GB2616652A

GB2616652A - A heat exchanging unit

Info

Publication number: GB2616652A
Application number: GB2203693.3A
Authority: GB
Inventors: White Bryan
Original assignee: White Heating Consultancy Ltd
Current assignee: White Heating Consultancy Ltd
Priority date: 2022-03-17
Filing date: 2022-03-17
Publication date: 2023-09-20
Anticipated expiration: 2042-03-17
Also published as: GB2616652B; GB202203693D0

Abstract

A heat exchanging unit 10 for exchanging heat between a first fluid circuit and a second fluid circuit of a heating system, the heat exchanging unit comprises a base 12 with a reservoir 20 to be filled with the first fluid provided on the base, a heat exchanger 30 that exchanges heat between the first and second fluid circuits supported on the base. A plurality of first tubes 40, 42, 44 are arranged to provide fluid communication between the first fluid circuit and both the heat exchanger and the reservoir, and a plurality of second tubes 50, 52 arranged to provide fluid communication between the second fluid circuit and the heat exchanger. The plurality of second tubes and at least one of the first tubes can extend through the reservoir. The heat exchanger may be supported on the reservoir by the plurality of first and second tubes. The heat exchanger unit may be mounted under a hot water tank (102, fig 1) of a central heating system.

Description

A HEAT EXCHANGING UNIT

Field

The present application relates to a heat exchanging unit, and in particular to a heat exchanging unit for exchanging heat between a first fluid circuit and a second fluid circuit of a heating system.

Background

Air-source heat pumps have gained prominence in the last decade as a primary 113 heat source for domestic central heating systems. Their increasing use is largely driven by high energy efficiencies, as well as various government incentives that promote phasing out of conventional gas/oil heating systems. Moreover, in contrast to combustion-based heating systems, air-source heat pumps do not pose a fire risk, nor do they emit greenhouse gases during use.

In comparison to ground-source (geothermal) heat pumps that typically require a significant footprint or borehole depth for extracting heat from the ground, air-source heat pumps comprise a relatively compact outdoor unit for extracting heat from the environment, making them a favourite for homeowners. In use, the extracted heat energy is transferred to indoor radiators or underfloor heaters by a heat transfer fluid, often comprised of an antifreeze such as glycol for preventing freezing in the outdoor unit and its associated pipeworks during winter months.

The performance of air-source heat pumps is susceptible to seasonal temperature changes. In the search for better seasonal coefficient of performance figures, manufacturers are continuously making the systems more complicated, as well as developing their installation methods. Not only do these increase the installation cost, if the system is not properly understood by the heating engineer it may result in a poor installation, thereby negatively impacting the performance of the heat pumps. Furthermore, heat pumps typically have a limited life span of 10 years before a complete removal and reinstallation is required. This may represent a significant challenge for heating engineers when fitting a new generation of heat pumps to existing heating systems.

In basic heating systems, a single fluid circuit may be provided which allow the heat transfer fluid to circulate both indoor and outdoor fluid circuits. However, such an arrangement requires a large amount of antifreeze and thus contributes to higher installation and maintenance costs. Moreover, when circulating in the central heat system, the antifreeze fluid may easily get contaminated by rust and other particulate matters, which can potentially cause heat pump failures.

In more advanced systems, a heat exchanger may be provided to exchange heat between an antifreeze filled outdoor fluid circuit and an indoor fluid circuit having water circulating therein, thus significantly reducing the amount of antifreeze required and prolonging the longevity of the antifreeze fluid. Furthermore, the two fluid circuits are fluidly decoupled, thus limiting fluid drainage when installing/replacing a heat pump system. However, such advanced systems increase the complexity of installation and often requires a separate buffer tank for the outdoor fluid circuit. This may prove difficult in some cases when the buffer tank is required to be installed in a confined space such as an airing cupboard or a plant room.

Therefore, a heat transferring unit that is compact, adaptable for use with a large variety of air-source heat pumps, whilst facilitating efficient installation is highly desirable.

Summary

The present invention offers a single heat exchanging unit that combines a heat exchanger and a buffer tank. Such an arrangement may allow a heat pump to be coupled to a heating system more efficiently. Moreover, the heat exchanging unit may present a generic solution to a heat pump installation, thereby reducing the cost of future heat pumps replacements. Furthermore, the compact design of the heat exchanging unit may allow it to be installed underneath an existing hot water cylinder to conserve space.

According to a first aspect of the presently-claimed invention, there is provided a heat exchanging unit for exchanging heat between a first fluid circuit and a second fluid circuit of a heating system, the heat exchanging unit comprising: a base; a reservoir provided on the base, the reservoir is arranged to be filled with a first fluid circulating the first fluid circuit; a heat exchanger supported on the base, the heat exchanger is arranged to exchange heat between the first fluid circulating the first fluid circuit and a second fluid circulating the second fluid circuit; and a plurality of first tubes arranged to provide fluid communication between the first fluid circuit and both the heat exchanger and the reservoir, and a plurality of second tubes arranged to provide fluid communication between the second fluid circuit with the heat exchanger.

One of the first and second fluid circuits may connect a ground-source, or air-source heat pump, or other heat sources, to the heat exchanger, and may be responsible for transferring heat energy from the outdoor heat pump into an indoor space. It may be subject to seasonal temperature changes. Thus, the fluid circulating the said fluid circuit may comprise an antifreeze. In some cases, particularly where the heat pump is installed at locations with mild weather, the said fluid may be dispensed with antifreeze.

The other one of the first and second fluid circuits may form part of a central heating system. That is, the said fluid circuit may be a network of indoor pipeworks that connects radiators and/or underfloor heating systems to a heat source (e.g. the heat exchanger). The said fluid circuit may not expose to the environment and therefore the fluid circulating therein may not comprise an antifreeze, e.g. the second fluid may be water.

In use, heat generated by the heat pump may be transferred to the central heating system, through heat exchange between the first and second fluid circuits at the heat exchanger. Thus, the first and second fluid may not come into direct contact with each other.

The reservoir may be a buffer tank or a volumiser, having an internal volume that holds an amount of first fluid, which may serve to reduce the risk of heat pump short cycling, as well as allow for fluctuations in the first fluid circuit under different operating conditions and losses due to leaks and evaporation. In addition, the first fluid stored in the reservoir may be used for carrying out a heat pump defrost cycle required by some heat pumps. The reservoir may be sealed from the environment. The reservoir may be provided with a valve for filling or discharging the first fluid in the reservoir. During use, the reservoir may be fully filled with the first fluid. The reservoir may comprise, towards its upper end, an air vent for venting gas accumulated in the reservoir. The air vent may be an automatic air vent of a manual air vent.

The reservoir may form together with the base, e.g. the upper surface of the base may serve as the floor of the tank. Alternatively, the reservoir may form separately to the base and it may be directly or indirectly mounted to the said base.

The reservoir may be connected with the first fluid circuit and the heat exchanger by a plurality of first tubes. More specifically, the reservoir may be fluidly connected, in series, to the first circuit by one of the first tubes and to a first inlet or a first outlet of the heat exchanger by another one of the first tubes.

The heat exchanger is preferably a plate heat exchanger or it may be other suitable liquid/liquid heat exchangers such as a shell-and-tube heat exchanger.

The heat exchanger may comprise a single heat exchanger or a plurality of heat exchangers in serial or parallel connection. The heat exchanger preferably adapts a concurrent flow arrangement but in some cases, it may adopt a countercurrent flow arrangement. The heat exchanger may be supported on the base by the reservoir or other parts of the heat exchanging unit, or it may mount directly onto the base.

The heat exchanger may further comprise another one of the first inlet or first outlet fluidly connecting to the first fluid circuit by a first tube, and a second inlet and second outlet fluidly connected to the second fluid circuit by a plurality of second tubes.

In some embodiments, the first fluid circuit may fluidly connect with the heat pump. Therefore the first fluid in the reservoir may comprise an antifreeze, e.g. an antifreeze or a mix of water and antifreeze.

In some other embodiments, the first fluid circuit may fluidly connect with central heating system. Therefore the first fluid in the reservoir may be in absence of an antifreeze, e.g. water and/or an anti-rust/scale agent.

Advantageously, the heat exchanger and the reservoir may be supplied as a single heat exchanging unit, thereby enabling an efficient installation. Furthermore, depending on its connections, the reservoir may provide buffering capacity for the antifreeze associated with the heat pump or the water circulating the central heating system, thus it is versatile for use with heat pumps from different manufacturers (e.g. some heat pumps may require the provision of a buffer tank whilst others may not).

Optionally, the plurality of first and second tubes extend through a sidewall of the reservoir. For example, the first and second tubes may extend into the internal volume of the reservoir. During use, the plurality of first and second tubes may be at least partially, or fully, immersed in the first fluid in the reservoir. For example, the plurality of the second tubes and at least one of the first tubes may extend through the reservoir and may be fluidly sealed from the first fluid in the reservoir. Such an arrangement increases the available heat transfer area, thereby advantageously improving heat transfer between the first and second. In some cases, the first and/or second tubes may be provide with an additional heat exchanger, such as a coil heat exchanger, inside the reservoir to further increase the available heat transfer surface.

Optionally, the heat exchanger may be supported on the reservoir by the plurality of first and second tubes. Preferably, the heat exchanger is supported on a side of the reservoir by the first and second tubes. In some other embodiment, the heat exchanger may be supported on top the reservoir by the first and second tubes. Advantageously, such an arrangement result in a more compact heat exchanging unit or allow the provision of a larger heat exchanger. Furthermore, such an arrangement may simplify the manufacturing and/or installation because the heat exchanger is fixed in place during the plumbing process.

Optionally, one of the first tubes comprises an opening inside the reservoir to provide fluid communication between the first fluid circuit and the reservoir. For example, the said first tube may comprise two open-ended segments (e.g. the first return tube and the reservoir return tube) extending through opposing sidewalls of the reservoir. The two open-ended segments may be provided towards a lower end of the reservoir. Such an arrangement may promote the circulation of the first fluid in the reservoir, as well as to minimise the formation of a stagnant flow. To aid circulation, a baffle may be provided in the reservoir to disrupt the flow of the first fluid therein. Alternatively, the said first tube may comprise a single tube (combining the first return tube and the reservoir return tube) having one or more orifices opened along the tube for providing fluid 113 communication. Such an arrangement may simplify the manufacturing process.

Alternatively, some or all of the plurality of the second tubes and at least one of the first tubes are routed away from the reservoir. That is, in these embodiments, only the first tubes associated with the reservoir is physically and fluidly connected therewith. In these embodiments, the heat exchanger may be mounted, directly or indirectly, onto the base. By decoupling the heat exchanger and the reservoir, such an arrangement may reduce the difficulty of replacing/servicing each component.

Optionally, the reservoir further comprises an auxiliary heating element configured to heat the first fluid inside the reservoir. More specifically, the auxiliary heating element may serve as a backup heater upon an occurrence of an abnormality in the first fluid circuit, e.g. blockage in the first fluid circuit, heat pump malfunction or a reduction in heat extraction from the environment due to seasonal changes.

Preferably, the auxiliary heating element is provided in embodiments where the first fluid circuit forms part of the central heating system, e.g. the auxiliary heating element may provide backup heating for the water circulating in the central heating system.

Optionally, the heat exchanging unit further comprises a controller for controlling the auxiliary heating element, wherein upon receiving a signal indicating an abnormality in the first fluid circuit, the controller controls the auxiliary heating element to heat the first fluid inside the reservoir. The signal may be generated by the heat pump, by a sensor in the first and/or second fluid circuits, by user input, or by another controller associated with the central heating system. The signal may be transmitted to the controller wirelessly, by physical wirings, or by a user interface at the heat exchanging unit.

Optionally, the first fluid is arranged to have a different freezing point to that of the second fluid. For example, one of the first fluid or the second fluid that is associated with the outdoor heat pump may be arranged to comprise one or more of glycol and glycerol, or other suitable antifreeze.

Optionally, the reservoir having an internal volume of less than 0.03m3, or less than 0.02m3, or less than 0.01m3. Preferably, the reservoir having an internal volume of 0.02m3, as typically required by some heat pumps.

Optionally, the reservoir having a height of less than 0.3m, or less than 0.2m, or less than 0. lm. Preferably, the reservoir having a height of 0.25m, which is the typical elevation of domestic hot water cyclinders.

Opitonally, the heat exchanging unit is configured to be installed, by the base, at a location beneath an insulated hot water cylinder of a central heating system. For example, the external dimension of the heat exchanging unit is sized to fit into a space that typically exists underneath a hot water cylinder. Advantageously, such an arrangement may eliminate the need for seeking suitable installation space in an airing cupboard, which often comes at a premium.

Optionally, the base having substantially the same cross-section profile and dimension as the insulated hot water cylinder. For example, the base may be circular, and the diameter of the base ranges from 0.4m to 0.6m. Preferably, the diameter of the base is 0.52m.

According to a second aspect of the presently-claimed invention, there is provided a heat exchanging unit for exchanging heat between a first fluid circuit and a second fluid circuit of a heating system, the heat exchanging unit comprising: a reservoir arranged to be filled with a first fluid circulating the first fluid circuit; a heat exchanger arranged to exchange heat between a first fluid circulating the first fluid circuit and a second fluid circulating the second fluid circuit; and a plurality of first tubes arranged to provide fluid communication between the first fluid circuit and both the heat exchanger and the reservoir, and a plurality of second tubes arranged to provide fluid communication between the second fluid circuit and the heat exchanger; wherein the plurality of the second tubes and at least one of the first tubes extend through the reservoir.

Advantageously, such an arrangement increases the available heat transfer area, thereby improving heat transfer between the first and second fluid inside the 10 reservoir.

Optionally, during use, the plurality of first and second tubes are at least partially, or fully, immersed in the first fluid in the reservoir.

Optionally, one of the first tubes comprises two open-ended segments extending through opposing sidewalls of the reservoir so as to provide fluid communication between the reservoir and the first fluid circuit.

Optionally, the heat exchanging unit further comprises a base on which the reservoir and the heat exchanger are supported.

According to a thrid aspect of the presently-claimed invention, there is provided a heating system, comprising: a first fluid circuit and a second fluid circuit; and the heat exchanging unit of the first aspect or the second aspect for exchanging heat between the first and second fluid circuits.

Optionally, one of the first and second fluid circuits is connected with a heat pump and the other one of the first and second fluid circuits forms part of a central heating system.

According to a fourth aspect of the presently-claimed invention, there is provided a heat exchanging unit of the first aspect or the second aspect to form a heating system, comprising the step of: installing the heat exchanging unit, by the base, at a location beneath a hot water cylinder; and connecting the plurality of first and second tubes to the respective first and second fluid circuits.

Features from any one of the first to the fourth aspects of the present invention may be applicable with any other feature from the other aspects.

Brief Description of the Drawings

Certain embodiments of the presently-claimed invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a heating system according to a first embodiment of the present invention; Figure 2 is a plan view of a heat exchanging unit installed in the heating system of Figure 1; Figure 3 is a side view of a heat exchanging unit of Figure 2; Figure 4 is a schematic diagram of a heating system according to a second embodiment of the present invention; Figure 5 is a plan view of a heat exchanging unit installed in the heating system of Figure 4; and Figure 6 is a side view of a heat exchanging unit of Figure 5.

Detailed Description

Figure 1 is a schematic diagram of a heating system 100 according to a first embodiment of the present invention. Figures 2 and 3 are respectively a plan view and a side view of a heat exchanging unit 10 installed in the heating system 100. In order to display its internal components, the heat exchanging unit 10 is shown without coverings (e.g. a top cover and a shroud) but they are nevertheless present.

Heating system Referring to Figure 1, the heating system 100 comprises a heat pump 110 and a central heating system 150 respectively connected to an antifreeze circuit 112 and an indoor circuit 152. In this context, the phrase 'circuit' generally means a network of pipes or tubes that allow fluid to circulate between different components. In use, the heat pump 110 serves as a primary heat source for the central heating system 150, through heat exchange between the two fluid circuits 112, 152 at the heat exchanging unit 10.

The heat pump 110 is an outdoor air-source heat pump for extracting heat energy from the environment. The output of the heat pump 110 ranges between 4kW to 12kW depending on the heating demand. The heat pump 110 is fluidly connected to the heat exchanging unit 10 by the antifreeze circuit 112. Since the heat pump 110 and a part of the antifreeze circuit 112 are exposed to the outdoor environment, the fluid circulating the antifreeze circuit 112 comprises an antifreeze, such as glycol. More specifically, the antifreeze fluid circulating the antifreeze circuit comprises a mixture of water and glycol, with a glycol contentraction ranging from 10 -50% by volume. This reduces the risk of fluid freezing during the winter months.

In the illustrated example as shown in Figures 1-3, heat pump 10 requires a buffer tank for storing an additional amount of antifreeze for carrying out a heat pump defrost cycle. The amount of additional antifreeze required is 20L as typically required by some heat pumps.

The antifreeze circuit 112 comprises a forward flow section 112a responsible for transferring heated antifreeze fluid from the heat pump 110 to the heat exchanging unit 10 and a conventional coil heat exchanger (not shown) disposed in a hot water cylinder 102. More specifically, the forward flow section 112a comprises a diverter valve 114 for controlling the allocation of heated antifreeze fluid between the heat exchanging unit 10 and the coil heat exchanger depending on their needs.

Similar to a convention installation associated with an unvented hot water cylinder 102, the part of forward flow section 112a connected to the hot water cylinder 112a is provided with an automatic air vent 116 for bleeding air from the antifreeze circuit 112.

Once it has dissipated its heat energy at the heat exchange unit 10 or the coil heat exchanger, the cooled antifreeze fluid is returned, by a return flow section 112b, to the heat pump to be reheated. The return flow section 112b comprises a filling valve 114, which allows topping up of the antifreeze fluid in the antifreeze circuit 112.

Some heat pumps may be supplied with a pump for driving the antifreeze fluid through the antifreeze circuit 112, as well as a pressure vessel for absorbing its thermal expansion. In cases where a pump or a pressure vessel is not supplied in the heat pump, they may be respectively installed in the forward flow section 112a and the return flow section 112b of the antifreeze circuit 112. The location of the pressure vessel and the pump, as provided in the heat pump or in their respective fluid circuits, are shown in dotted lines in Figure 1.

The central heating system 150, on the other hand, refers to a network of radiators and/or underfloor heating systems. The central heating system 150 is a conventional central heating system. However, instead of using a gas/oil boiler as a heat source, the central heating system 150 is connected to the heat exchanging unit 10 by the indoor circuit 152. Since the indoor circuit 152 is shielded from the environment, an antifreeze is not required. Thus, the fluid circulating the indoor circuit 152 mainly consists of water, and optionally comprises additives such as 3o rust and scale inhibitors.

The indoor circuit 152 comprises a forward flow section 152a responsible for transferring heated water from the heat exchanging unit 10 to various radiators and/or underfloor heating systems in the central heating system 150. The forward flow section 152a comprises a pump 160 for driving water flow through the central heating system 150.

Once it has dissipated its heat energy at the central heating system 150, the cooled water is returned, through a return water flow section 152b, to the heat exchanging unit 10 to be reheated. The return water flow section 152b further comprises a pressure vessel 162 for absorbing thermal expansion in the water and a filling valve 164 for topping up the water in the indoor circuit 12.

Heat Exchanging Unit Referring to Figures 2 and 3, the heat exchanging unit 10 comprises a base 12 onto which all of the components of the heat exchanging unit 10 are supported. The base 12 is a planar element having a circular shape that corresponds with a cross-sectional profile of a conventional hot water cylinder typically installed in a central heating system.

The heat exchanging unit 10 further comprises a reservoir 20 supported on the base. The reservoir 20 is formed by vertical sidewalls extending from an upper surface of the base 12. That is, the upper surface of the base 12 forms a floor of the reservoir 20. In this particular embodiment, the reservoir 20 primarily serves as a holding vessel for containing an amount of antifreeze additionally required by the heat pump when it carries out a defrost cycle. The reservoir 20 has an internal volume of 20L in the given example but it may be different in other embodiments depending on their needs, e.g. as required by the heat pump. The reservoir 20 has a footprint that is smaller than the base 20 to allow for other components to be coplanarly installed onto the base 20.

A top cover (not shown), having a similar dimension to the base 12, is provided on top of the vertical sidewalls to seal the internal volume of the reservoir 20 from the environment. During use, the reservoir 20 is configured to be fully filled with the antifreeze fluid. An automatic air vent 28 is provided towards an upper end of the reservoir 20 for venting gas (e.g. air) accumulated in the reservoir 20. In addition, a vertical shroud (not shown) may provide circumferentially around the heat exchanging unit 10 to cover or shield the components. Thus, the fully assembled heat exchanging unit 10 resembles a cylinder.

The external and/or internal surfaces of the top cover, the base and the top cover are provided with a layer of thermal insulation (not shown) where applicable. The thermal insulation may be any suitable thermal insulation such as cellulose material, mineral wool, fibreglass or rigid foam such as polystyrene and polyurethane foam.

The reservoir 20 comprises an orifice 24 opened on its sidewall for optional installation of an auxiliary immersion heater to serve as a backup heat source in the event of heat pump malfunction. In installations where an immersion heater is not installed, as in the present example, the orifice 24 may be sealingly closed by a plug.

The heat exchanging unit 10 further comprises a heat exchanger 30. In the illustrated embodiment the heat exchanger 30 is a plate heat exchanger (Nordic TEC Ba-16-22 having a heat exchange surface of 0.352m2). The heat exchanger 30 is formed from plural stacked corrugated metal plates between which multiple flow channels are created. The heat exchanger 30 comprises a first inlet 38 and a second inlet 36 fluidly connected to respectively a first outlet 32 and a second outlet 34 through the flow channels. The inlets 36,38 and outlets 32,34 are provided on the opposite sides of the heat exchanger 30, thus the heat exchanger 30 is a concurrent current heat exchanger. In other embodiments, a counter-current flow arrangement may be adapted by rearranging the inlets and outlets at the heat exchanger.

In the illustrated embodiment, the first inlet 38 is fluidly connected with the antifreeze circuit 112 by a first inlet tube 42. More specifically, an end 42a of first inlet tube 42 is connected to the pipelines of the antifreeze circuit 112 by a connector, e.g. a quick fit connector or a treaded connector typically used in plumbing.

The first outlet 32 of the heat exchanger 30 is fluidly connected to the internal 35 volume of the reservoir 20 by a reservoir tube 44. The reservoir tube 44 extends through a sidewall of the reservoir 20 and comprises an open end that feeds the antifreeze fluid into the reservoir 20. A first return tube 40, having an open end disposed inside the reservoir, extends through a sidewall of the reservoir 20. More specifically, the first return tube 40 and the reservoir tube 44 are arranged on opposing sidewalls of the reservoir. The first return tube 40 connects to the antifreeze circuit 112 by a connector at an end 40a opposite to the open end, thereby providing fluid passage for the cooled antifreeze fluid to return to the heat pump 110. As shown in Figure 3, the first return tube 40 and the reservoir tube 44 are provided towards a lower end of the reservoir 20.

In this embodiment, the reservoir 20 is primarily used for holding an amount of antifreeze fluid that is additionally required by the heat pump 110 when it carries out a defrost cycle. Furthermore, the volume of antifreeze fluid contained in the reservoir 20 reduces the risk of heat pump short cycling, as well as enabling the provision of a high flow rate in the antifreeze circuit 112, thus enhancing its heat transfer efficiency and capacity.

The reservoir 20 comprises a baffle 22 extending vertically from the base and in between the reservoir tube 44 and first return tube 40. The baffle 22 is configured zo to disrupt the flow of antifreeze fluid and improves its mixing and circulation within the reservoir 20. More specifically, as the antifreeze fluid enters the reservoir 20 through the reservoir tube 44, it routes around the baffle and interacts with pipework that are disposed in the reservoir 20, before being discharged through the first return tube 40. The baffle 22 advantageously reduces stagnant regions in the reservoir 20.

The second inlet 36 and the second outlet 34 of the heat exchanger 30 are fluidly connected with the indoor circuit 152 by respective second inlet tube 50 and second outlet tube 52. More specifically, the ends 50a,52a of second inlet tube 42 and second outlet tube 52 are connected to the pipelines of the indoor circuit 152 by connectors.

As shown in Figure 1, the first inlet tube 42, the second inlet tube 50 and the second outlet tube 52 extend through the reservoir 20. During use, the said tubes are immersed in the antifreeze fluid in the reservoir 20. In some cases, such an arrangement may advantageously offer additional heat transfer area between the antifreeze fluid and the water flow. For example, the antifreeze fluid in reservoir 20 may preheat the return water flow (from the indoor circuit 152) in second inlet tube 50 prior to its entrance to the heat exchanger 30, and may continue heating the forward water flow (towards the indoor circuit 152) once it has exited the heat exchanger 30.

As shown in Figure 1, The heat exchanger 30 is supported on the sidewalls of the reservoir 20 by the tubes 32,34,36,38. That is, the heat exchanger is suspended at the side of the reservoir 20. Since the heat exchanger 30 can be installed by plumbing, negating the need for separately fixing it in place. Furthermore, such an arrangement eliminates the need for additional pipe works (e.g. elbows and other constrictions) that would otherwise increase the pressure loss in the fluid flow.

The cylindrical heat exchanging unit 10 is sized to be fitted beneath the hot water cylinder 102, as shown in the schematic diagram of Figure 1. In the specific example, the heat exchanging unit 10 has cross-sectional diameter of 0.52m, corresponding to that of a typical insulated hot water cylinder. However, in other examples, the heat exchanging unit 10 may adopt a range of cross-sectional diameters depending on the size of the intended hot water cylinder it fits under.

Furthermore, in order to fit underneath a hot water cylinder, the height of the heat exchanging unit 10 is limited to 0.25m, corresponding to the typical elevation of a domestic hot water cylinder. Thus, the heat exchanging unit 10 may fit into an unused space commonly found in a domestic heat system, thereby removing the need to seek suitable installation space in an airing cupboard and other confined spaces.

The heat exchanging unit 10 facilitates an efficient heat pump installation. For example, a heating engineer may fix the base 12 of heat exchanging unit 10 to the desired location (e.g. beneath a hot water cylinder) to simultaneously install the buffer tank and heat exchanger in place. The heating engineer may then connect the antifreeze circuit 112 and the indoor circuit 152 to the corresponding connectors at the heat exchanging unit 10. Because the heat exchanger 30 and the reservoir 20 is already fluidly connected, there is less pipework to be installed.

Second embodiment Figure 4 is a schematic diagram of a heating system 200 according to a second embodiment of the present invention. Figures 5 and 6 are respectively a plan view and a side view of a heat exchanging unit 310 installed in the heating system 200. In order to display its internal components, the heat exchanging unit 310 is shown without coverings but they are nevertheless present.

The heating system 200 and the heat exchanging unit 310 of the second embodiment are structurally and functionally similar to their counterparts of the first embodiment shown in Figures 1 to 3. In the second embodiment, the heat pump 210 does not require the use of a buffer tank. Thus, reservoir 320 of the heat exchanging unit 310 is configured to serve as a buffer tank or volumiser for the water flow circulating an indoor circuit 252. That is, by rearranging the flow connections, the same heat-exchanging unit can advantageously adapt to heat pump systems with different requirements.

For conciseness, like features are not described again.

Referring to Figure 3, the heating system 200 comprises a heat pump 210 and a central heating system 250 respectively connected to an antifreeze circuit 212 and an indoor circuit 252. In use, the heat pump 210 serves as a primary heat source for the central heating system 250, through heat exchange between the two fluid circuits 212, 252 at the heat exchanging unit 310.

The heat pump 210 is an outdoor air-source heat pump. The heat pump 210 is fluidly connected to the heat exchanging unit 310 by the antifreeze circuit 212 having an antifreeze circulating therein. The heat pump 210 comprises a pump for driving antifreeze flow in the antifreeze circuit 212 and a pressure vessel for absorbing thermal expansion in the antifreeze fluid. That is, in this embodiment, the antifreeze circuit 212 is not provided with a pump nor a pressure vessel.

Furthermore, the heat pump 210 is capable of providing modulating flow rate control, so that the flow rate of antifreeze in the antifreeze circuit 212 can be precisely controlled. The flow rate of antifreeze is controlled based on several factors, for example, the amount of heating required and the operating mode/condition of the heat pump 210. In addition, the heat pump 210 is engineered in a way that it does not require a minimum amount of antifreeze flow to perform a defrost cycle. Thus, such heat pumps typically do not require the provision of a buffer tank in the antifreeze circuit 212.

Similar to the first embodiment, the antifreeze circuit 212 comprises a forward flow section 212a responsible for transferring heated antifreeze fluid from the heat pump 210 to the heat exchanging unit 310 and a conventional coil heat exchanger (not shown) disposed in a hot water cylinder 202. Once it has dissipated its heat energy at the heat exchange unit 310 or the coil heat exchanger, the cooled antifreeze fluid is returned, by a return flow section 212b, to the heat pump 210 to be reheated.

The central heating system 250, on the other hand, is connected to the heat exchanging unit 310 by the indoor circuit 252. The fluid circulating the indoor circuit 252 mainly consists of water, and optionally comprises additives such as rust and scale inhibitors.

The indoor circuit 252 comprises a forward flow section 252a responsible for transferring heated water from the heat exchanging unit 310 to various radiators and/or underfloor heating systems in the central heating system 250. Once it has dissipated its heat energy at the central heating system 250, the cooled water is returned, through a return water flow section 252b, to the heat exchanging unit 310 to be reheated.

The main difference between the heat exchanging unit 310 of the second embodiment and the heat exchanging unit 10 of the first embodiment lies in their different connections with the antifreeze and indoor circuits.

Referring to Figures 5 and 6, the heat exchanging unit 310 is structurally the same as the heat exchanging unit 10 as shown in Figures 2 and 3, except it comprises an auxiliary immersion heater 326 sealingly installed through an orifice 324 opened on the sidewall of the reservoir 320.

The heat exchanger 330 in this embodiment comprises an inlet/outlet arrangement different to that in the heat exchanger 30 of the first embodiment.

The heat exchanger 30 comprises a first inlet 332 and a second inlet 334 fluidly connected to respectively a first outlet 336 and a second outlet 338 through the flow channels in the heat exchanger 330. The inlets 332,334 and outlets 336,338 are provided on the opposite sides of the heat exchanger 330, thus the heat exchanger 330 is a concurrent current heat exchanger. In other embodiments, a counter-current flow arrangement may be adapted by rearranging the inlets and outlets at the heat exchanger.

In the illustrated embodiment, the first inlet 332 of the heat exchanger 330 is fluidly connected to the internal volume of the reservoir 320 by a reservoir tube 344. The reservoir tube 344 extends through a sidewall of the reservoir 320 and comprises an end opened to the internal volume of the reservoir 320. A first return tube 340, having an open end disposed inside the reservoir, extends through a sidewall of the reservoir 320. More specifically, the first return tube 340 and the reservoir tube 344 are arranged on opposing sidewalls of the reservoir 320. The first return tube 340 connects to the indoor circuit 352, thereby providing fluid passage for the cooled water flow to return to the heat exchanging unit 310. As shown in Figure 6, the first return tube 340 and the reservoir tube 344 are provided towards a lower end of the reservoir 320.

The first outlet 338 of the heat exchanger 330 is fluidly connected with the indoor circuit 352 by a first outlet tube 342, which serve to provide fluid passage for heated water flow to the central heating system 350.

In this embodiment, the reservoir 320 serves as buffer tank or a volumizer for the indoor circuit 352. For example, the volume of water contained in the reservoir 320 helps mitigate the fluctuations commonly experienced in the central heating system 350, e.g. due to on/off flow control to different heating zones. An automatic air vent 328 is provided towards an upper end of the reservoir 320 for venting gas (e.g. air) accumulated in the reservoir 320.

The second inlet 334 and the second outlet 336 of the heat exchanger 330 are fluidly connected with the antifreeze circuit 312 by respective second inlet tube 352 and second outlet tube 350.

As shown in Figure 5, the first outlet tube 342, the second inlet tube 352 and the second outlet tube 340 extend through the reservoir 320. During use, the said tubes are immersed in the water stored in the reservoir 320.

In the event of a heat pump failure or occurrence of an abnormality in the antifreeze circuit, e.g. the antifreeze fluid is insufficient to provide adequate heating, a controller (not shown) may activate the auxiliary immersion heater 326 to heat the water stored in the reservoir 320. Not only does the immersion heater 326 ensures continuous supply of heat energy to the central heating system 350 by heat transfer through the immersed second inlet and outlet tubes 340,352, but the heated water in the reservoir 320 may also raise the temperature of the antifreeze fluid circulating the antifreeze circuit 312, thereby enabling a defrosting cycle to be carried out at the heat pump even when it is incapable of extracting heat from the envioronment.

The auxiliary immersion heater 326 is a typical immersion heater that is found in a domestic central heating system. For example, the auxiliary immersion heater 326 may have a rated output ranging from 3 to 6 kW.

The controller activates the heat exchanger upon: 1) receiving a signal indicating an abnormality in the antifreeze circuit, e.g. from a flow/temperature sensor in the antifreeze circuit; or 2) receiving a signal from the heat pump indicating heat pump failure; or 3) receiving a signal from a controller of the central heating system calling for increased heating; 4) user input at a physical user interface, e.g. a button or a switch at the heat exchanging unit; or 5) receiving user input from a remote device, e.g. a text message sent from, or an app provided on, the remote device.

Claims

Claims 1. A heat exchanging unit for exchanging heat between a first fluid circuit and a second fluid circuit of a heating system, the heat exchanging unit comprising: a base; a reservoir provided on the base, the reservoir is arranged to be filled with a first fluid circulating the first fluid circuit; a heat exchanger supported on the base, the heat exchanger is arranged to lo exchange heat between the first fluid circulating the first fluid circuit and a second fluid circulating the second fluid circuit; and a plurality of first tubes arranged to provide fluid communication between the first fluid circuit and both the heat exchanger and the reservoir, and a plurality of second tubes arranged to provide fluid communication between the second fluid circuit and the heat exchanger.
2. The heat exchanging unit of claim 1, wherein the plurality of first and second tubes extend through a sidewall of the reservoir.
3. The heat exchanging unit of claim 2, wherein the heat exchanger is supported on the reservoir by the plurality of first and second tubes.
4. The heat exchanging unit of claim 2 or claim 3, wherein during use the plurality of first and second tubes are at least partially immersed in the first fluid in the reservoir.
5. The heat exchanging unit of claims 2 to 4, wherein the plurality of the second tubes and at least one of the first tubes extend through the reservoir.
6. The heat exchanging unit of claims 2 to 5, wherein one of the first tubes comprises an opening inside the reservoir to provide fluid communication between the first fluid circuit and the reservoir.
7. The heat exchanging unit of claims 6, wherein the said first tube comprises two open-ended segments extending through opposing sidewalls of the reservoir.
8. The heat exchanging unit of claim 1, wherein some or all of the plurality of first tubes are routed away from the reservoir.
9. The heat exchanging unit of claim 8, wherein the heat exchanger is mounted onto the base.
10. The heat exchanging unit of any of the preceding claims, wherein the reservoir further comprises an auxiliary heating element configured to heat the first fluid inside the reservoir.
11. The heat exchanging unit of claim 10, further comprises a controller for controlling the auxiliary heating element, wherein upon receiving a signal indicating a abnormality in the first fluid circuit, the controller controls the auxiliary heating element to heat the first fluid inside the reservoir.
12. The heat exchanging unit of any of the preceding claims, wherein the first fluid is arranged to have a different freezing point to that of the second fluid.
13. The heat exchanging unit of any of the preceding claims, wherein one of the first fluid or the second fluid is arranged to comprise an antifreeze.
14. The heat exchanging unit of any of the preceding claims, wherein the reservoir having an internal volume of less than 0.03m3, or less than 0.02m3, or less than 0.00m3.
15. The heat exchanging unit of any of the preceding claims, wherein the heat exchanging unit is configured to be installed, by the base, at a location beneath a hot water cylinder of a central heating system.
16. The heat exchanging unit of any preceding claims, wherein the base having substantially the same cross-section profile as the hot water cylinder.
17. The heat exchanging unit of any one of the preceding claims, wherein the heat exchanger comprises a plate heat exchanger.
18. The heat exchanging unit of any one of the preceding claims, wherein reservoir further comprises at least one baffle for improving circulation of the first fluid in the reservoir.
19. A heat exchanging unit for exchanging heat between a first fluid circuit and a second fluid circuit of a heating system, the heat exchanging unit comprising: a reservoir arranged to be filled with a first fluid circulating the first fluid circuit; a heat exchanger arranged to exchange heat between a first fluid circulating the first fluid circuit and a second fluid circulating the second fluid circuit; and a plurality of first tubes arranged to provide fluid communication between the first fluid circuit and both the heat exchanger and the reservoir, and a plurality of second tubes arranged to provide fluid communication between the second fluid circuit and the heat exchanger; wherein the plurality of the second tubes and at least one of the first tubes extend through the reservoir.
20. The heat exchanging unit of claim 19, wherein during use the plurality of first and second tubes are at least partially immersed in the first fluid in the reservoir.
21. The heat exchanging unit of claim 19 or claim 20, wherein one of the first tubes comprises two open-ended segments extending through opposing sidewalls of the reservoir so as to provide fluid communication between the reservoir and the first fluid circuit.
22. The heat exchanging unit of claims 19 to 21, further comprises a base on which the reservoir and the heat exchanger are supported.
23. A heating system, comprising: a first fluid circuit and a second fluid circuit; and the heat exchanging unit of claims 1 to 22 for exchanging heat between the first and second fluid circuits.
24. The heating system of claim 23, wherein one of the first and second fluid circuits is connected with a heat pump and other one of the first and second fluid circuits forms part of a central heating system.
25. A method of installing the heat exchanging unit of claims 1 to 18 and claim 22 to form a heating system, comprising the step of: installing the heat exchanging unit, by the base, at a location beneath a hot water cylinder; and connecting the plurality of first and second tubes to the respective first and second fluid circuits.Claims 1. A heat exchanging unit for exchanging heat between a first fluid circuit and a second fluid circuit of a heating system, the heat exchanging unit comprising: a base; a reservoir provided on the base, the reservoir is arranged to be filled with a first fluid circulating the first fluid circuit; a heat exchanger supported on the base, the heat exchanger is arranged to exchange heat between the first fluid circulating the first fluid circuit and a second fluid circulating the second fluid circuit; and a plurality of first tubes arranged to provide fluid communication between the first fluid circuit and both the heat exchanger and the reservoir, and a plurality of second tubes arranged to provide fluid communication between the second fluid circuit and the heat exchanger, wherein the plurality of first and second tubes C1/41 extend through a sidewall of the reservoir, and wherein the heat exchanger is C\I supported on the reservoir by the plurality of first and second tubes. a)2. The heat exchanging unit of claim 1, wherein during use the plurality of first CO20 and second tubes are at least partially immersed in the first fluid in the reservoir.3. The heat exchanging unit of either of claims 1 and 2, wherein the plurality of the second tubes and at least one of the first tubes extend through the reservoir.4. The heat exchanging unit of any one of claims 1 to 3, wherein one of the first tubes comprises an opening inside the reservoir to provide fluid communication between the first fluid circuit and the reservoir.5. The heat exchanging unit of claims 4, wherein the said first tube comprises two open-ended segments extending through opposing sidewalls of the reservoir.6. The heat exchanging unit of claim 1, wherein some of the plurality of first tubes are routed away from the reservoir.7. The heat exchanging unit of any of the preceding claims, wherein the reservoir further comprises an auxiliary heating element configured to heat the first fluid inside the reservoir.8. The heat exchanging unit of claim 7, further comprises a controller for controlling the auxiliary heating element, wherein upon receiving a signal indicating a abnormality in the first fluid circuit, the controller controls the auxiliary heating element to heat the first fluid inside the reservoir.9. The heat exchanging unit of any of the preceding claims, wherein the first fluid is arranged to have a different freezing point to that of the second fluid.10. The heat exchanging unit of any of the preceding claims, wherein one of the first fluid or the second fluid is arranged to comprise an antifreeze. C\IC\I 11. The heat exchanging unit of any of the preceding claims, wherein the a) reservoir having an internal volume of less than 0.003m3.O12. The heat exchanging unit of any of the preceding claims, wherein the heat C\I exchanging unit is configured to be installed, by the base, at a location beneath a hot water cylinder of a central heating system.13. The heat exchanging unit of any preceding claims, wherein the base having substantially the same cross-section profile as the hot water cylinder.14. The heat exchanging unit of any one of the preceding claims, wherein the heat exchanger comprises a plate heat exchanger.15. The heat exchanging unit of any one of the preceding claims, wherein reservoir further comprises at least one baffle for improving circulation of the first fluid in the reservoir.16. A heating system, comprising: a first fluid circuit and a second fluid circuit; and the heat exchanging unit of claims 1 to 15 for exchanging heat between the first and second fluid circuits.17. The heating system of claim 16, wherein one of the first and second fluid circuits is connected with a heat pump and other one of the first and second fluid circuits forms part of a central heating system.18. A method of installing the heat exchanging unit of claims 1 to 15 to form a heating system, comprising the step of: installing the heat exchanging unit, by the base, at a location beneath a hot water cylinder; and connecting the plurality of first and second tubes to the respective first and second fluid circuits. c\I ('Si a) O co 20C