Bells method

In Bell s method the heat-transfer coefficient and pressure drop are estimated from correlations for flow over ideal tube-banks, and the effects of leakage, bypassing and flow in the window zone are allowed for by applying correction factors. 

This approach will give more satisfactory predictions of the heat-transfer coefficient and pressure drop than Kern s method and, as it takes into account the effects of leakage and bypassing, can be used to investigate the effects of constructional tolerances and the use of sealing strips. The procedure in a simplified and modified form to that given by Bell (1963), is outlined below. 

The method is not recommended when the by-pass flow area is greater than 30% of the cross-flow area, unless sealing strips are used. 

The shell-side heat transfer coefficient is given by  

Fn = correction factor to allow for the effect of the number of vertical tube rows, Fw = window effect correction factor, 

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Glocken-giesser, m. bell founder, -gut, -metall, n., -speise, /. bell metal, -trichter, m. bell fimnel (as on a thistle tube), -verfahren, n. bell process, bell method, -wischer, m. bell-type scrubber. 

The design calculations highlighted the shortcomings of the Kern method of exchanger design. The Kern method fails to account for shell-side inefficiencies such as bypassing, leakage, crossflow losses, and window losses. This leads to a marked overestimate of the shell-side heat-transfer coefficient and shell-side pressure drop. The Bell method is recommended to correct these deficiencies. 

The Kern method is inaccurate for calculating the shell-side heat-transfer coefficient and shell-side pressure drop (Ref. E2, p. 545). Kern makes no account of the effect of bypss and leakage in the shell-fluid passage. For these reasons the Bell Method (Ref. E9) is employed to serve as a check on the preliminary design. 

If this 33% reduction in the overall heat-transfer coefficient and the 90% reduction in pressure drop had not been discovered, this would have caused a significant underestimate in the design to occur. This example should therefore serve to highlight the need for a more rigorous design approach to shell-side evaluation than that proposed by Kern. The Bell method proved quite adequate in this regard. 

H.9 Shell-side Heat-transfer Coefficient (The Bell Method) 318 H.10 New Overall Heat-Transfer Coefficient (The Bell... 

H.11 New Shell-side Pressure Drop (The Bell Method) 321... 

The shell-side pressure drop must be recalculated using the Bell method, i.e. accounting for the various losses previously mentioned. 

Mass spectrometer Boiling Point Torsion-effusion Torsion-effusion "Bell" method (total vapor pressures)... 

Dyno has contributed to the development of a method, named the Bell method, for the quantitative determination of the formaldehyde emission from a panel surface ( 5). A glass flask or bell having a plane flange is placed on the surface to be measured. A tight sealing between the flange of the bell and the panel surface is very important. The air can be kept in circulation by means of a membrane pump, pumping about 2 liters per minute in a closed loop, which also contains a gas burette. After a predetermined time the formaldehyde concentration of the air in the gas burette is determined by a sensitive analytical method. 

The Bell method can be used to determine the equilibrium concentration of formaldehyde, C in the model above. When the formaldehyde concentration in the Bell system is plotted against time, the initial slope of the resulting curve can be used to determine the mass transfer coefficient, kg in the same model. 

Thus, although there is no air exchange between the glass bell and the surroundings, the Bell method can be used to provide data to calculate the steady state concentration in a ventilated system. 

The project plan involved the use of the Bell method to determine the equilibrium concentration and mass transfer coefficient for a number of particleboard samples with different surface finishes and overlays. 

Bell method, formaldehyde emission from a panel surface, 205... 

The sine-bell method multiplies the FID by half a sine cycle using the function sin (nt/T) where T is the acquisition time of the FID. There are no adjustable parameters, although a variant technique, a shifted sine-bell using the function [43]... 

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