WO2012123914A1

WO2012123914A1 - Device for treating humid air and associated method

Info

Publication number: WO2012123914A1
Application number: PCT/IB2012/051242
Authority: WO
Inventors: Pierre Brun
Original assignee: Pierre Brun
Priority date: 2011-03-16
Filing date: 2012-03-15
Publication date: 2012-09-20
Also published as: FR2972787A1; FR2972787B1

Abstract

The present invention relates to a treatment device (1) for treating hot and humid air from at least one drying installation, notably a dryer (10), comprising: - an inlet to receive the air for treating coming from the outlet (3) of the drying installation, - an air/air exchanger (6) through which the air for treating circulates - at least one air/fluid exchanger (7a, 7b) for dehumidifying the air for treating, the air/air exchanger (6) and said at least one air/fluid exchanger (7a, 7b) being placed in series in such a way as to allow air from said at least one air/fluid exchanger (7a, 7b) and/or air from outside to be heated up using the air for treating, - at least one outlet for air after treatment connected to the inlet (2) of the drying installation, - at least one bypass (15, 16, 22) bypassing said at least one air/fluid exchanger (7a, 7b).

Description

Wet air treatment device and associated method

The present invention relates to the treatment of moist air. The invention applies for example to the treatment of air from electric dryers, steam or gas.

In known manner, clothes dryers use a hot air flow that moistens on contact with wet laundry. Evacuation of hot, humid air can be problematic in the absence of a dedicated exhaust stack.

Dryers are responsible for the highest energy consumption in a laundromat, with over 60% of total energy consumption. They consume a lot of energy in order to heat the air and much of this energy is lost in the hot and humid air released to the outside. It is therefore desirable to reduce the energy consumption of the dryers.

In addition, regulatory constraints and the implementation of self-service laundromats in urban areas make it difficult to remove hot, humid air to the outside.

It is known, particularly from application DE 43 06 215, to associate with an electric dryer an exchanger for cooling and dehumidifying the hot and humid air from the dryer.

Moreover, the hot and humid air of the dryer is loaded with textile fibers from the laundry, which can lead to maintenance operations of any facility receiving this air to remove the fibers that have accumulated.

There is a need to treat the air drying plants, including existing dryers, to reduce energy consumption and / or simplify their installation and use conditions.

The present invention aims in particular to meet this need.

The invention thus has, according to one of its aspects, a device for treating hot and humid air coming from at least one drying installation, in particular a dryer, comprising:

an inlet for receiving the air to be treated coming from the outlet of the drying installation,

an air / air exchanger in which circulates the air to be treated, at least one air / fluid exchanger, in particular an air / fluid exchanger, in particular an air / water exchanger, for dehumidifying the air to be treated, the air / air exchanger and said at least one air / fluid exchanger being arranged in series so as to allow the air to be treated to heat air from said at least one air / fluid exchanger and / or air coming from the outside,

at least one air outlet after treatment connected to the inlet of the drying installation,

at least one bypass of said at least one air / fluid exchanger.

Said at least one bypass may be a first bypass connecting the outlet of the drying installation to the inlet of the drying installation and / or a second bypass connecting the outlet of the air / air exchanger to the inlet of the dryer. the drying installation and / or a third bypass allowing recirculation of the air to be treated leaving the air / air heat exchanger therein again before returning to the entrance of the drying installation.

Thanks to the invention energy saving can be achieved due to a heat recovery of the hot and humid air from the drying installation to heat air that can be sent into the installation drying.

On the other hand, the liquid heated in an air / fluid exchanger can be recovered, especially when it comes to water, for example washing clothes. The recovered liquid can also be stored before being reintroduced into the air / fluid exchanger, thereby saving fluid, for example water. Alternatively, the heated liquid is discharged without being intended for a specific subsequent use.

In addition, the invention can allow a reduction in the installed electrical power and a suppression of the exhaust system hot and humid output through a closed circuit operation.

"Bypass" means any system for driving the air to be treated from a given air outlet to a given air inlet.

The presence of a first bypass and / or a second bypass and / or a third bypass can make it possible to avoid the passage of the air to be treated in the at least one air / fluid exchanger, and possibly in the air / air exchanger when the first bypass is used.

The first bypass and / or the second bypass and / or the third bypass can be used, in particular during the start of the drying installation, by example during a first drying cycle, especially during a rise in temperature in the drying installation. Indeed, when the temperature of the air to be treated leaving the drying installation is not yet very high, the use of an air / fluid exchanger causes significant undesirable cooling of the air at this stage. because it returns to the drying installation and causes a decrease in temperature in it. The use of the first bypass and / or the second bypass and / or the third bypass can thus make it possible to reduce the energy losses and the additional consumption cost for heating the air in the drying installation, in particular at the beginning of the cycle, during a temperature rise phase.

The passage of the air to be treated in said at least one air / fluid exchanger can be controlled by means of the first bypass and / or the second bypass and / or the third bypass. The opening and / or closing of the first bypass and / or the second bypass and / or the third bypass can be controlled as a function of at least one control parameter. In particular, the passage of the air to be treated in said at least one air / fluid exchanger may be authorized, for example by closing the first bypass and / or the second bypass and / or the third bypass, when at least one value predetermined value of said at least one control parameter is reached.

The control parameter may for example be a temperature, a humidity and / or a time, in particular the temperature in the dryer, the moisture content in the dryer and / or a dryer operating time.

The circulation of the air to be treated in said at least one air / fluid exchanger may, for example, be authorized when the temperature is above 50 ° C. and / or when the humidity level is close to 100%.

The treatment device may comprise at least two air / fluid exchangers, advantageously placed in series, or at least one air / fluid exchanger with at least two stages. An air / fluid exchanger with at least two stages may comprise at least two different air inlets and two different air outlets.

Advantageously, the air to be treated can circulate in a single air / fluid exchanger or in a single stage of an air / fluid exchanger with at least two stages to allow faster dehumidification of the air to be treated circulating in the exchanger. . Indeed, when the temperature of the air to be treated entering said at least one air / fluid exchanger is too high, it may be advantageous to increase the circulation velocity of the liquid of cooling in said at least one air / fluid exchanger to improve the removal of moisture from the treated air. The use of a single air / fluid exchanger or a single stage of an air / fluid exchanger at least two stages can allow the coolant to circulate faster and thus facilitate cooling.

The operation of said at least one air / fluid exchanger with a single air / fluid exchanger and / or a single stage of an air / fluid exchanger with at least two stages can be regulated as a function, for example, of an operating time of the air / fluid exchanger. drying installation and / or a humidity level in the drying installation, in particular the dryer, and possibly depending on the temperature in the drying installation.

The use of a single air / fluid exchanger or a single stage of an air / fluid exchanger with at least two stages can be particularly adapted during a drying cycle of the drying installation, in particular when the temperature of the air to be treated is the highest.

The use of a single air / fluid exchanger or a single stage of an air / fluid exchanger at least two stages can be accompanied by a stop operation of the heater of the drying installation in order to decrease the temperature of the air entering the dryer and thereby reduce the energy consumption of the drying installation.

The device may comprise a fourth bypass connecting the outlet of the air / fluid exchanger to the inlet of the drying installation. The use of the fourth bypass can be particularly useful at the end of the drying cycle of the drying installation, especially when the temperature of the air to be treated is high. In fact, the fourth bypass can make it possible to divert the hot air to be treated leaving said at least one air / fluid exchanger towards the drying installation without this being still being heated by passing through the air / air exchanger. In this way, it is possible to avoid introducing air at a temperature that is too high in the drying installation.

The device may comprise a safety valve allowing the evacuation of hot air to the outside. The valve can open when the temperature of the air to be treated reaches a certain temperature threshold, for example a temperature above 80 ° C.

The device may comprise a liquid circuit for cooling said at least one air / fluid exchanger. The liquid circuit can be equipped with a regulating valve, in particular a three-way valve, to vary the quantity of liquid brought into the circuit of liquid to regulate the temperature of said at least one air / fluid exchanger. The control valve can for example be connected to a city water circuit. The control valve can be used to regulate the temperature of the at least one air / fluid exchanger by bringing more or less liquid therein. The temperature of the at least one air / fluid exchanger can be regulated between 5 and 35 ° C, or between 5 and 30 ° C, preferably between 10 and 28 ° C, or at a temperature of the order of 35 ° C. Such a temperature range can achieve a significant energy gain of the treatment device according to the invention.

The air / fluid exchanger may comprise a plurality of fluid inlets and a plurality of fluid outlets. Thus, the path of the fluid in the exchanger may be shorter, so that the fluid is heated only moderately.

The air / air exchanger may comprise at least one thermally conductive plate separating the flows of air to be treated from the inlet and air to be heated to the exit.

Heated and condensed water circulating in said at least one air / fluid exchanger can be collected in a water reserve so as to be able to be reused later, for example for washing clothes.

Water from the water supply can be reintroduced into the air / fluid heat exchanger. Water can circulate in closed circuit. Water can circulate several times in the air / fluid heat exchanger.

The three-way valve can allow the supply of water from the reserve, as well as drinking water from the city water circuit in case the water of the reserve is too hot. In the invention, it is possible to use only a small amount of tap water. We mainly use the water of the reserve, circulating in closed circuit.

The device may comprise a filtration system for the air to be treated, which may comprise, for example, at least one grid supporting a filtering membrane, for example an open cell foam.

The filtration system may be provided with an alarm, including sound and / or light, informing about the efficiency of the filtration system. In particular, the alarm can be used to determine when it is necessary to change the filter of the filtration system. The filtration system may comprise at least one drawer allowing the removal of at least one filter and its cleaning.

The filtration system may also include a system for cleaning the liquid injection filtration system, in particular water, in order to drive the fibers retained in the filtration system towards an evacuation.

The device may comprise an outer casing, inside which the exchangers are arranged. This can contribute to the aesthetics of the device, especially in case of installation in a laundromat or laundry, for example.

According to another of its aspects, a subject of the invention is a method of regulating the operation of a treatment device as defined above, in which the operation of said at least one air / fluid exchanger is regulated as a function of at least one regulation parameter.

In particular, the method comprises the step of allowing the passage or not of the air to be treated in said at least one air / fluid exchanger according to at least one control parameter.

The method may comprise the following successive steps:

diverting the air to be treated from the outlet of the drying installation to the inlet of the drying installation via said at least one bypass, in particular the first bypass and / or the second bypass and / or the third bypass, until a predetermined value of said at least one regulation parameter is reached, allow the passage of the air to be treated in said at least one air / fluid exchanger when the predetermined value of said at least one regulation parameter is reached.

Said at least one control parameter can be a temperature and / or a humidity level and / or a time, in particular the temperature in the dryer and / or the humidity level in the dryer and / or an operating time of the dryer. dryer.

When the treatment device comprises at least two air / fluid exchangers or an air / fluid exchanger with at least two stages, the method may comprise the step consisting in directing the air to be treated in a single air / fluid exchanger or in a single stage of a heat exchanger with at least two stages so as to increase the cooling efficiency of the air to be treated. The temperature of said at least one air / fluid exchanger can be regulated between 5 and 35 °, or between 5 and 30 ° C, preferably between 10 and 28 ° C using the liquid circuit, for example at a value of about 23 ° C.

When the processing device comprises a fourth bypass connecting the output of the at least one air / fluid exchanger to the inlet of the drying installation, the method may comprise the step of diverting the air to be treated from the outlet of said at least one air / fluid exchanger to the inlet of the drying installation so as to avoid a heating of the air to be treated in the air / air exchanger.

The method may comprise the heat insulation of the treatment device and / or the drying installation, in particular the dryer. Indeed, it is possible to very significantly reduce the power consumption of a dryer only by effectively insulating it. The gain can go up to 30%.

The invention also relates, independently or in combination with the foregoing, to an installation comprising a treatment device as defined above and at least one drying installation, in particular a dryer. Several drying plants, including dryers, may be associated, where appropriate with a single treatment device.

The drying facility (s) may be electric, steam or gas.

The installation may comprise at least one washing machine whose water supply is at least partially provided by water having circulated in said at least one air / fluid exchanger of the treatment device.

The invention will be better understood on reading the following detailed description of nonlimiting exemplary embodiments and on examining the appended drawing, in which:

FIG. 1 schematically and partially illustrates a dryer according to the prior art,

FIG. 2 schematically and partially shows an example of an installation comprising a processing device produced in accordance with the invention; FIGS. 2a to 2d illustrate, in a schematic and partial manner, parts of the processing device of FIG. 1

FIG. 3 represents the evolution of the energy gain as a function of the temperature at the outlet of the air / air heat exchanger, FIG. 4 represents the evolution of the power exchanged in the air / air exchanger as a function of the temperature at the outlet of the air / air exchanger,

FIG. 5 represents the evolution of the energy gain as a function of the temperature at the outlet of the air / fluid exchanger, and

FIG. 6 represents the evolution of the relative humidity at the inlet of the dryer drum as a function of the temperature at the outlet of the air / fluid exchanger.

FIG. 1 shows an example of a dryer 10 according to the prior art. The dryer 10 comprises a heater 5 provided with one or more electrical resistors and a drum 4 in which the laundry is placed. Alternatively, the dryer 10 may be steam or gas.

The ambient air passes through the inlet 2 of the heater 5 and is then injected at the outlet 8 of the heater 5 into the rotating drum 4 which contains the laundry to be dried.

The hot and humid air present at the outlet 3 of the drum 4 is then rejected to the outside.

The outward discharge of the hot and humid air at the outlet 3 of the drum 4 gives rise to several disadvantages. In particular, the energy consumption of the heater 5 for heating the ambient air is high and most of this energy is lost in the hot and humid air discharged to the outside environment. In addition, the current regulatory constraints and the implementation of self-service laundromats in urban areas do not allow easy evacuation of hot, humid air to the outside.

FIG. 2 shows a drying installation according to the invention, comprising an air treatment device 1 coming from a dryer 10. Although this is not shown, the processing device 1 can also process air from several dryers.

The dryer 10 may be according to a dryer according to the prior art, for example as described in FIG. 1. The dryer 10 comprises a heater 5, comprising one or more electrical resistors, for heating the ambient air coming from the dryer. inlet 2, and a drum 4 for drying the laundry, wherein the air heated by the heater 5 is injected through the inlet 8 of the drum 4.

The air from a single dryer 10 can be channeled to the device 1. Alternatively, the air flows from each of the dryers of a plurality of dryers can be combined before reaching the treatment device 1 or be joined at the input of the treatment device 1.

The treatment device 1 may also comprise several air inlets 2 for respective dryers.

The dryer 10 may be an electric dryer, a steam dryer or a gas dryer.

The hot and humid air leaving the dryer 10 may, depending on the nature of the dryer, be of variable composition, and may for example comprise gases from the combustion of the dryer heating gas.

The air discharged from the dryer 10 may for example have a temperature of the order of 60 to 70 ° C.

The processing device 1 further comprises a first bypass 15 connecting the outlet 3 of the dryer 10 to the inlet 2 of the heater 5, visible in FIG. 2a, a second bypass 16 connecting the outlet of the air / air heat exchanger 6 to the inlet 2 of the heater 5, visible in Figure 2b, and a fourth bypass 17 connecting the outlet 18 of the air / fluid exchangers 7a and 7b to the inlet 2 of the heater 5, visible in Figure 2c.

A third bypass 22 also allows a recirculation of the air to be treated leaving the air / air exchanger 6 through it again before being redirected to the inlet 2 of the heater 5, as shown in FIG. 2d. This third bypass 22 is preferably used when the dryer 10 is a steam dryer or a gas dryer.

The hot and humid air introduced into the treatment device 1 through the inlet 3 is led to the inlet of an air / air heat exchanger 6. The hot and humid air is thus cooled in the exchanger 6 and, optionally , some of its moisture is condensed.

The exchanger 6 comprises, for example, a plurality of thermally conductive plates separating the two air streams which exchange their calories circulating through the exchanger.

The air leaving the air / air exchanger 6, partially dehumidified, is then injected into two air / fluid exchangers 7a and 7b placed in series in which it cools and dehumidifies thanks to the circulation of a colder liquid, for example water, circulating in a water circuit 12. The water circuit 12 may for example consist of water from the city network and / or water from a water supply, for example a storage tank.

The water heated by the exchangers 7a and 7b may allow, if necessary, to feed one or more washing machines.

Advantageously, the dew point enabling the air to be dehumidified is largely reached even if the water flowing in the air / fluid exchangers 7a and 7b reaches a temperature of the order of 35 ° C., so that the water flowing through the water circuit may not be very cold.

The supply of cold water to cool the water flowing in the air / fluid exchangers 7a and 7b may not be very important and allow substantial water saving.

The water circuit 12 may be a closed circuit, the water being cooled for example by means of one or more radiators or any other heat exchanger.

Part of the water from the air / fluid exchangers 7a and 7b may or may not be recovered at a water outlet 9, for example in a storage tank, for example for use in one or more washing machines.

The cooled and dehumidified air leaving the air / fluid exchangers 7a and 7b through the outlet 13 and is directed towards the air / air heat exchanger 6 in which it heats up.

The temperature of at least one of the air / fluid exchangers 7a and 7b can be regulated to be, for example, between 10 and 28 ° C. by means of a three-way valve 21 installed on the water circuit 20, for example tap water, this valve 21 for bringing more or less water into the water circuit 20.

The dehumidified and heated air is then discharged through an air outlet 2 to be directed back to the dryer 10 to complete a new cycle.

An example of operation and regulation of the treatment device 1 according to the invention will now be described.

At the start of the dryer 10, the first bypass 15, visible in Figure 2a, and / or the second bypass 16, visible in Figure 2b, and / or the third bypass 22 especially in the case of a steam dryer 10 or gas, visible in Figure 2d, are in operation so as to divert the air to be treated from the outlet 3 of the dryer 10 to the inlet 2 of the heater 5. The air to be treated is thus diverted so as not to pass through the air / fluid exchangers 7a and 7b so as not to be cooled and thus to lose energy.

The operation of the first bypass 15 and / or the second bypass 16 and / or the third bypass 22 is interrupted when a predetermined value of a regulation parameter is reached. This may be, for example, a predetermined temperature in the dryer 10, a predetermined humidity level in the dryer 10 and / or an operating time of the predetermined dryer.

When the predetermined value of the regulation parameter is reached, the first bypass 15 and / or the second bypass 16 and / or the third bypass 22 stop working so that the air to be treated can pass through the air / fluid exchangers 7a and 7b .

The temperature of the air / fluid exchangers 7a and 7b is regulated to be for example between 10 and 28 ° C by means of the three-way valve 21 installed on the water circuit 20, this valve making it possible to bring more or less city water in the water circuit 20.

The air to be treated leaving the air / fluid exchangers 7a and 7b is reheated in the air / air exchanger 6 before returning to the dryer 10 via the inlet 2 of the heater 5.

At the end of the drying cycle, when the temperature in the dryer 10 is high, only one of the two air / fluid exchangers 7a and 7b remains in operation so as to allow a faster circulation of the water of the water circuit 12 and easier cooling of the air to be treated.

In addition, when the temperature of the air to be treated is too high, especially at the end of the drying cycle, it may be useless and dangerous to let it pass through the air / air heat exchanger 6 to be heated. In this way, the fourth bypass 17, visible in FIG. 2c, can make it possible to divert the air leaving the air / fluid exchangers 7a and 7b towards the inlet 2 of the heater 5 before entering the dryer 10.

The treatment device 1 may comprise a filtration system (not shown) of the air coming from the dryer in order to rid it of the textile fibers that may come from the laundry to be dried. The filtration system may comprise a plurality of filters including for example at least one grid, for example a fine grid, and at least one open-cell foam filter or other filter membrane. Such a filtration system is easy to maintain. The device may include one or more drawers for extracting the filter or filters for cleaning.

On the other hand, the filtration system may include a cleaning system comprising a liquid injection pipe including water, not shown, for cleaning the filters and to cause the textile fibers. The liquid or the cleaning water of the filter (s) and the condensed water during the dehumidification of the hot and humid air can be evacuated by a condensate drain located at the bottom of the device.

The filtration system may be equipped with an alarm, including sound and / or light, allowing a user to determine when the filter is no longer effective and must be changed.

Example

We will now describe an example of operation of a drying installation comprising a treatment device 1 according to the invention to determine the energy gain obtained in comparison with that of a dryer 10 according to the prior art.

The calculation of the energy gain was performed using a numerical simulation, carried out in static mode, that is to say assuming the operation of the plant in steady state and assuming that all the parameters (temperature, humidity, flow) are constant.

The simulation required access to different physicochemical properties of the fluids used. The details of the calculation of these properties are given below.

Molar masses (M in g.mol ¹ ): water: 18.00 g.mol- ¹ and air: 28.96 g.mol ^-1 Heat capacities (Cp in kJ.kg ^_1 .K ^_1 ): the heat capacities The mass values are considered as constant and their value taken as equal to their value at 30 ° C, liquid water: 4,1803 kJ.kg ^ .K ^"1 , water vapor: 1,8130 kJ.kg ^ .K ^{" 1} and air dry: 1.0070 kJ.kg -1 .K ^-1 .

Latent heat of vaporization (Lv in kJ.K ^"1 ): one considers the latent heat of vaporization of the water at 0 ° C, Lv _water = 2501 kJ.kg ^{" 1} . The choice of the temperature of 0 ° C determines the method of calculating the enthalpy of the water vapor contained in the moist air.

Saturating vapor pressure of water (P ° in Pa): the saturation vapor pressure of water is given by the following correlation: - Uy, y30D _? _?

Ln (P °) = - + 21, 2409642 - 2.711193 - 10 - T + 1.673952 - 10 - J ^z

T '

+ 2,433502 · Ln (T)

where T is the temperature in K.

Specific enthalpy (h in KJ.kg ^"1 ): the reference state for which the enthalpy is assumed to be zero is different for water and air For air, 0 ° C is taken and the condition gaseous, whereas for water, 0 ° C and the liquid state will be obtained, thus obtaining the enthalpies by the following relations:

Liquid water: h = Cp _{water | iq} - (T - 273 (2)

_A. ,, Cp Air dry '( ^" * ^{" ~} 273.15) + w · (h / _water + Cp _water · (T - 273.15))

Moist air: h = - (3)

1 + w where w is the absolute humidity of moist air expressed in kg of water vapor per kg of dry air. On the other hand, the specific enthalpy of moist air is reduced to 1 kg of humid air.

Determination of the air flow 11 at the inlet 11 of the air / fluid exchanger 7 and the stream 14 of condensed water at the outlet 14 of the air / air exchanger 6

We start by calculating the absolute humidity w ^sat (Tn) of saturated humid air at the temperature Tu, Tu being the temperature at the outlet 11 of the air / air exchanger 6. If the absolute humidity w ₃ of the air leaving the dryer 10 at the air outlet 3 is less than w ^sat (Tn), so there is no condensation in the air / air heat exchanger 6 and we therefore have the following results:

wi i = w ₃ (4) Qm "= Qm ₃ (5) Qm _flow i4 = 0 (6) If, however, w ^sat (Tn) <w ₃ , then part of the moisture contained in the air 3 exiting of the dryer 10 condenses in the air / air heat exchanger 6, and the air 11 leaving the exchanger 6 is saturated. We will then have:

Qm _n = Qm ₃ - ^l ^ L (8)

1 + w ₃

The main characteristics of the flow 11 being known, one can then calculate its enthalpy and its flow rate. It is the same for the stream 14 of condensed water.

Calculation of the heat flux exchanged in the air / air heat exchanger 6

The heat flux exchanged in the air / air heat exchanger 6 is deduced by a heat balance:

Φ ₆ = Qm, - h, - Qm _n - _u - Qm _fliaU - _flaU (10)

Determination of the air flow 13 entering the air / air exchanger 6 and the flow 9 of condensed water leaving the fluid air exchanger 7

The approach is identical to that followed previously. There are two cases. The first case is that for which wn <w ^sat (Ti ₃ ). There is no condensation in the air / fluid exchanger 7 and the following results are obtained:

wi ₃ = wn (11) Qm ₁₃ = Qm "(12)

Qm _{flux 9} = 0 (13) In the second case where wn> w ^sat (Ti ₃ ), the air leaves saturated air / fluid exchanger 7 and part of the water vapor condenses. We then have:

W ₁₃ = w ^sat (T ") (14) Qm _u = Qm _n - ^X ^ (15) l + w

Qm _flow

Since the main characteristics of the stream 13 are known, it is then possible to calculate its enthalpy and its volume flow rate. It's the same for stream 9.

Calculation of the heat flux exchanged in the fluid air exchanger 7

The heat flux exchanged in the air / fluid exchanger 7 is deduced by a thermal balance:

Φ _Ί = Qm _u - h _u - Qm _l , - _l , - Qm _flia9 - h _fla9 (17) Determination of the cooling water flow 12

A thermal balance on the cooling water 12 makes it possible to obtain the flow of cooling water 12 necessary since the temperature variation of this water is known. Qm _l2 = ^Φ (18)

Determination of the air flow 2 at the outlet of the air / air exchanger 6

When the air leaving the air / fluid exchanger 7 passes through the air / air heat exchanger 6, it can only get warmer. The water vapor can not condense and therefore the water content of the air does not change. So we have :

W ₂ = Wl3 (19)

Qm ₂ = Qm ₁₃ (20)

A heat balance makes it possible to determine the enthalpy of flow 2:

^ _{6 +} Qm _l3 . h _{l3 (21)} Qm ₂

From equation (3) giving the enthalpy of moist air as a function of its temperature and its absolute humidity, it is possible to determine T ₂ :

_{T2 =} h ₂ - (l + w ₂ ) - w ₂ - _water Lv _(2¾

^ P dry air ^ 2 ^ Steam water

We can then calculate the relative humidity and the flow rate of the flow 2.

Determination of the air flow 8 at the entrance of the drum 4

When the air passes through the heater 5, its temperature increases and so there can be no condensation. Therefore, the absolute humidity is conserved as well as the mass flow:

w ₈ = w ₂ (23)

When the hot air exiting the heater 5 passes through the wet laundry in the drum 4, it is charged moisture isenthalpe way. Therefore, we have:

h ₈ = h ₃ (25) We can then deduce the temperature of the air flow 8: It is then possible to calculate the volume flow and the relative humidity of the air flow 8. Determination of the electrical power required by the heater 5

A heat balance on the air in the heater 5 makes it possible to determine the electric power that the electrical resistances must supply:

(£ ₅ = Om ₈ · (/ ¾ - / ¾) (27)

Calculation of energy gain

The energy gain is defined as the relative difference expressed as a percentage between the power required to heat a flow of ambient air from room temperature to the temperature T ₈ , and the power supplied to the heater 5. It is chosen to consider that the volume flow of ambient air is equal to the volume flow rate of the air flow 3. The ambient air temperature is taken at 20 ° C and its relative humidity at 30%.

We begin by calculating the conventional power Φ required in the case of conventional operation without the treatment device 1 according to the invention:

classical = Q ™ ₃ ^■ (h ambient air (- h ambient air (^ ambient)) ( ²⁸ ) We can then calculate the gain:

Gain (%) = 100 · ° ^{5 ~} ^ ^d "(29)

Calculation of the energy gain for the example

The observation of experimental results made it possible to define a typical cycle of drying. The parameters of this cycle are as follows:

- air temperature at the heater outlet T ₈ = 70 ° C

- volume flow rate of the air leaving the drum Qv ₃ = 1200 m ^3. !! ^"1

relative humidity of the air leaving the drum ε ₃ = 45%

- temperature of the air leaving the air / air heat exchanger Tu = 35 ° C.

- temperature of the air leaving the air / water exchanger T ₁₃ = 25 ° C.

The following table 1 presents the results of the simulation for the cycle of this type.

Flux T ε w Qm Condensed water T Qm

° C% k§ ir umide / h ° C kg / h

3 46.5 45 0.00303 1210 14 - 0

11 35 82.7 0.00303 1210 9 25 ii; 7 13 25 100 0.00203 1199 T Qm

2 36.7 51.4 0.00203 1199 Cooling water 12 ° C kg / h

8 70 10.2 0.00203 1199 Entry 20

983

Power exchanged kW Output 30

Gain: 42.6 ⁰ / o

Air / air heat exchanger 6 3,97

Air / water exchanger 7 11.4

Heater 5 11.4

Table 1

An energy gain of 42.6% is obtained. The energy saving compared to conventional drying is therefore important, namely more than 40%. In addition, the electric power required for heating the air before returning to the drum 4 is only 11.4 kW, the power installed on the dryer 10 being 36 kW. It therefore appears possible to greatly reduce the installed electrical power required for the dryer 10.

It is also noted that the air returning to the drum 4 is dry since its relative humidity is 10.2% at 70 ° C. This figure can be compared with that of a conventional dryer. Thus, if an ambient air initially at 20 ° C. and 30% humidity is heated to 70 ° C., air is obtained at 70 ° C. and 2.6% humidity. With the device 1 according to the invention, the humidity remains very low and allows easy drying of the laundry.

Finally, it can be seen that at the air / water heat exchanger 7 it is possible to heat water up to 30 ° C. This water can for example be stored in a water tank.

Study of the influence of the temperature Tn_ {air entering the air / water exchanger 7)

With a view to the dimensioning of the treatment device 1 according to the invention, it may be useful to know up to what temperature it is necessary to cool, in the air / air exchanger 6, the moist and hot air coming from the drum 4 This temperature will influence the exchange surface and therefore the size and cost of the heat exchanger.

The values of the input parameters of the typical cycle were taken (T ₈ = 70 ° C., 83 = 45%, T 13 = 25 ° C. and Qv ₃ = 1200 m ³ / h) and the value of Tu was varied. from 31 to 40 ° C.

Figure 3 shows the evolution of energy gain with Tu.

It follows from this figure 3 that it is advantageous to have an air / air exchanger 6 as efficient as possible. This is explained because if in the hot circuit of this exchanger 6 the air gives way a large amount of thermal energy, then in the cold circuit the air returning to the heater 5 will recover a large amount of thermal energy. The amount of electrical energy to be supplied to the resistors in the heater 5 to reduce the air to 70 ° C will be reduced accordingly.

In Figure 4, we can observe for the same variation of Tu, the evolution of the power exchanged in the air / air heat exchanger 6. It can be seen that the energy gain obtained for the low values of Tu leads to a fairly clear increase heat exchange exchanged in the air / air heat exchanger 6 and therefore its exchange surface, its size and its cost.

Study of the influence of the temperature T (air leaving the air / air exchanger 6)

The temperature Tn is important because, first of all, the more the air is cooled by the water in the water / water heat exchanger 6, the more the steam will be condensed and thus the air obtained will be dry. It should also be noted that in the end the water that condenses is actually water that has been removed from the laundry. Therefore, a low Tn temperature is synonymous with faster drying. In addition, excessively cooling the air in the air / water heat exchanger 7 will require providing a greater amount of heat in the heater 5 to bring the air back to 70 ° C.

T ₈ was thus set at 70 ° C, ε ₃ at 45%, T "at 35 ° C and Qv ₃ at 1200 m ³ / h, and the temperature Ti ₃ was varied between 16 and 32 ° C, as we can see it in figure 5.

It appears that it may be disadvantageous from the point of view of the electrical consumption too much to cool the air in the air / fluid exchanger 7. Another disadvantage of cooling the air to a low temperature is that it is necessary to have a cooling water 12 which is at a temperature below T ₁₃ , which is not always possible.

The curve of Figure 6 shows that even at relatively high temperatures T ₁₃ , the relative humidity of the air entering the drum 4 remains quite low (at most 15% when T ₁₃ = 32 ° C). From the point of view of drying, a temperature T _{13 of} up to 30 ° C. can be used. Similarly, it is possible to have cooling water at around 25 ° C.

The invention can thus both minimize the energy expenditure required for a drying cycle and eliminate the constraining and costly systems for exhausting moist air to the outside. It is advisable to favor an operating mode in which the air / air exchanger must be the most efficient possible and lead to a temperature of the air entering the air / water heat exchanger as low as possible, preferably between 30 and 35. ° C.

The invention can be applied for example to the treatment of air from household or industrial dryers, laundry or self-service laundry. The invention can also be applied to the dehumidification of the pool air, the water heated in the air / water heat exchanger can for example be poured into the pool or into a hot water tank. The invention can still be applied to any industry where hot air is used to dry wet foods.

The phrase "with one" should be understood as synonymous with

"With at least one" unless otherwise specified.

Claims

1. A device for treating (1) hot and humid air from at least one drying installation, in particular a dryer (10), comprising:

an inlet for receiving the air to be treated coming from the outlet (3) of the drying installation,

an air / air exchanger (6) in which circulates the air to be treated, at least one air / fluid exchanger (7a, 7b) for dehumidifying the air to be treated, Γ air / air exchanger (6) and said at least one air / fluid exchanger (7a, 7b) being arranged in series so as to allow the air to be treated to heat air from said at least one air / fluid exchanger (7a, 7b) and / or air from the outside,

at least one air outlet after treatment connected to the inlet (2) of the drying installation,

at least one bypass (15, 16, 22) of said at least one air / fluid exchanger (7a, 7b).

2. Device according to claim 1, said at least one bypass (15, 16, 22) being a first bypass (15) connecting the outlet (3) of the drying installation to the inlet (2) of the installation drying and / or a second bypass (16) connecting the outlet (11) of the air / air exchanger (6) to the inlet (2) of the drying installation and / or a third bypass (22) allowing a recirculation of the air to be treated leaving the air / air exchanger (6) in it again before returning to the entrance of the drying installation.

3. Device according to claim 1 or 2, comprising at least two air / fluid exchangers (7a, 7b) or at least one air / fluid exchanger at least two stages.

4. Device according to one of the preceding claims, comprising a fourth bypass (17) connecting the outlet (18) of the air / fluid exchanger (7a, 7b) to the inlet (2) of the drying installation.

5. Device according to any one of the preceding claims, comprising a liquid circuit (20) for cooling said at least one air / fluid exchanger (7a, 7b), the liquid circuit (20) being equipped with a valve of regulation (21), in particular a three-way valve, for varying the quantity of liquid fed into the liquid circuit (20) in order to regulate the temperature of said at least one air / fluid exchanger (7a, 7b).

6. Device according to any one of the preceding claims, comprising a filtration system provided with an alarm, including sound and / or light, providing information on the efficiency of the filtration system.

7. A method of regulating the operation of a device according to any one of the preceding claims, wherein the operation of said at least one air / fluid exchanger (7a, 7b) is regulated according to at least one control parameter.

8. Method according to the preceding claim, comprising the following successive steps:

- diverting the air to be treated from the outlet (3) of the drying installation to the inlet (2) of the drying installation via said at least one bypass (15, 16, 22), in particular the first bypass (15) and / or the second bypass (16) and / or the third bypass (22), until reaching a predetermined value of the at least one control parameter,

- Allow the passage of the air to be treated in said at least one air / fluid exchanger (7a, 7b) when the predetermined value of said at least one control parameter is reached.

9. Method according to one of claims 7 to 8, said at least one control parameter being a temperature and / or a moisture content and / or a time, including the temperature in the dryer (10) and / or the rate humidity in the dryer (10) and / or an operating time of the dryer (10).

10. Process according to any one of claims 7 to 9, the treatment device (1) comprising at least two air / fluid exchangers (7a, 7b) or an air / fluid exchanger with at least two stages, the process comprising a step of directing the air to be treated in a single air / fluid exchanger or in a single stage of an air / fluid exchanger at least two stages so as to increase the cooling efficiency of the air to be treated.

11. Method according to the preceding claim, comprising the step of stopping the operation of at least one heater (5) of the drying installation.

12. Method according to any one of claims 7 to 11, the treatment device (1) comprising a liquid circuit (20) for cooling said at least one air / fluid exchanger (7a, 7b), the temperature of said at least one air / fluid exchanger (7a, 7b) being regulated between 5 and 30 ° C, in particular between 10 and 28 ° C.

13. A method according to any one of claims 7 to 10, the processing device (1) comprising a fourth bypass (17) connecting the outlet (9) of said at least one air / fluid exchanger (7a, 7b) to the inlet (2) of the drying plant, the method comprising the step of diverting the air to be treated from the outlet (9) of the at least one air / fluid exchanger (7a, 7b) to the inlet (2 ) of the drying installation so as to avoid a warming of the air to be treated in Γ air / air exchanger (6).

14. Installation comprising a treatment device (1) according to any one of claims 1 to 6 and at least one drying installation, including a dryer (10).