METHOD FOR THE CONTROL OF AIR-CONDITIONING AS WELL AS EQUIPMENT FOR CARRYING OUT THE METHOD

Abstract: Method for the control of a ventilation system using recirculation air or fresh air or a mixture of same, in particular for the control of the ventilation of vegetable and potato warehouses. In the method for controlling the flows of air, pressure-actuated gates (9, 10) or corresponding members are used, whereas, in accordance with the invention, as fresh-air gates (9) are used gates opened by the effect of negative pressure, as well as for the circulation air, gates (10) opened at least by the effect of negative pressure. The opening of the circulation-air and fresh-air gates relative to each other by the effect of negative pressure is controlled by means of a temperature-actuated device (12, 13), which limits the position of opening of the gates but permits free closing at least of the fresh-air gate.

Description: Method for the control of air-conditioning as well as equipment for carrying out the method The present invention is concerned with a method for the control of air-conditioning based on air-conditioning gates or equivalent members and a system of air-conditioning gates used for putting the method into effect. The primary objects of use of the air-conditioning in accordance with the invention are potato and vegetable warehouses in which adjustable gates are used for controlling the outdoor-air venti¬ lation of the warehouses. The objective of the outdoor-air ventilation is to cool the warehouse. The temperature of the air used for the cooling must, however, not be excessively low (at the maximum 4 C lower than the temperature of the vegetables) , and therefore the outdoor air cannot be used for the cooling as such, during the cold season. By means of the technology known at present, the above problem has been solved in principle in two ways. 1. Positively driven gates By means of positively driven gates, indoor air and outdoor air are mixed together at an appro¬ priate ratio, and the cooling air in this way obtained is blown to among the vegetables. The temperature of the air used for cooling can always be chosen suitable in respect of the vegetables irrespective of the outdoor temperature. By means of this method, the problem mentioned initially can be controlled com¬ pletely, and outdoor air can be used for cooling always when it is colder than the vegetables. Figure 1 illustrates the principle of posi- tively driven gates. By means of the gate 1, indoor and outdoor air can be mixed together and the inlet opening for outdoor air be closed when cooling is not required. The evacuation of indoor air corresponding to the outdoor air sucked into the warehouse through the gate 1 can be arranged through an outlet air gate opened synchronously with gate 1, as is shown in Fig. 1. In the example of Fig. 1, the position of the gates 1 is varied by means of a shaft 3 operating the racks 2 and by means of a motor 4 driving the shaft. Starting of the blower 5 does not affect the position of the gate 1 in any situation. When cooling is performed by means of outdoor air, the blower 5 blows air in the direction of the arrow 7, and when indoor air is being circulated, the direction of the air is that shown by the arrow 8 , and the gate 1 closes the inlet opening of outdoor air. A drawback of the method is its high cost. Each gate requires a mechanism to control its position, and even if several gates had, e.g., a common drive motor, a drive motor of its own is required for each warehouse compartment that is controlled separately. Each drive motor requires its own contactors, fuses, switches, etc. in the group distribution board. More¬ over, separate cables are required for each motor. 2. Negative-pressure gates In principle, negative-pressure gates have only two different positions: either open or closed. The gates have no separate opening mechanism, but they are opened by the effect of the negative pressure generated by the blower. In the method, it is neces- sary to use two gates in order that it should be possible to control both the outdoor-air cooling and the so-called circulation correctly. Figure 2 illustrates the principle of the negative-pressure gates. When the vegetables are supposed to be cooled, the blower 5 is started so that the air flows in the direction of the arrow 7. Thereat the gate 9 is opened, and the gate 10 is OMPI so closed by the effect of the negative pressure produced by the blower 5 and by the effect of the force of gra¬ vity. The air blown by the blower 5 to among the vegetables 11 consists exclusively of outdoor air. When the indoor air in the warehouse is sup¬ posed to be circulated, the blower 5 is started so that the air flows in the direction of the arrow 8, whereat the gate 10 is opened, and the gate 9 is closed. The access of outdoor air into the warehouse is pre- vented during the circulation stage. If the blower 5 is stopped (the blower is at standstill most of the time) , both of the gates 9 and 10 are closed by the effect of their own weight more or less tightly. The gates opened by the negative-pressure method are of low cost, but their operation is defi¬ cient. The most important drawback of the negative- pressure gates is that by their means it is not pos¬ sible to mix indoor air and outdoor air with each other at the desired ratio, so that they cannot be used for cooling when the outdoor air is excessively cold. During long frost periods, the temperature in the warehouse can become higher, and that is detrimental in view of the storage, e.g., in the form of increased weight losses. The negative-pressure gates are not closed reliably, as a result of which ice is accumula¬ ted in the slots between the gates and the frames in frost periods, which ice may further cause, e.g., freezing up. The negative-pressure gates are also constantly subject to the effects of wind. By means of the gate control method in accordance with the present invention, it is possible to avoid the worst drawbacks of the above methods and to combine their advantages. By means of one gate positioning motor, it is possible to control the mixing ratio of several gates depending on the difference between the temperatures of the indoor and outdood air, however, so that the opening of the gates is not positively controlled. Thereat, the gates controlled by means of this method, may be located in separate warehouse compartments, and the temperatures in the said separate warehouse compartments can be adjusted individually. When no warehouse compartment belonging to the control circuit of the same positioning motor is being cooled, the gates are closed tightly by means of the positioning motor of the gates. The circulation of the indoor air in the warehouse can be performed freely at any time whatsoever irrespective of the posi¬ tion of the positioning motor of the gates. The method for the control of air-condition¬ ing in accordance with the present invention and the equipment for carrying out the said method are mainly characterized in what is stated in the patent claims. The method of controlling the air-condition¬ ing gates in accordance with the present invention and the operation of the gates of the method will be described in detail in the following by means of the following figures: Figure 3 shows the operation of a gate in accordance with the invention in different situations of operation. The component figure 3 f is a top projection of the construction of a warehouse of several compartments, in accordance with the present invention. The component figures 3 a, b, c, and d are sectional views slong line A-A and illustrate the operation of the gates in different situations of operation. Figure 4 shows a possible alternative of location of the gate system in accordance with the present invention in a vegetable warehouse. Figure 5 shows an alternative constructional embodiment of the gates operating in accordance with the gate control method of the present invention. O PI . mp ° In the following, the method in accordance with the invention as well as the operation of the gates controlled by means of the method will be described with reference to Fig. 3. The gates in accordance with the invention consist of a fresh-air gate 9, which can be opened only inwards, of a circulation-air gate 10, which can be opened to both sides of its vertical balance position, of a position-control rod 12 of the gates 9 and 10, and of the drive shaft 13 of the rod 12. The system additionally includes a blower 5 and an automatic control system, which controls the blowers, the gate motor, etc., but which is not shown in the drawing . The examination of the method of the inven¬ tion and of the gate system controlled by means of the method is started from a situation in which there is a correct temperature in the warehouse and it does not have to be cooled. The blower 5 is at standstill, and both of the gates 9 and 10 are closed (Fig. 3 a) . The fresh-air gate 9 is pressed against its frame by means of the rod 12 used for controlling the mixing ratio, which rod ensures that the gate remains closed, e.g., in spite of a pressure caused by wind. The control rods 12 of all of the gates connected to the same con¬ trol circuit are attached to the shaft 13 operating them in the same position relative each other (Fig. 3e) , so that all the gates are in the closed position. When a requirement of cooling occurs in one warehouse compartment belonging to the system and when it is sufficiently cold outdoors, the automatic control system starts the blower of the warehouse compartment concerned in the direction of the arrow 7, whereat the negative pressure produced by the blower opens the circulation-air gate 10, but the fresh-air gate 9 srill remains closed, owing to the control rod 12. A guide value of, e.g. 2 C has been given to the automatic control system for the difference in temperature between the vegetables and the air used for their cooling. After the starting of the blower, the automatic system starts turning the shaft 13 in the direction of the arrow 14, whereat the control rod 12 obtains, e.g., a position shown in Fig. 3b, and the fresh-air gate 9 can be opened by the effect of nega¬ tive pressure. The automatic system goes on turning the control rod 12 in the direction of the arrow 14 until the temperature of the air 6 flowing in the duct is colder than the vegetables by the required 2 degrees. In a case in which the temperature of the outdoor air is exactly two degrees colder than the vegetables, the control rod is turned to the position shown in Fig. 3d, whereat the fresh-air gate is fully open, the circulation-air gate 10 is fully closed, and the air 6 flowing in the duct consists exclusively of outdoor air. It is to be noticed that the opening of gates described above takes place in the warehouse compartments only in which the blower was started; in the other compartments the gates are fully closed. However, if the blower of some other warehouse com- partment is started for the purpose of cooling, its gates obtain the same position. After the warehouse has been cooled to a sufficient extent, the controller turns the control rod 12 to the position shown in Fig. 3a, whereat all the fresh-air gates are closed by mechanical force. In the warehouses, besides cooling, there is also other need for circulation of air. When the ware¬ house has not had to bee cooled for a long time, the indoor air in the warehouse tends to be formed as layers so that warm and moist air is gathered in the top portion of the warehouse, and cold and drier air in the bottom portion. These layers must be mixed at G_ ?I regular intervals, e.g., after every 5 hours. The mixing must be performed so that cold and dry air from the bottom portion of the warehouse is blown into the top portion of the warehouse, because in the contrary case condensed water would be produced in the bottom portion of the warehouse. In the method in accordance with the present patent application, the mixing is performed simply by starting the blower 5 in the direction indicated by the arrow 8, whereat the fresh-air gate 9 is closed and the circulation-air gate 10 is opened in the way shown by Fig. 3e. It is to be noticed that the position of the control rod 12 has no significance for the mixing blowing mentioned above, i.e., even if cooling is performed in some warehouse compartment belonging to the same control circuit, the mixing in accordance with Fig. 3e can be performed in the other compartments. Fig. 5 shows an alternative embodiment ope¬ rating by means of the gate control method of the pre- sent invention, wherein the control rod 12 of the embodiment described above has been substituted for by a gate 15 moving in the same way. In this alternative embodiment, the mixing ratio is determined by mea-.s of the position of the gate 15 in the warehouse com- partments in which the blower 5 revolves in the direc¬ tion of the arrow 7. If the gate 15 is opened to the fully open position 16, it closes the access of the indoor air 17 into the duct completely, whereat the cooling takes place exclusively by means of outdoor air. It is a drawback of this constructional alternative that, if the gate 16 is open for cooling taking place in some warehouse compartment, mixing circulation of indoor air cannot be performed in the other compartments at the same time. Above, some embodiments of a gate system operating by means of the control method for air-con- ditioninα αates in accordance with the present invention have been described, but for a person skilled in the art, it is self-evident that the gate control prin¬ ciple in accordance with the invention can also be accomplished by means of different constructions of the gate system, and therefore the invention should not be confined to the embodiments described above. C PI

Claims: WHAT IS CLAIMED IS: 1. Method for the control of an air-con¬ ditioning making use of recirculation air, fresh air, or a mixture thereof in vegetable or potato warehouses, in which method circulation-air and fresh-air openings are adjusted by means of pressure-actuated gates or gratings, c h a r a c t e r i z e d in that, for fresh air, gates opened by means of negative pressure are used, that for circulation air, gates opened at least by negative pressure are used, and that the opening of the circulation-air and fresh-air gates relative each other by the effect of negative pressure is controlled by means of a temperature-actuated con- trol member, which defines the position of opening of the gates but permits free closing at least of the fresh-air gate. 2. Method as claimed in claim 1 , c h a r ¬ a c t e r i z e d in that for circulation air, gates opened both by negative pressure and by positive pressure are used and that the control member permits free closing both of the fresh-air gate and of the circulation-air gate. 3. Equipment for carrying out the method as claimed in claims 1 and 2, which said equipment consists of a blower (5) of variable direction of rotation, placed in the ventilation duct, of fresh-air and circulation-air gates (9, 10) leading into the duct and closing by the effect of pressure and prefer- ably by the effect of the force of gravity, of temperature-actuated members (12, 13) controlling the operation of the gates, c h a r a c t e r i z e d in that the fresh-air gate (9) is opened by the effect of negative pressure, that the circulating-air gate (10) is opened by the effect of both negative pressure and positive pressure, and that temperature-actuated control members (12, 13) are provided so as to limit the opening of the gates (9, 10) relative each other by the effect of negative pressure, but to permit free closing of the gates. 4. Equipment as claimed in claim 3, c h a r a c t e r i z e d in that temperature-actuated control members (12, 13) are provided so as to con¬ fine the fresh-air gate to the closed position after the effect of negative pressure has ceased in the ventilation duct.

Inventors: RUOKOLAINEN ANTTI, RUOKOLAINEN, ANTTI
Applicants: ITUMIC OY
Application year: 1984
Main classification: F24F13
IPC codes: A23B7, F24F11