EP2166291A2

EP2166291A2 - Heat pump

Info

Publication number: EP2166291A2
Application number: EP09252222A
Authority: EP
Inventors: Justin Smith; Joe Gasan; Peter Schwarz
Original assignee: Thermal Engineering Systems Ltd
Current assignee: Thermal Engineering Systems Ltd
Priority date: 2008-09-17
Filing date: 2009-09-17
Publication date: 2010-03-24
Also published as: GB0916344D0; EP2166291A3; GB2463574A; GB0817055D0

Abstract

A heat pump (10) for locating in a loft, the heat pump (10) comprising a housing (1) and a heat exchanger, the heat exchanger being located in the housing (1), wherein the housing (1) is narrower at the top than at the bottom.

Description

The field of this invention relates to heat pumps, in particular, but not necessarily exclusively, heat pumps for positioning in lofts.
Heat pumps are devices that extract heat from a relatively low temperature source and transfer the heat at a higher and more useful temperature to a heating system, e.g., a space heating system or hot water system. The transfer of heat is performed based on the compression and decompression of a refrigerant via a compressor, heat exchangers and an expansion valve. Hot air is drawn across one of the heat exchangers by a fan where the air is cooled, the heat being transferred into the system.
The amount of heat energy developed using a heat pump may be several times greater than the amount of electrical energy supplied to the process to operate the heat pump. This multiple is known as the Coefficient of Performance (COP). The higher the COP, the higher the efficiency, and the lower the operating costs and quantity of carbon dioxide generated for a given amount of heating. For these reasons, heat pumps are widely seen as being able to make a significant contribution towards reducing the production of greenhouse gases over other heating devices that directly use hydrocarbon fuel sources.
Heat pumps may be divided into two main classes: air source heat pumps (ASHPs), which extract heat from ambient, normally outside, air; and ground source heat pumps (GSHPs), which extract heat from the ground, either via water pumped up from a borehole, or by circulating a water and anti-freeze mixture in a closed-loop flexible pipe (often called a 'slinky') laid just under the soil where it extracts heat from the sun.
One significant problem with ASHPs is that, at the coldest time of the year, when the maximum heat output is required, the outside air temperature is at its lowest, and the ASHP delivers its poorest performance. However, in contrast to the air temperature, the temperature of ground source water drops only slightly, from around 12°C in the summer to minimum of 8°C in the winter, so a GSHP is typically more efficient than an ASHP at the coldest time of year. Nonetheless, against this must be weighed the much greater cost of GSHP installation, which requires either a borehole or a large ground area (typically the size of a tennis court) in which to bury the 'slinky'. Hence there is a trade off between the lower installation cost but higher running cost of an ASHP, and the opposite for a GSHP.
Although ASHPs are normally installed outside, in the early 1980s Thermal Engineering Systems Ltd produced and marketed an ASHP designed to be installed in an attic, known as the "All Seasons Loft Heat Pump". The advantage of locating the unit in the attic was that it allowed utilisation of the warmer air inside the roof space, brought about as a result of solar gain from the roof fabric, together with any heat losses from the dwelling below. The difference in temperature between ambient air and attic air can be significant (3 to 7°C averaged over a whole year), enabling the ASHP to operate much more efficiently than when installed outside.
Generally, the invention described herein is based on the loft heat pump principle, but delivers significant further efficiency and performance improvements. These improvements may enable ASHPs, for the first time, to compete with GSHPs in terms of efficiency and performance over the heating season, whilst maintaining the ASHP's significant cost advantage and installation simplicity.
According to a first aspect of the present invention, there is provided:

a heat pump located in a loft,
the heat pump comprising a housing and a heat exchanger,
wherein the heat exchanger is located in the housing, and
wherein the loft has a pitched roof and the heat pump is located proximate an apex in the pitched roof.

The heat pump may further comprise one or more compressors and/or expansion valves located in the housing.
In this application, the "apex" in the pitched roof is intended to mean an inside corner part of the roof provided by two relatively angled sections. The relatively angled sections may be two roof sections, or a roof section and a side wall of a building. The apex in the pitched roof may take a generally inverted v-shape and will commonly be at the top of the roof.
The top region of a loft, which is commonly proximate the apex of the pitched roof, is usually the hottest part of a loft. This is primarily as a result of hot air naturally rising. Furthermore, the whole surface of the pitched roof can act as a heat collector dependent on the orientation and position relative to the sun. Therefore, the apex of the pitched roof may be exposed to direct sunlight for longer periods, ensuring greater solar temperature gain at the top region of the loft. Accordingly, by positioning the heat pump proximate the apex of the pitched roof, at the top region of the loft, the heat pump may be surrounded by air of higher temperature than elsewhere in the loft, and therefore the performance and efficiency of the heat pump in transferring heat from ambient air to a heating and/or hot water system may be significantly improved. Accordingly, there may be a substantial reduction in the 'carbon footprint' of the system, and the running costs.
Preferably, the heat pump is disposed within a plenum chamber adjacent the apex of the pitched roof. The plenum chamber may act as a hot air trap.
Preferably, the heat pump housing is shaped to conform to the shape of the apex of the pitched roof. Accordingly, the heat pump may be positioned closer to the apex, and therefore closer to the top of the roof, than would otherwise be possible. To achieve this, the housing may be narrower at the top than at the bottom.
According to a second aspect of the present invention, there is provided:

a heat pump for locating in a loft,
the heat pump comprising a housing and a heat exchanger,
wherein the heat exchanger is located in the housing, and
wherein the housing is narrower at the top than at the bottom.

The heat pump may further comprise one or more compressors and/or expansion valves located in the housing.
By having a housing that is narrower at the top than at the bottom, the heat pump may be fitted closer to the apex in a pitched roof. This gives performance and heating advantages, as discussed above. In this application, references to the 'top' and 'bottom' of the housing are intended to mean the top and bottom of the housing when the heat pump is oriented for normal use.
Preferably, in the first or second aspects of the present invention, the housing has two end walls, and side walls connected between the end walls.
Preferably, first and second side walls lie along planes which are relatively angled to form an inverted V-shape, the first and second sidewalls being appropriate for positioning adjacent to, and substantially parallel to, respective relatively angled sections of the apex in the pitched roof. Preferably the arrangement is such that, in these positions, a third side wall will lie along a substantially horizontal plane at the bottom of the housing. In combination, preferably the planes along which the first, second a third side walls lie form a triangular shape. Preferably, the triangular shape is an isosceles triangle.
At its simplest, this arrangement may be achieved by providing the housing with only three sidewalls, i.e., the first, second and third sidewalls only, as described above. The sidewalls may form, in combination with the end walls, a triangular-prism shape. This triangular-prism shape may ensure a close fit with the apex in the pitched roof, whilst providing minimum obtrusion into the loft space.
However, the arrangement may alternatively be achieved with a housing having four or more sidewalls; i.e. the housing may have the three side walls discussed above, which lie along planes forming, in combination, a triangular shape, and additional side walls. In combination, the four or more sidewalls may take, for example, a trapezium-shape, a pentagonal-shaped cross-section, or a hexagonal shaped cross-section etc., between the end walls. Corners between the sidewalls may be rounded to provide for more comfortable handling and/or a more visually appealing look.
Preferably, one or more of the sidewalls has a respective opening for permitting air to enter the housing. Preferably, the opening is adjacent a portion of the heat exchanger. Preferably, the aforementioned first and second sidewalls each have a respective opening. Accordingly, air very close to the top of the loft may access the housing via the openings. Preferably, the heat exchanger is arranged to take an inverted v-shape to fit within the housing. This inverted v-shape may be achieved using a single heat exchanger or two or more heat exchangers angled relative to one another. The heat exchanger(s) may have two evaporation plates that are angled in substantially the same manner as the first and second sidewalls, so that they can locate adjacent openings located in the respective first and second sidewalls to ensure that warm air entering the openings will be immediately incident on them.
Preferably, the heat pump comprises at least one fan that is located in the housing, and a vent is provided in a sidewall or end wall through which air can be expelled from the housing using the fan, the expelled air having been cooled as a result of passing across the heat exchanger(s).
The vent may be located in the third sidewall at the bottom of the housing. By expelling the air through the vent, the fan will cause warm air to be drawn into the housing via the one or more openings discussed above. By expelling the cooled air (exhaust air) at the bottom of the housing, the cooled air is less likely to mix with the hotter air that enters the housing, which would otherwise reduce the efficiency of the heat pump. Alternatively, the vent may be located in an end wall or one of the first and second side walls. With this arrangement, (cool) waste air can be more easily ducted to the outside, thus not cooling the warm loft air. Thus, in some embodiments, the heat pump arrangement includes a duct extending from the vent that can be used to expel waste air outside of the loft.
In some embodiments two or more fans may be used. This can give greater control over the amount of air drawn by the heat pump (by switching on one or more of the fans), dependent for example of the temperature in the loft and/or the desired duty required from the unit.
When the heat pump is provided in a plenum chamber, e.g. by being located between the pitched roof and panelling, preferably a hole is provided in the plenum chamber, e.g. in the panelling, at a position adjacent the bottom of the heat pump housing, to permit exhaust air to pass into the main loft area below the plenum chamber.
One or both of the first and second sidewalls may abut the adjacent angled sections of the apex. However, preferably a gap is provided between one or both of the sidewalls and the adjacent sections to allow ambient air to enter the housing via the openings situated in the first and second sidewalls. To mount the housing proximate the apex of the roof, whilst leaving the gaps, the housing may be suspended from the roof, e.g., by a chain fixed between the roof and the housing.
Preferably the gap between the first and/or second sidewall and the adjacent roof section is less than 50 cm, more preferably less than 20 cm, and most preferably less than 10 cm. Preferably, the gap is greater than 3 cm. Preferably, the gap between the housing and the apex in the pitched roof is less than 50 cm, more preferably less than 20 cm, and most preferably less than 10 cm. Preferably, the gap is greater than 3 cm.
An embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 shows a top oblique view of a heat pump according to an embodiment of the present invention;
Fig. 2 shows a bottom oblique view of the heat pump of Fig. 1;
Fig. 3 shows the heat pump of Fig. 1 in position in a loft;
Fig. 4 shows a top oblique view of the heat pump of Fig. 1 with sidewalls removed;
Fig. 5 shows the heat pump of Fig. 1 in position in a loft;
Figs. 6a to 6e show alternative cross-sectional shapes for a heat pump according to the present invention;
Fig. 7 is a partly sectioned side view of heat pump according to a second embodiment of the invention that has two fans and a side discharge vent for waste air;
Fig. 8 is a plan view of a bottom section (containing the fans) of the heat pump of fig. 7; and
Fig. 9 illustrates an exemplary mounting of the heat pump of fig. 7 in a loft area, with a duct for expelling waste air outside the loft area.

A heat pump 10 according to an embodiment of the present invention is shown in Figs. 1 and 2. The heat pump comprises a housing 1 that includes first, second and third side walls 11, 12, 13 and front and rear end walls 14, 15. The side walls 11, 12 and 13, and end walls 14, 15 combine to give the housing a triangular-prism shape with a triangular cross-section between the front and rear end walls 14, 15, the corners of the triangle being rounded in this instance.
With reference to Fig. 3, the heat pump 10 is designed to be located in a loft with a pitched roof. The pitched roof 2 comprises two relatively angled roofing sections 22, 23, joined together at an apex 21. Since the first and second sidewalls 11, 12 are angled to a peak, the shape of the housing 10 generally conforms to the shape of the roof proximate the apex 21, and therefore the heat pump 10 can be fitted close to the apex 21.
By locating close to the apex 21 in the pitched roof, the heat pump 10 can be located in a top region of the loft, where the air in the loft is normally hottest. This improves the performance of the heat pump cycle, which is described further below.
As shown in Fig. 3, the heat pump is located within a plenum chamber 24. The plenum chamber is created between the apex of the roof 21 and a panel 25 fitted below the heat pump 10, and serves to trap hot air at the top region of the loft. A gap is provided between the bottom panel 25 and the roofing sections 21, 22 to permit rising air to enter the plenum chamber, in the directions indicated by the arrows 26.
Fig. 4 shows the heat pump 1 with the first and second sidewalls 11, 12 removed so that the heat exchanger of the heat pump 10 can be seen. The heat exchanger comprises two evaporators 31, 32 that comprise evaporator pipes 311, 321, a compressor 33, a condenser coil 34 and associated piping. The evaporators 31, 32 act as "heat collectors", transferring heat from ambient air drawn into the housing, as indicated by arrows 35, to liquid refrigerant fed through an expansion valve / evaporator pipes 311, 321, raising the temperature of the refrigerant, causing it to become a low temperature vapour. Subsequently, the vaporised refrigerant is fed into the compressor 33 where it is compressed, adding more heat energy to the vaporised refrigerant, raising its temperature considerably higher. This higher temperature vaporised refrigerant is passed via the condenser coil 34, where it condenses, transferring heat to water circulating in adjacent water pipes. The water enters the housing 1 via an inlet 36 located on the front end wall 14 of the housing 1, and exits the housing 1, once heated, via an outlet 37 also located on the front end wall 14 of the housing 1. The water is pumped through the heat pump using a circulation pump (not shown). The heated water exiting the housing 1 can be fed into a hot water system (not shown). The refrigerant is pumped around the piping using the compressor.
The housing is divided generally into two sections 18, 19. The rear section 18 includes the evaporators 31, 32 and the front section 19 includes the compressor 33, condenser coil 34 and the associated piping. The housing 1 is designed so that air is drawn into the housing only in the rear section 19, in order to transfer energy to the refrigerant in the evaporator pipes 311, 321.
The two evaporators 31, 32 each have a generally planar configuration and, the cross-section of the two evaporators 31, 32 in combination has a generally inverted v-shape. Accordingly, the two evaporators follow substantially the angle of the adjacent first and second side walls 11, 12 of the housing 1. Therefore, air entering the housing 1 via inlets 16 in each of the first and second side walls 11, 12 is immediately incident on the two evaporators 31, 32, improving the efficiency of the heat pump 10. Also, since the evaporators 31, 32 angle upwards, the incident air may be the hotter air, that has risen to the top region of the loft.
The air cools after transferring heat to the evaporator pipes 331, 332 and is expelled from the housing 1 via an outlet 17, as indicated by arrow 36 in Fig. 4. The outlet 17 is on the third side wall 13, which is at the bottom of the housing 1. A fan 38 is provided adjacent the outlet 17 to expel the cooled air through the outlet 17 and to cause hotter air to be drawn into the housing 1 via the inlets 16. With reference to Fig. 5, a circulation of air is created in the loft space 5. The movement of the air is represented by arrows 51; the wider the arrow, the hotter the air. As the air circulates, the air passes across the interior surface of the roof. When solar radiation acts (represented by arrows 52) on the exterior of the roof 22, 23, the temperature of the interior surface of the roof 22, 23 increases to a temperature higher than the air in the loft. Therefore, the air passing across the interior surface of the roof 22, 23 is warmed and continues to rise toward the apex 21 of the roof space where the heat pump is situated. The hotter air is drawn into the heat pump 10 and the cycle continues. The circulation is repeated on both sides of the loft space, but is shown on one side only in Fig. 5 for simplicity. This circulation and solar heating results in a considerable increase in performance over, for example, an arrangement where a rectangular heat pump is mounted on the floor of the loft.
So that the heat pump may fit close to the apex 21 of the roof, the housing 1 of the heat pump 10 may take a number of different cross-sectional shapes, in addition to the triangular shape, with rounded corners, discussed above. A non-exhaustive set of examples is shown in Figs. 6a to 6e. The cross-sectional shape may be a triangle with no rounded corners (Figs. 6a and 6b) that is an acute triangle 61 (Fig. 6b) that suits a steeply pitched roof or an obtuse triangle 62 (Fig. 6a) that suits a shallowly pitched roof. Alternatively, the cross-sectional shape may be 4-sided polygon 64 (Fig. 6d), 5-sided polygon 65 (Fig. 6d) or a 6-sided polygon 66 (Fig. 6e). All these shapes are narrower at the top than the bottom. Furthermore, the shapes each have three side walls which, in combination, form a triangular shape that conforms generally to the shape of an apex in a pitched roof.
Figs. 7 and 8 show a heat pump in accordance with a second embodiment of the invention. In this embodiment, there are two fans in the base on the unit that can be controlled independently of one another to expel (cool) waste air from the heat pump (and consequently to draw warm air from the loft space into the heat pump). By using one or other or both of the fans, the amount of air drawn into the heat pump can be controlled.
As best seen in fig. 8, the base of the heat pump housing, in which the fans are housed, is shaped to provide separate channels for waste air discharged from respective ones of the fans, these channels terminating at a shared discharge point at an end of the unit. As exemplified in fig. 9, air can be ducted from the discharge point through a duct to the outside, so as not to cool the warm loft air.
While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the scope of the invention.

Claims

A heat pump for locating in a loft,
the heat pump comprising a housing and a heat exchanger, the heat exchanger being located in the housing,
wherein the housing is narrower at the top than at the bottom.
The heat pump of claim 1, wherein the housing has first and second side walls which lie along planes which are relatively angled to form an inverted V-shape.
The heat pump of claim 2, wherein the housing comprises a third side wall that lies along a substantially horizontal plane at the bottom of the housing.
The heat pump according to claims 2 or 3, wherein the housing comprises first and second end walls, the side walls extending between the first and second end walls.
The heat pump according to claims 4, wherein the shape of the cross-section of the housing between the end walls is a polygon with three of more sides.
The heat pump of claims 4, wherein the shape of the cross-section of the housing between the end walls is a triangle.
The heat pump of claim 6, wherein the triangle is an isosceles triangle.
The heat pump of any one of claims to 2 to 7, wherein the heat exchanger comprises two evaporators which take an inverted v-shape within the housing, so that they lie substantially along the first and second side walls.
The heat pump of any one of the clams 2 to 7, wherein two heat exchangers are provided, each comprising an evaporator, which evaporators take an inverted v-shape within the housing, so that they lie substantially along the first and second side walls respectively.
The heat pump of any one of claims 2 to 9, wherein the heat pump comprises one or more fans that are located in the housing, and a vent is provided in a sidewall or an end wall through which air can be expelled from the housing using the fan.
The heat pump of any one of the preceding claims further comprising a compressor and condenser located in the housing.
A heat pump located in a loft,
the heat pump comprising a housing and a heat exchanger,
wherein the heat exchanger is located in the housing, and
wherein the loft has a pitched roof and the heat pump is located proximate an apex in the pitched roof.
The heat pump located in a loft of claim 12, wherein the heat pump is a heat pump according to any one of claims 1 to 11.
The heat pump of claim 12 or 13, wherein the hear pump is suspended from the roof.
The heat pump of claim 12, 13 or 14, wherein the heat pump is located in a plenum chamber.