What Are the Savings from Replacing Calrod Heaters with Cast-In Aluminum Platen Heaters?

Many older platen presses utilise tubular calrod-type heaters that are inserted into drilled holes in a steel plate. The thermal resistance is due to the air gap or the loose fit between the heater and the plate. This bottleneck is eliminated by cast-in aluminium heaters where the element is inherent to the plate.

Advantages of construction and performance of cast-in aluminium heaters
Aluminium platen heaters are cast aluminium with the heating elements integrated in the aluminium during the casting process. The design provides tight metal-to-metal contact between the element and the platen, avoiding the air gaps typical of previous systems. By removing the air gap, the thermal resistance is greatly reduced, and the heat can more easily transfer from the heating source to the platen surface.

This improved heat transmission leads to various performance benefits:

Rapid heating periods : The direct contact of metals allows the heater to heat up to the target temperature faster than typical heaters with air gaps.

More even temperature distribution: Improved contact results in a more even dispersion of heat throughout the surface of the platen.

Heating elements at lower operating temperatures: Lower thermal resistance means the heating elements can run at lower temperatures and still attain the same surface output. This will decrease the burden on the heater and increase its lifespan.

Cast-In Aluminium Heaters for Energy Efficiency
One of the biggest benefits of cast-in aluminium platen heaters is the energy savings obtained from the faster heat-up times. The transient phase has increased heat loss to surrounds since the heat-up process is delayed due to the air gap with conventional Calrod heaters. Faster heat-up time of cast-in heaters minimises these losses and reduces energy usage.

Furthermore, being able to run the heating elements at a lower temperature without sacrificing performance lowers power consumption even further. Lowering the temperature of the element means less energy is needed to keep the same output at the surface . So less energy is used overall .

By replacing standard Calrod® heaters with cast-in aluminium platen heaters, significant energy savings can be achieved on either new installations or retrofits in the field to optimise heat transfer efficiency.

Technical Issues
The performance improvements possible with cast-in aluminium platen heaters are significant, but there are certain technical considerations.

Calrod heaters: These are put into drilled holes in the platen and employ thermal grease to minimise the air gap. But even with thermal grease, there is some contact resistance because the heater and the platen don't match well.

Cast heaters: These heaters are part of the platen. They are very efficient but are not repairable. If one element breaks, usually the whole platen has to be replaced.

Summary
Cast-in aluminium platens are a major efficiency improvement over standard tubular Calrod heaters. The shorter heat-up periods, lower energy usage and higher uniformity of temperature of these heaters result in obvious energy savings, particularly in high-demand applications. For a given application, the trade-off between the efficiency gains and the inability to repair individual elements should be evaluated. Cast-in aluminium platen heaters are an attractive alternative for optimising thermal processing in industrial applications, with energy efficiency still a consideration for reducing operational costs.