Cooling - uv-technik international ltd. uv lamps, uv units and uv equipment

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Cooling

The volume of cooling air required depends on the power of the UV lamp and is usually extracted from the top or end of the reflector unit. In special cases, the cooling air can also enter through the same route and be blown over the UV lamp. However, this involves the risk of the UV lamp being cooled down too much
at certain places (e.g. jet effect due to ventilation slots, air vortices).
Therefore, a trial run is necessary before starting this kind of operation.

The values shown in the table below can be taken as guide values for the cooling air volume. They have to be multiplied by the electrical lamp power
in kW.

Reflector Units Cooling
Lamp power	40 to 60 W/cm	70 to 90 W/cm	100 to 130 W/cm	140 to 180 W/cm	200 to 240 W/cm
Air volume	30 m³/h * kW	40 m³/h * kW	50 m³/h * kW	65 m³/h * kW	90 m³/h * kW
Approx. 80 to 100% must be added for the cooling of the surrounding case provided by the customer.

Example: Electrical power 6 kW at 120 W/cm
Required cooling air volume for the reflector unit: approx. 300 m³/h
Additional cooling air volume for the protective housing: approx. 270 m³/h
The total exhaust air volume is approx. 600 m³/h.

We know from general experience that an exhaust air temperature of 60 °C, measured near the air outlet of the dryer, indicates sufficient cooling. If the temperature of the exhaust air is below 40 °C, the lamps may perhaps be cooled down too much (not necessarily, though).

In stand-by operation, with reduced power, the cooling air volume usually needs to be reduced in order not to supercool the UV lamp. As the degree of air reduction is, among other things, also dependent on the actual operating conditions, the exact amount must be determined in a trial. The air volume can be reduced by e.g. a motor-driven throttle valve, a two-stage fan or a continuously variable fan (with frequency inverter). Generally, if the arc voltage of the lamp is too low in the long run, this indicates excessive cooling of the lamp (operating voltage less than approx. 75 - 80% of the rated voltage).

Please note that in stand-by operation, the required air volume is significantly different depending on whether the shutters are open or closed. In the case that the shutters are open, the calculation shown above can be used. However, if the shutters are closed, a significantly larger air flow is necessary in order to sufficiently cool the shutters that are heated up due to the proximity of the lamp. Under certain conditions, the required air volume can be the same as the amount that is needed for full-load operation. However,
the lamp will not cool down too much as it is protected by the closed shutters. The exact setting of the air volume must be determined by experimentation during the commissioning. Monitoring the lamp voltage (see previous paragraph) will prove helpful. The profile temperature should not exceed 300 °C. Due to its ozone content, the exhaust air must be discharged to the outside through the roof. Thanks to the relatively high temperature of the exhaust air, the ozone decomposes rapidly.