Indoor exhaust air heat pump system, and method of controlling an indoor exhaust air heat pump
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- JOULE GRP LTD
- Filing Date
- 2026-01-30
- Publication Date
- 2026-08-06
Smart Images
Figure EP2026052477_06082026_PF_FP_ABST
Abstract
Description
[0001] Title: Indoor exhaust air heat pump system, and method of controlling an indoor exhaust air heat pump
[0002] Description:
[0003] The present invention relates to an indoor exhaust air heat pump system, as well as to a method of controlling an indoor exhaust air heat pump.
[0004] Various types of domestic heat pumps exist, and they can be broadly categorized based on their installation location (especially indoor versus outdoor) and type of heat source, such as air (including ambient air and exhaust air of a ventilation system), ground (geothermal heat) and water.
[0005] Exhaust air of an indoor ventilation system, hereafter also referred to as “exhaust air", may form a very interesting heat source for a heat pump, because such exhaust air has a relatively high energy density, and would otherwise by expelled from the building as waste. In most countries, legislation requires ventilation of buildings, such as residential buildings and office spaces. Using an exhaust air heat pump allows at least a part of the thermal energy to be recovered, before it is allowed to leave the building. In this way, energy is recovered that would otherwise be wasted via the obligatory ventilation system.
[0006] Advantages of exhaust air heat pumps are the relatively high energy density, allowing the heat pump to be relatively compact. Moreover, indoor air temperature is generally more stable compared to outdoor air temperatures, meaning the heat pump can operate more consistently, regardless of outdoor weather conditions. By recovering heat from exhaust air, these systems help reduce overall energy consumption and carbon emissions, contributing to a greener building solution and resulting in environmental benefits.
[0007] Disadvantages of exhaust air heat pumps are a potentially limited heat supply, as well as challenges with respect to noise attenuation.
[0008] Limited heat supply may especially occur in smaller homes or buildings with low ventilation rates resulting in a limited source for heat supply. For this reason, they are often installed in a hybrid set up, wherein they are combined with a conventional central heating boiler. Such a hybrid set up allows an exhaust air heatpump to be used also in buildings with low ventilation rates and / or large heating demands.
[0009] A further important factor is noise attenuation. After all, if exhaust air heat pumps are installed indoor, where they are connected to the indoor ventilation system, noise produced during operation is a serious concern that directly relates to user comfort and willingness of households to install such an exhaust air heat pump. In practice, installation will often be at an attic, thus potentially also near bed rooms. Also in smaller homes, such as apartments, a bed room may be close to a space where the heat pump and central heating boiler are installed. As a result, noise attenuation becomes a critical point of concern. The operational sounds generated by compressors, fans, and moving parts can significantly affect indoor comfort levels. Moreover, available space indoor may be limited. The balance between effective heat transfer, noise management, and compact design is thus a key consideration in the development of exhaust air heat pumps, that are installed indoor.
[0010] European patent application EP 3296658 A1 is considered the closest prior art, and discloses an exhaust air heat pump apparatus and method of processing exhaust air. It describes an outdoor system, wherein the exhaust air heat pump is positioned outside a many apartment building, e.g. on a roof of a building. The exhaust air heat pump is configured to use a combination of exhaust air, obtained from the many apartments in the many apartment building, and outdoor air. EP 3 296 658 A1 also explicitly acknowledges that in many-apartment houses with a common exhaust air heat pump (EAHP), adjusting the air flow rates in replacement and / or exhaust air channels in a single apartment affects the balance of the system and also the ventilation of other apartments in the building. This can lead to situations where the EAHP is far from its optimal point of operation and / or some apartments are facing problems relating to indoor air quality, temperature or ventilation. The EAHP of EP 3 296 658 A1 is configured to optimize the heat pump's performance, and more in particular its coefficient of performance (COP), under the varying conditions. More in particular, the outdoor system is designed to adjust the air flows to achieve the most favourable operating conditions for the heat pump, and does so by e.g. setting a fan speed of an exhaust fan to control the amount of exhaust air entering a mixing chamber of the exhaust air heat pump.The European patents EP 2853829 B1 , EP 3607249 B1 and EP 2450 641 B1, European patent application EP 3 165 838 A1, and United States patent US 10,408,487 B1 are acknowledged as further prior art.
[0011] An objective of the present invention is to provide an indoor exhaust air heat pump, that is improved relative to the prior art, and wherein at least one of the above stated problems is obviated or alleviated.
[0012] Said objective is achieved with the indoor exhaust air heat pump system according to claim 1 of the present invention, comprising:
[0013] - an indoor exhaust air heat pump, having a housing that comprises a primary heat exchanger and a secondary heat exchanger, a compressor, and a fan;
[0014] - a first air inlet configured to be connected to an indoor ventilation system of a building, wherein exhaust air of said indoor ventilation system defines a first heat source for the primary heat exchanger;
[0015] - a second air inlet configured to be in fluid connection with outside air that defines a second heat source for the primary heat exchanger;
[0016] - a flow sensor configured to measure an air flow rate to determine a preselected flow rate of the exhaust air of the indoor ventilation system;
[0017] - a first air flow regulator that is in fluid connection with the first air inlet, and that is configured to control a flow rate of exhaust air passing therethrough;
[0018] - a second air flow regulator that is in fluid connection with the second air inlet, and that is configured to control a flow rate of outside air passing therethrough;
[0019] - a mixing chamber that is arranged downstream of the first and the second air flow regulator, and upstream of the primary and the secondary heat exchanger;
[0020] - wherein the first and the second air flow regulator are adjustable between an opened state and a closed state, and at least one intermediate state therebetween; and
[0021] - wherein the system further comprises a controller that is communicatively connected to the flow sensor, wherein the controller is configured to independently adjust the first air flow regulator and the second air flow regulator based on the air flow rate of the exhaust air measured by the flow sensor, to thereby maintain the measured air flow rate of the exhaust air within a predetermined bandwidth of a pre-selected flow rate of the exhaust air of the indoor ventilation system.The primary heat exchanger is associated with a primary heating circuit, and the secondary heat exchanger is associated with a secondary heating circuit. The primary heat exchanger brings thermal energy from the primary heating circuit into the heat pump and heats a refrigerant. The secondary heat exchanger of the heat pump transfer the heat stored in the refrigerant into a medium circulating in a secondary heating circuit.
[0022] According to the invention, the indoor exhaust air heat pump system is designed as a dual source heat pump system that is able to use exhaust air of an indoor ventilation system as a first heat source, and outside air as a second heat source. As the indoor exhaust air heat pump system may extract heat from two sustainable energy sources, it will be able to meet a larger heating demand. In this way, the exhaust air heat pump may not need to be combined anymore in a hybrid set up with a conventional central heating boiler, or it could at least greatly limit the use of such a conventional central heating boiler if it would be applied in a hybrid set up.
[0023] The present invention is based on the insight that for an indoor heat pump system, the primary control objective should be the stability of the building's ventilation to ensure occupant comfort, rather than solely the optimization of the heat pump's own performance. In contrast to prior art systems like EP 3296658 A1 , which adjust air flows to maximize the Coefficient of Performance (COP), the present invention prioritizes ventilation integrity. To this end, the controller of the present invention is configured to execute a unique control method. It uses the real-time measurement from the flow sensor, which measures the exhaust air flow rate from the indoor ventilation system, as the primary control input. Based on this measurement, the controller independently adjusts the first air flow regulator (for exhaust air) and the second air flow regulator (for outside air). The specific goal of this control loop is to actively maintain the measured exhaust air flow rate within a narrow, predetermined bandwidth of a pre-selected target flow rate. This control philosophy ensures that the building's ventilation is never compromised. This provides several advantages.
[0024] First, it decouples the building's ventilation rate from the heat pump's operational state. This means that even when the heat pump's heating demand changes, the total volume of air extracted from the building's ventilation system remains constant. This directly solves the problem of ventilation instability identified in the prior art.Second, the system is highly robust and adaptable. Because it relies on a real-time flow measurement, it can automatically compensate for long-term changes in the ventilation system (such as gradual filter clogging) or short-term changes.
[0025] Third, the use of air flow regulators that are adjustable between an open and a fully closed state provides a wider and more precise control range. This is a significant improvement over the system of EP 3296658 A1 , which relies on adjusting the speed of an exhaust fan to control the flow of exhaust air. A fan, by its nature, cannot be fully closed to block an air path. The regulators of the present invention, however, allow for a complete shut-off of one air source if needed, giving the controller maximum flexibility in managing the heat sources.
[0026] Regarding energy performance, it is desirable to maintain the air in the mixing chamber, that defines the heat source for the heat exchanger, as high as possible.
[0027] In most operating conditions, e.g. during fall, winter and spring, the exhaust air of the indoor ventilation system will normally be hotter than the outside air. In such conditions, the exhaust air of the indoor ventilation system has the highest energy density, and will preferably be used as the primary, and possibly only, heat source for the indoor exhaust air heat pump.
[0028] However, if the exhaust air of the indoor ventilation system alone is insufficient to meet the heating demand, the indoor exhaust air heat pump according to the invention is able to gradually increase the amount of outside air that is used as a secondary heat source. More in particular, the second air flow regulator may be set in a plurality of positions between an initially closed state towards a fully opened state thereof, thereby gradually increasing the amount of outside air that is mixed with the more energy dense exhaust air. In this way, the second air flow regulator may gradually increase the amount of outside air that is allowed to enter into the mixing chamber, where it mixes with the exhaust air, before the mixed air streams pass the heat exchanger downstream of the mixing chamber. Current heat pumps are able to extract thermal energy from outside air well below freezing point, up till temperatures as low as -15 °C.
[0029] In some operating conditions, especially in summer time, the outside air may have a higher temperature than the exhaust air. In such hot circumstances, the heating demand will very likely also be limited to heating tap water only, and the indoorexhaust air heat pump will preferably run solely, or at least mostly, on the outside air that defines the second heat source. Because also the first air flow regulator may be set in a plurality of positions between an initially closed state towards a fully opened state thereof, optimized energy performance may also be obtained in these circumstances. In all operating conditions, thus also in the summer time, ventilation of the (residential) building is maintained. As such, the exhaust air is always available as a source, but it is conceivable that the indoor exhaust air heat pump system gives preference to the hotter outside air for the current heating demand, such a heating tap water.
[0030] Regarding acoustic performance, the control method according to the invention also leads to significant improvements.. More in particular, the control method allows for an optimal mixture of exhaust air of the indoor ventilation system and outside air to be obtained. This allows the heat pump to run on the highest available energy density. In this way, the total flow rate required can be reduced, and consequently a fan of the indoor exhaust air heat pump may run at a lower speed. This results in less noise being generated by said fan. Moreover, the reduced flow rates also allows for a compact design, which is especially advantageous for an indoor heat pump.
[0031] On top of optimizing energy and acoustic performance, also increased levels of comfort may be obtained. After all, the adjustable air flow regulators allow the power output of the heat pump to controlled while maintaining a preferred ventilation flow rate by virtue of the flow sensor. In this way, a key advantage of the invention is that the ventilation flow rate is no longer influenced by a flow rate demand of the exhaust air heat pump. Consequently, the ventilation flow rate is set in accordance with comfort demand, rather than being determined by a desired heating demand.
[0032] Contrary to most prior art indoor exhaust air heat pump systems that rely on look-up tables that are determined at initialisation of the system, the indoor exhaust air heat pump system according to the invention proposes to apply a flow sensor that is configured to measure the air flow rate to determine a pre-selected flow rate of the exhaust air of the indoor ventilation system. In this way, the controller of the indoor exhaust air heat pump system according to the invention can take the actual settings into account when setting the flow rates of exhaust air and outside air entering the mixing chamber independently of each other.An indoor exhaust heat pump system that relies on a look-up table that is determined at initialisation will have fixed settings that are optimized for a freshly installed system. However, the air flow resistance in indoor ventilation systems will change over time, either by a gradual clogging up and successive cleaning, with also the risk that a user cleans an entry point and fails to return it at the correct resistance setting. As a result, the lookup table will most of the time only reflect a sub-optimal setting. Moreover, the invention proposes the use of the first air flow regulator and the second air flow regulator that are both adjustable between an opened state and a closed state, and at least one intermediate state therebetween. This requires look-up tables to be determined at initialisation for the opened state, the closed state, and each intermediate state, and for each zone independently, which is a very laborious task. For example, for a first zone, a look-up table is determined over the full operating range of the air flow rate of the ventilation heat pump, i.e. from the minimum flow rate to the maximum flow rate thereof. If the operating range has a minimum flow rate of 60 m3 / h and a maximum flow rate of 200 m3 / h, the underpressure (expressed in Pa) may be determined for 60, 80, 120, 140, 160, 180 and 200 m3 / h. For each additional zone, all underpressure will have to determined again, to define the correlation of the underpressure at the specific flow rates for each zone.
[0033] According to the invention, the controller of the indoor exhaust air heat pump system can take the actual settings into account when setting the flow rates of exhaust air and outside air entering the mixing chamber independently of each other. In practice, this means that initialisation of the indoor exhaust air heat pump system according to the invention is greatly simplified relative to look-up tables. After all, it suffices to run the indoor exhaust air heat pump system at its maximum flow rate and set the resistance of each inlet valve for each zone only once. In this way, the laborious task of filling look-up tables for a large plurality of settings is reduced to a simple and fast initialisation procedure. The flow sensor thus guarantees that the operation of indoor exhaust air heat pump system may be adjusted to varying use conditions, such as long term changes (e.g. due to the indoor exhaust air heat pump system gradually clogging up) and short term changes (including use states to meet an actual ventilation demand, but also weather conditions, such as wind speed, as well as freezing of the evaporator). For example, if an exhaust air flow rate setting is temporarily changed, for example if the exhaust air flow rate is temporarily increased in a bathroom whensomebody takes a shower or decreased afterwards, the controller of the indoor exhaust air heat pump system will immediately recognize this change that is measured by the flow sensor.
[0034] Being able to adapt to short term changes due to freezing of the evaporator is especially interesting, because it allows to increase the performance of the indoor exhaust air heat pump system. After all, the flow sensor allows the indoor exhaust air heat pump system to detect frost formation on the evaporator building up. The controller can then adjust the setting of the air flow regulators to a desired state, such as the opened state, the closed state or one of the intermediate states therebetween, to thereby maintain exhaust air flow rates at a desired and comfortable level. This allows the indoor exhaust air heat pump system to apply deep cooling with evaporator frost, and thereby increase the performance of the indoor exhaust air heat pump system, while still maintaining the desired exhaust air flow rates.
[0035] Summarizing, the indoor exhaust air heat pump according to the invention is a dual source indoor exhaust air heat pump, thereby increasing the heating capacity of the heat pump on the basis of sustainable energy sources. This reduces the need for it to be supplemented with other heating technologies, such as in a hybrid setup with a conventional central heating boiler that runs on non-renewable fossil fuels, in particular natural gas. However, even in a hybrid setup, the indoor exhaust air heat pump may greatly reduce the need to run the conventional central heating boiler on fossil fuels. Applying a flow sensor and air flow regulators having multiple states provides a flexible system that is able to obtain a high level of performance in terms of energy and acoustics, while also guaranteeing optimal comfort, because influences on the air flow rate of the indoor ventilation system are actively minimized, and preferably eliminated.
[0036] Said objective is furthermore achieved with the method of controlling an indoor exhaust air heat pump system, according to claim 19 of the present invention, comprising the steps of:
[0037] - supplying exhaust air of an indoor ventilation system that defines a first heat source for a primary heat exchanger of an indoor exhaust air heat pump system;
[0038] - supplying outside air that defines a second heat source for the primary heat exchanger;- with a flow sensor, measuring an air flow rate of exhaust air of the indoor ventilation system to determine a pre-selected flow rate of the exhaust air of the indoor ventilation system;
[0039] - based on the measured air flow rate, independently regulating a flow rate of exhaust air originating from an indoor ventilation system, that defines the first heat source, and a flow rate of outside air, that defines the second heat source, to thereby maintain the measured air flow rate of the exhaust air of the indoor ventilation system within a predetermined bandwidth of a pre-selected flow rate;
[0040] - providing a mixture by mixing the exhaust air and the outside air; and
[0041] - heating a heat exchanger of the heat pump with the mixture.
[0042] According to a preferred embodiment of the method, the predetermined bandwidth is 15%, and preferably 10%, of the pre-selected flow rate.
[0043] According to a further preferred embodiment, the indoor exhaust air heat pump system further comprises:
[0044] - one or more than one further air inlet configured to be connected to an indoor ventilation system of a building, wherein exhaust air of said indoor ventilation system defines a further heat source for the primary heat exchanger;
[0045] - wherein each further air inlet comprises a further air flow regulator that is in fluid connection with the respective further air inlet, wherein said further air flow regulator is configured to control a flow rate of exhaust air passing therethrough; and - wherein each further air inlet corresponds to a further flow sensor configured to measure an air flow rate to determine a pre-selected flow rate of the exhaust air of the indoor ventilation system.
[0046] By measuring the air flow rate for each air inlet independently, it is on the one hand possible to determine a total pre-selected flow rate of the exhaust air of the indoor ventilation system, and on the other hand determine a pre-selected flow rate for each ventilation zone corresponding to a dedicated further air inlet. This allows the indoor exhaust air heat pump system to maintain the flow rates, and thus the level of ventilation, constant, while also guaranteeing optimal performance.
[0047] Preferred embodiments are the subject of the dependent claims.
[0048] The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, and in particular the aspects and features described in the attached dependent claims,may be an invention in its own right that is related to a different problem relative to the prior art.
[0049] In the following description preferred embodiments of the present invention are further elucidated with reference to the drawing, in which:
[0050] Figure 1 is a schematic view of a building comprising an indoor exhaust air heat pump system according to the invention;
[0051] Figure 2 is a schematic view of an indoor exhaust air heat pump system according to a first preferred embodiment;
[0052] Figure 3 is a schematic view of an indoor exhaust air heat pump system according to a second preferred embodiment;
[0053] Figure 4 shows different states of louvres of an air flow regulator;
[0054] Figure 5 is a schematic view of a first air flow regulator configured to regulate a flow rate of exhaust air;
[0055] Figure 6 is a perspective view of the first air flow regulator of Fig. 5; and Figure 7 is a schematic view of an indoor exhaust air heat pump system according to a third preferred embodiment.
[0056] A building 1 with an indoor exhaust air heat pump system 2 according to the invention is shown in Fig. 1. Such indoor exhaust air heat pump system 2, is particularly suitable for residential buildings. To prevent unnecessary repetition, the "indoor exhaust air heat pump system 2” is hereafter also referred to as “heat pump system 2”.
[0057] The indoor exhaust air heat pump system 2 is arranged inside the building 1 , for example at an attic 3. Heat pump system 2 comprises an indoor exhaust air heat pump 4, a first air inlet 5, a second air inlet 6, a first air flow regulator 7, a second air flow regulator 8, and a mixing chamber 9. The indoor exhaust air heat pump 4 has a housing 10 that comprises a primary heat exchanger 11, a secondary heat exchanger 12, a compressor 13, and a fan 14. The first air inlet 5 is configured to be connected to an indoor ventilation system 15 of the building 1. Exhaust air E of said indoor ventilation system 15 defines a first heat source Hi for the primary heat exchanger 11. The second air inlet 6 is configured to be in fluid connection with outside air O that defines a second heat source H2 for the primary heat exchanger 11. In this application, outside air O is defined as ambient air outside the building 1 wherein theindoor heat pump 4 is installed during use. The first air flow regulator 7 is in fluid connection with the first air inlet 5, and is configured to control a flow rate of exhaust air E passing therethrough. Likewise, the second air flow regulator 8 that is in fluid connection with the second air inlet 6, and is configured to control a flow rate of outside air O passing therethrough. The mixing chamber 9 is arranged downstream of the first air flow regulator 7 and the second air flow regulator 8, and upstream of the primary heat exchanger 11. According to the invention, the first air flow regulator 7 and the second air flow regulator 8 are adjustable between an opened state (schematically shown in Fig. 4A) and a closed state (schematically shown in Fig. 4D), and at least one intermediate state (e.g. shown schematically in Figs. 4B and 4C) therebetween. This adjustability of the air flow regulators 7, 8 allows a controller 16 to set the flow rates of exhaust air E and outside air O entering the mixing chamber 9 independently of each other. Because the exhaust air E defines the first heat source Hi, and the outside air O defines the second heat source H2, the adjustability of the air flow regulators 7, 8 allows the controller 16 to control the ratio of different heat sources Hi and H2.
[0058] The primary heat exchanger 11 is associated with a primary heating 17 circuit, and the secondary heat exchanger 12 is associated with a secondary heating circuit 18. The primary heat exchanger 11 brings thermal energy from the mixture of flows of exhaust air E and outside air O inside the mixing chamber 9 from the primary heating circuit 17 into the heat pump and heats a refrigerant that flows between the primary heat exchanger 11 and the secondary heat exchanger 12. The secondary heat exchanger 12 of the heat pump transfer the heat stored in the refrigerant into a medium circulating in the secondary heating circuit 18. This medium may be used to heat tap water, for example for a central heating system 19, or stored inside a heat buffer 20 in the form of a water tank 21.
[0059] In a preferred embodiment, the controller 16 is configured to control a setting of the first 7 and the second air flow regulator 8, and also a speed of the fan 14.
[0060] Downstream of the primary heat exchanger 11 is a plenum 22 that is in fluid connection with an outlet 23, where exhaust air E, after heat being extracted therefrom by said primary heat exchanger 11 , is expelled from the building 1 as waste.Figs. 2 and 3 show two alternative embodiments of a indoor exhaust air heat pump system 2 that only differ in that the embodiment of Fig. 2 comprises the first and second air flow regulators 7, 8 integrated inside the housing 10 of the indoor exhaust air heat pump 4. The alternative embodiment shown in Fig. 3 shows that it is also conceivable that at least one of the first and second air flow regulators 7, 8 is arranged outside the housing 10. In Fig. 3, both of the first and second air flow regulators 7, 8 are arranged outside the housing 10, inside the ducts 24, 25 that are associated with the first inlet 5 of exhaust air E, and the second inlet 6 of outside air O, respectively. The following description of the heat pump system 2, and in particular of the first and second air flow regulators 7, 8 thereof, applies to both alternative embodiments of Figs. 2 and 3.
[0061] As shown in Fig. 4B and 4C, the first and the second air flow regulator 7, 8 are adjustable in a plurality of intermediate states between the opened state (shown in Fig. 4A) and the closed state (shown in Fig. 4D) to enable the indoor exhaust air heat pump system 2 to set a state that gives preference to the first heat source Hi and supplement the air flow rate of the first heat source Hi with a supplementary flow rate of the second heat source H2 to obtain a balance between the first heat source Hi and the second heat source H2 that optimizes performance and / or acoustics. These intermediate states define a plurality of intermediate positions between the opened state and the closed state. The intermediate positions may be discrete positions, but more preferably, the first air flow regulator 7 and / or the second air flow regulator 8 are continuously adjustable between the opened state (shown in Fig. 4A) and the closed state (shown in Fig. 4D) to enable the indoor exhaust air heat pump system 2 to set and continuously adjust a state that gives preference to the first heat source Hi and supplement the air flow rate of the first heat source Hi with a supplementary flow rate of the second heat source H2 to obtain a balance between the first heat source Hi and the second heat source H2 that optimizes performance and / or acoustics. A continuous adjustability allows the air flow to be accurately controlled.
[0062] Fig. 5 shows a detailed schematic view of the first air flow regulator 7. It is remarked that the second air flow regulator 8 mainly differs from the first air flow regulator 7 because it lacks a flow sensor 26 the shown embodiments. An alternative flow sensor, or possibly with a similar flow sensor arrangement, may however optionally be applied as well in the second air flow regulator 8.The first air flow regulator 7 shown in Fig. 5 comprises a flow sensor 26 that is configured to determine a pre-selected flow rate of the exhaust air E of the indoor ventilation system 15. The pre-selected flow rate is a flow rate that is set by the ventilation air system 15, and is an air flow set point target value. This may be a manual selection by a user. For example, ventilation air systems 15 often have three ventilation states: a low, mid and high state. The high state is for example selected when a user takes a shower and wants to temporary increase the ventilation of the bathroom. Modern ventilation air systems 15 may however also use additional sensors, such as CO2 sensor, to automatically adjust the pre-selected flow rate of the ventilation air system 15.
[0063] Using a flow sensor 26 allows the controller 16 to automatically adjust the first and the second air flow regulator 7, 8, and preferably also the fan speed 14, to set the indoor exhaust air heat pump system 2 in a setting for optimizing at least one of energy performance, acoustic performance, and comfort levels.
[0064] In absence of such a flow sensor 26, an installer would have to configure the system before first use, and determine preferred settings for each ventilation state (low I mid I high) and store these preferred settings in the controller 16. This is a laborious process, that requires skilled installers, and is prone to errors. Moreover, the flow rate of the exhaust air E of the indoor ventilation system 15 may change over time due to a gradually clogging up of air ducts or air inlets. As a result of such clogging up, the ideal settings for the fixed ventilation states (low I mid I high) may also shift over time.
[0065] It is envisaged that the level of automation of ventilation air systems 15 will increase in the future based on the above mentioned additional sensors, such as CO2 sensors. As a result, it is likely that ventilation air systems 15 will have more settings than the currently common three states mid I low I high, thereby exponentially increasing the workload to be done when configuring the indoor exhaust air heat pump system 2 for first use. The use of a flow sensor 26 prevents the need to determine and store preferred settings for each possible ventilation state.
[0066] If the pre-selected flow rate of the exhaust air E is known to the controller 16, it may take control actions in dependency of this pre-selected flow rate. This allows the controller 16 to increase and maintain comfort levels, and in particular prevent that the exhaust air flow rate exceeds a predetermined desired maximum level. If too muchventilation occurs, additional outside air is drawn into the building 1, possibly undesirably cooling down the building 1, or causing draught.
[0067] It is particularly advantageous if the indoor exhaust air heat pump system 2 combines a flow sensor 26 with the first air flow regulator 7 and / or the second air flow regulator 8 being continuously adjustable between the opened state and the closed state.
[0068] In the shown preferred embodiments, the flow sensor 26 is arranged downstream of an air filter 27. A screen 28, that promotes the flow of exhaust air E to become more laminar, may be arranged intermediate the air filter 27 and the flow sensor 26. The flow sensor 26 is arranged inside an air guide 29 that has a funnel shape. The combination of the air guide 29 and the flow sensor 26 defines a flow sensor arrangement 30.
[0069] Due to the funnel shaped air guide 29, air flowing through the air filter 27, that is arranged upstream relative to the flow sensor 26, is condensed and accelerated. Due to the condensing aspect, the air flow in a relative large area is measured, thereby minimizing any potentially disturbing effects from a variance in filter positioning and minimizing any influence of the ducts 24 connecting the indoor exhaust air heat pump system 2. Moreover, the narrowing down of the funnel shaped air guide 29 accelerates the air flow via the venturi effect, thereby increasing the resolution of the flow sensor 26. More in particular the increased air speed of the air flow inside the funnel shaped air guide 29 allows for more accurate measurements, even when the air speed inside the duct 24 is low.
[0070] The controller 16 is configured to control the setting of the first air flow regulator 7 and the second air flow regulator 8 based on the air flow rate measured by the flow sensor 26, to thereby maintain the flow rate of the exhaust air E of the indoor ventilation system 15 within a predetermined bandwidth, in particular 15%, preferably 10%, of the pre-selected flow rate. In this way, the indoor exhaust air heat pump system 2 has only a limited effect on the ventilation rate inside the building 1, that will very likely not even be noticed by users of said building 1. In this way, the indoor exhaust air heat pump system 2 will have no noticeable effect on ventilation comfort levels.
[0071] When there is no heat demand the controller 16 is preferably configured to:- set the first air flow regulator 7 in the opened state (conform Fig. 4A) thereof; - set the second air flow regulator 8 in the closed state (conform Fig. 4D) thereof; and
[0072] - drive the fan 14 at a speed corresponding to of the pre-selected flow rate of the exhaust air E of the indoor ventilation system 15 measured by the flow sensor 26.
[0073] When there is a limited heat demand, the controller 16 is preferably configured to:
[0074] - set the first air flow regulator 7 in the opened state (conform Fig. 4A) thereof; - set the second air flow regulator 8 in an intermediate state (conform e.g. Figs.
[0075] 4B or 4C) in between the opened state and the closed state to allow outside air O to be drawn in by the fan 14;
[0076] - activate the compressor 13 of the indoor exhaust air heat pump 4; and - drive the fan 14 at an increased speed corresponding to a sum of the preselected flow rate of the exhaust air E and a flow rate of the outside air O. The flow rate of the outside air O may be measured with a (not shown) flow sensor, or calculated via software, for example based on actual settings of the compressor 13 and the temperature of the outside air O, e.g. measured with a temperature sensor 38. A limited heat demand may be qualified as a heat demand in the range of 20 - 70%, with 0% indicating no heat demand, and 100% indicating a maximum heat demand. A maximum heat demand may be qualified as when the compressor 13 of the indoor exhaust air heat pump system 2 is running at maximum speed. For smaller buildings, the maximum exhaust air flow rate is limited relative to larger buildings. For this reason, outside air O will have to be used sooner as a supplementary heat source H2 for smaller buildings. For example, if the indoor exhaust air heat pump system 2 has a capacity of 5 kW, and the exhaust air E of the indoor ventilation system 15 of a small building is capable of providing only 2 kW, the remaining 3 kW may be supplemented by outside air O. However, for a large building the exhaust air E of the indoor ventilation system 15 alone may already be capable of providing 3 or even 4 kW.
[0077] When there is a maximum heat demand, the controller 16 may be set according to two options. In a first, and most preferred option, the controller 16 is configured to, when there is a maximum heat demand:
[0078] - set the first air flow regulator 7 in the opened state (conform Fig. 4A) thereof;- set the second air flow regulator 8 in the opened state (conform Fig. 4A), or in an intermediate state close to the opened state, to allow outside air O to be drawn in by the fan 14; and
[0079] - drive the fan 14 at an increased speed corresponding to a sum of the preselected flow rate of the exhaust air E and a flow rate of the outside air O.
[0080] However, according to a second option, the controller 16 may be configured to, when there is a maximum heat demand:
[0081] - set the first air flow regulator 7 in an intermediate state in between the opened state and the closed state to thereby partially restrict the inflow of exhaust air E;
[0082] - set the second air flow regulator 8 in the opened state, or in an intermediate state close to the opened state, to allow outside air O to be drawn in by the fan 14; and
[0083] - drive the fan 14 at an increased speed corresponding to a sum of the preselected flow rate of the exhaust air E and a flow rate of the outside air O.
[0084] In the preferred embodiments shown in Figs. 2-6, at least one of the first air flow regulator 7 and the second air flow regulator 8 comprises a plurality of louvres 31 that acts as a valve 37. In the opened state (conform Fig. 4A), the opening between adjacent louvres 31 is maximized to allow the air E, O to flow freely through the air flow regulator 7, 8. In the closed state (conform Fig. 4D), the opening between adjacent louvres 31 is minimized to substantially block, or greatly restrict, the air E, O to flow through the air flow regulator 7, 8. The intermediate states (e.g. shown in Figs.4B and 4C), starting from the opened state towards the closed state, define successive states wherein opening between adjacent louvres 31 is gradually decreased to thereby restrict the air flow e, O more and more towards the closed state (conform Fig. 4D). In order to influence the opening between adjacent louvres 31, they are rotated.
[0085] As can be best shown in Fig. 4C, adjacent louvres 31 of the plurality of louvres 31 are configured to counter rotate relative to each other when the air flow regulator 7, 8 is adjusted between states thereof. In this way, the plurality of louvres 31 promote an even flow condition, that is largely independent of the orientation of the louvres 31. After all, by counter rotating adjacent louvres 31 of the plurality of louvres relative to each other, it is guaranteed that the air flow E, O is only influenced in a very limited manner. This can be best understood by imagining an alternative - and not recommended - configuration wherein all louvres 31 would rotate in the samedirection: the air flow would be guided along the louvres 31, and therefore directed in different orientations in dependence of the actual orientation of the louvres 31. As a result, the exhaust air flow E encountered by the flow sensor 26 would be influenced by the orientation of the louvres 31, thereby reducing the accuracy and reliability of the flow sensor 26. However, if adjacent louvres 31 counter rotate according to the invention, the direction of the exhaust air flow E is hardly influenced, because guiding effects are averaged out.
[0086] In the first and second preferred embodiments, the first air flow regulator 7 and the second air flow regulator 8 comprise a housing 32 that is wedge shaped. This is best shown in the perspective view of the first art flow regulator 7 in Fig. 6. A first side 33 that defines an inlet 34 and a second side 35 that defines an outlet 36 enclose a sharp angle a (indicated in Fig. 5) in the range of 15° - 55°, preferably 20° - 50°, and most preferably 30° - 40°. The plurality of louvres 31 are arranged at the second side 35.
[0087] In the first preferred embodiment shown in Fig. 2, the housing 10 of the indoor exhaust air heat pump 4 further comprises the first air flow regulator 7, the second air flow regulator 8, and the mixing chamber 9. In this way, the air flow regulators 7, 8 are integrated inside the housing 10. In this way, installing the indoor exhaust air heat pump system 2 may be simplified, and will be less prone to errors.
[0088] It is however also conceivable that at least one of the first air flow regulator 7 and the second air flow regulator 8 of the indoor exhaust air heat pump system 2 is arranged outside the housing 10 of the exhaust air heat pump 4. In the second preferred embodiment shown in Fig. 3, both the first air flow regulator 7 and the second air flow regulator 8 are arranged outside the housing 10.
[0089] A third preferred embodiment is shown in Fig. 7. In this alternative embodiment, the indoor exhaust air heat pump system 2 comprises a single valve 37. By positioning this valve 37, the ratio of exhaust air E relative to outside air O may be set, while a setting of the fan speed of the fan 14 allows to further control the air flows of the exhaust air E and outside air O. It is furthermore mentioned that the fan 14 is shown upstream of the primary heat exchanger 11. This positioning of the fan 14 is an alternative positioning that may also be applied in the first or second preferred embodiments. Likewise, it is also conceivable that the fan 14 is arranged downstream of the primary heat exchanger 11 in the third preferred embodiment.The invention further relates to a method of controlling the indoor exhaust air heat pump 4, comprising the steps of:
[0090] - supplying exhaust air E of an indoor ventilation system 15 that defines a first heat source Hi for a primary heat exchanger 11 of an indoor exhaust air heat pump system 2;
[0091] - supplying outside air O that defines a second heat source H2 for the primary heat exchanger 11;
[0092] - with a flow sensor 26, measuring an air flow rate of exhaust air E of the indoor ventilation system 15 to determine a pre-selected flow rate of the exhaust air E of the indoor ventilation system 15;
[0093] - based on the air flow rate determined by the flow sensor 26:
[0094] - regulating the flow rate of exhaust air E originating from the indoor ventilation system 15, that defines the first heat source Hi;
[0095] - independently of the flow rate of exhaust air E, regulating the flow rate of outside air O, that defines the second heat source H2;
[0096] - providing a mixture by mixing the exhaust air E and the outside air O; and - heating a heat exchanger 11 of the heat pump 4 with the mixture.
[0097] The method preferably further comprises the steps of:
[0098] - prior to the step of regulating the flow rate of exhaust air E, determining a preselected flow rate of said exhaust air E of the indoor ventilation system 15; and
[0099] - independently regulating the flow rates of the exhaust air E and the outside air O to maintain the flow rate of the exhaust air E of the indoor ventilation system 15 within a predetermined bandwidth, in particular 15%, preferably 10%, of the preselected flow rate.
[0100] The method preferably comprises the steps of: controlling the indoor exhaust air heat pump 4, and thereby performing the steps of the controller 16 as discussed above for one or more of the conditions: minimum heat demand, limited heat demand, and maximum heat demand.
[0101] Although they show preferred embodiments of the invention, the above described embodiments are intended only to illustrate the invention and not to limit in any way the scope of the invention. Accordingly, it should be understood that where features mentioned in the appended claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of the claims and arein no way limiting on the scope of the claims. Furthermore, it is particularly noted that the skilled person can combine technical measures of the different embodiments. The scope of protection is defined solely by the following claims.
Claims
CLAIMS1. Indoor exhaust air heat pump system, comprising:- an indoor exhaust air heat pump, having a housing that comprises a primary heat exchanger and a secondary heat exchanger, a compressor, and a fan;- a first air inlet configured to be connected to an indoor ventilation system of a building, wherein exhaust air of said indoor ventilation system defines a first heat source for the primary heat exchanger;- a second air inlet configured to be in fluid connection with outside air that defines a second heat source for the primary heat exchanger;- a flow sensor configured to measure an air flow rate to determine a pre-selected flow rate of the exhaust air of the indoor ventilation system;- a first air flow regulator that is in fluid connection with the first air inlet, and that is configured to control a flow rate of exhaust air passing therethrough;- a second air flow regulator that is in fluid connection with the second air inlet, and that is configured to control a flow rate of outside air passing therethrough;- a mixing chamber that is arranged downstream of the first and the second air flow regulator, and upstream of the primary heat exchanger;- wherein the first and the second air flow regulator are adjustable between an opened state and a closed state, and at least one intermediate state therebetween; and- wherein the system further comprises a controller that is communicatively connected to the flow sensor, wherein the controller is configured to independently adjust the first air flow regulator and the second air flow regulator based on the air flow rate of the exhaust air measured by the flow sensor, to thereby maintain the measured air flow rate of the exhaust air within a predetermined bandwidth of a pre-selected flow rate of the exhaust air of the indoor ventilation system.
2. Indoor exhaust air heat pump system according to claim 1, wherein the first and the second air flow regulator are adjustable in a plurality of intermediate states between the opened state and the closed state to enable the indoor exhaust air heat pump system to select a state that gives preference to the first heat source andsupplement the air flow rate of the first heat source with a supplementary flow rate of the second heat source to obtain a balance between the first heat source and the second heat source that optimizes performance and / or acoustics.
3. Indoor exhaust air heat pump system according to claim 1 or 2, wherein the first and / or the second air flow regulator is continuously adjustable between the opened state and the closed state to enable the indoor exhaust air heat pump system to set and continuously adjust a state that gives preference to the first heat source and supplement the air flow rate of the first heat source with a supplementary flow rate of the second heat source to obtain a balance between the first heat source and the second heat source that optimizes performance and / or acoustics.
4. Indoor exhaust air heat pump system according to any of the foregoing claims, wherein the first air flow regulator comprises the flow sensor that is configured to determine the pre-selected flow rate of the exhaust air of the indoor ventilation system.
5. Indoor exhaust air heat pump system according to claim 4, wherein the flow sensor is arranged downstream of an air filter.
6. Indoor exhaust air heat pump system according to claim 4 or 5, wherein a screen is arranged intermediate the air filter and the flow sensor.
7. Indoor exhaust air heat pump system according to any of claims 4-6, wherein the flow sensor is arranged inside an air guide that has a funnel shape.
8. Indoor exhaust air heat pump system according to any of claims 4-7, wherein the predetermined bandwidth is 15%, and preferably 10%, of the pre-selected flow rate of the exhaust air.
9. Indoor exhaust air heat pump system according to claim 8, wherein the controller is configured to, when there is no heat demand:- set the first air flow regulator in the opened state thereof;- set the second air flow regulator in the closed state thereof; and - drive the fan at a speed corresponding to of the pre-selected flow rate of the exhaust air of the indoor ventilation system measured by the flow sensor.
10. Indoor exhaust air heat pump system according to claim 8 or 9, wherein the controller is configured to, when there is a limited heat demand:- set the first air flow regulator in the opened state thereof;- set the second air flow regulator in an intermediate state in between the opened state and the closed state to allow outside air to be drawn in by the fan;- activate the compressor of the indoor exhaust air heat pump; and - drive the fan at an increased speed corresponding to a sum of the preselected flow rate of the exhaust air and a flow rate of the outside air.
11. Indoor exhaust air heat pump system according to any of claims 8-10, wherein the controller is configured to, when there is a maximum heat demand:- set the first air flow regulator in the opened state thereof;- set the second air flow regulator in the opened state, or in an intermediate state close to the opened state, to allow outside air to be drawn in by the fan; and- drive the fan at an increased speed corresponding to a sum of the preselected flow rate of the exhaust air and a flow rate of the outside air.
12. Indoor exhaust air heat pump system according to any of claims 8-10, wherein the controller is configured to, when there is a maximum heat demand:- set the first air flow regulator in an intermediate state in between the opened state and the closed state to thereby partially restrict the inflow of exhaust air;- set the second air flow regulator in the opened state, or in an intermediate state close to the opened state, to allow outside air to be drawn in by the fan; and - drive the fan at an increased speed corresponding to a sum of the pre-selected flow rate of the exhaust air and a flow rate of the outside air.
13. Indoor exhaust air heat pump system according to any of the foregoing claims, wherein at least one of the first air flow regulator and the second air flow regulator comprises a plurality of louvres.
14. Indoor exhaust air heat pump system according to claim 13, wherein adjacent louvres of the plurality of louvres are configured to counter rotate relative to each other when the air flow regulator is adjusted between states thereof.
15. Indoor exhaust air heat pump system according to claim 13 or 14, wherein the first air flow regulator and the second air flow regulator comprise a housing that is wedge shaped, wherein:- a first side that defines an inlet and a second side that defines an outlet enclose a sharp angle a in the range of 15° - 55°, preferably 20° - 50°, and most preferably 30° - 40°.
16. Indoor exhaust air heat pump system according to claim 15, wherein the plurality of louvres are arranged at the second side.
17. Indoor exhaust air heat pump system according to any of the foregoing claims, wherein the housing of the indoor exhaust air heat pump further comprises the first air flow regulator, the second air flow regulator, and the mixing chamber.
18. Indoor exhaust air heat pump system according to any of the foregoing claims, comprising:- one or more than one further air inlet configured to be connected to an indoor ventilation system of a building, wherein exhaust air of said indoor ventilation system defines a further heat source for the primary heat exchanger;- wherein each further air inlet comprises a further air flow regulator that is in fluid connection with the one or more than one further air inlet, and that is configured to control a flow rate of exhaust air passing therethrough; and- wherein each further air inlet corresponds to a further flow sensor configured to measure an air flow rate to determine a pre-selected flow rate of the exhaust air of the indoor ventilation system.
19. Method of controlling an indoor exhaust air heat pump, comprising the steps of:- supplying exhaust air of an indoor ventilation system that defines a first heat source for a primary heat exchanger of an indoor exhaust air heat pump system;- supplying outside air that defines a second heat source for the primary heat exchanger;- with a flow sensor, measuring an air flow rate of exhaust air of the indoor ventilation system to determine a pre-selected flow rate of the exhaust air of the indoor ventilation system;- based on the measured air flow rate, independently regulating a flow rate of exhaust air originating from an indoor ventilation system, that defines the first heat source, and a flow rate of outside air, that defines the second heat source, to thereby maintain the measured air flow rate of the exhaust air of the indoor ventilation system within a predetermined bandwidth of a pre-selected flow rate;- providing a mixture by mixing the exhaust air and the outside air; and - heating a heat exchanger of the heat pump with the mixture.
20. Method according to claim 19, wherein the predetermined bandwidth is 15%, and preferably 10%, of the pre-selected flow rate.
21. Method according to claim 20, comprising the steps of:- controlling an indoor exhaust air heat pump system according to any of the foregoing claims 1-18.