GB2539939A

GB2539939A - Drying method

Info

Publication number: GB2539939A
Application number: GB1511564.5A
Authority: GB
Inventors: Jane Moulding Vanessa; Andrew Coombs Michael; Wilhelmus Van Uum Paulus; George Gilbert David
Original assignee: AGV TECHNOLOGY Ltd; Agv Tech Ltd
Current assignee: AGV TECHNOLOGY Ltd; Agv Tech Ltd
Priority date: 2015-07-01
Filing date: 2015-07-01
Publication date: 2017-01-04
Also published as: GB201511564D0

Abstract

A diffuse infrared source having a wavelength of between 3 and 15 microns, used to advance the drying times of damp construction and decorating materials such as cement, render, plaster, concrete, grouting, and paint. This reduces drying times whilst avoiding damage or degredation to the material. It can be used to dry newly applied materials, or materials that have become wet through flood damage or similar. The material to be dried receives the IR over a period of at least 3 hours, and is maintained at a temperature that is no more than 35°C. The device is positioned at between 1.5 and 3.5m from the damp material. The device is a heated plate of 0.25-1.75m2 powered by an electrical or other power source. The drying effect can be augmented by the use of ventilation. The device may be waterproof and may be thermostatically controlled. The device can monitor the humidity of the material to be dried.

Description

DRYING METHOD

The present invention relates to a method for evenly drying materials over relatively long periods of time (e.g. more than 3hrs). It is especially useful for drying out buildings or parts thereof which have become wet during construction, during renovations, or because of flooding or other damp issues. The method can be applied to other materials prepared using water or other solvents or fluids.

Drying of construction material is a well-known requirement in the building trade. For example, materials such as plaster, cement and concrete are frequently left to dry naturally over several days in order to preserve their long-term aesthetic appearance or structural integrity. However there is increasingly a need to dry these materials quicker in order to meet to tight schedules or reduce costs. Similarly in a flood situation the need to quickly dry and repair a building to get it back to its normal use is also highly desirable. This has led to a number of options to advance these drying processes including the use of heaters, fans and dehumidifiers all of which are generally available in the market. Various patents have also taught how combinations of heating a limited area and flushing air can improve drying times; e.g. 'Method and apparatus for extracting moisture and/or mould from a structure of a building' WO1998045653. However there are issues with the use of conventional heaters; for example those using liquid petroleum gas (LPG) as a fuel, as they can produce hot spots and result in feathering and cracking of plaster or damage in other materials. Generally heating up large spaces especially on building sites under construction can also be expensive. Dehumidifiers are successful in reducing drying times and are widely used by the construction industry however drying times can still be long. Our invention can be used by itself or complimentary to several existing techniques already used to decrease drying times.

Contrary to industry-wide practice our invention uses a low-power diffuse infrared (IR) source to improve drying times. We have found that application of diffuse IR radiation can under certain low-level conditions and over more than 3 hours or more reduce drying times while avoiding any damage or degradation to the material e.g. feathering or cracking in plaster work. In our method, low levels of temperature increase are achieved in the surface of the material, wall or structure. This is different to several other heating methods that employ concentrated IR or higher intensity sources or sources placed close to the surfaces being dried. In our method the temperature increase is spread more evenly across the total surface being dried. In our invention absolute surface temperature is also limited. These features make the process very efficient in terms of energy usage.

Thus, according to a first aspect of our invention, there is provided the use of at least one man-made diffuse IR source having a wavelength envelope substantially in the range 3-15 microns to advance the drying times of damp materials characterised in that a total equivalent power per unit of surface area of material to be dried of from greater than 50 W/m^ to 500W/m^ is applied over a period of at least 3 hours under conditions such that (1) the surface temperature of the material being dried does not increase by more than 25°C over ambient, (2) the actual temperature of the material does not exceed 35°C and (3) the diffuse IR source operates between 0.25-5kW and is positioned at between 1.5m to 3.5m from the material to be dried

By the term 'man-made diffuse IR source' is meant a non-naturally-occurring source of IR radiation which allows a diffuse blanket of radiation to be spread more evenly across the wall, structure or material it is drying. Such sources, which act in a way akin to heating by natural sources such as the sun's rays, are different from conventional IR LPG heaters or ceramic heaters which function as single-point or concentrated IR sources. Diffuse IR radiation is thus able to reach a large majority of the surface in the building, room or material provided that the source is correctly located.

It is a feature of our invention that the diffuse IR from these sources is applied under specific range of conditions that give optimal performance. For example it important to limit the increase in temperature of the surface, and thus actual temperature of the material being dried to those it would normally experience in hot weather conditions. Thus the surface temperature should not heat up by more than 25°C above the ambient temperature encountered at the site of use under normal weather conditions and the actual surface temperature should not exceed 35°C. More preferably, the surface should not heat up by more than 20°C over ambient and the actual surface temperature should be in the range from 5 to 35°C. This both limits potential damage to the material being dried and makes the process efficient. The source should be positioned so as not to over- or under-heat the surface which is being dried. To do this the source is positioned between 0.5-3.5m from the surface, more preferably 1.5-2.5m away from the surface.

In one embodiment, the diffuse IR source is comprised of a heated plate, which may be flat or shaped, having a radiative surface area of from 0.25m^ to 1.75m^ more preferably from 0.3m^ to 0.9m^ The plate can for example be heated by an electrical or other power source with a power of 0.25kW to 5kW, more preferably 0.5-1.75kW. Diffuse IR from the source should be applied over more than 3hrs, preferably 1 day, more preferably several days or even weeks. The process can be increased in efficiency by insulating the back surface of the heated plate and stopped once the desired level of humidity is achieved in the material. However it is also envisaged that the diffuse IR source may be on a controller so that it can be switched on and off automatically for chosen periods. If so desired the drying process can be augmented by the use of natural or forced ventilation.

In one embodiment, the diffuse IR source is one which creates infrared radiation having a wavelength envelope substantially in the range 3-15 microns; preferably mid- to long-wave infrared radiation in the range 6-15 microns. By the term substantially is meant that greater than 75% preferably greater than 80%, 90% or even 95% of the radiation emitted by the source has a wavelength within the envelope.

In another embodiment the source itself will be waterproof and/or washable and/or thermostatically controlled and/or mounted to allow the plate to be tilted and/or on a moveable frame.

In addition to describing the ranges of operation we also define suitable total equivalent power per unit of surface area being dried. For the purposes of this invention, it is assumed that all the power supplied to the diffuse IR source is transmitted as radiation and then all this radiation arrives on the surface being dried. This is unlikely to be valid in reality, as for example some radiation will arrive at other surfaces but this approach can be used to describe the conditions required for different sizes of surface. In our invention the diffuse IR source should deliver equivalent total power per unit of surface area being dried of greater than 50W/m^ to 500W/m^ more preferably from 100 W/m^ to 500W/m^ and most preferably from 100 W/m^ to 250W/ml

The highest power levels need to be carefully chosen in order not to adversely damage the material and cause e.g. cracking or feathering in plaster work. Thus power levels of 5kW and above applied to the diffuse source (equivalent of 500W/m^ per unit of surface area for a wall of lOm^) would not only be costly and unsuitable but may cause overheating and damage to the surface or material being dried.

Use of diffuse IR, according to the present invention is especially efficacious in reducing drying times. Thus in a second aspect of the present invention there is provided a method of drying damp materials characterised by the steps of (1) placing a diffuse IR source between 0.5-3.5m away from the material to be dried and (2) applying diffuse IR radiation having a wavelength envelope substantially in the range 3-15microns to the material for a period of at least 3 hours at a power in the range greater than 50 W/m^ to 500W/m^ under conditions such that the increase in surface temperature of the material being dried is limited to 25°C above ambient and does not exceed 35°C . In one embodiment, the method is practised after plastering or rendering a wall or to dry new or recently repointed brickwork. In yet another it is used to advance the drying time of paint, concrete, cement, grouting and the like. In another it is practiced in a room or space which has been flooded or has other damp issues. In yet another embodiment, the method further comprises the step of monitoring the humidity in the plaster or wall to confirm it has achieved the required level. The construction materials may have been previously rendered damp by water and/or other solvents or fluids used in their manufacture or deployment. In another embodiment the method may include the step of (3) ventilating the surface at the same time as step 2) is carried out.

The present invention will now be illustrated with reference to the following Examples: Demonstration of Application comparing 2 recently plastered walls in 1 room A diffuse IR source was placed at 2m from a recently plastered wall in a room of floor dimensions 3x4m. The wall it was facing was of approximate dimensions 3x2.5m. In this case the source was a 1200x600mm heated glass plate. The heated plate was insulated behind the glass encouraging the majority of radiation to transmit through from the plate. The plate was further mounted in a stainless steel mounting fully sealed to water. The plate was powered at 1.25kW. This is an equivalent IR radiation power of 165W/m2 by the definition used above. In reality the side walls and ceiling also received some of this radiation. The drying process was practised over a period of 3.5hrs. A side wall was used as a control which did not receive any direct radiation from the IR source although did experience the increase in ambient temperature in the room. Visual observations and pictures were taken and the drier area indicated by a change in plaster colour was estimated (this process has errors of approximately +/-10%). Surface temperatures were measured at various points on the 2 walls. Results are shown in Figures 1 and 2.

Visual results and estimates of dried area indicate that the wall receiving the diffuse IR dried more quickly than the control wall. Surface temperatures in the wall receiving the diffuse IR increased by 12°C and final temperature was 16°C. The control wall showed some drying due to the natural setting process taking place which was also increased due to the increase in ambient temperature increasing surface temperature of approximately 5°C.

These results indicate the use of diffuse IR can reduce drying times in an efficient and effective way.

Demonstration of Application comparing rooms with and without a diffuse IR source

In this example two similar rooms on a building site which had been recently plastered were used; one as a control and one as a test room with a diffuse IR source placed at 1.5m from the wall. The trial took place in March in the UK. The source was a heated glass plate of 1200x600mm. The heated plate was insulated behind the glass encouraging the majority of radiation to transmit from the plate. The plate was further mounted in a sealed stainless steel mounting fully sealed to water. The plate was powered at l.lkW. Wall surface temperatures were 5-10°C warmer on the wall receiving the diffuse IR. Assessment by experts on site deemed the test room dried out 7 days faster than the control room. Overall drying time for the test room with the diffuse IR source was around 7 days compared to around 14 days for the control room.

Claims

Claims:

1. Use of at least one man-made diffuse IR source having a wavelength envelope substantially in the range 3-15 microns to advance the drying times of damp materials characterised in that a total equivalent power per unit of surface area of material to be dried of from greater than 50 W/m^ to 500W/m^ is applied over a period of at least 3 hours under conditions such that (1) the surface temperature of the material being dried does not increase by more than 25°C over ambient, (2) the actual temperature of the material does not exceed 35°C and (3) the diffuse IR source operates between 0.25-5kW and is positioned at between 1.5m to 3.5m from the material to be dried.

2. Use of at least one diffuse IR source as claimed in claim 1 characterised in that the drying time is 1 day or more.

3. Use of at least one diffuse IR source as claimed in claim 1 characterised in that the drying time is more than 1 week or more.

4. Use of at least one diffuse IR source as claimed in claim 1 characterised in that the total equivalent power per unit of surface area is from lOOW/m^ to 500W/m^

5. Use of at least one diffuse IR source as claimed in claim 1 characterised by comprising a total equivalent power per unit of surface area of material to be dried from greater than 100 W/m^ to 250W/m^ applied over a period of at least Iday, such that the surface temperature does not increase by more than 20°C and actual temperature does not exceed 35°C and the source is powered between 0.5-1.75kW and has an heated area between 0.3-0.9m^ and is positioned at between 1.5m to 2.5m from the material being dried and the radiation has wavelengths substantially in the range 6-15 microns.

6. Use at least one diffuse IR source as claimed in any of the preceding claims characterised in that the material to be dried is a construction material, selected from plaster, rendering, paint, grouting, cement or concrete.

7. Use at least one diffuse IR source as claimed in any of the preceding claims characterised in that the material to be dried is a repair or decorating material.

8. Use at least one diffuse IR source as claimed in any of the preceding claims characterised in that the material to be dried has incurred flood damage.

9. Use at least one IR source as claimed in any of the preceding claims characterised in that the material to be dried has been prepared using water or other solvents or fluids.

10. A diffuse IR source for use in any of the preceding claims characterised by being waterproof and/or thermostatically and/or computer controlled.

11. A method of drying damp materials characterised by the steps of (1) placing a diffuse IR source between 0.5-3.5m away from the material to be dried and (2) applying diffuse IR radiation having a wavelength envelope substantially in the range 3-15 microns for a period of at least 3 hours at an equivalent power per unit of surface area of material to be dried in the range of from greater than 50 W/m^ to 500W/m^ under conditions such that the increase in surface temperature of the material being dried is limited to 25°C above ambient and does not exceed 35°C.

12. A method as claimed in claim 11 characterised by being practised in a room or space which has been recently plastered or rendered.

13. A method as claimed in claim 11 characterised by being practised in a room or space which has been flooded or has other damp issues.

14. A method as claimed in claim 11 characterised by being practised on a material which has been prepared or deployed with water and/or solvents or fluids.

15. A method as claimed in either of claims 13 or 14 characterised by comprising the further step of monitoring the humidity in the plaster or wall to confirm it has achieved the required level.