Patent Description:
A chiller system is used to chill a process fluid, such as water, which can be used to provide cooling and air conditioning in buildings. A chiller system typically includes a compressor, heat exchangers such as a condenser and an evaporator, and an expansion device forming a refrigeration circuit. Refrigerant vapour is compressed by the compressor and condensed into liquid refrigerant in the condenser. The expansion valve expands the liquid refrigerant to increase its volume and reduce its pressure and become a two-phase refrigerant. The two-phase refrigerant is directed to the evaporator, where heat is transferred from the process fluid to the refrigerant, chilling the process fluid and vaporising the two-phase refrigerant. The refrigerant vapour then returns to the compressor.

The compressor in a chiller system typically has an electric motor to provide the driving force to compress the refrigerant and drive it through the refrigeration circuit. The motor can generate heat during use, and as such, it may be desirable to provide cooling to the compressor and its associated components. The liquid refrigerant at the outlet of the condenser is subcooled prior to passing through the expansion valve to reduce its temperature. It is known to direct a portion of this subcooled refrigerant flow along a cooling line to the compressor to provide cooling to the compressor or other components to be cooled. The refrigerant in this cooling line re-joins the refrigerant circuit at or just upstream of the compressor. This refrigerant is then compressed by the compressor in the refrigeration circuit as described above.

However, the pressure of the subcooled refrigerant can be low compared to the suction pressure of the refrigerant entering the compressor, due to the pressure drop experienced by the refrigerant as it passes through the condenser and losses along the pipeline of the refrigeration circuit. This results in a low pressure differential between the refrigerant pressure in the cooling line and the suction pressure, which means that there is insufficient flow force and speed for the refrigerant in the cooling line and cooling efficiency is reduced. This weak flow can be mitigated by providing an additional pump for refrigerant in the cooling line to increase the pumping head. However, providing an additional pump is expensive and also reduces the energy efficiency of the chiller system.

There is therefore a need to provide an improved chiller system to overcome at least the aforementioned problems.

<CIT> describes an air conditioning device having a refrigerant circuit, a power conversion device including a power module, and a control device that controls the refrigerant circuit and the power conversion device. <CIT> describes an air-cooling type chiller including a plurality of fans and an intermediate device provided between adjacent fans of the plurality of fans. <CIT> describes a refrigerant circuit including a compressor, a heat-source-side heat exchanger, a first expansion device, and a load-side heat exchanger; a plurality of controllers configured to control the refrigerant circuit; a bypass pipe; a second expansion device provided to the bypass pipe, and configured to adjust a flow rate of the refrigerant flowing through the bypass pipe; and a plurality of refrigerant coolers provided to the bypass pipe, and configured to cool the controllers by using the refrigerant the flow rate of which is adjusted by the second expansion device, each of the plurality of refrigerant coolers including a refrigerant cooling pipe and a plate, the refrigerant cooling pipe forming the bypass pipe, the plate being joined between the refrigerant cooling pipe and one of the controllers.

According to a first aspect according to the present invention, there is provided a chiller system comprising: a refrigeration circuit comprising, in flow order, a compressor, a main condenser, an expansion valve and an evaporator; an auxiliary cooling branch configured to receive an auxiliary refrigerant flow from the refrigerant circuit downstream of the compressor, the auxiliary cooling branch bypassing the main condenser, expansion valve and evaporator, the auxiliary branch comprising an auxiliary condenser configured to discharge refrigerant to a cooling line for cooling one or more components of the chiller system; wherein the cooling line is configured to return the portion of refrigerant flow to the refrigeration circuit at or upstream of the compressor; wherein the main condenser and auxiliary condenser are co-located for heat exchange with a common flow of an external heat exchange medium. The auxiliary condenser is located within an installation volume circumscribed by the main condenser. The main condenser comprises a plurality of main heat exchangers spaced apart from one another. The auxiliary condenser is located within the installation volume defined between the main heat exchangers. The main heat exchangers are arranged so that the installation volume extends along a longitudinal axis of the main heat exchangers and has an open axial end which is at least partly closed by the auxiliary condenser.

Each of two adjacent main heat exchangers of the main condenser may be substantially planar and defines a respective plane. The respective planes may be angled relative to each other so that the installation volume has a triangular cross-section.

The auxiliary condenser may have a peripheral profile corresponding to a cross-section of a void of the installation volume defined by the main condenser or corresponding to a shape of an end of the installation volume.

The auxiliary condenser may have a triangular peripheral profile corresponding to the triangular cross-section of the installation volume.

The auxiliary condenser may comprise one of a microchannel heat exchanger (MCHE) and a round-tube plate-fin (RTPF) heat exchanger.

The main condenser may be an air-cooled condenser. The chiller system may comprise a main condenser fan configured to provide an airflow as the common flow through both the main condenser and the auxiliary condenser.

The cooling line may be configured to cool at least one of a motor of the compressor, electronic componentry of the compressor, and a pump. The motor may be internal or external to the compressor.

A controller may be configured to control refrigerant flow around the refrigerant circuit by actuation of a control device such as the expansion valve. The cooling line may bypass the portion of the refrigerant circuit comprising the control device.

The chiller system may be configured so that the refrigerant flow and the auxiliary refrigerant flow are received at the main condenser and the auxiliary condenser, respectively, at the same condenser inlet temperature. The controller may define an operating map of operating conditions for operation of the chiller system. The main condenser and the auxiliary condenser may be configured so that throughout the operating map, a first rate of heat transfer from the refrigerant flow at the main condenser is greater than a second rate of heat transfer from the auxiliary refrigerant flow at the auxiliary condenser.

The controller may be configured to control the discharge of refrigerant to the cooling line by actuation of a solenoid valve.

The chiller system may comprise a calibrated orifice configured to control the discharge of refrigerant to the cooling line.

Except where mutually exclusive, any feature described herein may be applied to any aspect and/or combined with any other features described herein.

<FIG> shows an example chiller system <NUM> according to the present invention. The chiller system <NUM> comprises, in flow order, a compressor <NUM>, a main condenser <NUM>, an expansion valve <NUM>, and an evaporator <NUM>, which are connected by refrigerant lines to form a refrigeration circuit. The compressor <NUM> may be any suitable compressor type, such as a centrifugal compressor, a screw-type compressor, a reciprocating-type compressor, or a scroll-type compressor. The chiller system <NUM> also comprises a non-return valve <NUM> (such as a check valve) downstream of the compressor <NUM> to prevent backflow in the refrigeration circuit.

The chiller system <NUM> comprises a condenser unit <NUM>, including the main condenser <NUM>, an auxiliary condenser <NUM>, and one or more fans <NUM>. In the example of <FIG> (which is in accordance with the present invention), the main condenser <NUM> comprises a plurality of main heat exchangers 22a, 22b. An inlet of each of the plurality of main heat exchangers 22a, 22b is in fluid communication with the outlet of the compressor <NUM> via a discharge line <NUM> of the refrigeration circuit. The main heat exchangers 22a, 22b may have any suitable type of heat exchanger construction, such as microchannel heat exchangers (MCHEs), or round-tube plate-fin (RTPF) heat exchangers. A MCHE typically includes an inlet header, an outlet header and a plurality of flat tubes connecting to and communicating with the headers. Each of the flat tubes has microchannels or small pathways for the refrigerant to pass through, forming microchannel tubes. In a MCHE, refrigerant enters the inlet header and then enters the microchannel tubes. The heat exchangers are configured to conduct heat exchange between refrigerant in the tubes and an external heat exchange medium to provide cooling to the refrigerant within the microchannel tubes. In examples, the microchannel tubes may have thermally conductive fins disposed between the tubes to promote heat transfer between the refrigerant flowing through the tubes and the external heat exchange medium.

The auxiliary condenser <NUM> is formed as a separate heat exchanger to the main condenser <NUM>. The auxiliary condenser <NUM> have any suitable type of heat exchanger construction, and for example may be a round-tube plate-fin (RTPF) heat exchanger or a MCHE. An inlet of the auxiliary condenser <NUM> is also in fluid communication with the outlet of the compressor <NUM>. The auxiliary condenser <NUM> is fluidly coupled to the outlet of the compressor <NUM> via an auxiliary cooling branch <NUM>, which diverts a portion of the refrigerant flow from the discharge line <NUM> to provide an auxiliary refrigerant flow to the auxiliary condenser <NUM>. According to the invention, the auxiliary cooling branch <NUM> connects the auxiliary condenser <NUM> to a point on the discharge line <NUM> downstream of the compressor <NUM> and upstream of the non-return valve <NUM>. However, in other examples, the auxiliary cooling branch <NUM> may connect the auxiliary condenser <NUM> to a point on the discharge line <NUM> which is downstream of the check valve <NUM>. The auxiliary condenser <NUM> is therefore connected in parallel to the main condenser <NUM> in the refrigeration circuit.

The main condenser <NUM> and the auxiliary condenser <NUM> are arranged for heat transfer with an external heat exchange medium to condense the refrigerant flowing through each condenser <NUM>, <NUM>. In this example both the main condenser <NUM> and the auxiliary condenser <NUM> are air-cooled condensers, such that the refrigerant flowing through the main heat exchangers 22a, 22b and the auxiliary condenser <NUM> are arranged for heat transfer with air as the external heat exchange medium. The main condenser <NUM> and the auxiliary condenser <NUM> are co-located within the condenser unit <NUM>, such that a common flow of air provides the external heat exchange medium for both the main condenser <NUM> and the auxiliary condenser <NUM>. The one or more fans <NUM> are configured to provide a flow of air across both the main condenser <NUM> and the auxiliary condenser <NUM> to enable the refrigerant within the condensers to reject heat to the air. Only a single set of one or more fans <NUM> may be required to provide sufficient airflow for heat transfer over both the main condenser <NUM> and the auxiliary condenser <NUM>. Therefore, the inclusion of an auxiliary condenser <NUM> in addition to a main condenser does not necessitate an additional dedicated fan to be provided and thus avoids the additional power consumption and noise that would be generated as a result of having such an additional fan.

In this example, the chiller system <NUM> also comprises a subcooler <NUM> disposed downstream of the main condenser <NUM> (i.e. in fluid communication with the outlet of the main condenser <NUM>). The expansion valve <NUM> is in fluid communication with the subcooler <NUM> and is located downstream of the subcooler <NUM> with respect to the refrigerant flow. In examples, the expansion valve <NUM> may be an electronic expansion valve, an orifice, expander, or the like. In other examples, the chiller system <NUM> may not include a subcooler <NUM>, such that the expansion valve may be in direct fluid communication with the outlet of the main condenser <NUM>.

The evaporator <NUM> is downstream of and in fluid communication with the expansion valve <NUM>. The evaporator <NUM> is configured to provide heat exchange between the refrigerant and a process fluid provided to the chiller system, such as water, to cool the process fluid. The compressor <NUM> is downstream of and in fluid communication with the evaporator <NUM>.

The outlet of the auxiliary condenser <NUM> is connected to a cooling line <NUM>, which carries an auxiliary refrigerant flow exiting the auxiliary condenser <NUM>. The cooling line <NUM> is configured to absorb heat from one or more components <NUM> of the chiller system <NUM>. In this example, the components <NUM> include electronic components of the compressor <NUM>. In other examples, the components <NUM> may include parts of the compressor <NUM>, such as a motor, or any components of the chiller system <NUM> which require cooling when in operation, such as an inverter, or a pump. A valve <NUM> is located on the cooling line <NUM> downstream of the auxiliary condenser <NUM> with respect to the refrigerant flow. The valve <NUM> is configured to selectively discharge refrigerant from the auxiliary condenser <NUM> to the cooling line <NUM> such that the auxiliary refrigerant flow can be provided to the components <NUM> for cooling. The valve <NUM> may be a solenoid valve. In other examples, the system <NUM> may not comprise a valve <NUM> located on the cooling line <NUM>. Instead, the chiller system <NUM> may comprise a calibrated orifice. The calibrated orifice is configured to passively control the refrigerant flow from the auxiliary condenser <NUM> to the cooling line <NUM>. The geometry of the calibrated orifice can be selected to provide the required refrigerant flow rate.

The cooling line <NUM> is connected to the compressor <NUM> to return the auxiliary refrigerant flow to the refrigeration circuit. In other examples, the cooling line <NUM> may be connected to a point upstream of the compressor <NUM> in the refrigeration circuit to return the auxiliary refrigerant flow to the refrigerant circuit (for example, between the evaporator and the compressor). The auxiliary cooling branch <NUM>, which includes the auxiliary condenser <NUM> and the cooling line <NUM>, bypasses the main condenser <NUM>, the expansion valve <NUM>, and the evaporator <NUM>. The auxiliary cooling branch <NUM> therefore provides a parallel refrigerant flow with respect to the refrigerant flow through a party of the refrigeration circuit extending from the main condenser <NUM> to at least the evaporator <NUM> and optionally the compressor <NUM>.

The chiller system comprises a controller <NUM>. The controller <NUM> is configured to control actuation of the expansion valve <NUM> to control the flow of refrigerant through the refrigerant circuit. In this example, the controller <NUM> is configured to control the actuation of the valve <NUM> to selectively control the flow of refrigerant from the auxiliary condenser <NUM> to the cooling line <NUM>. In other examples, when calibrated orifice is used instead of a valve <NUM>, the calibrated orifice is not controlled by the controller. Instead, the calibrated orifice permits refrigerant to flow therethrough in a passive manner.

It will be appreciated that the chiller system <NUM> is an example and can be modified to include additional components. It will also be appreciated that there can be one or more sensors provided at or near the inlet and/or outlets of each of the components in the chiller system. The one or more sensors can be configured to sense or measure one or more properties of the refrigerant, the process fluid, and/or the components. The measured data can be sent to the controller <NUM>, which can use the data to adjust parameters or operating points of the chiller system <NUM>.

In operation, the controller <NUM> is configured to actuate the expansion valve <NUM> to control refrigerant flow around the refrigeration circuit to meet a cooling demand of the chiller system (i.e. via heat exchange at the main condenser). The compressor <NUM> compresses the refrigerant received at the compressor inlet from a relatively lower pressure gas to a relatively higher pressure and temperature at its outlet. The pressure of the refrigerant at the outlet of the compressor <NUM> is referred to as the discharge pressure.

The refrigerant flows through the discharge line <NUM> to the main condenser <NUM>. A portion of the refrigerant flow in the discharge line <NUM> is diverted to the auxiliary condenser <NUM> via the auxiliary cooling branch <NUM> to provide an auxiliary refrigerant flow. The refrigerant flow is condensed in the condenser unit <NUM> by the main condenser <NUM> and the auxiliary refrigerant flow is condensed in the condenser unit <NUM> by the auxiliary condenser <NUM>. Heat from the refrigerant flow and the auxiliary refrigerant flow is transferred to the external air, which is blown across both the main condenser <NUM> and the auxiliary condenser <NUM> by the one or more fans <NUM>. The refrigerant flow and the auxiliary refrigerant flow are thereby cooled. The refrigerant flow and the auxiliary refrigerant flow may be received at the main condenser and the auxiliary condenser, respectively, at the same condenser inlet temperature.

The controller may define an operating map for the chiller system, where the operating map defines a set of operating conditions for the system. For instance, the operating map may define an envelope of operating parameters in which the chiller system is rated and/or permitted to operate. The envelope of operating parameters may be defined by a temperature range of the external heat exchange medium as monitored by a temperature sensor (e.g. ambient air, in the embodiments described above), and/or by a temperature range of the process fluid provided to the evaporator <NUM>, which may be a range of target temperatures, with the controller being configured to operate the chiller system to maintain the process fluid at a set point within the target range. It may be that such a set point is variable within the target range. The operating map may additionally or alternatively be defined by reference to parameters of the refrigerant, such as a discharge temperature of the refrigerant (i.e. upon discharge from the compressor), a discharge temperature of the refrigerant, a suction pressure of the refrigerant (i.e. upon discharge from the expansion valve), a suction temperature or suction saturation temperature of the refrigerant. The operating map limits the conditions in which the chiller system is configured to operate.

The main condenser <NUM> and the auxiliary condenser <NUM> may be configured so that throughout the operating map, a first rate of heat transfer from the refrigerant flow to the air at the main condenser <NUM> is greater than a second rate of heat transfer from the auxiliary refrigerant flow to the air at the auxiliary condenser <NUM>. The relatively higher rate of heat transfer can be determined by the design of the main condenser <NUM> and the auxiliary condenser <NUM>. For example, the main condenser <NUM> may be designed to have a greater heat transfer area than the auxiliary condenser <NUM>, which enables it to transfer heat energy at a greater heat transfer rate across the operating map, or a different construction type which permits a higher heat transfer rate.

The main condenser <NUM> and the auxiliary condenser <NUM> are configured such that main condenser <NUM> causes a first pressure drop in the refrigerant flow, and that the auxiliary condenser <NUM> causes a second pressure drop in the auxiliary refrigerant flow, relative to the discharge pressure. The main condenser is configured so that the first pressure drop is higher than the second pressure drop caused by the auxiliary condenser <NUM>, at the same operating point of the chiller system <NUM>. The chiller system <NUM> is configured to operate at a plurality of operating points, which can be selected according to several factors, including the size of the system and the level of cooling required. At a particular example operating point, the first pressure drop is at least <NUM> kPa and the second pressure drop is no more than <NUM> kPa, for example no more than <NUM> kPa or no more than <NUM> kPa.

The relatively low second pressure drop caused by the auxiliary condenser <NUM> in relation to the first pressure drop caused by the main condenser <NUM> is a result of the configuration of the heat exchangers of the respective condensers. It is common for pressure drops to be specified and considered in the design of a flow system, with manufacturers reporting pressure drops for components to permit suitable components to be selected for particular requirements. Accordingly, the present disclosure does not relate to or include a detailed discussion of how to provide a condenser that provides a lower pressure drop than another condenser. Merely as an example, the pressure drop across a heat exchanger can be affected by factors including flow surface area and flow velocity. Whether for a MCHE or an RTPF heat exchanger, by varying the number, length, and diameter of the tubes through which refrigerant flows, the pressure drop can be varied. For instance, the pressure drop can be reduced by reducing the number of tubes, reducing the length of the tubes, and/or increasing the diameter of the tubes. In addition, reducing the flow velocity through the heat exchanger can reduce the pressure drop through the heat exchanger. As such, the design of the auxiliary condenser can be formulated to achieve the desired low pressure drop relative to the pressure drop caused by the main condenser <NUM>.

As the second pressure drop through the auxiliary condenser is relatively low, the pressure of the auxiliary refrigerant flow at the outlet of the auxiliary condenser <NUM> is relatively closer to the discharge pressure. This means that the pressure of auxiliary refrigerant flow in the cooling line <NUM> is relatively high compared to the suction pressure at the inlet of the compressor <NUM>. Therefore, there is a large pressure differential between the pressure of the auxiliary refrigerant flow in the cooling line <NUM> and the suction pressure, such that refrigerant can flow effectively from the cooling line <NUM> to the compressor <NUM>, without any additional pumping force being required. This ensures that the refrigerant in the cooling line can flow readily to receive heat from the components <NUM> which require cooling, thereby providing good cooling efficiency.

Condensed refrigerant in the auxiliary refrigerant flow exiting the auxiliary condenser is discharged to the cooling line <NUM>. In examples, the geometry of the controller <NUM> is configured to control the actuation of the valve <NUM> to selectively allow the condensed refrigerant to flow along the cooling line <NUM> and to the components <NUM> which require cooling. The refrigerant will absorb heat from the components <NUM>, heating the refrigerant and converting it into a gaseous form. The gaseous auxiliary refrigerant flow then returns to the refrigeration circuit at or upstream of the inlet of the compressor <NUM>.

The condensed refrigerant exiting the main condenser <NUM> flows through the subcooler <NUM> to reduce its temperature. The subcooled refrigerant is then received by the expansion valve <NUM> which reduces its pressure. As a result, a portion of the refrigerant is converted into a gaseous form. The refrigerant flow, which is now in a mixed two-phase form of liquid and gas, flows to the evaporator <NUM>. The refrigerant flows through the evaporator <NUM> and absorbs heat from the process fluid i.e. an internal heat transfer medium of a chiller circuit (e.g. water, air, etc.), thereby heating the refrigerant and converting it into a gaseous form. The gaseous refrigerant then returns to the inlet of the compressor <NUM>. The above process continues while the chiller system <NUM> is operating.

By providing the auxiliary cooling branch <NUM> (having the auxiliary condenser <NUM> and auxiliary refrigerant flow for cooling), a cooling loop which is in parallel to parts of the main refrigeration circuit is established (e.g. parallel to at least the expansion valve and evaporator). Therefore, cooling can be provided to the one or more components <NUM> which require it, without interfering with or disrupting control of the main cooling loop as controlled by actuation of the expansion valve <NUM>.

This can also provide advantageous effects at start up of the chiller system <NUM>. In conventional chiller systems (i.e. those without an auxiliary cooling branch <NUM>), at start up the discharge pressure increases rapidly. It may be necessary to open the expansion valve to mitigate this rapid increase in discharge pressure. However, if components of the chiller system require cooling, there can be a competing requirement to close the expansion valve to ensure that sufficient subcooling is provided to the refrigerant leaving the main condenser so that it can be used for such cooling. These two actions are antagonistic and therefore lead to compromises in system performance or risk damage or low performance issues. The chiller system <NUM> of the present disclosure avoids such issues by providing the auxiliary cooling branch <NUM> which is in parallel to the main refrigeration circuit and bypasses the main condenser <NUM>, expansion valve <NUM> and evaporator <NUM>. This means that the cooling of one or more components <NUM> of the chiller system <NUM> is not affected by the need to open the expansion valve <NUM> to a large extent during start up.

The auxiliary cooling branch <NUM> also serves as a liquid receiver volume which can be advantageous for providing liquid cooling. For example, upon system start up, components of the chiller system <NUM> may have a cooling demand to prevent rapid temperatures rise. The chiller system <NUM> of the present disclosure enables this rapid cooling to be provided at start up by maintaining a buffer or reserve supply of cooled liquid refrigerant downstream of the auxiliary condenser <NUM>. This supply can be provided by the internal volume of the auxiliary cooling branch, for example comprising the associated pipework downstream of the auxiliary condenser <NUM>, which enables a portion of cooled refrigerant to be stored. The auxiliary cooling branch <NUM> may further comprise a tank to store a portion of cooled refrigerant exiting the auxiliary condenser <NUM>. The stored refrigerant in the buffer can be used to provide rapid cooling to components of the chiller system <NUM> upon start up.

<FIG> schematically shows an example condenser unit <NUM>. The condenser unit <NUM> comprises three condenser modules <NUM>, <NUM>', <NUM>". In other examples, the condenser unit <NUM> may include any number of condenser modules. The condenser modules <NUM>, <NUM>', <NUM>" are supported by a frame <NUM>. It will be appreciated that similar reference numerals for each of the condenser modules <NUM>, <NUM>', <NUM>" indicates that similar features are present.

Each condenser module <NUM>, <NUM>', <NUM>" comprises a main condenser <NUM>, <NUM>', <NUM>". The main condenser <NUM>, <NUM>', <NUM>" comprises two main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b". The main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b" are arranged to be spaced apart from one another. The main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b" are substantially planar. The main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b" may be microchannel heat exchangers (MCHEs), or round-tube plate-fin (RTPF) heat exchangers, as described previously. Each main heat exchanger 22a, 22b; 22a', 22b'; 22a", 22b" has a respective inlet 32a, 32b; 32a', 32b', 32a", 32b", through which refrigerant from the discharge line enters the heat exchanger. Each of the main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b" of each condenser module <NUM>, <NUM>', <NUM>" has respective outlets, which are manifolded to a common outlet <NUM>, <NUM>', <NUM>". The common outlet <NUM>, <NUM>', <NUM>" is configured to discharge condensed refrigerant downstream towards the expansion valve <NUM>. The outlets <NUM>, <NUM>', <NUM>" for the main condenser <NUM>, <NUM>', <NUM>" for each of the plurality of condenser modules <NUM>, <NUM>', <NUM>" may be manifolded to a common outlet manifold.

At least one of the condenser modules <NUM>, <NUM>', <NUM>" comprises an auxiliary condenser <NUM>, <NUM>". As In this example, the first and third condenser modules <NUM>, <NUM>" (seen from left to right in <FIG>) comprise a respective auxiliary condenser <NUM>, <NUM>". In other examples, all of the condenser modules in the condenser unit may have an auxiliary condenser. As described previously, the auxiliary condenser <NUM>, <NUM>" may be a microchannel heat exchanger (MCHE), or a round-tube plate-fin (RTPF) heat exchanger. The auxiliary condenser <NUM>, <NUM>" has an inlet <NUM>, <NUM>", through which refrigerant from the discharge line enters. The auxiliary condenser <NUM>, <NUM>" has an outlet <NUM>, <NUM>" through which condensed refrigerant exits to the cooling line <NUM>. The outlets <NUM>, <NUM>" for the respective auxiliary condensers of the plurality of condenser modules may be manifolded to a common outlet manifold.

Each condenser module <NUM>, <NUM>', <NUM>" comprises at least one fan <NUM>, <NUM>', <NUM>". The fan <NUM>, <NUM>', <NUM>" is configured to force airflow <NUM> through and across the main condensers <NUM>, <NUM>', <NUM>" and the auxiliary condensers <NUM>, <NUM>" such that refrigerant flowing through the condensers can transfer heat to the airflow <NUM>.

<FIG> shows an isometric view of the condenser unit <NUM> of <FIG>, with the fans not shown for ease of understanding. The auxiliary condenser <NUM>, <NUM>" of each condenser module <NUM>, <NUM>', <NUM>" is located within an installation volume <NUM>, <NUM>', <NUM>" circumscribed by the respective main condenser <NUM>, <NUM>', <NUM>". The installation volume <NUM>, <NUM>', <NUM>" relates to the three-dimensional space present in the gap between the main heat exchangers of a condenser module. As shown in both <FIG> and <FIG>, the auxiliary condenser <NUM>, <NUM>" is located within the installation volume <NUM>, <NUM>', <NUM>" defined by the space between the main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b". In this example, each of the main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b" is formed in a substantially planar shape. As a result, each main heat exchanger 22a, 22b; 22a', 22b'; 22a", 22b" defines a respective plane. In this example, the two main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b" of each condenser module <NUM>, <NUM>', <NUM>" are arranged such that their respective planes are angled with respect to each other. In this example, the respective planes are arranged to define an acute angle with respect to each other. The main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b" are therefore arranged in a "V"-shape. In other examples, the main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b" may be arranged in any suitable configuration, such as to form an "A"-shape. In further examples, the main condenser <NUM>, <NUM>', <NUM>" may comprise four such main heat exchangers that are arranged in a "W"-shape.

As a result of being angled with respect to one another, the installation volume <NUM>, <NUM>', <NUM>" circumscribed by the main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b" has a triangular cross section in the particular example shown. The installation volume <NUM>, <NUM>', <NUM>" extends along a longitudinal axis of the main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b". As shown in <FIG>, the installation volume has a shape resembling a triangular prism. The main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b" are arranged such that the installation volume <NUM>, <NUM>', <NUM>" has at least one open axial end. The auxiliary condenser has a peripheral profile which corresponds to the cross-section of a void of the installation volume <NUM>, <NUM>', <NUM>" or which corresponds to a shape of an end of the installation volume <NUM>, <NUM>', <NUM>". In this example, the auxiliary condenser <NUM>, <NUM>" has a triangular peripheral profile, which corresponds to both the triangular cross-section of the void of the installation volume <NUM>, <NUM>', <NUM>" and the triangular shape formed at the end of the installation volume <NUM>, <NUM>', <NUM>". The auxiliary condenser <NUM>, <NUM>" is disposed at an axial end of the installation volume <NUM>, <NUM>', <NUM>", so as to at least partially close the open axial end. In other examples, the auxiliary condenser <NUM>, <NUM>" may be disposed at any axial position along the axial length of the installation volume <NUM>, <NUM>', <NUM>". In further examples, there may be a plurality of auxiliary condensers <NUM>, <NUM>" disposed at respective axial positions along the axial length of the installation volume <NUM>, <NUM>', <NUM>". The auxiliary condenser <NUM>, <NUM>" may be secured in position to the frame <NUM> and/or to the main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b" with the use of any suitable fixing means, for example using fasteners. By disposing the auxiliary condenser <NUM>, <NUM>" with an installation volume <NUM>, <NUM>', <NUM>" formed by the space between main heat exchangers 22a, 22b; 22a', 22b'; 22a", 22b", the present arrangement utilises space with is otherwise left unused in a conventional condenser unit. Therefore, space is used in an efficient manner, such that the condenser unit <NUM> has a compact construction. In addition, this removes the need for the auxiliary condenser <NUM>, <NUM>" to be housed in a separate unit to the main condenser <NUM>, <NUM>', <NUM>". This enables the main condenser <NUM>, <NUM>', <NUM>" and the auxiliary condenser <NUM>, <NUM>" to share the airflow generated by the fan <NUM>, <NUM>', <NUM>" for external heat exchange.

<FIG> schematically shows a view of a second example condenser unit <NUM>. The second example condenser unit <NUM> comprises similar features to that of the first example condenser unit <NUM>, with like reference numerals indicating like features. The second example condenser unit <NUM> differs from the first example condenser unit <NUM> in the arrangement of the main heat exchangers and the peripheral profile of the auxiliary condenser.

The condenser unit <NUM> comprises a condenser module <NUM>. In this example, only a single condenser module <NUM> is shown, however, in other examples a plurality of condenser modules <NUM> may be present in the condenser unit <NUM>. The condenser module comprises a main condenser <NUM>. The main condenser <NUM> comprises two main heat exchangers 222a, 222b. The main heat exchangers 222a, 222b are arranged to be spaced apart from one another. In this example, the main heat exchangers 222a, 222b are spaced apart vertically from one another. The main heat exchangers 222a, 222b are supported by the frame <NUM>.

The condenser module <NUM> also includes an auxiliary condenser <NUM>. The auxiliary condenser <NUM> is disposed between the main heat exchangers 222a, 222b. Both the main heat exchangers 222a, 222b and the auxiliary condenser <NUM> have refrigerant inlet and outlet arrangements similar to those described with reference to the first example condenser unit <NUM>. The condenser module <NUM> also comprises at least one fan <NUM>. The fan <NUM> is configured to force airflow <NUM> upwards through and across the main condenser <NUM> and the auxiliary condenser <NUM> such that refrigerant flowing through the condensers can transfer heat to the airflow <NUM>. As with the first example condenser unit, the main heat exchangers 222a, 222b and the auxiliary condenser <NUM> may be microchannel heat exchangers (MCHE), or a round-tube plate-fin (RTPF) heat exchangers.

The main heat exchangers 222a, 222b are each formed in a substantially planar shape. As a result, each main heat exchanger 222a, 222b defines a respective plane. In this example, the main heat exchangers 222a, 222b are arranged such that their respective planes are parallel with respect to each other. As such, the installation volume circumscribed by the space between the main heat exchangers has a rectangular cross-section. The installation volume extends along the axial length of the main heat exchangers 222a, 222b. The installation volume therefore resembles a cuboid extending along the length of the main heat exchangers 222a, 222b.

Claim 1:
A chiller system (<NUM>) comprising:
a refrigeration circuit comprising, in flow order, a compressor (<NUM>), a main condenser (<NUM>, <NUM>', <NUM>", <NUM>), an expansion valve (<NUM>) and an evaporator (<NUM>);
an auxiliary cooling branch (<NUM>) configured to receive an auxiliary refrigerant flow from the refrigerant circuit downstream of the compressor (<NUM>), the auxiliary cooling branch (<NUM>) bypassing the main condenser (<NUM>, <NUM>', <NUM>", <NUM>), expansion valve (<NUM>) and evaporator (<NUM>), the auxiliary branch comprising an auxiliary condenser (<NUM>, <NUM>", <NUM>) configured to discharge refrigerant to a cooling line (<NUM>) for cooling one or more components (<NUM>) of the chiller system (<NUM>);
wherein the cooling line (<NUM>) is configured to return the portion of refrigerant flow to the refrigeration circuit at or upstream of the compressor (<NUM>);
wherein the main condenser (<NUM>, <NUM>', <NUM>", <NUM>) and auxiliary condenser (<NUM>, <NUM>", <NUM>) are co-located for heat exchange with a common flow of an external heat exchange medium;
characterised in that the main condenser (<NUM>, <NUM>', <NUM>", <NUM>) comprises a plurality of main heat exchangers (22a, 22b, 222a, 222b) spaced apart from one another;
wherein the auxiliary condenser (<NUM>, <NUM>", <NUM>) is located within an installation volume (<NUM>, <NUM>', <NUM>") circumscribed by the main condenser (<NUM>, <NUM>', <NUM>", <NUM>) and defined between the main heat exchangers (22a, 22b, 222a, 222b); and
wherein the main heat exchangers (22a, 22b, 222a, 222b) are arranged so that the installation volume (<NUM>, <NUM>', <NUM>") extends along a longitudinal axis of the main heat exchangers (22a, 22b, 222a, 222b) and has an open axial end which is at least partly closed by the auxiliary condenser (<NUM>, <NUM>", <NUM>).