Method and apparatus for controlling a heat exchanger

Claim 2

Method of controlling a heat exchanger such as a forced-flow boiler or the like wherein slightly superheated steam is generated, comprising continuously determining the specific actual enthalpy (ii) of the slightly superheated steam, and utilizing the specific actual enthalpy as an auxiliary control quantity.

Claim 3

The method of claim 1 wherein the heat exchanger is supplied with the operating mediums of fuel and feedwater and is equipped with adjusting means for adjusting the flow of at least one of the operating mediums to the heat exchanger, comprising continuously measuring the actual pressure (pi) and actual temperature (Ti) of the slightly superheated steam in the heat exchanger, supplying the measured actual values of pressure (pi) and temperature (Ti) to a computation circuit for determining the control deviation (xwi) of the specific actual enthalpy (ii) from the reference value of the enthalpy (io), and supplying the control deviation (xwi) of the specific enthalpy as a correction quantity for the input quantity of the adjusting means.

Claim 4

The method of claim 2 wherein the adjusting means includes a controller connected to a positioning device for adjusting the flow of one of the operating mediums to the heat exchanger, comprising supplying the control deviation (xwi) of the specific enthalpy as a correction quantity for the input quantity (e) of the controller.

Claim 5

The method of claim 2 comprising supplying respective predetermined reference values of pressure (po) and temperature (To) for the slightly superheated steam to the computation circuit, and determining the control deviation (xwi) of the specific enthalpy from the measured actual values of the pressure (pi) and temperature (Ti) and the predetermined refernce values of pressure (po) and temperature (To).

Claim 6

The method of claim 4 comprising determining the specific enthalpy (xwi) according to the equation: xwi Kp xwp + KT xwT wherein Kp and KT are predetermined values and wherein (xwp) is the control deviation (pi - po) of the pressure and (xwT) is the control deviation (Ti - To) of the temperature.

Claim 7

The method of claim 5 wherein the heat exchanger supplies a load and wherein the values of pressure (po) and temperature (To) are functions of the load.

Claim 8

The method of claim 5 wherein the heat exchanger supplies a load and wherein the values of (Kp) and (KT) are functions of the load.

Claim 9

The method of claim 5 wherein the heat exchanger supplies a load and wherein the values of pressure (po) and temperature (To) and the values of (Kp) and (KT) are all functions of the load.

Claim 10

The method of claim 5 wherein the heat exchanger is connectable to a turbogenerator for supplying the same, the turbogenerator having a specified value (Po) of electric capacity, and wherein the values of pressure (po) and temperature (To) are functions of (Po).

Claim 11

The method of claim 5 wherein the heat exchanger is connectable to a turbogenerator for supplying the same, the turbogenerator having a reference value (Po) of electric capacity, and wherein the values of (Kp) and (KT) are functions of (Po).

Claim 12

The method of claim 5 wherein the heat exchanger is connectable to a turbogenerator for supplying the same, the turbogenerator having a reference value (Po) of electric capacity, and wherein the values of pressure (po) and temperature (To) and values of (Kp) and (KT) are all functions of (Po). of a i i

Claim 13

The method of claim 2 wherein the heat exchanger operates under the condition that the reference value of the pressure (po) is variable and the reference value of the enthalpy (io) of the slightly superheated steam is constant, and wherein the method comprises forming a pressure dependent auxiliary quantity as a function of the measured actual pressure (pi), said quantity being in the form of reference temperature (Ts), subtracting the reference temperature (Ts) from the measured actual temperature (Ti) to determine a temperature deviation (Ti- Ts), and determining the control deviation (xwi) of the specific enthalpy as a function of the temperature deviation (Ti- Ts).

Claim 14

The method of claim 2 wherein the heat exchanger operates under the condition that the reference value of the pressure (po) is substantially constant and that the reference enthalpy (io) of the slightly superheated steam is constant, and wherein the method comprises determining the control deviation (xwi) of the specific enthalpy according to the equation: xwi ( Delta i/ Delta T)p (Ti - Ts) wherein the quantity ( Delta i/ Delta T)p is predetermined as dependent upon the operating point (io, po, To) of the slightly superheated steam, and wherein the quantity (Ts) is a reference temperature dependent upon pressure and determined from the equation: Ts To + aT , p (pi - po) wherein aT , p is fixed.

Claim 15

The method of claim 2 wherein the heat exchanger operates at a reference enthalpy (io) of the slightly superheated steam which varies about a mean enthalpy value (io), comprising: forming a pressure dependent reference temperature (Ts) as a function of the measured actual pressure (pi), subtracting the reference temperature (Ts) from the measured actual temperature (Ti) to determine the temperature deviation (Ti - Ts), determining a control deviation quantity (x*wi) as a function of the temperature deviation (Ti - Ts), and subtracting an intended enthalpy change ( Delta io io - io) from the quantity (x*wi) to form the control deviation (xwi).

Claim 16

The method of claim 14 wherein heat exchanger supplies a load and wherein the intended enthalpy change ( Delta io) is a fuNction of the load.

Claim 17

The method of claim 15 wherein the heat exchanger is connectable to a turbogenerator for supplying the same, the turbogenerator having a specified value (Po) of electric capacity, and wherein the intended enthalpy change ( Delta io) is a function of (Po).

Claim 18

The method of claim 14 wherein the heat exchanger is equipped with an injection cooler supplied with intensely heated steam and a superordinated controller, comprising detecting the temperature difference (T''i - T''o) of the intensely superheated steam at the injection cooler and forming therewith the deviation quantity (x''w T), and supplying the deviation quantity (x''w T) to the superordinated controller to form the quantity ( Delta i''o) for correcting the enthalpy deviation ( Delta io).

Claim 19

In a heat exchanger such as a forced-flow boiler or the like supplied with the operating mediums of fuel and feedwater and having an evaporator wherein slightly superheated steam is generated, the heat exchanger being equipped with an apparatus for controlling the heat exchanger, the apparatus comprising pressure detection means and temperature detection means for continuously measuring the pressure and temperature respectively of the slightly superheated steam at the output of the evaporator, computation means connected to said detection means for continuously determining the specific actual enthalpy of the slightly superheated steam, and means connected to said computation means for controlling the heat exchanger in response to said specific actual enthalpy.

Claim 20

In a heat exchanger such as a forced-flow boiler or the like supplied with the operating mediums of fuel and feedwater and having an evaporator wherein slightly superheated steam is generated, the heat exchanger being equipped with an apparatus for controlling the heat exchanger, the apparatus comprising pressure detection means and temperature detection means for continuously measuring the pressure and temperature respectively of the slightly superheated steam at the output of the evaporator, computation means connected to said detection means for continuously determining the specific actual enthalpy of the slightly superheated steam, and means connected to said computation means for controlling the heat exchanger in response to said specific actual enthalpy.

Claim 21

The apparatus of claim 18 wherein the apparatus controls at least one of the operating mediums said last-mentioned means being adjustment means for adjusting the flow of at least one of said mediums to the heat exchanger in response to said specific actual enthalpy.

Claim 22

The apparatus of claim 19 wherein the heat exchanger is equipped with a conduit to supply the feedwater to the heat exchanger proper, said adjustment means comprising positioning equipment, said equipment including a valve for controlling the supply of feedwater to the heat exchanger, and a positioning device connected to said valve for adjusting the position of said valve.

Claim 23

The apparatus of claim 19 wherein the heat exchanger is equipped with a conduit to supply the fuel to the heat exchanger proper, said adjustment means comprising positioning equipment said equipment including a valve for controlling the supply of fuel to the heat exchanger, and a positioning device connected to said valve for adjusting the position of said valve.

Claim 24

The apparatus of claim 19, said pressure detection means comprising a pressure transmitter placed at the output of the evaporator, and a pressure transducer connected to said pressure transmitter for converting said pressure to a corresponding electrical quantity; said temperature detection means comprising a temperature transmitter placed at the output of the evaporator, and a temperature transducer connected to said temperature transmitter for converting said temperature to a corresponding electrical quantity; said computation means comprising respective reference transmitters for providing respective predetermined electrical reference quantities of pressure and temperature for the slightly superheated steam, and further computation circuit means connected to said reference transmitters and said transducers for forming a control deviation signal corresponding to the deviation of the specific actual enthalpy from the reference value of the enthalpy; and said adjustment means comprising means responsive to the control deviation signal for adjusting the flow of at least one of the operating mediums to the heat exchanger.