UVX digital radiometer

The evaluation of photocatalytic reactor performance is closely related to the continuous evaluation and reassessment of lamp operation since lamps experience decay with time of utilization. It is recommended that lamps be calibrated and re-recalibrated frequently to estimate their decay. In addition, it is advised to use some auxiliary equipment in perfonning this task (a) a UVX digital radiometer, (b) a 4D Controls Ltd spectrora-diometer, (c) the Lamp Testing Unit (LTU) developed by Serrano and de Lasa (1997), and (d) a set of tubulai collimators for radiation ti ansmission measurements. 

FIGURE 3.1. Spectral Response of the UVX-36 Sensor Cell. (Reprinted with permission of M. Salaices, PhD Dissertation, University of Western Ontario 2002). 

When measm ing intensities for a phosphor-coated lamp, a correction factor is needed to obtain the true absolute reading. A coiTection factor can be calculated using the following relationship. 

Alternatively, a 4D Controls Ltd spectroradiometer can be used for the measurement of both spectrometric fluxes and total radiation fluxes in the range of 10 to 50 W cm nm. This instrument covers a spectrum from low UVC (235 nm) up to the beginning of the visible blue light (470 nm), with a 0.5-nm-width spectral sampling. 

FIGURE 3.2. Typical BL lamp radiative flux axial distribution at 3.1 cm from the reactor axis. (Reprinted with permission from Ind. Eng. Chein. Res., 40(23), M. Salaices, B. Serrano and H.I. de Lasa, Photocatalytic conversion of organic pollutants Extinction coefiicients and quantum efficiencies, 5455-5464. Copyright 2001 American Chemical Society). 

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Figure 3.2 reports typical radiative flux axial distributions in mW cm for a black-light lamp (BL). The values were obtained using a UVX digital radiometer at 3.1 cm from the reactor axis. 

A 15-W black-Iight-blue lamp (BLB) with emission in the 300-4I0-nm wavelength range is used as radiation source. The initial emission of this lamp is assessed at 1.03. 10 einstein/s (3.5 W) using a 4D Controls Ltd spectroradiometer and a UVX digital radiometer (Salaices et ai, 2001). The initial total energy absorbed into the system is estimated at 2.66 W. This parameter can be connected as needed, taking into account the lamp irradiation decay. 

All processes of irradiation were carried out using a illuminator Cole Palmer 41720-series keeping a distance of 10 cm between the lamp surface and the solution, varying the time periods of exposure at 25 °C under continuous shaking, with a emission maximum in UVA-Vis 320 00 nm (3.3 mW/cm, 45-575 Lux/ seg) (radiation dose 4.5 J/cm ) as measured with a model of UVX Digital Radiometer after 1 h continued illumination. 

The LTU consists of a UV-opaque chamber, a lamp holder and a sensor holder rail. A schematic representation of the LTU with one digital UVX radiometer is presented in Figure 3.4. The near-UV lamp (365 nm peak) is placed in the lamp holder at a set distance fi om the detector. The LTU is designed to be flexible in accommodating different detectors. 

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