Refrigeration Apparatus

The present invention relates to a refrigeration apparatus using a refrigeration cycle working medium containing a fluoroolefin and particularly relates to a refrigeration apparatus that can successfully avoid the impact of disproportionation of a fluoroolefin.

A refrigeration cycle working medium is usually composed of a refrigerant and a refrigerating machine oil (lubricating oil retained in a hermetic compressor). HCFCs (hydrochlorofluorocarbons) had been used as refrigerants in the past; however, they contribute considerably to ozone depletion. Thus, in recent years, HFCs (hydrofluorocarbons) having an ozone depletion potential (ODP) of zero have been used. A typical example is difluoromethane (HFC-32 or R-32).

Although HFCs have stability when used as refrigeration cycle working media, they have a long atmospheric lifetime and therefore a high global warming potential (GWP). Thus, nowadays, the use of fluoroolefins having a lower GWP than HFCs, in particular the use of hydrofluoroolefins (HFOs), has been proposed. For example, 1,1,2-trifluoroethylene (HFO-1123) is known as an HFO having a low GWP, having high cooling ability, and having performance similar to that of R-32 which is currently in widespread use.

An example of a previously proposed refrigeration apparatus using a fluoroolefin such as HFO-1123 is disclosed in Patent Literature 1.

The refrigeration apparatus disclosed in Patent Literature 1 includes a dual cycle made up of a heat source-side heat medium circuit and a load-side heat medium circuit, and at least one of a heat source-side heat medium and a load-side heat medium which are used in the circuits is a refrigerant containing HFO-1123. The heat source-side heat medium circuit includes a cascade heat exchanger that effects heat exchange between the heat source-side and load-side heat media.

In this refrigeration apparatus, the heat source-side heat medium circuit is located in an outdoor space, and a load-side heat exchanger included in the load-side heat medium circuit is located in an indoor space. Thus, the cascade heat exchanger included in the heat source-side heat medium circuit is located in the outdoor space.

PTL 1: WO 2015/140872

The fact that fluoroolefins have a low GWP means that they have a short atmospheric lifetime. In other words, fluoroolefins are easily chemically decomposed and have low stability. A fluoroolefin such as HFO-1123 is known to easily undergo a self-polymerization reaction called a disproportionation reaction (hereinafter referred to as “disproportionation”).

It is believed that disproportionation is often induced, for example, by high pressure or generated heat during the use of a refrigeration cycle working medium. Additionally, the occurrence of disproportionation entails a large amount of heat release, and a chain reaction of disproportionation is known to occur. Such disproportionation results in a large amount of soot, which could reduce the reliability of the refrigeration cycle system.

In the refrigeration apparatus disclosed in Patent Literature 1, as mentioned above, either or both of the working media (heat source-side and load-side heat media) used in the heat source-side and load-side heat medium circuits of the dual cycle may contain HFO-1123. However, Patent Literature 1 gives no consideration to the occurrence of disproportionation of a fluoroolefin such as HFO-1123 or the impact of disproportionation on the heat source-side and load-side heat medium circuits.

The present invention has been made to solve the problem as described above, and an object of the present invention is to provide a refrigeration apparatus using a fluoroolefin as a working medium and including a dual cycle made up of an indoor-side circuit and an outdoor-side circuit, the refrigeration apparatus being adapted to, in the event of disproportionation of the fluoroolefin, successfully avoid the possibility that the disproportionation has an impact on indoor equipment.

In order to solve the problem as described above, a refrigeration apparatus according to the present disclosure includes: a first heat exchanger; a second heat exchanger; a compressor; and an expansion mechanism, wherein the first heat exchanger, the compressor, and the expansion mechanism are located in an outdoor space and connected to first piping that allows a first working medium to circulate through the first heat exchanger, the compressor, and the expansion mechanism, the first heat exchanger, the compressor, the expansion mechanism, and the first piping constituting an outdoor-side circuit, the second heat exchanger is located in an indoor space and connected to second piping that allows a second working medium to circulate through the second heat exchanger, the second heat exchanger and the second piping constituting an indoor-side circuit, the refrigeration apparatus further includes a secondary heat exchanger located between the first piping and the second piping to effect heat exchange between the first working medium and the second working medium, the secondary heat exchanger is located in the outdoor space, the first working medium contains at least a fluoroolefin, and the second working medium contains no fluoroolefin.

In the above configuration, any fluoroolefin which can undergo disproportionation is not used as the second working medium circulating in the indoor-side circuit, while a fluoroolefin is used as the first working medium circulating in the outdoor-side circuit. In addition, the secondary heat exchanger which enables heat exchange between the indoor-side circuit and the outdoor-side circuit is located in the outdoor space. Thus, in the event that disproportionation of the fluoroolefin occurs in the outdoor-side circuit and has an impact on the secondary heat exchanger, this event only affects the outdoor equipment. As such, the possibility of disproportionation having an impact on the indoor equipment can be effectively avoided.

The above and further objects, features and advantages of the present invention will be more apparent from the following detailed description of preferred embodiments with reference to the accompanying drawings.

The present invention can provide a refrigeration apparatus configured as described above which uses a fluoroolefin as a working medium and includes a dual cycle made up of an indoor-side circuit and an outdoor-side circuit, the refrigeration apparatus being adapted to, in the event of disproportionation of the fluoroolefin, successfully avoid the possibility that the disproportionation has an impact on the indoor equipment.

A refrigeration apparatus according to the present disclosure includes: a first heat exchanger; a second heat exchanger; a compressor; and an expansion mechanism, wherein the first heat exchanger, the compressor, and the expansion mechanism are located in an outdoor space and connected to first piping that allows a first working medium to circulate through the first heat exchanger, the compressor, and the expansion mechanism, the first heat exchanger, the compressor, the expansion mechanism, and the first piping constituting an outdoor-side circuit, the second heat exchanger is located in an indoor space and connected to second piping that allows a second working medium to circulate through the second heat exchanger, the second heat exchanger and the second piping constituting an indoor-side circuit, the refrigeration apparatus further includes a secondary heat exchanger located between the first piping and the second piping to effect heat exchange between the first working medium and the second working medium, the secondary heat exchanger is located in the outdoor space, the first working medium contains at least a fluoroolefin, and the second working medium contains no fluoroolefin.

In the above configuration, any fluoroolefin which can undergo disproportionation is not used as the second working medium circulating in the indoor-side circuit, while a fluoroolefin is used as the first working medium circulating in the outdoor-side circuit. In addition, the secondary heat exchanger which enables heat exchange between the indoor-side circuit and the outdoor-side circuit is located in the outdoor space. Thus, in the event that disproportionation of the fluoroolefin occurs in the outdoor-side circuit and has an impact on the secondary heat exchanger, this event only affects the outdoor equipment. As such, the possibility of disproportionation having an impact on the indoor equipment can be effectively avoided.

The refrigeration apparatus configured as described above may further include bypass piping connected to the first piping in parallel to the secondary heat exchanger and including a shut-off valve, and the bypass piping may be located in the outdoor space.

In the refrigeration apparatus configured as described above, the indoor-side circuit may include a pump that pumps the second working medium to the second heat exchanger, and an indoor-side inflow shut-off valve that blocks inflow of the second working medium into the secondary heat exchanger, and the pump may be stopped in case that the indoor-side inflow shut-off valve blocks the inflow of the second working medium.

In the refrigeration apparatus configured as described above, the indoor-side circuit may further include a gas-liquid separator connected to the second piping and located in the outdoor space, and the gas-liquid separator may include a safety valve that discharges a gas at a predetermined pressure.

In the refrigeration apparatus configured as described above, the indoor-side circuit may further include an indoor-side outflow shut-off valve located to block outflow from the gas-liquid separator.

The refrigeration apparatus configured as described above may further include: a controller; and a first working medium temperature detector that measures a temperature of the first working medium flowing in the first piping, and the controller may open the shut-off valve of the bypass piping in case that the temperature measured by the first working medium temperature detector has reached a predetermined temperature.

The refrigeration apparatus configured as described above may further include: a controller; and a first working medium temperature detector that measures a temperature of the first working medium flowing in the first piping, the outdoor-side circuit may further include an outdoor-side flow shut-off valve that blocks inflow of the first working medium into the secondary heat exchanger and outflow of the first working medium from the secondary heat exchanger, and the controller may close the outdoor-side flow shut-off valve and stop operation of the outdoor-side circuit in case that the temperature measured by the first working medium temperature detector has reached a predetermined temperature.

In the refrigeration apparatus configured as described above, the secondary heat exchanger may be a plate heat exchanger, a double pipe heat exchanger, or a shell-and-tube heat exchanger.

In the refrigeration apparatus configured as described above, the first working medium may be a refrigerant mixture containing propane in addition to the fluoroolefin.

In the refrigeration apparatus configured as described above, the first working medium may further contain a disproportionation inhibitor.

In the refrigeration apparatus configured as described above, the second working medium may be a liquid refrigerant or a low-pressure refrigerant.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. The same or equivalent elements are denoted by the same reference signs throughout the drawings and will not be described repeatedly.

A refrigeration apparatus Rshown inis a typical example of a configuration according to Embodiment 1. The refrigeration apparatus RI is configured as an air conditioner. As shown in, the refrigeration apparatus RI according to Embodiment 1 includes an outdoor-side circuitand an indoor-side circuit.

As shown by a dashed box in, the outdoor-side circuitincludes first piping, a compressor, a first heat exchanger, a first blower, an expansion valve, a four-way valve, a secondary heat exchanger, etc. The indoor-side circuit, as shown by a dashed box inlike the outdoor-side circuit, includes second piping, a pump, a second heat exchanger, a second blower, the secondary heat exchanger, etc. The secondary heat exchangeris a component shared by both the outdoor-side circuitand the indoor-side circuit.

In the outdoor-side circuit, the compressor, the secondary heat exchanger, the expansion valve, and the first heat exchangerare arranged in this order and serially connected in a loop by the first pipingand via the four-way valveto constitute one refrigeration cycle.

A first working medium containing at least a fluoroolefin circulates in the outdoor-side circuit. The fluoroolefin contained in the first working medium is, for example, but not limited to, 1,1,2-trifluoroethylene (HFO-1123) in Embodiment 1. The first working medium may be a single-component refrigerant consisting only of HFO-1123 or may be a refrigerant mixture containing another refrigerant component in addition to HFO-1123. The details of the first working medium will be described later.

The compressorcompresses the first working medium. The first heat exchangereffects heat exchange between the first working medium and outdoor air (outside air). The first blowerdelivers outdoor air toward the first heat exchanger. The expansion valveis an expansion mechanism that expands the first working medium.

The discharge outlet and the suction inlet of the compressorare connected to the four-way valve. The four-way valveswitches between different positions to change the flow direction of the first working medium. A cooling operation takes place when the four-way valveis in a position to connect the discharge outlet of the compressorto the first heat exchanger, while a heating operation takes place when the four-way valveis in a position to connect the discharge outlet of the compressorto the secondary heat exchanger. The cooling and heating operations will be described later. In, the direction in which the first working medium flows during the cooling operation is shown by a black block arrow F, and the direction in which the first working medium flows during the heating operation is shown by a white block arrow F.

In the indoor-side circuit, the pump, the secondary heat exchanger, and the second heat exchangerare arranged in this order and serially connected in a loop by the second pipingto constitute one refrigeration cycle. The bold dotted line ofis a boundary line between the indoor space and the outdoor space. Of the components of the indoor-side circuit, as shown in, only the second heat exchangeris located in the indoor space, and the pumpand the secondary heat exchangerare located in the outdoor space. The pumpmay be located in the indoor space. All the components of the outdoor-side circuitare located in the outdoor space.

A second working medium containing no fluoroolefin circulates in the indoor-side circuit. The second working medium is not limited to a particular composition and may have any composition insofar as the second working medium does not contain any fluoroolefin. For example, a known liquid refrigerant or low-pressure refrigerant can be suitably used as the second working medium. In Embodiment 1, carbon dioxide (CO) is used as the second working medium. The liquid refrigerant used may be, for example, water, brine composed mainly of water, or an antifreeze fluid. The details of the second working medium will also be described later.

The pumppumps the second working medium through the second piping. The second heat exchangereffects heat exchange between the second working medium and indoor air. The second blowerdelivers indoor air toward the second heat exchanger. The indoor-side circuitdoes not include any component corresponding to the four-way valvein the outdoor-side circuit. Thus, in the indoor-side circuit, the second working medium flows and circulates only in one direction. In, the flow direction of the second working medium is shown by a black block arrow F.

As previously stated, the secondary heat exchangeris a component shared by both the outdoor-side circuitand the indoor-side circuit. The secondary heat exchangereffects heat exchange between the first working medium circulating in the outdoor-side circuitand the second working medium circulating in the indoor-side circuit. It can therefore be said that the outdoor-side circuitand the indoor-side circuitare thermally connected via the secondary heat exchanger.

As described above, the refrigeration apparatus Raccording to the present disclosure is configured as a dual cycle apparatus including two circuits thermally connected via the secondary heat exchanger, and the secondary heat exchangereffects heat exchange between the first and second working media. Thus, the outdoor-side circuitand the indoor-side circuit, which are refrigeration cycles independent of each other, can be controlled together as one refrigeration apparatus R.

In the present disclosure, the compressor, the first heat exchanger, the first blower, the expansion valve, the four-way valve, the pump, the second heat exchanger, the second blower, and the secondary heat exchangerconstituting the refrigeration apparatus Rare not limited to particular configurations, and any configurations known in the field of refrigeration apparatuses RI can be suitably employed.

For example, a known hermetic refrigerant compressor can be used as the compressor. The hermetic refrigerant compressor may be any kind of compressor such as a reciprocating, rotary, scroll, or screw compressor. The electric element of the refrigerant compressor may have the same configuration as any known motor and may be an outer rotor-type motor or an inner rotor-type motor.

The first heat exchangeris a heat exchanger “located in the outdoor space” and can be regarded as corresponding to a “condenser” of a common refrigeration apparatus. Likewise, the second heat exchangeris a heat exchanger “located in the indoor space” and can be regarded as corresponding to an “evaporator” of a common refrigeration apparatus. Thus, a heat exchanger known as a condenser can be used as the first heat exchanger, and a heat exchanger known as an evaporator can be used as the second heat exchanger. Examples of such heat exchangers include, but are not limited to, plate heat exchangers, double pipe heat exchangers, and shell-and-tube heat exchangers.

As with the first heat exchangeror the second heat exchanger, a known heat exchanger can be suitably used as the secondary heat exchanger. In particular, since the secondary heat exchangereffects heat exchange between the first and second working media unlike the first heat exchangeror second heat exchangerwhich effects heat exchange between a corresponding one of the working media and air (outdoor air or indoor air), the type of the heat exchanger used as the secondary heat exchangercan be selected depending on the types of the first and second working media.

In the present disclosure, where the first working medium is a refrigerant containing a fluoroolefin, the second working medium may be, for example, a common refrigerant containing a hydrofluorocarbon as a main component, and in this case a plate heat exchanger can be used as the secondary heat exchanger. In the case where the second working medium is a liquid refrigerant such as water, brine, or an antifreeze fluid, a shell-and-tube heat exchanger can be used as the secondary heat exchanger. A shell-and-tube heat exchanger includes an outer pipe (shell) serving as an enclosure body and a number of inner pipes (tubes) located inside the outer pipe. With the use of such a heat exchanger, the second working medium which is a liquid refrigerant can be made to flow through the inner pipes, while the first working medium containing a fluoroolefin can be made to flow through the outer pipe.

The expansion valveused may be a thermostatic expansion valve, an electronic expansion valve, or any other expansion mechanism. As for the four-way valve, the pump, the first blower, the second blower, etc., various known configurations can be suitably employed.

The following will describe exemplary operations of the refrigeration apparatus Rdescribed above. A cooling operation will be described first. In the outdoor-side circuit, the first working medium compressed by the compressorand having a high temperature and a high pressure is delivered to the first heat exchangervia the four-way valve(the direction of the arrow F). The first heat exchangerallows the first working medium to exchange heat with outdoor air (outside air) delivered by the first blowerand thus turn into a high-pressure, middle-to-high temperature liquid, which is delivered to the expansion valve.

The first working medium is expanded by the expansion valveand turns into a low-pressure, low-temperature gas-liquid mixture, which is delivered to the secondary heat exchanger. The secondary heat exchangereffects heat exchange between the first working medium and the second working medium circulating in the indoor-side circuit, thus turning the first working medium into a low-pressure, middle-to-low-temperature gas, which is sucked into the suction inlet of the compressorvia the four-way valve.

In the indoor-side circuit, the second working medium is pumped by the pumpto the secondary heat exchanger(the direction of the arrow F). As stated above, the secondary heat exchangereffects heat exchange between the first and second working media; thus, the second working medium is cooled by the first working medium having a low temperature and a low pressure. The cooled second working medium is delivered to the second heat exchangerlocated in the indoor space. The second heat exchangerallows the second working medium to exchange heat with indoor air delivered by the second blower, and thus the indoor air is cooled by the second working medium and cools the indoor space.

Next, a heating operation will be described. In the outdoor-side circuit, the first working medium compressed by the compressorand having a high temperature and a high pressure is delivered to the secondary heat exchangervia the four-way valve(the direction of the arrow F). The secondary heat exchangereffects heat exchange between the first working medium and the second working medium circulating in the indoor-side circuit, thus turning the first working medium into a high-pressure, middle-to-low-temperature liquid, which is delivered to the expansion valve.

The first working medium is expanded by the expansion valveand turns into a low-temperature, low-pressure gas-liquid mixture, which is delivered to the first heat exchanger. The first heat exchangerallows the first working medium to exchange heat with outdoor air delivered by the first blowerand thus turn into a low-pressure, middle-to-low-temperature gas, which is sucked into the suction inlet of the compressor.