Patent Application
20170146274
The present invention relates to an air-conditioning apparatus using flammable refrigerant and a method of installing the same.
Until now, there has been an air-conditioning apparatus executing a refrigeration cycle by using “hydrofluorocarbon (HFC) refrigerant” such as nonflammable R410A. The R410A is different from “hydrochlorofluorocarbon (HCFC) refrigerant” such as a conventional R22, zero in ozone depleting potential (ODP), never destroy the ozone layer, but high in global warming potential (hereinafter referred to as GWP). Therefore, a change of the HFC refrigerant such as the R410A high in GWP to refrigerant low in GWP (hereinafter referred to as low GWP refrigerant) has been made as one of global warming preventions.
There has been hydrocarbon (HC) refrigerant such as R290 (C3H8; propane) or R1270 (C3H6; propylene) being natural refrigerant as candidates for the low GWP refrigerant. Unlike the nonflammable R410A, the HC refrigerant is high in flammability, so that care and precaution must be taken not to leak refrigerant.
As candidates for the low GWP refrigerant, there has been the HFC refrigerant having no double bond of carbons in composition such as, for example, R32 (CH2H2; difluoro-methane) being lower in GWP than the R410A.
Furthermore, as a similar candidate for refrigerant, there has been halogenated hydrocarbon being one type of the HFC refrigerant similar to the R32 and having double bond of carbons in composition. As such halogenated hydrocarbon, there has been known, for example, HFO-1234yf (CF3CF═CH2; tetrafluoropropene) or HFO-1234ze (CF3—CH═CHF). The HFC refrigerant having double bond of carbons in composition is often represented as “HFO refrigerant” using “O” of olefin (because unsaturated hydrocarbon having double bond of carbons is called olefin) to discriminate from the HFC refrigerant having no double bond of carbons in composition, such as the R32.
The low GWP refrigerant such as the HFC refrigerant and the HFO refrigerant is not flammable than the HC refrigerant such as the R290 (C3H8; propane) being natural refrigerant, but slightly flammable unlike the nonflammable R410A. For this reason, care must be taken not to leak refrigerant, as is the case with the R290. Hereinafter, even the refrigerant that is slightly flammable is referred to as “flammable refrigerant.”
Patent Literature 1, for example, discusses a method of decreasing the risk of ignition caused in a case where the flammable refrigerant leaks by any chance, such that a refrigerant amount calculated from an installation floor space manually input according to a relational expression uniquely determined with reference to the following formula I related to an allowable refrigerant amount per room mmax [kg] being not ventilated and defined by International Electrotechnical Commission IEC60335-2-40 is compared with a refrigerant amount in an air-conditioning apparatus and the refrigerant exceeding the allowable refrigerant amount mmax is discharged and transferred to a surplus refrigerant storage unit.
m
max=2.5×(LFL)1.25×h0×(A)0.5 (Formula I)
Here, the installation height h0 is 0.6 m in a floor type, 1.8 m in wall type, 1.0 m in window type, and 2.2 m in ceiling type.
Patent Literature 1: Japanese Patent No. 3477184
However, in the technique using the formula I discussed in Patent Literature 1, a term related to a leak speed of the refrigerant is not included in the formula I, so that there is a concern that the refrigerant amount may be excessively restricted (discharged). In an air-conditioning apparatus for business use whose refrigerant pipe for connecting an outdoor unit to an indoor unit is long and which may be more often installed to a high heat load property such as a commercial kitchen than a home-use air-conditioning apparatus, even if a technique for decreasing the refrigerant to be enclosed is fully made use of, it is difficult to satisfy the formula I while the required capacity is exhibited.
The present invention has been made to solve the above problems and has an objective to provide an air-conditioning apparatus filling an effective refrigerant amount and securing safety in the air-conditioning apparatus using the flammable refrigerant being higher in density than air under the atmospheric pressure.
The air-conditioning apparatus according to one embodiment of the present invention includes an indoor unit on which an indoor heat exchanger is mounted and uses the flammable refrigerant being higher in density than air under the atmospheric pressure. The indoor unit is installed at an installation height of h0 [m] or more, (which complies with IEC60335-2-40 or may be a value agreeing with an opening position of an air inlet and an air outlet or an arrangement position of a refrigerant circuit) in an installation floor space A [m2]. The refrigerant amount M [kg] to be filled falls within the following formula II. Formula II is M≦α×G−β×h0×A. Parameters are as follows; LFL is a lower flammability limit of the flammable refrigerant [kg/m3], A is an installation floor space A [m2] of the indoor unit, G is an assumed maximum leak speed of the refrigerant [kg/h], and α is a positive constant of the refrigerant, mainly correlating to the LFL (determined by an experiment). β is a positive constant of the refrigerant, mainly correlating to the density (determined by an experiment).
The method of installing the air-conditioning apparatus according to one embodiment of the present invention uses the air-conditioning apparatus.
According to the air-conditioning apparatus of an embodiment of the present invention, even if the flammable refrigerant being higher in density than air under the atmospheric pressure is used, the air-conditioning apparatus secures safety while filling an effective refrigerant amount.
Embodiments of the present invention will be described hereinafter with reference to the drawings as necessary. The size of component members in the following drawings including
The air-conditioning apparatus 100 has been designed on the assumption that the flammable refrigerant is used and includes an indoor unit 1 shown in
All the indoor units 1 shown in
The heat exchanger 2 acts as one element of the refrigerant circuit along with a compressor 11 housed in the outdoor unit 10, a heat exchanger 12 and an expansion valve 13 on the outdoor side. When a room space is heated, refrigerant flows through a compressor 11, the heat exchanger 2, an expansion valve 13, and the heat exchanger 12 in this order. In other words, the heat exchanger 2 and the heat exchanger 12 are caused to act as a condenser and an evaporator respectively, and room air passing through the heat exchanger 2 is provided with heating energy to warm the air, thereby performing a heating operation. When a room space is cooled, refrigerant flows through the compressor 11, the heat exchanger 12, the expansion valve 13, and the heat exchanger 2 in this order. In other words, the heat exchanger 2 and the heat exchanger 12 are caused to act as an evaporator and a condenser respectively, and room air removes cooling energy from the refrigerant passing through the heat exchanger 2 to be cooled, thereby performing a cooling operation.
When the refrigerant leaks from the refrigerant circuit in the indoor unit 1, in general, a larger amount of refrigerant leaks from the side lower in height (hereinafter referred to as floor height) of an opening portion such as the air inlet 3 and the air outlet 4. Furthermore, the floor height at the place where leakage occurs may affect. It is presumed that the flammable refrigerant is used in the air-conditioning apparatus 100, so that a flammable area may be generated in a room space depending on a leak amount.
The air-conditioning apparatus 100 includes an input unit to which M, A, LFL, h0, G, α, and β are input, a unit configured to detect and monitor as to whether the formula II is satisfied (control apparatus 18), and a notification unit configured to making notification when the control apparatus 18 detects that a set threshold value is exceeded. If any improvement cannot be found in a certain period of time after the notification, the control apparatus 18 makes the air-conditioning apparatus 100 inoperative. The control apparatus 18 is composed of hardware such as a circuit device actualizing the above functions, or software for executing on an arithmetic unit such as a microcomputer or a central processing unit (CPU) for example.
Where, h0 is a value basically conforms to IEC60335-2-40. Alternatively, a floor height h0 (A) of the air inlet 3 or the air outlet 4 of the indoor unit 1 whichever is lower may be used.
Alternatively, a floor height h0 (B) of the refrigerant pipe 15 or refrigerant pipe fittings 16 of the indoor unit 1 whichever is lower may be used.
In general, in the wall type (
On the other hand, in the floor type indoor unit 1 (
In the present embodiment, the following indoor unit 1 is used as an experimental object.
In “the wall type” shown in
In “the ceiling type” shown in
In “the window type” shown in
In “the floor type” shown in
The minimum value of A is determined to be 4 m2 with reference to a required minimum floor space provided by bylaws. A ceiling height is determined to be 2.2 m or more with reference to Building Standards Act. At least, the indoor unit 1 provided with the heat exchanger 2 is installed at an installation height of h0 or more. Assumed leak speeds are taken as 5 kg/h, 10 kg/h, and 75 kg/h with reference to “Environment and New Refrigerant, International Symposium 2012” on page 98, issued by (corporate juridical person) The Japan Refrigeration and Air Conditioning Industry Association (JRAIA), and a median of 10 kg/h is taken as a standard value. The above reference describes that the majority of refrigerant leakage accidents occurred at a leak speed of 1 kg/h or less. Safety can therefore be secured at a leak speed of 5 kg/h.
The lower flammability limit (LFL) described in IEC60335-2-40 complies therewith. For example, LFL of R32=0.306 [kg/m3], LFL of propane (R290)=0.038 [kg/m3]. If IEC60335-2-40 describes nothing about the above, speculation is made from documents or experiments. HFO-1234yf is taken as 0.294 [kg/m3] because IEC60335-2-40 describes nothing about it.
The constants α and β are determined by refrigerant leak experiment results described below, but basically depend on refrigerant species. The constant a is influenced mainly by LFL and the constant β is influenced mainly by density (molecular weight), but details are not clear.
As shown in
The indoor unit 1 leaking the refrigerant is installed in the enclosed space 50.
A gas density sensor 51 is arranged at a predetermined height in the enclosed space 50. As an example,
Inside the indoor unit 1, a general capillary 53 is connected to a charge hose 55 by an opening and closing opening and closing valve 54. At this time, the charge hose 55 is connected to a charge hose 56 by an opening and closing opening and closing valve 57. The charge hose 55 is arranged to communicate inside and outside the enclosed space 50. The opening and closing valve 54 should lie inside the enclosed space 50 and the opening and closing valve 57 should lie outside the enclosed space 50. Furthermore, another end of the charge hose 56 that is not connected to the opening and closing valve 57 is connected to a main tap 59 of a refrigerant cylinder 58.
The capillary 53 functions to adjust a leakage speed in leaking the refrigerant. A general copper capillary may be used as it is, or a partially processed capillary may be used. A general TASCO TA-136A, for example, may be used as the charge hoses 55 and 56.
The opening and closing valve 57 is kept closed in a state where the opening and closing valve 57 is adjusted to the leakage speed targeted at a preliminary experiment and then the main tap 59 is opened. This state is kept, and the refrigerant cylinder 58 is placed on an electronic platform scale 60. While change in weight of the refrigerant cylinder 58 is always recorded using a personal computer, the opening and closing valve 57 is opened.
Thus, the refrigerant is leaked into the enclosed space 50 at the targeted leakage speed. The leakage speed can be estimated as an average leakage speed V [kg/h] from a gradient that temporal change in the weight of the refrigerant cylinder 58 is linearly approximated.
The preliminary experiment is performed using an experiment apparatus 200. The leakage speed can be adjusted by specifications (inside diameter and length) of the capillary 53 and a degree to which the opening and closing valve 54 is opened.
A refrigerant leakage amount can be adjusted by closing the opening and closing valve 57 when the electronic platform scale 60 reads the targeted weight.
The gas density sensors 51 are set at a predetermined height in the center part of the enclosed space 50. Detection results are continuously recorded by a personal computer. A gas sensor VT-1 for R32 (produced by New Cosmos Electric., Co., Ltd.), for example, may be used.
In the present embodiment, 14.4 vol % being the volume density LFL of R32 conforming to the IEC60335-2-40 is used as an index to display the volume density by the gas density sensor used for the R32. When the maximum density of R32 reaches 14.4 vol % or more, “present” is given as an evidence of generating a flammable area, and when the maximum density of R32 is less than 14.4 vol %, “absent” is given.
Confirmation was made that the flammable area is not generated in a range satisfying the formula I, however, as described in the paragraph [0009], the refrigerant amount may be excessively restricted, so that the confirmation is described as a comparative example.
Reason given that the example is performed in the case where leakage is not occurred from the actual apparatus (the refrigeration cycle apparatus such as the air-conditioning apparatus) as follows.
In the actual apparatus, almost all of refrigerant is stored in a compressor. For this reason, when the refrigerant is leaked from the actual apparatus into the room, the refrigerant will leak from the compressor. In this case, refrigerant gas leaking at a high speed because of high pressure in starting leakage lowers in internal pressure of the refrigerant circuit according as the refrigerant amount remained in a refrigeration cycle apparatus decreases, and the leakage speed is also lowered. Thereby, the leakage speed is changed by the leakage refrigerant amount, and the leakage amount is not known because the total amount is not discharged, which makes it difficult to obtain quantitative data for discussing safety.
The preliminary experiment was performed before the present embodiment is made. When the refrigerant whose amount is equal to that in the method shown in the present embodiment is leaked at substantially the same speed, confirmation was made that a room density in leaking the refrigerant from the actual apparatus was lower.
Tables 1 to 9 show a state of generation of a flammable area in leaking the R32, in a case where the wall-type indoor unit 1 is installed to one wall surface of the enclosed space 50 with the floor space (inside dimension) of 12 m2, 36 m2, and 64 m2 and a ceiling height of 2.5 m so that the lower end part of the indoor unit 1 has a floor height of 1.8 m, a leakage refrigerant amount is taken as 0.5 kg to 70.0 kg, an average leakage speed V is taken as 5 kg/h, 10 kg/h, and 75 kg/h, and installation floor heights for the gas density sensors are taken as 50 mm, 100 mm, 250 mm, 500 mm, 1000 mm, 1500 mm, and 2000 mm.
The examples are summarized in table 10 which lists an allowable refrigerant amount without a flammable area (M upper limit) and a relationship between mmax conforming to IEC60335-2-40 and the installation floor space A (M upper limit/A and mmax/A). Incidentally, mmax/A is as follows in accordance with the formula I.
Now, h0=1.8 m, so that mmax=1.024×(A)0.5.
When A=12 m2, mmax=1.02×120.5=3.53 [kg].
Therefore, mmax/A=3.53 [kg]/12 [m2]=0.294 [kg/m2].
When A=36 m2, mmax=1.02×360.5=6.12 [kg].
Therefore, mmax/A=6.12/36=0.170 [kg/m2].
When A=64 m2, mmax=1.02×640.5=8.16 [kg].
Therefore, mmax/A=8.16/64=0.128 [kg/m2].
Table 10 tells us the following.
(1) Leakage of the refrigerant in excess of mmax will not generate the flammable area.
(2) M upper limit needs to be decreased according as V increases. In other words, M upper limit needs to be decreased according as G increases.
(3) M upper limit/A (synonymous with “maximum value of M/A” in case A is constant) is constant in case V is constant, i.e., in case G is constant.
The above tells us that M/A has only to be taken as an index to perform management so that the flammable area is not generated. That is, at h0=1.8 [m], and at G=5 [kg/h], (the maximum value of M/A)=1.061 [kg/m2]; at G=10 [kg/h], (the maximum value of M/A)=0.75 [kg/m2]; and at G=75 [kg/h], (the maximum value of M/A)=0.350 [kg/m2].
It is easily assumable that the greater an assumed maximum leakage speed G, the greater the safety.
Table 11 also shows a state of generation of a flammable area in leaking the R32, in a case where the ceiling-type indoor unit 1 is installed to the center of the ceiling of the enclosed space 50 with the floor space (inside dimension) of 12 m2, 36 m2, and 64 m2 so that the lower end part of the indoor unit 1 has a floor height of 2.2 m, a leakage refrigerant amount is taken as 0.5 kg to 53.4 kg, an average leakage speed V is taken as 5 kg/h, 10 kg/h, and 75 kg/h, and installation floor heights for the gas density sensors are taken as 50 mm, 100 mm, 250 mm, 500 mm, 1000 mm, 1500 mm, and 2000 mm.
The above tells us a tendency similar to Example 1. That is, at h0=2.2 m and at G=5 [kg/h], (the maximum value of M/A)=1.30 [kg/m2]; at G=10 [kg/h], (the maximum value of M/A)=0.925 [kg/m2]; and at G=75 [kg/h], (the maximum value of M/A)=0.423 [kg/m2].
Table 12 also shows a state of generation of a flammable area in leaking the R32, in a case where the window-type indoor unit 1 is installed to a part of the wall of the enclosed space 50 with the floor space (inside dimension) of 12 m2, 36 m2, and 64 m2 so that the lower end part of the indoor unit 1 has a floor height of 1.0 m, a leakage refrigerant amount is taken as 0.5 kg to 53.4 kg, an average leakage speed V is taken as 5 kg/h, 10 kg/h, and 75 kg/h, and installation floor heights for the gas density sensors are taken as 50 mm, 100 mm, 250 mm, 500 mm, 1000 mm, 1500 mm, and 2000 mm.
The above tells us a tendency similar to Examples 1 and 2. That is, at h0=1.0 [m] and at G=5 [kg/h], (the maximum value of M/A)=0.591 [kg/m2]; at G=10 [kg/h], (the maximum value of M/A)=0.421 [kg/m2]; and at G=75 [kg/h], (the maximum value of M/A)=0.192 [kg/m2].
The floor-type indoor unit 1 shown in
As described above, Example 4 has provided the results similar to those in Examples 1 to 3 (the results that the flammable area was not generated even in the excess of mmax, M upper limit needs to be decreased according as G is increased, and G correlates to M/A).
In the examples in which h0 conforming to IEC60335-2-40 is equal to the installation height of the indoor unit (the floor height of the lower end of the indoor unit 1) in the tables 10 to 13, it is obvious that (M upper limit/A), i.e., (the maximum value of M/A) is always greater than (mmax/A). In this case, the greater the G, and the smaller the h0, the smaller (the maximum value of M/A) becomes.
Then, the relationship between the maximum value of M/A [kg/m2] and h0[m] in the average leakage speeds V (5 kg/h, 10 kg/h, and 75 kg/h) was investigated.
The maximum values of M/A in each V and h0 are plotted in the abscissa and in the ordinate respectively, thereby, the following relational expressions were obtained.
h
0 (V=5 [kg/h])=1.69×(M/A) (Formula IV)
h
0 (V=10 [kg/h])=2.38×(M/A) (Formula V)
h
0 (V=75 [kg/h])=5.21×(M/A) (Formula VI)
The relationship among the value of V, gradient of straight lines of Formulas IV to VI (=grad [m3/kg]=(h0·A)/M), and reciprocal of gradient of straight lines (=1/grad [kg/m3]=M/(h0·A) is given in table 16.
V and (1/grad) are plotted in the abscissa and in the ordinate respectively, which well agrees with power approximation and gives the following formula.
(1/grad)=M/(h0·A)=1.11×V−0.41
M=1.11×V−0.41×h0×A
Here, G is substituted for V, which gives the following formula.
M=1.11×G−0.41×h0×A (Formula VII)
where, M is a refrigerant amount [kg], G is an assumed maximum leak speed [kg/h], h0 is an installation height [m] and A is an installation floor space [m2].
The above description and M≦α×G−β×h0×A . . . (Formula III) show that a flammable area is not generated according to (Formula III) with α=1.11 and β=0.41 in the case of R32. This has shown the effectiveness of the present invention.
To ensure higher safety with reference to the results (in tables 13 to 15) that the lower end position (substantially equal to floor height) of the capillary 53 being the floor height of the refrigerant leakage position is changed in Example 4, h0 in (Formula II) may use the floor height (h0 (A)) of the air outlet 4 or the air inlet 3 whichever is lower or the floor height (h0 (B)) of the refrigerant pipe 15 or the refrigerant pipe fitting 16 whichever is lower instead of the value conforming to IEC60335-2-40.
Thereby, safety is further improved when the actual refrigerant leakage position (the floor height) is lower than the h0 conforming to IEC60335-2-40.
However, like A=64 [m2] and G=75 [kg/h] in table 15, there may be a range that substantially does not have a solution. This shows that h0=0.6 [m] at h0 (B)=0.15 [m] does not hold true any more at the time of a high speed leakage such as G=75 [kg/h], which does not have any influence on the effectiveness of the present invention.
As described in paragraph [0023], safety can be ensured enough at the assumed maximum leak speed G of 5 kg/h. However, G is taken as 10 kg/h to allow the generation of the flammable area to be suppressed in almost all the refrigerant leakage accidents. Particularly, in the floor-type indoor unit, h0 is made as lower as possible to further increase safety. In other words, the following further increases safety.
M/A≦1.30 [kg/m2] in h0=2.2 [m] or more
M/A≦0.925 [kg/m2] in h0=1.8 [m] or more
M/A≦0.421 [kg/m2] in h0=1.0 [m] or more
M/A≦0.252 [kg/m2] in h0=0.6 [m] or more
M/A≦0.189 [kg/m2] in h0=0.45 [m] or more
M/A≦0.0546 [kg/m2] in h0=0.15 [m] or more
The above measurements and approximations include errors, so that it is obvious that each value has more or less variation. So many data do not need to be taken, but it is assumable that the more the data used for the approximation, the smaller the error.
Furthermore, in table 16, another approximation can be made. For example, the average leakage speed V [kg/h] and grad [m3/kg] are plotted in the abscissa and in the ordinate respectively to perform a log approximation, giving the following formulas.
grad=(h0·A)/M=1.3×Ln (V)+0.5 (Formula VIII)
where Ln (V) is a natural logarithm of V.
Thereby, the following formula is given,
M={1/(1.3×Ln (V)+0.5)}×h0×A (Formula IX)
which substitutes G for V.
Thereby, the following formula is given,
M{1/(1.3×Ln (G)+0.5)}×h0×A (Formula X)
which can also suppress the generation of the flammable area.
Other than the above, various approximations are can be made such as, grad=0.9×V0.41, or 1/grad=−0.14×Ln (V)+0.8, however, it is obvious that the approximation highest in versatility and accuracy is (Formula VII).
The experiment made in Embodiment 1 was conducted by using HFO-1234yf substituted for the refrigerant gas.
As a result, the following formula was obtained.
2.5×(LFL)125×h0×A0.5≦M≦α×G−β×h0×A
where, α=0.78, and β=0.34
The lower limit is as follows,
2.5×(0.294 [kg/m3])1.25×h0=2.5×0.217×h0=0.54 [kg],
which confirmed that the advantage of the present invention could be obtained.
The experiment made in Embodiment 1 was conducted by using propane (R290: C3H8) high in flammability.
As a result, the following formula was obtained.
2.5×(LFL)1.25×h0×A0.5≦M≦α×G−β×h0×A
where, α=0.22, and β=1.0
Where, when LFL of propane is taken as 0.038 kg/m3 (2.1 vol %), the lower limit is as follows,
On the other hand, the upper limit is as follows,
0.22×G−1×h0×A.
In the case of G=5 [kg/h],
M≦0.22×(5)−1×h0×A=0.044×h0×A is given, and
M≦0.0264A holds true for h0=0.6 [m], and
M≦0.0968A holds true for h0=2.2 [m].
Thus, it was found that the higher the flammability of gas (propane, for example), the smaller the upper limit of the refrigerant amount M needs to be. It was also found that the lower the flammability of gas, the greater the upper limit of the refrigerant amount M can be.
The results obtained in the Embodiments 1 to 3 are summarized in the following table.
Where, α is taken as a positive constant that the refrigerant mainly correlates to LFL and β is taken as a positive constant that the refrigerant mainly correlates to density. However, it is clear from Table 17 that the greater the LFL, the greater the a, and the greater the gas density, the smaller the β.
These approximate equations can be substantially represented by the following.
α=0.2 exp [6×LFL]
β=−0.5 Ln [gas density]+1
Thereby, a correlates to a lower flammability limit [kg/m3] and β correlates to gas density at about 25 degrees C.
However, these amounts do not sometimes strictly follow because they are influenced by liquefaction temperature or saturation vapor pressure.
The formulas can be represented as follows.
α=X exp [Y×LFL]
β=−ZLn [W×density]+1
where X, Y, Z, and W are positive constants determined by the type of refrigerant.
Description has been made in Embodiments 1 to 3 using R32, HFO-1234yf, and R290 as representative examples, but it is needless to say that the description also holds true for other HFC refrigerants or those mixed refrigerants.
It is also needless to say that the air-conditioning apparatus installed according to the above embodiments fills an effective refrigerant amount and does not lose safety.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/059707 | Apr 2014 | JP | national |
This application is a U.S. national stage application of PCT/JP2015/059952 filed on Mar. 30, 2015, which claims priority to International Patent Application No. PCT/JP2014/059707 filed on Apr. 2, 2014, the contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/059952 | 3/30/2015 | WO | 00 |
