Feedback control optimization of a single fluid heat exchanger or nuclear reactor

• Published in: Nuclear engineering and design 1968, Vol.7 (1), p.40-48
• Main Authors: Watts, R.G., Schoenhals, R.J.
• Format: Article
• Language: English
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/0029-5493(68)90125-8

The performance of a single fluid heat exchanger is analyzed under conditions of proportional control of heat flux. The error is obtained from a single temperature probe whose axial location can be varied. The usual procedure is to place the probe at the outlet and to select the best proportional gain constant for this situation. However, results of this study show that simultaneous optimization of gain constant and axial probe location can produce large improvements in system performance. For purposes of illustration, quantitative results are given for the case of variable inlet temperature whose spectral power density is constant up to a high frequency limit, and is zero beyond this limiting value. A physical argument is suggested which relates optimum probe location to a single parameter defined in terms of system time constants. Many nuclear reactor systems can be regarded as single fluid heat exchangers for purposes of calculating outlet temperature dynamics, since the heat generation rate usually responds a great deal faster than the fluid temperature when a control rod position is changed. The general method outlined is also applicable to boiling water reactors in which the outlet void fraction rather than the outlet temperature is the controlled variable.