JP2806090B2 - Operation control device for refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control device for a refrigeration system in which a circulating fluid in a chiller circuit is cooled by an evaporator, and more particularly to a measure for improving the control accuracy of the evaporator outlet liquid temperature.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Utility Model Laid-Open No. 49-4004
As disclosed in Japanese Patent Application Publication No. 7-107, there is provided a refrigeration apparatus comprising a refrigerant circuit in which a compressor, a condenser, a pressure reducing valve and an evaporator are sequentially connected, and the evaporator cools a cooling liquid in a chiller circuit. A hot gas bypass path is provided for bypass-connecting the discharge line of the refrigerant circuit and the liquid pipe between the pressure reducing valve and the evaporator, and a heat exchanger for exchanging heat with the refrigerant of the evaporator is provided in the hot gas bypass path. In this way, it is possible to easily adjust the amount of hot gas bypass, and therefore, even when a low-capacity compressor such as a fully-closed compressor is used, the capacity is controlled smoothly by a known technique. is there.

[0003]

[Problems to be solved by the invention] By the way, in recent years,
As the reach unit is used for industrial purposes, it is required to control the outlet water temperature with high accuracy. Here, especially for medium to large units,
Equipped with a compressor having a plurality of unload steps, it is possible to control the evaporator outlet water temperature, but with a small fully-closed compressor, the unload step cannot be increased, It was difficult to keep the outlet water temperature constant.

In such a case, as means for adjusting the coolant temperature at the evaporator outlet of the coolant without controlling the capacity of the compressor, for example, a heater for heating the coolant at the evaporator outlet is provided, and the coolant once cooled is provided. It is conceivable to control the evaporator outlet water temperature constant by adjusting the heating amount of the evaporator. But,
In this case, the cooling liquid is once excessively cooled, and furthermore, the heater power is used, so that the efficiency is very poor.

Therefore, as in the above-mentioned conventional publication,
Although it is conceivable to adjust the capacity of the evaporator by hot gas bypass instead of the capacity of the compressor, in the above publication, the overheating of the refrigerant bypassed by heat exchange with the refrigerant of the evaporator in the hot gas bypass passage is considered. Even if the refrigerant state such as the temperature can be properly maintained, there is a problem that it is difficult to control the water temperature at the evaporator outlet at a constant level. on the other hand,
It is conceivable to arrange an electric expansion valve in the bypass or a three-way valve at a branch point with the bypass to control the bypass amount of the refrigerant by PID, but the controller becomes expensive. In addition, when the load on the chiller circuit fluctuates suddenly or when the amount of water changes, it is necessary to change the set value of the PID. Therefore, there is a possibility that the temperature controllability may be disturbed or the water temperature may be unstable.

[0006] The present invention has been made in view of the above point, and an object of the present invention is to reduce the cost while taking measures to finely adjust the hot gas bypass amount using the evaporator outlet water temperature as an index. Another object of the present invention is to constantly control the water temperature at the evaporator outlet with high accuracy and high stability.

[0007]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
As shown in FIG. 1, the means adopted by the present invention is a refrigerant circuit (FIG. 1) that connects a fully-closed compressor (1), a condenser (2), a pressure reducing mechanism (3), and an evaporator (4) in order. It is assumed that the refrigerating apparatus is provided with 6) and the circulating liquid in the chiller circuit (10) is cooled by the evaporator (4).

A hot gas bypass path (7) for bypass-connecting the discharge line of the refrigerant circuit (6) and a liquid pipe between the pressure reducing mechanism (3) and the evaporator (4); And a flow control valve (8) for adjusting the refrigerant bypass amount of the hot gas bypass passage (7).

Further, as an operation control device of the refrigeration system,
An outlet temperature detecting means (Thw) for detecting a liquid temperature at the outlet of the evaporator (4) of the chiller circuit (10), and an output of the outlet temperature detecting means (Thw) is supplied to the liquid at the outlet of the evaporator (4). The temperature is compared with the set temperature, and the opening degree of the flow control valve (8) is increased by a certain opening degree every predetermined standby time when the liquid temperature at the outlet of the evaporator (4) is lower than the set temperature. On the other hand, when the outlet liquid temperature of the evaporator (4) is higher than the set temperature by a predetermined temperature or more, control is performed such that the opening degree is reduced by a certain degree.
, After increased or decreased controlling the opening of the flow control valve (8), the opening degree decrease of the evaporator within a short predetermined time than the waiting time (4) outlet of the liquid temperature flow control valve (8) Opening control means (20) for controlling the opening of the flow control valve (8) to return by half of the constant opening which has been increased or decreased in the previous control when the opening changes to the side or the opening increasing side. Things.

[0010]

According to the present invention, in the present invention, the evaporator (4)
When the liquid temperature at the outlet falls and becomes lower than the set temperature, the opening control means (20) controls the opening of the flow control valve (8) to increase by a constant opening, so that the discharge refrigerant is discharged. The amount of bypass to the hot gas bypass passage (7) increases, and as a result, the cooling capacity of the evaporator (4) decreases due to the same effect as the load down of the compressor (1). afterwards,
When the liquid temperature at the outlet of the evaporator (4) rises and the outlet water temperature becomes higher than the set temperature by a predetermined temperature or more, the opening of the flow rate control valve (8) is controlled to be reduced by a fixed opening. Control is performed so that the cooling capacity of the evaporator (4) increases, the liquid temperature decreases, and approaches the set temperature. By adjusting the refrigerant bypass amount to the hot gas bypass passage (7) in this way, even when the fixed capacity compressor (1) is used, the capacity of the evaporator (4) is adjusted and the evaporator (4) is adjusted. 4) The liquid temperature at the outlet is maintained near the set temperature.

In this case, it is not necessary to provide a pressure sensor in addition to the need for an inexpensive fully-closed compact compressor.
As in the case of ID control, it is possible to cope with a sudden change in the load on the chiller circuit (10) side without providing an expensive set value changing function, thereby reducing the cost and stabilizing the control. Will do.

In addition, when the liquid temperature changes in the reverse direction within a predetermined time shorter than the predetermined time after the opening degree of the flow control valve (8) is changed, the constant is changed by the previous control. Since the control is performed so as to return the opening by half of the opening, a sudden change in the liquid temperature caused by a sudden change in load or the like is suppressed, and a stable control state is maintained.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a refrigerant piping system of a liquid cooling device according to an embodiment of the present invention. The liquid cooling device includes a chilling unit (B) for cooling a machine tool and the like, and a circulating liquid of the chilling unit (B). And a refrigerating device (A) for cooling the water. The refrigerating apparatus (A) includes a fully-closed compressor (1), a condenser (2) for condensing and liquefying a refrigerant discharged from the compressor (1), and the condenser (2). A capillary tube (3) as a decompression mechanism for decompressing the refrigerant liquefied by the above, and an evaporator (4) for evaporating the refrigerant decompressed by the capillary tube (3) are connected by a refrigerant pipe (5). A refrigerant circuit (6) that is sequentially connected is provided. Further, a hot gas bypass path (7) for bypass-connecting the discharge line of the refrigerant circuit (6) and a liquid pipe between the capillary tube (3) and the evaporator (4) is provided. The hot gas bypass passage (7) is provided with a pulse type electric expansion valve (8) as a flow control valve for adjusting the flow rate. That is, the motor-operated expansion valve (8) is opened and closed by a pulse motor in accordance with a pulse signal.
The bypass amount of the discharged refrigerant to the hot gas bypass path (7) is increased or decreased.

Here, a chiller circuit (1) of the chilling unit (B) is provided in the use side medium flowing section of the evaporator (4).
0) is circulated through the cooling liquid,
In the refrigerant circuit (6), cold heat given by the condenser (2) is given to the coolant by heat exchange in the evaporator (4) to cool the coolant.

At the outlet of the evaporator (4) of the chiller circuit (10), a temperature sensor (Thw) as outlet water temperature detecting means for detecting the water temperature Two at the outlet of the cooling water evaporator (4) is provided. The signal from the temperature sensor (Thw) can be input to a controller (20) for controlling the operation of the refrigeration system (A). And the above controller (20)
Thus, the opening degree of the electric expansion valve (8) of the hot gas bypass passage (7) is controlled in accordance with the signal of the temperature sensor (Thw). It has a function as an opening control means according to the invention of the above.

Next, the contents of control of the controller (20) will be described with reference to FIGS. Here, FIG. 2 is a flowchart showing the control contents of the controller (20), and (a) and (b) of FIG. 3 (or FIG. 4) show changes in the outlet water temperature TWo, respectively (however, a broken line in the figure indicates 5 shows changes in the inlet water temperature Ti) and changes in the opening of the electric expansion valve (8). First, in step ST1, it is determined whether or not the coolant outlet water temperature Two detected by the temperature sensor (Thw) is equal to or higher than the set temperature Ts. If Two ≧ Ts, the process proceeds to step ST2, and the following process is performed. Compressor by procedure (1)
, Ie, the opening degree reduction control of the electric expansion valve (8).

First, in step ST2, it is determined whether or not a counter n for determining whether the outlet water temperature Two is equal to or higher than the set temperature Ts (n = 1) or lower (n = 0) is "1". 1
If n = 1, step n3
To reset the counter n to "1", and reset the time t1 of a first timer (not shown) for load-up, that is, for controlling the degree of opening of the electric expansion valve (8), and then go to step ST4. The time t2 of the second timer (not shown) for the load-down, that is, the control for increasing the opening, is the third time which is the predetermined time for the control for increasing the opening according to the first aspect of the present invention.
It is determined whether or not a set value ΔT3 (where ΔT3 <ΔT1) (ΔT1 is a first set value described later) is not reached.

If the result of the determination in step ST4 is not t2 <ΔT3, that is, if the predetermined time ΔT3 has passed, then in step ST5, the counted time t1 of the first timer is referred to as the invention of claim 1. After waiting until the first set time .DELTA.T1 which is the standby time for the opening degree reduction control becomes equal to or longer than the first set time .DELTA.T1, when the first set value .DELTA.T1 elapses, the timer time t1 of the first timer is reset in step ST6 and the step ST7 is executed. Then, the outlet water temperature Two is compared with a value (Ts + α) obtained by adding the constant temperature α to the set temperature Ts.
If ≧ Ts + α, the process proceeds to step ST8, where P = P−ΔP1 (ΔP1 is a constant opening during the opening reduction control according to the first aspect of the present invention) with respect to the opening P of the electric expansion valve (8). And the opening of the electric expansion valve (8) is set to a constant opening ΔP1
(For example, a value of about 100 pulses) (see times m3 and m4 in FIGS. 3A and 3B).

The result of the determination in step ST4 is t
If 2 <ΔT3, that is, if the predetermined time ΔT3 has not elapsed since the previous opening control of the electric expansion valve (8) was increased, the process proceeds to step ST9 and proceeds to step ST7.
In the same manner as above, it is determined whether Two ≧ Ts + α, and Two ≧ Ts +
The process proceeds to step ST5 until α is reached. When Two ≧ Ts + α, it is determined that there is a risk of overcontrol due to a sudden change in load, and the process proceeds to step ST10, where P = P− (ΔP2 / 2), that is, It is reduced by a half (and therefore a value of about 50 pulses) of the constant opening .DELTA.P2 (which is also a value of about 100 pulses in the present embodiment) on the side of increasing the opening (the time shown in FIGS. 4A and 4B). m5 and m6).

In the determination in step ST1, Two is determined.
If not ≧ Ts, the process proceeds to step ST11, where the counter n determines whether or not the water temperature Two is “0” indicating that the water temperature Two is equal to or lower than the set temperature TS. If n = 0, the load of the compressor (1) is determined. In order to perform the down, that is, the opening increase control,
The process proceeds to step ST12, and waits until the measured time t2 of the second timer becomes equal to or longer than the predetermined time ΔT2 during the opening degree increase control. Thereafter, in step ST14, P = P + .DELTA.P2 (.DELTA.P2 is a constant opening during the opening increasing control according to the first aspect of the present invention), and the opening of the electric expansion valve (8) is increased by the constant opening .DELTA.P2. (FIG. 3
(See times m1 and m2 in (a) and (b)).

If the result of the determination in step ST11 is NO, that is, n = 0, the process proceeds to step ST15, where the counter n is set to "0" and the time t2 of the second timer is reset. , First
The fourth set time count time t1 of the timer is a predetermined time opening increasing side referred to in the invention of claim 1 .DELTA.T4 (However, [Delta] T
4 <ΔT2), it is determined whether or not t1 <ΔT2.
If it is not T4, the process shifts to the control in step ST12. On the other hand, if t1 <ΔT4, it is determined that there is a risk of overcontrol, and in step ST17, P = P + (ΔP1 //
2) Assuming that the opening of the electric expansion valve (8) is the constant opening Δ
Control is performed to open only half of P1 (see times m7 and m8 in FIG. 4).

Therefore, in the above embodiment, for example, FIG.
As shown in (a) and (b), the outlet water temperature Two falls and drops below the temperature (Ts + α) higher than the set temperature Ts by a predetermined temperature α (for example, a temperature of about 2 ° C.). ,
Further becomes lower than the set temperature Ts, the in <br/> the opening control unit controller - by La (20), the electric expansion valve (8)
(See times m1 and m2 in FIG. 3), the amount of refrigerant discharged to the hot gas bypass passage (7) increases, and as a result, The cooling capacity of the evaporator (4) is reduced by the same effect as the load down of the compressor (1). Thereafter, when the outlet water temperature Two rises and the outlet water temperature Two becomes higher than the set temperature Ts by a predetermined temperature α or more, the opening of the electric expansion valve (8) is controlled to be reduced by the constant opening ΔP1 (FIG. As a result, the cooling capacity of the evaporator (4) is increased, the water temperature TWO is reduced, and the temperature is controlled so as to approach the set temperature Ts.

That is, by adjusting the bypass amount of the refrigerant to the hot gas bypass path (7) in this way, the evaporator (4) can be used while using a fully closed type, that is, a fixed capacity type compressor (1). , The outlet water temperature TWO can be maintained near the set temperature Ts.

In this case, in addition to a compressor that controls the capacity of the compressor (1) by, for example, one having multiple unloading steps, a fully-closed, inexpensive small-sized compressor is used, and a pressure sensor is arranged. Since there is no need, cost can be reduced. Also, compared to the case where the electric expansion valve or the three-way control valve is controlled by PID, it is possible to cope with a sudden change in the load on the chiller circuit (10) side without providing an expensive set value changing function, Therefore, the control can be stabilized while reducing the cost.

In particular, after the opening degree of the electric expansion valve (8) is increased or decreased, the outlet water temperature Two changes in the opposite direction before a predetermined time (ΔT3 or ΔT4) shorter than a certain time (ΔT1 or ΔT2) elapses. In this case, a sudden change in the outlet water temperature Two caused by a sudden change in load or the like is particularly suppressed by changing the fixed opening (.DELTA.T3 or .DELTA.T4) in a direction opposite to the previous control by half. , A stable control state is maintained. Therefore, a remarkable effect can be exhibited.

In the above embodiment, the values of the constant openings ΔT1 and ΔT2 on the opening increasing side and the opening decreasing side are all 100.
Although the value is set to be approximately equal to the pulse, it is needless to say that both values need not be equal.

[0027]

As described above, according to the present invention,
As an operation control device of a refrigerating apparatus in which a circulating liquid in a chiller circuit is cooled by an evaporator in a refrigerant circuit, a discharge gas is connected to a liquid pipe between a decompression mechanism and an evaporator by a hot gas bypass path. A flow control valve in the bypass passage is interposed, and the liquid temperature at the outlet of the evaporator is compared with the set temperature. When the outlet liquid temperature is lower than the set temperature for every predetermined standby time, the opening of the flow control valve is set. The evaporator capacity is reduced by increasing the evaporator capacity by a fixed opening, and when the outlet liquid temperature is higher than the set temperature by a predetermined temperature or more, the opening of the flow control valve is reduced by a certain opening to increase the evaporator capacity. Therefore, an inexpensive fully-closed compressor can be used, and the liquid temperature at the evaporator outlet is controlled to be constant without increasing costs such as PID control and causing control instability due to load fluctuations. Can, so It can be achieved and stability of the reduction and control of costs. Moreover, after increasing or decreasing the opening of the flow control valve by a fixed opening, the liquid temperature at the evaporator outlet changes to the opening decreasing side or the opening increasing side within a predetermined time shorter than the predetermined standby time. sometimes because then returned only half of the predetermined opening degree increased or decreased in the last control, remarkable that that-out <br/> in is possible to suppress the liquid rapid change in temperature due to changes such as a sudden load The effect can be exhibited.

[Brief description of the drawings]

FIG. 1 is a refrigerant piping system diagram of a refrigeration apparatus according to an embodiment.

FIG. 2 is a flowchart showing control contents of a controller.

FIG. 3 is a diagram showing changes in the water temperature at the evaporator outlet and the degree of opening of the electric expansion valve under normal conditions.

FIG. 4 is a diagram showing changes in the water temperature at the evaporator outlet and the degree of opening of the electric expansion valve when the conditions change rapidly.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Compressor 2 Condenser 3 Capillary tube (decompression mechanism) 4 Evaporator 6 Refrigerant circuit 7 Hot gas bypass 8 Electric expansion valve (flow control valve) 10 Chiller circuit 20 Controller (opening degree control means) A Refrigeration Device B Chilling unit

Claims (1)

(57) [Claims] 1. A refrigerant circuit (6) comprising a fully-closed compressor (1), a condenser (2), a pressure reducing mechanism (3), and an evaporator (4) sequentially connected. ) And the chiller circuit (1)
0) In the refrigeration apparatus for cooling the circulating liquid, the hot gas bypass path (bypass connection) between the discharge line of the refrigerant circuit (6) and the liquid pipe between the pressure reducing mechanism (3) and the evaporator (4). 7) and a flow control valve (8) interposed in the hot gas bypass passage (7) for adjusting a refrigerant bypass amount of the hot gas bypass passage (7). An outlet temperature detecting means (Thw) for detecting the liquid temperature at the outlet of the evaporator (4); receiving the output of the outlet temperature detecting means (Thw), comparing the liquid temperature at the outlet of the evaporator (4) with the set temperature. The opening degree of the flow rate control valve (8) is increased by a constant opening degree at every predetermined standby time when the liquid temperature at the outlet of the evaporator (4) is lower than the set temperature, while the opening degree of the evaporator (4) is increased. The opening is constant when the liquid temperature of the Only controls to reduce, after increased or decreased controlling the opening of the flow control valve (8), an evaporator within a short predetermined time than the waiting time (4) outlet of the liquid temperature flow control valve ( When the opening is changed to the opening decreasing side or the opening increasing side in 8), the opening control means (2) for controlling the opening of the flow control valve (8) to return by half of the constant opening increased or decreased in the previous control.
0). An operation control device for a refrigeration system, comprising: