WO1999042764A1

WO1999042764A1 - Air humidifier

Info

Publication number: WO1999042764A1
Application number: PCT/SE1999/000218
Authority: WO
Inventors: Gunnar LÖFQVIST
Original assignee: KB BIOTOPEN
Current assignee: KB BIOTOPEN
Priority date: 1998-02-20
Filing date: 1999-02-18
Publication date: 1999-08-26
Anticipated expiration: 2000-08-20
Also published as: NO20004034L; SE9800537D0; NO20004034D0; DE69921969D1; SE9800537L; ATE282799T1; CA2321251A1; EP1056977B1; EP1056977A1

Abstract

The invention relates to a humidifier for conditioning ambient air, comprising a liquid reservoir (10) with an upward facing opening (11). Also, the humidifier comprises a body (12) which is arranged above the reservoir (10) and is made of a capillary material and a shaft (13) extending through the opening (11) into the reservoir. The body (12) and the shaft (13) is manufactured from a single piece of a mineral material.

Description

TITLE

Air humidifier

FIELD OF THE INVENTION

The present invention relates to an air humidifier for conditioning ambient air, comprising a liquid reservoir with an upward facing opening, a body which is arranged above the reservoir and is made of a capillary material and a shaft extending through the opening into the reservoir.

BACKGROUND OF THE INVENTION

It is known in the field that the humidity of the air is an important factor which influences our experience of the indoor climate. Especially during the winter season, the indoor climate is influenced because the air that is used for ventilation exhibits a lower humidity of the air than during the summer season. That is the reason that the indoor air may become very dry, for example in office rooms. These rooms are normally ventilated by exchanging the room air for outdoor air at an average frequency of about one renewal per hour.

A number of devices are known which enable humidifying the indoor air. Some of these devices function as electric driven steam generators that are expensive, energy consuming, noisy as well as require frequent cleaning. Other more simple devices function by natural evaporation, without a supply of electric energy. Generally, these devices have a low degree of efficiency, which involves that they are not cost efficient. In many cases organic material is used as a wick, for drawing up water from a water reservoir in the humidifier, wherein there is a great risk for growth of micro-organisms, mould and bacteria in said material.

TECHNICAL PROBLEM One object of the present invention is therefore to provide a simple and efficient device for solving the above described problems .

THE SOLUTION For this object, the humidifier according to the invention is characterized in that the body and the shaft is manufactured from a single piece of a mineral material.

According to one preferable embodiment of the invention, the body is substantially spherical. Also, the shaft is preferably substantially cylindrical.

The diameter of the shaft is preferably about a third of the diameter of the body. The mineral material may for example be sandstone.

The reservoir is preferably provided with a closing lid with an via hole which closes against the shaft. The lid may be provided with a closable filling opening.

According to still another preferable form of execution of the invention, the edge of the liquid reservoir opening constitutes a support for the capillary material body. A closable filling opening is preferably located adjacent the edge of the liquid reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will in the following be further described in a non- limiting way with reference to the accompanying drawings in which: Fig. 1 is a partly sectioned side view of a humidifier according to a first embodiment of the invention, and Fig. 2 is a corresponding side view of a second embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

The humidifier shown in Fig. 1 comprises a liquid reservoir 10 with upward facing opening 11. The opening is provided with a closing lid 14 with a closable filling opening 15. The lid 14 is provided with a via hole which closes against a cylindrical shaft 13, which is manufactured from a single piece with a spherical body 12, in such a way that it is rotation symmetric.

When the humidifier is set up for use, the body 12 is located directly above the shaft 13, which extends down into the liquid in the reservoir. The body is manufactured with its shaft of a mineral material, e.g. sandstone, which is available from Slite on Gotland. This sandstone has an air content of about 20%, which means that water may be drawn up by capillary suction via the shaft and be distributed in the body 12, so that it becomes damp. It has turned out to be advantageous when the diameter of the shaft is about a third of the diameter of the body, in order to get sufficient capillary transport capacity to maintain a moist sandstone surface. That is to say that there should be practically free water on the surface of the sandstone. This results in that the capillary transported moisture may be delivered to the ambient air according to the principle of evaporation from a substantially free liquid surface. Theoretical description

The climatic conditions which are generally stated as essential for our experience of indoor climate is the temperature, the movement of the air as well as the humidity of the air. One way of presenting the connection between a suitable temperature and a relative humidity is to state a delimited area in the so called Mollier diagram. The Manual Bygg, chapter HOI, 1982, refers to the comfort diagram according to Ashrae Comfort Standard 55 - 74. There, an area for relative humidity is stipulated which should lie in the interval of 20 - 60 %.

In a room having a normal change of room air and without extra supply of humidity, the relative humidity will be: v

RF = —^£— , ,) v_e = RF_e*v_s(T_e)

v_e content of vapour in outdoor air kg/m³

RF_[ relative humidity in indoor air

RF_e relative humidity in outdoor air v_s(T) saturation density in air at the temperature T degrees Celsius kg/m

T_e temperature in outdoor air in degrees Celsius

T_ temperature in indoor air in degrees Celsius

The following terms have been used for calculating evaporation from a free liquid surface: g = β*(v_s(T_w) -φ*v₅(O) g delivered humidity kg/ (m *s)

T_w surface temperature °Celsius Tj ambient temperature °Celsius β calculated according to Lewis' formula β = a_cv l(p*Q α„ convection heat transition coefficient W/ (m²*K) p air density kg/m³ 1.20 kg/m³ C specific heat for air 1000 W/ (kg*K) φ relative humidity in the surrounding air v_s(T) saturation density in air at the temperature T degrees Celsius kg/m³

From this equation it is clear that emitted moisture increases with β which in its turn grows with a_cv . Dry air in the environment also increases g .

One problem with the equation is that T_w is a part of the expression of g . However, an energy balance equation may be formulated. It is assumed that the energy efficiency only occurs between ambient air and moist surface.

g*K = (a_cy + _r .)*(?; - - T )

τ_w = _τ s*K - Ii _cy + o

« -- = c*|τ - r_w| 0.25

a_r = ^5.78*10-⁸*(7; + Z)* T_W + h_c heat of evaporation 2.3*10⁶ J/kg

C coefficient about 2 ε emission number about 0.85

The equations result in the following: Energy is needed for allowing the moisture to evaporate, and energy is taken from the ambient air. The ambient temperature T_ must be higher than the temperature T_w of the surface for enabling energy to be transferred from the air to the surface.

The table below show how evaporation from a moist surface is generally affected by the relative humidity in the ambient air, wherein: g delivered vapour from a moist surface in gram per m and hour

RF relative humidity in the environment

T_w surface temperature, water temperature

T_± room temperature

T_± °C RF % T °C g gram/m hour

21.0 0.0 12.3 112.0

21.0 10.0 13.3 97.4

21.0 20.0 14.4 83.6

21.0 30.0 15.3 70.4

21.0 40.0 16.3 57.8

21.0 50.0 17.2 45.9

21.0 60.0 18.1 34.8

21.0 70.0 18.9 24.4

21.0 80.0 19.7 14.8

21.0 90.0 20.4 7.0

21.0 100.0 21.0 0.0

Thus, for example is true for RF_t = 20% that there would ideally be about 83,6 gram water vapour per m of moist delivering surface each hour. It has been demonstrated by laboratory experiment that the humidifier designed according to the invention is maintained moist by capillary supply of liquid. Thus, during this process, the surface of the sandstone becomes moist and water in vapour phase is delivered to the ambient air, so that this air thereby will be humidified. Analysis have been performed by means of measurements of relative humidity and temperature in a test room. Furthermore, relative humidity and temperature has been measured outside this test room. Delivered average amount of dampness has been measured by weighing. Calibrated thermohygrographs, thermometers and capacitive transducers have been used during the measurements.

The experiments have shown the following:

• The difference in relative humidity in different test rooms, with respectively without the humidifier according to the invention, has by measurements proven to be 4 to 10 percentage points depending on amount of ventilation and the size of the moisture emitting surface.

• A higher relative humidity has been measured in the close vicinity of the invention than the average value in the room.

Reasonably, this may be interpreted as the forming of a local climate in the vicinity of the humidifier according to the invention.

• The emission of moisture increases with increasing dryness in the air.

• In doing so, the emission of moisture closely coincides with the theoretical calculations.

Thus, it has been shown that the above described humidifier operates efficiently without the inconveniences mentioned in the 8

introductory part. Because the driving power for humidifying, i.e. thermal energy, is derived from the surroundings, a physical effect is obtained on said surroundings. As a result of this, an automatic mixing of the air is provided m a closed room, if the humidifier according to the invention is placed inside this room.

The humidifier shown in Fig. 2 comprises an in the direction upwards slightly tapering liquid reservoir 10, which forms a support for the spherical body 12 by means of the edge of its opening 14. Consequently, this embodiment of the invention does not need any closing lid. A filling opening 15 is arranged in the side of the reservoir, and this opening is closable by means of a stopper 16.

The invention is not limited to the above described embodiment, but several variants are conceivable within the scope of the accompanying claims. For example, the shape of the shaft 13 and the body 12 may be varied within scope of the invention. Other materials than sandstone are possible. Also, the reservoir 10 may be designed differently.

Claims

1. An air humidifier for conditioning ambient air, comprising a liquid reservoir (10) with an upward facing opening (11) , a body (12) which is arranged above the reservoir (10) and is made of a capillary material and a shaft (13) extending through the opening (11) into the reservoir, c h a r a c t e r i z e d in that the body (12) and the shaft (13) is manufactured from a single piece of a mineral material .

2. Air humidifier according to claim 1, c h a r a c t e r i z e d in that the body (12) is substantially spherical .

3. Air humidifier according to claim 1 or 2 , c h a r a c t e r i z e d in that the shaft (13) is substantially cylindrical .

4. Air humidifier according to claim 3, c h a r a c t e r i z e d m that the diameter of the shaft (13) is about a third of the diameter of the body (12) .

5. Air humidifier according to any one of claims 1-4, c h a r a c t e r i z e d in that the mineral material is sandstone.

6. Air humidifier according to any one of claims 1-5, c h a r a c t e r i z e d m that the reservoir (10) is provided with a closing lid (14) with an via hole which closes against the shaft (13) . 10

7. Air humidifier according to claim 6, c h a r a c t e r i z e d in that the lid (14) is provided with a closable filling opening (15) .

8. Air humidifier according to any one of claims 1 to 5, c h a r a c t e r i z e d in that the edge of the liquid reservoir (10) opening (14) constitutes a support for the body (12) .

9. Air humidifier according to claim 8, c h a r a c t e r i z e d in that a closable filling opening (15) is located at the edge of the liquid reservoir.