METHOD FOR CONTROLLING THE TEMPERATURE AND HUMIDITY OF THE AIR CONTAINED IN AN ENCLOSED REFRIGERATED SPACE

Abstract

A method for controlling the temperature and humidity level of the air contained in an enclosed refrigerated space includes the step of measuring the temperature of air in the space. The space includes a cooler having a plurality of cold batteries; at least one coolant temperature sensor at the input and at least one coolant temperature sensor at the output of the cooler; at least one fan with an adjustable, reversible direction of ventilation for producing a variable flow of air through the cooler; at least one temperature sensor upstream of the fan; at least one temperature sensor downstream of the cooler; at least one humidity level sensor upstream of the fan; and at least one humidity level sensor downstream of the cooler. The control is affected by reference values given initially for the temperature and humidity level in the enclosed space.

Claims

1. A method for controlling the temperature and humidity comprising the steps of: Step A: measuring a temperature of air in an enclosed space, the space comprising: a cooler comprising a plurality of cold batteries provided with means for selecting the number of cold batteries in service in order to vary the cooling capacity, said cooler being supplied with a coolant of variable speed and temperature; at least one coolant temperature sensor at the input and at least one coolant temperature sensor at the output of the cooler; at least one fan with an adjustable, reversible direction of ventilation for producing a variable flow of air through the cooler; at least one temperature sensor upstream of the fan; at least one temperature sensor downstream of the cooler; at least one humidity level sensor upstream of the fan; and at least one humidity level sensor downstream of the cooler; said air in said enclosed space having reference values given initially for an initial temperature and initial humidity; Step B. If the measured temperature of the air in the enclosed space is higher than the reference temperature; 1. if said temperature is higher than a predetermined threshold temperature: cooling by increasing the flow of air, cooling and increasing the speed of the coolant, establishing a maximal cooling capacity by selecting all the cold batteries; 2. if said temperature is less than said predetermined threshold temperature: measuring the humidity level, comparing it to the reference humidity value and modifying the humidity level, if it is not equal to the reference value, by varying the flow of air, the temperature and the speed of the coolant, and the cooling capacity; and Step C. If the measured temperature of the air in the enclosed space is less than the reference temperature, measuring the humidity level, comparing it to the reference humidity level and modifying the humidity level if it is not equal to the reference value, by varying the flow of air and the direction of ventilation, the temperature and speed of the coolant and the cooling capacity of the flow of air and/or reversing the direction of ventilation.

2. The method for controlling temperature and humidity, according to claim 1 wherein Step B. if the air temperature is higher than the reference temperature, if 2. said temperature is less than said predetermined threshold temperature, and if the humidity level is less than the reference humidity level, comprises setting in motion a processing cycle for the following parameters: increasing the flow of air in the enclosed space; establishing maximal cooling capacity by selecting all the cold batteries; increasing the temperature of the coolant; reducing the circulation speed of the coolant.

3. The method for controlling temperature and humidity, according to claim 1 wherein Step B. if the air temperature is higher than the reference temperature, if 2. said temperature is less than said predetermined threshold temperature, and if the humidity level is greater than the reference humidity level, comprises setting in motion a processing cycle for the following parameters is: reducing the flow of air in the enclosed space; bringing a third of the cold batteries into service; reducing the temperature of the coolant; increasing the circulation speed of the coolant.

4. The method for controlling temperature and humidity, according to claim 1 wherein Step B. if the temperature of the air is higher than the reference temperature, if 2. said temperature is less than said predetermined threshold temperature, and if the humidity level is equal to the humidity reference value, comprises setting in motion a processing cycle for the following parameters is stabilizing the flow of air in the enclosed space; stabilizing the number of cold batteries in service; stabilizing the temperature of the coolant; stabilizing the circulation speed of the coolant.

5. The method for controlling temperature and humidity, according to claim 1, wherein the threshold temperature is at least equal to the reference temperature plus 3° C.

6. The method for controlling temperature and humidity, according to claim 1, wherein Step C. if the temperature of the air is less than or equal to the reference temperature and the humidity level is less than the humidity reference value, comprises setting in motion a processing cycle for the following parameters: increasing the flow of air in the enclosed space; establishing a maximal cooling capacity by selecting all the cold batteries; measuring the temperature of the coolant: if the temperature of the coolant is less than the temperature of the air in the enclosed space, increasing the circulation speed of the coolant; if the temperature of the coolant is higher than or equal to the temperature of the air in the enclosed space, stopping the circulation of the coolant.

7. The method for controlling temperature and humidity, according to claim 1, wherein Step C. if the temperature of the air is less than or equal to the reference temperature and if the humidity level is equal to the reference humidity level, comprises setting in motion a processing cycle for the following parameters: reducing the flow of air in the enclosed space to a predetermined value and/or reversing the direction of ventilation; establishing maximal cooling capacity by selecting all the cold batteries; maintaining the temperature of the coolant: stopping the circulation of the coolant.

8. The method for controlling temperature and humidity, according to claim 1, wherein Step C. if the temperature of the air is less than or equal to the reference temperature and the humidity level is greater than or equal to the reference humidity value, comprises setting in motion a processing cycle for the following parameters: reducing the flow of air in the enclosed space to a predetermined value and/or reversing the direction of ventilation; establishing maximal cooling capacity by selecting all the cold batteries; reducing the temperature of the coolant to a predetermined value; increasing the circulation speed of the coolant to a predetermined higher value.

9. The method for controlling temperature and humidity, according to claim 1, wherein the temperatures of the motors of the fans are measured and the power percentage of each motor is subject to the highest temperature measured.

10. The method for controlling temperature and humidity, according to claim 1, further comprising the steps of: measuring and recording data, including durations, for the parameter processing cycles over predetermined time periods; comparing the data for the parameter processing cycles set in motion with the recorded data and durations; and triggering corrective actions and alarms if the differences exceed the predetermined values.

11. The method for controlling temperature and humidity, according to claim 1, wherein the coefficient of performance (COP) of the cooler (1) is measured, recorded and compared to a predetermined COP value, a defrosting cycle for said cooler being initiated if the measured value is less than the predetermined value.

12. The method for controlling temperature and humidity, according to claim 11, wherein an internal volume comprising a cooler having a plurality of cold batteries provided with fins that define a heat exchange surface of the cooler, wherein the ratio between the heat exchange surface of the cooler and the internal volume of the enclosed refrigerated space ranges from 1.0 m.sup.2/m.sup.3 to 1.5 m.sup.2/m.sup.3, and wherein the pitch of the fins positioned on the batteries of the cooler is between 2 mm and 5 mm.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0097] Other objects and advantages of the present invention will appear on reading the following description which relates to embodiments of the invention that are given simply as indicative and non-limiting examples.

[0098] The description will be understood more easily by referring to the accompanying drawings.

[0099] FIG. 1 is a diagrammatic schematic view of an enclosed refrigerated space according to the invention.

[0100] FIG. 2 is a schematic view of the first part of an operating flowchart that shows the control system for the enclosed refrigerated space in the previous figure, in the case where the temperature measured in the enclosed space is higher than the reference temperature.

[0101] FIG. 3 is a schematic view of the second part of the operating flowchart that shows the control system for the enclosed refrigerated space in FIG. 1, in the case where the temperature measured in the enclosed space is less than or equal to the reference temperature.

DETAILED DESCRIPTION OF THE INVENTION

[0102] Cooling and humidification of the enclosed refrigerated space 1 are dependent on a number of components that appear in FIG. 1. Thus, a conventional central cooling unit 2 for producing cold comprising an evaporator/exchanger 3 allows the temperature of a coolant (for example glycol water) used to cool the enclosed space 1 to be controlled. The coolant circuit, outside the enclosed space 1 as such comprises—as well as the central cooling unit 2—a three-way valve 4 which manages a dual circulation loop between the inlet and the outlet of the enclosed space 1: a circulation branch for the coolant is thus redirected from the outlet straight to the inlet, and another branch passes through the evaporator/exchanger 3, their combined flows being managed by the three-way valve 4, which manages the relative flow of coolant from each loop, and more generally the flow of coolant entering the enclosed refrigerated space. A recirculation pump 5 or circulator 5 is positioned downstream of said valve 4, allowing the speed of the coolant to be controlled. Finally, coolant temperature sensors 6, 7 are positioned at the inlet and the outlet respectively of a cooler 10 arranged inside the enclosed space 1.

[0103] Said cooler 10 is made up of a plurality of cold producing batteries 16 connected in parallel to the coolant circulation circuit, typically coolers through which the coolant flows controlled by solenoid valves 17 so that the cooling capacity can be adjusted by adding or removing one or more batteries 16. It should be noted that adjustment of the active exchange surface of the complete heat exchanger which is the cooler 10 can also be seen.

[0104] A plurality of fans 11, the speed of which can be adjusted, varies the flow of air passing through the cooler. The arrows F indicate the direction of the air flows, showing the general direction conferred on the flow, which may however be reversed in some situations. These flows are directed transversally to the batteries 16, in order to provide correct cover of the exchange surface of the cooler 10 and, as a secondary matter, of the entire volume of the enclosed refrigerated space with regard to the overall mixing of the air, the properties of which are modified on contact with the exchange surfaces of the batteries 16. A temperature sensor 12 is positioned at the outlet (in the direction of the air flows indicated by the arrows F) of the cooler 10, in other words at the air blowing point. A humidity level sensor 13 is positioned on the same side. A similar pair of temperature 15 and humidity 14 sensors is positioned at the inlet of the cooler 10, at the return air point.

[0105] The operation of all these components is managed by the automaton from initial reference values mainly for the humidity level and the air temperature. The values of the parameters controlled are adjusted simultaneously and constantly in order to maintain an atmosphere inside the enclosed refrigerated space 1 suitable for the conservation and preservation of various biological products that have a significant water composition, in particular free water, for example plant and animal foodstuffs, plants and trees, etc.

[0106] It is also useful to examine the incidence of variations of the different parameters, taken individually or considered successively, the other parameters being, if applicable, seen as dependent on the parameter in focus, or also considered individually below.

[0107] Concentrating first on control of the ventilation, and thus on control of the fans 11, the sensors that are first used to measure the effects of this control are the return air temperature sensor 15 (or the blown air temperature sensor 12, depending on the direction of ventilation or the choice of the user) and the return air humidity sensor 14. As emphasized repeatedly, the initial parameters remain temperature and humidity, and therefore the ventilation control is clearly observed in the light of the measurements for these parameters.

[0108] Thus, if the measured air temperature is higher than the reference temperature, a first comparison is made with a threshold temperature. If the measured temperature is above this threshold, this indicates a rise in temperature that is much too rapid, probably resulting in too long a period to allow the temperature to fall back within a suitable duration. In this case, the automaton adjusts upwards the air flow reference value for the internal fans 11 suitable for producing a flow of air through the cooler 10. The humidity measurement has no influence during this cycle which could be described as a “temperature priority” cycle, at least for a given time.

[0109] The humidity measurement plays a role if the measured temperature, although too high, is below said threshold. Three cases are then possible.

[0110] If the measured humidity of the air is less than the reference value, the automaton adjusts upwards the air flow reference value for the internal fans 11 producing a flow of air through the cooler 10 and consequently increases the measured humidity of the air. As the temperature of the coolant rises (see the examination of the other parameters below) and the ventilation accelerates, the water found on the exchange surface of the cooler 10 is released into the air by evaporation. Moreover, passing from the liquid state (water) to the gaseous state (water vapor) requires a thermal energy input: this energy is drawn from the ambient air, which results in a cooling of the air. In this process, the water molecules found on the surface of the water gradually change state to vapor, causing the measured humidity to rise and the temperature to fall. Moreover, the greater the flow of air, the better the water present in the ambient air is conserved, reducing condensation on the exchange surface of the cooler 10.

[0111] If the measured humidity of the air is equal to the reference value, the air flow reference value for the internal fans 11 is stabilized by the automaton in a neutral coolant air regulation zone.

[0112] Finally, if the measured humidity of the air is greater than the reference value, the air flow reference value for the internal fans 11 is reduced downwards, so as to reduce the flow of air through the cooler 10 with a view to reducing the measured humidity of the air. In this case, as the ventilation and coolant temperature reduce, the water present in the (moist) air is deposited on the exchange surface of the cooler 10 because the moist air passes over a colder surface, the temperature of which is below that of the dewpoint. The cooled air then loses some of its water vapor by condensation. As the flow of air is reduced, the contact time of the moist air with the cold surface increases, which encourages and further increases condensation.

[0113] Still concentrating on the control of the interior flow of air, this is addressed as follows if the air temperature inside the enclosed refrigerated space this time is at the reference temperature.

[0114] If the measured humidity of the air is also less than the reference value, the automaton adjusts the air flow reference value for the internal fans 11 upwards until said neutral regulation zone is stabilized in order to enrich the air by evaporation of the air trapped on the exchange surface of the cooler 10.

[0115] If the measured humidity of the air is greater than or equal to the reference value, the automaton reduces the ventilation reference value to the minimum in order to limit transmission of the heat released by the electric motors of the fans 11. However, the flow of air must be sufficient to capture the air temperature measurement very precisely and dynamically.

[0116] To accelerate detection of the rise in temperature of the interior air which results from the respiration heat of the products, the direction of ventilation is also reversed. Therefore, the air, being warmed up as a priority, is forced to return to the blow temperature sensor 12. If not, the cooling installation would need more time to capture the rise in temperature, as this would require the air to pass throughout the mass of stored products, and might even warm said products in passing, before returning to the blowing temperature sensor 12. Warming the products must be avoided as it produces temperature differences on the surface thereof, which are sources of conservation issues. As already mentioned, once the refrigeration cycle has been restarted, the direction of ventilation returns to the initial direction.

[0117] Regulation of the atmosphere inside the cold room may also be examined from the perspective of the control of the three-way valve 4, which controls in particular the temperature of the coolant. Returning to the distinctions made previously on the measured temperature and humidity, the following observations may be made.

[0118] Thus, if the measured temperature of the ambient air is higher than the reference temperature, control depends as indicated on a comparison with the above-mentioned threshold temperature. If the measured temperature is above this threshold, the automaton sends a signal to gradually open the three-way valve 4 to cause cold coolant to enter the cooler 10, leading to a lowering of the temperature of the coolant. For a given time, the priority is to reach the reference air temperature in the enclosed space. A maximal difference between the air temperature and the temperature of the coolant (DTmax)—parameterized according to the installation—is maintained with a view to reaching a minimal temperature measurement in the region of the blow sensor 12.

[0119] As already mentioned, the humidity is not measured at this stage as it has no influence during the “temperature priority” cycle. Only once the air temperature approaches the reference temperature does management return to measuring the humidity conditions. The same three cases are then managed by the automaton.

[0120] If the measured humidity of the air is less than the reference value, the automaton sends a signal to gradually close the three-way valve 4, allowing coolant to recirculate in the cooler 10, which causes the temperature thereof to rise. Consequently, the difference (DT) between the temperature of the air measured in the enclosed space 1 and that of the coolant reduces, which reduces condensation of the water present in the air and encourages evaporation of the water initially trapped on the exchange surface of the cooler 10, causing the measured humidity to increase.

[0121] If the measured humidity of the air is equal to the reference value, the automaton stabilizes the three-way valve 4 in a neutral “regulation” zone.

[0122] Finally, if the measured humidity of the air is greater than the reference value, the automaton sends a signal to gradually open the three-way valve 4 allowing colder coolant to enter into the cooler 10, producing there a fall in the temperature thereof, and thus allowing the difference between the air temperature and the coolant temperature to increase. This encourages condensation on the surface of the cooler 10, and eliminates the water present in the moist air, thus reducing the measured humidity.

[0123] Still concentrating on the control of the three-way valve 4, said control is different if the air temperature inside the enclosed refrigerated space 1 is less than or equal to the reference temperature. Thus, if the measured humidity of the air is less than or equal to the reference value, according to the method of the invention, the system closes the three-way valve 4.

[0124] However, if the measured humidity of the air is greater than the reference value, the automaton sends a signal to gradually open the three-way valve 4 until a fixed limit is reached, to cause a minimum amount of cold coolant to enter into the cooler 10, resulting in a fall in the temperature of said coolant in the enclosed space 1, and thus increasing the difference between the air temperature and the coolant temperature. This encourages condensation on the exchange surface of the cooler 10, and eliminates at least a fraction of the water present in the moist air, thus reducing the measured humidity. However, a limit is imposed on this operation to prevent the air temperature from falling too far.

[0125] Regulation of the atmosphere inside the cold room may then be examined from the perspective of the control of the flow of coolant, which it will be recalled is glycol water, for example. More precisely, the coolant input temperature sensor 6 is used to manage the operation of the circulator 5. Referring once again to the distinctions made previously in relation to the measured temperature and humidity, the following observations may be made.

[0126] Firstly, if the measured air temperature is higher than the reference temperature, a comparison is first made with the above-mentioned threshold temperature. If the measured temperature is above this threshold, the temperature priority cycle is set in motion, and the automaton gradually increases the speed of the circulator 5. This increase results in causing cold coolant to enter into the cooler 10, in which a lowering of the temperature of the coolant is produced. As soon as the measured air temperature in the enclosed space 1 approaches the reference temperature, overall control by the automaton goes back to managing the measured humidity.

[0127] If the measured humidity of the air is less than the reference value, the automaton reduces the reference speed of the circulator 5 to increase the temperature of the coolant in the cooler 10. Consequently, the difference (DT) between the temperature of the air measured in the enclosed space 1 and that of the coolant is reduced, which reduces condensation of the water present in the air and encourages evaporation of the water initially trapped on the exchange surface of the cooler 10. The measured humidity increases in proportion.

[0128] If the measured humidity of the air is equal to the reference value, the automaton stabilizes the circulator 5 in a neutral “regulation” zone.

[0129] Finally, if the measured humidity of the air is greater than the reference value, the automaton increases the speed of the circulator 5 in order to obtain a lowering of the temperature of the coolant in the cooler 10 and thus increase the difference between the temperature of the air in the enclosed space 1 and that of the coolant. This helps encourage condensation on the exchange surface of the cooler 10 and helps eliminate the water present in the moist air, thus reducing the measured humidity.

[0130] Still from the point of view of controlling the flow of coolant, management is different if the temperature of the air inside the enclosed refrigerated space 1 is less than or equal to the reference temperature.

[0131] If the measured humidity of the air is less than the reference value, the automaton controls the operation of the circulator 5 with a higher speed until a fixed limit is reached. However, the operating permission given by the automaton to the circulator only exists on condition that the temperature of the coolant is less than or equal to the temperature of the air measured in the enclosed space 1. The object is to encourage condensation on the exchange surface of the cooler 10, but without warming the ambient air.

[0132] If the measured humidity of the air is equal to the reference value, the circulator 5 is stopped by the automaton.

[0133] If the measured humidity of the air is greater than the reference value, the circulator 5 is commanded to operate up to a maximal programmed threshold, in conjunction with the three-way valve 4, to encourage light condensation on the exchange surface of the cooler 10, without the air temperature in the enclosed space 1 falling.

[0134] Finally, regulation of the atmosphere inside the cold room may be examined from the point of view of cooling capacity or active exchange surface, in other words, by managing a plurality of cold batteries 16 in service. The distinctions made previously in relation to the measured temperature and humidity are referred to again below.

[0135] First, if a temperature priority cycle is in progress without the humidity being measured, the automaton opens 100% of the solenoid valves 17 that open the flow of coolant, to cause cold coolant to enter all the batteries 16 of the cooler 10 (see FIG. 1), leading to a lowering of the temperature of the coolant initially present in the batteries 16. This priority cycle, which aims to reach the reference temperature as quickly as possible, is applied for a limited period before the automaton reverts to the operation that is the subject of the following paragraphs, resuming the humidity measurements when the temperature of the ambient air approaches the reference temperature.

[0136] In this case, where a temperature priority cycle is implemented, if the measured humidity of the air is less than the reference value, the automaton opens all the solenoid valves 17 that open the flow of coolant to cause coolant to enter the batteries 16 of the cooler 10 in order to use 100% of the exchange surface thereof to increase the temperature of the coolant in the cooler 10. Consequently, the difference (DT) between the temperature of the air in the enclosed space 1 and that of the coolant is reduced, which reduces condensation of the water present in the air and encourages evaporation of the water initially trapped on the exchange surface of the cooler 10, which ultimately increases the measured humidity.

[0137] If the measured humidity of the air is equal to the reference value, the automaton stabilizes the percentage of open solenoid valves 17 and therefore the percentage of the batteries 16 in operation, in other words, conveying the coolant.

[0138] Finally, if the measured humidity of the air is greater than the reference value, the automaton gradually closes the solenoid valves 17 that open the flow of coolant, so as to use a smaller exchange surface to cause coolant with a lowered temperature to enter only the last battery of the cooler 10 in order to obtain a lowering of the temperature of internal coolant and thus increase the difference between the temperature of the air and that of the coolant. This encourages condensation on said cold battery and eliminates the water present in the moist air, thus reducing the measured humidity while gradually lowering the cooling capacity of the cooler 10.

[0139] FIGS. 2 and 3 synthesize the management of the different parameters that allow accurate control of the atmosphere of the enclosed refrigerated space 1 of FIG. 1. The flowchart clearly shows the preeminence in said control of the temperature and humidity level parameters, and of the tests initially carried out by the automaton on these parameters. As the enclosed space 1 is a cold room, temperature is of course the master parameter for all the management, followed by measurements and tests on the humidity of said enclosed space 1.

[0140] Next come the other parameters or the devices said parameters manage, which can be seen in each branch of the flowchart and are the three-way valve 4, the circulator 5, the cold batteries 16 of the cooler 10 and the fans 11. As seen in detail previously, each device has an impact on at least one parameter.

[0141] In FIG. 2, which shows the control if the temperature measured in the enclosed space 1 is higher than the reference temperature, in other words if refrigeration is not sufficient, the two hypotheses can be clearly distinguished depending on whether or not the temperature exceeds a predetermined threshold. If the threshold is exceeded, meaning that there is an urgent need to take action, priority—or even exclusivity—is given to the processing of the temperature without taking the measured humidity into consideration. It is the farthest left branch in FIG. 2 that is concerned, this case being designated “Priority mode T° C. activated.”

[0142] In this branch, as stated between the two blocks relating to the three-way valve 4 and the circulator 5, regulation is carried out based firstly on a maximal difference reference value between the temperature of the air and that of the coolant, parameterized according to the installation, and secondly on a minimum reference temperature measured by the blow sensor 12 (or by the return sensor 15) and controlled by said maximal programmed difference.

[0143] The other three branches cause the intervention of the measurement of the humidity level, and compare said measurement with the initial measured humidity reference value.

[0144] The same applies to the branches of FIG. 3, which relate to the case where the temperature measured in the enclosed space 1 is less than or equal to the reference temperature. Taking account of the level of measured humidity therefore intervenes in all the hypotheses and consequently generates the three branches that can be seen in this figure.

[0145] In the branch on the left of FIG. 3, the measured humidity of the air is less than the reference value and a measurement is taken of the temperature of the coolant by the sensor 6. If said temperature is less than the temperature measured in the enclosed space 1, the speed of the circulator 5 is increased until a fixed limit is reached. In the reverse hypothesis, the circulator 5 is stopped. The object is to encourage vaporization of water present on the exchange surface of the cooler 10, but without warming the ambient air.

[0146] In the other two branches, it should be noted that the direction of the ventilation is reversed for reasons that take account of the need to speed up measurement of the warming of the ambient air without said air being constrained to pass through the entire mass of the stored products.

[0147] It should be noted that in the branch farthest to the right, the circulator 5 is controlled to operate to a maximum threshold of its maximal flow in conjunction with the three-way valve 4 to encourage light condensation on the cooler 10, without the temperature of the ambient air falling.

[0148] The operating examples above, in conjunction with the figures, are not exhaustive examples of the invention, which on the contrary encompasses variations, notably of structure (number of sensors, cold batteries, etc.).