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Air-conditioning apparatus

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Air-conditioning apparatus


To provide an air-conditioning apparatus that can prevent the formation of frost on indoor-side heat exchangers functioning as an evaporator even when the outside air temperature is low, and can use unmodified normal indoor units even when a portion of the indoor units is used in a place that has a large sensible heat load. An air-conditioning apparatus capable of simultaneous heating and cooling operation includes a heat source unit, a plurality of indoor units, and a relay unit that connects the heat source unit to the indoor units. A flow control unit that controls a flow amount of a refrigerant that flows through the indoor units that are in cooling operation is provided to a piping on the downstream side of a merging section of a piping through which flows the refrigerant that flows out from the indoor units that are in cooling operation.

Browse recent Mitsubishi Electric Corporation patents - Tokyo, JP
Inventor: Kazuyoshi Shinozaki
USPTO Applicaton #: #20120285675 - Class: 165207 (USPTO) - 11/15/12 - Class 165 
Heat Exchange > With Timer, Programmer, Time Delay, Or Condition Responsive Control >Having Heating And Cooling Capability >Plural Temperature Regulators For Plural Zones >Refrigeration System Having An Evaporator Or Condenser In Each Zone

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The Patent Description & Claims data below is from USPTO Patent Application 20120285675, Air-conditioning apparatus.

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TECHNICAL FIELD

The present invention is related to an air-conditioning apparatus, and, in particular, a multi-room heat pump air-conditioning apparatus that is capable of selectively heating and cooling each indoor unit and simultaneously operating indoor units performing cooling and indoor units performing heating, the multi-room heat pump air-conditioning apparatus connecting to a plurality of indoor units.

BACKGROUND ART

As a conventional air-conditioning apparatus capable of selectively heating and cooling each indoor unit and simultaneously operating indoor units performing cooling and indoor units performing heating (hereinafter referred to as an air-conditioning apparatus capable of simultaneous cooling and heating operation), for example, the following has been proposed (for example, refer to Patent Literature 1): “an air-conditioning apparatus capable of simultaneous heating and cooling operation, wherein one heat source unit consisting of a compressor, a four-way switching valve, a heat source unit-side heat exchanger, an accumulator, and the like is connected via first and second connecting pipings to a plurality of indoor units each consisting of an indoor-side heat exchanger, a first flow control device, and the like; a first branching unit that switchably connects one end of the indoor-side heat exchangers of the plurality of indoor units to the first connecting piping or the second connecting piping is connected via a second flow control device to a second branching unit which is connected to the other end of the indoor-side heat exchangers of the plurality of indoor units via the first flow control device and is connected to the second connecting piping via the second flow control device; the second branching unit and the first connecting piping are connected via a third flow control device; a relay unit containing the first branching unit, the second flow control device, the third flow control device, and the second branching unit is interposed between the heat source unit and the plurality of indoor units; the first connecting piping is constituted to have a larger diameter than the second connecting piping; a switching valve is provided between the first and second connecting pipings of the heat source unit; and the first connecting piping is switchable to a low pressure side of the heat source unit and the second connecting piping is switchable to a high pressure side of the heat source unit during both cases of operation in which the heat source unit-side heat exchanger is a condenser and operation in which the heat source unit-side heat exchanger is an evaporator”.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application, First Publication No. 4-335967 (Paragraph [0006] and FIG. 1)

SUMMARY

OF INVENTION Technical Problem

However, the conventional air-conditioning apparatus capable of simultaneous cooling and heating operation has the following problems.

For example, during simultaneous cooling and heating operation, when the heating load is larger than the cooling load, the heat source unit (outdoor) side heat exchanger functions as an evaporator. In this case, the heat exchangers of the indoor units (indoor-side heat exchangers) which are cooling also function as an evaporator. Accordingly, the heat source unit-side heat exchanger and the indoor-side heat exchangers functioning as an evaporator are serially connected. At this time, if the temperature of air sucked in by the heat source unit-side heat exchanger (that is, the outside air temperature) is low, the evaporation temperature of the indoor-side heat exchangers functioning as an evaporator will drop as the evaporation temperature of the heat source unit-side heat exchanger drops. Therefore, there has been a problem in that frost forms on the indoor-side heat exchangers functioning as an evaporator leading to a drop in cooling capacity. Further, there has been another problem in that in order to remove the frost, the indoor units performing cooling operation repeatedly starts and stop cooling, and thus making it difficult to maintain a continuous and stable operation state.

Furthermore, in some conventional air-conditioning apparatuses, in order to prevent drop of the evaporation temperature of the indoor-side heat exchangers functioning as an evaporator, an expansion device has been provided on an outlet-side piping of the indoor-side heat exchangers (more specifically, in each piping that is on the refrigerant outlet side when functioning as an evaporator). In such a conventional air-conditioning apparatus, the pressure loss on the evaporator outlet side is increased by adjusting the expansion device in order to prevent drop of the evaporation temperature of the indoor-side heat exchangers functioning as an evaporator. However, in this kind of conventional air-conditioning apparatus, an expansion device is provided for each indoor-side heat exchanger, and thus the throttling of each expansion device varies. Therefore, the throttle control of the flow control device provided on the inlet-side piping (more specifically, in the piping that is on the refrigerant inlet side when functioning as an evaporator) of each indoor-side heat exchanger changes. Accordingly, there has been a problem in that the operation of the air-conditioning apparatus becomes unstable.

In a case in which a portion of the indoor units are used for the cooling operation of a place that has a large sensible heat load such as a computer room provided in a building or the like, or in other words, in a place in which the sensible heat ratio among the cooling load (the ratio of the sensible heat load relative to the cooling load) is large, there has been a problem in that the other indoor units used in a place that has a normal cooling operation load cannot obtain the necessary sensible heat capacity. Since the sensible heat load is large and the latent heat load (load when the sensible heat load is removed from the cooling load) is small, there has been a problem in terms of the balance of the refrigeration cycle in that the evaporation temperature of the indoor-side heat exchangers drops leading to the indoor-side heat exchangers to freeze in which water leaks are caused. In order to obtain the necessary sensible heat capacity, it is necessary to use a specialized indoor unit that has large sensible heat ratios. However, when the sensible heat load on the indoor side changes such as when computers are increased, it is necessary to exchange the indoor units with ones tailored to the sensible heat load in each case, and, thus, leading to excessive cost.

In consideration of the above problems, an objective of the present invention is to provide an air-conditioning apparatus that can, even when the outside air temperature is low, prevent the formation of frost on the indoor-side heat exchangers functioning as an evaporator and operate continuously and stably, and can inexpensively obtain the necessary sensible heat capacity using unmodified normal indoor units even when a portion of the indoor units is used in a place that has a large sensible heat load such as a computer room.

Solution to Problem

The air-conditioning apparatus of the present invention is an air-conditioning apparatus that includes a heat source unit having a compressor, a four-way switching valve, and a heat source unit-side heat exchanger that is connected to the four-way switching valve; a plurality of indoor units each having an indoor-side heat exchanger and a first flow control device connected to one end of the indoor-side heat exchanger; and a relay unit that connects the heat source unit to the indoor units, and that is capable of simultaneous heating and cooling operation in which each of the indoor units selectively performing a cooling operation or a heating operation. The relay unit is connected to the heat source unit by a first connecting piping through which a refrigerant that flows out to the heat source unit flows and a second connecting piping through which the refrigerant that flows in from the heat source unit flows. The relay unit comprises a first branching unit that switchably connects the other end of each of the indoor-side heat exchangers to the first connecting piping or the second connecting piping, a second branching unit that switchably connects each first flow control device to the first connecting piping or the second connecting piping, and a flow control unit provided to the first connecting piping that controls a flow amount of the refrigerant that flows through the indoor-side heat exchangers functioning as an evaporator.

Advantageous Effects of Invention

According to the present invention, the flow amount of a refrigerant that flows through the indoor-side heat exchangers functioning as an evaporator (heat exchangers of the indoor units that are performing a cooling operation) is controlled by the flow control unit. Therefore, the evaporation temperature of the indoor-side heat exchangers functioning as an evaporator can be raised, and thus the sensible heat capacity of the indoor-side heat exchangers functioning as an evaporator can be improved.

Therefore, the air-conditioning apparatus of the present invention can, even when the outside air temperature is low, prevent the formation of frost on the indoor-side heat exchangers functioning as an evaporator and operate continuously and stably, and can inexpensively obtain the necessary sensible heat capacity using unmodified normal indoor units even when a portion of the indoor units is used in a place that has a large sensible heat load such as a computer room.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of a refrigerant circuit showing the air-conditioning apparatus according to Embodiment 1 of the present invention.



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stats Patent Info
Application #
US 20120285675 A1
Publish Date
11/15/2012
Document #
13511921
File Date
12/15/2009
USPTO Class
165207
Other USPTO Classes
165218, 165219
International Class
24F3/00
Drawings
6



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