EP0694150A1 - An air-conditioning apparatus and a method of controlling its operation - Google Patents
An air-conditioning apparatus and a method of controlling its operationInfo
- Publication number
- EP0694150A1 EP0694150A1 EP94912565A EP94912565A EP0694150A1 EP 0694150 A1 EP0694150 A1 EP 0694150A1 EP 94912565 A EP94912565 A EP 94912565A EP 94912565 A EP94912565 A EP 94912565A EP 0694150 A1 EP0694150 A1 EP 0694150A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- air
- return
- room
- duct
- adjusting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
- F24F3/044—Systems in which all treatment is given in the central station, i.e. all-air systems
Definitions
- This invention relates to a method of con- trolling the operation of an air-conditioning apparatus comprising
- - adjusting means for adjusting the amounts of outdoor air, indoor air removed from the room, and indoor air to be returned into the room, said means being adjustable between a closed position preventing the passage of air and an open position allowing the passage of air;
- the adjusting means being adjustable for con- trolling the mixing ratios between said amounts of air according to desired conditions to be achieved in the room.
- the need for air-conditioning in buildings depends on the number of people staying in the build- ing at a specific time, the amount of impurities entering the air, the heat load, etc.
- the air- conditioning system especially the flow of air, has to be designed according to the maximum load. As the heat load is very often the factor determining the design values, the air-conditioning system often has to be operated at an unnecessarily high power, especially in winter, if the power cannot be adjusted. This would require a very high amount of energy, especially thermal energy, as whatever the way cold outdoor air is introduced into the building, the air has to be heated.
- An object of the present invention is to provide a method which avoids the above drawbacks and allows the operation of an air-conditioning apparatus to be controlled. This object is achieved by a method according to the invention, which is characterized in that the outdoor air and the return air are passed into the room alternately, and that the durations of the open periods of the adjusting means are adjusted to correspond with a desired mixing ratio between the amounts of outdoor and return air in the room.
- An essential feature of the invention is that the supply device and the return device are used alternately and periodically for periods such that a desired mixing ratio between outdoor air and return air is achieved in the room.
- Another object of the invention is to provide a controllable air-conditioning apparatus in which desired air flows and mixing ratios are achieved with a high accuracy; the minimum flow of outdoor air is achieved under all circumstances; the pressure ratios of the building remain undisturbed at all operating points in all rooms to be air-conditioned; the mixing process will not cause problems in the mixing section itself nor does it disturb the operation of subsequent sections; and the apparatus required for adjustment is substantially simpler than previously.
- An essential feature of the invention is that the operation of the mixing section (return device) is designed so as to be controllable according to the properties of the system only at two operating points of the mixing section, or at a limited number of operating points, and the mixing section is operated by ON/OFF adjustment only at these operating points.
- a desired mixing ratio is achieved by varying the duration of operation at each operating point.
- the system operates through ON/OFF adjustment so that the outdoor air device and the return air device are used alternately, i.e., only outdoor air or only return air is introduced into the room.
- a desired mixing ratio i.e. the ratio between the outdoor air flow and the return air flow, is achieved by varying the duration of the different operating periods. Accordingly, if the total air flow to be passed into the room should contain one half of return air, the dampers of the return device are open for one half of the total operating time and closed for the other half. If the minimum requirement of outdoor air flow is e.g. 30% of the total air flow, the outdoor air damper is open for 30% of the total time.
- the adjustment is based on the degree of use of the building, the purity or tem ⁇ perature of air, the outdoor temperature, etc.
- the adjusting motors are simple ON/OFF motors, which are considerably cheaper and more reli ⁇ able in operation than relatively adjusting motors in use today.
- the adjustment logic is somewhat simpler.
- Figures 1 and 2 are schematic views of one pre ⁇ ferred embodiment of an air-conditioning apparatus according to the invention in outdoor air flow oper- ation and in return air flow operation, respectively;
- FIGS 3 and 4 show alternative embodiments of the air-conditioning apparatus.
- the air-conditioning apparatus shown in Figure 1 of the drawings comprises a supply device 1, an ex ⁇ haust device 2, and a return device 3.
- the supply device 1 comprises a supply air duct
- a damper 6, a filter 7, a heat recovery means 8, a damper 9, heat- ing and cooling elements 10, 11, and a blower 12 are installed inside the duct 5.
- the blower creates an outdoor air flow A in the duct.
- the exhaust device 2 comprises an exhaust air duct 13 extending from the room to outdoor air.
- a filter 14, a blower 15, dampers 16, a heat recovery means 17 and a damper 18 are installed inside the duct.
- the blower creates an exhaust air flow B in the duct.
- the return device 3 comprises a return air duct 19, within which a damper 20 is installed.
- a return air flow C consisting of exhaust air passes through the duct.
- the dampers 9, 16 and 20 are connected to oper ⁇ ating means 21 which adjust the dampers into different operating positions, in this specific example between a closed position and an open position.
- the operating means are controlled by adjustable time switches 22, by means of which the durations of the open periods can be adjusted.
- the operation of the return device 3 is designed to be controlled according to the properties of the system only at two operating points of the return device.
- the air-conditioning apparatus shown herein operates through ON/OFF adjustment so that only out- door air A or only return air C is passed alternately into the room during the different operating periods. In the former case, the dampers 6 and 9 of the supply device and the dampers 16 and 18 of the exhaust device are fully open, while the damper 20 of the return device is fully closed.
- a desired mixing ratio i.e. the ratio between the amount of outdoor air and the amount of return air in the room is achieved by adjusting the duration of the different operating periods, i.e. the time during which the dampers are open. If the desired proportion of outdoor air A in the total air flow introduced into the room is 50% and the proportion of return air C is 50%, the dampers are open for one half of the total time and closed for the other half. On the other hand, if the desired minimum amount of outdoor air in the total amount of air is 30%, the dampers 6 and 9 of the supply duct should be kept open for 30% of the total time while the damper 20 of the return duct is closed.
- the operating means 21 are preferably ON-OFF servomotors.
- the total air flow tends to increase during return air operation, as the resistance of the damper 20 is considerably smaller than the combined resistance of the elements 16, 17, 18 and 6, 7, 8, 9. This may result in overloading of the blower motors, noise and draught problems in the rooms to be air-conditioned, etc.
- These problems can be avoided and the total air flow can be kept constant by making the damper 20 so small that its resistance is sufficient in the open position, or by restricting its open position so that a desired resistance is achieved.
- the part may be a perforated plate or a nozzle plate, the free area of the openings of which is selectable or adjustable in a desired way; or it may be a series of plates having mutual spacings adjustable by varying the position of the plates with respect to each other, or any other similar device.
- the operation of the mixing section can be controlled and the desired performance values can be predesigned in accordance with the requirements of each particular apparatus, in addition to which the apparatus can be prefabricated also in this respect.
- the required additional parts are considerably cheaper than e.g. the savings that could be obtained in the price of electric motors.
- the operation of the system can be ensured even in such cases by providing the servomotors of the dampers with a limiter, beginning from a certain out ⁇ door temperature or mixing ratio.
- the duration of the open period has to be increased correspondingly by dividing the time corresponding to the 100% air flow by 0.7.
- the air flow ratios are maintained unchanged and can be adjusted even in this case, whereas there are three flow resistances to be adjusted in place of one resistance (the dampers 6, 9, 16, 18 only for one operating point, and the damper 20 for two operating points corresponding to 100% and 30% air flows).
- the adjustment is more complicated, although it is still easy as compared with the systems presently in use.
- the system is self-balancing to some extent: for instance, on transition from outdoor air operation to return air operation, the liquid circulation system operates in a manner resembling heat recovery for some time due to the large liquid volumes and heat sur- faces. In other words, it first cools the air in a heat exchanger 17 ' on the exhaust air side and then again heats it up in a heating element 8 ' on the supply air side. As there is no risk of freezing, the adjustment can be made to act in advance so that a valve 24 closes the heat supply at the same time as or slightly before the return air damper 20 starts to open. As a consequence, the temperature of the supply air first drops slightly on transition to return air operation, then rises slightly, and finally returns to room temperature.
- the temperature variation of the supply air remains small, especially as compared with conven- tional heat exchanger systems, in which the temper ⁇ ature difference is between 40 and 50 C C.
- One embodiment of the system is to realize the return air operation merely by the use of the supply air blower, as shown in Figure 4.
- the return air is taken directly from the exhaust duct 13 or from the return duct 19 specially provided for the purpose directly to the suction side of the supply air blower 12.
- the exhaust air blower 15 is stopped entire ⁇ ly during the return air period. In this way the electric power consumed by the exhaust air blower will be saved, which may be significant.
- the proportion of return air of the total air flow can be adjusted continuously between 0 and 100% by varying the duration of the operating periods.
- the use of return air is also possible in apparatuses where the exhaust and supply air blowers are remote from each other.
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Air Conditioning Control Device (AREA)
- Devices That Are Associated With Refrigeration Equipment (AREA)
- Road Signs Or Road Markings (AREA)
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FI931848 | 1993-04-23 | ||
FI931848A FI100065B (en) | 1993-04-23 | 1993-04-23 | Air conditioning equipment and method for controlling its operation |
PCT/FI1994/000154 WO1994025804A1 (en) | 1993-04-23 | 1994-04-22 | An air-conditioning apparatus and a method of controlling its operation |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0694150A1 true EP0694150A1 (en) | 1996-01-31 |
EP0694150B1 EP0694150B1 (en) | 1999-03-24 |
Family
ID=8537795
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP94912565A Expired - Lifetime EP0694150B1 (en) | 1993-04-23 | 1994-04-22 | An air-conditioning apparatus and a method of controlling its operation |
Country Status (7)
Country | Link |
---|---|
EP (1) | EP0694150B1 (en) |
AT (1) | ATE178135T1 (en) |
AU (1) | AU6506394A (en) |
DE (1) | DE69417411T2 (en) |
DK (1) | DK0694150T3 (en) |
FI (1) | FI100065B (en) |
WO (1) | WO1994025804A1 (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2135011B1 (en) * | 2007-01-11 | 2016-11-16 | Swegon AB | Air conditioning equipment for return air |
JP4703692B2 (en) | 2008-07-11 | 2011-06-15 | 株式会社東芝 | Air conditioning control system, air supply switching controller used therefor, and air conditioning control method |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2224407A (en) * | 1938-02-15 | 1940-12-10 | Passur Norman | Control means for air circulating systems |
US3635282A (en) * | 1969-06-05 | 1972-01-18 | New Cosmos Electric Co | Air-conditioning device of automatic ventilation type |
US4199101A (en) * | 1979-01-26 | 1980-04-22 | Johnson Controls, Inc. | Multiple load integrated fluid control units |
FI78979C (en) * | 1988-02-18 | 1989-10-10 | Halton Oy | Method for controlling air conditioning and air conditioning device for use in the process. |
-
1993
- 1993-04-23 FI FI931848A patent/FI100065B/en active
-
1994
- 1994-04-22 AT AT94912565T patent/ATE178135T1/en not_active IP Right Cessation
- 1994-04-22 WO PCT/FI1994/000154 patent/WO1994025804A1/en active IP Right Grant
- 1994-04-22 EP EP94912565A patent/EP0694150B1/en not_active Expired - Lifetime
- 1994-04-22 DE DE69417411T patent/DE69417411T2/en not_active Expired - Fee Related
- 1994-04-22 DK DK94912565T patent/DK0694150T3/en active
- 1994-04-22 AU AU65063/94A patent/AU6506394A/en not_active Abandoned
Non-Patent Citations (1)
Title |
---|
See references of WO9425804A1 * |
Also Published As
Publication number | Publication date |
---|---|
DE69417411T2 (en) | 1999-08-19 |
DK0694150T3 (en) | 1999-10-11 |
DE69417411D1 (en) | 1999-04-29 |
FI931848A (en) | 1994-10-24 |
AU6506394A (en) | 1994-11-21 |
ATE178135T1 (en) | 1999-04-15 |
EP0694150B1 (en) | 1999-03-24 |
FI931848A0 (en) | 1993-04-23 |
FI100065B (en) | 1997-09-15 |
WO1994025804A1 (en) | 1994-11-10 |
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