The Duravant family of operating companies serve the food processing, packaging and material handling segments.

Steam Energy: Continuous Thermal Heating in Spiral Ovens


The spiral oven cooking process occurs in a single oven enclosure on a continuous conveyor belt which conveys food upward through multiple, circular tiers. Due to the box-shaped design of this single enclosure with relatively narrow openings for infeed and discharge, the Marlen spiral oven offers effective utilization of the amount and kind of heat energy contained within that cooking space. One interesting way advanced spiral cooking technology maximizes product yield and capacity is by using super-heated steam to dramatically increase the heat energy in the oven enclosure.

Decrease Cook Times and Maximize Yields with Super-Heated Steam

Since the spiral cook process operates within an oven enclosure that features a smaller footprint and reduced openings as compared to traditional linear ovens, a spiral oven offers precision with the amount and kind of heat energy used to cook a food product. In particular, the Marlen spiral oven uses super-heated steam to create a cooking environment that is arguably more efficient than traditional convection cooking. In fact, this super-heated steam environment has with 263 kcal/m³ more energy (when cooking at 230°C) versus convection cooking at the same temperature. This reduces overall cook times and maximizes product yields.

So, what is super-heated steam? Super-heated steam is the non-visible clear, colorless gas obtained by heating ordinary steam at 100°C to a higher temperature under normal pressure. The Marlen spiral oven requires that the steam supplied be greater than 5-bar (80 PSI). Importantly, this high-pressure steam supply is then introduced directly into the oven’s heat exchanger. While in “Roast Mode,” this steam supply of greater than 5 bar (80 PSI) maintains a gaseous state as a vapor and continues to be heated by the oven’s heat source—this “super-heats” the steam vapor and creates more available energy with which the product will be cooked. Thus, the super-heated steam will have more energy with which to cook the product than the energy contained in ordinary hot air from a convection oven. This approach is like “super-charging” an engine that allows the production rate to speed up and the product yield to be optimized.

More Heat Energy than an Ordinary Convection Cooking Process

To be more specific, we can calculate the heat energy of the super-heated steam within the oven and compare it to the heat energy of the heated air within a convection oven.

First, we must calculate the energy contained in the water which turns into super-heated vapor. This occurs in three parts: the energy needed to take liquid water to 100°C, the energy needed for the liquid water to change phases into a vapor at 100°C, and then the energy needed to take the water vapor from 100°C to 230°C. So, we must multiply the specific heat of the liquid water by the temperature difference to bring it from 20°C to 100°C, then add that value to the evaporation heat of water, and then add that sum to the specific heat of the water vapor multiplied by the temperature difference to bring the vapor from 100°C to 230°C. By multiplying this sum with the density of the vapor contained in the spiral oven enclosure, the result is 298 kcal/m³.

Second, we must calculate the heat energy of normal heated air. Performing the calculation for the heat energy of heated air in a convection oven at 230°C results in 35 kcal/m³—far less heat energy than the spiral oven with super-heated steam.

Finally, by subtracting the two, we can compare the two cooking environments to see how much more heat energy with which the spiral oven cooks. Subtracting the 35 kcal/m³ of the convection oven’s heated air from the 298 kcal/m³ of the spiral oven’s super-heated vapor results in 263 kcal/m³ more heat energy in the spiral oven.

The spiral oven cooking process today offers more than a footprint advantage over linear ovens. Today’s advanced spiral cooking technology leverages the advantages of its more efficient box-shaped design for heat transfer together with super-heated steam to maximize product yield and capacity. The super-heated steam delivered directly at the heat source dramatically increases the available heat energy in the oven enclosure. This approach is like “super-charging” an engine that allows the production rate to speed up and the product yield to be optimized.

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