JP2003065618A - Heat carrying equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide heat carrying equipment which suppress lowering of the efficiency of a heat exchanger. SOLUTION: The heat carrying equipment has a closed-loop circulation circuit which connects a rotation speed variable type liquid pump 1, an evaporator 3 and the heat exchanger 7 sequentially and is filled with a refrigerant. The equipment is provided with detecting means 31 and 33 for detecting a supercooling degree at an inlet of the liquid pump 1 and a control means 41 for controlling the speed of rotation of the liquid pump 1 according to the supercooling degree detected by these detecting means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer device suitable for use in, for example, commercial freezers and showcases.

[0002]

2. Description of the Related Art Generally, a heat transfer device is known which is provided with a closed loop circulation circuit in which a liquid pump, an evaporator, and a heat exchanger are connected in order and filled with a refrigerant. In this type, in recent years, there has been proposed one in which a high-pressure working refrigerant such as CO ₂ or HFC is enclosed in the circulation circuit. For example, if the CO ₂ refrigerant is filled in the circulation circuit, since the CO ₂ refrigerant has a low viscosity, it is possible to pressure loss is small, a longer pipe length of the circulation circuit, CO ₂ refrigerant in the low-temperature region Since the latent heat is high, there are advantages such as that the circulation amount of the refrigerant can be reduced.

[0003]

By the way, in the conventional structure, when the degree of supercooling at the inlet of the liquid pump exceeds a predetermined value, the liquid refrigerant stays in the heat exchanger connected to the inlet of the liquid pump, and that much However, there is a problem that the area required for heat exchange is reduced and the efficiency of the heat exchanger is reduced.

On the other hand, if the degree of supercooling at the inlet of the liquid pump becomes too low, there is a problem that bubbles are generated and cavitation occurs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a heat transfer device capable of suppressing a decrease in efficiency of the heat exchanger and suppressing the occurrence of cavitation. is there.

[0006]

In order to achieve the above object, the invention according to claim 1 is a closed loop in which a variable rotation speed type liquid pump, an evaporator and a heat exchanger are connected in order and a refrigerant is filled. In the heat transfer device including the circulation circuit, a detection unit that detects the degree of supercooling at the inlet of the liquid pump, and a control unit that controls the rotation speed of the liquid pump according to the degree of supercooling detected by the detection unit. It is characterized by having and.

According to a second aspect of the present invention, there is provided a heat transfer device including a closed-loop circulation circuit in which a constant-speed liquid pump, an evaporator, and a heat exchanger are connected in sequence and a refrigerant is filled. A flow rate adjusting valve provided in a pipe bypassing the pump, a detecting means for detecting the degree of supercooling at the inlet of the liquid pump, and a valve of the flow rate adjusting valve according to the degree of supercooling detected by the detecting means. A control means for controlling the opening is provided.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the above described, the refrigerant filled in the circulation circuit is a high pressure working refrigerant such as CO ₂ or HFC.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of the heat transfer device. Figure 1
In the figure, 1 indicates a rotary type totally enclosed liquid pump. The liquid pump 1 is a variable speed pump of an inverter drive system. On the discharge side of the liquid pump 1, a plurality of evaporators 3 such as a showcase are connected in parallel via a liquid pipe 2. Reference numeral 4 is a flow rate adjusting valve for adjusting the amount of refrigerant flowing into each evaporator 3.

Each evaporator 3 has a heat exchanger 7 through a gas pipe 6.
The heat exchanger 7 is connected to the suction side of the liquid pump 1.

The heat exchanger 7 is, so to speak, a refrigerant-to-refrigerant heat exchanger for exchanging heat between the refrigerants, and the condensing section 7
It has A and the evaporation part 7B.

The condensing section 7A is composed of a pipe line connected to the liquid pump 1, and the refrigeration cycle 9 is connected to the pipe line of the evaporation section 7B.

The refrigeration cycle 9 is constructed by connecting a compressor 11, a condenser 13, a decompression device 15 and an evaporation section 7B by piping.

Next, the operation of this heat transfer device will be described.

The refrigeration cycle 9 operates by driving the compressor 11. When the compressor 11 is driven, the refrigerant circulates in the closed loop in the direction of the arrow P, and the refrigerant condensed in the condenser 13 is evaporated in the evaporator 7B of the refrigerant / refrigerant / heat exchanger 7. On the other hand, the heat transfer device operates by driving the liquid pump 1. When the liquid pump 1 is driven, the refrigerant circulates in the closed loop in the direction of the arrow Q, is evaporated by the evaporator 3, and the inside of the showcase is cooled. Next, the refrigerant flows into the refrigerant / refrigerant / heat exchanger 7, is condensed and liquefied in the condensing portion 7A of the refrigerant / refrigerant / heat exchanger 7, and is sucked into the liquid pump 1. The liquid pump 1 sucks a refrigerant as a liquid and discharges it as a liquid.

A CO ₂ refrigerant is enclosed in the closed loop of the heat transfer device. Since this CO ₂ refrigerant has a low viscosity, the pressure loss is small and the piping length of the circulation circuit can be lengthened. Therefore, this configuration is suitable for a heat transfer device for a large store such as a supermarket to which a commercial freezer or a plurality of showcases are connected.

Further, since the CO ₂ refrigerant has a high latent heat in a low temperature range, the circulation amount of the refrigerant can be reduced. Since the circulation amount can be reduced, the pressure loss can be reduced and the pipe length can be increased (the pipe diameter can be reduced). Furthermore, since the CO ₂ refrigerant has an ozone depletion potential of 0 and a global warming potential of 1, it is less toxic, non-flammable, safe and inexpensive.
Provided is a heat transfer device having a low environmental load.

FIG. 2 shows the liquid pump 1. The liquid pump 1 includes an electric motor unit 22 including a stator 22A and a rotor 22B inside a shell case 21, and two pump units 23 and 24 arranged in parallel in the vertical direction, which are driven by being connected to a lower portion of the electric motor unit 22. And is configured. The pump units 23 and 24 compress the liquid refrigerant sucked from the suction units 23A and 24A, and discharge the liquid refrigerant from the discharge units 23B and 24B to the evaporator 3 side. The suction portions 23A and 24A of the pump portions 23 and 24 are the condensing portion 7A of the heat exchanger 7.
Connected to.

FIG. 3 shows the power consumption k per unit time when the liquid pump 1 is operated with the subcooling degree (subcool) SC at the inlet of the liquid pump 1 and the discharge flow rate Q as parameters.
The experimental result which measured W is shown.

According to this result, when the discharge flow rate Q of the liquid pump 1 changes, the power consumption kW of the liquid pump 1 does not change significantly, although there is a smooth change according to the change of the outside air temperature. However, when the supercooling degree SC becomes high, the power consumption kW of the liquid pump 1 obviously increases.

Referring to FIG. 2, when the supercooling degree SC at the inlet of the liquid pump 1 becomes high, the refrigerant liquid level A in the heat exchanger 7 rises, so that the actual heat transfer area of the heat exchanger 7 is increased. B is reduced and heat exchange efficiency is reduced.

In this embodiment, in order to suppress a decrease in heat exchange efficiency of the heat exchanger 7, the supercooling degree S at the inlet of the liquid pump 1 is suppressed.
When C becomes high, the number of rotations of the liquid pump 1 is increased,
The discharge flow rate Q of the liquid pump 1 is increased.

If the discharge flow rate Q increases, the heat exchanger 7
The liquid refrigerant inside is discharged to the liquid pump 1 side, and the refrigerant liquid level A
Is decreased, the actual heat transfer area B of the heat exchanger 7 is increased, and the heat exchange efficiency can be improved.

Specifically, as shown in FIG. 2, a temperature sensor 31 for detecting the refrigerant temperature at the inlet of the liquid pump 1 and a pressure sensor 33 for detecting the refrigerant pressure at the inlet of the liquid pump 1 are provided. These are connected to the control means 41. In the control means 41, the degree of supercooling SC is calculated, and when the degree of supercooling SC exceeds a predetermined value, a rotation speed increase command is output to the inverter liquid pump 1.

Here, the degree of supercooling SC is obtained by calculating the saturation temperature from the refrigerant pressure and calculating the deviation between the saturation temperature and the measured refrigerant temperature.

In this embodiment, when the supercooling degree SC at the inlet of the liquid pump 1 becomes high, the number of rotations of the liquid pump 1 is increased and the discharge flow rate Q of the liquid pump 1 is increased. It is possible to suppress the decrease in heat exchange efficiency.

With reference to FIG. 3, the discharge flow rate Q of the liquid pump 1
It has been found that the power consumption kW of the liquid pump 1 does not change significantly even when the power consumption increases.

Therefore, in this embodiment, it is possible to suppress a decrease in the heat exchange efficiency of the heat exchanger 7 without increasing the power consumption kW.

On the other hand, when the supercooling degree SC at the inlet of the liquid pump 1 becomes low, bubbles are generated and cavitation occurs. In this case, in the present embodiment, the rotation speed of the liquid pump 1 is reduced. Then, since the discharge flow rate Q of the liquid pump 1 is reduced, the generation of bubbles is eliminated and the generation of cavitation is eliminated.

Next, another embodiment will be described.

In the present embodiment, the refrigerant charging amount of CO ₂ in the closed loop is set to be small so that the supercooling degree SC at the inlet of the liquid pump 1 does not become high.

In the present embodiment, a constant rotation speed type liquid pump is used as the liquid pump 1, and as shown in FIG. 1, a pipe line 5 that bypasses the liquid pump 1 is provided. 5 is provided with a flow rate adjusting valve 8.

In this embodiment, as described above, CO ₂
Since the filling amount is set to a small value, the subcooling degree SC at the inlet of the liquid pump 1 does not increase when the liquid pump 1 is operated. On the other hand, the supercooling degree S at the inlet of the liquid pump 1
C becomes low, bubbles are generated, and the occurrence rate of cavitation becomes high.

Therefore, the supercooling degree SC at the inlet of the liquid pump 1
When becomes low, the valve opening of the flow rate adjusting valve 8 is increased. Alternatively, the fully closed flow rate adjusting valve 8 is controlled to be fully opened. When the valve opening degree increases, the refrigerant discharged from the liquid pump 1 is returned to the suction side of the liquid pump 1 through the conduit 5.

Therefore, bubbles are not generated on the suction side of the liquid pump 1, and cavitation can be suppressed.

Although the present invention has been described based on the embodiment, the present invention is not limited to this.

[0038]

According to the present invention, the detecting means for detecting the degree of supercooling at the inlet of the liquid pump and the controlling means for controlling the number of revolutions of the liquid pump according to the degree of supercooling detected by the detecting means are provided. Therefore, it is possible to suppress a decrease in the efficiency of the heat exchanger and suppress the occurrence of cavitation.

According to the present invention, the flow rate adjusting valve provided in the conduit bypassing the liquid pump, the detecting means for detecting the degree of supercooling at the inlet of the liquid pump, and the means for detecting the degree of supercooling detected by the detecting means are used. Since the control means for controlling the valve opening of the flow rate adjusting valve is provided, the occurrence of cavitation can be suppressed.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a heat transfer device according to the present invention.

FIG. 2 is a diagram showing an embodiment of a liquid pump.

FIG. 3 is a diagram showing an experimental result in which a power consumption KW per unit time is measured when the liquid pump is operated by using the supercooling degree SC at the inlet of the liquid pump and the discharge flow rate Q as parameters.

[Explanation of symbols]

1-liquid pump 3 evaporator 7 heat exchanger 11 compressor 13 condenser 15 Pressure reducing device 31 Temperature sensor 33 Pressure sensor 41 Control means

Claims (3)

[Claims] 1. A heat transfer device comprising a closed-loop circulation circuit in which a variable-speed liquid pump, an evaporator, and a heat exchanger are connected in order, and a closed loop circulation circuit is filled with a refrigerant. A heat transfer device comprising: a detection unit that detects the temperature of the liquid pump; and a control unit that controls the rotation speed of the liquid pump according to the degree of supercooling detected by the detection unit. 2. A heat transfer device comprising a closed-loop circulation circuit in which a constant-rotation type liquid pump, an evaporator and a heat exchanger are connected in sequence, and a closed loop circulating circuit is filled with a refrigerant. A flow rate adjusting valve, a detecting means for detecting the degree of supercooling at the inlet of the liquid pump, and a control for controlling the valve opening of the flow rate adjusting valve according to the degree of supercooling detected by the detecting means. And a heat transfer device. 3. The refrigerant filled in the circulation circuit is CO ₂
Alternatively, the heat transfer device according to claim 1 or 2, which is a high pressure working refrigerant such as HFC.