CN2663907Y - Accurate mathematical controller for compact heat exchanger - Google Patents

Abstract

The utility model relates to an accurate mathematical controller for compact heat exchanger, comprising a micro-computer CPU, a multi-path analog switch and A/ D converter, an RAM memorizer, an EPROM memorizer, a D/ A converter, a set point station and a power-supply system, wherein a detector is arranged in the inlet end of the heat exchanger, and the detector is connected with the A/ D converter through the multi-path analog switch; the inlet parameter which is detected by the detector is converted from analog quantity to digital quantity and is transmitted into the micro-computer CPU connected with the RAM memorizer, the EPROM memorizer and a parameter set point station; the number value of the auxiliary fluid regulating variable can be acquired from an enquiry data base or an indirect-problem algorithm routine which are stored in the EPROM memorizer, the micro-computer CPU transmits an actuator which is used to control the auxiliary fluid, and thus, flow quantity regulation for the auxiliary fluid is realized. On the basis of feed forward control, the utility model introduces an accurate mathematical model of the heat exchanger into a feed forward control device, and then, the accurate mathematical model is integrated into an accurate mathematical controller; the utility model controls the compact heat exchanger with high accuracy and zero lag, and achieves obvious effect.

Description

The compact heat exchanger accurate mathematics controller

Technical field

The utility model relates to a kind of accurate mathematics controller that is widely used in the compact heat exchanger in fields such as chemical industry, space flight, automobile, belongs to the energy and power engineering technology field.

Background technology

Compact heat exchanger is because numerous advantages such as compactness height, heat exchange property be good just are being widely used in fields such as chemical industry, space flight, automobile, and it is to guarantee process conditions and carry out temperature controlled capital equipment.In actual moving process, because the variation of off-design operating mode usually takes place working condition, therefore, the control of heat exchanger is the key of good temperature control quality and high product quality.At present, the control of heat exchanger mainly can be divided into two kinds, and the first serves as the control parameter with the target fluid outlet temperature, is the FEEDBACK CONTROL of regulated quantity with the auxiliary fluid flow, under disturbance quantity was not very big situation, this control mode was widely used in compact heat exchanger; Another kind of control method is by increasing the by-pass governing method of target fluid bypass passageways, and this control mode is mainly used in the large-scale heat transmission equipment such as shell-and-tube, owing to increased bypass passageways, makes that the performance of heat exchanger can not be brought into play fully.Above-mentioned two kinds of control modes on control method, all belong to FEEDBACK CONTROL.Because the work characteristics of heat exchanger, making it all have very big volume lags behind and pure hysteresis, but FEEDBACK CONTROL only just can work after the target fluid technological parameter has changed, therefore, usually cause regulating action hysteresis, regulate shortcomings such as overlong time and overshoot be excessive, so, can not reach very high control quality generally speaking.

In view of the above problems, start with from improving the control lag effect, feed forward control method also once was suggested, and what this method was used is the transfer function that experimental method or theory method obtain.But, because the complexity of heat transfer process in the heat exchanger, make parameter in the different operating points place transfer function, even transfer function integral body there are differences all, though therefore control rate makes moderate progress, be difficult to the control accuracy that reaches enough.

Summary of the invention

The purpose of this utility model is in order to overcome the weak point of existing control, provide a kind of on the basis of FEEDFORWARD CONTROL, the mathematical models of heat exchanger is introduced feedforward controller, and integrated control method and hardware device are in the accurate mathematics controller of the compact heat exchanger of one, improve the control quality of compact heat exchanger, realize its high accuracy, do not have the control that lags behind, thereby improve the level of technological parameter, the purpose of improving the quality of products.

The technical solution of the utility model is: the compact heat exchanger accurate mathematics controller comprises: micro computer CPU, multiway analog switch and A/D converter, RAM memory, eprom memory, D/A converter, setting apparatus and power-supply system; The detector that the heat exchanger entrance end is equipped with is connected with A/D converter through multiway analog switch, the detected heat exchanger entrance parameter of detector converts digital quantity to by analog quantity and sends into micro computer CPU, RAM memory and have Query Database or an indirect problem algorithm program, primary control program, boot, the eprom memory of data processor, the parameter setting apparatus is connected with micro computer CPU, obtain auxiliary fluid regulated quantity numerical value by Query Database in the eprom memory or indirect problem algorithm program, by micro computer CPU output executing agency, the adjusting of realization auxiliary fluid flow by the auxiliary fluid that is connected with D/A converter.

Effect of the present utility model is:

The utility model adopts the method (indirect problem algorithm perhaps simply feedovers) of data base querying, and the fastest regulated quantity given way can be provided, and therefore, can guarantee control rate to greatest extent; Adopt mathematical models, can guarantee control accuracy,, when the heat exchanger performance parameter is accurate, can realizes high accuracy, not have the control dynamic transition process that lags behind, even can eliminate transient process in conjunction with the advantage of control rate; Heat exchanger control system in the past adopts a whole set of computer system often, and not only investment is big, and complex structure, and the wiring debugging cycle is long; And make things convenient for controller architecture compactness, the application that this method is made; The utility model is on the basis of FEEDFORWARD CONTROL, the mathematical models of heat exchanger is introduced feedforward controller, and it is integrated into accurate mathematics controller, realizes the compact heat exchanger high accuracy, does not have the control that lags behind, and obtains obvious effects.

Description of drawings

Fig. 1 is a compact heat exchanger accurate mathematics controller structured flowchart.

The specific embodiment

Need to implement according to the following steps:

1, setting up precise math model, be directed to the compact heat exchanger of any known structure and duty parameter, can set up its mathematical models, is example with the plate-fin heat exchanger, and its Mathematical Modeling comprises:

The fluid energy equilibrium equation

${\left({\mathrm{\ρC}}_p\right)}_i\frac{{\∂T}_i}{\∂\mathrm{\τ}}+{\left({\mathrm{GC}}_p\right)}_i\frac{{\mathrm{dT}}_i}{\mathrm{dz}}={(1-\mathrm{\ξ\δ})}_i{\mathrm{\α}}_i(T_{b,i}+T_{b,i+1}-{2T}_i)+2{\mathrm{\ξ}}_i{\mathrm{\α}}_i{\∫}_{x=0}^{b_i}(T_{p,i}\left(x\right)-T_i)---\left(1\right)$

The dividing plate energy-balance equation

$-{\left(\mathrm{\ξ\δ}\right)}_i\mathrm{\λ}\frac{{\∂T}_{p,i}}{\∂x}{|}_{x=b_i}+{\left(\mathrm{\ξ\δ}\right)}_{+1i}\mathrm{\λ}\frac{{\∂T}_{p,i+1}}{\∂x}{|}_{x=0}+{\mathrm{\δ}}_i\mathrm{\λ}\frac{{\∂}^2{T}_{b,i}}{{\∂z}^2}+{(1-\mathrm{\ξ\δ})}_i{\mathrm{\α}}_i[T_i-T_{b,i+1}]---\left(2\right)$

$+{(1-\mathrm{\ξ\δ})}_{i+1}{\mathrm{\α}}_{i+1}[T_{i+1}-T_{b,i+1}]=\left({\mathrm{\ρ}}_b{C}_p\right)\frac{{\∂T}_{p,i}(p,i+1)}{\∂\mathrm{\τ}}$

The fin energy-balance equation

${\left(\mathrm{\ξ\δ}\right)}_i\mathrm{\λ}\frac{{\∂}^2{T}_{p,i}(x,z)}{{\∂x}^2}+{\left(\mathrm{\ξ\δ}\right)}_i\mathrm{\λ}\frac{{\∂}^2{T}_{p,i}(x,z)}{{\∂z}^2}-2{\mathrm{\ξ}}_i{\mathrm{\α}}_i(T_{p,i}(x,z)-T_i)=\left({\mathrm{\ρ}}_p{C}_p\right)\frac{{\∂T}_{p,i}(x,z)}{\∂\mathrm{\τ}}---\left(3\right)$

Using numerical solution can be in the hope of the heat exchanger output parameter under any initial conditions.

2, obtain to regulate parameter;

After the control of heat exchanger is meant that target fluid or auxiliary fluid suction parameter (temperature or flow) change, guarantees that the target fluid outlet parameter is constant or turn back to the setting process parameters range by regulating action.Therefore, Guan Jian problem is to regulate the acquisition of parameter.If directly obtain this parameter, and regulating action can be provided in time, the control quality will be improved widely so.Therefore, this method is that preposition (temperature and flow) detector is set in the porch of heat exchanger, disturbance situation by this detector perception suction parameter in time, and can obtain the situation of change of outlet parameter by mathematical models, when disturbance quantity is enough to change outlet parameter, obtain the numerical value of auxiliary fluid regulated quantity by the computational methods of " indirect problem ", and send regulating action in time, like this, just the effect of disturbance can be eliminated before the target fluid outlet parameter changes.

3, numerical solution solving heat exchange device mathematical models;

By a database that comprises the adjusting scale of all power condition changing situations,, obtain the numerical value of regulated quantity in the fastest mode with the method for Query Database in the feedforward controller.At present, finding the solution of compact heat exchanger Mathematical Modeling mainly contains two kinds of methods, i.e. numerical method and analytic method.In the two, numerical method is acknowledged as method the most accurately, and it can find the solution the heat exchanger diffusion model that does not add any simplification and hypothesis, and analytic solutions are only under certain simplified condition, and just can find the solution under the simple situation of heat exchanger structure.Therefore, the art of this patent is utilized numerical solution solving heat exchange device mathematical models, has considered that fluid heat conduction, fin and dividing plate laterally reach vertical heat conduction and whole diffusion inside effects, can obtain the result of clock like precision.But, need the long period by numerical methods of solving " indirect problem ", can not guarantee the speed controlled, therefore, for any heat exchanger, be the adjusting scale that comprises all power condition changing situations by one of prior acquisition, be stored in chip internal, inquire about at any time for control system with the form of database.Like this, can obtain the numerical value of regulated quantity in the fastest mode.The capacity of database can decide according to the actual condition change conditions.

In addition, adopt ε-NTU method or logarithmic mean temperature difference (LMTD) method also to can be used as the core feedforward arithmetic of the simple compact heat exchanger accurate mathematics controller of structure, because it calculates simple, can directly use indirect problem algorithm, and needn't adopt " database ", but be not so good as " database " method on the precision.

4, make accurate mathematics controller with single-chip microcomputer or PLC controller.

By shown in Figure 1, it comprises:

1) becomes the micro computer CPU8 of functions such as all calculating, input and output, data query, data processing, adopt single-chip microcomputer (98 or 51 series) or programmable logic controller (PLC) cpu chip;

2) multiway analog switch 6 and A/D converter 7 are selected general-purpose device for use according to required precision and speed, constitute analog input channel, realize the touring detection of heat exchanging device suction parameter (temperature and flow) under the CPU commander, and are converted to data volume for the CPU processing;

3) provide CPU to calculate and the RAM memory 11 of the memory space of deal with data, the employing general-purpose chip when memory desired volume hour, also can adopt the CPU on-chip memory, thereby save this element;

4) eprom memory 12 of application programs such as the master control program of inside solidification accurate mathematics controller, boot, data processor, Query Database or indirect problem algorithm program adopts general-purpose chip;

5) be used to provide auxiliary fluid executing agency (control valve or frequency converter etc.) signal, realization is to the D/A converter 9 of the adjusting of auxiliary fluid flow, select general-purpose chip for use according to required precision and speed, current signal of outputting standard (4-20mA or 0-10mA) or voltage signal (0-10V or other optional scope);

6) be used to be provided with the setting apparatus 13 of the form of input sample primary element form and canonical parameter (for example thermoelectricity thermal resistance occasionally, and thermocouple kind etc.), output signal and range ability etc.:

7) power-supply system 10, provide all required power supply signals of accurate mathematics controller.

1 is that target fluid, 2 is that auxiliary fluid, 3 is that heat exchanger body, 4,5 is heat exchanger entrance and outlet among the figure.

Claims (1)

1, a kind of compact heat exchanger accurate mathematics controller is characterized in that it comprises: micro computer CPU (8), multiway analog switch (6) and A/D converter (7), RAM memory (11), eprom memory (12), D/A converter (9), setting apparatus (13) and power-supply system (10); The detector that the heat exchanger entrance end is equipped with is connected with A/D converter (7) through multiway analog switch (6), the detected heat exchanger entrance parameter of detector converts digital quantity to by analog quantity and sends into micro computer CPU (8), RAM memory (11) and have Query Database or the indirect problem algorithm program, primary control program, boot, the eprom memory of data processor (12), parameter setting apparatus (13) is connected with micro computer CPU (8), obtain auxiliary fluid regulated quantity numerical value by Query Database in the eprom memory (12) or indirect problem algorithm program, by micro computer CPU (8) output executing agency, the adjusting of realization auxiliary fluid flow by the auxiliary fluid that is connected with D/A converter (9).