JPS5937418B2 - Refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigeration system O in which a refrigerant circuit is constructed by sequentially connecting a compressor, a condenser, a pressure reducing device, an evaporator, etc. in an annular manner.
In particular, it relates to something that suppresses a rise in pressure on the discharge side of a compressor.

Conventionally, in this type of refrigeration equipment, during operation, the temperature of the intake air for heat exchange increases in the condenser, and the rotation speed of the heat exchange fan decreases, resulting in so-called overload operation, which causes the condenser to overload. The heat exchange capacity decreases, the condensation pressure of the refrigerant increases, and the temperature may rise accordingly.

When the condensing pressure and temperature rise, the pressure and temperature at the discharge port of the compressor, which is directly connected to the condenser inlet Q, rises, which not only increases the load on each part of the compressor, but also overheats the lubricating oil in the compressor, causing it to become viscous. If the lubricating performance deteriorates due to changes or deterioration, problems such as burnout of the compressor body may occur.

For this reason, in the past, the discharge port pressure of the compressor was lower than the set value (
Although this inconvenience has been prevented by providing a high-pressure cut-off mechanism that stops the operation of the compressor when the pressure increases, the range of possible operation has been significantly restricted by such preventive measures.

The present invention solves the above-mentioned difficulties by providing a refrigeration system that can continue operating while suppressing the increase in pressure on the outlet side of the compressor to within a certain limit.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a compressor, 2 is a condenser 53, a pressure reducing device, and 4 is an evaporator, which are sequentially connected in a ring to form a refrigerant circuit.

Refrigeration sign of the above basic circuit configuration) I/l To explain in detail, the refrigerant compressed almost adiabatically in the compressor 1 is condensed by exchanging heat with the air on the high heat source side in the condenser 2, and becomes liquid refrigerant. Further, the steam is compressed and expanded almost isenthalpically in the decompression device 3 to become wet steam, and then heat exchanged with the air on the low heat source side in the evaporator 4 to become dry steam, which is sucked into the compressor 1c again.

That is, the structure is such that heat is absorbed from the low heat source side, and the heat amount, which is the sum of the work of the compressor, is radiated from the high heat source.

Next, a detailed explanation of the present invention will be given with respect to the basic refrigeration cycle circuit.

5 is a bypass passage connecting the outlet side and the inlet side of the compressor 1, and 6 is a flow rate control means, which is a flow rate control valve such as a solenoid valve installed in the bypass passage 5Q.

7 is a detection means for detecting that the pressure on the outlet side of the compressor 1 has exceeded a predetermined value, and is a temperature sensor disposed on the pipe wall of the condenser 2.

Reference numeral 8 denotes a calculation section such as a microcomputer which inputs the detection signal from the temperature sensor 7 and transmits a response signal to the flow rate control valve 6G.

9 is a check valve as a blocking means installed in the refrigerant passage Q connecting between the outlet of the evaporator 4 and the inlet of the compressor 1;
This is arranged to prevent backflow from the inlet side of the compressor 1 to the outlet side of the evaporator 4.

The operation of this configuration will be explained based on FIG. 2G.

During operation of the refrigeration system, the refrigerant discharge pressure of the compressor 1 is a set value P1 below PH, which is the limit value of condensing pressure that causes overload operation.
(When this reaches this point, the temperature detector 7 detects the condensing temperature that increases correspondingly to the discharge pressure P1Q, and the detection signal is sent to the calculation unit 8.
Communicate to.

When the arithmetic unit 8 receives the signal, it sets m1Jtf to open the control valve 6 which is in a closed state at a condensing pressure lower than the pressure P1.
+

When the control valve 6 is opened, the compressor 1 is connected to the bypass passage 5.
Refrigerant flows from the high pressure discharge side to the low pressure suction side.

At this time, the refrigerant passage connecting the discharge port of the compressor 1 and the outlet of the evaporator 2 (through the action of the check valve 9 installed therein), the refrigerant flowing through the bypass passage 5 is prevented from flowing back toward the evaporator. Instead, it flows into the compressor 1.

Since the passage resistance of the flow rate control valve 6 and the bypass passage 5 is negligibly small compared to the passage resistance of the basic circuit, the refrigerant compressed by the compressor 1 only needs to circulate through the bypass passage 5 and is then transferred to the condenser. The compressor 1 does not flow in the direction 2, and the compressor 1 is operating from the so-called 9.

By the way, if the work of the compressor is adiabatic compression, the compression work is expressed by the following formula.

”” (Vt Pt V2p2) °”(
1)-1 where ′, specific heat ratio, pl: pressure at the start of adiabatic compression, p
2: Pressure at the end of adiabatic compression, vl: Specific volume at the start of adiabatic compression, v2: Specific volume at the end of adiabatic compression As described above, the bypass passage 5 at the start of the Q-flow control valve 6
If we ignore the passing resistance of
With this substitution, the compression work becomes zero.

However, since this is not a strict adiabatic compression, the compressor 1
Heat loss from the internal cylinder or friction loss between the piston and cylinder is used as work.

In this way, when the flow control valve 6 is opened, the compressor 1 to the condenser 2
While the refrigerant supply to the condenser 2 is stopped, the refrigerant is sent from the condenser 2 to the evaporator 4 via the pressure reducing device 3.
The amount of refrigerant in the tank decreases, and the condensing pressure drops.

Then, when the pressure drops to the second set value p2 shown in the figure and a detection signal from the temperature sensor 7 corresponding to the pressure p2' is input to the calculation unit 8, the calculation unit 8 controls the control valve 6. A closing response signal is generated and the bypass passage 5 is closed.

Therefore, no refrigerant flows into the bypass passage 5, and the compressor 1
Since the condensate flows to the condenser 2 and normal operation is restarted, the condensation pressure increases again.

Then, when the condensing pressure reaches p, the control valve is closed again, and since the opening and closing of the control valve is repeated at approximately equal intervals, the condensing pressure-hour curve becomes a sawtooth broken line as shown in Figure 2. .

In this way, the increase in condensing pressure, that is, the pressure on the outlet side of the compressor, is suppressed to a set value that does not cause overload operation, and operation can be continued. Since it can be continued, the operating range of use is further expanded.

Next, another embodiment of the present invention is shown in FIG. 3 and will be described.

In addition to the configuration of the embodiment shown in FIG. 1, this compressor can also suppress and control the rise in the discharge temperature of the compressor.

That is, in this embodiment, two bypass passages are provided, one for guiding the refrigerant from the discharge port of the compressor to the inlet side, and the other for guiding the refrigerant from the outlet side of the condenser to the inlet side of the compressor. The configuration is such that the flow rate is controlled by detecting the discharge temperature.

Specifically, on the upstream side of the flow rate control valve 11 as a flow rate control means, there are a bypass passage 12 similar to the previous embodiment that branches from the discharge port of the compressor 1 and a bypass passage 13 that branches from the outlet side of the condenser 2. They are connected to one common bypass passage 14 downstream of the control valve 11, and are connected to the inlet side of the compressor 1.

The calculation unit 15 receives input from both a temperature detector 16 that detects the condensing temperature corresponding to the pressure of the condenser 2 and a temperature detector 17 that detects the discharge port temperature of the compressor 1, and receives respective detection signals. The control valves are opened and closed in response to this, thereby controlling the flow rates of refrigerant in the bypass passages 12 and 13.

Therefore, as in the previous embodiment, when the pressure on the outlet side of the compressor rises above the set value, the control valve 11 opens and closes via the temperature detector 16 and the calculation section 15, and the bypass passages 12, 14? This refrigerant is caused to flow to suppress the increase in the discharge pressure.

At the same time, when the discharge temperature of the compressor 1 rises above the set value, the control valve 11 is opened and closed via the temperature detector 17 and the calculation unit 15, and a portion of the cooled liquid refrigerant downstream of the condenser is transferred to the bypass passage 13,
14 and is again compressed by the compressor 1, so the compressor 1
It is possible to reliably suppress the rise in the discharge port temperature of the compressor, thereby avoiding the adverse effects of overheating the compressor.

In other words, even if the structure of the previous embodiment suppresses the rise in the compressor discharge pressure, the temperature rise accompanying the pressure rise can be suppressed to some extent, but in this embodiment, the rise in the compressor discharge temperature is further suppressed. This is something that can be reliably suppressed.

In the above embodiment, the flow control valve is an on-off valve, and the discharge pressure and temperature of the compressor are controlled within a set range by repeated opening and closing operations. It may also be a throttle valve that controls the valve opening within the set temperature range.

In this case, for example, when controlling the pressure on the outlet side of the compressor, the control pressure does not take the form of a sawtooth broken line as shown in FIG. 2, but takes the form of a relatively flat straight line.

As described above, the present invention provides a bypass passage for recirculating the refrigerant in the compressor, and also provides a flow rate control means for controlling the bypass flow rate, and controls the flow rate control means to control the pressure at the outlet side of the compressor. By controlling the pressure accordingly, the increase in the pressure on the outlet side of the compressor is suppressed within a certain value, so that the durability of the compressor is improved without causing weekly load operation of the compressor.

[Brief explanation of drawings]

1 and 3 are circuit diagrams showing an embodiment of the refrigeration system according to the present invention, and FIG. 2 is a condensing pressure curve diagram of the refrigeration system shown in FIG. 1 during operation. In the figure, 1 is a compressor, 2 is a condenser, 3 is a pressure reduction device, 4 is an evaporator, 5, 12, 13, 14 are bypass passages, 6, 11
Is the flow control valve? , 16, 17 are temperature detectors, 8, 15
9 is a calculation unit, and 9 is a check valve.

Claims (1)

[Claims] 1. In a refrigeration system in which a compressor, a condenser, a pressure reducing device, and an evaporator are sequentially connected in a ring shape with a refrigerant pipe Q, high-pressure refrigerant on the outlet side of the compressor is transferred to the inlet side of the compressor. a return bypass passage; a flow rate control means provided in the bypass passage for controlling the flow rate of refrigerant in the passage; a blocking means for preventing high-pressure refrigerant returning from the bypass passage from flowing toward the evaporator; pressure detection means for detecting that the pressure on the outlet side has exceeded a predetermined value; and in response to a signal from the detection means, the flow rate control means is controlled so that the high-pressure refrigerant of the compressor is supplied through the bypass passage. A refrigeration device characterized in that the water is returned to the inlet side. 2. The refrigeration system according to claim 1, wherein the flow rate control means is constituted by a flow rate control valve. 3. The refrigeration system according to claim 1, wherein the blocking means is comprised of a check valve.