FR2842588A1 - Small building air conditioning system having inner/outer temperature measured/difference calculated and threshold compared and switch activated when threshold above determined leve - Google Patents

Abstract

The heat evacuation method measures the inner (Tint) and outer temperature (Text). The difference (210) is calculated. The difference (220) is compared with a threshold value. A switch (250) is activated when the threshold is above a determined level.

Description

The present invention relates to a method for evacuating heat released

  inside a room, by variable flow ventilation, and an implementation system. The invention is in the climatic and thermal field and more particularly in the field of air conditioning for small buildings. It typically finds its application in the mechanical ventilation of professional premises containing

  active equipment that dissipates thermal energy.

  The rise of broadband, in particular x-DSL technologies, involves the installation of active equipment, such as concentrators (DSLAM) capable of boosting the copper line, on the premises of telecommunications operators. Such active equipment releases heat and contributes to a significant increase in temperature in these rooms. However, an excessive temperature rise can become detrimental to

  proper functioning of equipment.

  Of course, even if there is no reference, in the

  following the description, only to premises or buildings in

  which are arranged active telecommunication equipment, it should not be forgotten that the invention applies more generally to the ventilation of any type of professional premises in which equipment or

machines dissipate heat.

  To reduce the risks linked to the increase in temperature and to respect the climatic standards relating to the functioning of telecommunications equipment, that is to say in particular the ETSI standards ETS 300-019, various solutions, based on ventilation

  mechanical, have already been considered.

  The invention will now be presented with regard to known methods of ventilation which are illustrated in the following figures: - Figure la represents a block diagram of a first known method of mechanical ventilation, - Figure lb represents the evolution of temperatures inside and outside a room equipped with a first ventilation system operating according to the principle illustrated in Figure la, - Figure 2a shows a block diagram of a second known mechanical ventilation process , - Figure 2b shows the evolution of temperatures inside and outside a room equipped with a second ventilation system operating according to the principle illustrated in the

Figure 2a.

  It is recalled that ventilation consists of sucking stale air from a room to reject it outside and blowing clean air from outside. A first known method of ventilation consists in forcing ventilation when the ambient temperature, prevailing at

  the interior of the room to be ventilated exceeds a certain threshold.

  The block diagram of Figure la illustrates the operation of this process, where Tdecl represents the threshold temperature from which the ventilation is started. In this case, the ventilation works in "all or nothing", that is to say that it is stopped as long as the ambient temperature is below the threshold Tdecl then, beyond this threshold value, it is triggered so to produce a constant air flow D

and maximum Dmax.

  FIG. 1b represents the evolution, over eight days Jl to D8, of the interior and exterior temperatures of a

  room equipped with a system operating according to this process.

  The curve in solid lines corresponds to the interior temperature Tint, and the curve in dotted lines corresponds to the exterior temperature Text. The period referenced VI corresponds to a period during which the ventilation has operated intermittently, and the period referenced VP corresponds to a period during which the ventilation has operated permanently. With this process, it appears that the interior temperature of the room is only exceptionally lower than the outside temperature, which is contrary to the aim sought to remove the heat dissipated in the room. In addition, the indoor temperature fluctuates much like the outside temperature. However, these temperature fluctuations which appear are often too high to be compatible with the aforementioned climatic standards relating to the operation of telecommunications equipment. Furthermore, the periods during which the outside air is blown in are not optimized, so that air is supplied even when it is not essential. However, it should not be forgotten that the supply of outside air promotes the introduction of pollutants and / or humidity which are factors favoring the phenomena

corrosion on equipment.

  To avoid the appearance of temperature gradients, a second method, the schematic diagram of which is illustrated in FIG. 2a, has been envisaged. This second method consists in varying the ventilated air flow as a function of the temperature measured inside the room, ventilation being triggered.

  when the interior temperature exceeds the Tdecl threshold.

  FIG. 2b represents the evolution, over 48 hours HO to H48, of the internal temperature Tint (curve in solid lines) and the external temperature Text (curve in dotted lines) of a room. The ventilation is done by a variable air flow, beyond the triggering temperature Tdecl. The air flow D increases as the interior temperature increases and becomes

  maximum Dmax for a maximum interior temperature Tmax.

  In this case, the temperature gradients are low and compatible with the climatic standards relating to telecommunications equipment. However, in cases where the premises equipped with systems operating according to this process have a low thermal inertia, the variations in the outside temperature are immediately and practically entirely reflected inside. In addition, the interior temperature never drops below the ventilation trigger temperature Tdecl during periods of high heat, i.e. mainly in summer, even if the outside temperature is much lower, as shown in the Figure 2b. No decrease in indoor temperature is therefore actually observed. Consequently, this second ventilation method does not allow either to cool the

  rooms by removing the heat dissipated there.

  In addition, in the two methods which have just been described, it is necessary to configure the systems for implementing the ventilation methods at the time of their installation since the threshold temperatures Tdecl which are fixed differ according to the geographical region in

which they are installed.

  To be able to dissipate the thermal power released by the active equipment and obtain an interior temperature lower than the outside temperature, there are dynamic solutions such as air conditioning, water vaporization or the installation of air / water exchangers. However, these solutions have a significant investment and operating cost. Also, the technical problem which is the subject of the present invention relates to a process for evacuating the heat released inside a room, by variable flow ventilation, which would allow the room to be really cooled and the peaks of heat, due to variations

  outside, without using cold production.

  The solution to the technical problem is obtained, according to the present invention, because the said method comprises the steps consisting in: measuring the temperature inside the room and the temperature outside, - calculating the difference between the inside temperature and the outside temperature, - compare the calculated difference to a threshold value, - start ventilation as soon as the difference

  calculated is greater than said threshold value.

  Thus, the evacuation of heat consists in ventilating the room by bringing outside air whose temperature is lower than the inside temperature. In this way the room is really cooled. In addition, the fact that the process allows variable flow ventilation makes it possible to avoid the appearance of temperature gradients which would be incompatible with the standards in force. The solution to the technical problem is also obtained thanks to a system for implementing the aforementioned method. This system is remarkable in that it comprises: - a means of ventilation intended for evacuating the hot air, - a means of ventilation intended to allow outside air to enter, - two temperature probes intended to measure respectively the indoor temperature and outdoor temperature, - a means of processing the measured temperature values and controlling the ventilation means. Other features and advantages of the invention

  will appear on reading the following description,

  made by way of illustrative but nonlimiting example, with reference to the appended figures which represent: - Figure 3, a block diagram of a heat removal process according to the invention, - Figures 4a and 4b, diagrams of a possible embodiment of a system for implementing the method of FIG. 3, respectively in top view and in section, - FIG. 5, a flowchart illustrating the essential steps of an evacuation process heaters operating according to the principle of FIG. 3, - FIGS. 6a and 6b, respectively a flow diagram of an alternative embodiment of the method illustrated in FIG. 5, - FIG. 7, curves representing the evolution, during 72 hours, on the one hand the interior and exterior temperatures of a room, and on the other hand the control voltage applied to the ventilation means, - Figure 8, curves representing the air flow to be supplied by the means of ventilation in operation ion of the thermal power dissipated in a

local.

  FIG. 3 illustrates the operation of a process for evacuating heat released inside a room, according to the present invention. This process consists in particular in varying the flow rate D of ventilated air in proportion to the variation in the deviation of

  temperature DT between the inside of the room and the outside.

  Thus, the variable ventilation makes it possible to increase the air flow rate D, up to a maximum Dmax, when it is colder outside, that is to say when the difference DT between the inside temperature and the outside temperature is maximum DTmax, and conversely the flow rate D is minimum Dmin when it is hot outside, that is to say when the difference DT is minimum and substantially equal to the threshold value DTmin. This variation in flow therefore makes it possible to regulate the temperature inside the room and to avoid

  the appearance of high temperature gradients.

  The outside air is therefore automatically brought inside the room only when its temperature is lower than the inside temperature, so as to allow cooling of the room and evacuation of the thermal energy dissipated by the equipment. As an example, the threshold value DTmin can be set

substantially equal to 3 or 40C.

  This process also involves the well-known phenomenon of thermal inertia in buildings. Thus, when the difference DT between the internal temperature Tint and the external temperature Text is less than the threshold value DTmin, the ventilation is stopped. The thermal power P released by the active equipment is then partly discharged to the outside, partly stored by the horizontal and vertical walls of the room, and partly stored in the ambient air. All these exchanges allow the ambient temperature Tint, prevailing inside the room, to increase more slowly than the

outside temperature.

  Then, when the temperature difference DT between the interior and the exterior is sufficient, the ventilation operates with a flow proportional to this temperature difference. Due to the introduction of cooler air, the ambient temperature Tint prevailing inside the room decreases, and the heat stored in the room

  and its walls are evacuated to the outside.

  Figures 4a and 4b show an example of a system for implementing this method respectively in top view and in section. In these two figures, the same references are used to designate the same elements. The heat evacuation system is installed in a room 100 in which are active equipment 150 dissipating thermal energy,

  such as telecommunications equipment for example.

  A ventilation means 110, such as a fan for example, associated with an air discharge mouth 115 makes it possible to extract the ambient air from inside the room and to reject it towards the outside (as shown diagrammatically). by the black arrow). The air discharge mouth 115 and the associated fan 110 are preferably positioned at the

  higher in the room to evacuate the maximum amount of hot air.

  When possible, it is advantageous to place this extractor on the roof. Furthermore, it is preferable that the air discharge mouth is not exposed to the prevailing local winds to avoid a backflow of air inside the room through this mouth. If, despite everything, this mouth is exposed to the winds, it would be advisable

  protect it with a wind screen.

  Aeration means 120, constituted by an air inlet mouth for example, is further provided to allow air to enter from the outside towards the inside of the room 100 (as shown schematically by the 'other black arrow). This ventilation means 120 is preferably placed as close to the ground, and to the east or north of the room so that the temperature of the outside air which is brought inside is as cool as possible. The position of this aeration means 120 must be as far as possible from the ventilation means 110 intended for rejecting air in order to benefit from a large buffer volume allowing homogenization of the temperature at

inside the room.

  In addition, one or more closing / opening means (s), of the motorized register (s) or flap (s) type, can (for example) be provided in the mouth 115 for rejection of air and / or in the air vent 120. Such a means makes it possible, for example, to close access to the interior of the room when the outside temperature Text is too low, in winter for example, and thus avoid a sudden drop in the interior temperature which would risk disturbing the operation.

equipment.

  The air inlet and outlet vents 120, 115 must have dimensions compatible with the maximum authorized speeds and defined in the ETSI ETS 300-019 standards. The speed limit tolerated by ETSI standards is 5m / s. The calculation of the size of the outlets is given by conventional mathematical relations of the mechanics of the fluids linking in particular the flow rate, the flow area and the flow rate. The flow rate is for example given by the curves C4 to C6 in FIG. 8, as a function of the thermal power P to be removed. To simplify, the surface of the mouths is proportional to the

  ratio of the calculated flow to the discharging speed.

  A temperature probe 131 placed outside the room and in the air flow passing through the aeration means 120 makes it possible to measure the outside temperature, while another probe 132 placed inside the room 100, allows to measure the temperature

  prevailing inside the room.

  Finally, a processing and control means, not shown in FIGS. 4a and 4b, makes it possible on the one hand to process the measured temperature values in order in particular to calculate the difference DT = Tint - Text, and on the other hand to control the means 110 ventilation. It is for example constituted by a regulator equipped with a specific microprocessor. It can for example be a commercial regulator modified so that it can make calculations from two temperature measurements and control the ventilation means from the calculation (s) performed. The motorized damper (s) or flap (s), possibly placed in the air outlet 120 and / or in the outlet mouth 115, is (are) also

  ordered by this processing and control means.

  The flowchart in Figure 5 shows the essential steps of the heat removal process, the

  principle has been explained with reference to Figure 3.

  The first step 200 consists in measuring the ambient temperature Tint inside the room, by means of the probe 132, and the outside temperature Text by means of the probe 131. These measured quantities are transmitted to the processing and control means. The processing means calculates in particular the difference DT between the interior temperature and the exterior temperature (step 210), then it compares, in step 220, the value DT calculated with a threshold value DTmin previously

  recorded in a storage means.

  As long as the calculated value DT is lower than this threshold value DTmin, the ventilation is stopped, but as soon as the difference DT reaches and exceeds this threshold value DT min, then the processing and control means controls (step 250) the setting in operation of ventilation V. In order to be able to vary the flow rate D of the means of

  ventilation, other parameters are also stored in one or more storage means.

  Thus, a value DTmax, corresponding to the maximum value of the calculated difference DTmax beyond which the air flow will be constant and maximum, is also defined and pre-recorded. The control means can therefore vary the flow rate, depending on the variation of DT between a minimum value DTmin and a maximum value DTmax. To vary this flow rate, it suffices to vary the control voltage Tc applied to the ventilation means. Minimum control voltages Tcmin and maximum Tcmax are therefore also pre-recorded in the (s)

means of storage.

  In a variant, illustrated in FIG. 6a, another parameter is also pre-recorded in a storage means and defined another threshold called "low limit temperature" TLB, which is the limit temperature below which the ventilation must be stopped because the ambient temperature inside the room is too cold. Indeed, the ETSI ETS 300-019 standards also define low temperatures below which it is preferable not to operate telecommunications equipment, so as not to damage them. Thus, an additional step referenced 215 in FIG. 6a, consists in comparing the

  indoor temperature value Tint at TLB threshold.

  In this case, ventilation V is only triggered (step 250) when, on the one hand, the difference DT reaches and exceeds the threshold value DTmin and, on the other hand, the internal temperature Tint is greater than the temperature threshold TLB

low limit.

  FIG. 6b represents a flow diagram of another variant of this method. This variant consists in adding an additional step when the air vent 120 and / or the air exhaust mouth 115 is (are) equipped with register (s) intended to close the access to the inside the

  local when the outside temperature is too low.

  In this case too, the parameter defining the low limit temperature TLB is pre-recorded in a storage means. Thus, when the interior temperature Tint is below the threshold defined by the "low limit temperature" TLB, the register (s) must not

(must) not be open.

  A control voltage makes it possible to control the opening or closing of these registers. Thus, no voltage is for example applied when the registers must be closed, while a voltage is for example maintained at 10 volts as long as the registers

must remain open.

  Consequently, step 215 consists in comparing the interior temperature Tint with this other threshold value TLB and, as soon as it is greater than this threshold TLB, the processing and control means controls the opening (additional step 230) registers to save

access to the room.

  In step 220, the control means verifies that the

  threshold value DTmin has been reached.

  Finally, in step 245, a logic "AND" gate, for example, makes it possible to check whether the two preceding conditions are met, that is to say if one (of) accesses to the room has (been) provided (s) and if the calculated DT difference is greater than or equal to the threshold value DTmin. It is only when these two conditions are met that a control voltage Tc is applied to the ventilation means in order to trigger ventilation V (step

250).

  FIG. 7 represents curves illustrating the evolution, during 72 hours HO to H72, on the one hand of the interior (curve Cl), and exterior (curve C2) temperatures, and on the other hand of the voltage Tc applied to the ventilation means in order to control the flow

air (curve C3).

  During ventilation V the indoor temperature is always higher than the outdoor temperature. In the example illustrated in Figure 7, it is about 7 to 80C higher. The indoor temperature gradually decreases during ventilation until it becomes close to the outdoor temperature, or even lower, i.e. until the difference DT becomes lower than the threshold value DTmin and that the ventilation is stopped Vstop. The ventilation starts again as soon as the calculated DT difference

  reaches this threshold again.

  Furthermore, in the example illustrated in FIG. 7, the ventilation means is controlled by an alternating voltage Tc of the order of 230 volts. This figure illustrates the variation of the control voltage Tc applied to the ventilation means. This variation is proportional to the variation of the calculated DT difference, and it makes it possible to vary the air flow and thus avoid excessive heat peaks. Thanks to this control of the ventilation means to vary the air flow, the temperature fluctuations inside the room remain

  compatible with current standards.

  The dimensioning of the ventilation means is mainly dependent on the thermal power P to be evacuated and the pressure drops of the aeraulic circuit. FIG. 8 represents curves C4 to C6 of the flow rate D of the ventilation means necessary for removing the thermal power P dissipated in the room. The flow rate D of the ventilation means to be used is also a function of the thermal inertia of the building. Thus, the curves C4 to C6 correspond to a building having respectively a

  low inertia, medium inertia, and strong inertia.

  In addition, the fan must be dimensioned in anticipation of the rise in thermal load of the room. The fact that the fan is oversized is therefore not a problem since the regulation will adapt the

  air flow at the thermal load of the room.

  In another alternative embodiment, a hygrometric probe can also be connected to the processing and control means in order to take into account the degree of hygrometry prevailing inside the room for processing the data and controlling the means of ventilation. Indeed the degree of hygrometry allows to slightly modify the regulation parameters in particular

  in case the humidity reaches high levels.

  In this case, this action causes a shift, towards

  higher values, threshold temperatures.

  According to another variant, a switch can also be added and connected to the processing and control means to allow two types of operation depending on the periods of the year. In particular, the prerecorded parameters may differ depending on the winter or summer season. Thus, the threshold value DTmin can be set at a smaller value in summer than in winter, since cooling is more difficult to perform. Depending on the position of the switch, the threshold values, pre-recorded in a storage means, which will be selected for the

  implementation of the process will not be the same.

  Finally, provision can also be made to pre-register another threshold value called "high limit temperature" TLH. Thus, in the case where the interior temperature Tint is greater than or equal to this high limit TLH temperature, an alarm is triggered and the ventilation is switched on so that the flow is maximum, in order to create a current of air and to drive out maximum air

  vitiated, whatever the outside temperature.

  The method and the implementation system which have just been described with reference to the appended figures are only illustrations and are in no way limited

to these examples.

  An advantage of this process lies in the fact that it actually allows the heat released by active equipment to be removed in a room, and therefore to cool the room. Furthermore, ventilation is optimized because it only works when the outside temperature is lower than the inside temperature, so that the outside air is not brought in in quantities more than necessary. As a result, the risks of introducing

  pollutants and / or humidity are minimized to the maximum.

  Finally, the fact of ventilating with respect to a difference in temperature, and no longer with respect to a single temperature, has the advantage of being able to overcome the geographic region in which the implementation system is installed, it that is to say to be able to keep the same parameters for the processing

  data, regardless of region.

Claims (8)

  1. Method of evacuating heat released inside a room, by variable flow ventilation, characterized in that it comprises the steps consisting in: - measuring (200) the temperature (Tint) inside of the room and the temperature (Text) outside, - calculate (210) the difference (DT) between the inside temperature (Tint) and the outside temperature (Text), - compare (220) the difference (DT) calculated at a threshold value (DTmin), - trigger (250) ventilation as soon as the calculated difference (DT) is greater than the threshold value (DTmin).   2. Method according to claim 1, characterized in that an additional step consists in comparing (215) the interior temperature (Tint) with another threshold value defining a low limit temperature (TLB), and in that the ventilation is triggered (250) when on the one hand the internal temperature (Tint) is higher than the lower limit temperature (TLB) and on the other hand the difference (DT) calculated between the internal temperature (Tint) and the external temperature (Text) is   greater than the threshold value (DTmin).   3. Method according to one of claims 1 to 2,   characterized in that an additional step consists in comparing (215) the interior temperature (Tint) measured with a low limit temperature (TLB) and in providing (230) at least one access to the room when said interior temperature (Tint) is higher at said low limit temperature (TLB), and in that the ventilation is triggered (250) when on the one hand the said access (s) has (have) been arranged and on the other hand the difference (DT) calculated between the indoor temperature (Tint) and the outdoor temperature (Text) is higher than said threshold value (DTmin).   4. Method according to one of claims 1 to 3,   characterized in that a control voltage (Tc) applied to control the ventilation varies between a minimum value (Tcmin) and a maximum value (Tcmax), depending on the difference (DT) calculated between the interior temperature (Tint) and the outside temperature (Text).   5. Method according to one of claims 1 to 4,   characterized in that an alarm is triggered when the interior temperature (Tint) exceeds   a high limit temperature (TLH).   6. System for implementing the method according to one   of claims 1 to 5, characterized in that it   includes: - a ventilation means intended to evacuate the hot air, - a ventilation means intended to let in the outside air, - two temperature probes intended to measure respectively the inside temperature (Tint) and the outside temperature (Text), - a means of processing temperature values   measured and control of the ventilation means.   7. System according to claim 6, characterized in that it further comprises at least one closing / opening means, controlled by the processing and control means, intended to provide at least one access to the room when the internal temperature ( Tint) is higher than the temperature low limit (TLB).   8. System according to one of claims 6 to 7,   characterized in that it further comprises a hygrometry probe.