GB807288A - Improvements in fluid heating systems - Google Patents

Abstract

807,288. Automatic temperature control systems. FOSTER WHEELER Ltd. Nov. 21, 1956 [Nov. 21, 1955], No. 35596/56. Class 38 (4). [Also in Groups XIII and XXVI] In a heat exchanger 60 in which air flowing through tubes 73 to an outlet 76 is heated by a heat transfer liquid such as sodium potassium surrounding the tubes, the air temperature at the outlet 76 is maintained at a predetermined value by adjusting the liquid level of the heat transfer liquid in the heat exchanger. This adjustment is effected by regulating the speed and direction of a pump 115 which acts to either supply or withdraw the heat transfer liquid to or from the heat exchanger as necessary. If e.g. the air temperature in conduit 76 is below the desired value an air temperature sensing element 88 in the conduit 76 actuates a valve 91 in a pneumatic control line 92 to vary the pressure downstream of the valve and hence actuate a bellows 93 movement of which displaces one end of a link 95 upwardly thereby moving a core 103 away from a secondary winding 108 of a transformer 104. Consequently a signal of one phase is induced in the secondary windings and is then amplified by amplifier 109 and fed to variable-phase winding 111 whereby a motor 112 driving the pump 115 is rotated in a direction to feed heat transfer liquid from a surge tank 81 into the heat exchanger shell 65. The consequent rise in the liquid level in the heat exchanger shell changes the relative pressures in bellows 98, 99 (communicating respectively with the shell space above and below the liquid level therein), and thus causes movement of link 96 in a clockwise direction, which movement is imparted to link 95 as a counterclockwise motion tending to displace core 103 to a central position between the transformer windings 107, 108 so that the signals from the transformer windings cancel out and therefore motor 112 and pump 115 are stopped. Conversely when the air temperature in conduit 76 is above the desired value the temperature sensing element 88 acts to move the core 103 away from the secondary winding 107 of the transformer thereby rotating the pump 115 in the opposite direction to withdraw heat transfer liquid from the shell 65 until such time as the pump is stopped by restoration of the balance of pressures in bellows 98, 99. The heat transfer liquid in heat exchanger 60 receives its heat from further tubes 63 in which liquid sodium circulates, the heating circuit including a sodium heater 12 and a unidirectional variable-speed pump 124, the speed of the pump being varied through a control device 122 regulated by a temperature sensing element 116 in the sodium circuit located at the sodium outlet from the tubes 63 of the heat exchanger. Fuel supply through conduit 45 to the heater 12 is regulated in accordance with the temperature of the sodium flowing from the heater to the tubes 63.