JPH1114193A - Thermal storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sustain the ice making rate stably by employing a plastic/metal composite tube, produced by coating the inner and outer surfaces of a metal tube with a polyolefin based plastic layer, as a circulation tube thereby preventing the thermal conductivity from lowering due to corrosion on the inner surface of the circulation tube even if a coolant mixed with a water containing lubricant is employed. SOLUTION: In a system for storing heat by freezing the water in a heat storage tank 1 with a coolant flowing through a circulation tube 2 arranged therein, a plastic/metal composite tube produced by coating the inner and outer surfaces of a metal tube with a polyolefin based plastic layer is employed as the circulation tube 2. In this regard, the thickness of each plastic layer of the plastic/metal composite tube is set in the range of 0.006-0.075 times (0.04 times is optimal) of the outside diameter of the composite tube and the thickness of the metal tube is set in the range of 0.006-0.019 times (0.01 times is optimal) of the outside diameter of the composite tube. According to the arrangement, the ice making rate can be sustained stably by preventing the thermal conductivity from lowering due to corrosion on the inner surface of the circulation tube 2 even if a coolant mixed with a water containing lubricant is employed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ice heat storage system used for an air conditioner of a building or the like.

[0002]

2. Description of the Related Art There is a case where an ice heat storage system utilizing the latent heat of ice is used as a heat storage system used for air conditioning equipment in a building or the like. In this ice heat storage system, a circulation pipe as an evaporator of a refrigerant circulation system is disposed in a water tank (heat storage tank). In the refrigerant circulation system, compressed refrigerant from the compressor is radiated and liquefied by a condenser. The liquefied refrigerant is expanded through the expansion valve, and the water around the evaporator (circulation tube) is frozen while passing through the evaporator, and heat is stored by the adhesion of the ice. The compressor is sucked in, and thereafter the refrigerant is circulated as one cycle. And the cold water of a heat storage system is circulated to an air conditioner as needed, and indoor air conditioning is performed by a heat exchanger.

The circulation pipe as the evaporator is disposed in a water tank at a predetermined arrangement and density, requires good thermal conductivity and corrosion resistance to water, and is a metal pipe having an outer surface coated with a plastic layer. Are preferred.

[0004]

Conventionally, the above-mentioned refrigerant has C
Fluorocarbon compounds such as FC (chlorofluorocarbon) -12 and HCFC (hydrochlorofluorocarbon) -22 have been used, but recently, the destruction of the global environment due to the destruction of the ozone layer by these chlorofluorocarbons has become global. And is being replaced by new refrigerants.

The conditions required for this alternative refrigerant include:
It is required that the ozone depletion potential and the global warming potential are 0 to very low, and HFC-32 (C
_{H 2 F 2), HFC-} 125 (CHF 2 CF 3), HFC-
134a (CH ₂ FCF ₃ ). It is necessary to mix a lubricating oil with the refrigerant in order to prevent abrasion of movable parts of the refrigerant circulation system and to prevent blockage of the circulation path. Conventionally, mineral oil is used as the lubricating oil. However, mineral oil has poor compatibility with the new refrigerant, and polyalkylene glycols and polyol esters are suitable as lubricating oils for the new refrigerant.

However, these lubricating oils (polyalkylene glycols, polyol esters, etc.) have remarkably high hygroscopicity as compared with conventional mineral oils (the mineral oil has a saturated water content of 50 ppm or less). On the other hand, for example, the saturated water content of a polyol ester system is 2000 ppm or more), and there is a concern that the ice making efficiency may be reduced due to inner surface corrosion (including sludge generation by metal soap or the like) in the above-mentioned circulation pipe.

An object of the present invention is to prevent a decrease in thermal conductivity due to corrosion of the inner surface of a circulating pipe and to stably maintain an ice-making rate even in a case where an ice heat storage system uses a refrigerant containing water-containing lubricating oil. It is to provide a heat storage system. A further object of the present invention is to improve the ice making rate, workability, mechanical stability, and the like of the circulation tube in addition to the above objects.

[0008]

According to the present invention, there is provided a heat storage system for storing heat by freezing water in a heat storage tank with a refrigerant flowing through a circulation pipe disposed in the heat storage tank. And a plastic / metal composite pipe having an outer surface coated with a polyolefin-based plastic layer as the circulating pipe, wherein the thickness of each plastic layer of the plastic / metal composite pipe is the outer diameter of the composite pipe. And the thickness of the metal tube is preferably 0.006 to 0.019 times the outer diameter of the composite tube.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a heat storage system according to the present invention, which is a closed type. In FIG.
1 is a closed water tank. Reference numeral 2 denotes a circulation pipe disposed in the water tank 1, and as shown in FIG. 2, a plastic / metal composite pipe in which polyolefin-based plastic layers 22 and 23 are coated on the inner and outer surfaces of a metal pipe 21 are multistage zigzag or coiled. It is arranged in a shape pattern.

The arrangement pattern includes a multi-stage alternating reverse flow pattern already proposed by the applicant, that is, "a plurality of circulation pipes are zigzag in a plane in which each bent portion is parallel to each other. The adjacent circulation pipes are continuously bent so as to be located in a zigzag pattern, and the refrigerant circulation direction of the adjacent circulation pipes is reversed.
No. 36) ".

In FIG. 1, 3 is a compressor connected to the circulation pipe 2, 4 is a condenser, and 5 is an expansion valve. 6 is a circulation pump, 7 is an air conditioner. When the heat storage system is in operation, the refrigerant at the outlet of the compressor 3 is in a high-temperature, high-pressure heating state, which is cooled to a saturated liquid state by the condenser 4, and the refrigerant liquid is depressurized by the expansion valve 5, While the depressurized wet steam refrigerant passes through the circulation pipe 2, it absorbs heat from the contact water on the outer surface of the circulation pipe 2 to freeze water outside the circulation pipe 2, and further compresses the refrigerant that has passed through the circulation pipe 2. The refrigerant is sucked into the device 3, and the refrigerant is circulated with the above as one cycle.

Heat is stored in a frozen state outside the circulation pipe 2, and an air conditioner 7 is operated by a circulating pump 6 of cold water in the water tank 1.
Air conditioning is performed by circulation to the air. As the refrigerant, HFC-32 (CH ₂ F ₂ ) and HFC-125 have recently been used.
(CHF ₂ CF ₃ ), HFC-134a (CH ₂ FCF ₃ )
The new refrigerant is mixed with polyalkylene glycol, polyol ester, etc. as a lubricating oil, and a large amount of water is added to the lubricating oil mixed refrigerant due to the high hygroscopicity of the lubricating oil. It is contained, and contact between the inner surface of the circulation pipe and moisture is inevitable.

However, in the heat storage system according to the present invention, since a plastic / metal composite tube in which a chemically stable polyolefin-based plastic layer is coated on the inner surface of the metal tube is used for the circulation tube, lubricating oil mixing is performed. Even if a large amount of water is contained in the refrigerant, due to the chemical stability of the polyolefin-based plastic, the inner plastic layer can be stably retained by eliminating hydrolysis deterioration, etc. To eliminate the fear of corrosion.

Of course, since the outer surface of the metal tube is also coated with a polyolefin-based plastic layer, corrosion of the outer surface of the metal tube can be eliminated. Therefore, in the heat storage system according to the present invention, even if a refrigerant in which a hygroscopic lubricating oil is mixed is used, the thermal conductivity of the metal tube of the plastic / metal composite tube is reduced to the original high thermal conductivity without causing corrosion. It can maintain and guarantee a high ice making rate for a long time.

Aluminum metal, copper alloy, steel, etc. can be used for the metal pipe of the above-mentioned circulating pipe, and polyethylene, cross-linked polyethylene,
Polypropylene, polyvinyl alcohol, and the like can be used. Further, the metal pipe of the circulation pipe and the polyolefin-based plastic layer can be bonded with an adhesive. If the thickness of the plastic layer of the plastic / metal composite pipe used for the circulation pipe is too thick, the thermal conductivity of the plastic / metal composite pipe becomes low, which is disadvantageous in ice making efficiency,
If the thickness is too small, the mechanical strength of the anticorrosion layer is insufficient, and it is difficult to satisfactorily prevent the above-mentioned corrosion. Accordingly, the thickness of each of the inner plastic layer and the outer plastic layer is 0.006 to 0.075 of the outer diameter of the plastic / metal composite pipe.
Preferably, it is set to 0.04 times, and most preferably, it is set to 0.04 times.

On the other hand, if the thickness of the metal tube of the plastic / metal composite tube is too thin, the thermal conductivity of the entire plastic / metal composite tube becomes low, which is disadvantageous in terms of ice making efficiency. Bending becomes difficult. Therefore, the thickness of the metal pipe is preferably set to 0.006 to 0.019 times the outer diameter of the plastic / metal composite pipe.
It is optimal to set it to 01 times.

The thickness of each plastic layer of the plastic / metal composite tube is 0.006 to 0.075 of the outer diameter of the composite tube.
Twice as thick as the outer diameter of the composite tube.
Under 019 times, it is possible to guarantee a sufficient ice making rate of the circulation pipe,
It can be confirmed from the following examples that the circulation pipe can be easily bent and the circulation pipe can be stably held in the water tank without using a supporting member.

[0018]

【Example】

[Example 1] As a plastic / metal composite tube, a metal tube having an aluminum alloy tube having a thickness of 0.1 mm and inner and outer polyolefin-based plastic layers each being a low-density polyethylene layer having a thickness of 0.1 mm were used. The outer diameter of this plastic / metal composite tube is 16 mm, and therefore, the thickness of the metal tube and the thickness of each polyolefin-based plastic layer are 0.00625 times the outer diameter of the composite tube.

This plastic / metal composite pipe is bent into a circulating pipe having the above-mentioned alternate reverse flow pattern, and has a capacity of 4.
0m ³ placed in a heat storage tank, and a brine of -5 ° C was flowed.
An ice making test was performed. Processing into the circulation tube was extremely easy, and the circulation tube could be held sufficiently stably in the heat storage tank without using a support member. Also, assuming that the ice making rate when the inner and outer plastic layers are omitted is 100%, the ice making rate is 95%, which is an extremely excellent ice making rate.

Embodiment 2 In the plastic / metal composite tube, the metal tube is an aluminum alloy tube having a thickness of 0.3 mm, and the inner and outer polyolefin-based plastic layers are 1.2 m in thickness.
m low-density polyethylene layer was used. The outer diameter of this plastic / metal composite pipe is 16 mm, and therefore, the thickness of the metal pipe is 0.0018 times the outer diameter of the composite pipe, and the thickness of each polyolefin-based plastic layer is 0.075 times the outer diameter of the composite pipe. It is.

In the same manner as in Example 1, this plastic / metal composite pipe was bent into a circulation pipe to assemble a heat storage system. Although processing into the circulation pipe was somewhat difficult, it could be processed by a general-purpose vendor, and the circulation pipe could be extremely stably held in the heat storage tank without using a support member. In addition, the ice making rate was 70%, which was almost good.

Example 1 was repeated except that the thickness of the metal tube of the plastic / metal composite tube was 0.025 times the outer diameter of the composite tube, and the thickness of each polyolefin-based plastic layer was 0.125 times the outer diameter of the composite tube. Or when the heat storage system was assembled by bending the circulation pipe in the same manner as in 2, the ice making rate was 6%.
Although it was 0%, it was extremely difficult to bend into a circulation tube.

[0023]

In the heat storage system according to the present invention,
Even if a new refrigerant mixed with a hygroscopic lubricating oil such as polyalkylene glycol or polyol ester is used as a substitute for chlorofluorocarbon, the circulation pipe can be maintained at high thermal conductivity without fear of corrosion of the inner surface, and stable ice making for a long time Can maintain the rate. In addition, the bending of the circulation pipe is easy, the circulation pipe can be stably supported in the heat storage tank without using a support member, and the heat conduction per unit length of the circulation pipe can be increased. Can be shortened, and there is also an advantage that simplification of the assembling work of the heat storage system, simplification of the support structure of the circulation pipe, downsizing of the circulation pipe, and the like can be achieved.

[Brief description of the drawings]

FIG. 1 is a drawing showing an example of a heat storage system according to the present invention.

FIG. 2 is a cross-sectional view showing a plastic / metal composite pipe used for a circulation pipe in the present invention.

[Description of Signs] 1 Heat storage tank 2 Circulation pipe 3 Compressor 4 Condenser 5 Expansion valve 6 Circulation pump 7 Air conditioner 21 Metal pipe 22 Plastic layer 23 Plastic layer

Claims (2)

[Claims] 1. A system for storing heat by freezing water in a heat storage tank with a refrigerant flowing through a circulation pipe disposed in the heat storage tank, wherein the metal pipe has an inner surface and an outer surface coated with a polyolefin-based plastic layer. A heat storage system using a metal composite tube as the circulation tube. 2. The thickness of each plastic layer of the plastic / metal composite tube is 0.006 to 0.075 of the outer diameter of the composite tube.
Twice as thick as the outer diameter of the composite pipe.
The heat storage system according to claim 1, wherein the heat storage system is up to 0.019 times.