Fundamentals
FLAME BASED HEATING:
In order for heat to be generated by a flame-based process, the fuel molecules and oxygen molecules in the air must collide with sufficient kinetic energy (molecular speed) to overcome an energy barrier that normally keeps the molecules from reacting (i.e. exothermic reaction product) and releasing heat. The high energy barrier requires a high flame temperature (> 1000°C) to sustain the reaction, as well as, to start it (match, spark, etc).
CATALYTICALLY BASED HEATING:
Coolfire® technology employs a catalyst within the reaction zone to produce a flame free, low temperature ( < 260°C) heat reaction. The basic principle of operation is that the catalyst lowers the energy barrier between the fuel molecules and the oxygen molecules so that they may combine at a much lower temperature. The catalyst is not consumed in the reaction. Instead, it acts as a kind of “broker” to insure that the molecules combine at a much lower temperature than normally be required. It then proceeds to perform this function in a continuous manner as new, unreacted fuel and oxygen, enter the reaction zone. Although catalytic heating is not a new concept, the Coolfire® approach is a unique and patented method of optimizing catalytic heating for a wide variety of portable heating applications including beverage and food heating applications. In stark contrast, conventional catalytic heating has many of the same problems and limitations as flame based heating.
Startup, Control and Emissions:
FLAME BASED HEATING:
The kinetic energy required to start the reaction is generally supplied in the form of a high energy mechanism (match, spark, etc) or process of some sort to produce a temperature above the autoignition point. Automated starting of flame based products depend on spark based mechanisms. Portable products, that utilize a spark starting approach, universally depend on a manually switched piezoelectric component. Piezoelectric starters are prone to damage and tend to have high failure rates, are cumbersome to operate (high starting force manually applied ) and relatively noisy. Once started, the heat power is controlled by manually adjusting a flow valve (e.g. needle valve).
When a high temperature flame contacts a much cooler cooking utensil surface, an unsteady boundary layer is formed at the surface. The gases within the boundary layer transfer their heat energy to the cooking utensil causing some of the fuel/air mixture within this layer to drop below a critical temperature. This can prevent some of the fuel/air mixture constituents within the flame from completing combustion . Consequently, incomplete combustion products often form which include the toxic emission of carbon monoxide.
CATALYTICALLY BASED HEATING:
Coolfire® technology does not require a flame or spark to start the reaction. Instead, a micro-miniature, electrically driven (joule heating) resistance coil is embedded within the catalytic media and raises the local temperature to a point (well below the autoignition point) where the reaction begins. The reaction then spreads rapidly throughout the reaction chamber, allowing completion of the heat generating fuel/air reaction without noxious by-products (i.e. no CO or NOx ). Unlike portable open flame products, the starting process for Coolfire® catalytic technology is completely automated, noise free and requires a very low energy draw ( 0.5 W-sec) per start. Heat power is controlled by built-in sensors and a set of microcontroller algorithms.
Combustion Stability:
FLAME BASED HEATING:
Naked flames can only be sustained by a careful balance between flame propagation speed (which is determined by fuel type and fuel/air ratios) and the rate at which the raw fuel/air feed enters the reaction zone. Because of the need to balance these and other parameters within a narrow range of settings, flames may be thought of as essentially borderline stable. This tendency toward instability (i.e. flame out condition) also makes them susceptible to being extinguished by wind currents that interrupt this balancing act.
In addition, flame based products have other restraints, such as being sensitive to physical orientation of the product (i.e. the flame is always vertical), so it is necessary to provide (a reasonable degree) of product leveling to insure proper heat transfer and optimum performance. Another limiting factor for flame based products is that fuel/air mixtures must be within a relatively narrow operating range. If the mixture is too lean or too rich, flame ignition becomes unreliable.
CATALYTICALLY BASED HEATING:
Coolfire® catalytic technology avoids most of the limitations of flame based heat sources. The reaction cannot be extinguished by wind effects and is not susceptible to flame lift-off or flash-back effects. Moreover, our patented catalytically driven combustion technique runs at temperature below the ignition point of most materials encountered in daily life. In addition, it operates over a very wide range of fuel/air ratios not achievable with flame combustion. It is also not dependent on product orientation, which makes it safe and convenient to operate while walking, hiking, or traveling in a vehicle. Because of this and other properties, Coolfire® accommodates a much wider design space resulting in more desirable product attributes.
Fire Safety and Heat Transfer:
FLAME BASED HEATING:
Because of their high temperature, (typically above 1000 °C) and the lack of a flame isolating envelope, flame based portable heaters present a serious fire hazard if knocked over or placed too close to flammable material. The lack of a flame isolating envelope also contributes to safety issues during the starting process. For instance, inexperienced or inattentive users, who inadvertently let the unignited fuel/air mixture build up too much before manually igniting the flame, may see a sudden and unexpected back flash that propagates out of the air vents, exposing the user to potential harm.
The high temperatures common in flame based heating tends to cause a high degree of local turbulence as a result of flame zone buoyancy. The turbulence can adversely affect heat transfer, limiting overall efficiency.
CATALYTICALLY BASED HEATING:
Coolfire® catalytic technology produces a reaction that runs at an average temperature of about 260°C, which is well below flame based heat sources. The Coolfire® catalytic heat generating technology is completely enclosed within a porous, open cell, metal foam structure. The resulting effect is that the boundary layer at the cooking utensil surface, is laminar. This allows a more uniform heat transfer to occur which increases overall efficiency and eliminates local hot spots.
In addition, the metal foam, in which the catalytic reaction is maintained, has geometric properties that cause it to behave as a flame arrestor, further limiting the potential for any kind of flame formation or propagation.