METHOD AND APPARATUS FOR THE CONTROL OF AIR FLOWS AND PRESSURES IN AIR-CONDITIONING

Abstract: The invention relates to a method and apparatus for controlling the fresh-air, input-air, exhaust-air, waste-air and return-air flows, as well as the air pressure in the input-air duct and the air pressure in the exhaust-air duct, in an air-conditioning system which comprises at least input-air and waste-air flow meters (6, 20), input-air and exhaust-air pressure meters (12, 19), an input-air fan (5) with its air-flow control (13), a waste-air or exhaust-air fan (18) with its air-flow control (14), a fresh-air flow meter (15), a heat recovery exchanger (4), closing and control mechanisms for exhaust air and return air, coupled together as an outlet-air mechanism (10), and closing and control mechanisms for fresh air and fresh-air bypass, coupled together as an intake-air mechanism (3). The controls (13, 14) work together, and they have been fitted to act on the fans (5, 18) and mechanisms (3, 10) so that a change in one of the quantities measured will cause the adjustment of some air flow and/or mechanism (3, 10) so that the ratio (A/B) or difference (A-D) of certain air flows will be at the predetermined value, or/and that the bypass flow (F) will open or close.

Description: Method and apparatus for the control of air flows and pres¬ sures in air-conditioning The object of the invention is a method and apparatus for the control of the fresh-air, input-air, exhaust-air, waste-air and return-air flows, as well as of the air pres¬ sure in the input-air duct and the air pressure in the exhaust-air duct, in an air-conditioning system in which the closing and control mechanisms for the fresh air and fresh-air bypass in relation to the heat recovery exchanger are coupled to each other as an intake-air mechanism and, respectively, the closing and control mechanisms for the exhaust air and return air are coupled to each other as an outlet-air mechanism. There are two basic types of air-conditioning systems: constant-flow systems and flow-rate controllable systems. The constant-flow systems usually have one or two different operating rates, typically 1/1 rate and 1/2 rate. In the constant-flow systems, the air flow is not regulated at all after a certain basic setting. For this reason the air flow will change during use as the filters of the air- conditioning system become soiled, as the heating radiator becomes soiled owing to the oil condensed on the cooling radiator, and as the heat recovery exchanger freezes. The air flow will also change owing to, for example, the ther¬ mal forces caused in the air-conditioning ducts by the temperature difference between the fresh air and the inside air, or by wind. Also, the air flow in a constant-flow system is not adjusted according to pressure changes in the duct system. Thus the air flows of the air-conditioning plant vary depending on the season of the year, the condi¬ tion of the filters, and the shape of the characteristic curves of the fans and the duct system. The fresh-air flow and the waste-air flow vary independently of each other. Flow-rate controllable systems are nowadays always con¬ nected with a flow-rate controllable air-conditioning sys¬ tem. The objective of the control is to maintain a constant pressure in the ducts. The pressure in the duct system is measured, and on the basis of this measurement the air flow in the air-conditioning plant is adjusted according to need. The fresh-air flow and the waste-air flow in the air- conditioning system vary independently of each other. The air flows in present-day air-conditioning systems change readily when, for example, the filters become soiled or the heat recovery device freezes. The fresh-air flow and the waste-air flow change independently of each other, whereupon the pressure relations between the different parts of the building will change. The greatest disadvan¬ tage is undoubtedly the changing of the fresh-air flow and the waste-air flow independently of each other. As a conse¬ quence of this, humidity present in the indoor air in the building may condense on windows and structures, causing structural damage. Furthermore, spreading of odors around the building and drafts may also result. By the method according to the invention, a crucial remedy is obtained for the disadvantages described above. In order to achieve this, the method according to the invention is characterized in what is disclosed in the characterizing clause of Claim 1 and the apparatus is characterized in what is disclosed in the characterizing clause of Claim 10. It can be regarded as the most important advantage of the invention that the fresh-air flow and the waste-air flow in the air-conditioning system can be controlled (adjusted or maintained constant) continuously and independently of each other. In addition, in the air-conditioning system accord- ing to the invention, the controls of the pressure in the input-air duct and the pressure in the exhaust-air duct are dependent both on each other and on the fresh-air flow and the waste-air flow. It is a further advantage that the system is simple in construction. The invention is described below in detail, with reference to the accompanying drawing. Figure 1 is a schematic repre¬ sentation of an air-conditioning plant in which the system according to the invention has been installed. The indications of the air flows are as follows: A is the fresh-air flow, B is the input-air flow, C is the exhaust- air flow, D is the waste-air flow, E is the return-air flow, F is the fresh-air bypass flow of the heat recovery exchanger. A' is the fresh-air flow entering the heat re¬ covery exchanger. The input-air side of an air-conditioning system often includes, for example, the following parts: a fresh-air filter 2 in the fresh-air duct 21; the closing and control mechanisms of the fresh-air bypass, coupled to each other as an intake-air mechanism 3; a heat recovery exchanger ; an input-air fan 5, an input-air flow meter 6, an input-air pressure meter 12 in the input-air duct 1; a fresh-air flow meter 15; and various air-treatment devices such as a heat¬ ing radiator, a cooling radiator, an air-humidifier, air filters 7, 8, etc., which may be located at different points on the input-air side of the air-conditioning sys¬ tem.' Typically the input-air flow B in the duct 1 is equal to the fresh-air flow A in the duct 21. The exhaust-air side of air-conditioning system often in¬ cludes, for example, an exhaust-air filter 16 and an exhaust-air pressure meter 19 in the exhaust-air duct 9, exhaust-air and return-air closing and control mechanisms coupled to each other as an outlet-air mechanism 1Q, and a waste-air fan 11 and a waste-air flow meter 20 in the waste-air duct 22. Typically the exhaust-air flow C in the duct 9 is equal to the waste-air flow D in the duct 22. The input-air fan 5, the intake-air mechanism 3 and the outlet-air mechanism 10 are regulated by control 13, and the waste-air fan 18 by control 14. The input-air flow meter 6, the input-air pressure meter 12, and the fresh-air flow meter 15 are connected to control 13, and the exhaust- air pressure meter 19 and the waste-air flow meter 20 are connected to control 14. In addition, controls 13 and 14 are connected to each other. The intake-air mechanism 3 and the outlet-air mechanism 10, linked with the heat recovery exchanger 4, are preferably of the construction disclosed in our Finnish patent application 874 008. When the flow resistance on the input-air side 1 of the air-conditioning system for some reason increases, for example as the air filter becomes soiled, the air flow will decrease unless the input-air fan 5 is correspondingly con¬ trolled or unless the flow resistance of the input-air side is otherwise reduced correspondingly. The input-air fan 5 and the input-air flow control means 17 can be controlled by control 13 on the basis of either air-flow measurement 6 or pressure measurement 12. The measuring and the control are so arranged that an adjustment of the input-air fan 5 or of the input-air control means 17 will compensate pre¬ cisely for the error caused by the disturbance factor. In terms of control technology, the basis for this compensa¬ tion is either the difference A-D between the fresh-air flow and the waste-air flow or their ratio A/D; either one of these, or both of them in alternation, or a value some¬ where between them is maintained either constant or at a predetermined level by control 13. When the air flow has, under the effect of the above-mentioned adjustment, reached its limit value, the decreasing of the input-air flow will continue as the air filter continues to become further soiled. At this time the control 13 of the input-air fan, in accordance with the invention, will control the control 14 of the waste-air fan and/or of the waste-air flow con¬ trol means 18 in such a way that the predetermined dif¬ ference or ratio of the input-air flow B and the exhaust- air flow C will remain constant, which is essential with respect to the air-conditioned indoor space. Since, when the return-air flow E is closed, the input-air flow B is at all times precisely equal to the fresh-air flow A, this also corresponds to the maintaining of the difference A-D between the fresh-air flow and the waste-air flow, or their ratio A/D, at the predetermined level. The operation is similar if the flow resistance on the exhaust-air side 9 in the air-conditioning system for some reason increases, for example when the exhaust-air filter 16 becomes soiled, the heat recovery exchanger 4 freezes, the fire damper of the air duct system is triggered, etc. In such a case the control 14 of the waste-air fan or/and of the control means 18 of the waste-air flow will control the control 13 of the input-air fan or of the control means 17 of the input-air flow in such a way that the difference A-D between the fresh-air flow A and the waste-air flow D, or their ratio A/D, or a value somewhere between them will remain constant or at the predetermined value. When the waste-air flow D decreases to a value lower than the predetermined value, and the outside temperature is at the same time lower than the predetermined value, the in¬ take-air mechanism 3 adjusts to a position in which the fresh-air flow A in its entirety is fresh-air bypass flow F, i.e. the fresh-air flow A' through the heat recovery exchanger is cut off. As a consequence of this, the waste- air flow begins to thaw the heat recovery exchanger 4, if this has frozen. When the waste-air flow has risen back to its predetermined value and/or the predetermined time has elapsed from the cutting off of the air-flow A' , the intake-air mechanism 3 will switch back to its initial position, in which there is no fresh-air bypass flow F. This chain of steps can be repeated a predetermined number of times, typically 2-3 times. If the waste-air flow has not thereby risen back to its predetermined value, an alarm signal of an error operation will be given. When it is desired to change the fresh-air flow A to be smaller than the input-air flow B, and a predetermined ratio A/B is- desired as their ratio, part of the exhaust- air flow C is directed by means of the outlet-air mechanism 10 as a return-air flow E to serve as input air B. In this case, after a changing of the position of the outlet-air mechanism 10, the input-air flow B or the pressure in the input-air duct 1 is adjusted to a predetermined value. Thereafter the waste-air fan 11 or the waste-air flow con¬ trol means 18 is adjusted so that the difference A-D be¬ tween the measured values of the fresh-air flow and the waste-air flow, or their ratio A/D, will become the pre¬ determined constant value. If thereafter the input-air flow B or the pressure in the input-air duct 1 does not deviate from the predetermined value by more than a predetermined value, the ratio A/B of the fresh-air flow to the input-air flow will be compared to the predetermined ratio. This chain of steps is repeated in the order presented, or in part, until the input-air flow B, the ratio A/B of the fresh-air flow to the input-air flow and at the same time the difference A-D between the fresh-air flow and the waste-air flow, or their ratio A/D, reach their predeter¬ mined values. Thus the outlet-air mechanism 10 and thereby the return-air flow E may be for the control steps a start¬ ing point which has first been set according to other cri¬ teria, or alternatively the outlet-air mechanism can be used as a control means for achieving the desired fresh-air to input-air ratio A/B. In the event that the apparatus is simpler in construction in such a way that it does not include the possibility of using a return-air flow E, in which case the exhaust-air flow C is at all times equal to the waste-air flow D, the control method will be simply to control the flows directly in the input-air duct 1 and the waste-air duct 22 in order to control the input-air flow B or/and the waste-air flow D, while keeping, however, the said difference A-D between the fresh-air flow and the waste-air flow, or their ratio A/D, as the criterion. In principle the method described above can be applied by using components of any type, but preferably both the in¬ take-air mechanism 3 and the outlet-air mechanism 10 are fixed to the heat recovery exchanger 4. Preferably in these mechanisms the closing and control means, such as levers or similar means, are coupled to each other in such a way that, in the outlet-air mechanism 10, a gradual closing of the waste-air flow D will cause a simultaneous gradual opening of the return-air flow E at a corresponding rate, and vice versa, and, in the intake-air mechanism 3, the closing of the fresh-air flow A' to the heat recovery ex¬ changer 4 will cause a simultaneous opening of the fresh- air bypass flow F, and vice versa. It is also advantageous, in order to obtain a reliable measurement, that the input- air and waste-air flows A, D are measured in the pressure apertures of the fans 5, 18, or in the continuations of the apertures, as described in our Finnish patent application 874 009. Furthermore, it is preferable to measure the fresh-air flow at the point of connection of the air-condi¬ tioning system to the fresh-air duct or inside the air- conditioning system at a point before the filter or after the filter in the direction of the air flow, and that the pressures of the input air and exhaust air B, C are mea¬ sured inside the air-conditioning system or at the points of connection of the air-conditioning system to the input- air and exhaust-air ducts 1, 9, inside the system.

Claims: Claims 1. A method for controlling the fresh-air, input-air, exhaust-air, waste-air and return-air flows, as well as the air pressure in the input-air duct and the air pressure in the exhaust-air duct, in an air-conditioning system in which the closing and control mechanisms for the fresh air and the fresh-air bypass in respect to the heat recovery exchanger are coupled to each other as an intake-air mecha¬ nism (3) and, respectively, the closing and control mecha¬ nisms for the exhaust air and the return air are coupled to each other as an outlet-air mechanism (10), characterized in that the control of the fresh-air, input-air, exhaust- air, waste-air and return-air flows (A, B, C, D, E) and of the pressure in the input-air duct and of the pressure in the exhaust-air duct are interconnected in such a way that a deviation from the predetermined value in one of these will cause a change of the predetermined values in the others so that the difference (A-D) between the fresh-air flow and the waste-air flow, or their ratio (A/D), will change in a predetermined way. 2. A method according to Claim 1, characterized in that the fresh-air flow (A) is adjusted by regulating the flow in the input-air duct (1) on the basis of a change in the return-air flow (E) so that the difference (A-D) between the fresh-air flow and the waste-air flow, or their ratio (A/D), will remain constant. 3. A method according to Claim 1, characterized in that the input-air flow (B), the waste-air flow (D) and/or the outlet-air mechanism (10) is controlled so that first the ratio (A/B) of the fresh-air flow to the input-air flow and next the difference (A-D) between the fresh-air flow and the waste-air flow, or their ratio (A/D), will be at the predetermined values. 4. A method according to Claim 3, characterized, in that, after a change of the position of the outlet-air mechanism (10), the input-air flow (B) or the pressure in the input- air duct (1) is adjusted to the predetermined value, and that thereafter the waste-air flow is controlled so that the difference (A-D) between the measured values of the fresh-air flow and the waste-air flow, or their ratio (A/- D) , will become the predetermined constant value, and that thereafter, if the input-air flow (B) or the pressure in the input-air duct (1) does not deviate from the predeter¬ mined value by more than a set deviation, the ratio (A/B) of the fresh-air flow to the input-air flow will be com¬ pared to the-predetermined ratio, and that this said chain cf steps is repeated in the order presented, or in part, until the ratio A/B and at the same time the difference (A- D) , or the ratio (A/D), reach the predetermined values. 5. A method according to Claim 1, characterized in that, when the exhaust-air flow (C) is equal to the waste-air flow (D) , the input-air flow (B) is controlled on the basis of the change in the pressure in the input-air duct (1) so that the difference (A-D) between the fresh-air flow and the waste-air flow, or their ratio (A/D) , will remain con¬ stant. 6. A method according to Claim 1, characterized in that, when the exhaust-air flow (C) is equal to the waste-air flow (D) , the exhaust-air flow (C) is corrected by adjust¬ ing the flow in the waste-air duct (22) on the basis of the pressure change in the exhaust-air duct (9) in such a way that the difference (A-D) between the fresh-air flow and the waste-air flow, or their ratio (A/D), will remain con¬ stant. 7. A method according to Claim 1, characterized in that, when the exhaust-air flow (C) is equal to .the waste-air flow (D), either the input-air flow (B) is adjusted on the basis of the change in the exhaust-air flow (C) so that the difference (A-D) between the fresh-air flow and the waste- air flow, or their ratio (A/D), will remain constant, or the exhaust-air flow (C) is corrected on the basis of the change in the input-air flow (B) by adjusting the flow in the waste-air duct (22) so that the difference (A-D) be¬ tween the fresh-air flow and the waste-air flow, or their ratio (A/D) , will remain constant, or these two said ad¬ justments are carried out in alternation. 8. A method according to any of the above claims, charac¬ terized in that, when the waste-air flow (D) decreases to a value lower than the predetermined value and simultaneously the outside temperature drops lower than the predetermined value, the intake-air mechanism (3) adjusts to a position in which the fresh-air flow (A) is in its entirety fresh- air bypass flow (F), and that thereafter, when the waste- air flow (D) has risen to the predetermined value and/or a predetermined time has elapsed from the said adjusting of the intake-air mechanism (3) to its bypass position (A=F), the intake-air mechanism will switch back to its initial position, in which no bypass (F) of fresh air occurs. 9. A method according to any of the above claims, charac¬ terized in that the difference (A-D) between the fresh-air flow and the waste-air flow, and their ratio (A/D), are used during the control alternately, on a time basis, as the control basis for the adjustment step. 10. An apparatus for carrying out the method according to Claim 1, comprising at least input-air and waste-air flow meters (6, 20), input-air and exhaust-air pressure meters (12, 19), an input-air fan (5) with its air-flow control means (13), a waste-air and exhaust-air fan (18) with its air-flow control means (14), a fresh-air flow meter (15), a heat recovery exchanger (4), mechanisms for the closing and control of the exhaust air and the return air, coupled to form an outlet-air mechanism (10), and closing and control mechanisms for fresh air and fresh-air bypass, coupled to form an intake-air mechanism (3) , characterized in that the fresh-air flow and input-air flow meters (15, 6) and the input-air duct air pressure meter (12) are connected to the input-air flow control (13), and the waste-air flow meter (20) and the exhaust-air duct air pressure meter (19) are connected to the waste-air flow control (14), and that these controls (13, 14) work together and are fitted to act on the fans (5, 18) and mechanisms (3, 10) so that a change in one of the quantities measured will cause an adjustment of the input-air flow (B), the waste-air flow (D) , the outlet-air mechanism (10) and/or the intake-air mechanism (3) so that the ratio (A/B) of the fresh-air flow to the input-air flow and/or the difference (A-D) between the fresh-air flow and the waste-air flow, or their ratio (A/D) , will be at the predetermined values or/and that the fresh-air bypass flow (F) will open or close. 11. An apparatus according to Claim 10, characterized in that the input-air and waste-air flows (B, D) are measured in the pressure apertures (5, 18) of the fans, or in the continuations of the apertures. 12. An apparatus according to Claim 10, characterized in that the fresh-air flow (A) is measured at the point of connection of the air-conditioning system to the fresh-air duct or inside the air-conditioning system at a point before the filter or after the filter in the flow direc¬ tion. 13. An apparatus according to Claim 10, characterized in that the pressures of the input air and the exhaust air (B, C) are measured inside the air-conditioning system, or in- side the air-conditioning system at its connections to the input-air and exhaust-air ducts (1, 9). 14. An apparatus according to any of Claims 10-13, charac¬ terized in that the intake-air mechanism (3) and the out¬ let-air mechanism (10) are fixed to the heat recovery ex¬ changer (4), and that in these the closing and control mechanisms are coupled to each other so that, in the outlet-air mechanism (10), the closing of the waste-air flow (D) will cause a simultaneous opening of the return- air flow (E), and vice versa, and so that, in the intake- air mechanism (3), the closing of the fresh-air flow (A') to the exchanger (4) will cause an opening of the fresh-air bypass flow (F), and vice versa.

Inventors: LAINE JUHANI, NYMAN MIKKO, PAANANEN TAPIO, LAINE, JUHANI, NYMAN, MIKKO, PAANANEN, TAPIO
Applicants: ILMATERAE OY
Application year: 1988
Main classification: F24F11
IPC codes: F24F11, F24F12, F24F13