The present invention relates to a structure for controlling a temperature of hot-water supply from a waste heat recovery system, and more particularly, to a structure for controlling a temperature of hot-water supply from a waste heat recovery system using a three-way valve capable of stably supplying hot water at a hot-water supply setting temperature during hot-water supply use using the three-way valve and saving energy to improve system efficiency, in a waste heat recovery system recycling waste heat.

Systems and methods for providing override control for a feedwater pump recirculation valve 140 are provided. According to one embodiment, a system may include a controller 600 and a processor communicatively coupled to the controller 600. The processor may be configured to receive one or more measurements associated with pump motor power driving feedwater pump flow. The feedwater pump recirculation valve 140 may be configured to maintain a predetermined minimum recirculation flowthrough the feedwater pump 105 by regulating recirculation pump flow through a recirculation line. The processor may be also configured to calculate, based at least in part on the one or more measurements, the recirculation pump flow, and compare the recirculation pump flow to the predetermined minimum recirculation flow. Based at least in part on the comparing, the processor may selectively provide an override control signal to the feedwater pump recirculation valve 140 to selectively modify the recirculation pump flow.

A steam-raising system comprising a boiler (42) having (a) a passageway (86) for water and/or steam, (b) an inlet (40) to the passageway (86) through which water is introduced continuously for given periods when the boiler (42) is in use, (c) a burner (88) to heat the passageway (86) from the outside thereof, and (d) an outlet (44) from the passageway (86) from which steam emerges continuously as water is introduced through the inlet (40). The system further comprises a pump (32) connected by a flow-path (38) to the said inlet (40) to pump water thereto along the said flow-path (38). The pump (32) is a variable-flow-rate pump (32) constructed to provide a flow-rate through it which is substantially independent of its downstream pressure.

A steam-raising system comprising a boiler (42) . The boiler (42) has (a) a passageway (86) for water and/or steam, (b) an inlet (40) to the passageway (86) through which water is introduced continuously for given periods when the boiler (42) is in use, (c) a heater (88) to heat the passageway (86), and (d) an outlet (44) from the passageway (86) from which steam emerges continuously as water is introduced through the inlet (40) . The system further comprises a pump (14) connected by a flow-path (18, 20, 22, 32, 34, 36, 38) to the said inlet (40) to pump water thereto along the said flow-path (18, 20, 22, 32, 34, 36, 38), and flow-control means (32, 34, 36, 64, 66, 68, 76, 78, 80) in the said flow-path (18, 20, 22, 32, 34, 36, 38). The flow-control means (32, 34, 36, 64, 66, 68, 76, 78, 80) comprise a plurality of lines (32, 34, 36) which constitute a part of the flow-path (18, 20, 22, 32, 34, 36, 38), which are connected between the pump (14) and boiler (42) in parallel with one another, and which are independently openable to enable the amount of water delivered to the boiler (42) to be varied.

©7 An emergency feedwater system for the steam generators (S) of a pressurized water nuclear reactor has two separately located subsystems (A, B), each subsystem supplying water to at least one steam generator (S) when activated, where each subsystem contains an emergency feedwater supply tank (11), and a pair of emergency feedwater lines (15, 17) leading from the tank (11) and communicating with the inlet line (5) of a steam generator (S). An electrically operated motor driven pump (23) is located in one (15) of said pair of emergency feedwater lines (15, 17) and a steam turbine driven pump (27) in the other (17) of said pair (15, 17), with cavitating venturies (25, 33) provided in the emergency feedwater lines between the pumps (23, 27) and inlet lines (5) of the steam generators (S).

A system for controlling the feedwater system in a nuclear power plant utilises a logic calculations subsystem (50) which selects an operational mode of the system to be monitored from a plurality of operational modes. A disturbance estimate calculations subsystem (52) contains a dynamic mathematic model of the feedwater system and compares measured system variables with corresponding dynamic model variables contained therein to produce signals representative of deviations therebetween. A modified feedforward calculations subsystem (54) utilises these signals and other system parameters as inputs to a steady-state mathematical model to produce control signals to determine valve positions and pump speeds so that the control valve flows, minimum control valve pressure drop, and feedwater pump flows are at their respective demanded values.