Humans have used heat to dry wetness and wet materials from times immemorial. The heat from natural sources such as the sun, man-made fires as well as artificial sources has been used for the purpose. A typical modern example of an artificial source for drying wetness is an electrical tumble dryer for clothes.
When it comes to drying modern day buildings, the use of heat has been limited. Even today, the damage management technician uses technology and procedures developed in the sixties and seventies with only minor variations. The changes that have occurred over the times have been superficial and minimal.
The damage management technician works by drawing in the moisture from the building materials and subjecting it to a phase change whereby it becomes vapour (evaporation). To help the moisture evaporate, the air in a wet room is subject to a continuous lowering of vapour pressure. This is done with the help of dehumidifiers and directing the air to flow over wet surfaces. This action helps to push the moisture from the materials into the air (having lower vapour pressure) that surrounds it.
To the question whether this process works, the answer is yes’ and it can be implemented in many designs. However, more efficient methods can be used which will ensure that the moisture is removed quickly and the building is returned to its owner in a shorter time.
One simple method that can be used is to give enough energy to the moisture to enable it to escape from the material that contains it. This transfer can be made more effective when the air around is more thirsty for the moisture.
Simply adding heat to the material helps it to transfer this energy to the water molecules that are contained within it. Following principles of physics, this helps to increase the vibration of the particles and consequently their kinetic energy. The resultant increase in momentum helps the water molecules to escape from the material into the ambient air. The heated air also accepts the moisture quickly and the result is faster evaporation.
However, there are two important reasons as to why heat is not extensively used in the damage management industry. First and foremost, there is a lack of knowledge as to how heat works in the process of drying materials. Adding to the woes are the wrong/exaggerated stories that float around.
Secondly, heat has been hitherto used mainly in high-energy systems. The high temperatures blasted out of such systems stresses building materials that are delicate to their extremes. Moreover, the operations need to be constantly monitored by technicians who are experts in handling these systems.
What are the different methods by which heat energy is transferred?
- Conduction is the method which facilitates heat transfer through direct contact. When one heated surface is placed in direct contact with another, the heat is transferred from the surface with higher temperature to the one with lower temperature. Everyone well understands how our hands burn when we touch a hot surface.
- Convection occurs in liquids when heat is supplied to the liquid. Transfer of heat energy to the liquid results in a mass movement of the liquid molecules called convection currents. Convection currents help to carry the heat from the solid surface of vessel containing the liquid. Water boils in a pan, for instance, when the heat is transported from the hot surface of the pan to water.
- Radiation is the transfer of heat using the principle of electromagnetic radiation through empty space. The heat radiates from the source to the object to heat it. The earth is heated by the sun’s rays by electromagnetic radiation.
The electromagnetic spectrum is composed of a wide array of radiations: short waves such as gamma rays, X-rays, visible light and longer waves such as microwave and infra-red radiations. The specialised drying technologies primarily use heat in the infra-red spectrum of the electromagnetic radiations. It is also predicted that microwaves will also be used in the near future for the purpose of drying building materials.
Though it is a known fact that heat is of great importance helping moisture to evaporate faster, the main problem that has stopped users from using heat in building drying has been the ability to control temperature and heat energy.
Therefore, the point to be discussed is how to use thermal energy in such a manner so as to speed up the building drying process by overcoming the current obstacle of not being able to control heat energy that has limited its use.
Firstly, it is a well known fact that raising the temperature above 25 degrees centigrade within a building is just sufficient to increase the rate of evaporation. Raising the temperature by about 30 degrees steps up the evaporation rate without causing any stress on the materials. This is applicable to materials in both old and new buildings. The point to be noted here is that, in the first place, a lot of heat energy is not required and, if the temperature is raised gradually, then the materials are not overtly stressed during the conductive or convective heat transfer processes. Thus, if the rise of temperature in building materials is steady, then the material does not experience any of the side effects that would have been otherwise caused by blasting heated air over the material.
By constantly monitoring the temperature inside a room so as to establish a safe level of absolute humidity to promote faster evaporation but helping to maintain a level of relative humidity prevents hygroscopic materials from developing secondary damage while simultaneously facilitating safe evaporation.
The system to be used, therefore, should basically be capable of heating up gradually to a safe level. However, it should be self-monitoring in that it should constantly replace the air with fresh dry air in the room and remove the moisture to start the process over again. This helps to maintain environment control.
It is a good idea to remain in touch with the technician during the drying process and after it is completed. The system described above would be an ideal one that most modern damage management technicians can use.
As to whether such a drying system exists? Yes, our system uses convective heat transfer with intelligent software systems that allow fine controls which can be used by damage management technicians. Using heat optimally for drying of building materials with modern computerised systems is now a reality.