FI100065B - Air conditioning equipment and method for controlling its operation - Google Patents

Abstract

A method for controlling the operation of an air-conditioning apparatus comprising devices (1, 2, 3) for supplying outdoor air (A) into a room (4), for removing indoor air (B) from the room, and for returning removed indoor air as return air (C) into the room; and devices (9, 16, 20) for adjusting the amounts of outdoor air, removed air, and return air. The adjusting devices are adjustable for controlling the mixing ratios between the air amounts according to desired air conditions to be created in the room. To achieve a greater controllability of the apparatus and to improve the accuracy of the mixing ratios, the outdoor air (A) and the return air (C) are passed into the room alternately, and the durations of the open periods of the adjusting devices are adjusted so that a desired mixing ratio is achieved between the amounts of outdoor and return air in the room. An air-conditioning apparatus developed for applying the method comprises operating means (22) arranged to open the adjusting devices (9, 20) of an outdoor air duct (5) and a return air duct (19) alternately for the duration of the open periods.

Description

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The present invention relates to a method for controlling the operation of an air-conditioning system, comprising: - a device for introducing outdoor air into a room, - a device for removing room air from a room, - a device for returning exhaust air as return air to a room, and - means for controlling outdoor air. for adjusting the amounts of exhaust air and room air returned to the room space, the control means being adjustable between a closed position preventing air passage and an open position allowing air passage 15, - adjusting means for adjusting the mixing ratios of said air volumes to the desired room condition.

The need for ventilation in buildings varies depending on the number of people in the 20 buildings at any given time, the amount of pollutants entering the air, the heat load, etc. The ventilation system, especially its airflow, naturally has to be dimensioned according to maximum load. As the sizing factor is very often the heat load, • ventilation, especially in winter, has to be used at an unnecessarily high power if the power cannot be adjusted. This would unnecessarily consume a very large amount of thermal energy, especially because the cold outdoor air brought into the building in any way must be heated.

30 In order to avoid unnecessary energy consumption, various ways have been developed to control the efficiency of the ventilation system. The most natural way is to simultaneously reduce the supply and exhaust air flow of the air conditioning system when full power is not required. This can be done, for example, by adjusting the speed of the fans, changing the performance curves of the fans by adjusting the blade angle, or by bringing the air entering the fan into rotation. with wiring controls or simply by increasing the air resistance of the system with dampers.

5 However, reducing the airflow causes problems with the distribution of air in the rooms. The characteristics of conventional air and air devices, in particular the so-called throw length, change as the airflow decreases so that the airflow discharged from the air distributor does not extend into the entire room 10, but in some rooms the air does not change at all. The situation is particularly critical when the supply air temperature differs from the room air temperature. If the supply air is colder than room air, it will easily “fall” to the floor level and cause traction in addition to poor air exchange at the breathing-15 level. If the supply air is warmer than the room air, it stays (or rises) to the top of the room and usually exits directly through the exhaust valve there, so that the air at the actual living level does not change at all (so-called short-circuit flow).

20 In addition to this general problem, each of the above control methods has its own special problems. Otherwise, trouble-free rotation speed control is very expensive as well as wing angle control. When adjusting the blade angle, low airflows can cause the fan characteristic to become unstable; 25 parts, in which case in the worst case the so-called pumping phenomenon (hunting): the fan airflow varies several times per second, which can result in strong pressure shocks and sound generation. The risk of pumping is particularly significant when the response curve of the air conditioning system is not a square parabola. This risk, although clearly lower, is also present in the control of the control vane and damper, for example the air flow of axial fans can only be controlled by the damper in a very small air flow range.

li 3 100065 Mainly to eliminate air distribution problems, a so-called return air operation. In recirculated air use, the building's outdoor air flow and the so-called the waste air flow is reduced by means of control dampers, but the sa-5 club is directed part of the exhaust air flow after the fan to the suction side of the supply air fan, where it mixes with the outdoor air flow sucked by the fans. The aim is to keep the proportion of the exhaust air flow returned to the building equal to the reduction in the outdoor and / or exhaust air flow caused by the damper. In this case, the supply and exhaust air fan and the air distribution devices operate at all times with the rated air flow, and the problems described above do not occur in their operation.

In principle, the return air system looks simple-15, but in reality, as soon as the return air damper is opened to direct the exhaust air to the supply air fan, completely separate exhaust and supply air systems form one very complex and difficult-to-control airflow system. experience shows no control at all. Determining the whole field of problems would require a very broad and complex description, so the following is only a basic description of the problems encountered and the consequences that; There are 25 uncontrollable situations.

One of the most serious problems in practice is that the outdoor air flow, which is critical for human health, is not achieved. Commonly used minimum outdoor air flow protection devices based on limiting the position of the outdoor air game do not even guarantee that no outdoor air enters the system at all, let alone ensuring the minimum outdoor air flow. The situation is further complicated by the fact that the air flows in the different parts of the system vary according to the required control range and the air flows 35 should be controlled over the entire air flow range.

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The situation might still be somehow manageable if there was a constant relationship between the airflow and the position of the damper, or if it even followed some mathematical equation. Unfortunately, this is not the case, but the adjustment curves of the dampers 5 depend in a rather complex way on the shape of the adjustment louver, the end face speed and the position of the louver. The control curves must always be determined experimentally.

Air conditioner manufacturers supply mixing components as standardized standard solutions, the properties of which 10 are in no way changeable and for which, as a whole, no performance values are usually reported. The stated performance values are generally for dampers intended to be installed in separate ducts, and even their accuracy when installed in the mixing section has not been ensured in any way or no limit values have been given for the characteristics of the system to be controlled.

There have been numerous cases where fan motors have not remained on with recirculated air-20 operation due to the increase in airflow and the resulting increase in electrical power. Numerous measurements have shown that despite the limitations of the damper position, the minimum outdoor air flow is not achieved. In some cases, the pressure ratios in the building have been so badly disturbed by the use of return air that the exterior doors have not been easily opened. This has led to the abandonment of the use of return air altogether by many researchers, construction supervisors, etc. These requirements have been exacerbated by the problems of the mixing process itself, especially when the exhaust air is humid either due to the volatile moisture in the building or the humidification of the supply air. In practice, condensation and frost have formed in the mixing sections, at worst they have frozen in the face of cold outside air and moist return air. The situation has apparently been exacerbated by poor airflow management. The test component, which works flawlessly in laboratory tests when mixing "correct" airflows at "correct" speeds, can in practice cause great difficulties when "wrong" airflows are mixed at "wrong" speeds due to poor airflow control.

5 Poor operation of the mixing section also endangers the operation of the air conditioning parts after the section. Due to the uneven speed and / or temperature distribution, the heating coil does not reach its rated performance values or its resistance increases. There are even known cases where the radiator is frozen-10 now due to poor operation of the mixing section. The resistance of the filter section increases and the service life is shortened, droplets are released from the humidifying parts or cooling coils into the air stream causing moisture and hygiene problems, their resistance increases and performance deteriorates, etc. An uncontrolled component simply degrades the performance of any downstream air conditioner.

The object of the present invention is to provide a method which avoids the above-mentioned drawbacks and enables the controlled operation of the air-conditioning equipment. This object is achieved by the method according to the invention, which is characterized in that the outdoor air and the return air are introduced into the room alternately and that the opening times of the control means are adjusted to correspond to the desired mixing ratio of the outdoor air and return air volumes in the room.

The basic idea of the invention is that the inlet device and the return device are used alternately periodically for such a time that the desired mixing ratio between the outdoor air and the return air is achieved in the room.

It is also an object of the invention to provide a controlled air conditioning system in which the desired airflows and mixing ratios are achieved with high accuracy, minimum outdoor airflow is achieved in all conditions, building pressure ratios are maintained at all operating points, the mixing process does not cause problems in the mixing section itself and does not interfere with and the hardware required for adjustment is substantially simplified.

The basic idea of the invention is that the operation of the mixing section (return device) is dimensioned to be controlled according to the characteristics of the system only in two or a limited number of operating points of the mixing section, and the mixing section is used with on / off control only at these operating points. The desired mixing ratio is obtained by adjusting the length of time that the operating points operate.

10 In its simplest form, the system operates as a 2-position control, so that only the outdoor air device is used intermittently, i.e. only outdoor air or only the return air device is supplied to the room, so that only return air is supplied to the room. The desired mixing ratio, i.e. the ratio of the outdoor air flow to the return air flow, is achieved by adjusting the length of the operating cycles. Thus, for example, if half of the total air flow to the room is desired, half of the return air is present, the control dampers of the return device are half open all the time and half closed. If the minimum outdoor air flow requirement is, for example, 30% of the total air flow, the outdoor air damper is open 30% of the total time.

Since a very high accuracy is easily achieved in measuring the time, the desired mixing ratio 25 is achieved with a very high accuracy: in practice the deviation is less than 0.5%. The control message is obtained in the same way as in current systems on the basis of the occupancy rate of the building, air purity or temperature, outdoor temperature, etc. Instead, control motors are simple on / off-motors that are significantly cheaper and more reliable than the relatively controllable motors currently in use. The control logic is also slightly simplified.

In addition to ensuring that the minimum outdoor air flow is achieved, the difficulties associated with the mixing process itself, such as condensation, freezing and

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7 100065, uneven temperature distribution, etc., because two air currents of different temperatures are not mixed. It is easy to ascertain in the laboratory test only that the function of the parts after the mixing section is not disturbed at only two operating points, where the effect of the uneven temperature distribution does not have to be taken into account.

The invention will be described in more detail below with reference to the accompanying drawings, in which Figures 1 and 2 schematically show a preferred embodiment of the air conditioning apparatus according to the invention 10 in outdoor air flow and return air flow operation, and Figures 3 and 4 show alternative embodiments of air conditioning apparatus.

The air conditioning apparatus shown in Fig. 1 of the drawings includes an inlet device 1, an outlet device 2 and a return device 3.

The supply device 1 comprises an supply air duct 5 leading from the outside air to the room 4, in which a damper 6, 20 a filter 7, a heat recovery 8, a damper 9 and heating and cooling coils 10, 11 and a fan 12 are installed.

The exhaust device 2 comprises an exhaust air duct 13 leading from the room to the outside air, in which a filter 25 14, a fan 15 and control dampers 16, a heat exchanger 17 and a control damper 18 are installed. The fan generates an exhaust air flow B in the duct.

The return device 3 comprises a return air duct 19 in which a damper 20 is installed. A return air flow C of exhaust air 30 flows through the duct.

The dampers 9, 16 and 20 are connected to actuators 21 which set the dampers to different operating positions, in this example between the closed position and the open position. The actuators are controlled by adjustable time switches 22 35, which can be used to adjust the opening hours of the dampers.

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The operation of the return device 3 is then dimensioned to be controlled according to the characteristics of the system at only two operating points of the return device. The air conditioner shown here functions as a 2-position control so that only outdoor air A or only return air C is supplied to the room 5 alternately during different operating periods. In the former case, the inlet dampers 6 and 9 and the outlet dampers 16 and 18 are fully open and the return damper 20 fully closed. In the latter case, the dampers 6 and 9 of the inlet device and the dampers 16 and 18 of the outlet device are completely closed and the damper 20 of the return device is fully open. The desired mixing ratio, i.e. the ratio of the outdoor air volume and the return air volume from the room space, is achieved by adjusting the length of the different operating cycles, i.e. the opening time of the dampers. If it is desired that 50% of the total air flow into the room is outside air A and 50% is return air C, the dampers are half open and half closed all the time. If, on the other hand, it is desired that the minimum outdoor air volume be 30% of the total air volume, the inlet dampers 6 and 9 20 must be kept open for 30% of the total time with the return duct damper 20 closed during this time.

Since the operating modes of the dampers can be easily and precisely controlled by the timers 22, the desired mixing ratio is achieved with very high accuracy. The actuators 21 are preferably on-off control motors.

It is noted that in the air conditioning system, the mixing of the outdoor air flow and the return air flow does not take place in the equipment itself, but only in the room space, because different air flows are alternately introduced into the room space for the desired length of operation.

As stated above, the total airflow tends to increase in return air operation because the resistance of the damper 20 is considerably lower than the combined resistance of the elements 16, 17, 18 and 6, 7, 8, 9. This can result in overloading of the 35 fan motors, noise and traction problems in air-conditioned rooms, etc.

Il 9 100065 This difficulty can be avoided and the total air flow constant by measuring the damper 20 so small that its resistance is sufficient in the open position, or by limiting its open position so that the desired resistance 5 is reached. However, it is more advantageous to place in connection with the damper 20 a part 23 causing a single resistance, which equalizes the air flow. The part can be a perforated plate or a nozzle plate, the free surface area of the openings of which can be selected or adjusted to the desired size, a series of plates 10, the slits between which can be adjusted by changing the mutual position of the plates, or a device known per se.

In this way, a very important improvement over the current state of the art has also been achieved: the operation of the mixing section is controllable and the desired performance values can be dimensioned in advance to meet the requirements of the respective plant, and the equipment can be completely finished at the factory. The necessary accessories are considerably cheaper than, for example, the savings achieved in the price of control motors.

20 Sometimes, however, it is not possible to run the unit with a 100% outdoor air flow, for example because the power of the radiator 10 is not sufficient in severe frosts or because the low heat efficiency and heat storage capacity of the heat recovery coils 8, 17 and the heating system • slowness and poor air distribution. the temperature variation.

The system still operates in such a way that a damper is arranged in the damper control motors, e.g. from a certain outdoor temperature or mixing ratio, which in the "ul-30 air" position allows the outdoor air and exhaust air dampers 6,; 9, 16, 18 to open only to a position corresponding to e.g. 70% outdoor air flow but to the position and the return air damper 20 to a position corresponding to 30% return air flow (= controlled operating point). The opening time must be extended accordingly by 35 times the time corresponding to 100% airflow by a split-35 miles.

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The air flow ratios are maintained and can be dimensioned in this case as well, but instead of one resistor, three flow resistors must be dimensioned, although dampers 6, 9, 16, 18 at only one operating point but damper 20 at two points corresponding to 5, 100% and 30% air flow. Dimensioning becomes more difficult, although easy compared to current systems.

In this case, it is necessary to mix cold and warm, possibly even humid air. However, a significant relief compared to current 10 systems is that operation only needs to be checked at two operating points where airflows are controlled, so the number of laboratory tests is limited and it can be relied on that a well-functioning laboratory will work in practice and with a reasonable number of tests. even the humidity, temperature and mixing ratio limits within which the humidification section works properly.

A very good result is obtained if, instead of the conventional heat transfer technique, the system according to Fig. 3 20 is used, in which all the thermal engineering functions are combined in one heat exchanger. Its operation is described in more detail in FI patent application 915511.

When using the circuit according to Figure 3 system is to some extent self-stabilizing: the transition. 25, for example for outdoor use return air for the fluid circuit is of large liquid volumes and heat surfaces makes for a while, heat recovery-like manner, i.e., first to cool the exhaust air side of the heat exchanger 17 'of the air and warms it back into the supply air side patte-30 buffer 8. '. Since there is no risk of freezing, the adjustment can be arranged; arranges proactively so that the valve 24 shuts off the heat supply simultaneously or slightly before the return air damper 20 begins to open. In this case, the temperature of the supply air when switching to return air operation first decreases slightly, 35 then rises slightly and then returns to the same as 11 100065 room temperature. Since the maximum temperature difference between the supply air and the heating fluid flowing in the heat transfer circuit is well below 10 ° C, the fluctuation of the supply air temperature remains small, especially compared to conventional heat transfer systems with a temperature difference of 40-50 ° C.

Because the temperature of the return air has been lowered prior to mixing, mixing it and the outside air is substantially easier than in conventional systems; temperature deposition is less likely to occur, the risk of freezing and condensation is reduced, etc.

This arrangement achieves another essential advantage. When the return air damper 20 is placed "outside" the heat transfer devices, the air resistances caused by the elements 16, 17, 18 and 6, 7, 8, 9 of Fig. 2 are reduced by the resistance of the parts 8 and 17, i.e. at least 150 Pa. This means, firstly, that the resistance of the system changes considerably less when switching to return air operation than in conventional systems, i.e. the airflow changes less. The difference is at least 300 Pa, so really 20 significant. On the other hand, the proportion of said resistors 18 and 7 increases substantially, i.e. the system becomes much easier to adjust. The effect on the operation of the damper 20 is particularly strong. The principle can, of course, also be used in the conventional system according to Figure 1.

One embodiment of the system is a return air operation with a supply air fan only, as shown in Figure 4. In this case, the return air is taken directly from the exhaust duct 13 or from the return duct 30 separately provided for this purpose directly to the suction side of the supply air fan 12. The exhaust hall 15 is completely stopped for the return air period. This saves the electrical power consumed by the exhaust fan, which can be significant. However, the proportion of return air in the total air flow can be infinitely adjusted between 0 and 35 by adjusting the length of the 100% operating cycles. The use of return air 12 100065 is also possible in plants where the exhaust and supply air fans are far apart.

The presented embodiments are only examples of how the basic idea of the invention is applied in practice. The II-5 exchange system, its components and functions, etc. may, of course, vary within the scope of the prior art.

Claims (8)

A method for controlling the function of an air conditioner comprising: - a device (1) for introducing external air (A) into a room space (4), - a device (2) for removing room air (B) from the room space - a device (3) for returning removed room air such as return air (C) to the room space, and - control means (9, 16, 20) for controlling the amounts of external air removed from the room space and to the room space, which regulators are adjustable between an air passage preventive locking position and an air passage permitting opening position, - wherein the regulators are installed for controlling the mutual mixing ratios of said airflows to correspond to the desired state in the room space, characterized in that the outer air (A) and the return air (C) is introduced into the room space (4) in turn and the opening hours of the regulators (9, 16, 20) are regulated to counteract the desired mixing ratio of the outside air and the return air volumes in the room space. 25 2. A method according to claim 1, characterized in that the function of the feeding device (3) is dimensioned controlled in certain of the actuators (9, 16, 20), preferably in two operating positions and that the actuators are adjusted only in these operating positions. 30 3. A method according to claim 1 or 2, characterized in that the regulating means (9, 16, 20) are set such that the regulating means (9) for external air (A) and the regulating means (20) for return air (C) are located. alternately in the open position and in the interlocking position in order to achieve the desired conditions of the outer air and the return air during the desired opening time. 17 100065 An air conditioner for a room space, comprising: - a connection device (1) for introducing external air (A) into a room space (4) and with an inlet duct 5 (5) between the outer and the room space, a device (12) for generating an exterior air flow in the inlet duct and controls (9) for controlling the exterior air flow, - an outlet device (2) for conducting outlet air (B) from the room space and with an outlet room duct (13) from the room space, a means (15) ) for generating an outlet air flow in the outlet duct and regulators (16) for controlling the exhaust air flow - an return device (3) for returning the exhaust air to the room space such as the return air (C) and with a return duct and the outlet duct (19) between (20) for regulating the outlet air flow flowing in the feed duct, and - actuating means (21) for adjusting the control air flow. The opening opening of the unit, characterized in that the actuators (21) are arranged to open the actuators (9, 20) of the inlet duct (5) and the supply duct (13) alternately during opening pouring periods corresponding to those of the outer air and the return air in each case. mixing ratio in the room (4). 5. Air conditioning apparatus according to claim 4, characterized in that the function of the return device (3) is dimensionally controlled in the at least two operating positions of the control means (9, 16, 20), preferably in a locking position and in an open position and the actuating means ( 22) are arranged to adjust the actuators (9, 20) of the inlet duct (5) and the return duct (19) only in these operating positions in turns for a long period of time, such as the provision of the inlet and inlet (4) the desired relative airflow of the return air quantities requires. 6. A method according to claim 4 or 5, characterized in that, in addition to the control means (20), the return duct 5 (19) is provided with resistors (23) for controlling the flow resistance acting on the return air flow flowing through the duct (C). 7. A method according to claim 5, characterized in that said operating positions for the control means (9, 20) of the inlet duct (5) and the feed duct (19) differ from their fully closed position and / or fully open position. Method according to any one of claims 4-7, 15, characterized in that the return channel (19) is connected to the outlet channel (13) before the second operating means (14, 15, 17 ', 18) of the outlet channel and to the inlet channel (5). the suction side of its fan (12). Il