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US 3,970,832 AGranted
Apparatus and method for obtaining an electrical signal corresponding to the specific enthalpy of steam
AssigneeSiemens Aktiengesellschaft
InventorBruno Itschner
Life of this patent
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Abstract
Apparatus and method for obtaining an electrical signal corresponding to the enthalpy of steam expressed by Koch's state equation, is disclosed. In the form of Koch's state equation which is used, terms of minor significance are neglected and the equation is converted into a logarithmic form suitable for solution by electrical analog computer elements. A circuit arrangement comprised of adders, multipliers and function generators is disclosed for simulating and solving the potential and exponential functions in the formula for the enthalpy i = j.sub.o (t) - A.sup.. p(1/t.sup.2.82) - e.sup.(1n B .sup.+ 3 in p .sup.- 14 1n t) , where i.sub.o is a basic quantity dependent only on the temperature t, the pressure, p, and A and B are constants.
Claims9
Apparatus for determining the specific enthalpy of steam according to Koch's state equation comprising
- a first means responsive to the temperature of the steam for producing a variable output signal E(t) which is a function of the natural logarithm of the temperature;
- a second means responsive to the pressure of the steam for producing a variable output signal F(p) which is a function of the sum of a constant and the natural logarithm of the pressure;
- a third means connected to the output of the two means for algebraically adding the variable outputs of said means to form a combined output signal;
- means connected to the combining means responsive to the combined signals for producing a variable output signal G(p,t) which is a function of c.sup[sup.F(p) .sup.- E(t).sup.] ;
- means responsive to the temperature of the steam for producing a variable output signal D(t) which is a function of the temperature raised to the -2.82 power;
- means connected to the output of the temperature responsive means and a signal proportional to the pressure, said means responsive to both signals for producing a variable output signal which is a function of the product of the steam pressure and the function D(t);
- and
- a summing means having four inputs, the variable output signal G(p,t) as a first input, the product of the pressure and D(t) as a second input, the variable signal which is a function of the temperature of the steam as a third input and a signal which is proportional to a predetermined constant as a fourth input, said summing means producing a variable output signal in response to said inputs which is a function of the specific enthalpy of the steam in accordance with Koch's state equation.
5 more elements
Apparatus for determining the specific enthalpy of steam according to Koch's state equation comprising
- a first means responsive to the temperature of the steam for producing a variable output signal E(t) which is a function of the natural logarithm of the temperature,
- a second means responsive to the pressure of the steam for producing a variable output signal F(p) which is a function of the sum of a constant and the natural loarithm of the pressure,
- a third means connected to the output of the two means for algebraically adding the variable outputs of said means to form a combined output signal,
- means connected to the combining means responsive to the combined signals for producing a variable output signal G(p,t) which is a function of c.sup[sup.F(p) .sup.- E(t).sup.],
- means, responsive to the temperature of the steam, for adding a signal proportional to the temperature of the steam and a predetermined constant, to produce a variable output signal representing the sum of the two functions,
- dividing means having the output of said summing means as a first input and a signal proportional to the pressure of the steam as a second input, said dividing means producing a variable output signal which is a function of the pressure divided by the sum of the predetermined constant and the temperature,
- a summing means having four inputs, the variable output signal G(p,t) as the first input, the output of the dividing means as the second input, the variable signal which is a function of the temperature as the third input and a signal which is proportional to a predetermined constant as the fourth input, said summing means producing a variable output signal in response to said inputs which is a function of the specific enthalpy of the steam in accordance with Koch's state equation.
4 more elements
A method for determining the specific enthalpy of steam according to Koch's state equation comprising the steps of
- producing an electrical signal E(t) in response to the temperature of the steam, said signal being a function of the product of a predetermined constant and the natural logarithm of temperature,
- producing an electrical signal F(p) in response to the pressure of the steam, said signal being a function of the sum of the natural logarithm of a predetermined constant and the product of a constant and a natural logarithm of the pressure of the steam,
- algebraically adding the two electrical signals to produce a sum in which the signal which is a function of the predetermined constant and the natural logarithm of the temperature is subtracted from the signal,
- producing an electrical signal G(p,t) in response to the algebraically added signals, said signal G(p,t) being a function of the base e raised to the F(p) - E(t) power,
- producing an electrical signal, D(t), in response to the temperature of the steam, said signal D9t) being a function of the temperature raised to the -2.82 power,
- multiplying the electrical signal D(t) by a signal proportional to the pressure of the steam to produce an electrical signal proportional to p .sup.. t.sup.-.sup.2.82 power,
- adding the electrical signals G(p,t), the product p .sup.. t.sup.-.sup.2.82, a predetermined constant and a signal proportional to the temperature of the steam, both the signals G(p,t) and the product p .sup.. t.sup.-.sup.2.82 being added negatively to the predetermined constant and the signal proportional to the temperature, the signal produced by said addition representing the specific enthalpy of the steam in accordance with Koch's equation, and wherein all of the foregoing steps are carried out in analog computing apparatus.
4 more elements
A method for determining the specific enthalpy of steam according to Koch's state equation comprising the steps of
- producing an electrical signal E(t) in response to the temperature of the steam, said signal being a function of the product of a predetermined constant and the natural logarithm of the temperature,
- producing an electrical signal F(p) in response to the pressure of the steam, said signal being a function of the sum of the natural logarithm of a predetermined constant and the product of a constant and the natural logarithm of the pressure of the steam,
- algebraically adding the two electrical signals to produce a sum in which the signal which is a function of the predetermined constant and the natural logarithm of the temperature is subtracted from the other signal,
- producing an electrical signal G(p,t) in response to the algebraically added signals, said signal G(p,t) being a function of the base e raised to the F(p) - E(t) power,
- producing an electrical signal H(t) representing the sum of a first predetermined constant and the product of a second predetermined constant and a signal proportional to the temperature of the steam.
- dividing a signal proportional to the pressure of the steam by the signal H(t) to form a variable output signal proportional to p .sup.. t.sup.-.sup.2.82,
- adding the electrical signals G(p,t), the product p .sup.. t.sup.-.sup.2.82, a predetermined constant and a signal proportional to the temperature of the steam, both the signals G(p,t) and the product p .sup.. t.sup.-.sup.2.82 being added negatively to the predetermined constant and the signal proportional to the temperature, the signal produced by said addition representing the specific enthalpy of the steam in accordance with Koch's equation, and wherein all of the foregoing steps are carried out in analog computing apparatus.
4 more elements
Dependencies are inferred from the claim text.