JP2008045809A - Refrigerating cycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the amount of desiccant used and to contribute to compactness and on-vehicle mountability of a refrigerating cycle taking carbon dioxide as a refrigerant by solving the problem of an increase in infiltration amount of water in the refrigerating cycle with carbon dioxide as the refrigerant. <P>SOLUTION: In this refrigerating cycle taking carbon dioxide as a refrigerant, aluminosilicate-base zeolite is used as a desiccant of carbon dioxide refrigerant. The aluminosilicate-base zeolite has a pore diameter of 0.3 nm or more, and some or the whole of cations in counter ions have a smaller ion radius than potassium ion and have oxidation number equal to or more than bivalence. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle, and more particularly to a refrigeration cycle using carbon dioxide as a refrigerant.

  Conventionally, silica gel, alumina gel, zeolite, and the like are used as the refrigerant desiccant in the refrigeration cycle. Zeolite exerts its drying ability by packing water molecules into the pores of the zeolite and adsorbing them. Therefore, the larger the pore volume per unit amount of zeolite, the more water can be adsorbed, It can be said that ability is high. However, in the fluorine-containing refrigerants currently used in general, when the pore diameter of the zeolite is larger than the refrigerant molecules, not only water molecules but also refrigerant molecules are taken into the zeolite and the decomposition reaction occurs. The possibility has been pointed out.

  Aluminosilicate-based zeolites usually contain alkali metal ions such as sodium ions, potassium ions, or both as cations in the counter ion, and the pore size varies depending on the content ratio of these cations. To do. That is, when a large amount of potassium cations having a larger ionic radius is contained, the occupied volume of the cations in the pores is increased, and both the pore diameter and the pore volume are reduced. For this reason, zeolite having a pore size that adjusts the sodium / potassium content ratio of these alkali metal ions and incorporates only water molecules into the pores has been used in refrigeration cycles using fluorine-containing refrigerants. It was.

  On the other hand, recently, a refrigeration cycle using carbon dioxide as a refrigerant has attracted attention as a method for de-fluorinating a refrigerant. In this refrigeration cycle, zeolite is used as a desiccant, and the refrigerant is incorporated into the zeolite. The refrigerant molecules themselves do not change into compounds that affect the surrounding materials used during the cycle. Also, in the refrigeration cycle using carbon dioxide as the refrigerant, water that can be dissolved per unit amount of refrigerant is smaller than that of chlorofluorocarbon refrigerant, so water that enters the cycle and does not dissolve in the refrigerant is released. In the case of using a conventional desiccant, it is unavoidable to increase the size of the cycle, and it is particularly difficult to use it for an in-vehicle air conditioner. Therefore, further improvement of the water adsorption capacity of the desiccant aimed at downsizing the refrigeration cycle is required.

  It is also known to use an aluminosilicate zeolite as a desiccant in a refrigeration cycle using carbon dioxide as a refrigerant (Patent Documents 1 and 2). However, these only disclose a synthetic zeolite having a pore diameter of 0.33 nm or less and a sodium A-type zeolite having a pore diameter of 0.3 nm as desiccants, respectively. It cannot be solved.

JP 2005-315133 A JP 2001-255043 A

  An object of this invention is to solve said subject in the increase in the infiltration amount of the water in the refrigerating cycle using a carbon dioxide as a refrigerant | coolant.

In order to solve the above problems, the present invention provides the following inventions.
(1) An aluminosilicate having a pore diameter of 0.3 nm or more; and a part or all of cations in the counter ion are metal ions having an ionic radius smaller than that of potassium ions and having an oxidation number of 2 or more. A refrigeration cycle using carbon dioxide as a refrigerant, characterized by using an acid-based zeolite as a desiccant for the carbon dioxide refrigerant;
(2) A refrigeration cycle using carbon dioxide as a refrigerant according to (1), wherein the metal ion having an ionic radius smaller than potassium ion is an alkaline earth metal ion;
(3) A refrigeration cycle using carbon dioxide as a refrigerant according to (2), wherein the alkaline earth metal ion is magnesium ion or calcium ion;
(4) A refrigeration cycle using carbon dioxide as a refrigerant according to any one of (1) to (3), wherein the aluminosilicate zeolite has an LTA type or faujasite type structure;
(5) An air conditioner using the refrigeration cycle according to any one of (1) to (4);
(6) A vehicle-mounted air conditioner using the refrigeration cycle according to any one of (1) to (4); and (7) a water heater using the refrigeration cycle according to any one of (1) to (4) ,
It is.

  ADVANTAGE OF THE INVENTION According to this invention, the subject in the increase in the amount of water permeation in the refrigerating cycle using the zeolite which the adsorption amount of the water per unit quantity improved as a desiccant and using a carbon dioxide as a refrigerant | coolant can be solved. Therefore, the amount of desiccant used can be reduced, and the refrigeration cycle using carbon dioxide as a refrigerant can be made compact, and further contributed to in-vehicle use.

  In the refrigeration cycle of the present invention, the pore diameter is 0.3 nm (3 cm) or more; and some or all of the cations in the counter ion have an ionic radius smaller than that of potassium ion (0.133 nm), An aluminosilicate zeolite, which is a metal ion having an oxidation number equal to or higher than the valence, is used as a desiccant for the carbon dioxide refrigerant. The oxidation number of the metal ion having an ionic radius smaller than that of the potassium ion is preferably selected from divalent or trivalent. Examples of such metal ions having a bivalent or higher oxidation number include magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, cerium, neodymium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, One or more ions of each of tungsten, manganese, iron, cobalt, nickel, palladium, iridium, platinum, copper, zinc, boron, gallium, indium, and germanium can be used. Alkaline earth metal ions are preferable, and magnesium ions or calcium ions are particularly preferable.

  The aluminosilicate-based zeolite in the present invention is not particularly limited as long as it has the above-mentioned characteristics, but those having an LTA type or faujasite type structure can be suitably used.

  The aluminosilicate zeolite according to the present invention improves the amount of water adsorbed per unit amount, can prevent the release of moisture into the refrigeration cycle as a drying agent for carbon dioxide refrigerant, and improves the life of the device And can exhibit excellent performance. In the present invention, by using a metal ion having a bivalent or higher oxidation number as described above, the number of cations present can be reduced to 1/2 or less than that of an alkali metal ion. The occupied volume can be reduced and the pore volume can be improved. Furthermore, by reducing the ionic radius as described above, the occupied volume occupied by one cation can be reduced.

  Such an aluminosilicate-based zeolite can be produced by a substitution method or a synthesis method, but the substitution method is preferably used from the viewpoint of ease. For example, after hydrothermal synthesis of an aluminosilicate in which the cation in the counter ion is sodium or potassium by a conventional method, at least a part of sodium or potassium is ion-exchanged (that is, replaced with the metal ion) described above. The method is preferred.

  Here, a commercial item can be used for the aluminosilicate whose cation in a counter ion is sodium or potassium. The above substitution can be performed by, for example, mixing and stirring in an aqueous solution of a compound containing a predetermined metal at about 30 to 90 ° C. and ion exchange. Examples of the compound include chlorides, hydroxides, nitrates, acetates, carbonates and the like, and an aqueous solution is prepared and used.

  Such an aluminosilicate zeolite of the present invention is used as a desiccant for carbon dioxide refrigerant in a conventional refrigeration cycle including a compressor, a condenser, a decompression device, an evaporator, and the like. The storage method itself as a desiccant can be a conventional method. For example, the container filled with the desiccant of the present invention can be connected to the flow path of the carbon dioxide refrigerant by piping.

The refrigeration cycle according to the present invention includes an air conditioner, particularly an in-vehicle air conditioner, or a water heater,
Etc. can be suitably used.

Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
5.0 g of commercially available Na-A-type zeolite (pore diameter 0.4 nm) was added to 50 mL of 0.1 mol / L MgCl ₂ aqueous solution, and stirring at 80 ° C. for 5 hours was repeated 5 times to obtain maximum Na ⁺ Of which zeolite was substituted with Mg ²⁺ (pore size> 0.4 nm). The relationship between the Mg substitution rate (%) of the obtained zeolite and the saturated adsorption amount (g water / g zeolite) when used as a desiccant for the carbon dioxide refrigerant was as follows.

1 When the Mg substitution rate is 0 (Na100%), the saturated adsorption amount is 0.22.
2 When the Mg substitution rate is 38 (Mg38 / Na62%), the saturated adsorption amount is 0.25.
3 When the Mg substitution rate is 53 (Mg53 / Na47%), the saturated adsorption amount is 0.27.
4 When the Mg substitution rate is 68 (Mg68 / Na32%), the saturated adsorption amount is 0.27.
5 When the Mg substitution rate is 89 (Mg89 / Na11%), the saturated adsorption amount is 0.30.
Example 2
Using an aqueous calcium chloride solution, a Ca-substituted zeolite was obtained in the same manner as in Example 1. The amount of saturated adsorption also increased with increasing Ca substitution rate.

  ADVANTAGE OF THE INVENTION According to this invention, the subject in the increase in the amount of water permeation in the refrigerating cycle using the zeolite which the adsorption amount of the water per unit quantity improved as a desiccant and using a carbon dioxide as a refrigerant | coolant can be solved. Therefore, the amount of desiccant used can be reduced, and the refrigeration cycle using carbon dioxide as a refrigerant can be made compact, and further contributed to in-vehicle use.

Claims (7)

  An aluminosilicate system having a pore size of 0.3 nm or more; and a part or all of cations in the counter ion are metal ions having an ionic radius smaller than that of potassium ions and having an oxidation number of 2 or more. A refrigeration cycle using carbon dioxide as a refrigerant, wherein zeolite is used as a desiccant for the carbon dioxide refrigerant.   The refrigeration cycle using carbon dioxide as a refrigerant according to claim 1, wherein the metal ions are alkaline earth metal ions.   The refrigeration cycle using carbon dioxide as a refrigerant according to claim 2, wherein the alkaline earth metal ions are magnesium ions or calcium ions.   The refrigeration cycle using carbon dioxide as a refrigerant according to any one of claims 1 to 3, wherein the aluminosilicate zeolite has an LTA type or faujasite type structure.   An air conditioner using the refrigeration cycle according to claim 1.   An in-vehicle air conditioner using the refrigeration cycle according to claim 1.   A water heater using the refrigeration cycle according to claim 1.