Situation​

Various processes require drying processed materials. In the heating process for drying, three modes of heating transfer take place, but in each case, depending on the method of heating used and the construction of the plant, generally only one way to transfer heat will be used, while the other two participating in a lesser extent.

 

Problems

 

  •      In the case of heat transmission by conduction and convection, the heating of the bodies depends on the temperature difference between the heat source and material. As the material is heated, temperature raising speed decreases, this decrease is becoming even more pronounced the higher the temperature difference between the medium and the material shrinks.

  •      The material submitted by convection heating can not exceed the ambient temperature.

  •      Heating by convection is done slowly.

  •      Heat losses are significant, fluids getting warm and disperse heat, warming the enclosure walls and carrying the heat. Controlling the temperature is achieved with difficulty, there is unevenness in the enclosure, stratifications.

 

     The behavior of materials at drying is the basis for calculating the real base of industrial dryers. This cannot be determined only experimentally, because the factors influencing solvent evaporation of moisture may vary in space and time and the material that is dried changes characteristics during the drying process.

     In the drying process, heat is transmitted only to the surface of the material because warm air can not penetrate its mass. The surface material is transmitted by thermal conduction heat.

 

     Because of the low thermal conductivity of the material, the temperature equalization of the interior and exterior occurs slowly on its surface while keeping the higher temperature and in the mass and adjacent surface support, a lower temperature. As a result of the temperature gradient thus created, the material starts to harden from the surface to the inside. On the free surface a crust is produced that prevents the exit of water/solvent from inside the material.

 

     If drying by convection (hot air or flue gas), the temperature of inner layers is lower than the surface temperature and the final temperature can not exceed the final temperature of the body of the heat carrier. The moving humidity from inside the surface material is only because of the existing moisture gradient between the inner and outer layers of the material. In this case the temperature inside the material is lower than on its surface, so the temperature gradient has a negative influence and slows the movement of humidity in the material by creating a crust that prevents moisture from material output. Temperature gradient will lead to the uneven expansions and contractions of upper layers, these will be subjected to stretching and the lower ones will be subjected to compression and vice versa in the final phase. The tensions that arises in the material during the heating process becomes even greater while drying.

 

Implications

  • Low productivity

  • High energy consumption

  • Large-size complex installations

  • The possibility of thermal degradation of the heated material

     Following the appearance of the crust, is the formation of bubbles and cracks on the surface of the lacquer layer, defect that makes the varnishing or lacquering unusable. To accelerate drying through convection, temperature must rise as much as possible, the effect of forming cracks is stronger with the rise of the temperature, so as the temperature gradient is higher.

     The temperature of the carrier (hot air or flue gas must be properly regulated and the subject material can not exceed the drying temperature).

     If the productivity of drying by convection is low, the drying process is proceeding slowly and it takes more hours because the drying speed is limited by the materials resistance to uneven efforts and stretching. If accelerating the drying, the material degrades, develops pores, cracks, blistering etc.

 

Solutii

 

1. Read up on the following sources:

 

Comparison between heating through convection and heating through radiation

 

2.  Use local sources of radiation heating, specific for each application

 

 

3. Call on out ESCO services:

Performance contracting

Technical consultancy

Studies of necessity and opportunity

Feasibility studies

Projection

Production

Installation/Montage

Punere in functiune

Commissioning

Authorizing of operations

Maintenance / Preventive repairs

Service/Repair

Regular technical checks

 

 

Benefits

 

  • In the case of radiation heating, transmitted energy is independent from the heated material, the heating speed is slowed down only by the possible cooling convection effects from around the body, or the reflection of the energy in the body.

  • Heating through radiation can lead to the elevated temperatures well above ambient temperature, depending on the source of the radiation and the distance it can reach temperatures of 300-350°C.   

  • Heating materials exposed to radiation is done very quickly, radiant energy arises immediately after commissioning of the source of radiation

  • Heat losses are greatly reduced, electromagnetic radiation don’t heat ambient environment and they are under the form of a beam upon the body that is needed to be heated

  • Heating by radiation with our sources allows a continuous and precise temperature control.

 

     The drying process is based on the exposure to a radiation source, more precisely to metallic fabric radiants at a distance from the material. After a part of incident radiation, it penetrates the mass of the material. Radiated heat arises inside the irradiated layer. Through this a better heating is produced, but an even faster heating in the entire mass of the material.

     The drying process is done from the inside and water/solvent may leave the material without danger of formation of blisters and cracks that occur when accelerated by convection drying is used.

 

  • high share drying radiation in tunnel ovens and drying possibility to ensure mixed convection (exhaust gas or hot air recovered) enables application even on relatively complicated pieces with different shapes.

  • Easy setting and intensity modulation of the radiation

  • The crust does not occur on the surface of the material, the drying is made from the inside to the outside

  • Drying time is 5-6 times lower compared to drying with hot air of flue gas

  • Higher energy efficiency and the possibility of recirculation and heat recovery from flue gases

  • Emitted pollutants are much lower due to both reduced fuel consumption and the use of radiant burners with metallic fabric

  • Space occupied by equipment is decreased by 300%, mainly due to the reduced length of the dryer

  • Fast commissioning and for very low input regime

  • The possibility to set broad range of speeds to the conveyor, the intensity of radiation and interior temperature dryers causes them to be able to adapt to different types of paint and varnish, or various types and shapes of parts.

 

 

Radiation drying solutions

Request the optimal solutions for the radiation drying.

You will receive a questionnaire with the required data as soon as possible.

CALORSET SRL​ , 

Str. Uzinei nr. 60 , Carei, 445100,  Romania

Tel.  0040261861220  

Fax. 0040261861221 

GSM. 0040744816294

office@calorset.com