The perception of room brightness over photopic luminances ranging from 30 cd/m2 to 67 cd/m2 was judged by 12 subjects in an almost uniformly white experimental chamber. Two different illuminants were compared which had different spectral compositions, but were color matched. Brightness judgements were often opposite to large differences in photopic luminance. These results are inconsistent with models of brightness perception that depend solely on cone receptors. At the luminance levels considered here subjective evaluation of light intensity depends upon both photopic and scotopic spectral contributions. These results imply that aspects of the visual system operate mesopically under most interior lighting conditions.
Subjects judged the orientation of a 2 min. gap Landolt C located at a distance of 2.4 m. The stimuli were presented in central vision on a CRT, at low to medium contrast. The effects of varying the spectrum and luminance of surround lighting were assessed on both pupil size (measured using infrared pupillometry during task performance) and task accuracy. The task display was protected from the surround lighting, so that its luminance and contrast could be varied independently of the changes in the surround lighting. Indirect surround illumination was provided by . either two illuminants of very different scotopic spectral content but with the same · photopic luminance (Experiment 1 and 3 each), or by using the same illuminant at two different luminance levels (Experiment 2). In experiment 3, the effect of changing surround spectrum was compared to the effect of varying task background luminance between 12 cd/m2 and 73 cdfm2. In all experiments, scotopically enhanced surround lighting produced pupil areas which were reduced by almost 50% in comparison with surround lighting with relatively less scotopic luminance.Concomitantly there was improvement in Landolt C task performance with the scotopically enhanced surround lighting at all contrast and luminance levels. In these experiments, smaller pupil sizes were associated with significantly better visual-task performance in spite of lower task retinal illuminance when compared to the condition with larger pupils. These results suggest that changes in surround spectrum can compensate for the effect on task performance of a reduction in task luminance and supports the possibility that lighting energy savings can accrue in the workplace by shifting lamp spectra to obtain greater scotopic efficacy.
A new relationship describing dynamic multiphase orifice pressure drops and fluid flow capacities has been derived and tested with field data. The mathematical model relates dynamic orifice behavior in both critical and noncritical flow regions. Correlations are presented for predicting the ultimate (critical) capacity of an presented for predicting the ultimate (critical) capacity of an orifice for any given set of dynamic conditions. Introduction A new relationship describing dynamic, multiphase orifice pressure drops and fluid flow capacities has been derived and tested with actual field data. The mathematical model relates dynamic orifice behavior in both critical and noncritical flow regimes. Orifice pressure drops and capacities are related to pertinent fluid properties and choke dimensions. Graphical pertinent fluid properties and choke dimensions. Graphical correlations are also presented to predict the ultimate (critical) capacity of an orifice for any given set of dynamic conditions. To verify the model, a field test was designed and carried out in a flowing oil well. Both orifice pressure drops and fluid flow rates were measured in the well and the information was compared with analogous data predicted by the model. Comparable information was then predicted by the model. Comparable information was then used to compute an "orifice discharge coefficient" that enables calculation of actual orifice capacities from theoretical ones. The discharge coefficients are presented for 14/64-, 16/64- and 20/64-in. orifice diameters. The collected data reflect the behavior of an Otis Engineering Corp. J-type 22J037 safety valve. However, the model may be used to estimate multiphase pressure drops through restrictive beans in safety valves of other internal geometrical configurations. Discussion The increased need for more accurate settings on downhole, self-contained, flowing safety devices (storm chokes) has prompted efforts by many oil-producing companies to develop new multiphase orifice flow relationships. Interest in antipollution devices, especially in offshore oil-producing areas, has also encouraged the major oil companies to re-evaluate old, established procedures for the design of oil- and gas-well safety procedures for the design of oil- and gas-well safety valves. A review of the existing orifice flow literature and analysis of standard safety-valve design procedures yielded the following facts concerning noncritical multiphase orifice flow.Most orifice flow models do not adequately reflect the compressible nature of actual oilwell multiphase orifice flow. Consequently, models now in use do not adequately describe the dynamic behavior of orifice flow.The existing orifice flow relationships become less exact as the dynamic conditions approach the critical value; that is, at a given upstream pressure, no further flow-rate increase occurs through the orifice, regardless of the pressure drop across the orifice. Those who are involved in manufacturing down-hole, pressure-drop-operated safety valves are aware of the pressure-drop-operated safety valves are aware of the problems associated with accurate prediction of orifice problems associated with accurate prediction of orifice flow behavior. Most agree that a more rigorous mathematical model is needed to describe the mechanics of orifice flow under all oilfield conditions. The orifice relationships used by design engineers, though acceptable under certain flow conditions, are questionable for applications falling outside these specifications. A more rigorous procedure applicable to oilfield JPT P. 1145
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