GB2455125A

GB2455125A - Dehumidifier

Info

Publication number: GB2455125A
Application number: GB0723387A
Authority: GB
Inventors: Alistair Macfarlane
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-11-29
Filing date: 2007-11-29
Publication date: 2009-06-03
Also published as: GB0723387D0

Abstract

A dehumidifier for domestic use comprises one or more thermoelectric heat-pumping device (e.g. thermionic heat pump or Peltier devices) having a hot sink and a cold sink transferring heat there between, and air to be dehumidified being passed over the cold sink so as to lower its temperature below its dew point thereby allowing water inherent in the air to be removed. The cold sink may comprise of shaped fins that assist in the draining of condensed water, may comprise of a high thermal conductive aluminium with a hydrophobic coating or a graphite with high thermal conductivity and inherent hydrophobic properties. The dehumidifier may comprise an ionising brush whereby air prior to passing over the cold sink is removed of pollutants. One or more fans may draw air across the sinks. A pump may extract condensed water from a sump and is operable in response to a threshold water level being exceeded. The humidifier may operate in response to an output of a humidity detector and a temperature sensor proximate the cold sink may be used to control power to the heat pump(s).

Description

1 Iroved DehuRidifier 3 The present invention relates to an improved dehumidifier 4 for domestic use, and in particular a dehumidifier which achieves improved moisture removal and efficiency.

7 Dehumidification in the home has thus far mostly been 8 achieved via relatively large, heavy and cumbersome 9 devices based on refrigeration compressor technology.

Such devices are also noisy and expensive to run, so the *,**1 advantages of dehumidification are not being fully :...12 realized. Mould growth, dust mites and other pathogens S...

13 such as MRSA and C. Difficile all benefit from high *:*.4 humidity levels. Recent Swedish research has shown that *:i lowering the humidity also means that there can be much 16 fewer air changes in a dwelling house than usually :7 required, resulting in a major saving in energy, and that : f8 lower room temperatures are found to be more comfortable 19 when the humidity is lowered. It should also be noted that the present climate change is causing generally 21 higher levels of humidity in the more northern (and 22 southern) latitudes.

1 British Patent no. GB2386569B granted to A. A. Macfarlane 2 showed that a dehumidifier using solid state cooling 3 devices such as Peltier modules could form the basis of a 4 small room dehumidifier for homes with a permanent or temporary dampness problem. Such a design was able to 6 remove a reasonable amount of moisture from the air, 7 however it is desirable to improved on the levels of 8 moisture removal and efficiency achievable.

It is therefore an object of the present invention to 11 provide a dehumidifier which achieves improved moisture 12 removal and efficiency.

14 According to a first aspect of the present invention, there is provided an improved dehumidifier for domestic 16 use, the dehumidifier comprising: 17 one or more dehumidifier modules; 18 each of the one or more modules comprise a heatsink, 19 heatpump and cold sink; wherein the heatpuznp is arranged to transfer heat from the coidsink to the heatsink. 22

23 Preferably, the dehumidifier comprises a plurality of *.4 modules configured in an array.

**26 Preferably, the coidsink provides a preferred surface for :::27 condensation of airborne water.

29 Preferably, provision of the preferred surface for condensation acts to reduce humidity of air passing over 31 the coidsink.

1 Preferably, the coidsink comprises shaped fins to assist 2 in the draining of condensed water.

4 Preferably, the coidsink comprises a material of high thermal conductivity.

7 Optionally, the coidsink comprises a hydrophobic coating.

9 The coidsink may comprise a material such as high thermal conductivity aluminium which may have a hydrophobic 11 coating, or a graphite material having high thermal 12 conductivity and inherent hydrophobic qualities.

14 Preferably, the dehumidifier further comprises an ionising means adapted to ionise the air passing over the 16 coldsink.

18 Optionally, each of the one or more modules comprises the 19 ionising means.

21 Optionally, the ionising means is adapted to attract dust "22 particles or kill airborne organisms, and precipitate I...

23 said onto the coldsink. S. *

*. *.;4 5:25 Preferably, the dehumidifier comprises one or more fans 26 adapted to draw air into the dehumidifier. S. S.

: 28 Preferably, the one or more fans are arranged so as to 29 draw air across or through the ionising means prior to passing the coidsink.

1 Preferably, the one or more fans are arranged so as to 2 draw air across the heatsinks after passing the coidsink, 3 so as to cool the heatsinks.

Preferably, the dehumidifier comprises an air inlet and 6 an air outlet, the air outlet distal from the air inlet 7 so that air exiting the dehumidifier is not recirculated.

9 Preferably, the dehumidifier comprises an ionising brush located proximal to the air inlet.

12 Preferably, the ionising brush acts so as to at least 13 cause pollutants such as dust particles, mould spores, 14 dust mites, viruses, bacteria and the like to be attracted to the coidsinks, and further preferably in the 16 case of dust mites, viruses and bacteria to kill or 17 destroy said pollutants.

19 Preferably, the heatpump comprises one or more Peltier coolers. * * * * * **

*.22 Most preferably, the one or more Peltier coolers are S...

23 operated at a current less than a rated current of the same.

26 Alternatively, the heatpump comprises one or more devices :27 selected from the group of Peltier coolers, thermionic * 28 heatpumps, thermal chips or thermoelectric heat pumps.

Optionally, the dehumidifier comprises a high frequency 31 switching power supply which provides power to the one or 32 more heatpunips.

1 Preferably, the power supply comprises power factor 2 correction and/or synchronous rectification.

4 Preferably, the dehumidifier comprises an ionising device power supply which provides a high power voltage to the 6 ionising device.

8 Preferably, the ionising device power supply comprises a 9 quasi-resonant switching regulator so as to prevent radio frequency interference.

12 Preferably, the dehumidifier further comprises a pump 13 adapted to extract condensed water from the dehumidifier.

Optionally, the pump is operable in response to a water 16 level in a sump of the dehumidifier exceeding a 17 predetermined threshold.

19 Optionally, the dehumidifier comprises a user interface configured to allow a user to control operation of the * .21 dehumidifier. * * . * *.

* .. 22 *...

23 Preferably, the user interface comprises touch sensitive *:* controls. * .

**6 Preferably, the dehumidifier further comprises a humidity 2 detector.

29 Optionally, the dehumidifier is operable in response to an output of the humidity detector.

1 Preferably, the dehumidifier further comprises a 2 temperature sensor. Optionally, the temperature sensor 3 is located proximal to the coidsinks.

Optionally, the power supply to the heatpumps is 6 determined by an output of the temperature sensor.

8 The present invention will now be described by way of 9 example only and with reference to the accompanying figures in which: 12 Figure 1 illustrates in schematic form a 13 dehumidifier module in accordance with the present 14 invention; 16 Figure 2 illustrates in schematic form an array of 17 dehumidifier modules in accordance with the present 18 invention; Figure 3 illustrates a schematic cross section of the array of dehumidifier modules illustrated in Figure 2; and S...

Figure 4 illustrates a block diagram of a dehumidifier in accordance with an aspect of the present invention.

:: : : : 28 Fig 1 shows a basic module comprising heatsink, cold sink 29 and heatpump. Examples of specific heatpumps which may be utilised are discussed below. Such a coidsink requires 31 shaped and tapered pins to allow condensed water to drain 32 of as quickly as possible, and may be constructed of high 33 thermal conductivity aluminium, often requiring a 1 hydrophobic coating, or preferably a graphite material 2 which has extremely high thermal conductivity and is 3 super-hydrophobic, allowing water to drain off even more 4 speedily. The use of graphite also markedly reduces the weight of the entire device, which is an advantage where 6 one application would be for a wall-hung situation.

8 Fig. 2 shows an array of these modules, and fig 3 shows a 9 cross-sectional view of this array incorporated into an airflow arrangement such that the ambient moist air is 11 sucked in at the base of the unit due to negative 12 pressure caused by the exhaust fan or fans, and travels 13 first through an air negative ioniser brush, then across 14 the cold surfaces of the cold sinks where the moisture is condensed out. This air, which has been cooled slightly, 16 is then used to exhaust across the heatsinks and thus 17 cool them more effectively and efficiently than using 18 ambient air. The exhaust air, which is drier and has 19 gained heat both from the latent heat of condensation of the moisture contained in it and the inefficiency of the ****l heatpumps themselves, plus some losses associated with * S. 22 the electronics, is blown out of the unit with a fan or ***.

23 fans in the opposite direction away from the air inlet at ** . 4 the base, so that it is not recirculated.

5.5. 45 * S 26 The addition of an ioniser brush in the inlet airflow has 0S** * S a number of advantages. lonising the air passing through S. 2 it negatively causes the molecules of water vapour to be 29 attracted to the surfaces of the cold sink, which is charged positively. However it also has a similar effect 31 on particles contained in the inlet air, such as dust, 32 mould spores, dust mites, viruses, and bacteria. In fact 33 recent research has shown that organisms such as the 1 latter three which are subject to high voltage ionisation 2 have their cell walls disrupted causing the death of the 3 cell. These particles are attracted to the positively 4 charged cold surfaces and washed off into the drain by the condensing water.

7 So the ioniser both helps to clean the air and remove the 8 dust and pathogens from it. The negative air ions not 9 removed from the airflow are released into the surroundings via the exhaust air, where they provide a 11 known beneficial effect improving both mood and 12 alertness. It has also been shown recently that by 13 keeping humidity levels under control, neither mould, 14 dust mites or pathogens such as MRSA grow or multiply, so that both the dehumidifying action and ioniser action act 16 synergistically to clean the air in a room employing this 17 type of device. Reducing or halting the mould growth by 18 removing spores and keeping the humidity at a level where 19 they cannot grow has been shown to have beneficial effects on health, as some moulds are toxic or *."21 carcinogenic. Reducing or removing dust mites is known to * ** **42 markedly reduce the incidence of asthma. Reducing or 23 removing other pathogens speaks for itself, especially in S. S . 4 an application such as hospital wards.

S

26 The supply required to power the heatpumps, no matter S... * S

27 what type, is low voltage, and relatively high current. * .. * S S

* 28 To obtain this efficiently from a standard AC mains 29 outlet (llO/230vac) requires a small switched-mode supply. The entire circuit is shown in block diagram form 31 in Fig. 4. The method of construction of the individual 32 blocks will be well known to those skilled in the art.

33 The mains supply is connected to Live, Neutral and earth 1 and passes through an Electromagnetic Interference Filter 2 (limiting the amount of interference coupled to the line 3 to meet local regulations) to a full wave rectifier.

In order to meet current legislation, following that 6 rectifier the power supply has a high frequency boost 7 converter pre-regulator which is controlled to draw a 8 sinusoidal current from the line (power factor control) 9 and stores energy in the following smoothing capacitor.

Supplied by this is a flyback converter, also running at 11 high frequency, which drops the voltage from the high 12 voltage supplied by the pre-regulator to the low voltage, 13 high current required for the heatpumps. Due to this 14 relatively high current required, rectification of the output of the flyback transformer is by a synchronously 16 switched low resistance mosfet, which avoids the inherent 17 losses attributable to the forward drop of a conventional 18 rectifier diode at high current. A second capacitor 19 smoothing stage is provided to remove the high frequency ripple from the output voltage An auxiliary transformer * 1 winding is also provided to supply the fan or fans as * * * ** *...22 required. **1* ** *

* The high-voltage generator for the ioniser is also a small switching supply, this time a quasi-resonant 26 circuit which efficiently creates a sine wave in the * S 27 Kilohertz region, which is stepped up by a small I. S. * S S * *28 transformer and rectified to give around -5000 volts DC 29 to be applied to the brush. The large number of sharp points in the brush generates a large flow of ions from 31 their tips. A sine wave supply is used here to minimise 32 the potential for high voltage, high frequency edges 1 causing ringing and RF interference on the ioniser brush, 2 which could then act as an aerial.

4 A humidity detector circuit is included in the design, so that at chosen levels of humidity the device can 6 automatically switch off to save energy. Those levels are 7 chosen using touch sensitive switch pads safely on the 8 outside of the plastic casing which operate capacitively 9 through the plastic; likewise switching on and off is accomplished by another touch sensitive pad. Conventional 11 switches might be used in this application but as these 12 are mechanical device with moving parts may suffer from 13 limited life. A thermostat adjacent to the coidsinks 14 switches off the supplies to the heatpumps if the ambient temperature of the air leaving the coidsinks is close to 16 freezing point, to avoid the build-up of ice on the 17 coidsinks at very low ambient temperatures. In the touch 18 sensing block, non-volatile integrated circuits store the 19 set conditions so that in the event of mains failure the device will continue working in its chosen mode after 1 such an outage. Indicator Light emitting diodes provide * S. user feedback to indicate set humidity levels and 23 operating conditions.

A secondary very high efficiency direct off line supply 26 is provided to supply the low level of power required to :7 maintain the control and sensing electronics when the * �18 main power supply is switched of f, either by the user or 29 by achieving the desired humidity level.

31 A third auxiliary winding on the flyback transformer core 32 provides a safe low voltage power supply isolated from 33 the rest of the circuitry and connected to ground 1 potential, to power an optional pump in the sump of the 2 device. This pump may be used to force out the collected 3 water in the sump, should direct gravity fed drainage not 4 be possible. It could be needed should the device be situated in a basement, for example, or where the 6 discharge had to be at a higher level.

8 The water level in the sump is sensed by a capacitive 9 method. Two plates are held in a fixed position in two slots in the sump such that a capacitance Cs exists 11 between them, and should the water level rise to a preset 12 level, either through the receiver bottle being full, a 13 failure of the natural drainage (e.g. blocked pipe, full 14 bottle, etc) or where pump is needed, the capacitance between the plates increases due to the increased 16 dielectric constant of the water, and is detected, the 17 unit is switched off and the pump enabled for a set 18 period. During this period an indicator Light emitting 19 diode is caused to flash.

* .21 In summary, the use of very small but relatively * . * * *.

2 inefficient Peltier modules as the heat pumps to cool the * . cold moisture condensing surfaces has been improved by reducing their running current from their nominal value. * *.

*..?. It was realised that whilst the heat pumping capability 26 reduces linearly with the current passing through the I...

2.1 device, the losses in the Peltier due to this current *e *.

: 28' reduce by the square of the current. In this way, a 29 Peltier module running at one third of the rated current would have losses of one ninth of those at rated current.

31 However this reduced heat pumping capability can be 32 offset by using a number of Peltier modules to achieve 33 the same amount of condensation.

2 The difficulty of using one or a few high powered Peltier 3 modules with a single heat sink and cold sink as in the 4 previously mentioned British Patent, is related to the ability to dissipate the relatively concentrated heat 6 losses in such a way as to keep the hot side of the 7 Peltier module(s) cool, and therefore the cold surfaces 8 at the minimum temperature required to condense out the 9 airborne moisture. By using an array of smaller modules running at lower currents (and therefore higher 11 efficiency), each connecting to its own cold sink and 12 heatsink, it is possible to reduce the concentration of 13 heat and improve the efficiency of the Peltier modules 14 and the overall dehumidifier. Also, such an array of modules comprising heatpump, heatsink and cold sink is 16 scaleable, in that for small rooms such as a toilet a few 17 modules might suffice, whereas large rooms or rooms with 18 a more pervasive damp problem may require a larger number 19 of modules. In addition to this, new types of heatpurnps such as nano crystalline Peltiers, quantum 21 thermotunneling devices known as Coolchips, Eneco Thermal * ** * * * ?2 Chips and Thermoelectric heatpumps (such as eTEC produced **** *2' by Nextreme) are becoming available which enhance the overall efficiency by a factor of several times. However the basic modular construction can still beneficially be *S**** * 26 used with these devices, with only minimal changes to the **** **7' electronics supplying the current to them. ** A. * **

29 Further modifications and improvements may be added without departing from the scope of the invention herein 31 described.

Claims

Claims 1. A improved dehumidifier for domestic use, the dehumidifier comprising: one or more dehumidifier modules; each of the one or more modules comprise a heatsink, heatpump and coldsink; wherein the heatpump is arranged to transfer heat from the coidsink to the heatsink.
2. A dehumidifier as claimed in claim 1, wherein the dehumidifier comprises a plurality of modules configured in an array.
3. A dehumidifier as claimed in claim 1, wherein the coidsink provides a preferred surface for condensation of airborne water.
4. A dehumidifier as claimed in claim 1, wherein provision of the preferred surface for condensation acts to reduce humidity of air passing over the cold sink.
5. A dehumidifier as claimed in claim I, wherein the coldsink comprises shaped fins to assist in the draining of condensed water.
6. A dehumidifier as claimed in claim I, wherein the coldsink comprises a material of high thermal conductivity.
7. A dehumidifier as claimed in claim 1, wherein the coldsink comprises high thermal 00 conductivity aluminium with a hydrophobic coating or a graphite material with high (\J thermal conductivity and inherent hydrophobic qualities.
8. A dehumidifier as claimed in claim 1, wherein the dehumidifier further comprises an ionising means adapted to ionise the air passing over the coldsink to kill airborne organisms and precipitate said onto the coldsink.
9. A dehumidifier as claimed in claim 1, wherein one or more fans are adapted to draw air into the dehumidifier.
10. A dehumidifier as claimed in claim 1, wherein the one or more fans are arranged to draw air across or though the ionising means prior to passing through the coldsink.
11. A dehumidifier as claimed in claim 1, wherein the one or more fans are arranged so as to draw cooled air across the heatsinks after passing the coldsink, so as to cool the heatsinks.
12. A dehumidifier as claimed in claim 1, wherein the dehumidifier comprises an air inlet and an air outlet, the air outlet distal from the air inlet so that the air exiting the dehumidifier is not recirculated.
13. A dehumidifier as claimed in claim I, wherein the dehumidifier comprises an ionising brush located proximal to the air inlet.
14. A dehumidifier as claimed in claim 1, wherein the ionising brush acts so as to at least cause pollutants such as dust particles, mould spores, dust mites, viruses, bacteria and the like to be attracted to the coidsinks, and further preferably in the case of dust mites, viruses and bacteria to kill or destroy such pollutants.
15. A dehumidifier as claimed in claim 1, wherein the heatpump comprises one or more Peltier coolers.
16. A dehumidifier as claimed in claim 1, wherein the one or more Peltier coolers are operated at a current less than a rated current of the same.
17. A dehumidifier as claimed in claim 1, wherein the heatpump comprises one or more devices selected from the group of Peltier coolers, thermionic heatpumps, thermal chips or thermoelectric heatpumps.
18. A dehumidifier as claimed in claim 1, wherein the dehumidifier comprises a high frequency switching power supply which provides power to the one or more heatpumps.
19. A dehumidifier as claimed in claim 1, wherein the power supply comprises power factor correction and or synchronous rectification.

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20. A dehumidifier as claimed in claim 1, wherein the dehumidifier comprises an ionisng device power supply which provides a high voltage to the ionising device.
21. A dehumidifier as claimed in claim 1, wherein the ionising device power supply comprises a quasi-resonant switching regulator so as to prevent radio frequency interference.
22. A dehumidifier as claimed in claim 1, wherein the dehumidifier further comprises a pump adapted to extract condensed water from the dehumidifier.
23. A dehumidifier as claimed in claim 1, wherein the pump is operable in response to a water level in a sump of the dehumidifier exceeding a predetermined threshold.
24. A dehumidifier as claimed in claim 1, wherein the dehumidifier comprises a user interface configured to allow a user to control operation of the dehumdifier.
25. A dehumidifier as claimed in claim 1, wherein the user interface comprises touch sensitive controls.
26. A dehumidifier as claimed in claim 1, wherein the dehumidifer further comprises a humidity detector.
27. A dehumidifier as claimed in claim 1, wherein the dehumidifier is operable in response to an output of the humidity detector.
28. A dehumidifier as claimed in claim I, wherein the dehumidifier further comprises a temperature sensor located proximal to the coidsink.
29. A dehumidifier as claimed in claim 1, wherein the power supply to the heatpumps is determined by an output of the temperature sensor. c'J