JP2003148755A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve safety for refrigerant leakage of an air conditioner for a domestic use, using a refrigeration cycle using a HC refrigerant to be a combustible refrigerant. SOLUTION: A pipe diameter of a heat exchanger is thinned to reduce sealed quantity of the refrigerant. Pressure is made low to reduce refrigerants entering a compressor. The sealed quantity of the refrigerant is reduced down to about <=185 g by eliminating liquid parts of a pipe in the refrigeration cycle.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an air conditioner using an HC refrigerant which is a flammable refrigerant.

[0002]

2. Description of the Related Art A conventional air conditioner uses an HCFC refrigerant R
22 (chlorodifluoromethane, CHClF ₂ ) has been widely used. However, due to the fear of affecting the ozone layer depletion of the earth, chlorine-free HFC refrigerants R32 (difluoromethane, CH ₂ F ₂ ), R125 (pentafluoromethane) are used. _{ethane, H 3 -CHF 2), R134a} (1,1,1,2-
_{Tetrafluoroethane,} F ₃ -CH 3 mixed refrigerant _-CH 2 F) or the like has been considered. For small home air conditioners, the HFC refrigerant R410a (R32 (50%), R1
25 (50%) is being used as a substitute refrigerant for the refrigerant R22 in terms of prevention of ozone layer depletion, performance and safety.

Here, the HFC refrigerant, for example, R410a refrigerant, has the effect on global warming of the conventional HCFC refrigerant R
It has a drawback that it is close to 22. H is a refrigerant that has a small impact on global warming and does not cause ozone depletion.
Although there is a C refrigerant, it has the drawback of being highly flammable.

HC (hydrocarbon) for the refrigeration cycle
When a refrigerant is used, the refrigerant is flammable, so a safety device for flammability in the case where the HC refrigerant leaks from the refrigeration cycle to the outside is required.

As a conventional technique of this type, a structure for detecting the time-dependent change of the hydrocarbon concentration and discharging the HC refrigerant to the outside is disclosed in Japanese Patent Application Laid-Open No. 10-300294. Further, the function of collecting the HC refrigerant in the outdoor unit and preventing it from leaking into the room is disclosed in JP-A-6-180166.
It is disclosed in the publication.

[0006]

However, when the refrigerant to be sealed in the refrigerating cycle of the refrigerating apparatus is the HC refrigerant, even if an HC refrigerant sensor is provided to detect the leakage and take measures to prevent flammability, this is sufficient. Is difficult to prevent. That is, if the HC refrigerant sensor malfunctions and refrigerant leakage is not sufficiently detected, it is impossible to completely prevent flammability.

An object of the present invention is to eliminate the problem of flammability of a refrigeration system using an HC refrigerant.

[0008]

The object is to have a refrigeration cycle in which a compressor, an outdoor heat exchanger, a pressure reducer, and an indoor heat exchanger are connected in this order by connecting pipes, and H is used as a refrigerant.
In an air conditioner using C refrigerant, the diameter of the indoor heat exchanger pipe is 5.4 mm or less, and the stage pitch is 20 mm.
This is achieved by the above.

That is, by narrowing the pipe diameter of the heat exchanger used for the condenser and the evaporator, the amount of HC refrigerant enclosed in the refrigeration cycle is reduced, and even when the refrigerant in the refrigeration cycle leaks into the room, No flammable space was created in the room.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a refrigeration cycle of a general household air conditioner.

1 is a compressor, 2 is a refrigerant switching four-way valve, 3 is an outdoor heat exchanger, 4 is a pressure reducing valve, 5 is an indoor heat exchanger, and 6
Is an outdoor blower fan, 7 is an indoor blower fan, and among the outdoor units 8 installed on the outdoor side, there are a compressor 1, a four-way valve 2, an outdoor heat exchanger 3, a pressure reducing valve 4, and an outdoor side. Blower fan 6
The indoor heat exchanger 5 and the indoor blower fan 7 are housed in the indoor unit installed on the indoor side.
The outdoor unit 8 and the indoor unit 9 are connected by connection pipes 10 and 11.

In such a separate type air conditioner, the air conditioner has the ability to cool and heat 6 to 16 tatami mats as the size of the room, and R410a of HFC refrigerant is used as the refrigerant circulating in the refrigeration cycle. Using
For example, as a result of investigating the distribution of the refrigerant to each part when the indoor side is heated, it is in a state like NO1 in Table 1.

[0013]

[Table 1] 51% is distributed in the indoor heat exchanger 5 (condenser), 17% in the outdoor heat exchanger 3 (evaporator), 8% in the compressor 1, and 24% in other (connection pipes, etc.). A total of about 1050 g of the refrigerant is enclosed.

As a result of investigating the distribution to each portion when propane of HC refrigerant was used in such a refrigeration cycle, Table 1
It was in a state like NO2. When propane was used as the refrigerant, the amount of the refrigerant enclosed in the refrigeration cycle was significantly reduced to about 484 g, which is about 46%.

The main cause of the reduced amount of refrigerant enclosed is
This is because, as shown in Table 2, when R22 and propane refrigerant are compared, the density of liquid and gas is about 1/2, which is smaller than that of propane.

[0016]

[Table 2] The reason why the amount of refrigerant inside the compressor 1 is not decreased is that the amount of gas entering the space inside the compressor 1 is decreased, but the amount of refrigerant dissolved in the refrigeration oil (not shown) inside the compressor 1 is , R2
It is considered that the amount of propane refrigerant is larger than that of No. 2.

On the other hand, the minimum explosion concentration (LEL: Lower Explosion Le) of propane which is an HC refrigerant.
vel) is 2.0%, and when this amount is calculated by the size of the room, it becomes as shown in Table 3.

[0018]

[Table 3] The volume of the room when the size of the room changes to 6, 8, 12, and 16 tatami, and the height of the room is 2.4 m, 23.
The 3,31.1,46.7,62.2m ^3.

The minimum explosive refrigerant amount of propane corresponding to the size of this room is 932, 1160, 1720, 228.
When considering LEL ₀ as a practical LEL from the viewpoint of further safety, LEL ₀ = LEL × 20% is considered (safety factor 5 times).
It becomes 6,232,344,456g.

Therefore, in order to prevent the accident of fire such as explosion due to HC refrigerant leaking to the indoor side, the amount of refrigerant to be used in the refrigeration cycle of the home air conditioner is set as a safety amount in terms of safety.
Should be no more than about 185 g.

In Table 3, it can be seen that the amount of refrigerant entering the compressor 1 can be reduced to 19 g as shown in NO3 of Table 3 by significantly reducing the gas density in the compressor by reducing the pressure in the compressor 1. It was The amount of the refrigerant in the connection pipe or the like is the same as the amount of the refrigerant contained in the pipe 11 between the indoor heat exchanger 5 and the pressure reducer 4 as the liquid refrigerant between the indoor heat exchanger 5 and the pressure reducer 4. Since the inside of the pipe 10 can be made into a two-phase liquid by providing the throttle 12 which becomes a resistance, the refrigerant is
It was found that it could be significantly reduced to 5 g. Further, when the pipes of the heat exchangers of the indoor heat exchanger 5 and the outdoor heat exchanger 3 have an outer diameter of 5.4 mm and an inner diameter of 4.8 mm, the refrigerant amount in the heat exchanger becomes about 1/2 or less, Like NO3 of 3 194
It turned out to be g.

The specifications of the indoor heat exchanger used for NO3 in Table 1 are shown as NOII in Table 4.

[0023]

[Table 4] In the heat exchanger specifications in Table 4, NOIII and NOIV indicate the specifications in which the heat exchanger performance is the same and the pipe inner volume is reduced. The specifications of NOIII and NOIV are such that the internal volume is 91% and 81% with respect to NOII, and the amount of refrigerant enclosed can be reduced.

However, if the stage pitch of the pipe increases, the fin efficiency decreases, so that the fin area needs to be increased, and the fin row pitch increases, resulting in a heat exchanger having a large depth. It is against the compactness.

Table 5 shows the amount of refrigerant enclosed when the heat exchangers NOII, NOIII and NOIV are embedded.

[0026]

[Table 5] It has been found that when a heat exchanger having a large pipe stage pitch, such as NOIII and NOIV in Table 5, is used, the refrigerant charge amount can be suppressed to 185 g or less.

As described above, H is reduced by reducing the diameter of the heat exchanger of the refrigeration cycle, lowering the pressure of the compressor, and gasifying the connecting piping.
A safe air conditioner that can reduce the amount of refrigerant enclosed in a refrigeration cycle for an air conditioner using C refrigerant to a small amount that can prevent a fire such as an explosion even if it leaks indoors. Can be provided.

Here, the refrigerant filling amount is reduced to a safe refrigerant amount by reducing the diameter of the heat exchanger, lowering the pressure of the compressor, and liquefying the two-phase liquid portion of the pipe. If it is downsized, the amount of refrigerant enclosed in the refrigeration cycle can be further reduced, so it is not possible to create an air conditioner with excellent safety without combining all of these technologies.For example, downsizing of the heat exchanger It is also possible to realize with a smaller diameter.

[0029]

As described above, according to the present invention, in the air conditioner using the HC refrigerant which does not have a harmful effect on the ozone layer and has a small effect on global warming, the heat exchanger has a small diameter and the compressor has a small diameter. Air conditioning that uses technologies such as low pressure and two-phase liquefaction of piping to significantly reduce the amount of refrigerant filled in the refrigeration cycle and improve safety against fire even if refrigerant leaks to the indoor side. Can be an opportunity.

[Brief description of drawings]

FIG. 1 is a refrigeration cycle diagram for an air conditioner using a flammable refrigerant according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Four-way valve, 3 ... Outdoor heat exchanger, 4 ... Decompressor, 5 ... Indoor heat exchanger, 6 ... Outdoor blowing fan, 7
… Indoor fan, 8… outdoor unit, 9… indoor unit, 10,
11 ... Piping, 12 ... Throttling.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nobuo Inagaki             800 Tomita, Ohira-cho, Shimotsuga-gun, Tochigi             Hitachi Co., Ltd., Cooling & Heat Division (72) Inventor Isao Yokoshima             800 Tomita, Ohira-cho, Shimotsuga-gun, Tochigi             Hitachi Co., Ltd., Cooling & Heat Division (72) Inventor Shigeyuki Sasaki             502 Kintatemachi, Tsuchiura City, Ibaraki Japan             Tate Seisakusho Mechanical Research Center (72) Inventor Mitsuo Kudo             502 Kintatemachi, Tsuchiura City, Ibaraki Japan             Tate Seisakusho Mechanical Research Center F-term (reference) 3L051 BE04 BF01

Claims (3)

[Claims] 1. An air conditioner having a refrigeration cycle in which a compressor, an outdoor heat exchanger, a pressure reducer, and an indoor heat exchanger are connected by connecting pipes in this order, and HC refrigerant is used as a refrigerant. An air conditioner in which the diameter of the indoor heat exchanger pipe is 5.4 mm or less and the stage pitch is 20 mm or more. 2. The air conditioner according to claim 1, wherein the inside of the compressor is of a low pressure type. 3. The air conditioner according to claim 1, wherein the inside of the compressor is of a low pressure type, and a throttle is provided in a part of a pipe connecting the pressure reducing valve and the indoor unit.