Dynamic response, of pressure

Thus, the dynamic response of pressure is slowed down by both the thermal capacitance of the condenser and the rigorous handling of heat transfer in the reboiler. 

This chapter describes the dynamic response of pressure vessel columns and stacks. We will focus on screening criteria and methods of remediation and follow with a discussion on methodology. 

The dynamic response of most transmitters is usually much faster than the process and the control valves. Consequently we can normally consider the transmitter as a simple gain (a step change in the input to the transmitter gives an instantaneous step change in the output). The gain of the pressure transmitter considered above would be... 

Fuel supply is usually from liquid hydrogen or pressurized gaseous hydrogen. For other fuels, a fuel processor is needed, which includes a reformer, water gas shift reactors and purification reactors, in order to decrease the amount of CO to an acceptable level (below a few tens of ppm), which would otherwise poison the platinum-based catalysts. This equipment is still heavy and bulky and limits the dynamic response of the fuel cell stack, particularly for the electric vehicle in some urban driving cycles. 

Figure 2.134 illustrates how the dynamic response of the control system is maintained. Here, the pressure controller (PC) provides the sensitivity required for quick response, while the flow controller (FC) keeps the flow in the bypass line at a minimum, as it slowly opens the HPS supply valve to the turbine whenever the flow in the bypass line exceeds its set point. 

The temperature dependence of the actual oxidation state of the Ru(0001) surface raises the question of whether only the Ru02 phase is catalytically active. To confirm or correct the suggested mechanism of CO oxidation on a ruthenium catalyst, the evolution of the oxidation state of the catalyst with reaction temperature and the C02 production at CO + 02 pressures comparable to those of realistic catalytic conditions were followed simultaneously. The dynamic response of the Ols and Ru3d5/2 core level spectra was used for a precise assignment of the state of oxidation of the catalyst in the course of the reaction—correlated to the corresponding C02 yields measured with a mass spectrometer. The already determined Ru3d5/2 and Ols core-level spectra summarized in Figure 26 provided the necessary basis for identification of the adsorbed, "incorporated," and oxide states and verification of their roles in the CO oxidation reaction. 

Measuring device. This can be a variable capacitance differential pressure transducer (Section 13.3), measuring the pressure of a liquid column of height h. The dynamic response of the sensor is given by eq. (13.9). Let Ap = ah, where a is a constant. Then take... 

The dynamic response of the vapor inlet control scheme is far superior to that of the condensate outlet scheme. Manipulating the inlet valve immediately changes the vapor flow. Reboiler pressure and heat transfer rate only lag a few seconds behind. On the other hand, the condensate outlet valve has no direct effect on vapor flow. Condensate flow determines condensate level, and this level changes slowly. Reboiler vapor rate and heat transfer tread on the heels of the level change. Because of this slow response, manipulating vapor flow is a far better means of control than manipulating condensate flow. 

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