INFRARED Ap plicat ion: Heat ing b y Ra d iat ion INFRARED - Infrared Heaters with Ceramic Insulation - Figure 1 GENERAL CHARACTERISTICS INFRARED radiators are the best solution to set up radiation heating systems based on the use of infrared rays. Their emission factor is 0.96, i.e. very close to the maximum theoretical value of 1,and their manufacturing standard allows to insure: time the desired temperatures without presenting significant heat losses throughout the oven inlet and outlet sections. In addition, if the operational temperature is adequately selected, high specific power densities (higher than those typical of conduction or convection heating), can be obtained. TECHNICAL DATA (see Figure 1) 1. RESISTIVE WINDING spiral made of Nickel/Chrome 80/20 DIN 17470, material n° 2.4869 2. INSULATION made of high purity ceramic which presents a high resistance to thermal shocks and a high dielectrical rigidity 3. SURFACE FINISH particular treatment that protects the insulating body from oxidation, corrosion and water sprays. 4. FIXATION BASE standard for a 15x41 mm slot 5. POWER SUPPLY CABLES made of Nickel, insulated using ceramic bushes resistant to high temperatures 6. THERMOCOUPLE type K (Nickel/Chrome-Nickel - optional) The heating by radiation allows to heat easily and quickly moving objects. The dimensional and manufacturing characteristics of the heat radiators allow the construction of “open” ovens, normally installed around mobile surfaces (e.g. conveyor belts) inside which it is possible to reach in a short This last consideration is clearly shown in the graph of Figure 2 where the specific power transferred by forced convection (3 different air velocity values are considered) and the one obtained by heat radiation (2 different values of the emission factor are analysed) are compared. The selection of the heat radiators operating temperature shall be performed taking into account different and conflicting needs: on one hand the specific radiated power increases at higher radiators operational temperatures and reaches its peak for wavelength values around 2 µm (see graph in Figure 3), on the other hand, the heat absorption by the radiated bodies is higher when the radiators temperature is low (see Figure 4), which correspond to wavelength values in the range 4 ÷ 5 µm. Since a radiation heating system based on 300 ÷ 400 °C operating temperatures would imply a too long heating time, typically the operating temperature is set to 600 ÷ 800 °C which corresponds to a peak emission wavelength of about 3 µm (see Figure 5). HEATING BY RADIATION The rapid growth of the technology in the field of plastic materials processing has requested the development a large variety of electric heaters, capable to transfer efficiently the heat in the most different operational conditions. The most common applications adopt the heat transfer by direct contact or by convection. There are cases, however, in which peculiar process characteristics (rapid working cycle, necessity to heat moving objects, impossibility to seal the heating process inside a volume that is closed to the external environment) do not allow to use effectively the heating by conduction or convection. In these case the most appropriate solution is to adopt a heat transfer by radiation. Transferred Power (kW/m²) Figure 2: Long operational life Fast heat transmission Constant emission along the operational life Perfect heating uniformity Easy installation

INFRARED Ap plicat ion: Heat ing b y Ra d iat ion The individual radiators power size is also a function of the application. In fact, depending on the application, radiators with different heating powers are recommended (see Table 1 for the selection criteria). Figure 3: radiated power as a function of the operating temperature and of the wavelength Table 1: radiators heating power selection criteria APPLICATION Water Evaporation Radiated power (W/cm²) Drying of plastic or latex coatings Fast drying of glued surfaces Thermoforming, skin-pack Drying of adhesives onto glued parts Heating and drying...

INFRARED Ap plicat ion: Heat ing b y Ra d iat ion The distribution of the radiated thermal energy is not constant in the volume around the radiator. It is maximum in the direction perpendicular to the radiator axis and decreases when the distance from this direction increases. Also this aspect shall be taken into account in the choice of the radiators and in the definition of their position within the heating system. In particular, if the product to be heated has a flat shape and it can be positioned parallel to the radiators assembly, it is more convenient to use flat radiators, placed as much...

INFRARED Ap plicat ion: Heat ing b y Ra d iat ion INFRARED RADIATORS RADIATORS TYPE IC and TYPE IP which are available on stock are listed in the following tables. CURVED RADIATORS mm 123 x 60 Code without thermocouple Code with thermocouple type K (NiCr/Ni) 27IC0601230125 27IC0601230200 27IC0601230325 27IC0601230500 Average Surface Temperature (°C) 415 500 620 730 Heating rate from 0 to 90 °C (°C/min) 73 108 170 240 Cooling time down to 100 °C (min) 7.5 9 9.8 10.2 Heating rate from 0 to 90 °C (°C/min) 52 88 130 200 Cooling time down to 100 °C (min) 4.8 6.5 7.9 8.9 Code with thermocouple type...

INFRARED Ap plicat ion: Heat ing b y Ra d iat ion MOUNTING PANELS RAD TYPE IC Figure 10 RAD IC panels are designed to allow the installation of the curved radiators TYPE IC 123 x 60 and 245 x 60. They consist of a reflecting bow made of stainless steel and by a Ushaped structural support made of aluminised steel. If requested, a protection box, to enclose all the electrical contacts, can be provided (see solutions OPEN PANEL and CLOSED PANEL in Figure 11) The U-shaped support is perforated to make the routing of the cables possible and to allow the fixation of the electrical terminals. The reflecting...

INFRARED Ap plicat ion: Heat ing b y Ra d iat ion MOUNTING PANELS RAD TYPE IP/123 Figure 12 RAD IP/123 panels are designed to allow the installation of the flat radiators TYPE IP 123 x 123. They are manufactured using a flat reflecting sheet made of stainless steel and by a U-shaped structural support made of aluminised steel. Available lengths and mounting systems are the same as those presented for the RAD IC panels. Figure 13: RAD IP/123 panels envelope U-SHAPED SUPPORT with EXTERNAL FIXATION OPEN PANEL with INTERNAL FIXATION OPEN PANEL with EXTERNAL FIXATION CLOSED PANEL INFRARED QUANTITY...