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Reflector and Panel Information from Back Issues of The Salamander News

Salamander Radiant Emission Grid. April, 1998 issue
Take Note of Reflector Thickness. May, 1998 issue
Installation Instructions for Ceramic Emitters. June, 1998 issue
Custom Panel Design. June, 1999 issue
Sizing and Layout. November 2000 issue

April, 1998 issue:

Salamander Radiant Emission Grid           The Salamander radiant emission grid can be used to determine the proper ceramic emitter spacing when used in an application such as an infrared panel. In order to achieve an even heat pattern it is critical that the emitters are spaced so that their radiant emission patterns overlap when reaching the target. The more overlap that occurs, the more even the heat will be across the face of the product being heated. The area of highest radiant emission intensity for a single emitter is shown within the two dark crossed lines on the grid. In order for element emissions to overlap, the dashed line shows an intersection point at a distance of 7" will occur if the emitters are placed a distance of 2" apart from edge to edge. This same concept should be used to either determine the distance to place the product if using an existing panel, or placement of emitters if building a panel to guarantee radiant emission overlap.

May, 1998 issue:

Take Note of Reflector Thickness

    When using the single piece clip provided with each Salamander ceramic element, attention must be given to the gauge and type of metal present in both new and existing applications. Anything other than the accepted 20 to 24 gauge (.036"-.025")(.9mm-.6mm) thickness of aluminized of stainless steel could result in difficulty in securing the mounting clip. In some cases, unwarranted damage to the towers could result if excessive force is used.
    If you are having problems securing the clip, and are using the correct gauge metal, care should be taken to check that the slot equals the recommended size of 15mm x 41mm (1.61" x .59").
    If your reflector metal is thicker than the suggested gauge, a two piece clip could be tried, but simply enlarging the slot could alleviate the problem. Using the correct size slot allows more of the tower body to be accessible to the clip and permit easier attachment.
    If the slot is made too large, the elements may be loose causing unwanted movement. A thin metal spacer placed between the clip and reflector should tighten the connection. If the problem continues to exist, the sales office should be contacted.

Emitter Mounting, Single Tower

Emitter Mounting, Double Tower

Mount emitters in a 20 to 24 gauge [.036" (.9mm), .025" .6mm)] aluminized steel or stainless steel reflector. The single piece retaining clip(s) secures the emitter to the reflector as shown. Two piece mounting clips are available if required. Do not use excessive force when installing clips, damage to the mounting tower may result.

Wiring & General Emitter Operation

Electrical connections should be made directly through high temperature ceramic terminal blocks (sold separately). Nickel plated copper wire, with insulation suitable for the load amperage and operating temperatures, must be used to make the power connections to the ceramic terminal blocks. All electrical wiring must be done in accordance with local electrical codes by a qualified service technician.

For best results, the surface temperature of the Salamander ceramic infrared emitter should be controlled using an open-loop (percentage timer) or a closed-loop (thermocouple feedback with digital temperature control) system. The infrared emission intensity is directly related to the surface temperature of the ceramic body (see the Salamander technical manual for more details).

June 1999 - Custom Design

November 2000 issue:

The Information - Once a customer has decided to change over to or use ceramic heaters, their next question usually concerns sizing and layout. The engineering staff at Mor Electric Heating does this as routine and all distributors should be competent in providing this service. There are initially some basic questions to be answered:

    1. Is this going to be a drying/evaporating application or does the product need to be heated for processing?
    2. Which type of oven is needed: stationary, "batch", or conveyorized?
    3. If it is a drying application, how much water or solvent needs to be evaporated?
    4. What temperature does the product need to be heated to?
    5. How fast does the heating process need to be?

Additional product information is also needed such as, physical size, weight, material, color, and the ambient or "starting" temperature of the product, including specific heat and emissivity, if known.

Using this information, a heat loss may be calculated to determine the power required by using this basic formula:

Step 1  
(w/hr)/(in²⁾ = {(weight) (spec heat) (rT)}/3.412 Btu/w

However, knowing the power requirement is not enough. For radiant applications the emissivity must be factored in. Using the emissivity of the product and the estimated emissivity of the emitter in the following formula allows you to establish the "effective" or average emissivity between the two points.

Step 2 
e = 1/(1/e₁ + 1/e₂ - 1)

e1 = emissivity of the source
e2 = emissivity of the target

Once the effective emissivity is know, the Stefan-Boltzmann Law is used to determine the source temperature of the emitter:

T₁ = source temperature, e = effective emissivity, watt/in² = the amount of kW needed

This information, combined with the space required, determines the number and wattage of the individual heaters required. Spacing between emitters is typically 1/4" (6mm) to 1" (25mm), and the emitters are placed in the heated area according to the zoning requirements of the application and the need to balance 3 phase loads. On the back of this newsletter is an example application done using these steps.

The Example - A request was received for heating information on an application requiring evaporating water from water-based adhesive applied to a wooden board before being able to adhere the finished surface to the board. Following the steps outlined on the previous page, the following is the how we arrived at the required information.

Information received from the customer:

    1. This is obviously an evaporating application.
    2. The oven will need to be conveyorized to the point that it will be shuttling back and forth in front of a stationary product.
    3. The amount of water needed to be evaporated is 2.5 grams per sq. ft.
    4. Because we are evaporating water, it needs to be heated to 212° F.
    5. 2.5 grams of water needed to be evaporated every 4 seconds.

Before going into step 1, the weight in grams had to be converted to pounds per square inch.

Step 1  
(w/hr)in² = {38.27 x 10-6 (1.0)(212-65)}3.412 
(w/hr) in²= 1.65 x 10^-3

 When doing applications involving water evaporation the latent heat of vaporization must be considered and is determined by the following formula:

{965Btu/Lb(38.27 x 10^-6)} 3.412= 10.82 x 10-3 = Latent heat evaporation

Add the wattage required to raise the heat with the latent heat of evaporation to find the

Total Power Required = (1.65 x 10-3) + (10.82 x 10-3) = 12.47 x 10-3 (watt/hr) / in²

Now that we have the power required we must adapt it to how fast the waters need to be evaporated, which was stated as every 4 seconds, by using the following formula:

warm up time = watt-hour/in² x 60 min. (watt/in2)

watt/in2 = 12.47 x 10^-3(60) /watt/in2 = 12.47 x 10^-3(60)/ (4/60)= 11.223 watt/in2

Now that we have this information we are ready to solve for emissivity.

Step 2
e = 1 /. (1/.9 + 1/.93-1)

e =.84

Using the emissivity we move to the Stefan Boltzmann formula.

Step 3

T₂ = (65+212)/2 = 332.5 Deg. K

A graph may be used to determine the element wattage required to reach the identified source temperature. Graphs such as this can be found in our Technical Manual or on our Internet website. In this case our 951°F indicates that we use 800-1000 watt FTE size elements. I chose to specify FTE-1000 elements knowing that they are a standard and typically stocked element.

Working with our heated area of 5 ft. x 30", and using FTE-1000 elements, spaced as recommended, we would need 91 elements. The customer stated no special zoning was required. Are you ready for the challenge?

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