Importance

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Abstract

A supervisory computer automatically equalizes the temperature of effluent streams of a multipass heating system to maximize heat transfer, without substantially disturbing a desired total flow through the heating system. Temperature control is achieved by manipulating the division of a feed stream among the multiple passes. In addition, if the flow in one or more passes cannot be manipulated, the control scheme automatically equalizes the temperatures of the remaining passes. This is accomplished by calculating a flow rate for adjusting the flow through the number of passes under supervisory control to a value, which in addition with any uncontrolled flow, will provide the desired total flow through the heating system. This adjusted flow rate is used as an approximate set point for the flow rate in each controlled pass. The adjusted flow rate signal is modified for control of each individual pass by applyng a bias through a conventional controller acting on a weighted average temperature signal. This temperature biased signal is further modified by applying another bias through a gap controller acting on an average flow signal. The thus twice biased signal is provided as a flow rate set point for it's individual pass.

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First Claim