Heat pump type steam generator

Abstract

To provide a heat pump type steam generating device that can improve a distribution characteristic of a refrigerant for a plurality of compressors arranged in parallel.SOLUTION: A heat pump type steam generating device comprises: an evaporator 6 using heat source water; a compressor group in which compressors 1 and 2 comprising low-stage compressors 1L and 2L and high-stage compressors 1H and 2H are arranged in parallel; a condenser 3 for condensing a high-pressure refrigerant led out of the high-stage compressors 1H and 2H, and heating and evaporating water to be heated; a high-stage expansion valve 4; a gas-liquid separator 7 for separating an intermediate-pressure refrigerant into gas and liquid; intermediate-pressure pipes L11 and L12 for introducing the intermediate-pressure refrigerant introduced from a gas phase side outlet of the gas-liquid separator 7, into connection points P1 and P2 between discharge ports of the low-stage compressors 1L and 2L and suction ports of the high-stage compressors 1H and 2H respectively; a low-stage expansion valve 5; and an accumulator 8 provided between the evaporator 6 and the compressors 1 and 2. The accumulator 8 and refrigerant suction ports of the respective low-stage compressors 1L and 2L are connected by independent pipes L1 and L2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a heat pump type steam generation device capable of improving the distribution characteristics of refrigerant to a plurality of compressors arranged in parallel.

Background Art

[0002] A heat pump type steam generation device includes a heat pump unit and a steam generation unit. In the heat pump unit, a refrigerant circulation circuit is formed by connecting a compressor, a condenser, an expansion valve, and an evaporator in a ring shape. In the evaporator, the refrigerant is evaporated by an external heat source, and in the condenser, the refrigerant is condensed. In the steam generation unit, the water to be heated supplied to the condenser is heated by the refrigerant to generate steam.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the compression-expansion cycle used in the heat pump type steam generation device, in order to increase the steam generation capacity, an increase in the capacity of the compressor is required. An increase in the capacity of the compressor means that the compressor becomes larger. On the other hand, for compressors with limitations in the processing of increasing the size such as scroll compressors, multiple existing compressors may be arranged in parallel. When multiple compressors are arranged in parallel, in order to improve the distribution characteristics of the low-pressure refrigerant discharged from the evaporator to each compressor, an accumulator is usually provided between the evaporator and the refrigerant suction port of each compressor. Here, the accumulator and the refrigerant suction port of each compressor are connected by distributing pipes from a header or the like, and the distribution characteristics of the refrigerant are affected by the header.

[0005] The present invention has been made in view of the above problems, and aims to provide a heat pump type steam generator that can improve the distribution characteristics of refrigerant to multiple compressors arranged in parallel. [Means for solving the problem]

[0006] To solve the above-mentioned problems and achieve the objective, the heat pump type steam generator according to the present invention comprises: an evaporator that evaporates a low-pressure refrigerant using heat source water; a group of compressors connected in parallel, each having a low-stage compressor that compresses the low-pressure refrigerant to an intermediate pressure and a high-stage compressor that compresses the intermediate-pressure refrigerant to a high pressure; a condenser that condenses the high-pressure refrigerant derived from the group of compressors to heat and evaporate the water to be heated; a high-stage expansion mechanism that depressurizes and expands the high-pressure refrigerant condensed by the condenser to the intermediate-pressure refrigerant; and an intermediate The compressor comprises a gas-liquid separator for separating pressurized refrigerant into gas and liquid phases; a plurality of intermediate pipes for introducing the intermediate pressurized refrigerant introduced from the gas phase outlet of the gas-liquid separator between the discharge port of the low-stage compressor and the inlet port of the high-stage compressor of the compressor; a low-stage expansion mechanism for reducing the pressure of the intermediate pressurized refrigerant introduced from the liquid phase outlet of the gas-liquid separator, expanding it to a low pressure, and introducing it into the evaporator; and an accumulator provided between the evaporator and the compressor group, wherein the accumulator and the refrigerant inlets of each low-stage compressor are connected by independent piping.

[0007] Furthermore, the present invention is characterized in that, in the above invention, the plurality of intermediate pipes are a single intermediate pipe, and a buffer tank is provided that commonly connects the refrigerant discharge port of each low-stage compressor, the refrigerant inlet port of each high-stage compressor, and the intermediate pipe.

[0008] Furthermore, the present invention is characterized in that, in the above invention, the intermediate piping connects the refrigerant discharge port of each low-stage compressor and the refrigerant inlet of each high-stage compressor to the gas-liquid separator by independent piping.

[0009] Furthermore, the present invention comprises an evaporator that evaporates a low-pressure refrigerant using heat source water, a group of compressors connected in parallel to each other, a compressor that compresses the low-pressure refrigerant to high pressure, a condenser that condenses the high-pressure refrigerant discharged from the group of compressors to heat and evaporate the water to be heated, an expansion mechanism that depressurizes and expands the high-pressure refrigerant condensed by the condenser and introduces it into the evaporator, a low-stage expansion mechanism that introduces the low-pressure refrigerant introduced from the expansion mechanism into the group of compressors, and an accumulator provided between the evaporator and the group of compressors, wherein the accumulator and the refrigerant inlets of each compressor are connected by independent piping. [Effects of the Invention]

[0010] In this invention, the accumulator and the refrigerant inlet of each low-stage compressor are connected by independent piping, which improves the refrigerant distribution characteristics to multiple compressors arranged in parallel. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a circuit diagram of a heat pump type steam generator according to an embodiment. [Figure 2] Figure 2 is a circuit diagram of a heat pump type steam generator according to Modification 1. [Figure 3] Figure 3 is a circuit diagram of a heat pump type steam generator according to Modification 2. [Figure 4] Figure 4 is a circuit diagram of a heat pump type steam generator according to Modification 3. [Modes for carrying out the invention]

[0012] An embodiment of the heat pump type steam generator according to the present invention will be described in detail below with reference to the drawings. However, this embodiment does not limit the present invention.

[0013] Figure 1 is a circuit diagram of a heat pump type steam generator 10A, which is an embodiment of the present invention. As shown in Figure 1, the heat pump type steam generator 10A comprises a steam generation unit 11 that evaporates water to generate steam and sends it to the outside, and a heat pump unit 10 that recovers heat from heat source water such as waste hot water supplied by a hot water supply unit 12 and supplies this heat as a heat source for steam generation in the steam generation unit 11.

[0014] The heat pump type steam generator 10A is controlled by a control unit (not shown). The control unit may be implemented by, for example, causing a processing unit such as a CPU (Central Processing Unit) to execute a program, i.e., by software; by, by, hardware such as an IC (Integrated Circuit); or by, by, a combination of software and hardware.

[0015] The heat pump unit 10 is a circuit through which the refrigerant circulates, and in the order of refrigerant circulation, it includes an evaporator 6, multiple compressors 1 and 2 (compressor group), a condenser 3, a high-stage expansion valve 4, a gas-liquid separator 7, and a low-stage expansion valve 5. The multiple compressors 1 and 2 are arranged in parallel, and each compressor 1 and 2 consists of low-stage compressors 1L and 2L and high-stage compressors 1H and 2H connected in series. Compressors 1 and 2 are, for example, scroll compressors in which the low-stage compressor and high-stage compressor are integrated. In particular, a single-axis scroll compressor is applicable. The rotational speed of compressors 1 and 2 is controlled by an inverter (not shown) under the operation of the control unit. Compressors 1 and 2 have almost identical functions due to their parallel arrangement.

[0016] Furthermore, an accumulator 8 is positioned between the evaporator 6 and the refrigerant inlets of the respective low-stage compressors 1L and 2L. The accumulator 8 and the refrigerant inlets of the respective low-stage compressors 1L and 2L are connected by independent pipes L1 and L2, respectively. Intermediate pipes L11 and L12 are positioned at connection point P1 between low-stage compressor 1L and high-stage compressor 1H, and at connection point P2 between low-stage compressor 2L and high-stage compressor 2H, respectively. Intermediate pipes L11 and L12 directly and independently connect connection points P1 and P2 to the gas phase space of the gas-liquid separator 7.

[0017] The evaporator 6 superheats and evaporates the low-pressure refrigerant using heat source water such as waste hot water. The superheated gaseous low-pressure refrigerant is discharged to the accumulator 8. The low-pressure refrigerant from the accumulator 8 is directly supplied to the refrigerant inlets of the low-stage compressors 1L and 2L via independent pipes L1 and L2. Therefore, the low-pressure refrigerant is distributed to the low-stage compressors 1L and 2L by the pressure stored in the accumulator 8. Since there is no pressure imbalance due to branching or merging between pipes L1 and L2, the distribution characteristics are good. If this distribution is biased, a pressure difference will occur at the junction of the high-stage compressor 1H and high-stage compressor 2H, resulting in a large loss.

[0018] The heat pump unit 10 forms a two-stage compression-two-stage expansion cycle. The lower-stage compressors 1L and 2L each compress the low-pressure refrigerant to an intermediate pressure and discharge it to the refrigerant outlets and connection points P1 and P2. At connection points P1 and P2, the intermediate-pressure refrigerant is discharged via intermediate pipes L11 and L12, which are connected to the gas phase space of the gas-liquid separator 7. The intermediate-pressure refrigerant from the lower-stage compressors 1L and 2L and the intermediate-pressure refrigerant from the gas-liquid separator 7 are mixed and discharged to the refrigerant suction ports of the upper-stage compressors 1H and 2H, respectively. Here, the intermediate-pressure refrigerant in the gas phase space of the gas-liquid separator 7 independently and directly merges at connection points P1 and P2 via intermediate pipes L11 and L12. Therefore, since there is no pressure imbalance due to branching or merging between intermediate pipes L11 and L12, the distribution characteristics of the intermediate-pressure refrigerant in the gas phase space of the gas-liquid separator 7 to connection points P1 and P2 are good.

[0019] The high-stage compressors 1H and 2H respectively compress the intermediate-pressure refrigerant inhaled from the connection points P1 and P2 to a high pressure. After the compressed refrigerants are merged, the high-pressure refrigerant is led to the condenser 3. The condenser 3 condenses the high-pressure refrigerant led from the high-stage compressors 1H and 2H, heats the heated water, and evaporates it.

[0020] The high-stage expansion valve 4, which is a high-stage expansion mechanism, decompresses and expands the high-pressure refrigerant condensed by the condenser 3 into an intermediate-pressure refrigerant and leads it to the gas-liquid separator 7. The gas-liquid separator 7 separates the introduced intermediate-pressure refrigerant into gas and liquid. The gas-phase intermediate-pressure refrigerant is led to the connection points P1 and P2 via the intermediate pipes L11 and L12. On the other hand, the liquid-phase intermediate-pressure refrigerant is led to the low-stage expansion valve 5, which is a low-stage expansion mechanism. Note that the gas-liquid separator 7 has the function of an accumulator that accumulates the gas-phase intermediate-pressure refrigerant.

[0021] The low-stage expansion valve 5 decompresses and expands the intermediate-pressure refrigerant introduced from the liquid-phase side outlet of the gas-liquid separator 7 to a low pressure and leads the low-pressure refrigerant to the evaporator 6. As a result, the two-stage compression and two-stage expansion cycle is completed. The heat pump unit 10 forms a two-stage compression and two-stage expansion cycle. The lower half in FIG. 1 is the low-stage circuit, and the upper half is the high-stage circuit with the gas-liquid separator 7 and the intermediate pipes L11 and L12 as the boundaries.

[0022] In this embodiment, since the accumulator 8 and the refrigerant inlets of the low-stage compressors 1L and 2L are connected by independent pipes L1 and L2, the distribution characteristics of the refrigerant for the compressors 1 and 2 arranged in parallel can be improved. Also, the intermediate-pressure refrigerant led from the gas-liquid separator 7 to the connection points P1 and P2 via the intermediate pipes L11 and L12 respectively has the intermediate pipes L11 and L12 directly connected to the gas-phase space of the gas-liquid separator 7, and the distribution characteristics of the intermediate-pressure refrigerant in the gas-phase space of the gas-liquid separator 7 can be improved. By improving these distribution characteristics, it is possible to prevent the performance degradation of the entire device and the reliability degradation of the compressors 1 and 2.

[0023] <Modification Example 1> Figure 2 is a circuit diagram of a heat pump type steam generator 10B according to Modification 1 of the embodiment. In the above embodiment, the gas-liquid separator 7 and connection points P1 and P2 were directly connected by independent intermediate pipes L11 and L12, respectively. However, in this Modification 1, as shown in Figure 2, a buffer tank 9 is provided that commonly connects the refrigerant discharge ports of each low-stage compressor 1L and 2L, the refrigerant inlets of each high-stage compressor 1H and 2H, and the connection points P1 and P2 of the intermediate pipes L11 and L12. Furthermore, a single intermediate pipe L13 is used instead of intermediate pipes L11 and L12.

[0024] Unlike the header, the buffer tank 9 forms a single gas-phase mixing space. Specifically, the buffer tank 9 mixes the intermediate-pressure refrigerant introduced from the refrigerant discharge ports of each low-stage compressor 1L and 2L and the intermediate piping L13 in a single gas-phase mixing space, and distributes the intermediate-pressure refrigerant to the refrigerant inlets of each high-stage compressor 1H and 2H. This allows for a more even and improved distribution characteristic of the intermediate-pressure refrigerant to each high-stage compressor 1H and 2H.

[0025] <Modification 2> Figure 3 is a circuit diagram of a heat pump type steam generator 10C according to Modification 2 of the embodiment. In the above embodiment, the gas-liquid separator 7 and connection points P1 and P2 were directly connected by independent intermediate pipes L11 and L12, respectively. However, in this Modification 2, as shown in Figure 3, connection points P1 and P2 are not provided, and the refrigerant discharge ports of each low-stage compressor 1L and 2L and the refrigerant inlets of each high-stage compressor 1H and 2H are directly connected to the orbital space of the gas-liquid separator 7 via independent pipes. This configuration is similar to the configuration in which the gas phase space of the gas-liquid separator 7 and the buffer tank 9 are combined by removing the intermediate pipe L13. As a result, the same intermediate pressure mixing action as when the buffer tank 9 is provided in Modification 2 can be achieved with a simple configuration.

[0026] <Variation 3> Figure 4 is a circuit diagram of a heat pump type steam generator 10D according to Modification 3 of the embodiment. In the above embodiment, the heat pump type steam generator used a two-stage compression / two-stage expansion cycle, but in this Modification 3, the heat pump type steam generator 10D uses a one-stage compression / one-stage expansion cycle.

[0027] As shown in Figure 4, the compressors 1 and 2 are single-stage compressors, and the expansion valve 14, which has an expansion function, is also a single-stage expansion. Here, as with the above embodiment and modified examples 1 and 2, the compressors 1 and 2 are arranged in parallel. In the case of modified example 3, as with the above embodiment and modified examples 1 and 2, an accumulator 8 is provided between the evaporator 6 and the compressors 1 and 2, and the accumulator 8 is directly connected to the refrigerant inlets of each compressor 1 and 2 by independent piping L1 and L2. This improves the distribution characteristics of the refrigerant to the multiple compressors 1 and 2 arranged in parallel.

[0028] The present invention is not limited to the embodiments and modifications described above, and can be freely modified without departing from the spirit of the invention. [Explanation of Symbols]

[0029] 1,2 Compressor 1L,2L low stage compressor 1H, 2H High-stage compressor 3. Condenser 4. High-stage expansion valve (high-stage expansion mechanism) 5. Low-stage expansion valve (low-stage expansion mechanism) 6. Evaporator 7 Gas-liquid separator 8. Accumulator 9 Buffer Tank 10 Heat pump section 10A, 10B, 10C, 10D Heat pump type steam generator 11 Steam generation section 12 Hot water supply section 14. Expansion valve L1, L2 piping L11, L12, L13 Intermediate piping P1, P2 connection point

Claims

1. An evaporator that uses water as a heat source to evaporate a low-pressure refrigerant, A group of compressors, each having a low-stage compressor for compressing the low-pressure refrigerant to an intermediate pressure and a high-stage compressor for compressing the intermediate-pressure refrigerant to a high pressure, are connected in parallel. A condenser that condenses the high-pressure refrigerant discharged from the aforementioned group of compressors and heats the water to be heated to evaporate it, A high-stage expansion mechanism that reduces the pressure and expands the high-pressure refrigerant condensed by the condenser to produce the intermediate-pressure refrigerant, A gas-liquid separator for separating the intermediate pressure refrigerant introduced from the aforementioned high-stage expansion mechanism into gas-liquid and gas-liquid components, An intermediate pipe introduces the intermediate pressure refrigerant, which has been introduced from the gas phase side outlet of the gas-liquid separator, between the discharge port of the low-stage compressor and the inlet port of the high-stage compressor of the compressor. A low-stage expansion mechanism that reduces the pressure of the intermediate-pressure refrigerant introduced from the liquid-phase outlet of the gas-liquid separator to a low pressure by depressurizing and expanding it, and then introduces it into the evaporator, An accumulator provided between the evaporator and the compressor group, Equipped with, The aforementioned intermediate piping is one in number. A heat pump type steam generator characterized by having a buffer tank that commonly connects the refrigerant discharge port of each low-stage compressor, the refrigerant inlet of each high-stage compressor, and the intermediate piping.

2. The heat pump type steam generating apparatus according to claim 1, characterized in that the accumulator and the refrigerant inlet of each low-stage compressor are connected by independent piping.

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