JP2013213592A - Rising control method of binary refrigeration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rising control method of a binary refrigeration system which can perform smooth rising until usual running without risk from causing both of high pressure abnormality of a low element refrigerant circuit and low pressure abnormality of a high element refrigerant circuit upon rising.SOLUTION: A binary refrigeration system 10 includes: a high element refrigerant circuit 12 in which a high element refrigerant circulates; and at least a low element refrigerant circuit 14 in which the high element refrigerant and a low element refrigerant heat-exchange in an intermediate heat exchanger 16 with using the intermediate heat exchanger 16 as a condensation part. The rising control method of the binary refrigeration system 10 has the steps of: starting the low element refrigerant circuit 14 to set the low element refrigerant to a given first pressure at the degree of a load required early in rising of the high element refrigerant circuit 12 side; pausing the low element refrigerant circuit 14 when the low element refrigerant reaches the given first pressure, and also starting the high element refrigerant circuit 12; and starting the low element refrigerant circuit 14 when the high element refrigerant of the low element refrigerant circuit 14 is depressurized down to a given second pressure.

Description

  The present invention relates to a start-up control method for a binary refrigeration apparatus, and more specifically, at the time of start-up, there is no risk of causing either a high-pressure abnormality in a low-source refrigerant circuit or a low-pressure abnormality in a high-source refrigerant circuit. The present invention relates to a start-up control method for a binary refrigeration apparatus that enables smooth start-up.

Conventionally, a device with high pressure resistance is not required, mainly by eliminating an increase in the amount of displacement on the low-stage side in a multi-stage compression refrigeration system while preventing an increase in the refrigerant condensing pressure during steady operation. In view of this, a binary refrigeration apparatus having different types of refrigerant is used.
For example, as disclosed in Patent Documents 1 to 3, the binary refrigeration apparatus is configured by sequentially connecting a compressor, a condenser, an expansion mechanism, and an evaporation unit of an intermediate heat exchanger, A high-side refrigerant circuit in which the high-source refrigerant circulates, a compressor, a condensing part of the intermediate heat exchanger, an expansion mechanism, and an evaporator are connected in order, and the low-source refrigerant circulates in the middle The heat exchanger includes at least one low-source side refrigerant circuit that exchanges heat between the high-source refrigerant and the low-source refrigerant.

Such a binary refrigeration apparatus is usually used to cope with a low temperature load such as an evaporation temperature of −60 ° C. or less, and in a state where the cascade temperature in the intermediate heat exchanger is lower than normal temperature. In, the heat balance between the high-side refrigerant circuit and the low-side refrigerant circuit is stably balanced, and heat is dissipated in the condenser of the high-side refrigerant circuit, or in the evaporator of the low-side refrigerant circuit, It is possible to obtain a cold source of freezer.
In a normal low temperature application of −60 ° C., the intermediate temperature at the steady state is lower than the normal temperature, so that it exists as a sufficient load even at the normal temperature start, and a low boiling point refrigerant suitable for it is used.
About the starting method of such a binary refrigeration apparatus, as a low-source refrigerant of the low-source side refrigerant circuit, a sufficient load for starting up the high-side refrigerant circuit is retained even in a state before starting in equilibrium with the ambient temperature. Since a low-boiling-point refrigerant (for example, R23 or R508A) is employed, the high-side refrigerant circuit is started first, thereby cooling the low-side refrigerant circuit, and the low-side refrigerant pressure is low after the pressure drops. The original refrigerant circuit was activated.
However, when such a binary refrigeration apparatus is used in, for example, a high-temperature region for exhaust heat recovery, if the conventional method for starting up the binary refrigeration apparatus is adopted, the following technical problems are caused. It is.
In other words, since the cascade temperature is near or higher than normal temperature, it is necessary to use a normal air-conditioning refrigerant as the low-source refrigerant in the low-source refrigerant circuit, which is inconvenient for starting up the high-source refrigerant circuit. If the load is sufficient and the low-side refrigerant circuit and the high-side refrigerant circuit are started at the same time, the amount of refrigerant circulating in the high-side refrigerant circuit cannot be increased sufficiently, and the high-side refrigerant circuit reaches a low-pressure cut. If the low-circulation refrigerant circuit reaches the starting condition while the refrigerant circulation amount of the high-generation refrigerant circuit cannot be sufficiently increased, the startup speed of the low-generation refrigerant circuit is Above that, it may lead to high-pressure cut of the low-side refrigerant circuit, and in any case, there is a high risk of abnormal stop before reaching steady operation.
JP 7-12439 A JP 2001-241789 A JP 2009-133539 A

  In view of the above technical problems, the object of the present invention is to achieve a smooth start-up until steady operation without causing any high-pressure abnormality of the low-source refrigerant circuit and low-pressure abnormality of the high-source refrigerant circuit at the time of start-up. An object of the present invention is to provide a method for controlling the start-up of a binary refrigeration apparatus.

In order to achieve the above object, a start-up control method for a binary refrigeration apparatus of the present invention includes:
A compressor, a condenser, an expansion mechanism, and an evaporation unit of an intermediate heat exchanger are connected in order, and a high-side refrigerant circuit in which high-source refrigerant circulates, a compressor, and the intermediate heat exchanger The condensing part, the expansion mechanism, and the evaporator are connected in order, and a low-source refrigerant having a lower boiling point than that of the high-source refrigerant circulates, and in the intermediate heat exchanger, the high-source refrigerant and the low-source refrigerant are In a start-up control method of a binary refrigeration apparatus comprising at least one low-source-side refrigerant circuit for heat exchange, and having a cascade temperature near room temperature or higher,
Activating the low-source refrigerant circuit and setting the low-source refrigerant to a predetermined first pressure that is a required load at the initial startup of the high-source refrigerant circuit;
When the low-source refrigerant reaches the predetermined first pressure, stopping the low-source refrigerant circuit and starting the high-source refrigerant circuit;
Activating the low-source refrigerant circuit when the low-source refrigerant in the low-source refrigerant circuit is depressurized to a predetermined second pressure;
It has the composition to have.

According to the start-up control method of the binary refrigeration apparatus having the above configuration, the low-source refrigerant of the low-source refrigerant circuit employed when the cascade temperature in the intermediate heat exchanger is near room temperature or higher is, for example, evaporated. Compared with the low-source refrigerant of the low-source refrigerant circuit used in the binary refrigeration system for low-temperature loads such as temperatures below -60 ° C, it is not a low-boiling point refrigerant, so the ambient (outside air) temperature and before the start of the equilibrium state The high pressure of the low-source refrigerant in the low-source refrigerant circuit is insufficient as a startup load for the high-source refrigerant circuit, and if the low-source refrigerant circuit and the high-source refrigerant circuit are started at the same time, the high-source refrigerant circuit can reach a low-pressure cut. However, by starting the low-source refrigerant circuit alone first, the high-source refrigerant circuit is started after stopping at a predetermined first high pressure that is a necessary load at the initial start-up on the high-source refrigerant circuit side. By doing In addition to preventing such a low-pressure cut in the high-source refrigerant circuit, the heating capability of the low-source refrigerant circuit is more than the cooling capability on the high-source refrigerant circuit side, so that the low-source refrigerant circuit does not reach the high-pressure cut. In addition, after the low-source refrigerant in the low-source refrigerant circuit is depressurized to the predetermined second pressure, the low-source refrigerant circuit is activated, and thus both the high-pressure abnormality in the low-source refrigerant circuit and the low-pressure abnormality in the high-source refrigerant circuit It is possible to start up smoothly until steady operation without fear.
In this specification, the steady operation means a stable operation state that converges according to the load unless a disturbance is input to the system, and the rising operation means an operation state from the start of the system to such a steady operation. Is used to mean

Furthermore, before starting the binary refrigeration apparatus, detecting the high pressure of the low-source refrigerant in the low-source refrigerant circuit;
Starting the low-source refrigerant circuit if the detected high-pressure pressure of the low-source refrigerant is lower than the predetermined third pressure and starting the high-source refrigerant circuit if the low-source refrigerant circuit is equal to or equal to the predetermined third pressure; Furthermore, it is good to have.
Furthermore, the predetermined third pressure is higher than the predetermined second pressure and lower than the predetermined first pressure.

In addition, the low-source refrigerant may be a normal air-conditioning refrigerant.
Further, the low-source refrigerant may be such that the pressure during stopping in equilibrium with the ambient temperature is lower than the pressure during operation.
The low-source refrigerant may be R134a and the high-source refrigerant may be R245fa.

Further, the cascade temperature may be 10 ° C. or higher.
In addition, the binary refrigeration apparatus may be used for exhaust heat recovery using the evaporator of the low-source refrigerant circuit.
The predetermined first pressure, the predetermined second pressure, and the predetermined third pressure may be determined based on the type of refrigerant used, the rotational speed of the compressor, and the exhaust heat recovery temperature, respectively.

An embodiment of a binary refrigeration apparatus 10 according to the present invention will be described below in detail with reference to the drawings.
In FIG. 1, a high temperature side refrigerant circuit 12 and a low level refrigerant circuit 14 are connected to each other by an intermediate heat exchanger 16 in a binary refrigeration apparatus 10. For example, R245fa may be used as the high-side refrigerant, and R134a may be used as the low-side refrigerant, for example, and a normal air-conditioning refrigerant may be used. The low source side refrigerant has a lower pressure in operation at equilibrium with the ambient temperature than the operating pressure.
The high-end side refrigerant circuit 12 is schematically configured such that the other end of the high-end side refrigerant outlet pipe 20 whose one end is connected to the discharge side of the high-end side compressor 18 is connected via a condenser 22 and an expansion valve 24. The other end of the high-side refrigerant return pipe 26 connected to the primary-side flow path inlet of the intermediate heat exchanger 16 and connected to one end of the primary-side flow path outlet is connected to the suction side of the high-side compressor 18. Connected to form a refrigerant circuit.

On the other hand, the low-side refrigerant circuit 14 is generally configured such that the other end of the low-side refrigerant outgoing pipe 30 whose one end is connected to the discharge side of the low-side compressor 28 is the secondary side of the intermediate heat exchanger 16. The other end of the low-side refrigerant return pipe 32 connected to the flow path inlet and connected at one end to the secondary flow path outlet is connected to the suction side of the low-side compressor 28 via the expansion valve 34 and the evaporator 36. To form a refrigerant circuit.
The intermediate heat exchanger 16 is configured as a dry evaporator, and a heat exchange pipe (not shown) connected to the high-side refrigerant circuit 12 is disposed inside the intermediate heat exchanger 16, and the intermediate heat exchanger 16 is low on the trunk side. The original refrigerant gas is filled. As a result, heat exchange occurs between the high-side refrigerant and the low-side refrigerant gas outside the tube to condense the low-side refrigerant, and the high-side refrigerant becomes dry gas at the outlet of the intermediate heat exchanger 16. The original compressor 18 is sucked.
As the high-end compressor 18, for example, a capacity-controlled reciprocating compressor or a rotary or centrifugal compressor is used. Particularly, in the case of a reciprocating compressor, the lubricant is returned to a low pressure chamber such as a crank chamber, and in the case of a screw compressor, the lubricant is returned to a low pressure region or an intermediate pressure region of the compressor casing. The drive motor 38 of the high-end compressor 18 in the high-end refrigerant circuit 12 is provided with an inverter device 40 so that the rotation speed of the drive motor 38 can be controlled.

An oil separator 42 is provided on the downstream side of the high-end compressor 18, and the lubricant separated by the oil separator 42 is returned to the high-end compressor 18. A condenser 22 and a liquid receiver 44 are sequentially provided on the downstream side of the oil separator 42, and the high-side refrigerant circuit 12 is opened and closed on the downstream side of the liquid receiver 44 when the operation is started or stopped. An electromagnetic valve (not shown) and an expansion valve 24 are provided. The condenser 22 may be an evaporation type, a water cooling type, or an air cooling type. A high-side refrigerant return pipe 26 upstream of the high-side compressor 18 is provided with a temperature sensor (not shown) for detecting the refrigerant gas temperature and a pressure sensor (not shown) for detecting the refrigerant gas pressure. ing.

On the other hand, in the low-side refrigerant circuit 14, an accumulator 46 is provided on the upstream side of the low-side compressor 28, and droplets in the refrigerant are removed here.
In particular, in the low-side refrigerant circuit 14, when the low-side refrigerant is at a considerably low temperature, the viscosity of the lubricant mixed in the low-side refrigerant increases, so the lubricant is added to the accumulator 46. Since the lubricant adheres to the accumulator 46 and increases the pressure loss of the low-side refrigerant circuit 14 or closes the low-side refrigerant circuit 14, the Similar to the former side compressor 18, an oil separator is provided, and the lubricant separated by the oil separator is used as a refrigerant flow path between the low pressure side of the low side compressor 28 or the accumulator 46 and the low side compressor 28. You may return to.

As with the high-source side compressor 18, for example, a capacity-controlled reciprocating compressor or a rotary or centrifugal compressor is used as the low-side compressor 28. Particularly, in the case of a reciprocating compressor, the lubricant is returned to a low pressure chamber such as a crank chamber, and in the case of a screw compressor, the lubricant is returned to a low pressure region or an intermediate pressure region of the compressor casing.

  As with the high-side compressor 18, the drive motor 48 for the low-side compressor 28 in the low-side refrigerant circuit 14 is provided with an inverter device 50 so that the rotational speed can be controlled. Note that the control unit 52 controls the inverter device 40 of the high-source side compressor 18 and the inverter device 50 in the low-side refrigerant circuit 14 respectively.

A liquid receiver 54 is provided on the downstream side of the intermediate heat exchanger 16, and the low-source-side refrigerant liquid condensed in the intermediate heat exchanger 16 is supplied to the liquid receiver 54.
The low-side refrigerant gas is sucked into the low-side compressor 28 through the low-side refrigerant return pipe 32. The low-source-side refrigerant return pipe 32 is provided with a suction pressure adjustment valve (not shown), where the compressor suction pressure of the low-source-side refrigerant gas is adjusted. Further, the low-side refrigerant return pipe 32 is provided with a pressure sensor (not shown) for detecting the compressor suction pressure.
A hot gas line 56 is provided to connect the low-source side refrigerant return pipe 32 and the body portion of the intermediate heat exchanger 16. The hot gas line 56 includes a hot gas motor-operated valve (not shown) and an operation start or A hot gas solenoid valve (not shown) for opening and closing the hot gas line 56 at the time of stopping is attached.

The low-side refrigerant gas discharged from the low-side compressor 28 to the low-side refrigerant outgoing pipe 30 is supplied to the intermediate heat exchanger 16 and is cooled and condensed by the high-source refrigerant in the intermediate heat exchanger 16. The condensed low-source refrigerant liquid is further subcooled and sent to the expansion valve 34.

FIG. 2 shows an example of the temperature balance between the high-side refrigerant and the low-side refrigerant. In the figure, the high-side refrigerant saturation T1 is the condensation temperature of the high-side refrigerant in the condenser 22, the low-side refrigerant saturation T1 is the condensation temperature of the low-side refrigerant in the intermediate heat exchanger 16, and the high-side refrigerant saturation. T2 is the evaporation temperature of the high-side refrigerant in the intermediate heat exchanger 16, and low-side refrigerant saturation T2 is the evaporation temperature of the low-side refrigerant in the evaporator 36.

  In the above-described embodiment, a configuration in which a load is connected to the low-side evaporator 36, that is, a cooling operation is performed, and a heating operation in which a load is connected to the high-side condenser 22 (for example, heating) Or when it is applied as a steam generator, or a configuration in which these can be switched alternately.

In the intermediate heat exchanger 16, the high-side refrigerant liquid or gas-liquid mixture is vaporized by heat exchange with the low-side refrigerant gas, and is sucked into the high-side compressor 18 through the high-side refrigerant return pipe 26. At that time, from the viewpoint of preventing liquid compression, the degree of superheat in the operating state is adjusted to the target degree of superheat.

    In the binary refrigeration apparatus 10 having the above configuration, when the cascade temperature is close to or higher than the normal temperature, not only the high-side refrigerant but also the low-side refrigerant is not so low boiling point refrigerant. From the viewpoint of preventing both the high pressure cut of the original refrigerant circuit and the low pressure cut of the high original refrigerant circuit, the operation is performed as follows.

    As shown in FIG. 3, first, before starting the binary refrigeration apparatus 10, the high-pressure pressure of the low-source refrigerant in the low-source refrigerant circuit 14 is detected (step 1). If the detected high-pressure pressure PL of the low-source refrigerant is lower than the predetermined pressure P1 (step 2), the low-source refrigerant circuit 14 is activated (step 3), and if it is equal to P1 or higher than P1, the high-source refrigerant circuit 12 is activated. Start (step 4). Next, the low-source refrigerant circuit 14 is started, and the low-source refrigerant is set to a predetermined pressure P2 that is a load necessary for the initial startup on the high-source refrigerant circuit 12 side. That is, when the low-source refrigerant pressure reaches P2 (Step 5), the low-source refrigerant circuit 14 is stopped (Step 6) and the high-source refrigerant circuit is activated (Step 7). Next, when the low-source refrigerant in the low-source refrigerant circuit 14 is depressurized to a predetermined pressure P3 (step 8), the low-source refrigerant circuit 14 is activated (step 9).

In this case, P1 is higher than P3 and lower than P2. P1, P2 and P3 are preferably determined based on the type of refrigerant used, the rotational speed of the compressor, and the exhaust heat recovery temperature.
The binary refrigeration apparatus may be used for exhaust heat recovery using an evaporator of a low-source refrigerant circuit.

According to the start-up control method of the binary refrigeration apparatus 10 having the above configuration, the low-source refrigerant of the low-source refrigerant circuit 14 employed when the cascade temperature in the intermediate heat exchanger is near normal temperature or higher, For example, it is not a low-boiling point refrigerant as compared with the low-source refrigerant of the low-source refrigerant circuit 14 employed in a binary refrigeration apparatus for a low temperature load such as an evaporation temperature of −60 ° C. or lower. The high pressure of the low-source refrigerant in the low-source refrigerant circuit 14 before startup becomes insufficient as a starting load for the high-source refrigerant circuit 12, and if the low-source refrigerant circuit 14 and the high-source refrigerant circuit 12 are started simultaneously, the high-source refrigerant There is a possibility that the circuit 12 may reach a low pressure cut, and by starting the low-source refrigerant circuit 14 alone first, a predetermined first high pressure that is a required load at the initial startup of the high-source refrigerant circuit side 12 is obtained. Stop as Then, by starting the high-source refrigerant circuit 12, the low-pressure cut of the high-source refrigerant circuit 12 is prevented and the heating capability of the low-source refrigerant circuit 14 wins over the cooling capability on the high-source refrigerant circuit 12 side. On the contrary, the low-source refrigerant circuit 14 is activated after the low-source refrigerant in the low-source refrigerant circuit 14 is depressurized to a predetermined second pressure so that the low-source refrigerant circuit 14 does not reach a high-pressure cut. Thus, it is possible to smoothly start up to a steady operation without causing any high pressure abnormality of the low-source refrigerant circuit 14 and low-pressure abnormality of the high-source refrigerant circuit 12.

The embodiments of the present invention have been described in detail above, but various modifications or changes can be made by those skilled in the art without departing from the scope of the present invention.
For example, in the present embodiment, during start-up operation, the low-source-side refrigerant high-pressure is detected. If the pressure is lower than a predetermined pressure, the low-source-side refrigerant circuit is activated first, and if it is high, the high-source-side refrigerant circuit is activated first. However, the present invention is not limited to this, and when it is clear that the low-side refrigerant pressure is sufficiently low, the detection of such low-side refrigerant pressure is omitted and the low-side refrigerant pressure is immediately reduced. The former-side refrigerant circuit may be activated first.

1 is an overall configuration diagram of a binary refrigeration apparatus according to an embodiment of the present invention. It is a diagram which shows the temperature balance of the binary refrigeration apparatus which concerns on embodiment of this invention. In the binary refrigeration apparatus concerning the embodiment of the present invention, it is a flow figure showing the operation flow of start-up operation.

DESCRIPTION OF SYMBOLS 10 Binary refrigeration apparatus 12 High side refrigerant circuit 14 Low side refrigerant circuit 16 Intermediate heat exchanger 18 High side compressor 20 High side refrigerant forward pipe 22 Condenser 24 Expansion valve 26 High side refrigerant return pipe 28 Low Original compressor 30 Low original refrigerant return pipe 32 Low original refrigerant return pipe 34 Expansion valve 36 Evaporator 38 Drive motor 40 Inverter device 42 Oil separator 44 Liquid receiver 46 Accumulator 48 Drive motor 50 Inverter device 52 Control Part 54 liquid receiver 56 hot gas line

Claims (9)

A compressor, a condenser, an expansion mechanism, and an evaporation unit of an intermediate heat exchanger are connected in order, and a high-side refrigerant circuit in which high-source refrigerant circulates, a compressor, and the intermediate heat exchanger The condensing part, the expansion mechanism, and the evaporator are connected in order, and a low-source refrigerant having a lower boiling point than that of the high-source refrigerant circulates, and in the intermediate heat exchanger, the high-source refrigerant and the low-source refrigerant are In a start-up control method of a binary refrigeration apparatus comprising at least one low-source-side refrigerant circuit for heat exchange, and having a cascade temperature near room temperature or higher,
Activating the low-source refrigerant circuit and setting the low-source refrigerant to a predetermined first pressure that is a required load at the initial startup of the high-source refrigerant circuit;
When the low-source refrigerant reaches the predetermined first pressure, stopping the low-source refrigerant circuit and starting the high-source refrigerant circuit;
Activating the low-source refrigerant circuit when the low-source refrigerant in the low-source refrigerant circuit is depressurized to a predetermined second pressure;
A start-up control method for a binary refrigeration apparatus, comprising: Detecting the high pressure of the low-source refrigerant in the low-source refrigerant circuit before starting the binary refrigeration system;
Starting the low-source refrigerant circuit if the detected high-pressure pressure of the low-source refrigerant is lower than the predetermined third pressure and starting the high-source refrigerant circuit if the low-source refrigerant circuit is equal to or equal to the predetermined third pressure; The start-up control method for a binary refrigeration apparatus according to claim 1, further comprising: The start-up control method for a binary refrigeration apparatus according to claim 2, wherein the predetermined third pressure is higher than the predetermined second pressure and lower than the predetermined first pressure. The start-up control method for a binary refrigeration apparatus according to claim 1, wherein the low-source refrigerant is a normal air-conditioning refrigerant. 5. The start-up control method for a binary refrigeration apparatus according to claim 4, wherein the low-source refrigerant has a pressure in a state of equilibrium with an ambient temperature that is lower than a pressure during operation. The start-up control method for a binary refrigeration apparatus according to claim 5, wherein the low-source refrigerant is R134a, and the high-source refrigerant is R245fa. The start-up control method for a binary refrigeration apparatus according to claim 5, wherein the cascade temperature is 10 ° C or higher. 5. The start-up control method for a binary refrigeration apparatus according to claim 4, wherein the binary refrigeration apparatus is used for exhaust heat recovery using the evaporator of the low-source refrigerant circuit. The binary according to claim 8, wherein the predetermined first pressure, the predetermined second pressure, and the predetermined third pressure are determined based on a type of refrigerant to be used, a rotation speed of a compressor, and an exhaust heat recovery temperature, respectively. Start-up control method for refrigeration equipment.

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