US20090241555A1

US20090241555A1 - Method of controlling a device including hilsch-ranque vortex tubes

Info

Publication number: US20090241555A1
Application number: US12/416,465
Authority: US
Inventors: Jean-Pascal SERRE
Original assignee: S I R S E
Current assignee: S I R S E
Priority date: 2008-04-01
Filing date: 2009-04-01
Publication date: 2009-10-01
Also published as: FR2929382A1; FR2929382B1; CA2659550A1; EP2107321A1

Abstract

A method of controlling a device for air conditioning (80) or cooling by refrigeration (10) or heating the interior of a sealed chamber (12), the device (10, 80) including at least one compressed air source (16, 30) which supplies at least one Hilsch-Ranque tube (24), called “vortex” tube, with compressed air at an injection pressure (P_inj), is characterized in that a tapered relief valve (48) of the tube (24) is preset so that the first (FC) and second (FF) fractions of cold and hot air are constant while the method is running and in that it includes a step (E3, C4) for controlling the compressed air injection pressure (P_inj). A device for implementing such a method is also described.

Description

The invention relates to a method of controlling a device for air conditioning or cooling the interior of a sealed chamber including at least one Hilsch-Ranque tube.
The invention relates more particularly to a method of controlling a device for air conditioning or cooling by refrigeration or heating the interior of a sealed chamber, the device comprising at least one compressed air source which supplies at least one Hilsch-Ranque tube, called “vortex” tube, with compressed air at an injection pressure, the Hilsch-Ranque vortex tube comprising:
at least one tangential orifice for injecting compressed air inside the Hilsch-Ranque vortex tube which is arranged close to a first end of the Hilsch-Ranque vortex tube, the injected air forming a first incoming stream of swirling air towards a second end (38) of the Hilsch-Ranque vortex tube;
a tapered relief valve which partially blocks off a first expulsion orifice of the second end of the Hilsch-Ranque vortex tube so that a first fraction of the incoming hot air stream is expelled outside the chamber while a second fraction of the air stream is reflected towards the first end of the Hilsch-Ranque vortex tube forming a second concentric swirling air stream inside the first swirling stream, the reflected air stream being cooled by heat exchange with the incoming air stream;
a “cold” outlet orifice for the reflected air which is arranged at the first end of the Hilsch-Ranque vortex tube so as to allow the second fraction of the cold air stream to leave inside the chamber.
The air conditioning or cooling devices generally use heat-transfer fluids considered as pollutants such as chlorofluorocarbons (CFC).
To overcome this problem, the production of cold air by using tubes called Hilsch-Ranque vortex tubes is known, as disclosed, for example, in the document U.S. Pat. No. 1,952,281.
The regulation of the temperature inside a chamber cooled or air conditioned by such devices is generally controlled by acting on the cold air flow leaving the first end of the tube. This is done by adjusting the fraction of hot air expelled through the second end of the tube by acting on the tapered relief valve.
However, such a control method entails acting on the tapered relief valve through the intermediary of a motor. Such a device therefore includes moving parts which are likely to be prematurely worn.
Now, it is essential, in particular for the cooling device, to have a robust and reliable device. In practice, if a failure occurs on a cooling device for a cold room, the cold subsystem, which ensures that the cooled elements are well conserved, risks being broken.
Furthermore, such a control method induces a superfluous energy consumption, in particular for compressing the injected air, because, in the event of a weak cold air flow, a large fraction, called hot fraction, of the injected air is expelled as pure loss through the expulsion orifice of the second end of the tube.
To overcome these problems, the invention proposes a control method of the type described previously, characterized in that the tapered relief valve is preset so that the first fraction of hot air and the second fraction of cold air are constant while the method is running and in that it comprises a step for controlling the compressed air injection pressure.
According to other characteristics of the invention:
the outlet temperature of the cold air stream is controlled by acting only on the injection pressure of the air into the Hilsch-Ranque vortex tube according to a predetermined control law;
the method comprises a step for calculating the outlet temperature of the cold air stream prior to the step for controlling the injection pressure during which said outlet temperature is calculated by subtracting a predetermined constant value from the compressed air injection temperature,
and the method also comprises a step for correcting the calculated cold air stream outlet temperature, which is triggered when said outlet temperature during the preliminary calculation step is less than a minimum temperature and during which the outlet temperature is corrected so as to be greater than or equal to said minimum temperature;
the compressed air source is an air compressor which sucks in ambient air from outside the chamber, the injection temperature being proportional to the external temperature of the chamber;
the chamber is a passenger compartment of a motor vehicle in which the air conditioning device is installed and the air compressor is driven by the heat engine of the motor vehicle through the intermediary of a hydraulic pump and a hydraulic motor;
the injection pressure is controlled by pulses at an injection pressure which is predetermined, the duration of each pulse being determined in such a way that the chamber is maintained at a setpoint temperature;
the duration of each pulse is determined as a function of the ambient temperature inside the chamber, of the injection temperature of compressed air into the Hilsch-Ranque vortex tube, and of the setpoint temperature;
the duration of each pulse is determined by taking into account the balance between the sum of the heat losses through the walls of the chamber per time unit and the quantity of heat to be removed to cool the air inside the chamber to the setpoint temperature, and the quantity of heat likely to be absorbed by the cold air leaving each Hilsch-Ranque vortex tube for said time unit;
the air is dried by drying means before its injection into each Hilsch-Ranque vortex tube so that its dew point is less than the air outlet temperature.
The invention also relates to a device for implementing the method produced according to the teachings of the invention, characterized in that it comprises a plurality of Hilsch-Ranque vortex tubes which are fed in parallel by at least one common compressed air source and in that each Hilsch-Ranque vortex tube includes a tapered relief valve that can be adjusted only manually.

Other features and benefits will become apparent while reading the detailed description that follows, for an understanding of which reference should be made to the appended drawings in which:

FIG. 1 is a diagram which represents a cooling device installed in a refrigerated transport vehicle;

FIG. 2 is an axial cross-sectional view which represents a Hilsch-Ranque vortex tube;

FIG. 3 is a block diagram which represents a method of controlling the refrigerating cooling device of FIG. 1;

FIG. 4 is a diagram which represents an air conditioning device installed on board a motor vehicle;

FIG. 5 is a block diagram which represents a method of controlling the air conditioning device of FIG. 4.

Hereinafter in the description, elements that have identical, analogous or similar functions will be designated by the same reference numbers.
Hereinafter in the description, an axial orientation directed from back to front indicated by the arrow “A” in FIG. 2 will be adopted in a non-limiting manner.
FIG. 1 represents a refrigerating cooling device 10 which is intended to cool a hermetically sealed chamber 12. The sealed chamber 12 is in this case formed by a cold chamber of a refrigerated transport motor vehicle (not represented) in which the cooling device 10 is installed.
According to a non-represented variant of the invention, the cooling device 10 is also adapted to cool an immobile refrigerating chamber.
The chamber 12 is sealed horizontally in all directions by four vertical walls 14 and vertically in both directions by a top wall (not represented) and by a bottom wall (not represented).
The walls 14 are equipped with means of thermally insulating the chamber 12 from the outside. The thermal insulation means are characterized by their general thermal transmission coefficient “K”.
One of the walls of the cold chamber is also equipped with an access door (not represented) that is thermally insulated and is likely to be sealed hermetically.
The chamber 12 is intended to be maintained at a setpoint temperature “θ_c” by the cooling device 10. The setpoint temperature “θ_c” is, for example, less than 0° C. The setpoint temperature “θ_c” is, for example, −25° C.
The cooling device 10 includes at least one compressed air source. The cooling device 10 in this case includes two compressed air sources.
A first compressed air source 16 is formed by an air compressor 16 which is driven by an electric motor or heat engine. The motor is advantageously autonomous and independent of the engine (not represented) pulling the vehicle in order to ensure continuous operation of the air compressor 16 even when the engine pulling the motor vehicle is stopped.
The air compressor 16 includes a suction duct 18 through which the air outside the chamber 12 is sucked in, and it includes a discharge duct 20 through which the compressed air is discharged from the air compressor 16. The air compressor 16 is, for example, selected for the air to be compressed at a constant pressure between 7.5 and 10.5 bar.
The discharge duct 20 is connected to a duct 22 supplying Hilsch-Ranque vortex tubes 24 through the intermediary of a three-way supply valve 26 controlled by an electronic control unit 28.
A second compressed air source 30 is formed by air accumulators 30, such as cylinders. The air accumulators 30 are, for example, capable of storing 300 litres of compressed air at a pressure of 300 bar.
This second compressed air source 30 is reserved for backup use, enabling the cooling device 10 to operate when the air compressor 16 has failed. Thus, it is possible to act on the air compressor 16 and avoid breaking the cold subsystem.
The air accumulators 30 are also connected to the supply duct 22 through the intermediary of the third way of the supply valve 26.
The supply valve 26 can thus occupy a first position in which the supply duct 22 is fed with compressed air only by the air compressor 16, a second position in which the supply duct 22 is fed with compressed air only by the air accumulators 30, and a third total closure position in which the supply duct 22 is totally cut off from both compressed air sources 16, 30.
The cooling device 10 includes a plurality of Hilsch-Ranque vortex tubes 24 which are supplied in parallel by at least one supply circuit 32 supplied with compressed air by the supply duct 22.
The cooling device 10 includes, for example, three Hilsch-Ranque vortex tubes 24. It will, however, be understood that this number is given purely way of example and that the cooling device 10 is likely to include at least one Hilsch-Ranque vortex tube 24.
Because of the humidity of the air sucked in by the air compressor 16, and as will be explained in more detail hereinbelow, the cooling device 10 here includes two parallel compressed air supply circuits 32A, 32B. The Hilsch-Ranque vortex tubes 24 are likely to be supplied alternately by one then the other of the supply circuits 32A, 32B.
In a non-limiting manner, there are three Hilsch-Ranque vortex tubes 24. They are all identical, so hereinafter just one of these tubes 24 will be described.
A Hilsch-Ranque vortex tube 24 is represented in more detail in FIG. 2. It comprises a tubular body 34 which is cylindrical of revolution with longitudinal axis which comprises a first front end 36 and a second rear end 38.
A tangential orifice 40 for injecting compressed air inside the tubular body 34 is arranged close to the first front end 36 in an inlet chamber 42. The injection orifice 40 is arranged so that the injected air forms an incoming swirling air stream 44 towards the second rear end 38 of the tubular body 34.
The inlet chamber 42 is also configured so as to provoke an acceleration of the rotation of the injected compressed air. Under the effect of the centrifugal force, the air pressure at the periphery of the tubular body 34 increases, and a depression is formed inside the incoming swirling air stream 44.
The rear end 38 of the tubular body 34 is open through an expulsion orifice 46. A tapered relief valve 48 partially blocks off the expulsion orifice 46 of the second rear end 38 of the tubular body 34. The tapered relief valve 48 presents a tapered front face coaxial to the tubular body 34 so that the top of the cone is facing towards the interior of the tubular body 34. The diameter of the base is substantially equal to the diameter of the expulsion orifice 46.
The tapered relief valve 48 can be set axially, for example by means of a screw (not represented), so as to be able to axially separate the periphery of the base of the tapered relief valve 48 from the edge of the expulsion orifice 46.
A first fraction “FC” of the incoming swirling air stream 44 is expelled outside the chamber 12 through the space reserved between the tapered relief valve 48 and the edge of the expulsion orifice 46 in the form of a hot air stream 50 while a second fraction “FF” of the incoming swirling air stream 44 is reflected towards the front end 36 of the tubular body 34, forming a second concentric swirling air stream 52 inside the first incoming swirling air stream 44.
The reflected swirling air stream 52 is cooled by heat transfer radially towards the incoming swirling air stream 44.
The first front end 36 of the tubular body 34 is sealed by a radial wall 54 in which is formed an outlet orifice 56, called cold orifice, so as to allow the second fraction “FF” of the reflected swirling air stream 52 to leave in the form of a cold air stream 58 inside the chamber 12.
Such a Hilsch-Ranque vortex tube 24 operates under the action of the injected compressed air with air rotation speeds that are, for example, of the order of 500000 to 1000000 revolutions/min. These rotation speeds provoke air jet noises which are advantageously muffled by fitting a silencer to the rear expulsion orifice 46 for the hot air stream 50.
As a variant, or in combination, a silencer can be arranged at the front outlet orifice 56 of the cold air stream 58.
The outlet temperature “θ_SF” of the cold air stream 58 depends mainly on three parameters, which are the injection pressure “P_inj”, the air injection temperature “θ_inj” and the fraction “FC” of the hot air stream 50 expelled through the tapered relief valve 48.
As a general rule, the temperature drop between the air injection temperature “θ_inj” and the cold outlet temperature “θ_SF” is globally inversely proportional to the injection pressure “P_inj”.
The hot air stream 50 expelled by the Hilsch-Ranque vortex tubes 24 is expelled outside the chamber 12 through the intermediary of an exhaust duct 59 which includes inlet orifices which are each connected to an expulsion orifice 46 of an associated Hilsch-Ranque vortex tube 24 and an exhaust orifice 61 which is arranged outside the refrigerating chamber 12.
For a refrigerating cooling application, the outlet temperature “θ_SF” of the cold air stream 58 is generally less than 0° C. Now, the compressed air includes a percentage humidity such that the outlet temperature “θ_SF” of the cold air stream 58 leaving the Hilsch-Ranque vortex tube 24 is less than the dew point. This humidity then risks being condensed and then forming ice inside the chamber 12.
To avoid this problem, an air dryer 60A, 60B is inserted into each supply circuit 32A, 32B so that the compressed air is dried before being injected into the Hilsch-Ranque vortex tubes 24. Thus, the air will be dried so that its dew point is lowered below the cold air outlet temperature “θ_SF”, for example the dew point of the dried air is −40° C.
The air driers 60A, 60B have to be regularly regenerated in order to expel the retained humidity water in steam form. By having two parallel supply circuits 32A, 32B, it is possible to regenerate the air drier 60A, 60B of a supply circuit 32A, 32B while the Hilsch-Ranque tubes 24 are supplied by the other supply circuit 32B, 32A.
In the interests of optimizing the overall energy consumption of the cooling device 10, the heat used to evaporate the humidity is supplied by the hot air stream 50 expelled by the Hilsch-Ranque vortex tubes 24.
The hot air stream 50 is led to the air driers 60A, 60B through a tap duct 62 which is top connected to the exhaust duct 59. The tap duct 62 includes a fork in order to supply in parallel each of the two reheating circuits upstream of the associated air drier 60A, 60B.
The hot air stream 50 is intended to enter into the air drier 60A, 60B via the same inlet orifice as the compressed air. Thus, each reheating circuit is connected to an associated supply circuit 32A, 32B upstream of the associated air drier 60A, 60B.
The tapping of the hot air stream 50 in the tap duct 62 is controlled by a three-way tap valve 64 which is arranged at the connection between the exhaust duct 59 and the tap duct 62.
Then, the switching of the duly diverted hot air stream 50 to one or other of the air driers 60A, 60B is controlled by a three- way regulation valve 66A, 66B which is arranged at the connection between each supply circuit 32A, 32B and tap duct 62. The regulation valves 66A, 66B are controlled between a supply position in which the hot air stream 50 is completely blocked, the compressed air supplying the associated air drier 60A, 60B, and a drying position in which a mixture of compressed air and hot air stream 50 supplies the associated air drier 60A, 60B.
The moist hot air stream 50 leaving the regenerated air drier 60A, 60B is then discharged outside the refrigerating chamber 12 without being injected into the Hilsch-Ranque vortex tubes 24. To this end, a three- way discharge valve 68A, 68B is arranged in each supply circuit 32A, 32B downstream of the air drier 60A, 60B. The discharge valves 68A, 68B include a discharge orifice 70 which is connected to the exterior of the chamber 12. The discharge valve 68A, 68B is likely to occupy a regeneration position in which the air that arrives from the air drier 60A, 60B is entirely diverted to the discharge orifice 70 and a supply position in which the air that arrives from the air driver 60A, 60B is entirely directed to the injection orifice 40 of the Hilsch-Ranque vortex tubes 24.
Furthermore, to monitor the effectiveness of the air driers 60A, 60B, each supply circuit 32A, 32B is provided with a hygrostat 72 for measuring the humidity ratio “TH” of the air circulating in the associated supply circuit 32A, 32B downstream of the air driers 60A, 60B. Each hygrostat 72 is likely to send the electronic control unit 28 a signal representative of the measured humidity ratio “TH”.
Moreover, the air introduced inside the chamber 12 through the intermediary of the cooling device 10 is likely to increase the air pressure inside the chamber 12 which is hermetically sealed. To avoid having the pressure increase too much, a solenoid valve 74 is provided, which is controlled between a position in which it blocks a balancing orifice of a wall of the chamber 12 and a decompression position in which the pressurized cold ambient air can leave towards the exterior through the balancing orifice under the effect of the pressure difference between the inside and the outside of the chamber 12.
The solenoid valve 74 is controlled by the electronic control unit 28 according to the measurements made by a differential pressure stat 76 which is arranged in a wall of the refrigerating chamber 12 and which measures the differential pressure “ΔP” between the inside and the outside of the chamber 12. The differential pressure stat 76 can send a signal representative of the measurement of the differential pressure “ΔP” to the electronic control unit 28.
Thus, when the measured differential pressure “ΔP” between the pressure inside the chamber 12 and the pressure outside the chamber 12 exceeds an overpressure threshold, the solenoid valve 74 is controlled to its decompression position so as to expel the air causing the overpressure.
The solenoid valve 74 is controlled to its blocking position when the measured differential pressure “ΔP” between the inside and the outside of the chamber 12 is less than or equal to a second safety threshold. The safety threshold is chosen so that the pressure inside the chamber 12 is always greater than the pressure outside in order to avoid the hot outside air penetrating inside the chamber 12 through the balancing orifice.
The invention proposes a control method in which the compressed air source 16, 30 is controlled by the electronic control unit 28.
To implement the method set up according to the teachings of the invention, the tapered relief valve 48 is preset in such a way that the first “FC” and second “FF” air fractions are constant while the method is running. The tapered relief valve 48 is set as a preliminary step according to the maximum flow rate of the cold air current 58 likely to be produced.
Thus, the method set up according to the teachings of the invention does not entail acting on the structural elements that form the Hilsch-Ranque tubes 24. This is all the more beneficial when the cooling device 10 includes a plurality of Hilsch-Ranque vortex tubes 24.
The tapered relief valve 48 is, for example, set in such a way that the flow of hot air stream 50 expelled through the expulsion orifice 46 is equal to the flow of cold air stream 58 leaving through the cold outlet orifice 56, in other words, the first “FC” and second “FF” air fractions are equal to 50%.
The outlet temperature “θ_SF” of the cold air stream 58 is controlled by acting solely on the injection pressure “P_inj” of the compressed air into the Hilsch-Ranque vortex tube 24 according to a predetermined control law.
In this application for refrigeration cooling, the injection pressure “P_inj” is more particularly controlled by pulses at an injection pressure “P_inj” which is predetermined in such a way that the ambient temperature “θ_int” inside the chamber 12 is maintained equal to a setpoint temperature “θ_c”.
Hereinafter, the ambient temperature inside the chamber 12 will be called internal temperature “θ_int”.
At the time of the pulses, the outlet temperature “θ_SF” of the cold air stream 58 is determined according to a number of parameters. As an example, the parameters can be set as follows:
the injection pressure “P_inj” is set at 7 or 10 bar according to the type of air compression 16 used;
the injection temperature is set at 21° C.;
the hot “FC” and cold “FF” air stream fractions are set at 50% by presetting the tapered relief valve 48.
Thus, the outlet temperature “θ_SF” of the cold air stream 58, at the time of the pulses, is predetermined. The air compressor 16 is, for example, selected so that the outlet temperature “θ_SF” is substantially equal to −30° C. for an injection temperature “θ_inj” of approximately 21° C. The temperature of the hot air stream 50 is, for example, equal to 120° C.
The duration “t” of each pulse is determined according to internal temperature “θ_int”, the injection temperature “θ_inj” of compressed air into the Hilsch-Ranque vortex tube 24, and the setpoint temperature “θ_c”.
More particularly, the duration “t” of the pulse is determined by taking into account the following equation “EQ1”:
Q _m,of =Q _dep +Q _ref “EQ1”:
in which Q_m,afrepresents the quantity of heat likely to be absorbed by the cold air stream 58 leaving the Hilsch-Ranque vortex tube 24 for a time unit “t”;
Q_deprepresents the heat loss through the walls of the chamber 12 for said time unit “t”; and
Q_refrepresents the quantity of heat to be removed to cool the ambient air inside the chamber 12 to the setpoint temperature “θ_c”.
The heat loss Q_depthrough the walls of the chamber 12 is calculated according to the following equation “EQ2” which is well known to those skilled in the art:
Q _dep =K·S _T·(θ_ext−θ_C)·t “EQ2”:
in which “K” represents the general thermal transmission coefficient of the walls of the chamber 12 expressed in W/m².K;
S_Trepresents the surface area of the walls in m²;
θ_extrepresents the ambient temperature of the air outside the chamber 1 2 in K, hereinafter called external temperature;
“θ_c” represents the setpoint temperature in Kelvin.
The quantity of heat Q_refto be removed to cool the ambient air inside the chamber 12 is calculated according to the following equation “EQ3” which is well known to those skilled in the art:
Q _ref=ρ_int ·V·C _p·(θ_int−θ_C) “EQ3”:
in which ρ_intrepresents the density of the ambient air inside the chamber 12 expressed in kg/m³;
V represents the volume of the chamber 12 expressed in m³;
C_prepresents the specific heat of the air at constant pressure expressed in kJ/kg;
θ_intrepresents the internal temperature expressed in K;
“θ_c” represents the setpoint temperature in K.
The quantity of heat Q_m,aflikely to be absorbed by the cold air stream 58 is calculated according to the following equation “EQ4”:
Q_m,af=μ·ρ_af ·q _m,e ·h _af ·t “EQ4”:
in which μ represents the efficiency of the compressed air source;
ρ_afrepresents the density of the cold air leaving the Hilsch-Ranque vortex tube 24 expressed in kg/m³;
q_m,erepresents the mass flow of cold air expressed in kg/s;
h_afrepresents the quantity of heat likely to be absorbed by a kilogram of cold air leaving the Hilsch-Ranque vortex tube 24 expressed in fg/kg;
t represents the time expressed in seconds.
From balance equation “EQ1”, it is possible to find the duration “t” of a compressed air injection pulse for the inside temperature “θ_int” to be equal to the setpoint temperature “θ_c” according to the following equation “EQ5”:
$\begin{matrix} t = \frac{ρ_{int} \cdot V \cdot C_{p} \cdot (θ_{int} - θ_{int}^{c})}{μ \cdot ρ_{af} \cdot q_{m, e} \cdot h_{af} - K \cdot S_{T} \cdot (θ_{ext} - θ_{int}^{c})} & “ EQ 5 ” \end{matrix}$
It will be observed that, to be able to calculate the duration “t” of the pulse, in addition to the constants that are established beforehand according to the physical properties of the air or the specifications of the compressed air source, it is necessary to know the parameter values that are likely to change during the method. These parameters are the external temperature “θ_ext”, the inside temperature “θ_int” and the setpoint temperature “θ_c”.
The setpoint temperature “θ_c” can be predefined or indeed set by the user for example by means of an appropriate interface for entering data into the electronic control unit 28.
The inside “θ_int” and outside “θ_ext” temperatures are measured by at least two thermal probes 78 that are arranged respectively inside and outside the refrigerating chamber 12. Each thermal probe 78 comprises means for transmitting a signal representative of the measured temperature to the electronic control unit 28.
The table below represents the pulse durations “t” in seconds of the cooling device 10 controlled according to the inventive method according to the external temperature “θ_ext” and the internal temperature “θ_int” to achieve a setpoint temperature “θ_c” of −25° C. for a refrigerating chamber 12 with a volume of 12 m³and made of a highly insulating material having a general thermal transmission coefficient “K” less than 0.35 kcal/m².K.


	θext

Θint	25	26	28	30	32	34	35	36	38	40

−25	0	0	0	0	0	0	0	0	0	0
−24	3	3	3	3	3	3	3	3	3	3
−23	5	5	5	5	5	5	5	5	5	5
−22	8	8	8	8	8	8	8	8	8	8
−21	10	10	10	10	10	10	11	11	11	11
−20	13	13	13	13	13	13	13	13	13	13
−19	15	15	15	15	16	16	16	16	16	16
−18	18	18	18	18	18	18	18	18	18	18
−17	20	20	20	21	21	21	21	21	21	21
−16	23	23	23	23	23	23	23	23	23	23
−15	25	25	25	25	26	26	26	26	26	26
−14	28	28	28	28	28	28	28	28	28	28
−13	30	30	30	30	30	31	31	31	31	31
−12	32	32	33	33	33	33	33	33	33	33
−11	35	35	35	35	35	35	35	35	36	36
−10	37	37	37	37	38	38	38	38	38	38
−9	39	39	40	40	40	40	40	40	40	41
−8	42	42	42	42	42	42	43	43	43	43
−7	44	44	44	44	45	45	45	45	45	45
−6	46	46	47	47	47	47	47	47	47	48

The method of controlling the refrigerating cooling device 10 is represented in FIG. 3. When the method is running, all the control and comparison actions are performed by the electronic control unit 28.
On the initialization “E0” of the method, the setpoint temperature “θ_c” is given as a parameter of the electronic control unit 28.
In a first measurement step “E1”, the measurements of the internal temperature “θ_int”, of the external temperature “θ_ext”, of the differential pressure “ΔP” and of the humidity ratio “TH” are transmitted to the electronic control unit 28.
Then, in a second comparison step “E2”, the internal temperature “θ_int” is compared with the setpoint temperature “θ_c”.
If the internal temperature “θ_int” is less than the setpoint temperature “θ_c”, the internal temperature “θ_int” is compared to an alarm temperature “θ_al” above which the cold subsystem risks being broken.
If the alarm temperature “θ_al” is exceeded, an alarm is triggered.
If the internal temperature “θ_int” is between the setpoint temperature “θ_c” and the alarm temperature “θ_al”, a third step for controlling the injection pressure “E3” is triggered during which the Hilsch-Ranque vortex tubes 24 are supplied with compressed air by the air compressor 16.
The duration “t” of the injected compressed air pulse is calculated by the electronic control unit 28 as explained previously in such a way that the internal temperature “θ_int” once again becomes equal to the setpoint temperature “θ_c”.
When the duration “t” of the pulse is exceeded, the supply valve 26 is controlled to its total closure position. Thus, the Hilsch-Ranque vortex tubes 24 are no longer supplied with compressed air.
Then, the method returns to the first measurement step “E1”.
From the second comparison step “E2”, when the internal temperature “θ_int” is less than or equal to the setpoint temperature “θ_c”, the method triggers a fourth step “E4” for checking the pressure that is triggered when the differential pressure “ΔP” between inside and the outside of the chamber 12 exceeds the set overpressure threshold. During this step, the solenoid valve 74 is controlled in such a way that the differential pressure “ΔP” is equal to the safety threshold.
When the differential pressure “ΔP” is less than the overpressure threshold, and the humidity ratio “TH” inside the chamber 12 is greater than an icing threshold, a fifth step “E5” for regeneration of the air driers 60A, 60B is triggered. During this step, the tap 64, discharge 68A, 68B and regulator 66A, 66B valves are controlled in such a way as to regenerate one and then the other of the air driers 60A, 60B.
The method implemented according to the teachings of the invention makes it possible to very effectively cool a refrigerating chamber 12 through the intermediary of Hilsch-Ranque vortex tubes 24 by acting solely on the compressed air injection pressure “P_inj”.
This is particularly advantageous because the cooling method does not entail acting individually on the tapered relief valve 48 on each of the Hilsch-Ranque vortex tubes 24, but by acting in a centralized manner on the compressed air source which is common to all the Hilsch-Ranque vortex tubes 24. Thus, the cooling device 10 is less costly to manufacture and is easy to control.
According to a second embodiment of the invention, a similar method can be applied to an air conditioning device equipped with Hilsch-Ranque vortex tubes 24.
FIG. 4 represents an air conditioning device 80 which is intended to cool a sealed chamber 12. The chamber 12 is in this case formed by the passenger compartment of a motor vehicle, such as a bus, in which the air conditioning device 80 is installed.
According to a variant that is not represented of the invention, the air conditioning device is designed in such a way as to be able to be installed in a lift cabin in order to be able to air-condition its interior.
According to another variant that is not represented of the invention, the air conditioning device is also adapted for immobile applications, such as the air conditioning of rooms of a building.
The chamber 12 of the vehicle is sealed by four vertical walls 14, by a bottom wall (not represented) and by a top wall (not represented).
As for the first embodiment, the air conditioning device 80 mainly comprises a compressed air source which supplies, through the intermediary of a supply circuit 32A, 32B, a plurality of Hilsch-Ranque vortex tubes 24. An exhaust duct 59 routes the hot air stream 50 expelled by the Hilsch-Ranque vortex tubes 24 to an exhaust orifice 61 which discharges outside the chamber 12.
The compressed air source is in this case formed by an air compressor 16 which is driven by an autonomous electric motor (not represented). The electric motor is, for example, supplied by an electricity accumulator which is regularly recharged by an alternator driven by the heat engine of the motor vehicle.
According to an unrepresented variant of the invention, the air compressor is driven by the heat engine of the motor vehicle through the intermediary of a hydraulic pump and a hydraulic motor.
The air is sucked by the air compressor 16 outside the chamber 12 via a suction duct 18.
Advantageously, the air compressor 16 is selected in such a way as to ensure the renewal of the air of the passenger compartment according to the maximum number of people that the motor vehicle is likely to transport simultaneously. In practice, a passenger enclosed in the chamber 12 consumes an air flow rate that is, for example, approximately 4 m³/h. This flow rate has to be multiplied by the maximum number of people that the vehicle can transport simultaneously, for example 100 people. The air available in the chamber 12 depends on the volume of the chamber.
To avoid suffocation, the air must be renewed according to a renewal rate “τ_r” calculated according to the following equation “EQ6”:
$\begin{matrix} τ_{r} = \frac{q_{vs}}{V_{u}} & “ EQ 6 ” \end{matrix}$
in which “q_vs” represents the air flow rate expired by the maximum number of passengers that the passenger compartment of the vehicle is likely to contain simultaneously, expressed in m³/h;
V_urepresents the volume of the passenger compartment expressed in m³.
From this calculation, the selected air compressor 16 is, for example, likely to output 0.84 m³/h to ensure the renewal of the air.
Concerning an air conditioning device 80, the objective is in this case to cool the internal temperature “θ_int” of the chamber 12 by a few degrees relative to the external temperature “θ_ext”, in particular when the external temperature “θ_ext” is considered to be hot, for example above 25° C. For example, the air conditioning device 80 is designed for the internal temperature “θ_int” to be 6° C. less than the external temperature “θ_ext”.
Advantageously, the cold air stream is blown at the height of the head of an individual of average size, considering the population that is likely to be present inside the chamber. Thus, the heads of the individuals are cooled as a priority, because that is where the hypothalamus, which is the human body's thermal regulator, is located. This is a principle that we call “Human Occipital Cooling” (abbreviated HOC).
To be able to know the internal temperature “θ_int”, a thermal probe 78 is arranged inside the chamber 12.
This objective is reached by maintaining the outlet temperature “θ_SF” of the cold air stream 58 leaving the Hilsch-Ranque vortex tubes 24 as close as possible to the dew point, which is in this case 0° C., without this outlet temperature “θ_SF” of the cold air stream 58 being less than the dew point.
The temperature of the hot air stream 50 is then, for example, equal to 120° C.
Since the outlet temperature “θ_SF” of the cold air stream 58 blown through the cold outlet orifice 56 of the Hilsch-Ranque vortex tubes 24 is greater than the dew point of the air in normal atmospheric conditions, the device does not include an air drier 60A, 60B, and it includes only a single supply circuit 32.
The air conditioning device 80 is controlled according to a control method in which, in a manner similar to that described in the first embodiment, the outlet temperature “θ_SF” of the cold air stream 58 is controlled by acting only on the injection pressure “P_inj” of the air in the Hilsch-Ranque vortex tube 24 according to a predetermined control law.
However, unlike the first embodiment, the compressed air is in this case injected continuously and not by pulses.
Furthermore, the outlet temperature “θ_SF” of the cold air stream 58 is automatically regulated by the electronic control unit 28 by varying the injection pressure “P_inj” of the compressed air so that the outlet temperature “θ_SF” is always greater than or equal to a minimum temperature “θ_min”, for example 0° C., to avoid condensation of the humidity present in the cold air stream at the outlet of the Hilsch-Ranque vortex tube. To this end, the air conditioning device 80 includes a pneumatic regulator-expansion valve 82 which is inserted in the supply circuit 32 to adjust the injection pressure “P_inj” of the compressed air. The regulator-expansion valve 82 is controlled by the electronic control unit 28.
It will be recalled that the parameters that influence the outlet temperature “θ_SF” of the cold air stream 58 are as follows:
the setting of the tapered relief valve 48 which determines the fraction “FF” of air reflected towards the outlet of the Hilsch-Ranque vortex tube 24;
the injection temperature “θ_inj” of the compressed air;
the injection pressure “P_inj” of the compressed air.
In the inventive control method, the tapered relief valve 48 is preset so that the fraction “FF” of reflected air remains constant throughout the method. For an air conditioning device 80, this fraction “FF” of reflected air is, for example, equal to 70%.
The injection temperature “θ_inj” of the air is generally equal to the external temperature “θ_ext” of the air when it is sucked into the air compressor 16 to which must be added a constant which is, for example, equal to 10° C. or 15° C. according to the type of air compressor 16 used. To be able to know the injection temperature, the air conditioning device 80 therefore includes a temperature probe 78 which can transmit to the electronic control unit 28 a signal representative of the measured external temperature “θ_ext”, from which it is possible to know the injection temperature “θ_inj”.
The maximum injection pressure “P_max” at which the air can be injected depends on the selected air compressor 16 as indicated previously. The maximum injection pressure “P_max” is for example, equal to 8 bar.
In the method implemented according to the teachings of the invention, the air compressor 16 permanently compresses the air at the maximum pressure “P_max”, then, the injection pressure “P_inj” is regulated by controlling the regulator-expansion valve 82.
Thus, the injection pressure “P_inj” of the air can be controlled in an injection pressure range between 1 and 8 bar. Bearing in mind that the temperature drop “ΔT” between the injection temperature “θ_inj” and the outlet temperature “θ_SF” of the cold air stream 58 is inversely proportional to the pressure “P_inj” of the injected compressed air, the limitation of the injection pressure “P_inj” to 8 bar means ipso facto that the temperature drop “ΔT” will also be limited. The maximum temperature drop is, for example, 41° C.
The fraction “FF” of reflected air being constant, it is possible to deduce the injection pressure “P_inj” of the air by using the following equation “EQ7”:
ΔT=−0.0397·(P _inj)⁴+0.8377·(P _inj)³−6.5497·(P _inj)²+24.912·(P _inj)−5.3973 “EQ7”:
in which “ΔT” represents the temperature drop between the injection temperature “θ_inj” and the cold outlet temperature “θ_SF”; and “P_inj” represents the injection pressure of the compressed air.
This equation “EQ7” is here obtained by interpolation, for example by the least squares method, based on a table of values supplied by the manufacturer of the Hilsch-Ranque vortex tubes 24. It is in this case a fourth degree polynomial.
This equation “EQ7” is a correct approximation for an injection temperature “θ_inj” equal to a reference temperature “θ_ref” which is in this case equal to 21° C. When the injection temperature “θ_inj” differs from this reference temperature “θ_ref”, it is possible to multiply the measured temperature drop “ΔT” by a correction factor which is equal to the injection temperature “θ_inj” divided by the reference temperature “θ_ref”.
Such an approximation is sufficient to implement the air conditioning function of the air conditioning device 80 while retaining sufficient precision for the outlet temperature “θ_SF” of the cold air stream 58 not to fall below the minimum temperature “θ_min” of 0° C.
The control method of the air conditioning device 80 is now described.
In a first measurement step “C1” the external temperature “θ_ext” and the internal temperature “θ_int” are measured by the thermal probes 78 and transmitted to the electronic control unit 28.
Then, a second step “C2” for calculating the outlet temperature “θ_SF” of the cold air stream 58 is triggered when the difference between the external temperature “θ_ext” and the internal temperature “θ_int” is less than a comfort value which is, for example, 7° C. During this step, the outlet temperature “θ_SF” is calculated by subtracting a predetermined constant value from a measurement of the injection temperature “θ_inj” of the compressed air.
The predetermined constant value is defined according to the characteristics of the selected air compressor 16, and notably according to the maximum injection pressure “P_max” at which the air can be compressed. This constant value is more particularly equal to the maximum temperature drop “ΔT” that it is possible to obtain with the air compressor 16 and which is, for example, equal to 41° C. In other words, the outlet temperature “θ_SF” of the cold air stream 58 cannot be more than 41° C. less than the injection temperature “θ_inj” of the air, this temperature drop “ΔT” being obtained for the maximum injection pressure “P_max”.
Then, a subsequent third step “C3” for correcting the outlet temperature “θ_SF” of the cold air stream 58 calculated during the second calculation step “C2” is triggered when said outlet temperature “θ_SF” is less than the minimum temperature “θ_min” of 0° C. The outlet temperature “θ_SF” is corrected so as to be greater than or equal to said minimum temperature “θ_{min” of}0° C.
The minimum temperature “θ_min” is in this case set at 0° C. It can of course change according to the atmospheric conditions in which the motor vehicle is required to operate.
According to the result of this last step “C3”, the temperature drop “ΔT” between the injection temperature “θ_inj” and the desired outlet temperature “θ_SF” of the cold air stream 58 is known.
The injection pressure “P_inj” of the compressed air is then calculated by the resolution of the interpolation equation “EQ7” in a fourth control step “C4”. When this equation “EQ7” allows a number of injection pressures “P_inj” as a solution, the highest injection pressure “P_inj” that is within the pressure range of the air compressor 16 is retained by the electronic control unit 28.
Then, the electronic control unit 28 drives the regulator-expansion valve 82 so that the injection pressure “P_inj” of the compressed air is effectively equal to the calculated injection pressure.
Then, the method is repeated, for example, at the end of a time delay which is, for example, equal to 60 seconds.
Thanks to the method implemented according to the teachings of the invention, it is therefore possible to control in a centralized way a plurality of Hilsch-Ranque vortex tubes by acting only on the injection pressure “P_inj”. Such a method is less costly and simple to implement.
According to a third embodiment of the invention that is not represented, the devices explained in the initial embodiments of the invention can also be used as heating devices by routing the hot air stream 50 expelled from the Hilsch-Ranque vortex tube 24 to the place or the object to be heated.
For example, the exhaust duct 59 of the air conditioning device 80 includes an orifice opening out inside the chamber 12. The orifice is blocked off by a controlled valve. When it is necessary to heat the chamber 12, the valve is then controlled to open.
The temperature of the hot air stream 50 can equally be calculated according to the injection pressure “P_inj” of the compressed air and the injection temperature “θ_inj” of the compressed air. Thus, it is possible to control the temperature of the hot air stream 50 by acting only on the injection pressure “P_inj” of the air through the intermediary of the electronic control unit 28.
It will be understood that these embodiments are given by way of indication and that the control method is applicable to any device of the same type including Hilsch-Ranque vortex tubes that is used to cool or heat a chamber or any element.

Claims

1. Method of controlling a device for air conditioning (80) or cooling by refrigeration (10) or heating the interior of a sealed chamber (12), the device (10, 80) comprising at least one compressed air source (16, 30) which supplies at least one Hilsch-Ranque tube (24), called “vortex” tube, with compressed air at an injection pressure (P_inj), the Hilsch-Ranque vortex tube (24) comprising:

at least one tangential orifice (40) for injecting compressed air into the Hilsch-Ranque vortex tube (24) which is arranged close to a first end (36) of the Hilsch-Ranque vortex tube, the injected air forming a first incoming stream of swirling air (44) towards a second end (38) of the Hilsch-Ranque vortex tube;

a tapered relief valve (48) which partially blocks off a first expulsion orifice (46) of the second end (38) of the Hilsch-Ranque vortex tube so that a first fraction (FC) of the incoming hot air stream (44) is expelled outside the chamber (12) while a second fraction (FF) of the air stream is reflected towards the first end (36) of the Hilsch-Ranque vortex tube forming a second concentric swirling air stream (52) inside the first swirling stream (44), the reflected air stream (52) being cooled by heat exchange with the incoming air stream (44);

a “cold” outlet orifice (56) for the reflected air (52) which is arranged at the first end (36) of the Hilsch-Ranque vortex tube so as to allow the second fraction (FF) of the cold air stream (52) to leave inside the chamber (12);

characterized in that the tapered relief valve (48) is preset so that the first (FC) and second (FF) fractions of air are constant while the method is running and in that it comprises a step (E3, C4) for controlling the compressed air injection pressure (P_inj).

2. Control method according to claim 1, characterized in that the outlet temperature (θ_SF) of the cold air stream is controlled by acting only on the injection pressure (P_inj) of the air into the Hilsch-Ranque vortex tube (24) according to a predetermined control law (EQ7).

3. Control method according to claim 1, characterized in that it comprises a step (C2) for calculating the outlet temperature (θ_SF) of the cold air stream prior to the step for controlling the injection pressure (C4) during which said outlet temperature (θ_SF) is calculated by subtracting a predetermined constant value from the compressed air injection temperature (θ_inj),

and in that it comprises a step for correcting (C3) the calculated cold air stream outlet temperature (θ_SF), which is triggered when said outlet temperature (θ_SF) during the preliminary calculation step (C2) is less than a minimum temperature (θ_min) and during which the outlet temperature (θ_SF) is corrected so as to be greater than or equal to said minimum temperature (θ_min).

4. Control method according to claim 3, characterized in that the compressed air source (16) is an air compressor which sucks in ambient air from outside the chamber (12), and in that the injection temperature (θ_inj) is proportional to the external temperature (θ_ext) of the chamber (12).

5. Control method according to claim 4, characterized in that the chamber (12) is a passenger compartment of a motor vehicle in which the air conditioning device (80) is installed and in that the air compressor (16) is driven by the heat engine of the motor vehicle through the intermediary of a hydraulic pump and a hydraulic motor.

6. Control method according to claim 2, characterized in that the injection pressure (P_inj) is controlled by pulses at an injection pressure (P_inj) which is predetermined, the duration (t) of each pulse being determined in such a way that the chamber (12) is maintained at a setpoint temperature (θ_c).

7. Method according to claim 6, characterized in that the duration (t) of each pulse is determined as a function of the ambient temperature inside the chamber (θ_int), of the injection temperature of compressed air into the Hilsch-Ranque vortex tube (θ_inj), and of the setpoint temperature (θ_c).

8. Control method according to claim 7, characterized in that the duration (t) of each pulse is determined by taking into account the balance (EQ1) between:

the sum of the heat losses (Q_dep) through the walls of the chamber (12) per time unit and the quantity of heat to be removed (Q_ref) to cool the air inside the chamber (12) to the setpoint temperature (θ_c), and

the quantity of heat (Q_m,af) likely to be absorbed by the cold air leaving each Hilsch-Ranque vortex tube (24) for said time unit.

9. Method according to claim 7, characterized in that the air is dried by drying means (60A, 60B) before its injection into each Hilsch-Ranque vortex tube (24) so that its dew point is less than the air outlet temperature (θ_SF).

10. Device (10, 80) for implementing the method according to claim 1, characterized in that it comprises a plurality of Hilsch-Ranque vortex tubes (24) which are fed in parallel by at least one common compressed air source (16, 30) and in that each Hilsch-Ranque vortex tube (24) includes a tapered relief valve (48) that can be adjusted only manually.

11. Method according to claim 8, characterized in that the air is dried by drying means (60A, 60B) before its injection into each Hilsch-Ranque vortex tube (24) so that its dew point is less than the air outlet temperature (θ_SF).