JP3641362B2 - Cold storage method using cold clathrate, cold storage system, and cold storage agent - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、冷房などの空調設備や、食品等の冷却装置などに用いられる冷熱体の蓄冷方法、蓄冷システム、蓄冷剤に関する。
【０００２】
【従来の技術】
この種の用途に使用される従来公知の蓄冷方法として以下のものがある。
（１）冷水の温度差による蓄冷
空調では、冷房用の冷水温度は５〜７℃であり、負荷の小さい時間に冷凍機により冷水を貯蔵タンク（蓄熱槽）に貯蔵する。冷水の比熱は１ｋｃａｌ／ｋｇＫであるため、利用温度差を７℃とすると、１ｋｇ冷水あたり７ｋｃａｌ／ｋｇと単位重量当りの蓄冷量が少ないという欠点がある。
【０００３】
（２）氷などの凝固・融解潜熱を用いた蓄冷
氷の融解潜熱は、約８０ｋｃａｌ／ｋｇであるため、氷水の一部を氷にして蓄冷することで、蓄熱密度は冷水より高くできる。例えば、冷水中の氷の体積割合を２０％とすると、氷の潜熱及び冷水の顕熱（温度差１２℃の場合）を含めた蓄熱密度は、約２８ｋｃａｌ／ｋｇとなる。
【０００４】
しかし、氷を生成させるためには、冷水を０℃以下に冷却しなければならず、冷水を５℃に冷却するよりも冷凍機の動力は大きくなるのが欠点である。
（３）氷以外の固液相変化物質を用いた蓄冷
水や氷以外の冷熱蓄熱材として利用可能な物質として、ＬｉＣｌＯ2 ・３Ｈ2 ＯやＮａ2 ＳＯ4 ・１０Ｈ2 Ｏ＋ＮＨ4 Ｃｌなどの無機水和塩類や気体水和物が知られている（文献１．川崎、秋谷「基体水和物の冷熱蓄熱材への応用」：ケミカルエンジニアリングvol.27,No.8,603-608,1982、文献２．日本伝熱学会編「環境と省エネルギーのためのエネルギー新技術体系」ｐ．８０２、参照）
しかし、ＬｉＣｌＯ2 ・３Ｈ2 ＯやＮａ2 ＳＯ4 ・１０Ｈ2 Ｏ＋ＮＨ4 Ｃｌなどの無機水和塩類は、比較的潜熱量は大きいものの、調和融点（後述）を持たず、無水塩の濃度によって水和物が変化する。このため、冷却・加熱過程で相分離をおこし、所定の蓄熱量が得られなくなる問題が生ずる。
【０００５】
また、文献１に記載されている気体水和物は、Ｒ１１やＲ１２などのオゾン破壊係数の大きい物質であったり、また、大気圧下では気体であるため、加圧された密閉容器や配管を用いる必要があり、蓄冷装置が高価なものとなる。
【０００６】
【発明が解決しようとする課題】
以上のように、今までに実用化あるいは提案されてきた蓄冷方法には、それぞれ問題点があった。
本発明は、これらの課題を解決すべくなされたもので、蓄冷材に求められる蓄熱密度（潜熱量）が大きく、安定した熱特性を有し、経済性、安全性があり取り扱いが容易である包接水和物を用いた蓄冷方法、蓄冷システムおよび蓄熱剤を提供することを目的とする。
【０００７】
【課題を解決するための手段】
すなわち本発明は、
（１）包接水和物の調和融点を与える濃度未満の包接水和物生成物質を含む水溶液であって、冷却すると包接水和物を生成しスラリ状となるものからなる蓄冷剤。
（２）包接水和物生成物質は、テトラ−ｎ−ブチルアンモニウム塩、テトラｉｓｏ−アミルアンモニウム塩、テトラ−ｎ−ブチルフォスフォニウム塩、及びトリｉｓｏ−アミルサルフォニウム塩の群から選択される１種又は２種以上であることを特徴とする（１）に記載の蓄冷剤。
（３）水溶液は、水よりも凝固点の低い物質を含むことを特徴とする（１）又は（２）に記載の蓄冷剤。
【０００８】
（４）水分子で構成された籠状の包接格子内にゲスト分子が包み込まれて結晶化する包接水和物を生成する物質を含む水溶液であって、冷却すると包接水和物を生成しスラリ状となるものからなり、更に水よりも凝固点の低い物質とを含む水溶液からなる蓄冷剤。
（５）ゲスト分子は、テトラ−ｎ−ブチルアンモニウム塩、テトラｉｓｏ−アミルアンモニウム塩、テトラ−ｎ−ブチルフォスフォニウム塩、及びトリｉｓｏ−アミルサルフォニウム塩の群から選択される１種又は２種以上であることを特徴とする（４）に記載の蓄冷剤。
【０００９】
（６）外部から輸送される蓄冷剤と水又は空気との間で熱交換を行う熱交換器であって、蓄冷剤は、包接水和物の調和融点を与える濃度未満の包接水和物生成物質を含む水溶液を冷却して生成する包接水和物のスラリであることを特徴とする熱交換器。
（７）包接水和物の調和融点を与える濃度未満の包接水和物生成物質を含む水溶液を冷却して生成する包接水和物のスラリと、水又は空気との間で熱交換を行う熱交換器。
【００１０】
（８）（６）又は（７）に記載の熱交換器を備える蓄冷システム。
【００１１】
（９）包接水和物の調和融点を与える濃度未満の包接水和物生成物質を含む水溶液を冷却して包接水和物を生成させ、スラリ状にすることを特徴とする蓄冷方法。
【００１２】
（１０）包接水和物の調和融点を与える濃度未満の包接水和物生成物質と融点降下剤とを含む水溶液を冷却して包接水和物を生成させ、スラリ状にすることを特徴とする蓄冷方法。
【００１３】
（１１）包接水和物は、水分子で構成された籠状の包接格子内にゲスト分子が包み込まれて結晶化する化合物であることを特徴とする（９）又は（１０）に記載の蓄熱方法。
（１２）ゲスト分子は、テトラ−ｎ−ブチルアンモニウム塩、テトラｉｓｏ−アミルアンモニウム塩、テトラ−ｎ−ブチルフォスフォニウム塩、及びトリｉｓｏ−アミルサルフォニウム塩の群から選択される一種又は２種以上であることを特徴とする（１１）に記載の蓄熱方法。
【００１４】
（１３）水分子で構成された籠状の包接格子内にゲスト分子が包み込まれて結晶化する包接水和物を生成する物質と水よりも凝固点の低い物質とを含む水溶液を冷却して包接水和物のスラリを生成させ、そのスラリを輸送又は貯蔵することを特徴とする蓄冷方法。
（１４）包接水和物の調和融点を与える濃度未満の包接水和物生成物質を含む水溶液を冷却して包接水和物のスラリを生成させ、そのスラリを輸送又は貯蔵することを特徴とする蓄冷方法。
【００１５】
（１５）水よりも凝固点の低い物質を（１）又は（２）の蓄冷剤に混入させることにより蓄冷剤の融点を変更することを特徴とする蓄冷剤の製造方法。
【００１６】
【発明の実施の形態】
本発明に係る包接水和物とは、水分子（ホスト分子）で構成された籠状の包接格子内に以下の様なゲスト分子が包み込まれて結晶化する化合物をいう。ゲスト分子として、テトラｎ−ブチルアンモニウム塩、テトラｉｓｏ−アミルアンモニウム塩、テトラｎ−フォスフォニウム塩、トリｉｓｏ−アミルサルフォニウム塩の例として、テトラｎ−ブチルアンモニウム塩としてフッ化テトラｎ−ブチルアンモニウム（ｎ−Ｃ4 Ｈ9 ）4 ＮＦ），塩化テトラｎ−ブチルアンモニウム（（ｎ−Ｃ4 Ｈ9 ）4 ＮＣｌ），臭化テトラｎ−ブチルアンモニウム（（ｎ−Ｃ4 Ｈ9 ）4 ＮＢｒ）などがある。
【００１７】
これらＦ，Ｃｌ，Ｂｒの代わりに酢酸（ＣＨ3 ＣＯ2 ），重炭酸（ＨＣＯ2 ），クロム酸（ＣｒＯ4 ），タングステン酸（ＷＯ4 ），シュウ酸（Ｃ2 Ｏ4 ），リン酸（ＨＰＯ4 ）でもよい。その他の上記塩も同様である。
【００１８】
以下、臭化テトラｎ−ブチルアンモニウム（（ｎ−Ｃ4 Ｈ9 ）4 ＮＢｒ）を例にとり、本発明の蓄冷システムを説明する。
水溶液濃度と融点の関係を図１に示す。また、包接水和物が生成、分解するときの反応式を式（１）に示す。
【００１９】
(n-C4 H 9 ) 4 NBr ＋n ・H 2 O ←→ (n-C4 H 9 ) 4 NBr ・n ・H 2 O
…式（１）
ここで、ｎは水和数で、その値はおよそ２６で常に一定である。
【００２０】
図１に示されるように、この包接水和物生成物質を含む水溶液は、水溶液濃度約４０ｗｔ％で融点が極大値、１１．８℃である。この水溶液濃度の融点は調和融点と呼ばれ、ここでは水溶液中の濃度と包接水和物中の塩分濃度が等しい。
【００２１】
従って、調和融点を与える水溶液濃度（この例では常温における塩濃度が４０ｗｔ％）に設定した水溶液を用いてこれを冷却すると、調和融点（１１．８℃）で包接水和物が生成しはじめ、水溶液が全て包接水和物になるまでこの融点で一定になる。分解（融解）時も同様にこの融点一定で冷熱を放出する。なお、潜熱量は約４６ｋｃａｌ／ｋｇであり、利用上限温度を１２℃とすると、水和物の体積割合が５６％で蓄熱密度は２６ｋｃａｌ／ｋｇとなる。
【００２２】
このようにこの蓄冷剤は、蓄熱密度が大きく、安定した熱特性を有する。また、従来は触媒として用いられているので容易に入手可能であり、経済的かつ安全である。
【００２３】
また、調和融点を与える上記水溶液濃度より低い濃度に設定した水溶液（例えば常温で２７．２ｗｔ％の水溶液）を用いて冷却すると、約９．４℃で水和物が生成しはじめ、次第に水溶液中の塩分濃度が低下していき、それにつれて水和物の生成温度も低下していく。すなわち、図１の曲線に沿って包接水和物の生成温度も下がる。空調に適する１５℃程度の水・空気を作るために水溶液を５℃まで冷却すると、水溶液中の塩分濃度は約１７ｗｔ％になる。このとき、水溶液の４３％が水和物になる。また蓄熱量は、およそ２６ｋｃａｌ／ｋｇとなる（水和物の比熱を０．５３ｋｃａｌ／ｋｇＫ，水溶液の比熱を０．９６ｋｃａｌ／ｋｇＫとした）。また、包接水和物の潜熱を利用する場合には常温で濃度４％以上の濃度にする必要がある。
【００２４】
このように、調和融点を与える上記水溶液濃度より低い濃度に設定した水溶液を用いると、更に以下の利点を備える。
（１）融点（生成温度）が低温側に変化するため、低い温度の冷熱を蓄冷でき、その結果、所望の低い温度で取出することができる。
【００２５】
（２）融点（生成温度）が低温側に変化していくため、水和物と水又は空気と熱交換させる場合、その温度差がほぼ一定でしかも大きい。このため熱交換効率が高く、熱交換器をコンパクトとすることができる。即ち、熱交換器で２０℃の水または空気を冷却して１５℃とするに際し、図２のａに示す調和融点濃度の場合、水又は空気の出側（蓄冷剤の入り側）の蓄冷剤の温度が１１．８℃であり、その温度差が３．８℃しかないが、図２のｂに示す調和融点濃度より低い場合、例えば水又は空気の出側（蓄冷剤の入り側）の蓄冷剤の温度が５℃であり、その温度差を１０℃とすることができる。
【００２６】
（３）ほぼ同じ利用上限温度で蓄熱密度が同じ場合、水溶液中の塩分濃度を低くできるため、その分低コストになる。
（４）ほぼ同じ利用上限温度で蓄熱密度が同じ場合、水和物の体積割合は小さくてすむため、水和物スラリの輸送や貯蔵のハンドリングが容易となる。顕熱分が大きくなる。即ち、蓄熱量は「潜熱」＋「顕熱」で示されるが、蓄熱量を同じとした場合、調和融点より低い濃度の方が顕熱分が大きいため、水和物の体積割合が小さくてすむ。この試算を表１に示す。
【００２７】
【表１】
次に本発明では、水溶液に水よりも凝固点の小さい物質を混入させて、包接水和物の生成温度（融点）を低下させることができる。
臭化テトラｎ−ブチルアンモニウム（（ｎ−Ｃ4 Ｈ9 ）4 ＮＢｒ）を例に取ると、その調和融点は、１１．８℃であり、水溶液濃度と融点の関係は上述したように図１のようになる。
【００２９】
この水溶液に、エチレングリコール、プロピレングリコールなど融点降下剤（水よりも融点の低い物質）を混入させると、水溶液の融点は、この物質の混入量によって低下する。そこで、用途により利用温度幅を下げる必要がある場合、これら物質を適量混入させることにより、任意の融点を持つ蓄冷剤を作ることができる。
【００３０】
【発明の効果】
このように、本発明に係る蓄冷剤を用いれば、蓄熱密度が大きく、安定した熱特性を有する。また、従来は触媒として用いられており、容易に入手可能であり、経済的かつ安全である。特に、調和融点を与える上記水溶液濃度より低い濃度に設定した水溶液を用いると、所望の低い温度範囲で冷熱を蓄冷でき、その結果、低い温度で取出せる。そして、熱交換効率が高いので、熱交換器をコンパクトにでき、さらに、コストも安く、水和物スラリの輸送や貯蔵のハンドリングが容易となる。
【００３１】
さらに、水より融点の低い物質を混入させることによって、同じ塩を用いた水溶液で任意の融点を持つ蓄冷剤を作ることができるため、汎用性が高く、コスト安にもなる。
【図面の簡単な説明】
【図１】包接水和物生成物質を含む水溶液濃度と融点との関係を示す図。
【図２】包接水和物生成物質を含む水溶液を蓄冷剤として用いた場合の熱交換器内の温度変化を示す説明図で、ａは調和融点濃度の包接水和物生成物質を含む水溶液を蓄冷剤として用いた場合、ｂは調和融点濃度より低い包接水和物を含む水溶液を蓄冷剤として用いた場合をそれぞれ示す。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cold storage method, a cold storage system, and a cold storage agent for a cold body used in air conditioning equipment such as cooling, a cooling device for foods, and the like.
[0002]
[Prior art]
Conventionally known cold storage methods used for this type of application include the following.
(1) In the cold storage air conditioning by the temperature difference of cold water, the cold water temperature for cooling is 5-7 degreeC, and cold water is stored in a storage tank (heat storage tank) with a refrigerator at the time of a small load. Since the specific heat of cold water is 1 kcal / kgK, there is a drawback that if the utilization temperature difference is 7 ° C., the amount of cold storage per unit weight is 7 kcal / kg per kg cold water.
[0003]
(2) Since the latent heat of fusion of the cold storage ice using solidification / melting latent heat of ice or the like is about 80 kcal / kg, the heat storage density can be made higher than that of the cold water by storing a part of the ice water as ice. For example, if the volume ratio of ice in cold water is 20%, the heat storage density including the latent heat of ice and the sensible heat of cold water (temperature difference of 12 ° C.) is about 28 kcal / kg.
[0004]
However, in order to generate ice, cold water must be cooled to 0 ° C. or lower, and the disadvantage is that the power of the refrigerator becomes larger than that of cooling cold water to 5 ° C.
(3) Inorganic materials such as LiClO 2 .3H 2 O and Na 2 SO 4 .10H 2 O + NH 4 Cl that can be used as cold storage water using solid-liquid phase change materials other than ice and cold heat storage materials other than ice Hydrated salts and gaseous hydrates are known (Reference 1. Kawasaki, Akiya “Application of Base Hydrate to Cold Heat Storage Material”: Chemical Engineering vol. 27, No. 8, 603-608, 1982, Reference 2 (Refer to “The New Energy Technology System for Environment and Energy Conservation” p. 802)
However, inorganic hydrated salts such as LiClO 2 .3H 2 O and Na 2 SO 4 .10H 2 O + NH 4 Cl have a relatively large amount of latent heat but do not have a harmonic melting point (described later). Japanese products change. For this reason, there arises a problem that phase separation is performed in the cooling / heating process, and a predetermined heat storage amount cannot be obtained.
[0005]
The gas hydrate described in Document 1 is a substance having a large ozone depletion coefficient such as R11 or R12, or is a gas under atmospheric pressure. It is necessary to use it, and a cool storage device becomes expensive.
[0006]
[Problems to be solved by the invention]
As described above, the cold storage methods that have been put to practical use or proposed so far have problems.
The present invention has been made to solve these problems, has a large heat storage density (latent heat amount) required for a cold storage material, has stable thermal characteristics, is economical, safe and easy to handle. An object is to provide a cold storage method, a cold storage system, and a heat storage agent using clathrate hydrate.
[0007]
[Means for Solving the Problems]
That is, the present invention
(1) A cold storage agent comprising an clathrate hydrate-forming substance having a concentration lower than the concentration that gives the harmonic melting point of clathrate hydrate, and which forms clathrate hydrate and becomes a slurry when cooled.
(2) The clathrate hydrate-forming substance is selected from the group of tetra-n-butylammonium salt, tetraiso-amylammonium salt, tetra-n-butylphosphonium salt, and triiso-amylsulfonium salt The regenerator according to (1), which is one or more types.
(3) The cold storage agent according to (1) or (2), wherein the aqueous solution contains a substance having a freezing point lower than that of water.
[0008]
(4) An aqueous solution containing a substance that forms a clathrate hydrate in which a guest molecule is wrapped in a cage clathrate lattice composed of water molecules and crystallizes. A cold storage agent comprising an aqueous solution that is formed into a slurry and further contains a substance having a freezing point lower than that of water.
(5) The guest molecule is selected from the group consisting of tetra- n -butylammonium salt, tetraiso-amylammonium salt, tetra- n - butylphosphonium salt, and triiso-amylsulfonium salt, or The regenerator according to (4), wherein there are two or more kinds.
[0009]
(6) A heat exchanger for exchanging heat between a cold storage agent transported from the outside and water or air, and the cold storage agent is clathrate hydrate less than the concentration that gives the harmonic melting point of clathrate hydrate A heat exchanger characterized by being a clathrate hydrate slurry produced by cooling an aqueous solution containing a product-generating substance.
(7) Heat exchange between a clathrate hydrate slurry produced by cooling an aqueous solution containing a clathrate hydrate-forming substance having a concentration lower than the concentration giving the harmonic melting point of the clathrate hydrate, and water or air Do heat exchanger.
[0010]
(8) A cold storage system comprising the heat exchanger according to (6) or (7).
[0011]
(9) A cold storage method characterized by cooling an aqueous solution containing a clathrate hydrate-producing substance having a concentration lower than the concentration that gives the harmonic melting point of clathrate hydrate to produce clathrate hydrate to form a slurry. .
[0012]
(10) Cooling an aqueous solution containing a clathrate hydrate-producing substance and a melting point depressant having a concentration lower than the concentration that gives the harmonic melting point of the clathrate hydrate to produce a clathrate hydrate to form a slurry. Characterized cold storage method.
[0013]
(11) The clathrate hydrate is a compound in which a guest molecule is encapsulated in a cage-like clathrate lattice composed of water molecules and crystallizes. (9) or (10) Heat storage method.
(12) The guest molecule is one or two selected from the group consisting of tetra- n -butylammonium salt, tetraiso-amylammonium salt, tetra- n - butylphosphonium salt, and triiso-amylsulfonium salt. It is a seed | species or more, The heat storage method as described in (11) characterized by the above-mentioned.
[0014]
(13) Cooling an aqueous solution containing a substance that forms an clathrate hydrate in which a guest molecule is wrapped in a cage-like clathrate lattice composed of water molecules and crystallizes, and a substance that has a lower freezing point than water. A cold storage method characterized in that a clathrate hydrate slurry is produced and the slurry is transported or stored.
(14) Cooling an aqueous solution containing a clathrate hydrate-forming substance at a concentration that gives a harmonic melting point of the clathrate hydrate to produce a clathrate hydrate slurry, and transporting or storing the slurry. Characterized cold storage method.
[0015]
(15) A method for producing a regenerator, wherein a melting point of the regenerator is changed by mixing a substance having a freezing point lower than water in the regenerator (1) or (2).
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The clathrate hydrate according to the present invention refers to a compound that crystallizes by encapsulating the following guest molecules in a cage-like clathrate composed of water molecules (host molecules). Examples of guest molecules include tetra-n-butylammonium salt, tetraiso-amylammonium salt, tetran-phosphonium salt, triiso-amylsulfonium salt, tetra-n-butylammonium salt as tetra-n-butylammonium salt Butylammonium (n-C 4 H 9 ) 4 NF), tetra-n-butylammonium chloride ((n-C 4 H 9 ) 4 NCl), tetra-n-butylammonium bromide ((n-C 4 H 9 ) 4 NBr).
[0017]
Instead of these F, Cl and Br, acetic acid (CH 3 CO 2 ), bicarbonate (HCO 2 ), chromic acid (CrO 4 ), tungstic acid (WO 4 ), oxalic acid (C 2 O 4 ), phosphoric acid ( HPO 4 ) may also be used. The same applies to the other salts.
[0018]
Hereinafter, the cold storage system of the present invention will be described by taking tetra n-butylammonium bromide ((n-C 4 H 9 ) 4 NBr) as an example.
The relationship between the aqueous solution concentration and the melting point is shown in FIG. The reaction formula when the clathrate hydrate is generated and decomposed is shown in Formula (1).
[0019]
(nC 4 H 9 ) 4 NBr + n • H 2 O ← → (nC 4 H 9 ) 4 NBr • n • H 2 O
... Formula (1)
Here, n is a hydration number, and its value is approximately 26 and is always constant.
[0020]
As shown in FIG. 1, the aqueous solution containing the clathrate hydrate-forming substance has an aqueous solution concentration of about 40 wt% and a melting point at a maximum value of 11.8 ° C. The melting point of this aqueous solution concentration is called the harmonic melting point, and here, the concentration in the aqueous solution is equal to the salinity concentration in the clathrate hydrate.
[0021]
Therefore, when an aqueous solution set to a concentration of an aqueous solution giving a harmonic melting point (in this example, the salt concentration at room temperature is 40 wt%) is cooled, clathrate hydrate begins to form at the harmonic melting point (11.8 ° C.). The melting point remains constant until the aqueous solution is all clathrate hydrate. Similarly, at the time of decomposition (melting), cold heat is released with this constant melting point. The latent heat amount is about 46 kcal / kg. If the upper limit temperature of use is 12 ° C., the volume ratio of hydrate is 56% and the heat storage density is 26 kcal / kg.
[0022]
Thus, this cool storage agent has a large heat storage density and stable thermal characteristics. Further, since it is conventionally used as a catalyst, it can be easily obtained, and is economical and safe.
[0023]
Further, when cooling with an aqueous solution set to a concentration lower than the above aqueous solution concentration giving a harmonic melting point (for example, an aqueous solution of 27.2 wt% at room temperature), a hydrate begins to be formed at about 9.4 ° C., and gradually in the aqueous solution. As the salt concentration of the hydrate decreases, the hydrate formation temperature also decreases. That is, the production temperature of clathrate hydrate also decreases along the curve of FIG. When the aqueous solution is cooled to 5 ° C. in order to produce water / air at about 15 ° C. suitable for air conditioning, the salt concentration in the aqueous solution becomes about 17 wt%. At this time, 43% of the aqueous solution becomes a hydrate. The heat storage amount is approximately 26 kcal / kg (the specific heat of the hydrate is 0.53 kcal / kgK and the specific heat of the aqueous solution is 0.96 kcal / kgK). Further, when utilizing the latent heat of clathrate hydrate, it is necessary to make the
[0024]
Thus, when the aqueous solution set to a concentration lower than the concentration of the aqueous solution giving a harmonic melting point is used, the following advantages are further provided.
(1) Since the melting point (generation temperature) changes to the low temperature side, cold heat at a low temperature can be stored, and as a result, it can be taken out at a desired low temperature.
[0025]
(2) Since the melting point (generation temperature) changes to the low temperature side, when heat exchange is performed with hydrate and water or air, the temperature difference is substantially constant and large. For this reason, heat exchange efficiency is high and a heat exchanger can be made compact. That is, when the water or air at 20 ° C. is cooled to 15 ° C. with a heat exchanger, the regenerator on the outlet side of water or air (on the side of the regenerator) in the case of the harmonic melting point concentration shown in FIG. The temperature is 11.8 ° C. and the temperature difference is only 3.8 ° C., but if it is lower than the harmonic melting point concentration shown in FIG. 2b, for example, water or air exit side (cold storage agent entrance side) The temperature of the cold storage agent is 5 ° C., and the temperature difference can be 10 ° C.
[0026]
(3) When the heat storage density is the same at almost the same use upper limit temperature, the salinity concentration in the aqueous solution can be lowered, and the cost is reduced accordingly.
(4) When the heat storage density is the same at almost the same upper limit temperature of use, the volume ratio of the hydrate can be small, so that the hydrate slurry can be easily transported and handled. Sensible heat increases. That is, the amount of heat stored is expressed as “latent heat” + “sensible heat”, but when the amount of stored heat is the same, the sensible heat content is larger at a concentration lower than the harmonic melting point, so the volume ratio of the hydrate is small. I'm sorry. This trial calculation is shown in Table 1.
[0027]
[Table 1]
Next, in the present invention, a production temperature (melting point) of clathrate hydrate can be lowered by mixing a substance having a freezing point smaller than water in the aqueous solution.
Taking tetra n-butylammonium bromide ((n-C 4 H 9 ) 4 NBr) as an example, its harmonic melting point is 11.8 ° C. The relationship between the aqueous solution concentration and the melting point is as shown in FIG. become that way.
[0029]
When a melting point depressant (a substance having a melting point lower than that of water) such as ethylene glycol or propylene glycol is mixed in this aqueous solution, the melting point of the aqueous solution is lowered depending on the amount of this substance. Therefore, when it is necessary to lower the use temperature range depending on the application, a regenerator having an arbitrary melting point can be made by mixing an appropriate amount of these substances.
[0030]
【The invention's effect】
Thus, if the cool storage agent which concerns on this invention is used, a thermal storage density is large and it has the stable thermal characteristic. Moreover, it is conventionally used as a catalyst, is easily available, and is economical and safe. In particular, when an aqueous solution set to a concentration lower than the above aqueous solution concentration giving a harmonic melting point is used, cold energy can be stored in a desired low temperature range, and as a result, it can be taken out at a low temperature. Further, since the heat exchange efficiency is high, the heat exchanger can be made compact, the cost is low, and the transportation and storage handling of the hydrate slurry is facilitated.
[0031]
Further, by incorporating a substance having a melting point lower than that of water, a regenerator having an arbitrary melting point can be made with an aqueous solution using the same salt, so that the versatility is high and the cost is low.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the concentration of an aqueous solution containing a clathrate hydrate-forming substance and the melting point.
FIG. 2 is an explanatory view showing a temperature change in a heat exchanger when an aqueous solution containing a clathrate hydrate-generating substance is used as a cold storage agent, wherein a includes a clathrate hydrate-forming substance having a harmonic melting point concentration. When an aqueous solution is used as a cold storage agent, b shows the case where the aqueous solution containing the clathrate hydrate lower than a harmonic melting point density | concentration is used as a cold storage agent, respectively.
Claims (15)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| JP06890198A JP3641362B2 (en) | 1998-03-18 | 1998-03-18 | Cold storage method using cold clathrate, cold storage system, and cold storage agent |
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| Application Number | Priority Date | Filing Date | Title |
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| JP06890198A JP3641362B2 (en) | 1998-03-18 | 1998-03-18 | Cold storage method using cold clathrate, cold storage system, and cold storage agent |
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| JP2004367878A Division JP4134982B2 (en) | 2004-12-20 | 2004-12-20 | Cold storage method, cold storage system, cold storage agent, and method of extracting cold |
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| JP3641362B2 true JP3641362B2 (en) | 2005-04-20 |
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