JPH07117269B2 - Defrosting operation control device for air conditioner - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defrosting operation control device for an air conditioner, and more particularly, to an improvement for appropriately starting a defrosting operation.

(Prior Art) Conventionally, as a defrosting operation control device of this type, Japanese Patent Publication No.
As disclosed in Japanese Laid-Open Patent Publication No. 54332/1989, a conditional expression for starting the defrosting operation is uniquely determined based on both the temperature of the outdoor heat exchanger and the outdoor temperature, and the outdoor condition that satisfies the conditional expression is determined. It is known that when the temperature of the heat exchanger and the outdoor temperature are the same, it is determined that the outdoor heat exchanger is frosting and the defrosting operation is started.

(Problems to be Solved by the Invention) However, when the capacity of a compressor is controlled by an inverter or the like as in recent years, the conditions for starting the defrosting operation differ depending on the capacity state of the compressor. If the conditional expression is uniquely set as in the above-mentioned conventional case, there is a drawback that the defrosting operation is started early in a state where the amount of frost is small, or the start of the defrosting operation is too late.

The present invention has been made in view of the above point, and an object thereof is to detect the optimum defrosting timing and always start the defrosting operation at an appropriate time.

(Means for Solving the Problem) In order to achieve the above object, in the present invention, the heat exchange performance of the outdoor heat exchanger during the heating operation is grasped, and thereby the heat exchange performance of the outdoor heat exchanger due to frost formation. It is necessary to accurately detect the decrease in

That is, as a concrete solution means of the present invention, as shown in FIG. 1, the compressor (1), the indoor heat exchanger (2), the expansion valve (3), and the outdoor heat exchanger (4) are sequentially arranged. Defrosting means (12) for defrosting the frost formed on the outdoor heat exchanger (4) on the premise of an air conditioner that has a refrigerant circulation system connected to a closed circuit and is capable of heating operation; Outdoor heat exchanger (4)
Evaporation capacity calculating means (20) for calculating the evaporation capacity of the outdoor heat exchanger (4) calculated by the evaporation capacity calculating means (20), the temperature of the outdoor heat exchanger (4) and the outside air Index calculation means (21) for calculating an index related to the heat exchange performance of the outdoor heat exchanger (4) based on the temperature, and defrosting operation based on the index related to the heat exchange performance calculated by the index calculation means (21) The defrosting means (12) for determining the start time of
And a control means (22) for operating the.

In that case, the evaporation capacity calculation means (20) is particularly configured to calculate the evaporation capacity based on the condensation capacity of the indoor heat exchanger (2) and the input of the compressor (1). Further, the condensation capacity of the indoor heat exchanger (2) is calculated by the temperature difference between the intake temperature and the outlet temperature of air in the indoor heat exchanger (2) and the air passage flow rate of the indoor heat exchanger (2). Or the enthalpy difference of the refrigerant between the refrigerant inlet and outlet of the indoor heat exchanger (2) and the circulating flow rate of the refrigerant.

Furthermore, the evaporation capacity calculation means (20) directly determines the evaporation capacity based on the enthalpy difference between the refrigerant on the suction side of the compressor (1) and the refrigerant on the outlet of the indoor heat exchanger (2), and the circulation flow rate of the refrigerant. Consist of what is calculated.

(Operation) With the above configuration, in the present invention, the evaporation capacity of the outdoor heat exchanger (4) acting as an evaporator is calculated during the heating operation, and this evaporation capacity, the temperature of the outdoor heat exchanger (4), and An index relating to the heat exchange capacity of the outdoor heat exchanger (4) is calculated based on the outdoor temperature.

Then, frost is formed on the outdoor heat exchanger (4), whereby the air flow cross-sectional area begins to be blocked, and the amount of air blown from the outdoor blower fan (4a) and passing through the outdoor heat exchanger (4) is increased. When the heat exchange capacity of the outdoor heat exchanger (4) begins to decrease and the heat exchange capacity of the outdoor heat exchanger (4) begins to decrease, the index relating to the heat exchange capacity also changes. Therefore, the defrosting operation of the outdoor heat exchanger (4) is started based on this index. The time can be accurately judged.

Here, since the index relating to the heat exchange capacity of the outdoor heat exchanger (4) is calculated and the change in the heat exchange capacity is directly grasped, even if the capacity of the compressor (1) is controlled, the compression Regardless of the capacity state of the machine (1), frost formation on the outdoor heat exchanger (4) can be accurately detected, and the defrosting operation start timing can be set to an appropriate timing.

Moreover, in that case, the evaporation capacity of the outdoor heat exchanger is indirectly calculated based on, for example, the condensation capacity of the indoor heat exchanger and the electric input of the compressor, or the enthalpy difference of the refrigerant in the outdoor heat exchanger is calculated. Alternatively, if it is directly performed based on the difference in air temperature before and after passage of the passing air, the evaporation capacity can be calculated accurately, so that the start time of the defrosting operation can be made more appropriate.

(Effect of the invention) As described above, according to the defrosting operation control device for an air conditioner of the present invention, the heat exchange capacity of the outdoor heat exchanger during the heating operation is directly grasped by calculating its index,
Regardless of the capacity state of the compressor, it is possible to accurately determine the frost formation on the outdoor heat exchanger and to appropriately set the start time of the defrosting operation.

In addition, the evaporation capacity of the outdoor heat exchanger is calculated directly based on the condensing capacity of the indoor heat exchanger, the electric input of the compressor, the enthalpy difference of the refrigerant in the outdoor heat exchanger, and the air temperature difference before and after passing the passing air. Or indirectly, the defrosting operation can be started at a more appropriate timing.

(Example) Hereinafter, the Example of this invention is described based on drawing.

In FIG. 2, (1) is a compressor, (2) is an indoor heat exchanger having an indoor blower fan (2a), (3) is an electric expansion valve, and (4) is an outdoor blower having an outdoor blower fan (4a). The heat exchanger (5) is a four-way switching valve, and the above devices are connected in a closed circuit by refrigerant pipes (6) to form a refrigerant circulation system (8). When the four-way switching valve (5) is switched to the solid line position, the high temperature refrigerant discharged from the compressor (1) is flown into the indoor heat exchanger (2) to heat the room as indicated by the solid line arrow. The liquefied low-temperature refrigerant is repeatedly flown into the outdoor heat exchanger (4) to absorb heat from the outside air and returned to the compressor (1) as a high-temperature refrigerant again. In contrast,
At the time of switching the four-way switching valve (5) to the broken line position, the high-temperature refrigerant discharged from the compressor (1) flows into the outdoor heat exchanger (4) to radiate heat to the outside air, as indicated by the broken line arrow. The liquefied low-temperature refrigerant is flown into the indoor heat exchanger (2) to cool the room and return it to the compressor (1) as high-temperature refrigerant again.

A refrigerant pipe (9) for defrosting is connected to the refrigerant pipe (6) between the discharge side of the compressor (1) and the four-way switching valve (5). The other end is connected to a refrigerant pipe (6) between the electric expansion valve (3) and the outdoor heat exchanger (4), and the pipe (9) is provided in the middle of the defrosting refrigerant pipe (9). An electromagnetic valve (10) for defrosting which opens and closes 9) is provided. The solenoid valve (10) is controlled to be opened when it is determined that the outdoor heat exchanger (4) is frosted during the heating operation in which the four-way switching valve (5) is in the solid line position.

Therefore, when the electromagnetic valve (10) for defrosting is opened, a part of the hot gas discharged from the compressor (1) is passed through the refrigerant pipe (9) for defrosting in the outdoor heat exchanger (4). By supplying the refrigerant to the refrigerant introduction side of the refrigerant circulation system (8), the defrosting means (12) is configured to perform the defrosting in a normal cycle.

Further, (15) is a controller having a CPU or the like inside, and the controller (15) allows an inverter (16)
To control the capacity of the compressor (1) according to the room temperature.

The controller (15) includes the dry-bulb temperature DBg and the wet-bulb temperature WBg of the outdoor air during the heating operation, the temperature (evaporation temperature) Te of the outdoor heat exchanger (4), and the air blown from the indoor heat exchanger (2). The signals of the temperature To, the intake air temperature Ti, the rotation speed of the indoor blower fan (2a), the input current I of the compressor (1) and the applied voltage V are input.

Next, the control of the defrosting operation of the outdoor heat exchanger (4) by the controller (15) will be described based on the control flow shown in FIG.

After the start, in step S ₁ , the condensing capacity Qc of the indoor heat exchanger (2) acting as a condenser during heating operation is calculated.
This calculation is based on the blowout temperature To and suction temperature Ti of indoor air. The following equation Qc = Gi · Cp · (To−Ti) Gi; Weight flow rate of air passing through the indoor heat exchanger (2) Cp; Air constant pressure specific heat Calculate based on.

Further, in step S ₂ , the electric input W of the compressor (1) is changed to the formula W
= Calculated based on IV.

Thereafter, the evaporation capacity Qe of the outdoor heat exchanger (4) in step S ₃
As can be seen from the Mollier diagram of FIG. 4, it is calculated by the equation Qe = Qc−W based on the condensation capacity Qc of the indoor heat exchanger (2) and the input of the compressor (1).

Subsequently, in order to calculate the index K of the heat exchange capacity of the outdoor heat exchanger (4), first calculates the enthalpy difference of the air in the outdoor heat exchanger (4) at Step S _4. In this calculation, the evaporation capacity of the outdoor heat exchanger (4) is obtained by wet heat exchange, and the enthalpy difference of the air serves as a driving force to perform heat exchange. Therefore, the dry-bulb temperature DBg and the wet-bulb temperature of the outdoor air are calculated. The enthalpy Ha of the air is obtained from WBg, and the saturated air enthalpy He corresponding to that temperature is obtained from the temperature Te of the outdoor heat exchanger (4).

Here, the evaporation capacity Qe of the outdoor heat exchanger (4) is calculated from the above enthalpies Ha and He by the following equation Qe = Go · ε · (Ha−He) (1) Go; Weight flow rate of outdoor air ε; It can be calculated based on the enthalpy efficiency, and if Go · ε in the above equation (1) is set as the index K related to the heat exchange capacity of the outdoor heat exchanger (4), the above equation (1) is transformed to K = Qe / (Ha-He) (2) is obtained. Therefore, subsequently, in step S ₅ , the index K (= Go · ε) relating to the heat exchange capacity of the outdoor heat exchanger (4) is calculated based on the equation (2).

Then, in step S ₆ , the index K calculated above is compared with the set value K _D for starting the defrosting operation. Here, the set value K _D is changed depending on the rotation speed of the outdoor blower fan (4a).
When K> K _D non-frosting, the process returns to step S ₁ and repeats the above calculation operation. On the other hand, when it is judged that K ≦ K _D frosting occurs, in step S ₇ , the defrosting of FIG. 2 is performed. The solenoid valve (10) for use is controlled to open, and the defrosting operation of the outdoor heat exchanger (4) is started.

Therefore, in the control flow of FIG. 3 above, step S ₁
Evaporation capacity calculation means for calculating the evaporation capacity of the outdoor heat exchanger (4) based on the condensation capacity Qe of the indoor heat exchanger (2) and the input of the compressor (1) by S ₃ to S _3. 20). Further, in steps S ₄ and S ₅ , the evaporation capacity Qe of the outdoor heat exchanger (4) calculated by the evaporation capacity calculation means (20) and the dry-bulb temperature DBg of the outside air are calculated based on the calculation formula (2). And the enthalpy Ha of the air obtained from the wet-bulb temperature WBg,
And an index K (= Go · ε) relating to the heat exchange performance of the outdoor heat exchanger (4) based on the saturated air enthalpy He corresponding to the temperature Te of the outdoor heat exchanger (4) The index calculation means (21). Further, in steps S ₆ and S ₇ of the control flow, it is determined that the defrosting operation start time is satisfied when K ≦ K _D , based on the index K relating to the heat exchange performance calculated by the index calculation means (21). The defrosting solenoid valve (10) is controlled to be opened to operate the defrosting means (12), thereby forming a control means (22).

Therefore, in the above-described embodiment, the evaporation capacity Qe of the outdoor heat exchanger (4) is calculated based on the condensation capacity Qc of the indoor heat exchanger (2) and the electric input W of the compressor (1) during the heating operation. After that, the index K (= Go · ε) regarding the heat exchange capacity of the outdoor heat exchanger (4) is calculated based on the above equation (2), which is repeated.

Now, when frost forms on the outdoor heat exchanger (4) and progresses, the frost blocks the passage cross section of the air blown from the outdoor blower fan (4a) in the outdoor heat exchanger (4). The air passing flow rate Go decreases, and the heat exchange capacity of the outdoor heat exchanger (4) decreases. Further, as the heat exchange capacity decreases, the index K (= Go · ε) relating to the heat exchange capacity also decreases as shown in FIG. 5 as the air flow rate Go decreases. As a result, when the index K becomes equal to or less than the set value K _D corresponding to frost formation (K ≦ K _D ), the defrosting solenoid valve (10) is controlled to open, so that the compressor (1 A part of the hot gas discharged from (4) flows through the defrosting refrigerant pipe (9) to the outdoor heat exchanger (4), and defrosting of the outdoor heat exchanger (4) is started.

Here, the above-mentioned index K corresponds well to the change in the heat exchange capacity of the outdoor heat exchanger (4), and the outdoor heat exchanger (4)
Since the heat exchange capacity of the compressor (1) is accurately grasped, even if the capacity of the compressor (1) is controlled by the inverter (16) according to the change of room temperature, the outdoor heat exchanger (4) is irrespective of its capacity state. The defrosting operation start timing can be set appropriately.

FIG. 6 shows a modification of the calculation of the condensing capacity Qc of the indoor heat exchanger (2). In the above embodiment, the temperature difference between the air outlet temperature To and the suction temperature Ti of the indoor heat exchanger (2) depends on the temperature difference. Instead of the above calculation, it is calculated based on the enthalpy difference of the refrigerant between the refrigerant inlet and outlet of the indoor heat exchanger (2).

That is, the refrigerant temperature Tc at the refrigerant inlet side of the indoor heat exchanger (2)
The ond-in and the condensation temperature Tc, the evaporation temperature Te, the refrigerant temperature Tsuc on the suction side of the compressor (1), the rotation speed n of the compressor (1) are detected, and the refrigerant outlet side of the indoor heat exchanger (2) is detected. Refrigerant temperature
Tcond-out = Tcond-out = Tcon
After calculated by d-in + SC, based on these, the enthalpy Hc of each refrigerant at the refrigerant inlet and outlet of the indoor heat exchanger (2)
Ond-in and Hcond-out are calculated based on the following formula Hcond-in = f (Tc, Tcond-in) Hcond-out = f (Tc, Tcond-out) as can be seen from FIG.

Then, the circulating weight flow rate G of the refrigerant is calculated by the following equation G = (1 / ρ) · F = (1 / ρ) · Vrev · n. Where ρ is the density of the refrigerant on the suction side [kg
/ m ³ ], and ρ = f (Te, Tsuc). Further, F is the circulation volume flow of the refrigerant [m ³ / h], and Vrev is 1 of the compressor (1).
Excluded volume per revolution.

And each enthalpy Hcond-in, Hc of the refrigerant inlet and outlet
Condensation capacity based on the on-out and the circulating weight flow rate G of the refrigerant
Qc is calculated by the following formula Qc = G · (Hcond-in-Hcond-out).

Next, as a modified example of the evaporation capacity calculation means (20), an example in which the evaporation capacity Qe of the outdoor heat exchanger (4) is directly calculated will be described.

Since the enthalpy difference of the refrigerant between the refrigerant inlet and outlet of the outdoor heat exchanger (4) is Hsuc-Hcond-out as can be seen from FIG. 6, the circulation weight flow rate of the refrigerant is G, and the evaporation capacity Qe is Qe = It is calculated by G · (Hsuc-Hcond-out).

In that case, the refrigerant temperature Tsuc on the suction side of the compressor (1) may be calculated by Tc + SH based on the evaporation temperature Tc and the superheat degree SH without detecting the refrigerant temperature Tsuc.

In the above embodiment, K (= Go · ε) is used as an index relating to the heat exchange capacity of the outdoor heat exchanger (4) during the heating operation.
However, instead of this, the weight flow rate Go of the outdoor air may be used.

That is, from the outdoor blower fan (4a) to the outdoor heat exchanger (4)
The enthalpy of the outdoor air after passing through the
t, the enthalpy before passing is Ha-in, and these are the temperature Te of the outdoor heat exchanger (4), and the dry-bulb temperature D before passing the outdoor air.
The evaporation capacity Qe of the outdoor heat exchanger (4) can be calculated based on Bin and wet bulb temperature WBin, and the dry bulb temperature DBout after passing and the wet bulb temperature WBout. -In). Therefore, the weight flow rate Go of the outdoor air is calculated by the above formula as an index of the heat exchange capacity of the outdoor heat exchanger (4), and if the decrease in the flow rate Go is directly observed, the outdoor heat exchanger (4) due to frost formation It is possible to directly detect the decrease in heat exchange capacity of.

In addition, other indexes can be used as indexes for heat exchange capacity. For example, the enthalpy of the outdoor air flowing through the outdoor heat exchanger (4) at the heat exchange section is H _∽ , the saturated air enthalpy corresponding to the temperature of the outdoor heat exchanger (4) is He, and the outdoor heat exchanger ( The evaporation capacity Qe of 4) is expressed by the equation Qe = h · A · (H _∽ −He). Where A is the heat transfer area of the outdoor heat exchanger (4), h is the heat transfer coefficient based on the enthalpy difference, and h = f
Calculated as (Te, DBin, WBin).

Therefore, the enthalpy difference ΔH (= H _∽ −He) is calculated by the above formula, the enthalpy difference ΔH due to frost is used as an index relating to the heat exchange capacity, and the increase is observed to determine the outdoor heat exchanger (4).
If a decrease in heat exchange capacity is detected and the defrosting operation is started when it exceeds the set value ΔHd corresponding to the start of the defrosting operation as shown in Fig. 7, the defrosting operation will be started at an appropriate start time. It can be carried out.

Furthermore, the evaporation capacity Qe is changed to the enthalpy difference [Delta] H, wherein Qe = h '· A · ( T ∽ -Te) based on the temperature difference _{ΔT (= T ∽ -Te) (} h is the temperature difference criteria since the calculated heat a transfer rate), the temperature difference ΔT (= T _∽ -Te) if index for heat exchange capability, it is possible to perform the defrosting operation in the appropriate start timing in the same manner as described above .

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention. 2 to 7 show an embodiment of the present invention, FIG. 2 is an overall configuration diagram, FIG. 3 is a flow chart diagram showing control of defrosting operation, and FIG. 4 is an index K relating to heat exchange capacity. FIG. 5 is an explanatory view showing a state of change with respect to the progress of frost, FIG. 5 is an explanatory view showing a Mollier diagram for calculating the evaporation capacity of the outdoor heat exchanger, and FIG. 6 is a drawing for calculating the condensation capacity of the indoor heat exchanger. FIG. 7 is an explanatory diagram showing a Mollier diagram, and FIG. 7 is an explanatory diagram showing how the enthalpy difference ΔH is used as an index relating to the heat exchange capacity, and the change in the enthalpy difference with respect to the progress of frost formation. (1) ... Compressor, (2) ... Indoor heat exchanger, (3) ...
... expansion valve, (4) ... outdoor heat exchanger, (8) ... refrigerant circulation system, (20) ... evaporation capacity calculation means, (21) ... index calculation means, (22) ... control means.

Claims (5)

[Claims] 1. A refrigerant circulation system (8) in which a compressor (1), an indoor heat exchanger (2), an expansion valve (3) and an outdoor heat exchanger (4) are sequentially connected in a closed circuit, In an air conditioner capable of heating operation, defrosting means (12) for defrosting the frost formed on the outdoor heat exchanger (4) and evaporation for calculating the evaporation capacity of the outdoor heat exchanger (4). Ability calculation means (20)
Of the outdoor heat exchanger (4) based on the evaporation capacity of the outdoor heat exchanger (4) calculated by the evaporation capacity calculation means (20) and the temperature of the outdoor heat exchanger (4) and the outside air temperature. Index calculation means (21) for calculating an index related to heat exchange performance, and a start time of defrosting operation is determined based on the index related to heat exchange performance calculated by the index calculation means (21). And a control means (22) for operating the air conditioner. 2. The evaporation capacity calculation means (20) calculates the evaporation capacity based on the condensation capacity of the indoor heat exchanger (2) and the input of the compressor (1). A defrosting operation control device for the air conditioner described. 3. The evaporation capacity calculation means (20) calculates the condensation capacity of the indoor heat exchanger (2), the temperature difference between the air intake temperature and the outlet temperature of the indoor heat exchanger (2), and the indoor heat exchange. The calculation is based on the flow rate of air passing through the device (2).
A defrosting operation control device for the air conditioner described. 4. The evaporation capacity calculation means (20) determines the condensation capacity of the indoor heat exchanger (2) based on the enthalpy difference of the refrigerant between the refrigerant inlet and outlet of the indoor heat exchanger (2) and the circulation flow rate of the refrigerant. The defrosting operation control device for an air conditioner according to claim 2, wherein 5. The evaporation capacity calculation means (20) is a compressor (1).
The defrosting of the air conditioner according to claim 1, wherein the evaporation capacity is directly calculated based on the enthalpy difference between the refrigerant on the suction side and the refrigerant at the outlet of the indoor heat exchanger (2) and the circulation flow rate of the refrigerant. Operation control device.