The flow rate of the stream which is uncontrollable is called the wild stream. In certain cases, the control of one stream could be difficult and in that case, the flow would be measured and after that, the flow rate of the other stream will be controlled. Ratio control would keep the flow of two or more streams at a constant ratio. It would set the relative amount, of components in the blending operations.It would maintain the fuel-air ratio of the furnace at the optimum value.It would keep a specified reflux ratio for the distillation column.Maintaining the required ratio of reactants to a reactor.The ratio factor would be set by a ratio relay or multiplying unit and this would be located between the flow transmitter and the flow controller setpoint, as we can see in the below image.įlow B is controlled to the preset ratio of flow A What are the major functions of the Ratio Control? In this type of control, an uncontrolled flow would determine the second flow, so that we can maintain the desired ratio between them. So by using this type of control we can make sure that the two or more flows (mixed flow) are kept at the same ratio even there are flow variations. Mostly the process variable which is to be controlled would be flow rate, manipulated variable, and also a disturbance variable. Basically, this is a type of feed-forward control where two disturbances are measured and held in a constant ratio to each other. The purpose of the Ratio control is to maintain the ratio of the two-process variable at a specified value. Ratio control can be defined as a type of feedforward control and it is widely used in the process industries. What are the applications of Ratio Control?.What are the disadvantages of Ratio Control?.What are the advantages of Ratio Control?.How can we do the Ratio Control of gaseous material?.What is the difference between Feed Forward and Ratio Control?.
#CIRCULATED WATER DRIFT RATIO CONTROL SERIES#
What is Series and Parallel Ratio Control?.What are the major functions of the Ratio Control?.(Note: Draw-off and blowdown are synonymous. In some large power plants, the cooling tower concentration cycles may be much higher. W = about 0.01 percent or less of C if the cooling tower has windage drift eliminatorsĬoncentration cycles in petroleum refinery cooling towers usually range from 3 to 7. W = 0.1 to 0.3 percent of C for an induced draft cooling tower W = 0.3 to 1.0 percent of C for a natural draft cooling tower Windage losses (W), in the absence of manufacturer's data, may be assumed to be: ΔT = water temperature difference from tower top to tower bottom, in ☌Ĭ p = specific heat of water = 4.184 kJ / kg / ☌ H V = latent heat of vaporization of water = ca. X C / X M = Cycles = M / (D + W) = M / (M û E) = 1 + įrom a simplified heat balance around the cooling tower: M (X M) = D (X C) + W (X C) = X C (D + W) Since the evaporated water (E) has no salts, a chloride balance around the system is: X C = Concentration of chlorides in circulating water (C), in ppmwĬycles = Cycles of concentration = X C / X MĪ water balance around the entire system is: X M = Concentration of chlorides in make-up water (M), in ppmw X = Concentration in ppmw (of any completely soluble salts à usually chlorides) Here are the governing relationships for the makeup flow rate, the evaporation and windage losses, the draw-off rate, and the concentration cycles in an evaporative cooling tower system:
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