Refrigeration Cycle Apparatus

The present disclosure relates to a refrigeration cycle apparatus having a refrigerant circuit, such as a heat pump chiller, and particularly relates to an attachment structure of a fusible plug in the refrigerant circuit.

In a refrigeration cycle apparatus such as a heat pump chiller, as means for protecting a refrigerant circuit from an excessive pressure increase, conventional techniques have been established, such as protection with a pressure switch, software protection using values detected by a pressure sensor, and protection by a controller instead of using the pressure switch and the pressure sensor.

However, for example, in the United States, devices having a pressure container in a refrigerant circuit, such as an air-conditioning device, a chiller device, and a water heating device, are required to be provided with a physical device designed to release refrigerant safely, such as a fusible plug or a safety valve, based on the safety standards, UL60335-2-40. The conventionally-used pressure switch, pressure sensor, and pressure control are not adequate enough to comply with UL60335-2-40. It is thus necessary to provide a pressure relief device such as a fusible plug (that is, a safety device). Patent Literature 1 discloses a safety device for a refrigerating machine. The safety device includes a fusible plug. The fusible plug is a device to detect a temperature and release refrigerant.

In a refrigeration cycle apparatus, there is a case where the refrigerant circuit uses the fusible plug. In that case, since the fusible plug is a device to detect a temperature and release refrigerant, a worker needs to work with great care to prevent the fusible plug from improperly operating during the servicing such as maintenance and regular inspection, or during the device assembly. The refrigeration cycle apparatus (refrigerating machine) in Patent Literature 1 has a problem that the fusible plug located on the rearward side in a main-body casing makes it difficult for a worker to work on or check the fusible plug during the servicing and other process, resulting in a decrease in work efficiency.

The present disclosure has been made in view of the above problems, and it is an object of the present disclosure to provide a refrigeration cycle apparatus including a fusible plug to result in an improvement in work efficiency during its servicing and other process.

A refrigeration cycle apparatus according to an embodiment of the present disclosure is a refrigeration cycle apparatus having a housing in which at least a portion of a refrigerant circuit through which refrigerant circulates is located, the housing forming an outer shell and having a front side portion, the front side portion being removable, wherein the at least portion of the refrigerant circuit includes a condenser, a pressure container in which the refrigerant is reserved, a first pipe through which the refrigerant flows, the first pipe connecting the condenser and the pressure container, and a pressure relief device having a fusible plug, provided on the first pipe, and configured to release the refrigerant when a pressure in the first pipe reaches a predetermined pressure, and a portion of the first pipe, on which the pressure relief device is provided, is located beside the front side portion in the housing.

According to the embodiment of the present disclosure, it is possible in the refrigeration cycle apparatus including the fusible plug to result in an improvement in work efficiency during its servicing and other process.

Hereinafter, an embodiment of a refrigeration cycle apparatus according to the present disclosure when it is applied to a heat pump chiller (hereinafter, referred to as a “chiller unit”) will be described with reference to the drawings. The present disclosure is not limited to the embodiment described below, and can be variously modified without departing from the gist of the present disclosure. In addition, the present disclosure includes all combinations of configurations that can be combined among the configurations shown in the embodiment described below. In particular, the combination of constituent elements is not limited to only the combination in each embodiment, and the constituent elements described in one embodiment can be applied to another embodiment. The refrigeration cycle apparatus is illustrated in the drawings merely as an example of a device to which the refrigeration cycle apparatus of the present disclosure is applied. The refrigeration cycle apparatus illustrated in the drawings does not intend to limit the devices to which the present disclosure is applied. The refrigeration cycle apparatus may be an air-conditioning apparatus, a water heating device, a refrigerator, or a freezer. In the descriptions below, terms that represent directions (for example, “up,” “down,” “right,” “left,” “front,” and “rear”) are appropriately used for the sake of easy understanding. However, these terms are used merely for description purposes, and are not intended to limit the present disclosure. In the drawings below, the same reference signs denote the same or equivalent components, which are common throughout the entire specification. Note that the relative relationship of sizes of the constituent components, the shapes of the constituent components, and the like in the drawings may differ from those of actual ones.

is a circuit configuration diagram of a heat pump chiller systemincluding a refrigeration cycle apparatus (the chiller unit) according to Embodiment 1. In, the heat pump chiller systemguides cooled water or heated water from the chiller unitto a load side to perform cooling or heating. The heat pump chiller systemincludes a refrigerant circuitusing flammable refrigerant such as hydrocarbon. Note that it is allowable that the refrigerant circuituses other type of refrigerant than the flammable refrigerant. The heat pump chiller systemincludes a water circuitthrough which a heat medium such as water circulates.

In, the refrigerant circuithas a compressorconfigured to compress and discharge refrigerant, a condenserconfigured to allow the refrigerant discharged from the compressorto exchange heat with water in the water circuit, an expansion valveconfigured to reduce the pressure of refrigerant on the downstream side of the condenser, and an evaporatorconfigured to allow the refrigerant whose pressure has been reduced to evaporate. These elements are connected annularly by a pipe. The condenseris, for example, a water heat exchanger such as a plate heat exchanger. The evaporatoris an air heat exchanger configured to allow refrigerant to exchange heat with air (outside air), and is for example a fin-and-tube heat exchanger. In the refrigerant circuit, a pressure containerand a pressure relief devicehaving a fusible plugare provided.

The pressure containeris provided on a pipe connecting a refrigerant outlet on the condenserand a refrigerant inlet on the evaporatorin the refrigerant circuit. In, the pressure containeris provided on the pipe extending between the condenserand the expansion valve. Note that the pressure containermay be provided on the pipe extending between the expansion valveand the evaporator. The pressure containeris configured to temporarily reserve refrigerant in the refrigerant circuit.

There is the pressure relief deviceon a liquid-refrigerant pipe portion in the refrigerant circuit, where liquid refrigerant flows. In, the pressure relief deviceis provided on a pipeextending between the condenserand the pressure containerin the refrigerant circuit. Hereinafter, the pipeconnecting the condenserand the pressure containermay sometimes be referred to as a “first pipe.”

The pressure relief deviceis set to operate when the pressure in the refrigerant circuitreaches a predetermined pressure. The pressure relief deviceis configured to allow the refrigerant to leak when an anomaly has occurred and then the refrigerant pressure in the refrigerant circuitincreases to the predetermined pressure. When the pressure in the refrigerant circuitreaches the predetermined pressure, the refrigerant is released from the pressure relief devicewhere the refrigerant is most likely to leak in the refrigerant circuit. The pressure relief devicereleases the refrigerant to release the pressure in the refrigerant circuit, thereby serving as a protection device (safety device) for a part of the circuit other than the pressure relief device.

The pressure relief devicehas the fusible plugand a branch pipethat branches off from a main pipe (the pipe) of the refrigerant circuit. In general, a fusible plug includes a fuse element (fusible alloy) that seals a container filled with gas and melts at a certain temperature. When the temperature in the container increases excessively, the fuse element melts, through which the gas is released, thereby to prevent the container from being broken.

In this example, in order that the fusible plugoperates when the refrigerant pressure in the pipeprovided with the pressure relief devicereaches a specified pressure in the refrigerant circuit, a fuse element appropriate to the specified pressure is used. With this configuration, when the refrigerant pressure in the refrigerant circuitincreases to a predetermined pressure, that is, the refrigerant pressure in the pipereaches the specified pressure, then the refrigerant is released from the fusible plug. Since the refrigerant is released from the fusible plugwhere the refrigerant is most likely to be released in the refrigerant circuit, it is possible to cause the refrigerant to leak at a fixed position in the refrigerant circuit.

The specified pressure described above is determined depending on the pressure resistance, for example, depending on the configuration of the refrigerant circuit, the type of refrigerant to be used, and the maximum pressure in the refrigerant circuitduring operation. The fusible plugis provided in such a manner as to satisfy, for example, the US safety standards, UL60335-2-40 Edition 3 22.112DV.9.

is an external perspective view of the refrigeration cycle apparatus according to Embodiment 1.is a schematic diagram illustrating a positional relationship between the fusible plugand the pressure containerinside a housing(see) of the refrigeration cycle apparatus according to Embodiment 1. The solid arrow illustrated inshows a refrigerant flow direction.is a plan view illustrating an internal configuration of the refrigeration cycle apparatus according to Embodiment 1.

As illustrated in, the refrigeration cycle apparatus (the chiller unit) has the housingforming the outer shell. On one of the sides of the housing, a maintenance side is provided. The maintenance side is a removable panel that can be removed to open a portion of the housingfor a worker to repair or check the parts inside the housingduring the servicing such as maintenance and regular inspection or during the device assembly. Hereinafter, a front side portionof the housingis defined as the maintenance side, and directional terms (for example, “up,” “down,” “right,” “left,” “front,” and “rear”) are supposed to represent directions when the chiller unitis viewed from the front side on which the maintenance side is provided.

The housingis formed in a hollow cuboid shape, and has a top side portion, a bottom side portion, a right side portion, a left side portion, a back side portion, and the front side portionthat is removable as the maintenance side.

The chiller unithas a configuration in which the above refrigerant circuitis accommodated in the housing. An air outlet is formed on the top side portion. A fanis located at the air outlet. Air inlets are formed on the right side portion, the back side portion, and the left side portionof the housing. As illustrated in, the evaporatoris located on the inner side of the right side portion, the back side portion, and the left side portion.

Note that the refrigeration cycle apparatus of the present disclosure does not necessarily have all the elements of the refrigerant circuit. It suffices that the refrigeration cycle apparatus has at least some of the elements of the refrigerant circuit(including the condenser, the pressure container, the pipeconnecting the condenserand the pressure container, and the pressure relief deviceprovided on the pipe). The refrigeration cycle apparatus may be, for example, an outdoor unit of an air-conditioning device.

The US safety standards, UL60335-2-40, impose several restrictions on the location of the pressure relief device. In the UL60335-2-40, for example, Edition 3 22.112DV.11 stipulates that “All the pressure relief means shall be connected adjacent to, or connected directly to, a pressure container or a portion of the system to be protected. The pressure relief device shall be connected at a position higher than the liquid refrigerant level, and be installed in an easily accessible manner for inspection and repair, and in such a manner as to protect from conditions that may possibly cause improper operation.”

As illustrated in, the fusible plugis located higher than the pressure containerin the housing. As also illustrated in, the pressure relief deviceis provided on the pipeextending between the condenserand the pressure containerin the refrigerant circuit. In, in the manner as described above, the pressure relief devicesatisfies the stipulations described above, and thus complies with the UL60335-2-40.

In, the condenserand the pressure containerare installed on the bottom side portionof the housing. The fusible plugis located on the pipeextending between the condenserand the pressure containernear the condenserwhose height is greater of the condenserand the pressure container. In, the pipeextending between the condenserand the pressure containerincludes a first pipe portionextending in a horizontal direction from the refrigerant outlet on the condenser, a second pipe portionextending in the horizontal direction from the refrigerant inlet on the pressure containerand located at a position lower than the first pipe portion(that is, near the bottom side portion), and a connection pipe portionconnecting the first pipe portionand the second pipe portion. The pipeis formed in substantially a Z-shape.

As illustrated in, a portion of the pipeextending between the condenserand the pressure containeris located beside the front side portionof the housing, and the fusible plugis located in close proximity to the front side portion. In, the condenserand the compressorare located on the forward side in the housing, while the pressure containeris located in the rear of the compressor. Due to this arrangement, in, in the pipeextending between the condenserand the pressure container, the first pipe portionnear the condenseris located on the forward side relative to the second pipe portionnear the pressure container, such that the first pipe portionruns along the front side portionof the housing. The fusible plugis attached to the first pipe portionthrough the branch pipe.

Specifically, in the pressure relief devicein, the branch pipestraightly extending upward is provided on the upper side of the first pipe portionin the pipe, and the fusible plugis provided at an upper end of the branch pipe. The branch pipeprovided in this manner allows the fusible plugto be located at a relatively high position in the housing.

Note that the pressure relief devicemay have a configuration in which the fusible plugis directly attached to the pipeextending between the condenserand the pressure container, however, it is structurally desirable to have a configuration in which the fusible plugis attached to the pipethrough the branch pipe, such that a direction in which or the position to which refrigerant is released is easily adjusted.

illustrates a configuration example of the fusible plugin the refrigeration cycle apparatus according to Embodiment 1. As illustrated in, the fusible plugincludes a plug attachment portionto be attached to the branch pipe(or to the pipewhen the fusible plugis directly installed on the pipe), and an outlet portionfrom which refrigerant is released. In the fusible plug, a holeis formed connecting the refrigerant inlet on the plug attachment portionand the refrigerant outlet on the outlet portion. The holeis normally closed by the fuse element (not illustrated).

With reference to, operation of the heat pump chiller systemis now described. In the refrigerant circuitof the heat pump chiller system, gas refrigerant heated to a high temperature and compressed to a high pressure by the compressorenters a refrigerant pipe (not illustrated) in the condenser, and exchanges heat with water flowing in the water circuitand passing through a water pipe (not illustrated) in the condenser. The water is heated in the condenser, while the refrigerant having transferred heat to the water flows out from the condenser, reaches the expansion valve, is reduced in pressure by the expansion valve, and then enters the evaporator. The refrigerant having entered the evaporatorreceives heat from outside air delivered by the fan(see), is then evaporated and gasified in the evaporator, and thereafter returns to the compressor. A controller (not illustrated) controls an actuator of the refrigerant circuitin response to the water temperature in the water circuit.

When the heat pump chiller systemis affected by some external factors, for example, when the ambient temperature excessively increases, the refrigerant pressure in the refrigerant circuitincreases, which may possibly cause cracks on the pipe and other constituent elements of the refrigerant circuit. If the cracks appear, flammable refrigerant in the refrigerant circuitleaks to the outside through the cracks. In the present embodiment, when the refrigerant pressure in the refrigerant circuitincreases, and thus there is a possibility that cracks may appear on the pipe and other constituent elements of the refrigerant circuit, that is, when the pressure in the refrigerant circuitincreases and the refrigerant pressure in the pipereaches a specified pressure, then the pressure relief deviceoperates, so that the refrigerant is released from the pressure relief devicewhere the refrigerant is most likely to be released in the refrigerant circuit. More specifically, as the pressure in the refrigerant circuitincreases anomalously, the temperature accordingly increases. Consequently, the fuse element (not illustrated) of the fusible plugillustrated inmelts and thus the holeis opened, from which refrigerant is released to the outside, so that the internal pressure of the refrigerant circuitis released to the outside.

In the configuration example in, the fusible plughas an outer circumferential portionprovided with a male thread. Specifically, thread cutting has been done on the outer circumferential portion of the outlet portion. In this manner, the fusible plugis threaded (male-threaded) on the outer circumferential portion, which allows, for example, a refrigerant recovery device (not illustrated) configured to recover refrigerant to be directly connected to the fusible plug.

Therefore, it is possible to connect the refrigerant recovery device (not illustrated) to the fusible plugduring, for example, assembly of the device to be filled with refrigerant, or inspection during which the refrigeration cycle apparatus may operate in different mode from the normal mode. Accordingly, even if the fusible plugoperates improperly, causing the refrigerant to be discharged, it is still possible to avoid the refrigerant from scattering to the peripheral devices around the fusible plug. This allows the peripheral devices to be protected from the refrigerant, and results in an improvement in the work efficiency. As illustrated in, in the housing, the fusible plugis located beside the maintenance side (the front side portion), so that even when the refrigerant recovery device or other device is temporarily connected to the fusible plugduring the device assembly or inspection, a work space can still be easily ensured.

There is a case where in the housing, flammable elements (for example, a structure made of resin) are provided in proximity to the pipeon which the pressure relief deviceis provided. In that case, it is desirable that the position to which or the direction in which refrigerant is released from the fusible plugcan be adjusted in such a manner as to prevent these flammable elements from contacting the refrigerant. Examples of the flammable elements include a covered wire and a control device. In, the pipeand the fusible plugare connected through the branch pipeextending upward, so that it is possible to adjust the position of the fusible plug(particularly, the refrigerant outlet) in its height direction.

Note that the shape, the orientation, and the length of the branch pipeare not limited to the shape, the orientation, and the length described above. It is also allowable to determine the shape, the orientation, and the length of the branch pipedepending on the positional relationship with the structures in the chiller unitin which the pressure relief deviceis installed. Two modifications of the pressure relief deviceare described below.

is a front view of a pressure relief deviceand the pipeon which the pressure relief deviceis provided, illustrating a first modification of the pressure relief devicein.is a cross-sectional view of the pressure relief deviceand the pipetaken along the A-A line in. As illustrated in, in the first modification, a branch pipeis provided to be bent in such a manner that a tip of the fusible plug, from which refrigerant is discharged, is directed not toward the flammable elements.

As illustrated in, the branch pipeis formed in an L-shape. The branch pipeincludes a first straight pipe portionextending parallel to the pipe, a second straight pipe portionconnected to the pipeperpendicularly to the pipe, and a curved portionconnecting the first straight pipe portionand the second straight pipe portion. At a tip end portion of the branch pipe(that is, a tip end portion of the first straight pipe portion), an attachment portionis provided to which the fusible plugis attached. The plug attachment portion(see) of the fusible plugis positioned on the inner circumferential side of the attachment portion

In, the first straight pipe portionextends parallel to the pipeas described above. That is, the branch pipeis bent toward the same direction as the refrigerant flow direction in the pipewhich is the main pipe of the refrigerant circuit. With this configuration, it is possible for the fusible plugto detect the temperature of refrigerant accurately. That is, even when the length of the branch pipeneeds to be increased by the amount of bending the branch pipe, it is still possible to locate the fusible plugclose to the pipe. As a result, the fuse element is affected sufficiently by the temperature increase due to the pressure increase, and then melts properly, so that the pressure relief devicefunctions normally.

In a case where the branch pipeof the pressure relief deviceincludes the curved portion, it is possible to adjust the orientation of the fusible plugin such a manner that its tip from which refrigerant is discharged is directed not toward the flammable elements as described above. While these effects are still achieved even in a case where refrigerant is non-flammable, particularly in a case where refrigerant is flammable, these effects result in an improvement in safety, which is effective.

is a front view of a pressure relief device, illustrating a second modification of the pressure relief devicein. As illustrated in, in the second modification, a capillary tube (with a length of, for example, approximately several tens of centimeters) is used as a connection pipe (that is, a branch pipe) connecting the fusible plugand the pipeon which the pressure relief deviceis provided. The fusible plugis connected to the pipethrough the capillary tube.

In, the branch pipeincludes an annular portionformed into an annular shape, a branch pipe base portionextending straightly from one end of the annular portion, and a branch pipe tip end portionextending straightly from the other end of the annular portion. The branch pipe base portionis connected to the pipe. The fusible plugis attached to the branch pipe tip end portion

In, at locations of the annular portionthat are opposite to each other (on the upper side and the lower side of the annular portionillustrated in), one end and the other end thereof are provided, and opened toward the same direction (on the right side in). The branch pipe base portionand the branch pipe tip end portionboth extend in the same direction along their respective tangents to the annular portion

Note that the positional relationship between one end and the other end of the annular portion, and the shape and the extending direction of the branch pipe base portionand the branch pipe tip end portionare not limited to those described above, and may be appropriately set such that refrigerant is released in a desired direction or to a desired position. As illustrated in, using the capillary tube to serve as the branch pipeof the pressure relief devicemakes it possible to easily set the direction in which or the position to which refrigerant is released.

Whileillustrates the case where the pressure relief device(particularly, the branch pipe) is connected to the upper side of the pipe, it is allowable that the pressure relief device,, or(the branch pipe,, or) is connected to any location on the pipe.

is a circuit configuration diagram illustrating another configuration example of the heat pump chiller systemin. The chiller unitillustrated inincludes a high-pressure switchas an additional safety device separate from the pressure relief device. The high-pressure switchis configured to operate when the high-pressure side pressure in the refrigerant circuitreaches an upper limit. The high-pressure switchmay be either an electrical switch or a mechanical switch using a diaphragm. The high-pressure switchis provided on a pipeextending between the compressorand the condenserin the refrigerant circuit. Hereinafter, the pipeconnecting the compressorand the condensermay sometimes be referred to as a “second pipe.”

In the heat pump chiller systemillustrated in, the high-pressure switchand the pressure relief deviceare provided in the refrigerant circuit. As illustrated in, the capillary tube is used to serve as the branch pipeof the pressure relief device, which allows a pipe length from the pipeto the fusible plugto be increased relative to a distance between the pipeand the fusible plug. Accordingly, it is possible to decrease the temperature of refrigerant by the time the refrigerant reaches the fusible plug.

Therefore, when the refrigerant circuitis, for example, under the condition of adequate pressure despite high temperature, and thus the pressure relief device(the fusible plug) does not need to be operated, then the high-pressure switchthat needs to be operated prior to the fusible plugcan be operated with a priority over the fusible plug. This can prevent the fusible plugfrom being improperly operated.

As described above, the refrigeration cycle apparatus according to Embodiment 1 (for example, the chiller unit) is a refrigeration cycle apparatus having the housingin which at least a portion of the refrigerant circuitthrough which refrigerant circulates is located. The housingforms the outer shell and has the front side portion. The front side portionis removable. The at least portion of the refrigerant circuitincludes the condenser, the pressure containerin which refrigerant is reserved, the first pipe (the pipe) through which refrigerant flows, and connecting the condenserand the pressure container, and the pressure relief device. The pressure relief devicehas the fusible plug, is provided on the first pipe (the pipe), and is configured to release refrigerant when the pressure in the first pipe reaches a predetermined pressure. A portion of the first pipe (the pipe), on which the pressure relief deviceis provided (the first pipe portionin), is located beside the front side portionin the housing. More specifically, when the front side portionis removed, the fusible plugis located at a position where the fusible plugis exposed to the outside, that is, at a position where the fusible plugcan be viewed from the front.

This allows the fusible plugto be located beside the front side portionused as the maintenance side in the housing, and thus helps a worker to check and work on the fusible plugeasily during the servicing or the device assembly. This can improve the work efficiency.

The fusible plughas the outer circumferential portionprovided with a male thread. The male thread is provided on the outer circumferential portionof the fusible plugas described above, so that it is possible to directly connect the refrigerant recovery device configured to recover refrigerant (for example, a container) or other device to the fusible plug, and reduce the influence of improperly discharged refrigerant on the peripheral devices during the work.