JPH1135931A - Cold storage material utilizing latent heat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cold storage material utilizing latent heat comprising an aqueous solution of sodium chloride which is protected from supercooling phenomenon, has a freezing point approximated closely to the phase transition temperature of the aqueous solution of sodium chloride as much as possible and is also free from deactivation phenomenon by incorporating graphite into the aqueous solution of sodium chloride. SOLUTION: A cold storage medium employed is an aqueous solution of sodium chloride. The concentration of sodium chloride is not limited so far as it forms an aqueous solution and is preferably 5-30 wt.%, more preferably 15-27 wt.%. The purity of sodium chloride is preferably 99% or higher. Graphite employed as a supercooling preventing agent has a purity of 99.0% or higher and there can be exemplified natural graphite (graphite, diamond, etc.), artificial graphite (including flake graphite). The amount of graphite employed is 0.1-10 pts.wt. based on 100 pts.wt. of an aqueous solution of sodium chloride. A water- absorbent resin can be added if required. The cold storage material utilizing latent heat exhibits a phase transition phenomenon preferably at -40 deg.C-2 deg.C.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は塩化ナトリウム水溶
液を蓄冷媒体（主剤）とする潜熱蓄冷材に関する。さら
に詳しくは、塩化ナトリウム水溶液を含む蓄冷材に過冷
却防止剤として黒鉛を加えた潜熱蓄冷材に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent heat storage material using an aqueous solution of sodium chloride as a refrigerant (main agent). More specifically, the present invention relates to a latent heat storage material in which graphite is added as a supercooling inhibitor to a cold storage material containing an aqueous solution of sodium chloride.

【０００２】[0002]

【従来の技術】余剰電力の利用を目的として電力エネル
ギーの効率的分散貯蔵法が、現在種々検討、開発されて
いる。例えば、熱媒体となる物質の融解、凝固などの相
変化に伴う吸収熱を利用した潜熱蓄冷材の開発もそのひ
とつである。蓄熱材とは、熱または冷熱を物質内に蓄積
し必要時に有効に熱の出入りを利用する材料である。特
に、主に物質の相変化に伴う発熱／吸熱反応を利用した
ものを潜熱蓄熱材、さらに特に予め冷熱を蓄熱し必要時
に放冷する場合を潜熱蓄冷材と呼ぶが、蓄熱材、蓄冷材
の明確な区別はない。潜熱蓄冷材のうち、無機塩、無機
水和塩などの無機物系材料を蓄冷媒体としたものは、有
機物系材料に比べて熱伝導率が大きい、潜熱量が大、体
積変化が小さい、不燃性であるなどの利点があり、なか
でも塩化ナトリウム水溶液は、さらに毒性がない、低反
応性、入手容易、適度な溶解度があり、共晶温度が冷凍
食品保存温度に近いという利点もある。従ってこれらの
蓄冷材は、食品の冷蔵、配送時の保冷、化学・医薬品の
冷蔵、食品工場などの冷却工程に特に好適に使用するこ
とができる。2. Description of the Related Art Various efficient storage methods of electric power energy have been studied and developed for the purpose of utilizing surplus electric power. For example, development of a latent heat storage material utilizing absorption heat accompanying a phase change such as melting and solidification of a substance serving as a heat medium is one of them. A heat storage material is a material that accumulates heat or cold in a substance and effectively uses the flow of heat when necessary. Particularly, a material utilizing heat generation / endothermic reaction mainly due to a phase change of a substance is referred to as a latent heat storage material, and more particularly, a case in which cold heat is stored in advance and then cooled when necessary is referred to as a latent heat storage material. There is no clear distinction. Among the latent heat storage materials, those using inorganic materials such as inorganic salts and inorganic hydrated salts as the refrigerant storage medium have higher thermal conductivity, larger latent heat, smaller volume change, and nonflammability than organic materials. Among them, an aqueous solution of sodium chloride has further advantages that it is less toxic, has low reactivity, is easily available, has an appropriate solubility, and has a eutectic temperature close to the frozen food storage temperature. Therefore, these regenerative materials can be particularly suitably used for refrigeration of foods, cold preservation at the time of delivery, refrigeration of chemicals and pharmaceuticals, and cooling processes in food factories and the like.

【０００３】[0003]

【発明が解決しようとする課題】しかし塩化ナトリウム
のような無機物系材料を蓄冷媒体とした潜熱蓄冷材は、
過冷却現象を起こすという問題がある。過冷却とは、物
質を冷却する際に液体から固体への相転移の温度を過ぎ
ても転移の現象が現れないことをいう。例えば、２３．
３重量％の塩化ナトリウム水溶液は相転移温度が−２１
℃であるにもかかわらず、実際には−３０℃付近まで温
度を下げないと相転移が起こらないことがある。すなわ
ち過冷却現象を起こすということは、実際利用しようと
する温度（蓄冷材の凝固点）よりさらに低温まで冷やす
ことのできる冷凍機を準備しなければならず、冷凍機設
備の費用がかかり、また低温運転による運転効率の低下
（１℃下がる毎に３％低下）によるランニングコストの
増大など、余分のエネルギーを必要とするという問題も
ある。However, a latent heat storage material using an inorganic material such as sodium chloride as a refrigerant storage medium,
There is a problem of causing a supercooling phenomenon. The term “supercooling” means that when a substance is cooled, the phenomenon of the transition does not appear even when the temperature of the phase transition from a liquid to a solid is exceeded. For example, 23.
A 3% by weight aqueous solution of sodium chloride has a phase transition temperature of -21.
Despite the temperature, the phase transition may not actually occur unless the temperature is lowered to around -30 ° C. In other words, to cause the supercooling phenomenon, it is necessary to prepare a refrigerator capable of cooling to a temperature lower than the temperature to be actually used (the freezing point of the regenerative material). There is also a problem that extra energy is required, such as an increase in running cost due to a decrease in operation efficiency due to operation (3% decrease every 1 ° C. decrease).

【０００４】この過冷却を緩和するために、凝固時に蓄
冷媒体の核となるような物質（過冷却防止剤）を添加す
ることが行われている。例えば特開平５−３３１４５７
号公報には、ＮＨ₄ Ｃｌ、ＮａＣｌなどの無機系の蓄熱
媒体にＤＢＰ吸油量１００以上のカーボンブラックを添
加することが開示されている。また、特開平２−９２９
８７号公報には硝酸カリウム、ケイ酸ナトリウム、炭酸
ナトリウム、硫酸マグネシウム、リン酸二水素アンモニ
ウムおよび塩化カリウムの各水溶液に、活性炭および／
またはグラファイトを含有した蓄冷材組成物が開示され
ている。しかし過冷却防止剤を含む蓄冷材は、（凝固剤
の融点＋３０）℃以上の温度にすると過冷却防止効果が
消滅する、いわゆる失活現象がある（WATANABE et al.A
CS Symp. Ser. D438(1990) p395参照）と言われてい
る。すなわち、蓄冷・放冷サイクルの途中で、何らかの
原因で蓄冷材温度がある以上になった次の蓄冷時には、
過冷却防止剤が有効に働かず、過冷却度が大きくなって
しまう現象が現れる。このようになった場合、一度再凝
固させた後、そのまま使用できなくなる場合もあれば、
続けて使用できる場合もある。[0004] In order to alleviate this supercooling, a substance (supercooling inhibitor) which becomes a core of the refrigerant storage during solidification is added. For example, JP-A-5-331457
Japanese Patent Application Laid-Open Publication No. H11-146, discloses that carbon black having a DBP oil absorption of 100 or more is added to an inorganic heat storage medium such as NH ₄ Cl or NaCl. Also, Japanese Patent Application Laid-Open No. 2-929
No. 87 discloses an aqueous solution of potassium nitrate, sodium silicate, sodium carbonate, magnesium sulfate, ammonium dihydrogen phosphate and potassium chloride containing activated carbon and / or
Alternatively, a regenerator material composition containing graphite is disclosed. However, the regenerator material containing a supercooling inhibitor has a so-called deactivation phenomenon in which the supercooling prevention effect disappears when the temperature is higher than (the melting point of the coagulant + 30) ° C (WATANABE et al. A).
CS Symp. Ser. D438 (1990) p395). In other words, during the cold storage / cooling cycle, at the time of the next cold storage in which the cold storage material temperature has exceeded the certain temperature for some reason,
A phenomenon appears in which the supercooling inhibitor does not work effectively and the degree of supercooling increases. In this case, once re-solidified, it may not be usable as it is,
In some cases, it can be used continuously.

【０００５】また、どんな過冷却防止剤を使用するかと
いう点に関しては、蓄熱媒体と同じような結晶構造・格
子定数をもつものが良いとも言う説もあり、逆に蓄熱媒
体と異質なものでも過冷却防止効果が高いものもあり、
特定の蓄熱媒体に対しどんな過冷却防止剤が適している
のかは試行錯誤しているのが現状である。[0005] In addition, regarding what kind of supercooling inhibitor to use, there is a theory that it is better to use a material having the same crystal structure and lattice constant as the heat storage medium. Some have a high supercooling prevention effect,
At present, what kind of supercooling inhibitor is suitable for a specific heat storage medium is trial and error.

【０００６】本発明の目的は、塩化ナトリウム水溶液を
蓄熱媒体とした潜熱蓄冷材の過冷却現象を抑制し、凝固
点を塩化ナトリウム水溶液の相転移温度にできる限り近
づけたものであって、かつ失活現象のない潜熱蓄冷材を
提供することにある。An object of the present invention is to suppress the supercooling phenomenon of a latent heat storage material using an aqueous solution of sodium chloride as a heat storage medium, to bring the freezing point as close as possible to the phase transition temperature of the aqueous solution of sodium chloride, and to deactivate it. It is to provide a latent heat storage material without a phenomenon.

【０００７】[0007]

【課題を解決するための手段】このような状況下、本発
明者らが種々検討した結果、黒鉛を塩化ナトリウム水溶
液の過冷却防止剤として使用した場合、特に有効に過冷
却を抑制する効果があることを初めて発見し、本発明を
完成させた。すなわち本発明は（１）塩化ナトリウム水
溶液および黒鉛を含む潜熱蓄冷材、（２）黒鉛が純度９
９％以上である上記（１）記載の潜熱蓄冷材、（３）黒
鉛の量が、塩化ナトリウム水溶液１００重量部に対して
０．１〜１０重量部である上記（１）または（２）記載
の潜熱蓄冷材、（４）−４０℃〜−２℃の温度範囲で相
転移現象の生じる上記（１）〜（３）のいずれかに記載
の潜熱蓄冷材、および（５） 塩化ナトリウムの濃度が
５〜３０重量％である上記（１）〜（４）のいずれかに
記載の潜熱蓄冷材に関する。Under these circumstances, the inventors of the present invention have conducted various studies. As a result, when graphite was used as a supercooling inhibitor for an aqueous solution of sodium chloride, the effect of suppressing supercooling was particularly effective. We discovered for the first time and completed the present invention. That is, the present invention provides (1) a latent heat storage material containing an aqueous sodium chloride solution and graphite, and (2) a graphite having a purity of 9%.
(1) or (2), wherein the latent heat storage material according to (1) is 9% or more, and (3) the amount of graphite is 0.1 to 10 parts by weight with respect to 100 parts by weight of the aqueous sodium chloride solution. (4) The latent heat storage material according to any one of (1) to (3), wherein a phase transition phenomenon occurs in a temperature range of -40 ° C to -2 ° C, and (5) the concentration of sodium chloride. Is 5 to 30% by weight of the latent heat storage material according to any one of the above (1) to (4).

【０００８】[0008]

【発明の実施の形態】本発明で使用する蓄冷媒体は塩化
ナトリウム水溶液である。塩化ナトリウムの濃度は水溶
液を形成する限り特に限定されない。なかでも５〜３０
重量％が好ましく、より好ましくは１５〜２７重量％で
ある。塩化ナトリウムが５〜３０重量％であると、凝固
および融解時の温度差が小さくなり、蓄冷・放冷温度が
一定に近くなり、蓄冷材として望ましいものとなる。塩
化ナトリウムの純度は特に限定されないが、通常９９％
以上が好ましく用いられる。BEST MODE FOR CARRYING OUT THE INVENTION The refrigerant storage medium used in the present invention is an aqueous sodium chloride solution. The concentration of sodium chloride is not particularly limited as long as an aqueous solution is formed. Above all, 5-30
% By weight, more preferably 15 to 27% by weight. When the content of sodium chloride is 5 to 30% by weight, the temperature difference at the time of solidification and melting becomes small, and the cold storage / cooling temperature becomes close to constant, which is desirable as a cold storage material. Although the purity of sodium chloride is not particularly limited, it is usually 99%.
The above is preferably used.

【０００９】過冷却防止剤として使用される黒鉛は、純
度が９９．０％以上のものが好ましく、例えば、天然黒
鉛（グラファイト、ダイヤモンドなど）、人造黒鉛（リ
ン片状黒鉛も含まれる）が挙げられる。The graphite used as the supercooling inhibitor preferably has a purity of 99.0% or more, and includes, for example, natural graphite (graphite, diamond, etc.) and artificial graphite (including flake graphite). Can be

【００１０】黒鉛の使用量は、塩化ナトリウム水溶液１
００重量部に対して０．１〜１０重量部、好ましくは１
〜４重量部である。上記使用量が０．１重量部未満の場
合、期待する過冷却防止効果が得られず、一方１０重量
部を超えると、潜熱量が低下し、かつ溶液の残渣が認め
られ、均一性が損なわれる場合がある。[0010] The amount of graphite used is 1
0.1 to 10 parts by weight, preferably 1 to 100 parts by weight
４4 parts by weight. When the amount is less than 0.1 part by weight, the expected effect of preventing supercooling cannot be obtained. On the other hand, when the amount exceeds 10 parts by weight, the amount of latent heat is reduced, and a residue of the solution is observed. May be

【００１１】必須成分の他に本発明の潜熱蓄冷材に加え
てもよい成分として、吸水性樹脂、アタパルジャイ粘
土、ゼラチン、寒天、シリカゲルなどの増粘剤などが挙
げられる。In addition to the essential components, the components that may be added to the latent heat storage material of the present invention include water-absorbing resins, thickening agents such as attapulghai clay, gelatin, agar, and silica gel.

【００１２】また本発明の潜熱蓄冷材は、好ましくは−
４０℃〜−２℃、さらに好ましくは−３０℃〜−１５℃
の温度範囲で相転移現象の生じるものがよい。The latent heat storage material of the present invention is preferably-
40 ° C to -2 ° C, more preferably -30 ° C to -15 ° C
It is preferable that a phase transition phenomenon occurs in the above temperature range.

【００１３】蓄冷材の製造法は特に限定されないが、例
えば、容器に入れた純水またはイオン交換水に、塩化ナ
トリウムを徐々に攪拌しながら所定量まで投入し、十分
混合した後、過冷却防止剤である黒鉛を徐々に攪拌しな
がら所定量まで投入し、十分混合し、他の添加剤もこれ
と同時またはこの後で添加し、攪拌・混合する方法、樹
脂の上に塩化ナトリウム、黒鉛などを予め混合した水溶
液を注ぎ込む方法などがある。なお、塩化ナトリウム、
黒鉛および他の添加剤の投入順序は任意であり、かつ溶
解を促進するために５０℃程度まで加熱することも可能
である。また、塩化ナトリウムと黒鉛などを混合した
後、該混合物を純水またはイオン交換水に投入してもよ
い。The method for producing the regenerator material is not particularly limited. For example, sodium chloride is gradually added to pure water or ion-exchanged water contained in a container to a predetermined amount while gradually stirring the mixture, and the mixture is sufficiently mixed. Charge the graphite as a premixing agent up to a predetermined amount while stirring, mix well and add other additives at the same time or after, stirring and mixing, sodium chloride, graphite, etc. on the resin And a method of pouring an aqueous solution obtained by premixing the components in advance. In addition, sodium chloride,
The order of charging graphite and other additives is arbitrary, and heating to about 50 ° C. is possible to promote dissolution. After mixing sodium chloride and graphite, the mixture may be added to pure water or ion-exchanged water.

【００１４】蓄冷材の形態も特に限定されないが、通常
は、上記した蓄冷材を耐蝕性のある金属や無機材料、お
よび／またはポリエチレンを初めとするプラスチックな
どの有機材料によって包装する形態となる。また形状と
しては、塊状、板状、シート状などがある。このような
蓄冷材が配置される場所としては、蓄冷室にそのまま、
あるいは熱交換部に置く、などが考えられる。Although the form of the cold storage material is not particularly limited, it is usually a form in which the above-mentioned cold storage material is packaged with a corrosion-resistant metal or inorganic material and / or an organic material such as polyethylene or other plastics. Examples of the shape include a lump, a plate, and a sheet. As a place where such a cold storage material is arranged, as it is in a cold storage room,
Alternatively, it is conceivable to place it in a heat exchange section.

【００１５】[0015]

【実施例】以下、本発明を実施例により具体的に説明す
る。ただし本発明は以下の実施例に限定されるものでは
ない。 実施例１ ２３．３重量％塩化ナトリウム水溶液に、該水溶液１０
０重量部に対して人造黒鉛（純度９９．９％、形状：
球、平均粒径：約５μｍ）を３重量部添加して蓄冷材を
得た。得られた蓄冷材の凝固開始温度を、ＤＳＣ（示差
走査熱量計）で降温速度：１℃／分→−４５℃で２０分
保持→昇温速度２℃／分→＋１０℃を１サイクルとし、
７回繰り返して測定した。また、得られた蓄冷材の温度
を１０℃に上げても失活現象は顕著には現れなかった。The present invention will be described below in more detail with reference to examples. However, the present invention is not limited to the following examples. Example 1 A 23.3% by weight aqueous sodium chloride solution was added to the aqueous solution 10
0 parts by weight of artificial graphite (purity 99.9%, shape:
(Sphere, average particle size: about 5 μm) was added to obtain a regenerator material. The solidification start temperature of the obtained regenerator material was determined by DSC (differential scanning calorimeter) at a temperature lowering rate of 1 ° C./min→held at −45 ° C. for 20 minutes → a temperature increasing rate of 2 ° C./min→+10° C. as one cycle
The measurement was repeated seven times. Further, even when the temperature of the obtained regenerator material was raised to 10 ° C., the deactivation phenomenon did not appear remarkably.

【００１６】実施例２ 人造黒鉛の代わりに天然黒鉛（純度９９．９％、形状：
粒状、平均粒径：１０μｍ）を使用した以外は実施例１
と同様にして蓄冷材を得、凝固開始温度を測定した。Example 2 Instead of artificial graphite, natural graphite (purity 99.9%, shape:
Example 1 except that granular, average particle size: 10 μm) was used.
A regenerator material was obtained in the same manner as described above, and the solidification start temperature was measured.

【００１７】比較例１ ２３．３重量％塩化ナトリウム水溶液（過冷却防止剤を
使用せず）の凝固開始温度を実施例１と同様にして測定
した。Comparative Example 1 The solidification starting temperature of a 23.3% by weight aqueous sodium chloride solution (without using a supercooling inhibitor) was measured in the same manner as in Example 1.

【００１８】比較例２ 人造黒鉛の代わりにケッチェンブラック（純度９９．３
％、形状：粒子凝集体、平均粒径：３０ｎｍ）を使用し
た以外は実施例１と同様にして蓄冷材を得、凝固開始温
度を測定した。Comparative Example 2 Ketjen Black (purity 99.3) was used instead of artificial graphite.
%, Shape: particle aggregate, average particle size: 30 nm), and a regenerator material was obtained in the same manner as in Example 1, and the solidification start temperature was measured.

【００１９】比較例３ 人造黒鉛の代わりにアセチレンブラック（純度９９．７
％、形状：粒子凝集体、平均粒径：５０ｎｍ）を使用し
た以外は実施例１と同様にして蓄冷材を得、凝固開始温
度を測定した。実施例１、２および比較例１〜３の結果
を表１および図１に示す。Comparative Example 3 In place of artificial graphite, acetylene black (purity 99.7)
%, Shape: particle aggregate, average particle size: 50 nm), and a regenerator material was obtained in the same manner as in Example 1, and the solidification start temperature was measured. Table 1 and FIG. 1 show the results of Examples 1 and 2 and Comparative Examples 1 to 3.

【００２０】[0020]

【表１】 [Table 1]

【００２１】以上の実施例および比較例の結果から、本
発明の潜熱蓄冷材は過冷却防止剤を使用しないものに比
べて１０℃以上の過冷却防止効果が得られ、またケッチ
ェンブラック、アセチレンブラックの結果と比較しても
かなり良い特性が得られているのがわかる。From the results of the above Examples and Comparative Examples, the latent heat storage material of the present invention has an effect of preventing supercooling of 10 ° C. or more as compared with the case where no supercooling inhibitor is used. It can be seen that considerably better characteristics are obtained as compared with the results of black.

【００２２】[0022]

【発明の効果】本発明の蓄冷材は、塩化ナトリウム水溶
液の過冷却が有効に抑制できかつ失活現象も示さず、経
済的に有効な蓄冷材であり、さらに安全性が高いためア
イスクリームなどの食品の保冷に問題なく利用できる。The regenerator material of the present invention is an economically effective regenerator material which can effectively suppress supercooling of an aqueous solution of sodium chloride and does not show a deactivation phenomenon. It can be used for keeping food cool.

【図面の簡単な説明】[Brief description of the drawings]

【図１】実施例１、２および比較例１〜３の蓄冷材の凝
固開始温度を示す。縦軸は凝固開始温度を、横軸はサイ
クル数（回）を示す。FIG. 1 shows the solidification start temperature of the cold storage materials of Examples 1 and 2 and Comparative Examples 1 to 3. The vertical axis indicates the solidification start temperature, and the horizontal axis indicates the number of cycles (times).

【符号の説明】[Explanation of symbols]

ａ 実施例１のサンプルの凝固開始温度を示す。 ｂ 実施例２のサンプルの凝固開始温度を示す。 ｃ 比較例１のサンプルの凝固開始温度を示す。 ｄ 比較例２のサンプルの凝固開始温度を示す。 ｅ 比較例３のサンプルの凝固開始温度を示す。 ｆ ２３．３重量％塩化ナトリウム水溶液の融解温度
（−２１．１℃、過冷却のない状態）を示す。a shows the solidification onset temperature of the sample of Example 1. b Shows the solidification onset temperature of the sample of Example 2. c Shows the solidification start temperature of the sample of Comparative Example 1. d shows the solidification start temperature of the sample of Comparative Example 2. e shows the solidification start temperature of the sample of Comparative Example 3. f shows the melting temperature of an aqueous 23.3% by weight sodium chloride solution (-21.1 ° C, without supercooling).

Claims (5)

【特許請求の範囲】[Claims] 【請求項１】 塩化ナトリウム水溶液および黒鉛を含む
潜熱蓄冷材。1. A latent heat storage material containing an aqueous sodium chloride solution and graphite. 【請求項２】 黒鉛が純度９９％以上である請求項１記
載の潜熱蓄冷材。2. The latent heat storage material according to claim 1, wherein the graphite has a purity of 99% or more. 【請求項３】 黒鉛の量が、塩化ナトリウム水溶液１０
０重量部に対して０．１〜１０重量部である請求項１ま
たは２記載の潜熱蓄冷材。3. The amount of graphite is 10% aqueous sodium chloride solution.
3. The latent heat storage material according to claim 1, wherein the amount is 0.1 to 10 parts by weight relative to 0 parts by weight. 【請求項４】 −４０℃〜−２℃の温度範囲で相転移現
象の生じる請求項１〜３のいずれかに記載の潜熱蓄冷
材。4. The latent heat storage material according to claim 1, wherein a phase transition phenomenon occurs in a temperature range of −40 ° C. to −2 ° C. 【請求項５】 塩化ナトリウムの濃度が５〜３０重量％
である請求項１〜４のいずれかに記載の潜熱蓄冷材。5. The concentration of sodium chloride is 5 to 30% by weight.
The latent heat storage material according to any one of claims 1 to 4, wherein