Patent Description:
Generally speaking, air-conditioners consist of one or more outdoor units and one or more indoor units connected via a refrigerant piping. The outdoor and indoor units each comprise a heat exchanger for, on the one hand, exchanging heat with the heat source and, on the other hand, exchanging heat with the space to be conditioned. Outdoor units of air-conditioners are in most cases installed outside a building for example on the roof or at the façade. This, however, has under certain circumstances being perceived disadvantageous from an aesthetical point of view. Therefore, <CIT> suggested to integrate the outdoor unit into a ceiling of the building so as to be hidden therein and not to be noticeable from the outside of the building.

Yet, the outdoor unit suggested in this document has certain disadvantages. One negative aspect is that the outdoor unit produces noises which may be perceived disturbing by individuals inside the building. A second negative aspect is installation and maintenance, because the outdoor unit is relatively heavy and because of its construction requires a relatively large installation space with respect to its height.

To overcome these drawbacks, the applicant of the present application has considered splitting the heat source unit into a compressor unit and a heat source heat exchanger unit. Further, some appliances require the integration of a sub-cooling section into the refrigerant circuit to increase efficiency. Yet, the integration of a sub-cooling section into a splitted heat source unit may require more piping between the heat source heat exchanger unit and the compressor unit as well as the indoor unit leading to a more complicated installation and higher installation costs. In addition, more piping through which gaseous refrigerant flows is required. Such piping is more expensive due to a larger required diameter and hence more material. Moreover, more time is necessary for installation. Finally, a loss of effect may be recognized if the piping for gaseous refrigerant between the compressor unit and the heat source heat exchanger unit becomes too long. The above disadvantages have been recognized when disposing the sub-cooling heat exchanger close to the heat source heat exchanger, i.e. in the heat source heat exchanger unit.

A compressor unit having the features of the preamble of claim <NUM> is known from <CIT>. Further, <CIT> discloses an air-conditioner, wherein one heat exchanger is contained in an external casing outside the building and other components, namely another heat exchanger, an expander and a compressor, are contained in an internal chamber arranged inside the building.

Accordingly, one object the present invention intends to solve is to provide a compressor unit, preferably as part of the above-described heat source unit, as well as a heat source unit having such a compressor unit, which are capable of reducing the piping and particularly the piping for gaseous refrigerant for connecting the several units to a minimum even if a sub-cooling section is integrated, thereby ensuring ease of installation and lower installation costs.

<CIT> discloses a heat source unit for an air conditioner according to the preamble of claim <NUM>, relating to an air-conditioning apparatus capable of having a thin low-pressure gas pipe even when a refrigerant with a low refrigerant density at low pressure is used. <CIT> states a refrigerant apparatus using an HFC group refrigerant in which the performance is improved by increasing the refrigerating capacity and a stable operation is made possible.

Accordingly, one object the present invention intends to solve is to provide a heat source unit having a compressor unit, which is capable of reducing the piping and particularly the piping for gaseous refrigerant for connecting the several units to a minimum even if a sub-cooling section is integrated, thereby ensuring ease of installation and lower installation costs.

This object is solved by a heat source unit according to claim <NUM>. Embodiments of the invention are named in the dependent claims, the following description and the accompanying drawings.

According to one aspect, a heat source unit for an air conditioner is suggested. The air-conditioner is configured to condition a space such as a room inside the building, be it heating or cooling. The heat source unit comprises a compressor unit having a compressor disposed in a first casing. Accordingly, the first casing is accommodating the compressor and preferably encapsulating the compressor. Additionally, a sound insulation may be provided at the inside or outside of the casing to avoid noises produced by the compressor from being transferred to the environment in which the compressor unit is installed. Further, a first and second heat source ports are provided and preferably accessible from the outside of the casing for ease of connection. The first and second heat source ports are configured to connect the compressor to a heat source heat exchanger of a heat source unit of the air conditioner by means of a refrigerant piping. The first and second heat source ports may be of any kind capable of connecting a refrigerant piping to the compressor such as a pipe open at one end and having an outer thread at the end. Yet, also so-called self-sealing connectors or quick fasteners may be used. In most cases it will however due to regulations be required to use flairs or braised connections. The heat source heat exchanger is disposed in a second casing separate from the first casing and configured to exchange heat with a heat source. "Separate" in this context means that the casings represent separate assemblies or units and should not encompass that one casing is disposed within the other casing. In a particular embodiment, the heat source heat exchanger unit uses outside air (i.e. air outside the building) as heat source. For this purpose, it is preferred that the second casing has a first connection at one side of the heat exchanger and a second connection at an opposite side of the heat exchanger. The first and second connections are preferably connected to ducting fluidly communicated with the outside of the building so that outside air may pass the first heat exchanger. Moreover, the compressor unit comprises a first and second indoor unit ports configured to connect the compressor to an indoor heat exchanger of at least one indoor unit of the air conditioner by refrigerant piping. The first and second indoor unit ports may be of the same or different kind as the first and second heat source ports. Further, the compressor unit comprises a first refrigerant piping preferably disposed within the first casing. The first refrigerant piping fluidly connects the first heat source port and the first indoor unit port. Accordingly, the first heat source port and the first indoor unit port are used to fluidly connect the heat source heat exchanger unit to one or more indoor units using refrigerant piping. Even though the connection between the heat source heat exchanger unit and the indoor unit/-s could be made to direct, one aspect suggests to connect these units via the compressor unit so that part of the refrigerant piping connecting these units passes through the first casing of the compressor unit. Furthermore, a sub-cooling heat exchanger is disposed inside the first casing and fluidly connected to the first refrigerant piping for sub-cooling refrigerant to be flown through the first refrigerant piping. Because the first refrigerant piping is passing through the first casing, the sub-cooling heat exchanger may be integrated into the air conditioner without an additional gaseous refrigerant piping being necessary to connect the compressor unit and the heat source heat exchanger unit and particularly the heat source heat exchanger and the suction side of the compressor passing the sub-cooling heat exchanger. This additional long gaseous refrigerant piping is integrated into the compressor unit and therefore much shorter so that less material is required and less installation time necessary. Therefore, ease of installation is obtained and the installation costs are reduced.

The compressor unit further comprises a second refrigerant piping. The second refrigerant piping fluidly communicates or connects the second heat source port and the second indoor unit port. The compressor and preferably a <NUM>-way valve are interposed between the second heat source port and the second indoor unit port or more particular in the second refrigerant piping connecting these ports. An accumulator may be included on the suction side of the compressor. Moreover, a bypass passage is connected to the second refrigerant piping at the suction side of the compressor between the compressor and the <NUM>-way valve and the sub-cooling heat exchanger is fluidly connected to the bypass passage for heat transfer between the refrigerant flowing in the bypass line and refrigerant flowing through the first refrigerant piping. Hence, all piping relating to the sub-cooling unit is a contained in the first casing so that in one embodiment only four ports are required in the compressor unit. To connect the compressor unit, the heat source heat exchanger unit and one indoor unit. In particular, an additional route between the heat source heat exchanger unit and the indoor unit can be avoided by placing the sub-cooling heat exchanger in the compressor unit and looping the refrigerant piping connecting the heat source heat exchanger module to the indoor unit through the compressor unit. An additional advantage of disposing the sub-cooling heat exchanger in the compressor module is that a large diameter pipe usually required to flow the gaseous refrigerant can be avoided.

The heat source unit for an air conditioner further comprises a heat source heat exchanger unit. The heat source heat exchanger unit has a heat source heat exchanger disposed in the second casing separate from the first casing as described above. The heat source heat exchanger is configured to exchange heat with a heat source particularly outside air and is fluidly connected or communicated to the compressor unit via the first and second heat source port. In this context, and because of the connection of the first heat source port and the first indoor unit port by the first refrigerant piping the connection of the heat source heat exchanger unit and the indoor unit is looped through the compressor unit (first casing). Thereby, it is possible to integrate the sub-cooling unit into the compressor unit without an additional piping required to connect the compressor unit with the heat source heat exchanger unit.

According to an aspect, the compressor unit does not comprise a main expansion valve of the air conditioner. The "main expansion valve" of an air conditioner is defined as that expansion valve through which the entire amount of refrigerant in the refrigerant circuit passes during cooling.

In heating the main expansion valve defines the superheat after the heat source heat exchanger. In cooling the main expansion valve is always fully opened to avoid a high pressure drop. In cooling the entire amount of refrigerant passes the main expansion valve. In heating, the amount of refrigerant is separated between the flow through the sub-cooling heat exchanger and the heat source heat exchanger.

In heating operation, a relatively large pressure drop exists because of a relatively long refrigerant piping connecting the sub-cooling heat exchanger to the heat source heat exchanger. Because the main expansion valve is not disposed in the compressor unit, a refrigerant pressure drop between the compressor unit and the heat source heat exchanger unit can be can be compensated and two phase flow noise is reduced.

According to an embodiment, the compressor unit may comprise an oil separator located at the discharge side of the compressor between the compressor and a (the) <NUM>-way valve.

As described previously, the main expansion valve of the air conditioner is disposed in the second casing, i.e. in the heat source heat exchanger unit. Accordingly, the pressure drop between the compressor unit and the heat source heat exchanger unit is kept as low as possible and two phase flow noises can be avoided.

As previously indicated, one or more indoor units can be fluidly connected or communicated to the compressor unit via the first and second indoor unit port. This context, the first indoor unit port serves for the connection of the indoor unit and particularly an indoor heat exchanger to the heat source heat exchanger unit and particularly the heat source heat exchanger. The second indoor unit port serves to connect the indoor unit and particularly the indoor heat exchanger to the second refrigerant piping and, hence, the compressor. If more than one indoor unit is provided, the indoor units can be connected in parallel.

Further features and effects of the heat source unit may be obtained from the following description of embodiments. In the description of these embodiments reference is made to the accompanying drawings.

<FIG> shows the circuit diagram of an air conditioner. The air-conditioner has a heat source unit <NUM> comprising a heat source heat exchanger unit <NUM> and a compressor unit <NUM>.

The heat source heat exchanger unit <NUM> comprises a heat exchanger <NUM> which consists of an upper heat exchanger element <NUM> and a lower heat exchanger element <NUM> which are positioned relative to each other to form the shape of a "V" in a side view or cross sectional view (see <FIG>). The heat source heat exchanger unit <NUM> further comprises the main expansion valve <NUM> of the refrigerant circuit. As becomes apparent from <FIG>, the entire amount of refrigerant contained in the circuit also passes the main expansion valve <NUM> during cooling. In other words, the entire amount of refrigerant delivered or supplied from the compressor <NUM> flows through the main expansion valve <NUM> during cooling.

The heat source heat exchanger unit is also shown in more detail in <FIG> and <FIG>.

<FIG> and <FIG> show a heat source heat exchanger unit <NUM> which may be part of the heat source unit <NUM>.

The heat source heat exchanger unit <NUM> comprises a casing <NUM> (second casing) being configured for connection to an outside air duct of an air conditioner. In particular, the heat source heat exchanger unit is configured as an "outdoor" unit of an air conditioner which is, however, disposed inside particularly within the ceiling of a building. Hence, a first connection <NUM> is provided at the casing <NUM> for connection to an air duct communicating the heat source heat exchanger unit <NUM> with the outside of the building and so as to enable taking of outdoor air into the casing <NUM>. A connection <NUM> (See <FIG>), provided for the connection of the heat source heat exchanger unit <NUM> to the air duct again leading to the outside of the building and to enable exhausting of air having passed the heat exchanger <NUM> to the outside, is disposed at the opposite end of the casing <NUM>.

The casing <NUM> is substantially rectangular and flat, meaning that the height H is a smaller than the width W and the length L. In one embodiment the height H is not more than <NUM>, preferably not more than <NUM>, more preferred not more than <NUM> and most preferred not more than <NUM>.

The heat source heat exchanger unit <NUM> further comprises a heat exchanger <NUM> (heat source heat exchanger) which is also visible in <FIG>. However, the configuration of the heat exchanger <NUM> can be best seen from <FIG> also represents a side view of the heat exchanger <NUM> in the sense of the present application.

The heat exchanger <NUM> comprises an upper heat exchanger element <NUM> and a lower heat exchanger element <NUM>. Both, the upper and lower heat exchanger elements <NUM>, <NUM> are flat or planar shaped and are positioned with an angle α enclosed between them. As best visible from <FIG>, the upper and lower heat exchanger elements <NUM>, <NUM> are fluidly connected in parallel to the refrigerant piping. Hence the heat exchanger <NUM> has a V-shape wherein the "V" is oriented horizontally. A line CL passing the apex <NUM> of the "V" is oriented horizontally, that is along the length L extension of the heat source heat exchanger unit <NUM>. The line CL is also the centerline of the heat exchanger <NUM> or to put it differently a line of symmetry as regards the heat exchanger elements <NUM>, <NUM>.

The heat exchanger <NUM> is arranged within the air duct formed by the casing <NUM> so that all air sucked in through the opening at the connection <NUM> has a to flow through the heat exchanger <NUM> without any air bypassing the heat exchanger <NUM> at the top or the bottom or the sides of the heat exchanger <NUM> in the width direction W.

The upper and lower heat exchanger elements <NUM>, <NUM> are connected to each other at the apex <NUM> by a connecting element <NUM>. The connecting element is impermeable to air and also used to mechanically or physically connect the upper and lower heat exchanger elements <NUM>, <NUM>. Each of the heat exchanger elements <NUM>, <NUM> comprises heat exchanger coils <NUM> (loops of tubing) and fins <NUM> disposed there between. The heat exchanger of the present embodiment is applied for outdoor applications, i.e. as part of the heat source unit of an air conditioner. In this case, the fins of the upper and lower heat exchanger element <NUM>, <NUM> are preferably waffled fins. Even though louvered fins are preferably used for a good air flow through the heat exchanger as several holes are provided to allow the air to flow through the fins, condensation water may accumulate in these holes and may lead to problems regarding the formation of frost during heating operation, when the ambient temperature is lower than about <NUM>. To prevent these problems it is in these cases preferred to use waffled fins.

Two backward curved centrifugal fans <NUM> are provided inside the casing. These backward curved centrifugal fans <NUM> each have a suction opening <NUM>. In the side view (<FIG>), the center axis of the suction opening <NUM> and hence the fans <NUM> is substantially congruent or aligned with the center line CL of the heat exchanger <NUM>. In some appliances, it may however be sufficient as in the depicted embodiment that the center axis of the suction opening <NUM> and the centerline CL of the heat exchanger <NUM> are parallel but displaced relative to each other in a horizontal direction.

In use, the fans <NUM> create a suction force at the suction opening <NUM> so as to induce a fluid flow (airflow) in the direction F. Thus air, particularly outside air is drawn in through the connection <NUM> toward the open end <NUM> of the heat exchanger <NUM>, passes through the upper and lower heat exchanger elements <NUM>, <NUM> and is sucked through the suction opening <NUM> to be flown out through the connection <NUM>. As such the casing <NUM> defines a duct from the connection <NUM> via the heat exchanger <NUM> and the fan <NUM> to the connection <NUM>. In this context, the connection <NUM> and the connection <NUM> define an inlet opening <NUM> and an outlet opening <NUM>.

Furthermore, a drain pan <NUM> is provided within the casing. The drain pan <NUM> is separated into two halves <NUM>, <NUM> along the length L of the casing <NUM> in the side view. In <FIG>, the two halves <NUM>, <NUM> are identified by the dotted line with one half being located on the left side and one half being located on the right side of the dotted line. The drain pan <NUM> has a lowest position <NUM> at which a drain opening <NUM> is provided. The bottom of the drain pan <NUM> slants toward the drain opening <NUM> and hence the lowest position <NUM>. Thus water dropping from any component into the drain pan is directly guided to the drain opening <NUM> and the lowest position <NUM> which is furthest away from the fan <NUM>. Thereby it is prevented that water accumulated within the drain pan may be sucked into the fan <NUM> and hence through the opening <NUM> into the duct. The drain opening <NUM> is directly connected to drainage so that water is directly drained.

Moreover, a sound and/or thermal insulation <NUM> are provided within the casing <NUM> at the side opposite to the drain pan <NUM> with respect to the line CL. In the cross section and hence a side view (<FIG>), the inner surfaces of the drain pan <NUM> and the insulation <NUM> respectively directed to the heat exchanger <NUM> should be approximated so that the duct created within the casing <NUM> is as symmetric as possible.

Further, the distance between the apex <NUM> and the entry of the suction opening <NUM> should be as short as possible to reduce the length. In particular, the high velocity zone of the fans should in the side view not overlap with the heat exchanger <NUM> and/or the drain pan <NUM>.

At a side of the casing <NUM>, one can see a first and second refrigerant piping connection <NUM> and <NUM> for connecting the heat source heat exchanger unit <NUM> to the refrigerant piping of the refrigerant circuit. In addition a connection port <NUM> for connecting the drain opening <NUM> to drainage (not shown) extends from the same side surface of the casing <NUM> as the refrigerant piping connections <NUM> and <NUM>.

The casing <NUM> is completely closed relative to the environment except for the connections <NUM> and <NUM> as well as the refrigerant piping connections <NUM> and <NUM> and the connection <NUM> to the drainage. Accordingly and as can be seen from <FIG> the casing may be sound insulated and thereby encapsuled to prevent any noises for example from the fans from being transferred to the space to be conditioned. In addition and because the compressor <NUM> is not disposed in the casing <NUM> but the compressor unit <NUM> as described below, no noise of the compressor is induced and transferred via the air flowing through the heat source heat exchanger unit <NUM> and in the air duct connected to the outside of the building.

The compressor unit <NUM> has a casing <NUM> (First casing) wherein in <FIG> a front wall of the casing <NUM> and a corresponding sound insulation have been removed to partly show the interior of the casing <NUM>. A compressor <NUM> (see <FIG>) is disposed in the casing <NUM>. Furthermore, all other components of the compressor unit described below and if present will be disposed in the casing <NUM> as well. In addition, the compressor unit may comprise an optional accumulator <NUM> and a <NUM>-way valve <NUM>.

In addition, the compressor unit <NUM> comprises a sub-cooling heat exchanger <NUM> and a sub-cooling expansion valve <NUM>. The sub-cooling heat exchanger is a tube heat exchanger.

The compressor unit <NUM> further comprises first and second refrigerant piping connections <NUM> and <NUM> (first and second heat source heat exchanger unit ports) as shown in <FIG>.

A stop the valve <NUM> (two stop valves, one for each connection <NUM>, <NUM>) may be provided close to the first and second refrigerant piping connections <NUM> and <NUM>, respectively.

Further a third and fourth refrigerant piping connection <NUM> and <NUM> (first and second indoor unit ports) are provided for connection of one or more indoor units <NUM> (one in the present embodiment) disposed in fluid communication with the space to be conditioned. A stop valve <NUM> (two stop valves, one for each connection <NUM>, <NUM>) is also provided close to the refrigerant piping connections <NUM> and <NUM>, respectively.

Ports <NUM>, <NUM> and <NUM>, <NUM> are all disposed close to the front of the compressor unit to improve serviceability. In particular, if the front wall of the casing <NUM> and the corresponding insulation is removed as in <FIG>, the ports are easily accessible.

Moreover, a refrigerant piping <NUM> (second refrigerant piping) connects the refrigerant piping connection <NUM> and the refrigerant piping connection <NUM> with the <NUM> way valve <NUM>, the compressor <NUM>, the accumulator <NUM>, the connection <NUM> to the refrigerant piping <NUM>, the connection <NUM> to the refrigerant piping <NUM> and the <NUM>-way valve <NUM> being interposed in this order.

The aforesaid components are disposed in the following order from the refrigerant piping connection <NUM> to the refrigerant piping connection <NUM> considering cooling operation (solid arrows in <FIG>): the <NUM>-way valve <NUM>, the accumulator <NUM>, the compressor <NUM>, the <NUM>-way valve <NUM> and the refrigerant piping connection <NUM>. The aforesaid components are disposed in the following order from the refrigerant piping connection <NUM> to the refrigerant piping connection <NUM> considering heating operation (broken arrows in <FIG>): the <NUM>-way valve <NUM>, the accumulator <NUM>, the compressor <NUM>, the <NUM>-way valve <NUM> and the refrigerant piping connection <NUM>.

Furthermore, a refrigerant piping <NUM> connects the first refrigerant piping connection <NUM> and the third refrigerant piping connection <NUM>. The sub-cooling heat exchanger <NUM> is configured to exchange heat between the refrigerant flowing in the refrigerant piping <NUM> and the refrigerant flowing in the refrigerant piping <NUM>. A sub-cooling expansion valve <NUM> is disposed in the refrigerant piping <NUM> between the sub-cooling heat exchanger and the refrigerant piping connection <NUM>. To put it differently, the sub-cooling expansion valve <NUM> is disposed between the connection of the refrigerant piping <NUM> with the refrigerant piping <NUM> and the sub-cooling heat exchanger <NUM>. In any case and during heating and cooling operation, the sub-cooling expansion valve <NUM> is disposed upstream of the sub-cooling heat exchanger <NUM> in the refrigerant piping <NUM>.

A refrigerant piping <NUM> connects the accumulator <NUM> and the <NUM>-way valve <NUM>. Even further, a refrigerant piping <NUM> (gaseous refrigerant piping) connects at one end to the refrigerant piping <NUM> and at the other end to the refrigerant piping <NUM>. Further, a refrigerant piping <NUM> connects the refrigerant piping <NUM> and the refrigerant piping <NUM> with a pressure regulating valve <NUM> being integrated into the refrigerant piping <NUM> at an intermediate position.

The casing <NUM> of the compressor unit <NUM> may be sound insulated so that noise produced by the compressor <NUM> can be prevented from exiting the casing and disturbing individuals inside the building. Further, the casing <NUM> can because of its compact size be disposed on the floor for easy installation and maintenance and even below a cupboard of a kitchen or other technical equipment rooms. The casing <NUM> may additionally comprise feet <NUM> as shown in <FIG> for placing and fixing the casing <NUM> on a horizontal supporting surface. The size of the casing <NUM> particularly relating to its height, widths and depth complies with DIN EN <NUM> for kitchen furniture and kitchen appliances.

An example of an indoor unit <NUM> comprises an indoor heat exchanger <NUM> (second heat exchanger) connected respectively via third and fourth refrigerant piping connections <NUM> and <NUM> and a refrigerant piping to the third and fourth refrigerant connections <NUM> and <NUM> of the compressor unit <NUM>. Optionally, the indoor unit <NUM> may comprise an indoor expansion valve <NUM> disposed between the indoor heat exchanger <NUM> and the third refrigerant piping connection <NUM>. The indoor unit <NUM> may in principle be configured as a common indoor units used in such air-conditioners.

As can be best seen from <FIG>, the air conditioner may be installed in a building <NUM>. In one possible embodiment, the heat source heat exchanger unit <NUM> can be disposed in the ceiling <NUM> of a space <NUM> to be conditioned and being hidden within the ceiling <NUM>. The connections <NUM> and <NUM> are preferably connected to an air duct <NUM> so that the casing <NUM> of the heat source heat exchanger unit <NUM> forms part of the air duct <NUM>. The end of the air duct <NUM> opens at both ends <NUM> and <NUM> to the outside of the building so that outside air may be sucked in through the end <NUM> passes the heat exchanger <NUM> of the heat source heat exchanger unit <NUM> and is exhausted through the end <NUM>.

The heat source heat exchanger unit <NUM> is connected by refrigerant piping <NUM> to the compressor unit <NUM> using the refrigerant piping connections <NUM> and <NUM> as well as <NUM> and <NUM>, respectively. The compressor unit <NUM> again is connected to the indoor unit/-s <NUM> via refrigerant piping <NUM> using the third to fourth refrigerant piping connections <NUM>, <NUM> and <NUM>, <NUM> respectively.

The operation of the air conditioner described above is as follows. During cooling operation (solid arrows in <FIG>), refrigerant flows into the compressor unit <NUM> at the refrigerant piping connection <NUM> passes the <NUM>-way valve <NUM> and is introduced into the accumulator <NUM>. When passing the accumulator associate liquid refrigerant is separated from the gaseous refrigerant and liquid refrigerant is temporarily stored in the accumulator <NUM>.

Subsequently, the gaseous refrigerant is introduced into the compressor <NUM> and compressed. The compressed refrigerant is introduced into the heat source heat exchanger unit <NUM> via the first refrigerant piping connections <NUM>, <NUM> and a refrigerant piping <NUM>. The refrigerant passes the heat exchanger <NUM> with its plates <NUM>, <NUM> of the heat source heat exchanger unit <NUM>, whereby the refrigerant is condensed (the heat exchanger <NUM> functions as a condenser). Hence, heat is transferred to the outside air parallely passing through the heat exchanger elements <NUM>, <NUM> of the heat exchanger <NUM>. The expansion valve <NUM> is entirely opened to avoid high pressure drops during cooling. Then, the refrigerant flows into the compressor unit <NUM> via the third refrigerant piping connections <NUM>, <NUM> and refrigerant piping. In the compressor unit <NUM>, the refrigerant flows in part through the refrigerant piping <NUM> and, hence, the sub-cooling expansion valve <NUM> and the sub-cooling heat exchanger <NUM> and in part through the refrigerant piping <NUM> being introduced via the third refrigerant piping connection <NUM>, a refrigerant piping and the third refrigerant connection <NUM> into the indoor unit <NUM>. The refrigerant is then further expanded by the indoor expansion valve <NUM> and evaporated in the heat exchanger <NUM> (the heat exchanger <NUM> functions as evaporator) cooling the space <NUM> to be conditioned. Accordingly, the heat is transferred from air in the space to be conditioned to the refrigerant flowing through the heat exchanger <NUM>. In cooling the main purpose of the sub-cooling heat exchanger <NUM> is to sub-cool the liquid refrigerant flowing through the refrigerant piping <NUM> to the indoor unit <NUM>. Finally, the refrigerant is again introduced via the fourth refrigerant piping connections <NUM>, <NUM> and refrigerant piping into the compressor unit <NUM>.

As is generally known, the capacity of an air conditioner at the indoor side is the multiplication of enthalpy and mass flow. Hence a reduced mass flow may be used when the enthalpy is increased. The sub-cooling heat exchanger serves to increase enthalpy at the indoor side. As a consequence, the mass flow can be reduced without impairing capacity. As a result the pressure drop in the liquid pipe can be reduced so that the compressor <NUM> needs to deliver less work improving the entire system efficiency.

During heating, this circuit is reversed wherein heating is shown by the broken arrows in <FIG>. The process is in principle the same. Yet, the first heat exchanger <NUM> functions as evaporator whereas the second heat exchanger <NUM> functions as condenser during heating. In particular, refrigerant is introduced into the compressor unit <NUM> via the first refrigerant piping connection <NUM>, flows via the <NUM>-way valve <NUM> into the accumulator <NUM> and is then compressed in the compressor <NUM> before flowing into the <NUM>-way valve <NUM> and through the fourth refrigerant piping connections <NUM>, <NUM> and refrigerant piping into the indoor unit <NUM> and particularly the indoor heat exchanger <NUM> where the refrigerant is condensed (the indoor heat exchanger <NUM> functions as a condenser). Subsequently, the refrigerant is expanded by the expansion valve <NUM> and then reintroduced via the third refrigerant piping interconnections <NUM>, <NUM> into the compressor unit <NUM> where the refrigerant flows into the piping <NUM> and passes the sub-cooling heat exchanger <NUM>. By refrigerant injection after the evaporator, the suction superheat before the compressor can be optimized. As a result, the discharge temperature can be reduced with the beneficial effect of better efficiency of the system and prolonged lifetime. In heating, the sub-cooling heat exchanger <NUM> serves to improve the refrigerant quality at the compressor inlet via the refrigerant piping <NUM> connected to the refrigerant piping <NUM> upstream of the compressor <NUM>, that is on the suction side of thereof. Further, the sub-cooling heat exchanger <NUM> serves to evaporate the two phase refrigerant in the refrigerant piping <NUM> as desired.

Subsequently, part of the refrigerant flows into the refrigerant piping <NUM>, is expanded in the sub-cooling expansion valve <NUM> and flows through the sub-cooling heat exchanger <NUM> before being reintroduced into the refrigerant piping <NUM> upstream of the accumulator <NUM> thereby pre-cooling the refrigerant flowing through the refrigerant piping <NUM> passing the sub-cooling heat exchanger <NUM>. The remaining part flows into the heat source heat exchanger unit <NUM> via the second refrigerant piping connections <NUM> and <NUM> and refrigerant piping. The refrigerant is further expanded by the main expansion valve <NUM> in the heat source heat exchanger unit <NUM> and then evaporated in the heat exchanger <NUM> (the heat exchanger <NUM> functions as evaporator) before being reintroduced into the compressor unit <NUM> via the first refrigerant piping connections <NUM> and <NUM> and refrigerant piping.

Because of the splitting of the compressor unit <NUM> and the heat source heat exchanger unit <NUM>, the compressor unit <NUM> may be installed in areas that are not noise sensitive so that there is no noise disturbance caused by the compressor even though disposed indoors. In addition the casing <NUM> of the compressor unit <NUM> may be well insulated with sound insulation. Even further, there is no compressor noise in the air flowing through the heat source heat exchanger unit <NUM> due to the split concept between the heat source heat exchanger unit <NUM> and the compressor unit <NUM> which could be transferred into the space to be conditioned.

Because of the lower weight per unit of the heat source heat exchanger unit <NUM> and the compressor unit <NUM>, the installation is improved. In addition, the compressor unit <NUM> may be installed on the floor so that there is no need to lift the heavy compressor unit. Because of a relatively small footprint (width and depth) of the compressor unit <NUM> and a lower height of the compressor unit <NUM> and particularly its casing <NUM>, the compressor unit <NUM> may even be hidden when disposed inside the room to be conditioned such as below a cupboard or counter-board.

The heat source heat exchanger unit <NUM> has also the advantage that there is no noise disturbance. Because the compressor is not contained in the heat source heat exchanger unit <NUM> the only sound that can be entrained in the airstream is the noise of the fan whereby the noise in the airstream is drastically reduced. Further, the casing <NUM> can be entirely closed to the space <NUM> to be conditioned so that no sounds are transferred into the space. Also this casing may be well insulated with sound insulation. Because of the lower height of the heat source heat exchanger unit <NUM>, it is easy to hide the unit for example in the ceiling. Therefore, the unit <NUM> is not visible from the outside. The installation is also improved because of the lower weight as compared to units having the compressor in the same casing and because of the lower height of the heat source heat exchanger unit <NUM>. The lower height is particularly assisted by using the "V" shape of the heat exchanger <NUM>, which enables high-efficiency with a relatively low height.

Because of the integration of the sub-cooling unit particularly the sub-cooling heat exchanger into the compressor unit rather than the heat source heat exchanger unit, one long gaseous refrigerant piping connecting the heat source heat exchanger with the suction side of the compressor can be substituted by a shorter line <NUM> contained in the compressor unit. Hence, a large diameter pipe usually required to flow the gaseous refrigerant can be shortened. In other words, an additional route between the heat source heat exchanger unit and the indoor unit can be avoided by placing the sub-cooling heat exchanger in the compressor unit and looping the refrigerant piping connecting the heat source heat exchanger module to the indoor unit through the compressor unit.

If the sub-cooling heat exchanger was disposed in the heat source heat exchanger module and the fluid connection between the units <NUM> and <NUM> would not be looped through the casing <NUM> of the compressor unit <NUM>, but directly connected, a third heat source heat exchanger port was necessary at the compressor unit <NUM> with an additional line connecting the compressor unit <NUM> and the heat source heat exchanger unit <NUM> to implement the line <NUM>. The present embodiment is hence improved as compared to this case with a consequence of easier installation and lower installation costs.

Claim 1:
Heat source unit (<NUM>) for an air conditioner comprising:
a compressor unit (<NUM>) having
a compressor (<NUM>) disposed in a first casing (<NUM>),
first and second heat source heat exchanger unit ports (<NUM>, <NUM>) configured to connect the compressor unit to a heat source heat exchanger (<NUM>) of at least one heat source heat exchanger unit (<NUM>) of the air conditioner,
first and second indoor unit ports (<NUM>, <NUM>) configured to connect the compressor unit to an indoor heat exchanger (<NUM>) of at least one indoor unit (<NUM>) of the air conditioner,
a first refrigerant piping (<NUM>) fluidly connecting the first heat source heat exchanger unit port (<NUM>) and the first indoor unit port (<NUM>),
a sub-cooling heat exchanger (<NUM>) disposed inside the first casing and fluidly connected to the first refrigerant piping for heat transfer with the refrigerant to be flown through the first refrigerant piping,
a second refrigerant piping (<NUM>) fluidly connecting the second heat source heat exchanger unit port (<NUM>) and the second indoor unit port (<NUM>), the compressor (<NUM>) and a <NUM>-way valve (<NUM>) being interposed between the second heat source heat exchanger unit port and the second indoor unit port in the second refrigerant piping, and
a bypass passage (<NUM>) connected to the second refrigerant piping at a suction side of the compressor (<NUM>) between the compressor and the <NUM>-way valve (<NUM>), the sub-cooling heat exchanger (<NUM>) being fluidly connected to the bypass passage (<NUM>) for heat transfer between refrigerant flowing in the bypass passage and refrigerant flowing in the first refrigerant piping (<NUM>), and characterized in that further comprising
a heat source heat exchanger unit (<NUM>) having a heat source heat exchanger (<NUM>), the heat source heat exchanger being disposed in a second casing (<NUM>) separate from the first casing (<NUM>) and being configured to exchange heat with a heat source, wherein the heat source heat exchanger unit is fluidly connected to the compressor unit via the first and second heat source heat exchanger unit ports (<NUM>, <NUM>),
wherein a main expansion valve (<NUM>) of the air conditioner is disposed in the second casing (<NUM>).