Bestimmung der persönlichen Formaldehydbelastung

The free recovery of wall-stabilised arcs with imposed laminar and turbulent flows

“…The results also show that the plasma-probe resistance substantially increases with mass flow rate and time into the free recovery period. For small flow rates at least, the slower decay of the probe characteristics observed for the larger bore (5 inm radius) arcs, compared with those for the smaller bore, is consistent with arc decay in the absence of flow (Frind 1960). The greater plasma-probe boundary resistances for the larger bore arcs at high flow rates should still enable reliable differential voltage measurements to be made, since it is still possible to draw 5-10 mA current to the probes, hence maintaining a positive probe bias.…”

“…For the entrainment arc region, the present analytical model predicts that a 10% reduction in arc radius should produce about a 46 % reduction in arc time constant due to flow effects, compared to a reduction of 20% in arc time constant in the absence of flow (Frind 1960).…”

“…The results are shown normalised with respect to arc current (Z/rw) and mass flux (uit/rw2). For the lower mass flux (4.8 x g mm-2 s-l), the initial arc decay time constants scale with the square of the bore radius in a similar maimer to zero flow conditions (Frind 1960). At greater mass fluxes, the initial decay time constants do not scale in this manner.…”

“…The effect of turbulence upon the free recovery of the fully developed region is embodied in the thermal time constant through the factor (1 + p) (equation 13). For laminar flows, the model reduces to Frind's (1960) ramp U-S model, where the decay time constants may be normalised with respect to stabilising tube area (figure 4). For turbulent flows, however, this normalisation is no longer valid since p is also a function of radius, leading to the time constant being independent of radius at higher flow rates.…”