JP2017161127A - Vapor compression type refrigerator and control method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vapor compression type refrigerator enabling energy consumption for separation of non-condensable gas from refrigerant and discharging the non-condensable gas to be suppressed as much as possible.SOLUTION: The vapor compression type refrigerator comprises a bleeding device 40 and a control unit. The bleeding device 40 includes: a cooling unit that cools gas bled from a condenser 5 to condense condensable gas; and an exhaust pump 48 for discharging the non-condensable gas separated without being condensed by the cooling unit to the outside. The control unit calculates the current temperature difference which is the difference between: the current saturation temperature in the condenser 5 and the current outlet temperature of the cooling water heat transfer tube 5a; and the planned temperature difference, and calculates the current rise in the temperature difference due to the contamination inside the tube using information on rise in temperature difference due to contamination inside the tube, which is the difference between the saturation temperature in the condenser 5 and the outlet temperature of the cooling water heat transfer tube 5a, which is determined in advance on the assumption of contamination inside the tube of the cooling water heat transfer tube 5a. The control unit causes the bleeding device 40 to operate when the increase of the current temperature difference from the planned temperature difference becomes larger than the current increase of the temperature difference due to the contamination inside the tube by a predetermined value or more.SELECTED DRAWING: Figure 1

Description

  TECHNICAL FIELD The present invention relates to a vapor compression refrigerator equipped with an extraction device for extracting noncondensable gas from a condenser and a control method thereof.

  In refrigeration equipment that uses refrigerant whose operating pressure during operation is partly lower than atmospheric pressure in the machine, after non-condensable gas such as air enters the machine and passes through the compressor etc. Stay in the condenser. If the non-condensable gas stays in the condenser, the non-condensable gas becomes a heat transfer resistance, the refrigerant condensing performance in the condenser is hindered, and the performance as a cooling device is lowered. For this reason, normal performance is ensured by discharging non-condensable gas from the condenser to the outside of the apparatus using the bleeder. The extraction device draws non-condensable gas into the extraction device as a mixed gas with the refrigerant gas, and the mixed gas is cooled and only the refrigerant is condensed and returned to the refrigerator, whereby the non-condensable gas is separated and accumulated, It is discharged out of the machine by an exhaust pump or the like (see Patent Documents 1 and 2 below).

Japanese Patent Laid-Open No. 2001-50618 JP 2006-38346 A

  However, in order to condense and separate the refrigerant sucked into the extraction device together with the non-condensable gas, a certain amount of cooling heat is required. As means for cooling, there are a method of cooling using a low-temperature medium such as cold water or an in-machine refrigerant, and a method of cooling using an electric cooling device. When a low temperature medium is used, the medium cooled by the refrigerator is heated, resulting in a loss of efficiency as a device. When electric cooling is performed, a certain amount of power is consumed. Therefore, it is desirable that the bleeder be automatically operated only when necessary to avoid unnecessary power consumption.

  To detect a decrease in condensation performance in a water-cooled condenser, detect the difference between the saturation temperature of the condenser and the cooling water temperature and monitor whether the temperature difference rises from the planned temperature difference. However, since the condensation performance of the condenser deteriorates due to contamination on the heat transfer surface (cooling water side), it is difficult to separate the condenser from the deterioration of performance due to non-condensable gas.

  The present invention has been made in view of such circumstances, and is a vapor compression refrigerator that can suppress energy consumption when separating and discharging non-condensable gas from a refrigerant as much as possible, and its control. It aims to provide a method.

In order to solve the above problems, the vapor compression refrigerator and the control method thereof according to the present invention employ the following means.
That is, a vapor compression refrigerator according to the present invention distributes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and cooling water that exchanges heat with the refrigerant in the condenser. A cooling water heat transfer tube to be expanded, an expansion valve for expanding the liquid refrigerant introduced from the condenser, an evaporator for evaporating the refrigerant expanded by the expansion valve, and gas extracted from the condenser, A bleeder having a cooling part for condensing condensed gas and a non-condensable gas separated without being condensed by the cooling part, and a control part for controlling the bleeder. The controller calculates a current temperature difference that is a difference between a current saturation temperature in the condenser and a current outlet temperature of the cooling water heat transfer tube and a planned temperature difference that is a planned value, and the cooling water. Assuming dirt in the heat transfer tube Using the information on the temperature difference increase due to dirt in the pipe, which is the difference between the saturated temperature in the condenser determined in advance and the outlet temperature of the cooling water heat transfer pipe, the temperature difference rise due to the current pipe dirt is calculated, and the current temperature The bleeder is operated when an increase in the difference from the planned temperature difference is greater than a predetermined value more than a temperature difference increase due to the current pipe contamination.

The decrease in the condensation performance of the condenser may be due to heat transfer inhibition due to dirt in the cooling water heat transfer pipe and heat transfer inhibition due to retention of non-condensable gas in the condenser.
If the current temperature difference, which is the difference between the current saturation temperature in the condenser and the current outlet temperature of the cooling water heat transfer tube, is higher than the planned temperature difference, which is the planned value, dirt in the tube and non-condensable gas retention Both effects are reflected. On the other hand, an increase in temperature difference due to dirt in the tube can be grasped by a preliminary test or the like in which cooling water is circulated in the heat transfer tube. Therefore, a value obtained by subtracting the temperature difference increase due to the current pipe contamination from the current temperature difference can be evaluated as a decrease in condensation performance due to non-condensable gas retention. Therefore, when the current temperature difference becomes larger than the sum of the planned temperature difference and the current increase in the in-pipe dirt temperature difference, it is determined that the condensation performance is reduced due to non-condensable gas retention, and the bleeder is operated. As a result, the extraction device can be operated only when a predetermined amount or more of non-condensable gas stays in the condenser, so that wasteful energy consumption can be suppressed and a vapor compression refrigerator with high overall efficiency can be realized. .
The saturation temperature of the condenser can be obtained from a pressure value obtained from a pressure sensor provided in the condenser.

  Further, the vapor compression refrigerator of the present invention further includes a differential pressure sensor that detects a differential pressure between the inlet and outlet of the condenser of the cooling water heat transfer tube, and the temperature difference increase due to dirt in the tube is detected by the differential pressure sensor. It is determined based on the amount of increase from the planned value of the current differential pressure obtained in (1).

  The dirt in the heat transfer pipe for cooling water is due to the deposits in the heat transfer pipe, and the deposits narrow the flow path in the heat transfer pipe, thereby causing a difference between the inlet and outlet of the heat transfer pipe for cooling water in the condenser. The pressure rises above the planned value. Therefore, by determining the pipe dirt temperature difference based on the differential pressure increase value from the planned value, the pipe dirt can be accurately estimated.

  The vapor compression refrigerator of the present invention further includes a cooling water flow sensor for measuring a flow rate of the cooling water flowing in the cooling water heat transfer pipe, and the temperature difference increase of the dirt in the pipe is caused by the cooling water flow sensor. It is determined based on the flow rate obtained in the above.

  The increase in the dirt temperature in the pipe depends on the rise in the differential pressure, and the pressure difference depends on the flow rate. Therefore, the increase in the dirt temperature in the pipe is determined based on the flow rate and the differential pressure obtained by the cooling water flow sensor. Thereby, the dirt in the pipe can be accurately estimated.

  Furthermore, in the vapor compression refrigerator of the present invention, a chilled water heat transfer tube that circulates chilled water that exchanges heat with the refrigerant in the evaporator, a chilled water flow rate sensor that measures the flow rate of the chilled water flowing in the chilled water heat transfer tube, and A temperature sensor that measures the inlet / outlet temperature of the chilled water in the heat transfer pipe for cold water, and a temperature sensor that measures the inlet / outlet temperature of the cooling water in the cooling water heat transfer pipe, wherein the control unit is obtained from the chilled water flow rate sensor. The cooling water flow rate, the refrigeration capacity calculated from the cold water inlet / outlet temperature difference of the cold water heat transfer tube in the evaporator, the power input to the compressor, and the cooling water inlet / outlet of the cooling water heat transfer tube in the condenser Based on the temperature difference, a flow rate of cooling water flowing in the heat transfer pipe for cooling water is calculated from a heat balance, and an increase in temperature difference due to dirt in the pipe is determined based on the flow rate of cooling water. .

If there is no cooling water flow sensor to measure the cooling water flow rate, it is based on the cold water flow rate obtained from the cold water flow sensor, the cold water inlet / outlet temperature difference, the power input to the compressor, and the cooling water inlet / outlet temperature difference. The coolant flow rate can be calculated from the heat balance. Thereby, a cooling water flow sensor can be omitted and cost can be reduced.
When there is no chilled water flow rate sensor, the chilled water flow rate can be calculated by using the chilled water differential pressure and the loss coefficient of the chilled water heat transfer tube.

  Further, the control method of the vapor compression refrigerator of the present invention includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and cooling water that exchanges heat with the refrigerant in the condenser. A cooling water heat transfer tube that circulates, an expansion valve that expands the liquid refrigerant led from the condenser, an evaporator that evaporates the refrigerant expanded by the expansion valve, and a gas is extracted from the condenser, A vapor compression refrigeration machine comprising: a cooling unit that cools the gas to condense condensed gas; and a bleeder that has a discharge unit that discharges uncondensed gas that has not been condensed by the cooling unit to the outside. A control method, wherein a current temperature difference that is a difference between a current saturation temperature in the condenser and a current outlet temperature of the cooling water heat transfer tube and a planned temperature difference that is a planned value are calculated, and the cooling water Assuming dirt inside the heat transfer tube Using the information on the increase in the fouling temperature difference in the pipe, which is the difference between the determined saturation temperature in the condenser and the outlet temperature of the heat transfer pipe for cooling water, the temperature difference rise due to the fouling in the current pipe is calculated, and the current temperature difference The bleeder is operated when an increase from the planned temperature difference is greater than a predetermined value by a value greater than a temperature difference increase due to the current pipe contamination.

  Since the extraction device and the cooling device are operated only when a predetermined amount or more of non-condensable gas stays in the condenser, energy consumption when separating and discharging the non-condensable gas from the refrigerant is made as much as possible. Can be suppressed.

It is the schematic block diagram which showed the turbo refrigerator based on one Embodiment of this invention. It is a control block diagram of a control part. It is the graph which showed the cooling water pressure loss with respect to the temperature difference in a cooling water exit. It is the flowchart which showed starting and stop control of the extraction apparatus which concerns on one Embodiment of this invention. It is the graph which showed the timing of starting and a stop of a bleeder.

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

As shown in FIG. 1, the turbo refrigerator 1 includes a turbo compressor 3 that compresses a refrigerant, a condenser 5 that condenses a high-temperature and high-pressure gas refrigerant compressed by the turbo compressor 3, and a condenser 5. The expansion valve 7 expands the liquid refrigerant introduced from the expansion valve 7 and the evaporator 9 evaporates the liquid refrigerant expanded by the expansion valve 7.
As the refrigerant, for example, a low-pressure refrigerant such as HFO-1233zd (E) is used, and a low-pressure part such as an evaporator becomes an atmospheric pressure or lower during operation.

  The turbo compressor 3 is a centrifugal compressor, and is driven by an electric motor 11 whose rotational speed is controlled by an inverter. The output of the inverter is controlled by a control unit (not shown). The input power W of the electric motor 11 is measured by the wattmeter 13 and the measurement result is sent to a control unit (not shown).

  The turbo compressor 3 includes an impeller 3a that rotates around a rotation shaft 3b. Rotational power is transmitted from the electric motor 11 to the rotary shaft 3b via the speed increasing gear 15.

The condenser 5 is a heat exchanger that is, for example, a shell and tube type.
The condenser 5 is inserted with a cooling water heat transfer tube 5a through which cooling water for cooling the refrigerant flows. A cooling water forward pipe 6a and a cooling water return pipe 6b are connected to the cooling water heat transfer pipe 5a. The cooling water guided to the condenser 5 via the cooling water return pipe 6a is guided to a cooling tower (not shown) via the cooling water return pipe 6b and exhausted to the outside, and then is discharged via the cooling water return pipe 6a. It is led to the condenser 5 again.
A cooling water pump 20 that supplies cooling water, a cooling water flow sensor 22 that measures the cooling water flow rate GWC, and a cooling water inlet temperature sensor 24 that measures the cooling water inlet temperature TWCI are provided in the cooling water going pipe 6a. It has been. The cooling water return pipe 6b is provided with a cooling water outlet temperature sensor 26 for measuring the cooling water outlet temperature TWCO. Further, a cooling water differential pressure sensor 28 that measures the differential pressure PDc at the inlet / outlet of the cooling water is provided between the cooling water going-out pipe 6a and the cooling water return pipe 6b.
The condenser 5 is provided with a condenser pressure sensor 29 that measures the condenser pressure Pc of the refrigerant in the condenser 5.
The measured values of these sensors 22, 24, 26, 28, and 29 are transmitted to the control unit.

  The expansion valve 7 is electrically operated, and the opening degree is arbitrarily set by the control unit.

The evaporator 9 is a heat exchanger of, for example, a shell and tube type.
The evaporator 9 is inserted with a cold water heat transfer tube 9a through which cold water that exchanges heat with the refrigerant flows. The cold water heat transfer pipe 9a is connected with a cold water forward pipe 10a and a cold water return pipe 10b. The chilled water led to the evaporator 9 through the chilled water outgoing pipe 10a is cooled to a rated temperature (for example, 7 ° C.), and is led to an external load (not shown) through the chilled water return pipe 10b to supply cold heat. It is led again to the evaporator 9 via the forward piping 10a.
The chilled water delivery pipe 10a is provided with a chilled water pump 30 for feeding chilled water, a chilled water flow rate sensor 32 for measuring the chilled water flow rate GWE, and a chilled water inlet temperature sensor 34 for measuring the chilled water inlet temperature TWEI. The cold water return pipe 10b is provided with a cold water outlet temperature sensor 36 for measuring the cold water outlet temperature TWEO. Further, a chilled water differential pressure sensor 38 for measuring the differential pressure PDe at the inlet / outlet of the chilled water is provided between the chilled water outgoing pipe 10a and the chilled water return pipe 10b.
The measurement values of these sensors 32, 34, 36, and 38 are transmitted to the control unit.

An extraction device 40 is provided between the condenser 5 and the evaporator 9. The extraction device 40 is connected to an extraction piping 42 that guides a refrigerant (condensed gas) containing non-condensable gas from the condenser 5. In addition, a liquid refrigerant pipe 44 that guides the condensed liquid refrigerant to the evaporator 9 is connected to the extraction device 40. The bleeder 40 is connected to a discharge pipe 46 for discharging non-condensable gas to the outside. The discharge pipe 46 is provided with an exhaust pump (discharge unit) 48. The operation of the exhaust pump 48 is controlled by the control unit.
Further, as shown by an arrow 49, the bleeder 40 is supplied with cold heat for cooling the refrigerant containing the non-condensable gas introduced into the bleeder 40. As a cooling unit for supplying cold heat, a refrigerator having a refrigeration cycle different from the turbo refrigerator 1, a means for supplying cold water, a means for supplying refrigerant in the turbo refrigerator 1, a cooling means by a Peltier element, etc. Is mentioned. The operations of these cooling units are performed by a control unit (not shown).

  The control unit performs control related to the operation of the turbo chiller 1, and includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a computer-readable storage medium, and the like. Yes. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program as an example, and the CPU reads the program into a RAM or the like to execute information processing / arithmetic processing. As a result, various functions are realized. The program is preinstalled in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Etc. may be applied. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

FIG. 2 shows a block diagram of the control unit.
The storage unit 50 stores data for determining the operation of the extraction device 40 as will be described later.
The operation value calculation unit 52 receives the measurement values from the above-described sensors and the data from the storage unit 50, and performs various calculations for determining the operation of the bleeder 40.
The operation state determination unit 54 determines the operation of the bleeder 40 from the information obtained from the operation state calculation unit 52.
In the control command unit 56, a command to start or stop the extraction device 40 is issued based on the output from the operation state determination unit 54.

Next, the concept of determining whether to start or stop the extraction device 40 will be described with reference to FIG.
In FIG. 3, the horizontal axis represents an increase value from the plan of the temperature difference between the cooling water outlet temperature TWCO and the condenser saturation temperature TCs calculated from the condenser pressure Pc. The vertical axis is an increase from the planned value of the cooling water pressure loss, and shows an increase in pressure difference between the inlet and outlet due to contamination of the cooling water in the cooling water heat transfer tube 5a. As described above, FIG. 3 shows the in-tube fouling temperature difference information indicating that the thermal resistance increases due to the fouling in the tube. The increase in pressure difference taking this dirt into account can be obtained by a preliminary test or the like.

  For example, when the increase from the planned value of the differential pressure PDc measured by the cooling water differential pressure sensor 28 is 4 kPa, according to FIG. 3, the temperature difference increase due to pressure loss due to dirt is about 1 ° C. However, when the rise of the cooling water inlet / outlet temperature difference (TWCO-TWCI) actually measured by the temperature sensors 24 and 26 is 2 ° C., 1 ° C. of the difference in temperature rise is a non-condensable gas. This is considered to be a deterioration of the condensability due to. When this temperature rise exceeds a predetermined value, a command is issued from the control unit so as to activate the bleeder 40.

FIG. 4 shows specific control of the bleeder 40.
First, it is assumed that the turbo chiller 1 is normally operated as in step S1. At this time, the bleeder 40 is stopped.
And a control part judges whether the following formula is satisfy | filled like step S2.
(TDact−TDsp) −ΔTDf> ΔTDset1 (1)

TDact of the formula (1) is a difference (measured value) [° C.] between the saturation temperature of the condenser pressure Pc and the cooling water outlet temperature TWCO. Here, TDact = TCs−TWCO.
TCs is the condenser pressure saturation temperature [° C.] and is given as a function of the condenser pressure Pc.
The cooling water outlet temperature TWCO is a measured value measured by the cooling water outlet temperature sensor 26.

The TDsp in the formula (1) is a difference (set value) [° C.] between the normal condenser saturation temperature and the cooling water outlet temperature. Here, the normal time means that no non-condensable gas exists in the condenser 5 and the cooling water heat transfer tube 5a is not contaminated.
TDsp is expressed by the equation TDsp = f (Qr), and is a function of the refrigerator load factor Qr (= Qact / Qsp). Here, Qact is the actual measurement value [kW] of the refrigeration capacity, and Qsp is the rated refrigeration capacity [kW].

ΔTDf in the equation (1) is an increase (set value) [° C.] of a temperature difference due to contamination in the cooling water heat transfer tube 5a. Here, ΔTDf is expressed by an equation: ΔTDf = f (ΔPDc).
ΔPDc means an increase from the planned value of the cooling water pressure, and is a differential pressure increase [kPa] between the inlet and outlet of the cooling water heat transfer tube 5a. ΔPDc is expressed by an equation: ΔPDc = PDcact−PDcsp.
PDcact is a differential pressure [kPa] between the inlet and outlet of the cooling water heat transfer tube 5 a measured by the cooling water differential pressure sensor 28.
PDcsp is a specification value [kPa] of the loss of the cooling water heat transfer pipe 5a with respect to the flow rate, and means a pressure loss in a state where the cooling water heat transfer pipe 5a is not contaminated. Therefore, PDcsp is a function of the cooling water flow rate GWC [m ³ / h].

  ΔTDset1 in equation (1) is a setting value that determines that the operation of the bleeder 40 is necessary, and is determined in advance by a preliminary test or the like.

As can be seen from the equation (1), from the rise (TDact−TDsp) from the planned value of the temperature difference between the condenser saturation temperature and the cooling water outlet temperature TWCO, the influence of the dirt in the cooling water heat transfer pipe 5a (ΔTDf) When the temperature difference increase obtained by subtracting is equal to or larger than the set value ΔTDset1, it is determined that the performance degradation due to the non-condensable gas in the condenser 5 is large, and the extraction device 40 is operated.
Therefore, when Formula (1) is satisfy | filled, it progresses to step S3 and a control part starts the extraction apparatus 40. FIG. At this time, the bleeder 40 is powered on for the first time.

And a control part judges whether the following formula is satisfy | filled like step S4.
(TDact−TDsp) −ΔTDf <ΔTDset2 (2)
The left side of Formula (2) is the same as Formula (1).
If Expression (2) is satisfied, the control unit stops the bleeder 40 (step S5).
Note that ΔTDset2 is a value smaller than ΔTDset1 by a predetermined temperature. As a result, as shown in FIG. 5, a temperature difference is given to the conditions for starting the extraction operation and stopping the extraction operation so that the start and stop are not frequently generated.

According to this embodiment, there exist the following effects.
The increase from the plan of the current temperature difference TDact, which is the difference between the current saturation temperature in the condenser 5 and the current outlet temperature TWCO of the cooling water heat transfer tube 5a, includes both the contamination in the tube and the retention of non-condensable gas. We focused on the effect being reflected.
On the other hand, the temperature difference increase ΔTDf due to the contamination in the tube can be grasped by a preliminary test or the like in which the cooling water is circulated in the cooling water heat transfer tube 5a.
Therefore, a value obtained by subtracting the temperature difference increase ΔTDf due to the current pipe fouling from the difference between the current temperature difference TDact and the planned temperature difference TDsp can be evaluated as a decrease in condensation performance due to non-condensable gas retention.
Therefore, when the difference between the current temperature difference TDact and the planned temperature difference TDsp is greater than a temperature difference increase ΔTDf due to the current pipe contamination, it is determined that the condensation performance is reduced due to non-condensable gas retention, and the extraction device 40 was activated. As a result, the bleeder 40 can be operated only when a predetermined amount or more of non-condensable gas stays in the condenser 5, thereby realizing a highly efficient turbo chiller 1 that can suppress wasteful energy consumption. it can.

  The dirt in the heat transfer pipe 5a for cooling water is due to the deposits in the heat transfer pipe, and the deposits narrow the flow path in the heat transfer pipe, whereby the differential pressure between the inlet and outlet of the heat transfer pipe 5a for cooling water. PDc rises above the planned value. Therefore, since the pipe dirt temperature difference ΔTDf is determined based on the differential pressure increase ΔPDc, the pipe dirt can be accurately estimated.

  The temperature difference increase ΔTDf due to dirt in the pipe depends on the increase ΔPDc from the planned differential pressure, and the differential pressure PDc depends on the cooling water flow rate GWC. Therefore, the temperature difference in the pipe is determined based on the cooling water flow rate GWC obtained by the cooling water flow rate sensor 22. The increase in temperature difference ΔTDf due to contamination was determined. Thereby, the dirt in the pipe can be accurately estimated.

The present embodiment can be modified as follows.
[Modification 1]
In the present embodiment, the cooling water flow rate GWC is measured by the cooling water flow rate sensor 22, but even when the cooling water flow rate sensor 22 is not provided, the cooling water flow rate GWC can be estimated as follows.

Using the cold water flow rate sensor 32, the cooling water flow rate GWC is obtained from the following equation from the heat balance of the entire turbo refrigerator 1.
GWC = (W + Qact) / ((TWCO−TWCI) × Cpcw × ρcw) (3)
Here, W is the input power [kW] of the electric motor 11 measured by the wattmeter 13. TWCO is the cooling water outlet temperature measured by the cooling water outlet temperature sensor 26, and TWCI is the cooling water inlet temperature measured by the cooling water inlet temperature sensor 24. Cpcw is the specific heat of cooling water [kWh / kg ° C.], and ρcw is the specific gravity of cooling water [kg / m ³ ].
Qact in the formula (3) is an actual measurement value [kW] of the refrigerating capacity, and is expressed by the following formula.
Qact = (TWEI−TWEO) × GWE × cpew × ρew (4)
Here, TWEI is the cold water inlet temperature measured by the cold water inlet temperature sensor 34, and TWEO is the cold water outlet temperature measured by the cold water outlet temperature sensor 36. GWE is the cold water flow rate measured by the cold water flow rate sensor 32, Cpew is the specific heat [kWh / kg ° C.] of cold water, and ρew is the specific gravity [kg / m ³ ] of cold water.

When there is no cooling water flow rate sensor 22 for measuring the cooling water flow rate GWC, the cold water flow rate GWE obtained from the cold water flow rate sensor 32, the cold water inlet / outlet temperature difference (TWEI-TWEO), and the electric power W input to the turbo compressor 3 Then, based on the cooling water inlet / outlet temperature difference (TWCI-TWCO), the cooling water flow rate GWC can be calculated from the heat balance by the above equation (3). Thereby, the cooling water flow sensor 22 can be omitted and the cost can be reduced.
If there is no chilled water flow sensor 32, the chilled water differential pressure ΔPDe measured by the chilled water differential pressure sensor 38 and the loss coefficient ξe of the chilled water heat transfer tube 9a are used to obtain the chilled water as shown in the following equation (5). The flow rate GWE can be calculated.
GWE = ξe × ΔPDe ^1/2 (5)

  In the above-described embodiment, the turbo refrigerator 1 has been described as an example, but the present invention can be applied to any vapor compression refrigerator.

1 Turbo refrigerator (vapor compression refrigerator)
3 Turbo compressor 3a Impeller 3b Rotating shaft 5 Condenser 7 Expansion valve 9 Evaporator 11 Electric motor 13 Power meter 20 Cooling water pump 22 Cooling water flow rate sensor 24 Cooling water inlet temperature sensor 26 Cooling water outlet temperature sensor 28 Cooling water differential pressure Sensor 30 Chilled water pump 32 Chilled water flow rate sensor 34 Chilled water inlet temperature sensor 36 Chilled water outlet temperature sensor 38 Chilled water differential pressure sensor 40 Bleed device 48 Exhaust pump (discharge unit)

Claims (5)

A compressor for compressing the refrigerant;
A condenser for condensing the refrigerant compressed by the compressor;
A cooling water heat transfer tube for circulating cooling water for heat exchange with the refrigerant in the condenser;
An expansion valve for expanding the liquid refrigerant introduced from the condenser;
An evaporator for evaporating the refrigerant expanded by the expansion valve;
A bleeder having a cooling unit for extracting gas from the condenser, cooling the gas and condensing the condensed gas, and a discharge unit for discharging the non-condensable gas separated without being condensed by the cooling unit;
A control unit for controlling the extraction device;
With
The control unit calculates a current temperature difference which is a difference between a current saturation temperature in the condenser and a current outlet temperature of the cooling water heat transfer tube and a planned temperature difference which is a planned value,
Using information on the temperature difference increase due to dirt in the pipe, which is the difference between the saturation temperature in the condenser and the outlet temperature of the cooling water heat transfer pipe, which is determined in advance assuming the dirt in the pipe of the cooling water heat transfer pipe Calculate the temperature difference rise due to dirt in the pipe,
A vapor compression refrigeration machine that operates the extraction device when an increase in the current temperature difference from the planned temperature difference is greater than a predetermined value more than a temperature difference increase due to contamination in the current pipe. A differential pressure sensor for detecting a differential pressure between the inlet and outlet in the condenser of the cooling water heat transfer tube;
2. The vapor compression type according to claim 1, wherein the temperature difference increase due to dirt in the pipe is determined based on an increase from a current differential pressure plan value obtained by the differential pressure sensor. refrigerator. A cooling water flow rate sensor for measuring the flow rate of cooling water flowing in the cooling water heat transfer tube;
The vapor compression refrigerator according to claim 2, wherein the temperature difference increase of the dirt in the pipe is determined based on a flow rate obtained by the cooling water flow sensor. A cold water heat transfer tube for circulating cold water for heat exchange with the refrigerant in the evaporator;
A chilled water flow sensor for measuring the flow rate of chilled water flowing in the heat transfer pipe for chilled water,
The control unit includes: a cold water flow rate obtained from the cold water flow sensor; a cold water inlet / outlet temperature difference of the cold water heat transfer tube in the evaporator; a power input to the compressor; and the cooling water in the condenser. Based on the cooling water inlet / outlet temperature difference of the heat transfer tube, the flow rate of the cooling water flowing in the heat transfer tube for cooling water is calculated from the heat balance,
The vapor compression refrigerator according to claim 2, wherein an increase in temperature difference due to dirt in the pipe is determined based on the cooling water flow rate. A compressor for compressing the refrigerant;
A condenser for condensing the refrigerant compressed by the compressor;
A cooling water heat transfer tube for circulating cooling water for heat exchange with the refrigerant in the condenser;
An expansion valve for expanding the liquid refrigerant introduced from the condenser;
An evaporator for evaporating the refrigerant expanded by the expansion valve;
A bleeder having a cooling unit for extracting gas from the condenser, cooling the gas and condensing the condensed gas, and a discharge unit for discharging the non-condensable gas separated without being condensed by the cooling unit;
A method for controlling a vapor compression refrigerator comprising:
Calculating a current temperature difference that is a difference between a current saturation temperature in the condenser and a current outlet temperature of the cooling water heat transfer tube and a planned temperature difference that is a planned value;
Using the information on the increase in the contamination temperature in the pipe, which is the difference between the saturation temperature in the condenser and the outlet temperature of the cooling water heat transfer pipe, which is determined in advance assuming the contamination in the pipe of the cooling water heat transfer pipe, Calculate the temperature difference rise due to dirt,
Control of a vapor compression refrigeration machine, wherein the extraction device is operated when an increase in the current temperature difference from the planned temperature difference is greater than a predetermined value more than a temperature difference increase due to dirt in the current pipe Method.

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