Test results show that 1 kW of power permits a 15C temperature increase for a water flow of 1 liter/min. Applications? Hot Drinks Vending Machine, Restaurant coffee makers, Heating of ultra-pure water for semiconductor device manufacture; medical products; chemical processes, Space heating and Hot water equipment
Some companies have been investigating microwave heating of ultra-pure water for semiconductor device manufacture. Most techniques have been based on heating the fluid through the walls of PFA Teflon pipes. "The biggest problem preventing commercialization has been the cost of microwave generators of the sizes required for their applications- typically > 50kW. The microwave generators alone cost approximately four times what complete heaters, based on infrared or direct-contact means, are marketed for in the U.S.A." commented an American semiconductor equipment supplier. This problem remains in the other market segments.
For reasons of economy and conception, it is more advantageous to manufacture a modular system of 1 KW rather than 2, 4 or 6 KW ; thus added in series or in parallel these devices will increase the temperature or the flow of the liquid. For specific industrial applications these devices will be able to be totally autonomous and thus to constitute operational heating circuits.
In the case of a rectangular wave guide we can use for instance the 2.45 GHz frequency with standard dimensions WR 340 a = 86.36 mm and b = 43.18 mm, the wave guide length L being calculated. Let us consider a liquid slab of thickness e and height b placed at the center of the wave guide because the electric field is maximum at this place with the TE10 mode. If is the microwave amplitude attenuation in dB/m (decibel per meter), the power attenuation after a distance of L will be 2L then with the TE10 mode, [4], [7] :
2L = 7.35 (2L) e" dB " is the loss factor supposed temperature independent, e is in mm, L is in m. In the case of water " = 8.9 at 25°C, " = 6 at 40° C and " = 4.2 at 55°C
For L = 0.25 m and e = 1 mm we have with 1KW and 1 Litre/mn
For an inlet water at 25°C 2L > 22 dB the outlet temperature is 40°C For an inlet water at 40°C 2L > 15 dB the outlet temperature is 55°C
The corresponding volume is approximately 0.01 litre. For a best absorption at elevated temperature one can increase the pipe width e, for instance to 5 or 10 mm , the corresponding volume will be 0.05 or 0.1 litre respectively. In the termination the pipe width is increased from e to a in order to absorb the residual microwave power.
All the above is from Knol.com
Market Data 
Markets 
AI
