Comparison of infrared, flame and steam units for their use in plant protection
The energy performance of infrared, flame-weeder & hot-steam units for pest and weed management were evaluated and compared. These thermal units were tested for ease of installation, adjustment of operation, safety and reliability. The temperature development of these units was tested in a controlled environment. All three units used propane combustion as the main source of energy to provide heat. Type K, 0.5 mm thermocouples were used for measuring temperature. The three thermal units were passed over the thermocouples at groundspeeds of 1.5, 2.5 and 3.5 km/h. At a groundspeed of 1.5 km/h, the hot water-steam unit reached the lowest temperature, 43.6°C. The infrared radiation and open flame units developed temperatures of 620.9ºC and 186.1ºC respectively. The exposure time, fuel consumption, and energy input were calculated for each thermal unit. Propane consumption was one of the main factors causing the significant difference in temperatures. The infrared radiation unit developed the highest temperature, and it also had the highest propane consumption, 165.2 kg/ha at a groundspeed of 1.5 km/h. The hot water-steam and open flame units had propane consumptions of 24.5 and 29.8 kg/ha respectively. The hot water-steam unit was the safest of the thermal units because all of the flames were contained within the boiler. The hot water would not do any damage to the soil and it would not spread rapidly across the field. The infrared unit can cause the greatest fire hazard and it is recommended that some form of fire-extinguisher be present when this unit is in operation. The hot water-steam unit has the most potential in pest management, and the infrared radiation unit is most suitable for pre-emergence weed control. The open flame unit reached medium temperature among the thermal units. This thermal unit has the biggest potential in thermal weed and pest management. It is the easiest to use of these thermal units, and the design allows for both nonselective and selective techniques, which makes it the most adaptable for using in practical situations.