Patent GB-927643-A (GB)
Title: Regulation of the outlet temperatures of media flowing through heat exchangers
IPC: F22G5/20
Filed: 1960-09-05
Abstract: 927,643. Fluid-pressure servomotor control systems. SULZER FRERES S.A. Sept. 5, 1960 [Sept. 16, 1959], No. 30572/60. Class 135. [Also in Group XIII] The outlet temperatures of two media flowing through an exchanger 17, Fig. 1, are regulated by varying the mass flow of one of the media in dependence on the outlet temperature of one of the media and varying the inlet temperature of the same or the other medium participating in the heat-exchange, in dependence on the outlet temperature of one of the media, in such a manner that when a change occurs in the outlet temperature of one of the media, the mass flow and the inlet temperature are acted upon in the same sense, and when a change occurs in the outlet temperature of the other medium, the mass flow and the inlet temperature are acted upon in opposite senses. The exchanger supplies a reheat superheater 15 of a steam turbine 16, 18 and is supplied by the superheater 12 of a steam generator. A feedwater injector 23 and a steam by-pass valve 22 control the temperature and the mass flow, respectively, of the heat-donating medium which passes through further superheaters 13, 14 after it leaves the exchanger 17. The by-pass valve 22 and a valve 27 controlling the flow of water to the injector 23 are connected by links 29, 30 and a lever 33 to a servomotor 35 controlled by a temperature-responsive device 40 at the outlet of the reheat superheater 15. When the temperature rises both valves 22 and 27 are opened to reduce the temperature and the quantity of steam entering the exchanger 17. A second temperature-responsive device 41 at the outlet of the superheater 14 controls a valve 28 supplying a feed-water injector 24 while a third such device 39 at the inlet to the superheater 13 controls a second servomotor 38 connected to the lever 33 which is rotated in response to a rise in temperature to open valve 27 and close valve 22. The steam generator also includes an evaporator 10, feedwater preheaters 4 to 8, a feed-water tank 9, condensate pumps 2, 3, a condenser 19 and a water separator 11. Fig. 2 shows a system similar to part of Fig. 1 in more detail. A temperature-responsive device 120 comprising a rod with a low co-efficient of expansion fitted to the steam pipe acts through a spring 200 on a control valve 121 which causes a relay valve 137 to operate the water injection valve 118 and a steam by-pass valve 113 for the exchanger 108 in the same sense. Actuation of the valve 121 also displaces a piston valve 126 to maintain a steadily rising pressure on the valve 137 until the temperature is restored to its preselected value which may be adjusted by a manually-operated valve 132. A second temperature responsive device 122 causes a second relay valve 152 to operate the valves 113 and 118 in opposite senses. The relay valve 152 is also connected to a pilot valve 157 coupled to a valve 119 for a feed-water injector 115 and through a regulator 164 to a third temperatureresponsive device 163. A by-pass valve having an actuating piston with opposite sides connected to the relay valves 137 and 152 may be connected between the lines 107 and 111.