Hydrogen response temperature profile

Electromagnetic flowmeters offer the advantage of no moving parts in the flow stream, possible two-phase fluid capability, direct mass flow measurement, good time response, and linear calibration. For reproducible results, the flow velocity profile must be symmetric with respect to the axis of the pipe. Problems with this flowmeter include zero point drift with temperature, complex electronics, and difficulty in maintaining a hydrogen leak-proof flow tube. 

Figure 11.4 shows the evolution of the hydrogen volume and differential temperature versus time upon four successive additions of NaBH4 solution (Fig. 11.4a, b). The curves of the amounts of evolved hydrogen (Fig. 11.4a) for each addition show similar profiles, with a kinetic response that slightly decreases with each successive addition as the concentration of metaborate and the total volume of the reactant solution increase. In fact, the presence of residual sodium metaborate... 

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