JPH0827088B2 - Screw refrigeration equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a screw refrigerating apparatus, and more particularly to a screw refrigerating apparatus including a screw compressor, a condenser and an evaporator.

(Prior Art) In this type of screw refrigerating device, a refrigerant is injected in the middle of the compression process of a screw compressor to form an economizer cycle for controlling the discharge gas temperature. It is already known as disclosed in -285352. As shown in FIG. 5, this refrigeration system includes a liquid subcooler between a condenser (B) connected to the discharge side of a screw compressor (A) and an evaporator (C) connected to the suction side. The branch pipe (E), which is provided with (D) and branches from the downstream side of the condenser (B), is connected to the compressor (A) via the heat exchanger (F) of the liquid subcooler (D). ) Is connected to the intermediate suction port (G), and the branch pipe (E) has a temperature sensing part (H) for detecting the temperature of the discharge gas refrigerant from the compressor (A). Through a temperature-sensitive expansion valve (K) that controls the valve opening so that the vaporization of the refrigerant in the heat exchanger (F) is performed in a range that does not cause liquid compression in the compressor (A). And a part of the liquid refrigerant condensed in the condenser (B) from the branch pipe (E) in a liquid-gas mixed state. The intermediate suction port (G) of the compressor (A). Injected into,
The discharge gas temperature is controlled.

On the other hand, as a method for controlling the wetting control of the refrigerant injected into the intermediate suction port of the compressor as described above to control the discharge gas temperature, it is shown in FIG. 6 instead of the liquid subcooler (D) described above. There is also known one using the intermediate expansion tank (M).

In the one shown in FIG. 6, the intermediate expansion tank (M) is connected to the outlet side of the condenser (B) via a liquid pipe (N) having a high temperature expansion valve (L), and the tank ( M) is connected to the evaporator (C) via a low temperature expansion valve (P), and the standard liquid level H _o in the expansion tank (M) (calculated static when liquid gas is completely separated) Above the liquid level), an intermediate suction pipe (Q) is connected, the intermediate suction pipe (Q) is connected to the intermediate suction port (G) of the compressor (A), and the refrigerant gas of the expansion tank (M) is connected. Is controlled to get wet and is injected into the intermediate suction port (G) to control the discharge gas temperature.

(Problems to be Solved by the Invention) By the way, according to the economizer cycle using the intermediate expansion tank (M) as described above, it is structurally more advantageous than using the liquid subcooler (D), but The liquid level in the tank (M) rises to the standard liquid level due to a disturbance such as a capacity change of the compressor (A) or a cooling load change, and the standard liquid level rises to a connecting portion of the intermediate suction pipe (Q). When approaching, the liquid refrigerant is rapidly sucked into the intermediate suction pipe (Q), the dryness of the refrigerant injected into the intermediate suction port (G) is drastically reduced, and liquid compression may occur. In practice, it was impossible to control the discharge gas temperature using the intermediate expansion tank (M) described above.

The present invention has been made in view of the above problems, and its object is to reduce the change in the dryness of the refrigerant injected during the compression process of the screw compressor while using the intermediate expansion tank, and to discharge gas. It is the point that the controllability of temperature is improved and it can be put to practical use.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a screw refrigerating apparatus including a screw compressor (1), a condenser (2) and an evaporator (3), The outlet side of the condenser (2) is connected to an intermediate expansion tank (4) via a liquid pipe (5) having a high temperature expansion valve (6), and the tank (4) is connected to
An intermediate suction pipe (9) which is connected to the evaporator (3) through a liquid pipe (7) having a low temperature expansion valve (8) and which opens above the standard liquid surface in the tank (4) is provided. While connecting to the intermediate suction port of the compressor (1), the liquid pipe (5) on the inflow side was connected below the standard liquid level in the tank (4).

Further, in the above-mentioned structure, a bubble-mixing preventive body is provided below the intermediate expansion tank (4) to prevent stirring of the lower liquid-refrigerant and prevent bubbles from flowing into the evaporator (3). It is preferable that the liquid pipe (5) on the inflow side is connected to the upper side of the air bubble mixing prevention body, while the liquid pipe (7) on the outflow side is connected to the lower side of the air bubble mixing prevention body.

(Operation) A part of the liquid refrigerant flowing from the liquid pipe (5) to the intermediate expansion tank (4) is vaporized by the high temperature expansion valve (6) interposed in the liquid pipe (5) and flashes. While flowing into the liquid phase of the tank (4). Therefore, since the liquid phase in the tank (4) is agitated by the liquid refrigerant flowing in while flushing, the upper inside part of the tank (4) is in a foaming state, and the liquid ratio distribution is as shown in FIG. The state shown in FIG. 3 is changed from the conventional state shown in FIG. Therefore, even if the standard liquid level in the tank (4) changes, the change in the liquid ratio of the refrigerant flowing out from the intermediate suction pipe (9) is small, and the dryness of the intermediate suction gas refrigerant against the liquid level change. Of the refrigerant gas having a small change in dryness is injected into the compressor (1), the stability of discharge gas temperature control can be improved, and the intermediate expansion tank ( It is practically possible to control the discharge gas temperature using 4).

Furthermore, in the case where the bubble-mixing preventive body is provided in the lower part of the tank (4), the bubble-mixing preventive body is provided above the bubble-mixture preventing body while ensuring a good bubbling state of the liquid phase. Agitation of the defined lower liquid refrigerant is suppressed, and it is possible to reliably prevent the bubbles of the effluent liquid refrigerant from entering the evaporator (3) and prevent the performance of the evaporator (3) from deteriorating.

(Example) FIG. 1 schematically shows a piping system in a screw refrigerating apparatus, in which a condenser (2) is provided on the discharge side of the screw compressor (1) and a compressor (1) is provided. An evaporator (3) is connected to the suction side, and an intermediate expansion tank (4) is interposed between the condenser (2) and the evaporator (3). That is, a high temperature expansion valve (6) is provided in the liquid pipe (5) connecting the condenser (2) and the intermediate expansion tank (4).
And a low-temperature expansion valve (8) is installed in the liquid pipe (7) connecting the intermediate expansion tank (4) and the evaporator (3) to the condenser (2). A liquefied refrigerant is caused to flow into the evaporator (3) through the intermediate expansion tank (4), and the refrigerant gas evaporated in the evaporator (3) is circulated so as to return to the compressor (1). . Further, the intermediate expansion tank (4) and the intermediate suction port (1a) provided in the compressor (1) are connected via an intermediate suction pipe (9), and the intermediate expansion gas is discharged from the intermediate expansion tank (4). An economizer cycle is formed in which the refrigerant is injected into the intermediate suction port (1a) of the compressor (1) during the compression process through the intermediate suction pipe (9).

More specifically, as shown in FIG. 2, the liquid pipe (5) on the inflow side that connects the condenser (2) and the tank (4) is shown by a chain line in the tank (4). The standard liquid level (R) (opened below the standard liquid level (R) (calculated static liquid level when the refrigerant is completely separated into gas and liquid in the tank (4)) The intermediate suction pipe (9) is connected to a position above (R), and an outflow side liquid pipe (7) for flowing a liquid refrigerant to the evaporator (3) is provided at the lowermost portion of the tank (4). The liquid pipe (5) connected to the liquid pipe (7) at a position higher than the connecting portion
In the lower position of the, there is provided a bubble mixing prevention body formed of punching metal (10) having a large number of small holes.

Incidentally, (61) and (81) are temperature sensing means for controlling the high temperature expansion valve (6) and the low temperature expansion valve (8), respectively.

The screw refrigerating apparatus of the embodiment described above controls the discharge gas temperature by injecting the intermediate suction gas refrigerant from the intermediate suction pipe (9) during the compression process of the compressor (1). , Its action will be explained.

First, the refrigerant flowing from the condenser (2) through the liquid pipe (5) is partially vaporized by the high temperature expansion valve (6) and flows into the liquid phase of the tank (4) while flashing. And most of the liquid refrigerant flowing into the tank (4) is
The liquid flows through the liquid pipe (7) connected to the lower part of the tank (4), expands at the low temperature expansion valve (8), evaporates at the evaporator (3), and is sucked into the compressor (1). To be done.

On the other hand, a part of the refrigerant gas from the tank (4) flows into the intermediate suction pipe (9) and is injected from the intermediate suction port (1a) in the middle of the compression process of the compressor (1) to control the discharge gas temperature. Control it.

Therefore, the liquid pipe (5) is provided with a high-temperature expansion valve (6) whose opening is changed according to the discharge gas temperature, and the liquid pipe (5) is connected to the standard liquid surface (R). Since it is connected to the lower part, the refrigerant flowing from the liquid pipe (5) into the tank (4) while flushing causes the upper part of the tank (4) to be in a bubbling state, and the liquid ratio distribution is The conventional state shown in FIG. 4 is changed to the state shown in FIG.

That is, the conventional liquid ratio distribution shown in FIG.
As shown in FIG. 6, in the liquid ratio distribution of the conventional example in which the liquid pipe (N) is connected to a position higher than the standard liquid level (R), the liquid ratio changes with changes in the liquid level height. While it is in a small state, the liquid ratio distribution according to the present invention shown in FIG. 3 has a large change in the liquid ratio with respect to the change in liquid level height.

In FIGS. 3 and 4, the liquid ratio 1 indicates that the liquid ratio is 100% and the entire amount is the liquid refrigerant, and the liquid ratio 0 indicates that the liquid ratio is 0% and the entire amount is the gas refrigerant. . or,
H _o is the height of the standard liquid surface (R), H _in is the connecting position of the liquid pipe (5), H _ou is the connecting position of the intermediate suction pipe (9), and H
_p indicates the height of each of the connection positions of the punching metal (10).

When the standard liquid level (R) changes due to a disturbance such as a change in the capacity of the compressor (1) or a change in the cooling load, the graphs shown in FIGS. 3 and 4 move vertically in parallel. However, the gradient of the liquid ratio in the vicinity of the standard liquid surface (R) is steeper as shown in FIG. 3 in the present invention as compared with the conventional example of FIG. 4, so that the conventional example of FIG. Then, when the standard liquid level rises, a portion having a high liquid ratio is rapidly sucked into the intermediate suction pipe (9), and the dryness of the refrigerant gas injected into the compressor (1) fluctuates rapidly, so that liquid compression is performed. However, in the present invention, since the gradient of the liquid ratio is large as shown in FIG. 3,
The change in the liquid ratio of the refrigerant sucked into the intermediate suction pipe (9) is small, the change in the dryness of the intermediate suction gas injected during the compression process of the compressor (1) is small, and the temperature of the discharge gas is reduced. The stability of control is improved and it becomes practical.

Furthermore, since an air bubble mixing preventer such as the punching metal (10) is provided below the tank (4), it is possible to suppress agitation of the liquid refrigerant below the air bubble mixing preventer. It is possible to prevent bubbles from being mixed into the liquid refrigerant flowing therethrough to the evaporator (3), so that the capacity of the evaporator (3) is not deteriorated. The air bubble mixture preventer may be, for example, a wire mesh instead of the punching metal (10).

(Effects of the Invention) As described above, according to the present invention, in the screw refrigeration apparatus including the screw compressor (1), the condenser (2) and the evaporator (3), the condenser (2 ) Is connected to an intermediate expansion tank (4) through a liquid pipe (5) having a high temperature expansion valve (6), and the tank (4) is connected to
An intermediate suction pipe (9) which is connected to the evaporator (3) through a liquid pipe (7) having a low temperature expansion valve (8) and which opens above the standard liquid surface in the tank (4) is provided. While being connected to the intermediate suction port of the compressor (1), the liquid pipe (5) on the inflow side was connected below the standard liquid surface in the tank (4). Part of the liquid refrigerant is vaporized by the mounted high temperature expansion valve (6),
Flowing into the liquid phase of the tank (4) while flushing,
Therefore, the liquid phase in the tank (4) is agitated by the liquid gas mixed refrigerant flowing in while flushing,
The inside upper part of the tank (1) is foamed, and the liquid ratio distribution thereof is changed from the conventional state shown in FIG. 4 to the state shown in FIG. Therefore, even if the standard liquid level in the tank (4) changes, the change in the dryness of the refrigerant sucked into the intermediate suction pipe (9) is smaller than that in the conventional example, and the change in the dryness is small. Since the gas is sucked into the compressor (1), the wetness of the intermediate sucked gas refrigerant can be controlled, and the discharge gas temperature can be controlled stably, and the discharge gas temperature can be controlled by using the expansion tank (4). It is possible to put the control into practice.

Further, a bubble-mixing preventive body is provided in the lower part of the intermediate expansion tank (4) to suppress stirring of the lower liquid-cooling medium to prevent mixing of bubbles of the effluent liquid-cooling medium into the evaporator (3), and a liquid pipe on the inflow side. When (5) is connected above the bubble inclusion preventing body, while the liquid pipe (7) on the outflow side is connected below the bubble inclusion preventing body, the area above the bubble inclusion preventing body is good. While ensuring the bubbling state of the liquid phase, the lower liquid refrigerant that is defined as the upper side by the air bubble entrainment body is suppressed from being stirred, and it is possible to reliably prevent the inflow liquid refrigerant from entering the evaporator (3). The deterioration of the performance of the evaporator (3) can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic piping system diagram of a screw refrigerating apparatus of the present invention, FIG. 2 is an enlarged sectional explanatory view of an intermediate expansion tank, FIG. 3 is a liquid ratio distribution diagram of the intermediate expansion tank according to the present invention, and FIG. FIG. 5 and FIG. 6 are liquid ratio distribution diagrams of a conventional example, and are explanatory diagrams showing a conventional example. (1) …… Screw compressor (2) …… Condenser (3) …… Evaporator (4) …… Intermediate expansion tank (5) …… Liquid pipe (6) …… High temperature expansion valve (7) …… Liquid pipe (8) …… Low temperature expansion valve (9) …… Intermediate suction pipe

Claims (2)

[Claims] 1. A screw compressor (1) and a condenser (2)
A screw refrigerating apparatus including an evaporator (3) and an intermediate expansion tank (4) on the outlet side of the condenser (2) via a liquid pipe (5) provided with a high temperature expansion valve (6). And the tank (4) is connected to the evaporator (3) through a liquid pipe (7) having a low temperature expansion valve (8).
An intermediate suction pipe (9) opening above the standard liquid level in the tank (4) is connected to the intermediate suction port of the compressor (1), while the liquid pipe (5) on the inflow side is connected to the tank ( A screw refrigerating apparatus, which is connected below the standard liquid surface in 4). 2. An air bubble mixing preventing body is provided at a lower portion of the intermediate expansion tank (4) for suppressing agitation of the lower liquid refrigerant to prevent air bubble mixing of the effluent liquid refrigerant into the evaporator (3). 2. The screw refrigerating apparatus according to claim 1, wherein said liquid pipe (5) is connected above said bubble inclusion preventer, while said liquid pipe (7) on the outflow side is connected below said bubble inclusion preventer. .