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faster than the round heater. The end result – the flat tubular gets the heated liquid into the work zone faster than when using a round tubular. The flat tubular heater has about a 50 percent greater surface area than a round tubular. This surface area design improvement is the key to lowering watt density for the same length heater or reducing the heater size while maintaining the same watt density.
Flat tubular heaters are ideal for fryer applications because their shape lifts the oil into the work zone better than round heaters.
Greater Buoyancy Force This natural convection phenomenon partially depends on the ratio of a buoyancy force to the viscous force of the fluid being heated. The buoyancy force or the flow of liquid up and across the heater surface is mainly determined by the length of the heater sides. The side of a flat tubular heater is typically 1 in. (25 mm), compared to the 0.43 in. (10.9 mm) or less dimension of a round tubular element. The flat tubular heater’s smaller edge and longer side creates a buoyancy force up to ten times greater than a round tubular heater depending on the material being heated.
Faster Heat Up Flat surface technology provides faster heat up and recovery times than round tubular heaters. Their unique shape minimizes coking and oil degradation, and enhances the flow of the oil past the element’s surface, helping to pull heat away from the heater sheath. Compacted magnesium oxide (MgO) insulation transfers heat away from resistance wire to sheath material and media more efficiently, shortening heat-up time. In addition, the heater lasts longer because it runs at a significantly lower sheath temperature than an equal watt density round tubular. This also prolongs the life of the oil which shortens and reduces costs from frequent changing.
Smaller Dimension Normal to Flow This feature refers to the width dimension of the heater that the liquid flows around. Typically, a narrower dimension will give a smoother and faster liquid flow. For example, the round tubular’s wide dimension, nearly a half-inch, inhibits the flow of liquid. It causes currents which disrupt the flow and the flow rate is somewhat slower.
If coking is a problem, it is an indication that the sheath temperature is too hot and is burning the oil. A flat tubular heater will provide a lower sheath temperature than a round tubular element, without reducing wattage or watt density. Coking is also reduced by the wiping action that occurs as the heated liquid flows past the heaters surface. The result is less liquid degradation and longer liquid life.
The flat tubular heater, on the other hand, has a much thinner dimension 0.235 in. (5.97 mm), which reduces the drag forces on the liquid flowing past the heater. This allows the liquid to move past the flat heater
Watlow’s flat tubular heater, called FIREBAR®, has long been a standard in the foodservice industry. An independent study that adhered to the American Society for Testing and Materials (ASTM) standards, called
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