Evaporator for air-source heat pumps

Abstract

Apparatus for evaporating water condensate produced by an air-source heat pump, such as an air conditioner, the apparatus having a housing adapted, in use, to be positioned below the condensate drain of a heat pump, a condensate container within or forming part of the housing for collecting condensate, the container having a deep end and a shallow end, means for detecting when a minimum level of water is in the container and for sending signals indicative thereof to an electronic control unit (ECU), and electric heater means for heating, either directly or indirectly, the water to cause evaporation thereof in response to command signals from the ECU. In a first aspect the housing and container has a lid with an opening to receive liquid condensate remote from the heat pump and in a second aspect the apparatus is adapted to be fitted directly to the underside of a pre-installed heat pump.

Description

[0001] This invention relates to air-source heat pumps for heating or cooling rooms within a building.BACKGROUND OF THE INVENTION

[0002] Air-source heat pumps are becoming increasingly popular as a cost-effective means of heating or cooling rooms within a building because they are relatively compact. They are especially useful for use in high-rise residential and office buildings since they do not require substantial infrastructure for their installation, unlike ground-source heat pumps which require extensive works below ground to install pipework for containing a working fluid for exchanging heat with the ground soil. Air-source heat pumps only require sufficient space for an external fan with which to blow ambient air over the finned surfaces of a heat exchanger containing the working fluid which fluid, with the aid of a compressor, is then used for warming or cooling air within the building via an internal fan. However, unlike ground-source heat pumps, air-source heat pumps usually produce condensate as a consequence of moisture within the ambient air condensing on the heat exchanger surfaces and forming droplets of water which can either be conveyed to a suitable drain or simply allowed to drip to the ground below. In either case the presence of the condensate is problematic, more particularly if it freezes during cold weather, in which case operation of the heat pump can be compromised.

[0003] A seemingly obvious solution to the problem of collecting condensate dripping from a heat pump would be to use a container such as a metal tray positioned below the heat pump and heated by means of an electric heater below the tray and operable whenever a minimum level of water is sensed in the tray, the water thereby being forcibly evaporated to ambient air. However, this seemingly simple solution overlooks the fact that water has a relatively high specific heat capacity, meaning that vaporisation requires significant energy. For example, where the mains supply to a domestic building is 230V it is found that for a heat pump requiring, say, 23 A the spare current for heating the water is only approximately 3.5 A or a maximum of 800 W. When this amount of power is spread over a relatively large surface area such as the underside of the collection tray an inordinate amount of time is required to bring the volume of water up to or near boiling point and to maintain it at that level during evaporation of the condensate, particularly if ambient temperature is low. Furthermore, even if the water collection tray is positioned perfectly horizontally below the heat pump, a sufficient depth of water must always be present in order to avoid the risk of hotspots occurring which could cause damage to the heater and pose a safety hazard if flammable materials such as thermal insulation and plastics are nearby. Accordingly, such an arrangement would always require a relatively large volume of water in the tray and when the sensed level of water falls below the safe minimum for operating the heater and the heater is switched off, this volume of water quickly cools due to the large surface area exposed to ambient air, wasting energy as it does so. As a consequence, if the sensed water level in the tray rises above the minimum required for activating the heater the cooled water has to be reheated to almost boiling point before any substantial evaporation can occur such that the overall thermodynamic efficiency is very poor. There is the further point in that if the ambient temperature is at or below freezing point this could also cause freezing of the condensate in the tray and condensate in the drainage pipework from the heat pump, causing potential damage thereto.

[0004] The present invention is derived from the realization that there is a need for obviating the problem of disposing of condensate from air source heat pumps in a more energy efficient manner in which the foregoing disadvantages are obviated.

[0005] In this patent specification the term “heat pump” is intended to mean an air-source heat pump for heating or cooling enclosed spaces including for the purposes of air conditioning and refrigerating in which at least part of the heat pump is partially exposed to ambient air and ambient air temperatures.SUMMARY OF THE INVENTION

[0006] According to a first aspect of the invention there is provided apparatus for evaporating water condensate produced by an air-source heat pump, the apparatus having a housing adapted, in use, to be positioned below the condensate drain of a heat pump, a condensate container within or forming part of the housing for collecting condensate, the container having a deep end and a shallow end, means for detecting when a minimum level of water is in the container and for sending signals indicative thereof to an electronic control unit (ECU), and electric heater means for heating, either directly or indirectly, the water to cause evaporation thereof in response to command signals from the ECU.

[0007] According to a second aspect of the invention there is provided apparatus for evaporating water condensate produced by an air-source heat pump of the type having a generally sealed base with a drain for removing liquid condensate, the apparatus having a housing adapted to be positioned below the condensate drain of the heat pump, a condensate container within or forming part of the housing for collecting condensate from the heat pump, the container having a deep end and a shallow end, means for detecting when a minimum level of water is in the container and for sending signals indicative thereof to an electronic control unit (ECU), and electric heater means for heating, either directly or indirectly, the water to cause evaporation thereof in response to command signals from the ECU.

[0008] Conveniently, the container has generally upright sidewalls, a generally flat base disposed at an angle to the horizontal, such as between about 10° and 15° but preferably about 12°, and a lid to thereby define in combination a hollow housing of frusto-triangular cross-section. With this arrangement condensate from the heat pump is directed initially into the deep end of the container, thereby making it possible for heating means targeted at that region of the base only to begin the evaporation process without wasting energy heating other parts of the base, and when the volume of condensate is too great for efficient heating and evaporation by the targeted heating means one or more other heating means may be used to heat the water condensate as its level rises and its surface area is increased. The heated and evaporated condensate is suitably expelled from the container via a vent in one of the sidewalls, thereby ensuring that contamination of the heat pump is avoided.

[0009] Preferably, the means for heating the collected condensate comprises a plurality of electric strip heaters, such as three silicone 260 W heaters, arranged to heat the underside of the condensate container base, which is suitably made for a metal such as stainless steel, with a first strip heater extending along the deep end of the container, and successive strip heaters extending parallel thereto up to the shallow end of the container.

[0010] The command signals from the ECU to each strip heater are preferably independently variable to provide, if necessary, pulsed activation of each strip heater, the duration of each activation pulse being dependent upon the sensed temperature. Preferably, each strip heater is provided with means for sensing temperature, such as through the use of a negative temperature coefficient thermistor (NTC) in which electrical resistance decreases as temperature increases, thereby enabling the ECU to independently manage the temperature of each heater. When water is detected in the container the heaters are activated until they reach the chosen temperature, typically 140° C., whereafter they are operated in a pulsed manner in order to maintain the chosen temperature. With such an arrangement the temperature profile at the base of the container can be monitored and managed to ensure that energy is not being wasted, while still ensuring that the water is kept at or near boiling point during an evaporation cycle in order to maximise the speed of evaporation without wasting energy.

[0011] The means for detecting when a sufficient level of condensate is in the container to justify commencement of an evaporation cycle conveniently comprises a pair of electrodes disposed within the container, such as a twin-core cable having a pair of insulated wires therewithin, one of which wires being longer than the other so as to provide a gap therebetween, with the electrodes being operatively connected to the ECU to thereby form an open circuit closable by the presence of condensate water therebetween and, if so, to activate the heater means.

[0012] Preferably, where the container is not integrally formed with the housing such that a void exists therebetween it is at least partially filled with thermal insulation, such as open cell insulation, which may conveniently also serve to retain the strip heaters in position below the base of the container and in close contact therewith.

[0013] With this arrangement a relatively lightweight but useful attachment can be easily fitted below a pre-installed air-source heat pump, or the apparatus of the invention may be added to or made integral with a new heat pump before it is installed in or on a building, in each case neatly solving the problem of how to remove condensate, by detecting a minimum level of condensate water within the container and heating it evenly and rapidly with strip heaters operating at a temperature of typically around 140° C., sufficient to ensure an adequate rate of evaporation and thereafter managing the heater means to ensure each evaporation cycle is completed efficiently and safely.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0015] FIG. 1 is a front view of part of conventional wall-mounted air source heat pump apparatus to which the evaporator apparatus of the invention has been attached,

[0016] FIG. 2 is a side view of the apparatus of FIG. 1,

[0017] FIG. 3 is a sectional side view of the evaporator apparatus to be fitted to the lower part of a heat pump apparatus,

[0018] FIG. 4 is a plan view of an electric strip heater array and associated ECU for use with the invention,

[0019] FIG. 5 is a plan view showing the wiring harness arrangement for the water detection means, and

[0020] FIG. 6 shows a sectional side view of the apparatus of the invention connected to the condensate water outlet pipe of a heat pump.DETAILED DESCRIPTION OF THE INVENTION

[0021] Referring firstly to FIGS. 1 and 2 a conventional air-source heat pump shown generally at 1 is mounted on and through an external wall surface of a building and includes therewithin an electrically operable fan for directing ambient air over the fins of a heat exchanger containing a working fluid convertible from liquid to gas and vice versa by means of a compressor for heating or cooling an enclosed space such as a room within the building, all in a known manner. Depending upon ambient temperature and humidity, this produces varying amounts of condensation which, in turn, produces condensate in the form of water or water droplets which, ordinarily, is either allowed to drip from the bottom of the heat pump to the ground or be collected and piped to a remote location, such as a drain in the ground or a condensate collection container. However, this is avoided by the placement of the evaporator apparatus 2 of the invention immediately below the heat pump 1 whereby to collect the condensate and evaporate it in situ.

[0022] FIG. 3 is an enlarged cross-sectional side view of the condensate evaporator apparatus 2 of the invention contained within a housing 3 within which is disposed a stainless steel container 4 in the form of a basin of generally frusto-triangular cross-sectional shape for collecting liquid condensate in a manner to be described. The container 4 has upright sidewalls 4a, 4b of differing heights and a flat base 4c set at an angle to the horizontal by about 12° such that the container has a shallow end adjacent sidewall 4a and a deep end adjacent sidewall 4b. The container 4 is closed by a lid 5 which also extends over the upper part of the housing 3. On the upper surface of the container base 4c is disposed water sensor means 6 for detecting the presence of water within the container, the sensor means being in the form of a twin core insulated electric cable with exposed wires defining a pair of electrodes 6a, 6b which form part of an open circuit with the ECU, between which electrodes water can accumulate to close the circuit. On the lower surface of the container base 4c is disposed an array of three silicone strip heaters 7a, 7b, 7c to be described in more detail in FIG. 4. Extending through an upper part of the sidewall 4b is a vent pipe 8 operable, in use, to permit the release to ambient air of evaporated condensate from within the container 4. Between the outer walls of the container 4 and the inner walls of the housing 3 is a layer of open-cell foam 9 which serves to thermally insulate the container 4 and also retain the strip heaters 7a, 7b, 7c, in the positions shown in which they are in intimate thermal contact with the base 4c of the container 4.

[0023] FIG. 4 is a plan view of the array of three strip heaters 7a, 7b, 7c shown in FIG. 3 electrically connected to an electronic control unit (ECU) 10, as is also an array of three NTC thermistors 11a, 11b, 11c, operable to sense the temperature of each respective strip heater, thereby allowing the ECU to thermally manage the strip heaters and the base 4c of the container 4.

[0024] FIG. 5 is a plan view of the housing 3 and container 4 with the lid 5 removed to reveal a schematic view of the wiring harness of the water sensor means 6 electrically connected to the ECU 10 and secured to the inside base 4c of the container 4 below the condensate outlet hose 12 of the heat pump 1 shown in FIGS. 1 & 2. The electrodes 6a, 6b, are electrically insulated from each other but are otherwise exposed such that upon water being detected between them the previously open circuit is closed, thereby indicating to the ECU 10 the presence of water and the need for the commencement of an evaporation cycle.

[0025] FIG. 6 is a sectional side view of the container 4 and lid 5 into and through which has been received the condensate outlet hose 12 from the heat pump 1 shown in FIGS. 1 & 2. The outlet end 12a of the outlet hose 12 is below the level of the water sensor 6 such that the presence of water can only be detected when sufficient water has accumulated at the deep end of the container 4. However, because of the angled orientation of the base 4c of the container 4 only a relatively small volume of water, typically 0.1 L of water, need be collected in this region before the water level is high enough to be sensed by the sensor means 6. This can be contrasted to the amount of water necessary for safe operation of a corresponding prior art evaporator apparatus with a container having a flat base disposed generally horizontally, where the water is evenly distributed over a much wider area and in order to ensure safe operation which avoids hot-spots occurring and possible burnout of the heater means a much larger volume of water is required where, in practice, it has been found that a minimum volume of 0.5 L is required. Such a relatively large volume of water is not particularly problematic at temperatures above freezing but at or below freezing it can become problematic if the collected condensate water freezes and the condensate pipe from the heat pump becomes blocked. However, of more concern from an energy perspective is that an evaporator requiring the presence of such a volume of water before it is detected necessarily has to heat the water to at or near boiling point every time condensate is detected and an evaporation cycle is required, which is wasteful of energy.

[0026] In operation, once the presence of water has been detected by the water sensor means 6 the strip heaters 7a, 7b, 7c, are activated by the ECU 10 until they have reached a chosen temperature, preferably around 140° C., following which, each heater is pulsed on and off to maintain the chosen temperature. After the required amount of evaporation has been detected by the absence of water between the electrodes 6a, 6b, the strip heaters are left on for a suitable period, such as 30 minutes, to evaporate the relatively minor amount of condensate remaining in the container 4.

[0027] By recognising that conventional condensation evaporators have condensate collection containers of uniform height in the form of a horizontally flat base and upright sides there is always the need to heat a relatively large volume of water at the beginning of each evaporation cycle and that this problem can be solved by adopting the eloquently simple arrangement of the collection container having a shallow end and a deep end, this disadvantage can be avoided. As a consequence, a much smaller volume of water, requiring a correspondingly lower amount of power to heat it, is needed for the same purpose. Accordingly, the apparatus of the invention can be made sufficiently lightweight so as to permit convenient attachment to or adjacent a pre-installed heat pump due to the significantly smaller volume of water required before an evaporation cycle is triggered, being only about a fifth of the volume and hence weight of the minimum amount of water required as compared to the prior art evaporator apparatus previously described before an evaporation cycle commences. Similarly, as a consequence of the evaporator apparatus of the invention requiring a much reduced volume of water before triggering an evaporation cycle together with a reduced volume of condensate liquid being heated during the cycle as a consequence of the container having a shallow end the apparatus can be relatively lightweight, compact and unobtrusive when fitted to or forming part of a heat pump, as can be seen from FIGS. 1 and 2 while collectively removing the need for an unsightly condensate drainpipe to the ground.

Examples

Embodiment Construction

[0021]Referring firstly to FIGS. 1 and 2 a conventional air-source heat pump shown generally at 1 is mounted on and through an external wall surface of a building and includes therewithin an electrically operable fan for directing ambient air over the fins of a heat exchanger containing a working fluid convertible from liquid to gas and vice versa by means of a compressor for heating or cooling an enclosed space such as a room within the building, all in a known manner. Depending upon ambient temperature and humidity, this produces varying amounts of condensation which, in turn, produces condensate in the form of water or water droplets which, ordinarily, is either allowed to drip from the bottom of the heat pump to the ground or be collected and piped to a remote location, such as a drain in the ground or a condensate collection container. However, this is avoided by the placement of the evaporator apparatus 2 of the invention immediately below the heat pump 1 whereby to collect th...

[0001] This invention relates to air-source heat pumps for heating or cooling rooms within a building.BACKGROUND OF THE INVENTION

[0002] Air-source heat pumps are becoming increasingly popular as a cost-effective means of heating or cooling rooms within a building because they are relatively compact. They are especially useful for use in high-rise residential and office buildings since they do not require substantial infrastructure for their installation, unlike ground-source heat pumps which require extensive works below ground to install pipework for containing a working fluid for exchanging heat with the ground soil. Air-source heat pumps only require sufficient space for an external fan with which to blow ambient air over the finned surfaces of a heat exchanger containing the working fluid which fluid, with the aid of a compressor, is then used for warming or cooling air within the building via an internal fan. However, unlike ground-source heat pumps, air-source heat pumps usually produce condensate as a consequence of moisture within the ambient air condensing on the heat exchanger surfaces and forming droplets of water which can either be conveyed to a suitable drain or simply allowed to drip to the ground below. In either case the presence of the condensate is problematic, more particularly if it freezes during cold weather, in which case operation of the heat pump can be compromised.

[0003] A seemingly obvious solution to the problem of collecting condensate dripping from a heat pump would be to use a container such as a metal tray positioned below the heat pump and heated by means of an electric heater below the tray and operable whenever a minimum level of water is sensed in the tray, the water thereby being forcibly evaporated to ambient air. However, this seemingly simple solution overlooks the fact that water has a relatively high specific heat capacity, meaning that vaporisation requires significant energy. For example, where the mains supply to a domestic building is 230V it is found that for a heat pump requiring, say, 23 A the spare current for heating the water is only approximately 3.5 A or a maximum of 800 W. When this amount of power is spread over a relatively large surface area such as the underside of the collection tray an inordinate amount of time is required to bring the volume of water up to or near boiling point and to maintain it at that level during evaporation of the condensate, particularly if ambient temperature is low. Furthermore, even if the water collection tray is positioned perfectly horizontally below the heat pump, a sufficient depth of water must always be present in order to avoid the risk of hotspots occurring which could cause damage to the heater and pose a safety hazard if flammable materials such as thermal insulation and plastics are nearby. Accordingly, such an arrangement would always require a relatively large volume of water in the tray and when the sensed level of water falls below the safe minimum for operating the heater and the heater is switched off, this volume of water quickly cools due to the large surface area exposed to ambient air, wasting energy as it does so. As a consequence, if the sensed water level in the tray rises above the minimum required for activating the heater the cooled water has to be reheated to almost boiling point before any substantial evaporation can occur such that the overall thermodynamic efficiency is very poor. There is the further point in that if the ambient temperature is at or below freezing point this could also cause freezing of the condensate in the tray and condensate in the drainage pipework from the heat pump, causing potential damage thereto.

[0004] The present invention is derived from the realization that there is a need for obviating the problem of disposing of condensate from air source heat pumps in a more energy efficient manner in which the foregoing disadvantages are obviated.

[0005] In this patent specification the term “heat pump” is intended to mean an air-source heat pump for heating or cooling enclosed spaces including for the purposes of air conditioning and refrigerating in which at least part of the heat pump is partially exposed to ambient air and ambient air temperatures.SUMMARY OF THE INVENTION

[0006] According to a first aspect of the invention there is provided apparatus for evaporating water condensate produced by an air-source heat pump, the apparatus having a housing adapted, in use, to be positioned below the condensate drain of a heat pump, a condensate container within or forming part of the housing for collecting condensate, the container having a deep end and a shallow end, means for detecting when a minimum level of water is in the container and for sending signals indicative thereof to an electronic control unit (ECU), and electric heater means for heating, either directly or indirectly, the water to cause evaporation thereof in response to command signals from the ECU.

[0007] According to a second aspect of the invention there is provided apparatus for evaporating water condensate produced by an air-source heat pump of the type having a generally sealed base with a drain for removing liquid condensate, the apparatus having a housing adapted to be positioned below the condensate drain of the heat pump, a condensate container within or forming part of the housing for collecting condensate from the heat pump, the container having a deep end and a shallow end, means for detecting when a minimum level of water is in the container and for sending signals indicative thereof to an electronic control unit (ECU), and electric heater means for heating, either directly or indirectly, the water to cause evaporation thereof in response to command signals from the ECU.

[0008] Conveniently, the container has generally upright sidewalls, a generally flat base disposed at an angle to the horizontal, such as between about 10° and 15° but preferably about 12°, and a lid to thereby define in combination a hollow housing of frusto-triangular cross-section. With this arrangement condensate from the heat pump is directed initially into the deep end of the container, thereby making it possible for heating means targeted at that region of the base only to begin the evaporation process without wasting energy heating other parts of the base, and when the volume of condensate is too great for efficient heating and evaporation by the targeted heating means one or more other heating means may be used to heat the water condensate as its level rises and its surface area is increased. The heated and evaporated condensate is suitably expelled from the container via a vent in one of the sidewalls, thereby ensuring that contamination of the heat pump is avoided.

[0009] Preferably, the means for heating the collected condensate comprises a plurality of electric strip heaters, such as three silicone 260 W heaters, arranged to heat the underside of the condensate container base, which is suitably made for a metal such as stainless steel, with a first strip heater extending along the deep end of the container, and successive strip heaters extending parallel thereto up to the shallow end of the container.

[0010] The command signals from the ECU to each strip heater are preferably independently variable to provide, if necessary, pulsed activation of each strip heater, the duration of each activation pulse being dependent upon the sensed temperature. Preferably, each strip heater is provided with means for sensing temperature, such as through the use of a negative temperature coefficient thermistor (NTC) in which electrical resistance decreases as temperature increases, thereby enabling the ECU to independently manage the temperature of each heater. When water is detected in the container the heaters are activated until they reach the chosen temperature, typically 140° C., whereafter they are operated in a pulsed manner in order to maintain the chosen temperature. With such an arrangement the temperature profile at the base of the container can be monitored and managed to ensure that energy is not being wasted, while still ensuring that the water is kept at or near boiling point during an evaporation cycle in order to maximise the speed of evaporation without wasting energy.

[0011] The means for detecting when a sufficient level of condensate is in the container to justify commencement of an evaporation cycle conveniently comprises a pair of electrodes disposed within the container, such as a twin-core cable having a pair of insulated wires therewithin, one of which wires being longer than the other so as to provide a gap therebetween, with the electrodes being operatively connected to the ECU to thereby form an open circuit closable by the presence of condensate water therebetween and, if so, to activate the heater means.

[0012] Preferably, where the container is not integrally formed with the housing such that a void exists therebetween it is at least partially filled with thermal insulation, such as open cell insulation, which may conveniently also serve to retain the strip heaters in position below the base of the container and in close contact therewith.

[0013] With this arrangement a relatively lightweight but useful attachment can be easily fitted below a pre-installed air-source heat pump, or the apparatus of the invention may be added to or made integral with a new heat pump before it is installed in or on a building, in each case neatly solving the problem of how to remove condensate, by detecting a minimum level of condensate water within the container and heating it evenly and rapidly with strip heaters operating at a temperature of typically around 140° C., sufficient to ensure an adequate rate of evaporation and thereafter managing the heater means to ensure each evaporation cycle is completed efficiently and safely.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0015] FIG. 1 is a front view of part of conventional wall-mounted air source heat pump apparatus to which the evaporator apparatus of the invention has been attached,

[0016] FIG. 2 is a side view of the apparatus of FIG. 1,

[0017] FIG. 3 is a sectional side view of the evaporator apparatus to be fitted to the lower part of a heat pump apparatus,

[0018] FIG. 4 is a plan view of an electric strip heater array and associated ECU for use with the invention,

[0019] FIG. 5 is a plan view showing the wiring harness arrangement for the water detection means, and

[0020] FIG. 6 shows a sectional side view of the apparatus of the invention connected to the condensate water outlet pipe of a heat pump.DETAILED DESCRIPTION OF THE INVENTION

[0021] Referring firstly to FIGS. 1 and 2 a conventional air-source heat pump shown generally at 1 is mounted on and through an external wall surface of a building and includes therewithin an electrically operable fan for directing ambient air over the fins of a heat exchanger containing a working fluid convertible from liquid to gas and vice versa by means of a compressor for heating or cooling an enclosed space such as a room within the building, all in a known manner. Depending upon ambient temperature and humidity, this produces varying amounts of condensation which, in turn, produces condensate in the form of water or water droplets which, ordinarily, is either allowed to drip from the bottom of the heat pump to the ground or be collected and piped to a remote location, such as a drain in the ground or a condensate collection container. However, this is avoided by the placement of the evaporator apparatus 2 of the invention immediately below the heat pump 1 whereby to collect the condensate and evaporate it in situ.

[0022] FIG. 3 is an enlarged cross-sectional side view of the condensate evaporator apparatus 2 of the invention contained within a housing 3 within which is disposed a stainless steel container 4 in the form of a basin of generally frusto-triangular cross-sectional shape for collecting liquid condensate in a manner to be described. The container 4 has upright sidewalls 4a, 4b of differing heights and a flat base 4c set at an angle to the horizontal by about 12° such that the container has a shallow end adjacent sidewall 4a and a deep end adjacent sidewall 4b. The container 4 is closed by a lid 5 which also extends over the upper part of the housing 3. On the upper surface of the container base 4c is disposed water sensor means 6 for detecting the presence of water within the container, the sensor means being in the form of a twin core insulated electric cable with exposed wires defining a pair of electrodes 6a, 6b which form part of an open circuit with the ECU, between which electrodes water can accumulate to close the circuit. On the lower surface of the container base 4c is disposed an array of three silicone strip heaters 7a, 7b, 7c to be described in more detail in FIG. 4. Extending through an upper part of the sidewall 4b is a vent pipe 8 operable, in use, to permit the release to ambient air of evaporated condensate from within the container 4. Between the outer walls of the container 4 and the inner walls of the housing 3 is a layer of open-cell foam 9 which serves to thermally insulate the container 4 and also retain the strip heaters 7a, 7b, 7c, in the positions shown in which they are in intimate thermal contact with the base 4c of the container 4.

[0023] FIG. 4 is a plan view of the array of three strip heaters 7a, 7b, 7c shown in FIG. 3 electrically connected to an electronic control unit (ECU) 10, as is also an array of three NTC thermistors 11a, 11b, 11c, operable to sense the temperature of each respective strip heater, thereby allowing the ECU to thermally manage the strip heaters and the base 4c of the container 4.

[0024] FIG. 5 is a plan view of the housing 3 and container 4 with the lid 5 removed to reveal a schematic view of the wiring harness of the water sensor means 6 electrically connected to the ECU 10 and secured to the inside base 4c of the container 4 below the condensate outlet hose 12 of the heat pump 1 shown in FIGS. 1 & 2. The electrodes 6a, 6b, are electrically insulated from each other but are otherwise exposed such that upon water being detected between them the previously open circuit is closed, thereby indicating to the ECU 10 the presence of water and the need for the commencement of an evaporation cycle.

[0025] FIG. 6 is a sectional side view of the container 4 and lid 5 into and through which has been received the condensate outlet hose 12 from the heat pump 1 shown in FIGS. 1 & 2. The outlet end 12a of the outlet hose 12 is below the level of the water sensor 6 such that the presence of water can only be detected when sufficient water has accumulated at the deep end of the container 4. However, because of the angled orientation of the base 4c of the container 4 only a relatively small volume of water, typically 0.1 L of water, need be collected in this region before the water level is high enough to be sensed by the sensor means 6. This can be contrasted to the amount of water necessary for safe operation of a corresponding prior art evaporator apparatus with a container having a flat base disposed generally horizontally, where the water is evenly distributed over a much wider area and in order to ensure safe operation which avoids hot-spots occurring and possible burnout of the heater means a much larger volume of water is required where, in practice, it has been found that a minimum volume of 0.5 L is required. Such a relatively large volume of water is not particularly problematic at temperatures above freezing but at or below freezing it can become problematic if the collected condensate water freezes and the condensate pipe from the heat pump becomes blocked. However, of more concern from an energy perspective is that an evaporator requiring the presence of such a volume of water before it is detected necessarily has to heat the water to at or near boiling point every time condensate is detected and an evaporation cycle is required, which is wasteful of energy.

[0026] In operation, once the presence of water has been detected by the water sensor means 6 the strip heaters 7a, 7b, 7c, are activated by the ECU 10 until they have reached a chosen temperature, preferably around 140° C., following which, each heater is pulsed on and off to maintain the chosen temperature. After the required amount of evaporation has been detected by the absence of water between the electrodes 6a, 6b, the strip heaters are left on for a suitable period, such as 30 minutes, to evaporate the relatively minor amount of condensate remaining in the container 4.

[0027] By recognising that conventional condensation evaporators have condensate collection containers of uniform height in the form of a horizontally flat base and upright sides there is always the need to heat a relatively large volume of water at the beginning of each evaporation cycle and that this problem can be solved by adopting the eloquently simple arrangement of the collection container having a shallow end and a deep end, this disadvantage can be avoided. As a consequence, a much smaller volume of water, requiring a correspondingly lower amount of power to heat it, is needed for the same purpose. Accordingly, the apparatus of the invention can be made sufficiently lightweight so as to permit convenient attachment to or adjacent a pre-installed heat pump due to the significantly smaller volume of water required before an evaporation cycle is triggered, being only about a fifth of the volume and hence weight of the minimum amount of water required as compared to the prior art evaporator apparatus previously described before an evaporation cycle commences. Similarly, as a consequence of the evaporator apparatus of the invention requiring a much reduced volume of water before triggering an evaporation cycle together with a reduced volume of condensate liquid being heated during the cycle as a consequence of the container having a shallow end the apparatus can be relatively lightweight, compact and unobtrusive when fitted to or forming part of a heat pump, as can be seen from FIGS. 1 and 2 while collectively removing the need for an unsightly condensate drainpipe to the ground.

Examples

Embodiment Construction

[0021]Referring firstly to FIGS. 1 and 2 a conventional air-source heat pump shown generally at 1 is mounted on and through an external wall surface of a building and includes therewithin an electrically operable fan for directing ambient air over the fins of a heat exchanger containing a working fluid convertible from liquid to gas and vice versa by means of a compressor for heating or cooling an enclosed space such as a room within the building, all in a known manner. Depending upon ambient temperature and humidity, this produces varying amounts of condensation which, in turn, produces condensate in the form of water or water droplets which, ordinarily, is either allowed to drip from the bottom of the heat pump to the ground or be collected and piped to a remote location, such as a drain in the ground or a condensate collection container. However, this is avoided by the placement of the evaporator apparatus 2 of the invention immediately below the heat pump 1 whereby to collect th...

Claims

1) Apparatus for evaporating water condensate produced by an air-source heat pump, the apparatus having a housing adapted, in use, to be positioned below the condensate drain of a heat pump, a condensate container within or forming part of the housing for collecting condensate, the container having a deep end and a shallow end, means for detecting when a minimum level of water is in the container and for sending signals indicative thereof to an electronic control unit (ECU), and electric heater means for heating, either directly or indirectly, the water to cause evaporation thereof in response to command signals from the ECU.2) Apparatus according to claim 1 wherein the container includes a lid, an inlet for receiving therethrough liquid condensate from the heat pump, and a vent for expelling evaporated condensate from the container.3) Apparatus according to claim 1 wherein the container has generally upright sidewalls, a lid and a generally flat base disposed at an angle to the horizontal to thereby define a cross-section of generally frusto-triangular shape.4) Apparatus according to claim 3 wherein the angle of the base is between about 10° and 15° and preferably about 12° from the horizontal.5) Apparatus according to claim 1 wherein the heater means comprises an array of electric strip heaters arranged in parallel relationship on the underside of the container whereby to permit the ECU to selectively activate and manage each heater.6) Apparatus according to claim 5 wherein the electric strip heaters are silicone strip heaters.7) Apparatus according to claim 5 wherein each strip heater includes means for sensing its own temperature and conveying signals indicative thereof to the ECU.8) Apparatus according to claim 7 wherein the temperature sensing means comprises a negative temperature coefficient thermistor (NTC).9) Apparatus according to claim 5 wherein the ECU is operable to independently activate each strip heater whereby to maintain a generally consistent temperature profile at the base of the container.10) Apparatus according to claim 9 wherein the consistent temperature profile of the base of the container is obtained via command signals from the ECU providing independently pulsed outputs to each strip heater.11) Apparatus according to claim 1 wherein the means for detecting when a sufficient level of condensate is in the container comprises a pair of electrodes disposed within the container, the electrodes being operatively connected to the ECU to thereby form an open circuit closable by the presence of condensate water whereby to activate the heater means and commence condensate evaporation.12) Apparatus for evaporating water condensate produced by an air-source heat pump of the type having a generally sealed base with a drain for removing liquid condensate, the apparatus having a housing adapted to be positioned below the condensate drain of the heat pump, a condensate container within or forming part of the housing for collecting condensate from the heat pump, the container having a deep end and a shallow end, means for detecting when a minimum level of water is in the container and for sending signals indicative thereof to an electronic control unit (ECU), and electric heater means for heating, either directly or indirectly, the water to cause evaporation thereof in response to command signals from the ECU.

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