrate structure /Ca(OH 2 6 is to be taken into account. When removing thei splitted off water, 9 kcal, evaporation heat of' a water mole, should be added to this value: 16 9 25 kcal/mol.

The decomposition of/each mole '(about 220 g of.CaC1l 2 6H 2 0) is accompanied by isolation 'of 4 mol of water,' thereby giving the total heat effect 25 x 4 =100 kcal/inol of CaCl 6 H 2 Accordingly, the potentialities of storing heat of CHA 5Zystems exceed, at least, by an order of magnitude those of te i I 6 conventional PCM-systems (see the prototype).

The dehydration generally occurs at temperatures over the melting points. Thus the'reaction CaC16 6H2 0 CaC12 4H 2 0 2H 20 occurs in the temperature range of 31 to 45

O

C which markedly exceed the working temperatures level of a heat accumulator.

To solve the stated problem, it is necessary to substantially decrease'the chemical decomposition temperature of thermolabile compounds such as salts crystallohydrates.

According to the present invention this is attained by using so called "size effects",'the change of structure and properties of crystalline solid substances when dispersing to microscopic sizes.

It is known in the art that for macroscopic particles wherein the number of atoms n C-D such thermodynamic characteristics as melting point and vapor pressure are constants (T=const at P=const), This rule is infringed when changing 5 the particle sizes, for example to D 10 cm (100 nm). The most reliable data was.-obtained for changing melting points depending on particle sizes. At small particle sizes, such as iC< 10 nm, this dependence becomes strong and substantially linear (see, for instance, N.N. Seling, SSP 7, No. 3, 881 (1965). Given hereinbelow is an analytical expression deduced on the basis of experimental data for the dependence of the melting point on a particle radius R: T T ex p T 2 R o RQ o RQ wherein T is the melting point of a macrocrystal: (R C/3 J is the coefficient of surface tension; _Qis the atomic volume; Q is the latent melting heat.

This analytical expression is derived from the Thomson (Kelvin) fundamental equation: kT o defining the excess pressure over a drop (particle) of a final size. (see Ya. E.Geguzin, Physics of sintering, "Nauka", M.

K Y c RA41i '5IVi 0 7 1967). The physical sense of the' above-mentioned changes of structure and properties of small particles can be interpreted in the first approximation so that a portion of energy spent for dispersing (formation of small particle surface) is accumulated by their three-dimentional structure. This is obvious enough from the fact that in a microparticle a relative portion u rface atoms exhibiting an increased mobility and free energy is high. From the same theoretical relations well experimentally supported it follows that in a wide range of particle sizes (from about 100 nm to 5 nm) "entropic" changes (melting temperature decrease, vapor pressure increase of a substance prevail, whereas "enthalpic" effects such as increase of interatomic spacings or decrease of heat of substance formation manifest themselves only at the particle sizes of about 1 to nm s ee, for example, the above-cited monograph by Ya.E. Geguzin). We have propounded a hypothesis in terms whereof for any thermolabile crystalline materials in a size range of from to 10 nm there is observed an essential dependence of a chemical decomposition temperature on particle sizes at,approximate constancy of heat of formation: t AH(R) ='const.

Experimental investigations carried out using physical methods (X-ray analysis, calorimetry) have shown that such dependences are actually realized, for example, for the crystallohydrate CaCl2 6H20 in the range of the salt particle sizes: -7 -5 D 10 to 100 nm (10 7 to 10 cm).

Given hereinbelow'are the main results of changing the decomposition temperature of CaCl 2

&H

2 0 as a function of crystal sizes D (nm): Particle size Salt decomposition D, nm temperature, °C 1..Reference Ca Cl 6H 0 100 29 2.,,Sample No. ,1 50 3. Sample No. 2 10 13 The investigations have shows that the decrease of a salt par.ticles size is accompanied by the change of not only the.-- 1 S8 the temperature but also the decomposition mechanism of a crystallohydrate. It is known from the literature that the crystallohydrate CaC12 6H 2 0 in the temperature range of from 31 to 0 C decomposes to CaC1 2 4H 20 with splitting off 2 molecules of water, then in the range of ifrom 50 to 600C transition to CaC2 2H 2 0 occurs with splitting off 2 more moles of water.

The process is reversible: under the conditions of temperature lowering'and humidity increasing CaC2 2H20 is fully converted into the starting hexahydrate QaCl 2 6H 2 0. This working process was used as a basis for developing the presently claimed CHA-* material.

Wheh realizing the process, natural difficulties arise: it is practically impossible to handle microscopic size particles,(less than 100 nm).

Moreover, such energy-rich non-equilibrium systems are readily caked to giv macroparticles (R C To solve this problem, we have used a step of placing salt.particles into a porous ceramic matrix. The porous matrix'used by us, for example made of silica (silica gel)', as distinct from the prototype, has pores of the required sizes (10-50 nm) wherein salt particles of the same (microscopic) sizes are crystallized.

Accordingly, per 1 kg of a working substance of a crystallohydrate, such as CaCI2 6H20 having particle sizes D 100 nm, the energy store is about 450 kcal/kg salt. When using silica gel with pore volume of about 1 cm 3 i.e. 0.5 1 pores per 1 1 of bulk volume, and the crystallohydrate density of 1.7 g/cm 3 the energy store per 1 1 of the bulk volume of the CHA materialgranules is 400 kcal/l.

In view of'a great numberof conventional compounds of a crystallohydrate type, the selection possibilities are defined by the following factors: For a great number of conventional crystallohydrates the enthalpy of formation per mole H20 is approximately constant and agrees with the binding energy'change in the range H 16 2.kcal/mol H 2 0; The most important requirementto the working substance is its stability under multiple hydration/dehydration cycles.

The main limitation here is associated with the salt partial?- I I J R A 3 r 1 9 9hydrolysis possibility when decomposing the crystallohydrate.

Such stability is inherent, first of all, in strong acids and bases. When transiting to elements forming amphoteric oxides and hydroxides, the isolation of acid occurs. The employment of salts of thermolabile acids (nitric, acetic, oxalic, etc.) is also limited; Non-toxicity of a salt; Availability.

In terms of the sum of the above-mentioned requirements, CaC12 6H20 is preferably useful as characterized by a thermochemical stability, high energy-storing of a substance due to isolation of 4 moles of water per mole of salt, non-toxicity, and availability (calcium chloride is a main by-product of the soda production by the Solvay process the utilization whereof is a problem).

In practice as a matrix for the selected cryst.-llohydrates use is made of porous substance wherein the prevailing pore volume portion is presented by pores of the required sizes less than 100 nm). To such Smaterials belong porous glasses and similar ceramic 3 materials, porous metals and polymers, active carbon, and Sother fine-porous matrixes.

For the realization of potentialities of CHA-systems it is highly important to use so-called "open systems" wherein the exchange with the environment both as per heat and substance (moisture) takes place. i By their purpose and significance any heat-accumulating systems are open as concerns heat, insofar as the heat exchan- Sge with the environment is an obligatory condition for any application of heat-accumulators.

30 If a heat accumulator is charged from a humid ai: 100%) by cooling air from 20 to 10 0 C, the amount of heat taken away from dry air under cooling by 10 0 C is 1.5 times less than the amount of steam condensation heat when lowering the temperature by the same 10 0 C. Accordingly, in case of humid air the main energy potential is associated with the moisture contained in that air. ,The presence in air.at temperatures over O~OC'of considerable aAounts of steam (moisture evaporation is 4 Z the main way of utilizing the :solar energy in the nature) and I PP^ J 4 L I!i 10 a relative simplicity of controlling the air humidity define a specific efficiency of using hygroscopic thermosensitive materials, in particular salt crystallohydrates disclosed in the instant application, as working substances in the heat-accumulating systems. To realize the "open" ,moisture exchange processes between CHA-materials and a gaseous atmosphere it, is essential that the pores wherein the thermosensitive hygroscopic material is put be "open" and easily communicating with the gaseous (air) atmosphere.

S The heat energy is stored in CHA-materials in the form of potential energy of a reactive Ichemical system. As distinct from PCM-systems, CHA-materials can have any temperature (generally it is equal to the ambient temperature). However, even at t t of.the environment no "self-discharge" of CHA-materials can occur. Both the accumulatidn and liberation of heat are associated with changes of the'system chemical composition.

Therefore the liberation of the accumulated heat will not take place until there is an efficient contact between the material and the reagent, steam. In the absence of such a contact the accumulated energy can be stored in a CHA-system for an unli-' mited period of time.

The realization,.f the CHA-systems s-~'ves 2 main problems limiting a wide use/of in prinqiple promising systems for accumulating heat energy based on salt crystallohydrates: the increase of energy capacity and time of heat storing.

Thus, the claimed CHA-materials based on CaC1 2 6H20 crystallohydrate are characterized by very high energy capacities as to heat accumulation, their working temperature levels being close to the optimal ones (comfortable temperature).

Such a unique combination of properties (high energy capacity at low temperatures) conditions a rather wide spectrum of fields of application of the CHA-materials in conventional and novel technologies, when there, is required a rapid and efficient heat removal from air or some parts being heated under Working conditions.

S The main effect on which the proposed process is based, i I GH&CO REF: P22735A/COS 1

I'

11 lowering the substance decomposition temperature when decreasing the salt particles sizes to microscopic ones (less than 100 nm) slightly depends on both the salt nature and the porous matrix nature. Of an essential significance is only the absence of a specific chemical interaction between the thermosensitive substance and the matrix material. Thus, for example, the opportunities of using zeolites, wherein the ion exchange process between the matrix and a thermosensitive material is very active, are limited.

The direction and rate of the main working process of a CHA-material are described by the following reversible thermochemical reaction: CaC1 2 6H20 CaC1 2H20 4H20 q.

The equilibrium state in the system depends not only on, the temperature, but also on the ambient humidity. Therefore, the' air humidity is the second important factor in controlling heat accumulation andremoval in HCA-materials. Using a CHAmaterial according t6 the present invention there has been developed adevice intended for. maintaining in a closed area a comfortable (optimal physiological) temperature, generally 2 0 C. Such a device which combines functions of a conditioner and a heater is called by us as "Conforter". The Comforter action is based on a reversible thermochemical cycle of storing and consuming a low-potential heat energy in a chemical heat accumulator (CHA-system). The absence of an autonomous energy source, such as a thermocompressor in a conditioner restricts the Comforter capabilities. This energy-storing technology is intended*for temperature control-in small premises (about 50 m3), and in case of closed spaces on the absence of an inflow of hot or cold air from the outside. However, such advantages of the Comforter as simplisity, safety, minimum energy consumption, and ecological purity (absence of freon) make them competitable for mass consumers. The unique property of the CHA-materials, the capability of accumulating a large amount of heat (up to kcal/cm 3 at a temperature close to room one considerably widens the scope'of pdssible applications of such substances in the technology. In the instant application along with the main purpose:, i.e- e R A 12 air temperature control in premises (Conforters) there are proposed 2 pon-traditional purposes of using heat-accumulating materials: Cooling parts and device which are heated under working conditions. This problem is urgent for a wide range of technical systems, first of all for elements of radio electronic apparatus in electronic computers and various electronic equipment, as well as for protedting building constructions in case df,fire.

S 2. Another non-traditional but logically following from the CHA-materias unique properties trend-in the application thereof is for extinguishing fire, for suppressing a.non-controllable burning process.

SA CHA-material capable of adcumulating about 1 kcal per gram in the temperature range of from 20 to 400C is an effective antipyrene a minimum amount whereof can extinguish any fire.

Hydrated forms of zeolites capable of effective heat absorption under heating to temperatures of 80 to 100°C and over and are very close to the CHA-materials in their.properties for such uses liberation the absorbed moisture to the environment.

Accordingly, for protecting articles and building constructions against overheating, as well as for fire extinguishing, according to the present invention, it is also possible to use hydrated forms of zeolites or mixtures thereof with CHA-materials. In a nuAmer of cases it is preferable in view of cheapness of natural zeolites.

The process for producing CHA-materials is based on a number of traditional operations: impregnation of the matrix with a salt' solution, removal of the solvent while crystallizing the salt crystallohydrate.

The other purposes and advahtages of.the instant invention will be illustrated by the following Examples of specific embodiment thereof and the Figure showing fragments of radiograms obtained for samples produced according to the instant invention.

The position of lines correspond to the synthesized phase of CaCl 2 6H 2 0. Owing to small sizes of crystallites (about 100 A) i the diffraction lines are broadened.

ii *All l 7 1

^T

.p i I- I i J I _i.

13 AHmel 4Hdec CaC 2 6H 2 0 T T T 290C AH Tmel. A H HIH CaC1 2 6H 2 0 H forCaCl AH' for. 2 for. 2 dec. -74 kcal/mol AHdec. Hfor. 2 .'Hbin.

A H H AH H O bin. dec. for. 2 74 58 16 kcal/mol 16 kcal/mol 9 kcal/mol Ievap.) 25 kcal/mol.

Versions of the invention embodiment.' Given hereinbelow are Examples A and B illustrating the CHA-material preparation.

EXAMPLE A 1 kg of granulated.,silica gel (granules of 3-7 pm) having about 1 cm3/g pores of 10 to 15 nm in diameter was impregnated with 1000 ml of 140% CaC1 2 solution. Then the impregnated mass was dried and calcined at a temperature of 2400C till the complete solvent (water) removal and formation of anhydrous salt in; the matrix pores. Then after cooling the material was hydrated to the crystallohydrate of CaCl 2 6H 2 0 salt by holding in a damp atmosphere, with the process course being controlled in terms of sample weight change.

EXAMPLE B 1 kg of silica gel powder dispersed to 1 to 100 pm having a 3 total volume of pores of 2.8 cm /g with a.prevailing pore diameter of 10 to 15'nm, was impregnated with 2800 ml of 40% CaC12 solution, then, following the procedure of Example A, the impregnated mass-was fied and calcined. Thereafter the mass was reimpregnated with the same solution as to moisture 'capacity; redried, calcined, and hydrated in a damp atmosphere till obtaining a salt crystallohydrate of the CaCl 2 .6H 2 0 composition.

The fragments of radiograms presented in the Figure correspond to sampels of the materials obtained in Examples A and B.

u n rmoensinve working substance which is a hiygrosc. ic substance capable of reversi" le" presses of de.hyat.

hydration. A heat accumulating material is intended for use as a agent for cooling and heating of a gaseous (air) medium an agent for thermostatic conditioning and protection against heating of articles or construction structures, for examle elements of radioelectronic devices, as well as a fire suppressing means.

14 They:show that crystals of the CaC12 6H 2 0 phase were actually formed within the.matrix pores.

Examples 1 to 4 given hereinbelow illustrate the compositions with various sizes of the CaCI2 6H20 salt crystalline particles '51 and different degree of the matrix pores filling with the working S substance.

EXAMPLE 1 A heat-accumulating material comprising CaCl 2 6H 2 0 crystals with an average size of'50 nm. The material comprises 400 g (about 2 ml crystallohydrate per 1 1 bulk volume of the matrix) (granules of 3-7 mm in diameter). According'to the calculated estimation (see above) energy storing of such an accumulator is about 200 kcal/l bulk volume or about 300 kcal/1 actual volume, without account of voids in the stack of granules.

The experimentally determined cdnversion temperature ta 1°C at a relative humidity EXAMPLE 2 A heat-accumulating material consisting of CaC12 6H 2 0 with a particle size of 10 to 15 nm. The material 400 g about 2 mol crystallohydrate per 1 1 matrix bulk volume.

The energy capacity of this heat 7 accumulating material is also 200-300 kcal/l of the bulk or actual volume of the material, respectively. The temperature of salt decomposition (at a relative humidity of the environment 65%) 'is 13.5 0

C.

EXAMPLE 3 .A heat-accumulating material consisting of CaC12 6H20 crystals of a size D 10 to 15 nm. The temperature of salt decomposition, as in Example 2,.is 13.50C, however the salt content is 800 g per 1 1 bulk vplume. Accordingl t1e energy capacity of 1 1 .of the material is 400 to 600 kcal/l.

EXAMPLE 4 A, heat-accumulating material similar to that described in Examples 2 and 3, but distinct in that instead of a granulated 3 silica gel with a limited total' porosity (about 1 cm3/g) use is made of a high-porous powder with pores of the same size but the 3 total'porosity of 2.8 cm3/g. Due.to a considerable increase of pordsity that is a powdery heat-accumulating material comprising 1.53 kg CaC12 6H20 per 11 volume. At the same accumulation SL 0: 11rC L aL L 1 2 3 4 S 40 15 temperature (13°C) the energy capacity of the sample 'is 700 kcal/l.

Given hereinbelow are Examples 5 to 8 illustrating the use of CHA-systems for the air temperature control.

EXAMPLE To a vertical cylindrical heat-insulated reactor charged S with 11 of a CHA-material in the form of granules 3 to 7 mm with energy capacity of about 500 kcal/1 bulk volume (see Example 3) was fed dry air in an amount of 1 m3/h with steam content of less than 1 g/m 3 At the inlet temperature of dry air of to 200C in consequence of adiabatic!cooling at the crystallohydrate decomposition, the air temperature decreased in the CHA layer, and at the reactor outlet was 0 +5 0 C (At -15 0

C),

3 the air .moisture content increasing to 4 which is close to 100% at t The practical importance of such a simple and ecologically pure method of obtaining-domestic cold .is obvious (the temperature range to +50C corresponds to the operation temperature level in a domestic refrigerator). It is expedient to use highly humid cboled air-for storing vegetables and other similar products. As distinct from the refrigerator, the presently'described system requires no freon and reduces energy consumptioh 10 times (instead of a compressor for freon, just a low-power fan is required for drawing air through the CHA-material layer). Additional'energy consumption may be associated withobtaining dry gas, however effective technical solutions are known for this too.

EXAMPLE 6 The procedure of/Example 5 was repeated, except that 1 m3/h air having t nit.= 30°C, P =50%,.bulk speed 1000 1/h was blown through the granules of GHA-material. When contacting air with the granules, the crystallohydrate dehydration with heat 'absorption occured. Due to the-heat exchange with the granules the air was cooled to +200C while the absolute humidity increased by 2 g/m 3 The experimental working.cycle time '(about 200 h) was rlose to the calculated one at the given energy capacity (500 kcal/1 granules).

EXAMPLE 7 SThe procedure of Example 6 was repeated, except that the S air flow was increased to 2 m3/h (bulk speed 2000 The 1 I i I I I I I II chemical heat accumulator ensured for 200 h the air cooling from +25 0 C at the inlet to +20 0 C at the outlet.

Examples 5, 6 and 7 illustrate the accumulator charging cycle (dehydration) with heat absorption. Example 8 describes the reverse process.

EXAMPLE 8 The same reactor as in Examples 5-7 was used, however the CHA-material granules charged into the reactor contained the working substance in a dehydrated form (CaCl 2 2H20). When pas- SI sing damp 50 to 60%) air with the initial temperature of 0 C, the hydration (discharging) of the accumulator occured.

The temperature of air at the outlet was +25 0 C, the absolute humidity was lowered by 1 g/m.

Examples 9 to 12 illustrate'the main ways of solution and the results of using such a method.

The process was studied on a model laboratory apparatus, a part to be protected against heating (flat metal plate) was put into contact with an electrically heated plate of the same size (6 x 6 36 cm When passing current through the latter plate (0.05 W/cm 2 s) it was heatled and the heat was transferred to the test plate of the same area and 2 mm thick. On the opposite side of the test plate there was applied an epoxy layer containing as a filler disperse CHA-material powder (less than 100 such a's that described pn Example 4 of the present application.

EXAMPLE 9 A control test wherein the resin coating and CHA-material were not applied. Upon passing electric current for 1 h the lower plate temperature attained 95 0 C (heating up 95-20 75 0

C).

EXAMPLE The procEdire of/Example 9 was repeated, e cept that onto a free (non-.contacting with the electric heater) side of the plate there was applied a layer of CHA-material powder'slurry in epoxy of 1 mm in thickness (about 0.1 cm 3 powder per cm2 plate). Upon passing electric current for 1 h, the test plate retained the temperature close to the initial one (room), 20 to 3.0 0

C.

EXAMPLE 11 .The procedure of Example 10 was repeated, except that the

E-

Iafir thr wa apidalyroCH-teialpwe'lryi px Considered hereibelow are results'attained according to the prototype and similar developments from the point ofiw 17 heat-accumulating coating thickness was increased to 3 mm (about 0.25 cm powder per 1 cm 'plate). Such coating ensured the temperature retention at 20 to 300C for 2 h.

EXAMPLE 12 The procedure of Examples 10 and 11 was 'repeated,'except that,the heat-accumulating coating thickness was increased to m 3 2 mm (about 0.4 cm powder per 1 cm plate surface). The coating ensured the plate temperature retention in the range of from, 2 to 400C for 4 h.

As follows from Examples 9 to 12, the'use of the syhthetic resi'n with the filler, CHA-material powder, is an effective method for heat'removal from metal and other surfaces being heated under working conditions, while the effective heat accumulation by the filler, CHA-material powder, ensures the retention of temperatures at a much lower level than the temperature of polymer binder destruction (about 1000C for epoxy).

The compositions employed in Examples 10 to 12 consisted of a disperse (less than 100 p) CHA powder and epoxy. The high adhesion between the resin and silica, the CHA matrix porous substance, makes it possible to prepare compositions with a high content (up to 80% by weighit) of the heat-accumulating material. The employment of epoxy in such compositions is quite justified, insofar as it cbmbines valuable properties such as high electric resistivity and satisfactory thermal conductivity which are necessary for heat transfer from the heated surface to the CHA-material powder.

The use of CHA-materials for fire extinguishing is illustrated by Exaples 13 to EXAMPLE 13 Into a flat cylindrical vessel of 5 cm in diameter and 1 cm high were fed 2.5 cm. of kerosene (layer of about 1 mm) and set on fire. Under thd selected conditions the time 'of kerosene I. burning out was about 200 s which corresponded to thb calculated heat liberation of 125 cal/s or"2000 cal/8 s. The bu'rning was stable, and the sample burning out time-was reprodusible of' 200 10 s in the repeated runs series.

EXAMPLE 14' The procedure of Example 13 was repeated, except that 50 s

T

.'To substantially increase the amount of heat being accu- Imulated, it is necessary to pass to breaking strong intrarol-..

after setting fire, the kerosene stable flame tongue was spread Swith''a CHA-material powder having a high energy capacity (see Example The'fire was completely extinguished upon feeding about 1 g powder (feeding time about 10 However in view of the powder disperse state, a considerable portion thereof was brought out, of,the burning area and deposited on the periphery (outside the vessel). This apparently increases the consumption of antipyrene..

EXAMPLE The procedure of Examples 13 and 14 was repeated, except that the CHA-material was used in the form of fractured particles (fraction of 1 to 3 mm). Such particles had a sufficient mass to penetrate into the burning kerosene area. The CHA-material consumption was about 0.3 g, which apparently agreed'with the actual consumption of antipyrene when extinguishing fire.

Accordingly, to effectively employ the CHA-material for fire extinguishing, it is necessary to ensure feeding thereof to the burning surface at a rate of about 0.3 kg/1000 kcal liberated heat.

It should be stressed that the CHA-materials possess the above-mentioned properties only in the discharged (hydrated) form. Therefore it is necessary to ensure such storing conditions (temperature, tightness) which prevent non-controllable (spontaneous) decomposition (dehydration).

The presently claimed material is advantageously distict; from many similar substances in:efficiency, compactness, and' no liberation of any toxic substances under heating.

The most efficient method of using a solid-phase antipyrene of the proposed type is a mechanical introduciton thereof onto ,the burning material surface, the least stable fire area where minimum actions: may give the most considerable .result. According to Examples 13 to 15 the antipyrene dose required for fire 2 extinguishing is 0.15 to 0.5 kg per 1 m burning surface, which is close to the best kinds of antipyrene known in the world practice.

Apparently the use of the novel antipyrene is most efficient for fire extinguishing in almost inaccessible regions, for C' example forest fires, as well as fires on transport.

C- ,i "1 w wt l l w wv l X N 1

Claims (9)

1. 2. To solve a temperature control problem on a qualitatively new basis, which is especially actual for high-speed computers and. a wide range of electronic devices. high-efficiency compact 2 ;hea;t removal systems made of polymeric resin with a CIIA. filler S can markedly simplify the design and increase the reliability of electronic devices. The use of the CIIA materials for fire extinguishing 'makes it possible to dratically decrease the need in antipyrenes, 2, which'is especially actual inc &se of forest fires in hard- S -accessible regions, as' well as fires on transport'. SWHAT IS CLAIMED IS: 1. A heat-accumulating material comprising a thermoinert ".matrix and a thermosensitive working substance, c h a, r a c t e r i z e d in t h a t said matrix is an open-porosity material, and said working substance is alhygroscopic subStance capable of.reversible dehydration/hydration processes. 2. A heat-accumulating material according to claim 1, characterized in that said working substance is in the form of crystallohydrates capable of changing their chemical composition with temperature, such as CaC1 2 6H20, as crystals of less than 100 nm in size.
2. 3. A heat-accumulating material according to claim 1 or claim 2, characterized in that said matrix is in theRA S/ I 2LL 0 w defining the excess pressure over a drop (particie) 0z c size. (see Ya. E.Geguzin, Physics of sintering, "Nauka", M. SRA -T form of granulated or powdery porous particles of 1 to 5000 pj in size of inorganic, polymer, carbon, or metal materials having open pores, preferably of 10 nm in diameter, such as silica gel.
3. 4. The use of a heat-accumulating material according to any one of claims 1-3, as a cooling and heating agent for gas/air atmospheres. The use of a heat-accumulating material according to any one of claims 1-3 as a thermostating agent and protection against heating of articles or building constructions, for example elements of radioelectronic devices.
4. 6. The use of a heat-accumulating material according to claim 5 in mixture with zeolite.
5. 7. The use of a heat-accumulating material according to any one of claims 1-3 as a means for fire extinguishing.
6. 8. The use of a heat-accumulating material according to claim 7 in mixture with zeolite.
7. 9. A heat-accumulating material substantially as herein described with reference to any one of Examplea 1 to 4. The use of a heat-accumulating material according to claim 4 and substantially as herein before described with reference to any one of Examples 5 to 8.
8. 11. The use of a heat-accumulating material according to claim 5 and substantially as herein before described with reference to any one of Examples 10 to 12.
9. 12. The use of a heat-accumulating material according to claim 7 and substantially as herein described with reference to any one of Examples 13 to Dated this 12th day of April 1995 INSTITUT KATALIZA STBIRSKOGO OTDELENIA ROSSIISKOI AKADEMII NAUK and AKTSIONERNOE OBSCHESTVO ZAKRYTOGO TIPA EKOTERM By their Patent Attorney R GRIFFITH HACK CO 7-c, F S:22735A i J b .ne investiga--unrii 1Idvt 61uwb LIUC L Loe UtjLt-eCe a. o particles size is accompanied by the change of not only the-" i :i 21 HEAT-ACCUMULATING MATERIAL AND USE THEREOF ABSTRACT Disclosed is a heat-accumulating material comprising a thermally inert matrix which is an open-porosity substance, and a thermosensitive working substance which is a hygroscopic substance capable f .reversible dehydratioh-hydration processes. A heat-accumulating material according to the present invention is intended for the use as a cooling and heating agent for a gas/air atmosphere, a thermostating agent, and as protec- tion against heating of articles and building constructions, for example radio-electronic devices, as well as as a means for fire extinguishing. RI c: I II