EP0588052A1 - Method for controlling an air-conditioning installation - Google Patents

Abstract

An air-conditioning installation with, at the inlet, a mixing chamber for mixing outside air with circulating air, a preheater, a cooler, a humidifier, for example an air washer, and a reheater, is to be controlled in such a way that an amount of outlay reflecting the operating outlay, for example the sum of the absolute values of the enthalpy changes caused by the activated units, is minimal. For the purpose of selecting the units to be activated, first state trajectories proceeding from an initial state (full circle) and second state trajectories leading to the desired state (x) are determined in the hx diagram, possible transitions are determined by calculating the sectional state (S; S'; S''), and the corresponding amounts of outlay are calculated. The possible transition with the lowest amount of outlay is selected, that is to say the corresponding units are activated and are controlled with the effect of bringing about the transition, for example by regulating the mixing chamber in terms of temperature and the humidifier in terms of moisture. <IMAGE>

Description

The invention relates to a method for controlling an air conditioning system according to the preamble of claim 1.

Such a method is known from DE-C-3 439 288 and from automation practice atp 28/4 (1986), pp. 184-190, in which for an air conditioning system with a mixing chamber, a preheater, a cooler, a humidifier and a reheater for a given target state of the air given off to supply rooms and a determined state of the recirculated air extracted from said rooms, the state of the outside air is then checked in which a row of subfields of the two-dimensional state room - represented as a Mollier's hx diagram - it lies and after In the corresponding subfield, a specific combination of units of the air conditioning system is selected and controlled in such a way that the air released reaches the desired state, while the other units are operated in idle mode. The aggregates are selected so that the path to the target state - if there are alternatives - is covered in such a way that the sum of the absolute values of the enthalpy changes caused by the selected aggregates is minimal. The boundaries between the subfields are each defined by i. a. defines linear equations that relate the enthalpy or temperature to the humidity.

This solution has several disadvantages. Even slight shifts in the condition of the outside air or the recirculating air result in shifts in the boundaries between the subfields, which make it necessary to recalculate them.

In addition, the method described in the publications mentioned assumes that the relative position of the conditions of air circulation and outside air meets certain qualitative requirements: the former is both humid and warmer than the latter, which is probably the case, but need not be so .

It is not immediately apparent how the subdivision into subfields has to be changed if the said relative location changes qualitatively, but it can be assumed that the boundaries of the subfields will not only shift, but a substantially new picture will emerge , so that the entire division z. T. newly determined for the limits based on new equations or a series of different rules and equation sets saved for different cases and depending on the starting point a selection must be made.

In this way, at least in the case of air conditioning systems with a mixing chamber, the set of rules required for the selection of the units to be used becomes very complex and confusing. In addition, there is considerable computing effort.

The calculation of the size of the effort on which the selection of the transition is based is determined as described above, so that, for example, different efficiencies or cost factors of different aggregates cannot be taken into account. It is also not easy to see whether and if so how the method can be adapted to a more refined calculation of the amount of effort that takes such effects into account.

The method seems to be limited to aggregates whose trajectory is a straight line in the hx diagram or can in any case be approximated sufficiently precisely by a straight line. Also the possibility of adjustments on differently constructed air conditioning systems is not readily apparent. In any case, such adjustments cannot be carried out without fundamental considerations.

In contrast, the invention, as characterized in the claims, provides a method for controlling an air conditioning system, which is extremely flexible in every respect.

According to the invention, the units to be used are preselected according to the relative position of the desired state and the states of the outside and recirculated air, at most within a very limited, easily manageable framework, and the procedure is always the same. The control procedure is therefore clear and easier to implement without errors. The computational effort is low, since the scope of the new calculations to be carried out when the air conditions are shifted remains very modest.

The amount of effort on which the selection of the units is based and whose correctness and accuracy is therefore crucial for the economical operation of the air conditioning system can be freely defined and take into account different efficiencies and cost factors of the various units, possibly also different efficiencies or cost factors of an unit in different areas the state level.

In addition to the usual and usually sufficient representation of the function of the various aggregates by means of a straight line in the hx diagram, it is also possible to use those which take nonlinearities into account - corresponding to nonlinear trajectories.

The method according to the invention can be implemented in a modular program executed by a computer, in which each unit is simulated by a module. The modules are easily interchangeable, so that the program - and thus the process - can be quickly and easily adapted to different unit configurations. Even if one unit fails, the control process can be easily adapted and the air conditioning system can continue to be operated as far as possible.

In general, the method according to the invention offers the possibility of adapting, expanding and refining the control in many directions as required.

Fig. 1

eine schematische Darstellung einer Klimaanlage, die nach dem erfindungsgemässen Verfahren gesteuert werden kann,

Fig. 2

die Zustandstrajektorie einer Mischkammer im hx-Diagramm, d. h. die Menge der Zustände, die bei gegebenem Luftzuständen an den Eingängen der Mischkammer am Ausgang derselben erzeugt werden können,

Fig. 3

die Zustandstrajektorie eines Vor- oder Nachwärmers,

Fig. 4

die Zustandstrajektorie eines Kühlers,

Fig. 5

die Zustandstrajektorie eines Luftwäschers,

Fig. 6

die Zustandstrajektorie eines Dampfbefeuchters,

Fig. 7 - 9

verschiedene Uebergänge bei diversen Konstellationen von Sollzustand, Umluftzustand und Aussenluftzustand in einer Klimaanlage gemäss Fig. 1, in der als Befeuchter ein Luftwäscher eingesetzt ist und

Fig. 10

einen Uebergang in einer Klimaanlage gemäss Fig. 1, in der als Befeuchter ein Dampfbefeuchter eingesetzt ist.

The invention is explained in more detail below with the aid of drawings which illustrate an exemplary embodiment and its mode of operation. Show it

Fig. 1

1 shows a schematic representation of an air conditioning system that can be controlled using the method according to the invention,

Fig. 2

the state trajectory of a mixing chamber in the hx diagram, ie the amount of states that can be generated at the inputs of the mixing chamber at the outlet of the same for a given air state,

Fig. 3

the state trajectory of a preheater or reheater,

Fig. 4

the state trajectory of a cooler,

Fig. 5

the state trajectory of an air washer,

Fig. 6

the state trajectory of a steam humidifier,

7 - 9

different transitions in various constellations of target state, recirculated air state and outside air state in an air conditioning system according to FIG. 1, in which an air washer is used as a humidifier and

Fig. 10

a transition in an air conditioning system according to FIG. 1, in which a steam humidifier is used as the humidifier.

An air conditioning system 1 contains (FIG. 1) five units through which air to be treated flows in succession. Via an outside air supply 2, the outside air is supplied to it and via a recirculating air supply 3, recirculating air is drawn off from the rooms supplied with air by the air conditioning system, while it supplies 4 supply air for supplying said rooms to a supply air extractor.

The outside air supply 2 and the recirculating air supply 3 open into an initially arranged mixing chamber 5, in which a controllable proportion of recirculating air is mixed into the outside air. A preheater 6 is connected to the mixing chamber 5, in which air which is supplied to it from the mixing chamber 5 can be brought to a higher temperature. A subsequent cooler 7, on the other hand, serves to lower the temperature of the supplied air and can also be used to reduce its humidity. Moisture can be added to the air by means of a subsequent humidifier 8. A reheater 9, from which the supply air outlet 4 starts, has the same function as the preheater 7.

The states of the outside air, the circulating air and the supply air are each monitored by temperature sensors 10a, 10b and 10c and humidity sensors 11a, 11b and 11c, the signals of which are fed to a control unit 12, which contains a computer, usually a microprocessor. The control unit 12 is also connected to the units of the air conditioning system 1 and controls the same.

The functions of the individual units are now explained using the hx diagram. The hx diagram has long been known in the field of air conditioning technology. It represents the two-dimensional state quantity of moist air, namely the humidity x, i.e. the horizontal axis. H. the water vapor content is plotted in g / kg. The lines of constant humidity run vertically, while the lines of the same enthalpy (i.e. the same heat content) form a system of parallel, equidistant straight lines running from top left to bottom right, which enables a direct reading of the enthalpy difference between two states. Of the constant temperature lines, only the zero degree isotherm runs horizontally, while the overlying isotherms are also straight lines, which however increase with increasing temperature.

In addition, lines of relative humidity are shown, of which the saturation line (100% relative humidity) is of particular interest, since it is the area in which all the moisture is in the form of water vapor, from the underlying so-called fog area, in which a part of the Forms damp water droplets, separates.

The water vapor partial pressure is given above the hx diagram and a key figure on the periphery, the meaning of which will be explained below in connection with the steam humidifier.

und

${\text{x}}_{\text{aus}}{\text{= λx}}_{\text{um}}{\text{+ (1-λ)x}}_{\text{aussen}}$

mit 0≦λ≦1 charakterisiert ist, wobei h für die Enthalpie und x für die Feuchte steht. Daraus ergeben sich

${\text{h}}_{\text{aus}}{\text{= h}}_{\text{aussen}}{\text{+ λ(h}}_{\text{um}}{\text{-h}}_{\text{aussen}}\text{)}$

und

${\text{x}}_{\text{aus}}{\text{= x}}_{\text{aussen}}{\text{+ λ(x}}_{\text{um}}{\text{-x}}_{\text{aussen}}\text{)}$

mit 0≦λ≦1. Mit den Bezeichnungen

${\text{r}}_{\text{h}}{\text{}}^{\text{M}}{\text{= h}}_{\text{um}}{\text{-h}}_{\text{aussen}}$

und

${\text{r}}_{\text{x}}{\text{}}^{\text{M}}{\text{= x}}_{\text{um}}{\text{-x}}_{\text{aussen}}$

erhält man die Darstellung

${\text{h}}_{\text{aus}}{\text{= h}}_{\text{aussen}}{\text{+ λr}}_{\text{h}}{\text{}}^{\text{M}}\text{, (1a)}$

${\text{x}}_{\text{aus}}{\text{= x}}_{\text{aussen}}{\text{+ λr}}_{\text{x}}{\text{}}^{\text{M}}\text{. (1b)}$

(h_aus,x_aus), (h_aussen,x_aussen) kann man jeweils zu Vektoren ξ _aus, ξ _aussen zusammenfassen ebenso wie (r_h ^M,r_x ^M) als Komponenten eines Richtungsvektors r ^M aufgefasst werden können. Dies führt auf die Darstellung

$\underline{\text{ξ}}{\text{}}_{\text{aus}}\text{=}\underline{\text{ξ}}{\text{}}_{\text{aussen}}\text{+ λ}\underline{\text{r}}{\text{}}^{\text{M}}\text{, 0≦λ≦1 (1)}$

für die Zustandstrajektorie. Das hochgestellte M bezeichnet das Aggregat, im vorliegenden Fall die Mischkammer. Die Trajektorie entspricht somit, vorausgesetzt, dass der Umluftanteil λ unbeschränkt ist, der den Aussenluftzustand und den Umluftzustand verbindenden geraden Strecke. Falls, wie oft aus hygienischen Gründen erforderlich, der Umluftanteil dagegen einen bestimmten Grenzwert nicht überschreiten darf, so ist nur ein an den Aussenluftzustand anschliessender Teil dieser Strecke zugänglich. Im dargestellten Beispiel wurde davon ausgegangen, dass λ≦²/₃ gelten muss, d. h. der Anteil der Umluft ca. 67% nicht überschreiten darf. Der Luftzustand am Ausgang der Mischkammer bei maximaler Umluftbeimischung ist durch einen Querstrich angedeutet. Die von der Luft in der Mischkammer durchlaufenen Zustände sollten ausserdem ausserhalb des Nebelgebiets bleiben, da sich sonst Kondenswasser bildet.2 shows the state trajectory of the mixing chamber 5. The mixture of outside air (full circle) and recirculating air (empty circle) leads to a linear interpolation between the corresponding humidities and enthalpies, i.e. with a recirculating air component λ and an outside air component 1-λ, an air condition results at the outlet of the mixing chamber, which

${\text{H}}_{\text{out}}{\text{= λh}}_{\text{around}}{\text{+ (1-λ) h}}_{\text{Outside}}$

and

${\text{x}}_{\text{out}}{\text{= λx}}_{\text{around}}{\text{+ (1-λ) x}}_{\text{Outside}}$

is characterized by 0 ≦ λ ≦ 1, where h stands for enthalpy and x for humidity. This results in

${\text{H}}_{\text{out}}{\text{= h}}_{\text{Outside}}{\text{+ λ (h}}_{\text{around}}{\text{-H}}_{\text{Outside}}\text{)}$

and

${\text{x}}_{\text{out}}{\text{= x}}_{\text{Outside}}{\text{+ λ (x}}_{\text{around}}{\text{-x}}_{\text{Outside}}\text{)}$

with 0 ≦ λ ≦ 1. With the labels

${\text{r}}_{\text{H}}{}^{\text{M}}{\text{= h}}_{\text{around}}{\text{-H}}_{\text{Outside}}$

and

${\text{r}}_{\text{x}}{}^{\text{M}}{\text{= x}}_{\text{around}}{\text{-x}}_{\text{Outside}}$

you get the representation

${\text{H}}_{\text{out}}{\text{= h}}_{\text{Outside}}{\text{+ λr}}_{\text{H}}{}^{\text{M}}\text{, (1a)}$

${\text{x}}_{\text{out}}{\text{= x}}_{\text{Outside}}{\text{+ λr}}_{\text{x}}{}^{\text{M}}\text{. (1b)}$

(h _out , x _out ), (h _outside , x _outside ) can be combined into vectors ξ _out , ξ _outside as well as (r _h ^M , r _x ^M ) can be understood as components of a direction vector r ^M. This leads to the presentation

$\underline{\text{ξ}}{}_{\text{out}}\text{=}\underline{\text{ξ}}{}_{\text{Outside}}\text{+ λ}\underline{\text{r}}{}^{\text{M}}\text{, 0 ≦ λ ≦ 1 (1)}$

for the state trajectory. The superscript M denotes the unit, in the present case the mixing chamber. The trajectory thus corresponds, provided that the recirculated air component λ is unlimited, of the straight section connecting the outside air condition and the recirculated air condition. If, as is often the case for hygienic reasons, the circulating air percentage must not exceed a certain limit value, only a part of this section that is connected to the outside air condition is accessible. in the The example shown was based on the assumption that λ ≦ ² / ₃ must apply, ie the proportion of air circulating must not exceed approx. 67%. The air condition at the outlet of the mixing chamber with maximum admixture of circulating air is indicated by a dash. The conditions passed through by the air in the mixing chamber should also remain outside the fog area, otherwise condensation will form.

mit λ≧0,

${\text{x}}_{\text{aus}}{\text{= x}}_{\text{ein}}\text{.}$

Wie im Fall der Mischkammer lässt sich dies auf die Form

${\text{h}}_{\text{aus}}{\text{= h}}_{\text{ein}}{\text{+ λr}}_{\text{h}}{\text{}}^{\text{W}}\text{ (2a)}$

${\text{x}}_{\text{aus}}{\text{= x}}_{\text{ein}}{\text{+ λr}}_{\text{x}}{\text{}}^{\text{W}}\text{ (2b)}$

mit λ≧0 bringen, wobei ${\text{r}}_{\text{h}}{\text{}}^{\text{W}}\text{=1}$

, ${\text{r}}_{\text{x}}{\text{}}^{\text{W}}\text{=0}$

gilt, und zu

$\underline{\text{ξ}}{\text{}}_{\text{aus}}\text{=}\underline{\text{ξ}}{\text{}}_{\text{ein}}\text{+ λ}\underline{\text{r}}{\text{}}^{\text{W}}\text{, λ≧0 (2)}$

mit r ^W=(r_h ^W,r_x ^W) zusammenfassen.Fig. 3 shows the state trajectory of the preheater 6 and the post-heater 9, which increase the enthalpy of the air without changing anything in the humidity, so that the trajectory forms a vertical half line which points upwards from the initial state, ie it applies

${\text{H}}_{\text{out}}{\text{= h}}_{\text{a}}\text{+ λ}$

with λ ≧ 0,

${\text{x}}_{\text{out}}{\text{= x}}_{\text{a}}\text{.}$

As in the case of the mixing chamber, this can be done on the shape

${\text{H}}_{\text{out}}{\text{= h}}_{\text{a}}{\text{+ λr}}_{\text{H}}{}^{\text{W}}\text{(2a)}$

${\text{x}}_{\text{out}}{\text{= x}}_{\text{a}}{\text{+ λr}}_{\text{x}}{}^{\text{W}}\text{(2 B)}$

bring with λ ≧ 0, where ${\text{r}}_{\text{H}}{}^{\text{W}}\text{= 1}$

, ${\text{r}}_{\text{x}}{}^{\text{W}}\text{= 0}$

applies, and too

$\underline{\text{ξ}}{}_{\text{out}}\text{=}\underline{\text{ξ}}{}_{\text{a}}\text{+ λ}\underline{\text{r}}{}^{\text{W}}\text{, λ ≧ 0 (2)}$

summarize with r ^W = (r _h ^W , r _x ^W ).

mit λ≧0,

${\text{x}}_{\text{aus}}{\text{= x}}_{\text{ein}}$

oder

${\text{h}}_{\text{aus}}{\text{= h}}_{\text{ein}}{\text{+ λr}}_{\text{h}}{\text{}}^{\text{K}}\text{ (3a)}$

${\text{x}}_{\text{aus}}{\text{= x}}_{\text{ein}}{\text{+ λr}}_{\text{x}}{\text{}}^{\text{K}}\text{ (3b)}$

mit λ≧0, wobei r_h ^K=-1, r_x ^K=0, und zusammengefasst

$\underline{\text{ξ}}{\text{}}_{\text{aus}}\text{=}\underline{\text{ξ}}{\text{}}_{\text{ein}}\text{+ λ}\underline{\text{r}}{\text{}}^{\text{K}}\text{, λ≧0 (3)}$

mit $\underline{\text{r}}{\text{}}^{\text{K}}{\text{=(r}}_{\text{h}}{\text{}}^{\text{K}}{\text{,r}}_{\text{x}}{\text{}}^{\text{K}}\text{)}$

. Die Sättigungslinie und damit auch der entsprechende Teil der Zustandstrajektorie des Kühlers 7 wird durch eine nichtlineare Funktion h_sat(x) angenähert.Also a vertical line (FIG. 4) is the part of the state trajectory of the cooler 7 which lies above the saturation line and which lowers the enthalpy of the air without changing its humidity until the saturation line is reached. Water droplets form on the saturation line, which precipitate out and settle in the cooler 7 when cooling continues, so that a reduction in the moisture occurs. The state trajectory then follows the saturation line (this representation is somewhat idealized, the trajectory does not directly meet the saturation line, but clings to it, but the approximation described is sufficient for calculation purposes). So above the saturation line

${\text{H}}_{\text{out}}{\text{= h}}_{\text{a}}\text{- λ}$

with λ ≧ 0,

${\text{x}}_{\text{out}}{\text{= x}}_{\text{a}}$

or

${\text{H}}_{\text{out}}{\text{= h}}_{\text{a}}{\text{+ λr}}_{\text{H}}{}^{\text{K}}\text{(3a)}$

${\text{x}}_{\text{out}}{\text{= x}}_{\text{a}}{\text{+ λr}}_{\text{x}}{}^{\text{K}}\text{(3b)}$

with λ ≧ 0, where r _h ^K = -1, r _x ^K = 0, and summarized

$\underline{\text{ξ}}{}_{\text{out}}\text{=}\underline{\text{ξ}}{}_{\text{a}}\text{+ λ}\underline{\text{r}}{}^{\text{K}}\text{, λ ≧ 0 (3)}$

With $\underline{\text{r}}{}^{\text{K}}{\text{= (r}}_{\text{H}}{}^{\text{K}}{\text{, r}}_{\text{x}}{}^{\text{K}}\text{)}$

. The saturation line and thus also the corresponding part of the state trajectory of the cooler 7 is approximated by a nonlinear function h _sat (x).

${\text{x}}_{\text{aus}}{\text{= x}}_{\text{ein}}\text{+ λ}$

mit λ≧0
oder

${\text{h}}_{\text{aus}}{\text{= h}}_{\text{ein}}{\text{+ λr}}_{\text{h}}{\text{}}^{\text{L}}\text{ (4a)}$

${\text{x}}_{\text{aus}}{\text{= x}}_{\text{ein}}{\text{+ λr}}_{\text{x}}{\text{}}^{\text{L}}\text{ (4b)}$

mit λ≧0, wobei ${\text{r}}_{\text{h}}{\text{}}^{\text{L}}\text{=0}$

, ${\text{r}}_{\text{x}}{\text{}}^{\text{L}}\text{=1}$

, zusammengefasst

$\underline{\text{ξ}}{\text{}}_{\text{aus}}\text{=}\underline{\text{ξ}}{\text{}}_{\text{ein}}\text{+ λ}\underline{\text{r}}{\text{}}^{\text{L}}\text{, λ≧0 (4)}$

mit $\underline{\text{r}}{\text{}}^{\text{L}}{\text{=(r}}_{\text{h}}{\text{}}^{\text{L}}{\text{,r}}_{\text{x}}{\text{}}^{\text{L}}\text{)}$

.If the humidifier 8 is an air washer with circulating water (FIG. 5), its state trajectory forms a line of increasing humidity and constant enthalpy, since an equilibrium state is established in which no heat is supplied or removed by the air washer. The trajectory ends at the saturation line since the air no longer absorbs water vapor when it has reached saturation. It is characterized by

${\text{H}}_{\text{out}}{\text{= h}}_{\text{a}}\text{,}$

${\text{x}}_{\text{out}}{\text{= x}}_{\text{a}}\text{+ λ}$

with λ ≧ 0
or

${\text{H}}_{\text{out}}{\text{= h}}_{\text{a}}{\text{+ λr}}_{\text{H}}{}^{\text{L}}\text{(4a)}$

${\text{x}}_{\text{out}}{\text{= x}}_{\text{a}}{\text{+ λr}}_{\text{x}}{}^{\text{L}}\text{(4b)}$

with λ ≧ 0, where ${\text{r}}_{\text{H}}{}^{\text{L}}\text{= 0}$

, ${\text{r}}_{\text{x}}{}^{\text{L}}\text{= 1}$

, summarized

$\underline{\text{ξ}}{}_{\text{out}}\text{=}\underline{\text{ξ}}{}_{\text{a}}\text{+ λ}\underline{\text{r}}{}^{\text{L}}\text{, λ ≧ 0 (4)}$

With $\underline{\text{r}}{}^{\text{L}}{\text{= (r}}_{\text{H}}{}^{\text{L}}{\text{, r}}_{\text{x}}{}^{\text{L}}\text{)}$

.

, ergibt sich aus dem von der Dampftemperatur abhängigen Wärmeinhalt des Dampfs - zuführt. Die Skala an der Peripherie des hx-Diagramms erlaubt die Bestimmung der Richtung der Zustandstrajektorie aus diesem Verhältnis zwischen Enthalpie- und Feuchtezufuhr. Für die Trajektorie ergibt sich

${\text{h}}_{\text{aus}}{\text{= h}}_{\text{ein}}{\text{+ λh}}_{\text{D}}$

${\text{X}}_{\text{aus}}{\text{= x}}_{\text{ein}}\text{+ λ}$

mit λ≧0 bzw.

${\text{h}}_{\text{aus}}{\text{= h}}_{\text{ein}}{\text{+ λr}}_{\text{h}}{\text{}}^{\text{D}}\text{ (5a)}$

${\text{x}}_{\text{aus}}{\text{= x}}_{\text{ein}}{\text{+ λr}}_{\text{x}}{\text{}}^{\text{D}}\text{ (5b)}$

mit λ≧0, wobei ${\text{r}}_{\text{h}}{\text{}}^{\text{D}}{\text{=h}}_{\text{D}}$

, ${\text{r}}_{\text{x}}{\text{}}^{\text{D}}\text{=1}$

, zusammengefasst

$\underline{\text{ξ}}{\text{}}_{\text{aus}}\text{=}\underline{\text{ξ}}{\text{}}_{\text{ein}}\text{+ λ}\underline{\text{r}}{\text{}}^{\text{D}}\text{, λ≧0 (5)}$

mit $\underline{\text{r}}{\text{}}^{\text{D}}{\text{=(r}}_{\text{h}}{\text{}}^{\text{D}}{\text{,r}}_{\text{x}}{\text{}}^{\text{D}}\text{)}$

.If the humidifier 8 is a steam humidifier (FIG. 6), the enthalpy of the water vapor supplied can be considerably higher than the air enthalpy, so that it not only contains moisture, but also enthalpy, namely in a proportion that is approximately proportional to the air mass in relation to the air mass - the proportionality factor, the specific heat ${\text{H}}_{\text{D}}\text{= Δh / Δx}$

, results from the heat content of the steam, which is dependent on the steam temperature. The scale on the periphery of the hx diagram allows the direction of the state trajectory to be determined from this relationship between enthalpy and moisture supply. For the trajectory we get

${\text{H}}_{\text{out}}{\text{= h}}_{\text{a}}{\text{+ λh}}_{\text{D}}$

${\text{X}}_{\text{out}}{\text{= x}}_{\text{a}}\text{+ λ}$

with λ ≧ 0 or

${\text{H}}_{\text{out}}{\text{= h}}_{\text{a}}{\text{+ λr}}_{\text{H}}{}^{\text{D}}\text{(5a)}$

${\text{x}}_{\text{out}}{\text{= x}}_{\text{a}}{\text{+ λr}}_{\text{x}}{}^{\text{D}}\text{(5b)}$

with λ ≧ 0, where ${\text{r}}_{\text{H}}{}^{\text{D}}{\text{= h}}_{\text{D}}$

, ${\text{r}}_{\text{x}}{}^{\text{D}}\text{= 1}$

, summarized

$\underline{\text{ξ}}{}_{\text{out}}\text{=}\underline{\text{ξ}}{}_{\text{a}}\text{+ λ}\underline{\text{r}}{}^{\text{D}}\text{, λ ≧ 0 (5)}$

With $\underline{\text{r}}{}^{\text{D}}{\text{= (r}}_{\text{H}}{}^{\text{D}}{\text{, r}}_{\text{x}}{}^{\text{D}}\text{)}$

.

zusammengefasst, sodass sich die erforderlichen Berechnungen einfach und übersichtlich gestalten und problemlos an die Konfiguration der jeweiligen Anlage angepasst werden können.For all aggregates, equations (1) - (5), in components (1a), (1b) - (5a), (5b), formally largely analogous descriptions of the state trajectories, the equations have the same structure regardless of the aggregate on. The specific for an aggregate is in the vector $\underline{\text{r}}{\text{= (r}}_{\text{H}}{\text{, r}}_{\text{x}}\text{)}$

summarized so that the required calculations are simple and clear and can be easily adapted to the configuration of the respective system.

The units themselves have long been known in air conditioning technology and are familiar to any specialist. They are therefore not shown in detail here.

The state trajectories, as can be seen from the above explanations, with the exception of part of the trajectory of the cooler 7, are represented throughout by straight lines. However, the method according to the invention readily offers the possibility of also working with non-linear state trajectories. At most, this increases the computing effort somewhat.

In the following, several constellations of outside air condition (full circle), Circulating air status (empty circle) and target status of the supply air (x) are shown and shown, in which ways the target status can be achieved and which of the possible transitions is to be selected. It is assumed that an air conditioning system of the configuration shown schematically in FIG. 1 is used, an air washer (FIGS. 7-9) or a steam humidifier (FIG. 10) being used as the humidifier.

For each possible transition to the target state, consisting of a plurality of successive partial transitions, which are produced by units arranged one behind the other in the flow direction, an amount of effort is determined which reflects the corresponding energy and / or cost.

The effort size is calculated from partial effort sizes, usually by adding them, which are assigned to the individual partial transitions. In the simplest case, a partial transition can be attributed to the absolute value of the enthalpy difference overcome as long as it is not nearly energy-neutral, such as in the mixing chamber - the use of such units is automatically preferred. In the examples described below, this type of calculation is mostly used for the sake of simplicity. However, it is also possible to multiply said absolute value by a cost factor assigned to the respective aggregate or to use more complicated calculation methods which take into account, for example, different efficiencies of an aggregate in different temperature and humidity ranges.

The basic procedure for determining the possible transitions to the target state is always the same, however, a certain preselection can be made according to the mutual position of the above-mentioned air conditions. A first state trajectory, which corresponds to a first unit, and a second state trajectory, which corresponds to the first unit, is determined in each case from an initial state which corresponds to the outside air state or also from a modified initial state produced by maximum admissible ambient air admixture in the mixing chamber 5 subordinate second unit corresponds and leads to the target state.

If the trajectories intersect in a sectional state, as is shown, for example, in FIG. 7, the use of the first and the second aggregate offers a possibility of bringing about the transition from the initial state to the desired state. The cutting state can then be determined by the computer - in most cases this is very simple, since the state trajectories are straight and therefore only a linear system of equations has to be solved. If the transition is selected, one of the units is regulated according to the moisture, i.e. H. its manipulated variable is set so that the humidity of the supply air emitted by the air conditioning system 1, which is monitored by the moisture meter 11c on the supply air extractor 4, corresponds to the setpoint humidity, the other according to the temperature, i. that is, the unit is regulated according to the supply air temperature monitored by the temperature sensor 11c on the supply air extractor 4.

If the second state trajectory does not intersect the first state trajectory, but rather, as shown in FIG. 9, the saturation curve at a point subsequently referred to as the second cutting state, an intermediate unit arranged between the first unit and the second unit can be selected and a corresponding intermediate state trajectory be determined which leads to the second cut state. If the intermediate state trajectory and the first state trajectory intersect in a first cutting state, the two cutting states can likewise be determined by the computer. If such a transition is selected, the first and the second aggregate are regulated according to humidity and temperature, while the intermediate aggregate is controlled so that the saturation line is reached.

This determination of possible transitions is simple, manageable and flexible. The computing effort is low and hardly dependent on the situation.

The air conditioning system 1 with an air washer as a humidifier essentially has the following possible control combinations, of which one or more, depending on the relative position of the air conditions, always represent possible transitions: M V K B N A f t a a a B f a t a a C. f a a a t D t a a f a E ma t a f a F mi t a f a G ma a t f a H mi a t f a I. ma a f a t J mi a f a t K ma f a ma t L mi f a ma t M ma a a f t N mi a a f t

M means mixing chamber, V preheater, K cooler, B humidifier and N postwarmer. a stands for out of service, d. H. the air condition is not changed. In the case of the mixing chamber, ma means the maximum proportion of outside air, i.e. H. no recirculated air is mixed in, with a minimal proportion of outside air, i. H. the maximum permissible proportion of recirculated air is added. Formal, i.e. H. With regard to the equations (1a), (1b), (1) - (5a), (5b), (5), which describe the behavior of the units, the state of the maximum outside air fraction, denoted by ma, corresponds to the outside fraction denoted by a. Operating state of the other units, corresponding to λ = 0. For the humidifier, ma means that the maximum water vapor content, i.e. H. until the saturation line is reached. f means that the unit is regulated according to the humidity, t that it is regulated according to the temperature.

$\underline{\text{ξ}}{\text{}}_{\text{soll}}\text{=}\underline{\text{ξ}}{\text{}}_{\text{S}}{\text{+ λ}}^{\text{L}}\underline{\text{r}}{\text{}}^{\text{L}}$

ergibt. In Komponenten (s. Gleichungen (1a),(1b), (5a),(5b)):

${\text{h}}_{\text{S}}{\text{= h}}_{\text{aussen}}{\text{+ λ}}^{\text{M}}{\text{r}}_{\text{h}}{\text{}}^{\text{M}}$

${\text{x}}_{\text{S}}{\text{= x}}_{\text{aussen}}{\text{+ λ}}^{\text{M}}{\text{r}}_{\text{x}}{\text{}}^{\text{M}}$

${\text{h}}_{\text{soll}}{\text{= h}}_{\text{S}}{\text{+ λ}}^{\text{L}}{\text{r}}_{\text{h}}{\text{}}^{\text{L}}$

${\text{x}}_{\text{soll}}{\text{= x}}_{\text{S}}{\text{+ ≧}}^{\text{L}}{\text{r}}_{\text{x}}{\text{}}^{\text{L}}\text{.}$

Aus diesen vier Gleichungen mit den vier Unbekannten h_S, x_S, λ^M, λ^L, erhält man etwa durch einfache Umformung

${\text{h}}_{\text{soll}}{\text{-h}}_{\text{aussen}}{\text{= λ}}^{\text{M}}{\text{r}}_{\text{h}}{\text{}}^{\text{M}}{\text{+λ}}^{\text{L}}{\text{r}}_{\text{h}}{\text{}}^{\text{L}}$

${\text{x}}_{\text{soll}}{\text{-x}}_{\text{aussen}}{\text{= λ}}^{\text{M}}{\text{r}}_{\text{x}}{\text{}}^{\text{M}}{\text{+λ}}^{\text{L}}{\text{r}}_{\text{x}}{\text{}}^{\text{L}}\text{,}$

ein System von zwei Gleichungen mit zwei Unbekannten, das sich ohne weiteres nach λ^M und λ^L auflösen lässt, da die Vektoren $\underline{\text{r}}{\text{}}^{\text{M}}{\text{=(r}}_{\text{h}}{\text{}}^{\text{M}}{\text{,r}}_{\text{x}}{\text{}}^{\text{M}}\text{)}$

und $\underline{\text{r}}{\text{}}^{\text{L}}{\text{=(r}}_{\text{h}}{\text{}}^{\text{L}}{\text{,r}}_{\text{x}}{\text{}}^{\text{L}}\text{)}$

nicht parallel sind und folglich die von ihnen gebildete Matrix regulär ist. Der Uebergang entspricht Fall D in der obigen Tabelle.7 shows a constellation of the air states in which the desired state can be achieved in two ways, in which the mixing chamber 5 serves as the first unit and its state trajectory starting from the outside air state thus as the first state trajectory. The humidifier 8, an air washer, can be used as the second unit, so that the second state trajectory is a line of constant enthalpy. It intersects the first state trajectory in a cutting state S, corresponding to a point (h _S , x _S ) in the hx diagram, which can be interpreted as a vector ξ _S , which (see Equations (1), (5)) results from the Solution of the system of equations

$\underline{\text{ξ}}{}_{\text{S}}\text{=}\underline{\text{ξ}}{}_{\text{Outside}}{\text{+ λ}}^{\text{M}}\underline{\text{r}}{}^{\text{M}}$

$\underline{\text{ξ}}{}_{\text{should}}\text{=}\underline{\text{ξ}}{}_{\text{S}}{\text{+ λ}}^{\text{L}}\underline{\text{r}}{}^{\text{L}}$

results. In components (see equations (1a), (1b), (5a), (5b)):

${\text{H}}_{\text{S}}{\text{= h}}_{\text{Outside}}{\text{+ λ}}^{\text{M}}{\text{r}}_{\text{H}}{}^{\text{M}}$

${\text{x}}_{\text{S}}{\text{= x}}_{\text{Outside}}{\text{+ λ}}^{\text{M}}{\text{r}}_{\text{x}}{}^{\text{M}}$

${\text{H}}_{\text{should}}{\text{= h}}_{\text{S}}{\text{+ λ}}^{\text{L}}{\text{r}}_{\text{H}}{}^{\text{L}}$

${\text{x}}_{\text{should}}{\text{= x}}_{\text{S}}{\text{+ ≧}}^{\text{L}}{\text{r}}_{\text{x}}{}^{\text{L}}\text{.}$

From these four equations with the four unknowns h _S , x _S , λ ^M , λ ^L , one obtains, for example, by simple transformation

${\text{H}}_{\text{should}}{\text{-H}}_{\text{Outside}}{\text{= λ}}^{\text{M}}{\text{r}}_{\text{H}}{}^{\text{M}}{\text{+ λ}}^{\text{L}}{\text{r}}_{\text{H}}{}^{\text{L}}$

${\text{x}}_{\text{should}}{\text{-x}}_{\text{Outside}}{\text{= λ}}^{\text{M}}{\text{r}}_{\text{x}}{}^{\text{M}}{\text{+ λ}}^{\text{L}}{\text{r}}_{\text{x}}{}^{\text{L}}\text{,}$

a system of two equations with two unknowns, which can easily be solved for λ ^M and λ ^L because the vectors $\underline{\text{r}}{}^{\text{M}}{\text{= (r}}_{\text{H}}{}^{\text{M}}{\text{, r}}_{\text{x}}{}^{\text{M}}\text{)}$

and $\underline{\text{r}}{}^{\text{L}}{\text{= (r}}_{\text{H}}{}^{\text{L}}{\text{, r}}_{\text{x}}{}^{\text{L}}\text{)}$

are not parallel and consequently the matrix they form is regular. The transition corresponds to case D in the table above.

Instead of the humidifier 8, the cooler 7 can also be used as the second unit. In this case, the second state trajectory - a line of constant moisture - intersects the first state trajectory in a cutting state S '(case B). The solution is determined in an analogous manner.

Another possibility is the use of the preheater 6 as the first and the humidifier 8 as the second unit (case E, sectional state S ″).

It is also possible to produce a modified starting point by admixing the maximum admissible ambient air in accordance with the minimum proportion of outside air in the mixing chamber 5, using the cooler 7 as the first unit and the reheater 9 as the second unit (case J).

In principle, all possible control combinations are calculated. However, it is also conceivable to exclude certain, for example energetically very unfavorable, options, such as the simultaneous operation of preheater and cooler, from the outset.

Because the air washer does not give off heat to the air or withdraws the same, but only circulates water, its energy consumption is very low, while the cooler 7 would have to extract enthalpy from the air with the corresponding expenditure of energy, so that the transition by means of the combination of the temperature-controlled mixing chamber 5 with the humidifier 8 controlled by the humidity with respect to the energy consumption represents the cheapest variant and is selected.

Fig. 8 shows a constellation in which the target humidity is lower than outside air and recirculating air humidity. It is therefore essential to use the cooler 7 as a dehumidifier. The mixing chamber 5 can be put out of operation so that the initial state corresponds to the outside air state (case I) or it can be used to produce a modified initial state (indicated by a cross line) with a minimal proportion of outside air (case J). In the configuration shown, the enthalpy difference to be overcome by the cooler 7 is smaller in the second case than in the first, so that since the enthalpy difference to be overcome by the reheater 9 as the second unit is the same in both cases, this variant is selected.

In the constellation according to FIG. 9, the nominal humidity is higher than the outside air humidity and this is higher than the circulating air humidity. Using the mixing chamber 5 would bring no profit under these circumstances. It is possible to use the preheater 6 as the first unit and the humidifier 8 as the second unit. The corresponding trajectories intersect in a section state S (case E).

ergibt. Der Befeuchter 8 als Zwischenaggregat und der Vorwärmer 6 als erstes Aggregat führen zu einem ersten Schnittpunkt S1', dessen Berechnung zu der im Zusammenhang mit Fig. 7 erläuterten völlig analog ist, wobei nur ξ _s2' an die Stelle von ξ _soll tritt. Somit ergibt sich ein weiterer möglicher Uebergang (Fall K).When the reheater 9 is used as the second unit, the second state trajectory intersects the saturation line in a second cutting state S2 ', which in the present case is very simple in terms of calculation as

$\underline{\text{ξ}}{}_{\text{s2 '}}{\text{= (h}}_{\text{sat}}{\text{(x}}_{\text{should}}{\text{), x}}_{\text{should}}\text{)}$

results. The humidifier 8 as an intermediate unit and the preheater 6 as the first unit lead to a first intersection point S1 ', the calculation of which is completely analogous to that explained in connection with FIG. 7, only ξ _s2' taking the place of ξ _soll . This results in another possible transition (case K).

The sum of the absolute values of the enthalpy differences is the same in both cases, so that this criterion does not allow a decision between the two possible transitions. However, the method according to the invention makes it possible to carry out a refined calculation of the partial effort sizes, which takes into account, for example, that higher heat losses occur at higher temperatures, so that the efficiency of preheaters and postheaters is reduced. Such a refinement in the calculation of the effort size leads to a decision for the second of the possible transitions.

10 shows possible transitions when a steam humidifier is used as the humidifier 8. Use of the mixing chamber 5 as the first unit and the preheater 6 or post-heater 9 as the second unit (cases A and C, sectional state S) is less energy-efficient than using the preheater 6 the first and the humidifier 8 as a second unit (case D, cut state S ') or the energetically equivalent possibility of using the humidifier 8 as the first and the reheater 9 as a second unit (case M, cut state S' '). A decision between the latter variants is only possible on the basis of additional or refined criteria.

The air conditioner 1 described (Fig. 1) of course provides is only an example. It could contain other or further aggregates without having to change the control method and the basic calculation method. Examples are: air washers with variable water temperatures, air dryers using the absorption method, rotary heat exchangers or other units for heat recovery.

Claims (7)

Method for controlling an air conditioning system (1), which takes up air of at least one initial state determined by an initial temperature and an initial humidity and releases air of a desired state determined by an intended temperature and an intended humidity for the supply of rooms and which regulates a number of controllable units through which the air flows With a given target state, depending on the respective initial state, certain aggregates are selected and regulated in such a way that an expense quantity reflecting the operating expenditure reaches a minimum value while the non-selected aggregates are out of operation, characterized in that possible transitions from the initial state to the target state, which in the series connection of partial transitions, each of which is accomplished by individual subordinate aggregates, are determined and the respective amount of effort is calculated, inde For each partial transition, a partial effort size is assigned and the effort size for the transition is determined from the partial effort sizes and the aggregates for managing the partial transitions, from which the transition with the smallest effort size is composed, are selected and controlled in such a way that they effect the said transition. A method according to claim 1, characterized in that the determination of the effort size for a possible transition from the partial effort sizes is carried out in each case by adding the latter. A method according to claim 1 or 2, characterized in that the amount of effort assigned to a partial transition is proportional to the absolute value of the enthalpy difference between the state before and the state after the partial transition, the proportionality factor being a function of the aggregate by means of which the partial transition is accomplished. Method according to one of claims 1 to 3, characterized in that the amount of effort assigned to a partial transition corresponds in each case to the energy used to accomplish the partial transition. Method according to one of claims 1 to 3, characterized in that the amount of effort assigned to a partial transition corresponds in each case to the costs to be accomplished to accomplish the partial transition. Method according to one of claims 1 to 5, characterized in that possible transitions are determined by in the two-dimensional state space at least one first state trajectory, consisting of the states lying outside the fog region, which can be achieved by using a first unit starting from the initial state or, if appropriate, from a mixing chamber arranged upstream of the other units by maximum admixture of modified initial air produced from the rooms, is determined - at least one second state trajectory, consisting of all states outside the fog area, from which the target state can be reached by using a second unit, if the second aggregate is arranged downstream of the first aggregate, it is determined in each case whether a cutting state (S; S ';S'') exists, on which the first state trajectory intersects the second state trajectory, - If necessary, the cutting state (S; S ';S'') is determined and the transition is determined as a series connection of a first partial transition from the initial state to the cutting state (S; S'; S '') and a second partial transition from the cutting state (S; S ';S'') to the target state, brought about by the first unit or the second unit, - Otherwise, if the second state trajectory intersects the saturation curve delimiting the fog region in a second cutting state (S2 '), at least one intermediate state trajectory is determined, consisting of all points lying outside the fog region, from which the second cutting state (S2') starts by means of a second aggregate upstream intermediate unit can be reached, in each case, if the corresponding first unit is upstream of the intermediate unit, a first cutting state (S1 '), in which the intermediate state trajectory intersects the first state trajectory, is determined and the transition is determined as a series connection of a first one Partial transition from the initial state to the first cutting state (S1 '), a second partial transition from the first cutting state (S1') to the second cutting state (S2 ') and a third partial transition from the second cutting state (S2') to the target state, accomplished by the first unit or the Intermediate unit or the second unit. Method according to one of claims 1 to 6, characterized in that the determination of possible transitions as well as the determination of the corresponding effort sizes by a computer on the basis of the target state, the initial state determined by measurements and, if appropriate, the state of admissible circulating air also determined by measurements, any boundary conditions and the Properties of the aggregates takes place.

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