AU2012331506A1

AU2012331506A1 - A laundry dryer with a heat pump system and air recirculation

Info

Publication number: AU2012331506A1
Application number: AU2012331506A
Authority: AU
Inventors: Francesco Cavarretta
Original assignee: Electrolux Home Products Corp NV
Current assignee: Electrolux Home Products Corp NV
Priority date: 2011-10-31
Filing date: 2012-10-29
Publication date: 2014-05-01
Anticipated expiration: 2032-10-29
Also published as: WO2013064236A1; AU2012331506B2; EP2586907A1; CN103946443A; CN103946443B; EP2586907B1

Abstract

The present invention relates to a laundry dryer with a heat pump system comprising a refrigerant circuit (10) for a refrigerant and an air stream circuit (12) for an air stream. The refrigerant circuit (10) includes a compressor (14), a first heat exchanger (16), an expansion device (18) and a second heat exchanger (20) connected in series and forming a closed loop. The air stream circuit (12) includes at least one air stream fan (24), a laundry drum (26), the second heat exchanger (20) and the first heat exchanger (16) connected in series and forming a closed loop. The refrigerant circuit (10) and the air stream circuit (12) are thermally coupled by the first heat exchanger (16) and the second heat exchanger (20). The first heat exchanger (16) is provided for heating up the air stream and cooling down the refrigerant. The second heat exchanger (20) is provided for cooling down the air stream and heating up the refrigerant, The air stream circuit (12) includes a recirculation channel (22), wherein an inlet of said recirculation channel (22) is arranged between an air stream outlet of the first heat exchanger (16) and an inlet of the laundry drum (26) and an outlet of said recirculation channel (22) is arranged between an air stream outlet of the second heat exchanger (20) and an air stream inlet of the first heat exchanger (16).

Description

WO 2013/064236 PCT/EP2012/004520 Description 5 A LAUNDRY DRYER WITH A HEAT PUMP SYSTEM AND AIR RECIRCULATION The present invention relates to a laundry dryer with a heat pump system according to the preamble of claim 1. 10 In a laundry dryer the heat pump technology is at present the most efficient way to dry laundry by reduced energy consumption. In a conventional heat pump laundry dryer an air stream flows in a closed air stream circuit. The air stream is moved by an air stream fan and passes through a 15 laundry drum removing water from wet clothes. Then, the air stream is cooled down and dehumidified in an evaporator or gas heater and heated up in a condenser or gas cooler. At last, the air stream is re-inserted into the laundry drum again. 20 A refrigerant flows in a closed refrigerant circuit. The refrigerant is compressed by a compressor. Then, the re frigerant is condensed in the condenser or cooled down in the gas cooler. Next, the refrigerant is laminated in an 25 expansion device. At last, the refrigerant is vaporized in the evaporator or heated up in the gas heater. If the re frigerant operates at a pressure equal or higher than the critical pressure, then it is cooled down in the gas cooler and heated up in the gas heater, respectively. The tempera 30 tures of the air stream and the refrigerant are strictly connected to each other.

WO 2013/064236 PCT/EP2012/004520 2 The cycle of the laundry dryer with the heat pump system comprise two phases, i.e. a transitory phase and a steady state phase. At the beginning of the cycle, the tempera 5 tures of the air stream and the refrigerant are usually at ambient temperature. During the transitory phase the tem peratures of the air stream and the refrigerant increase up to a desired level. During the steady state phase the tem peratures of the air stream and the refrigerant are kept 10 constant until the laundry is dried. During the transitory phase the drying rate is very low, since the temperature at the inlet of the laundry drum is still low. In order to remove water from the wet laundry a 15 high temperature at the inlet of the laundry drum is re quired. Further, the high temperature allows then, that the air stream is dehumidified in the evaporator. Moreover, the temperature of the air stream at the outlet of the evapora tor decreases in the beginning of the cycle below the ini 20 tial value, i.e. the ambient temperature, since the tem perature of the refrigerant decreases in the evaporator, after the compressor has started to work. FIG 2 illustrates the time development of the temperatures 25 of the air stream at several points of the air stream chan nel. The temperature T-LD-OUT of the air stream at the out let of the laundry drum corresponds with the temperature T EV-IN of the air stream at the inlet of the evaporator. The temperature T-EV-OUT of the air stream at the outlet of the 30 evaporator corresponds with the temperature T-CO-IN of the air stream at the inlet of the condenser. The temperature WO 2013/064236 PCT/EP2012/004520 3 T-CO-OUT of the air stream at the outlet of the condenser corresponds with the temperature T-LD-IN of the air stream at the inlet of the laundry drum. 5 At the beginning of the drying cycle the above temperatures T-LD-OUT, T-EV-OUT and T-CO-OUT of the air stream are at the ambient temperature T-AM. The temperature T-CO-OUT of the air stream at the outlet of the condenser increases during the transitory phase. The temperature T-LD-OUT of 10 the air stream at the outlet of the laundry drum can de crease marginally, but increases during the substantial part of the transitory phase. The temperature T-EV-OUT of the air stream at the outlet of the evaporator decreases at first, but increases during the substantial part of the 15 transitory phase. However, during the first half of the transitory phase the temperature T-EV-OUT of the air stream at the outlet of the evaporator is below the ambient tem perature T-AM. In this example, after about 50 minutes, the drying cycle enters the steady state phase. During the 20 steady state phase the temperatures T-LD-OUT, T-EV-OUT and T-CO-OUT of the air stream are substantially at constant values. The condensation temperature of the refrigerant is close to 25 the temperature T-CO-OUT of the air stream at the outlet of the condenser, while the evaporation temperature is margin ally lower than the temperature T-EV-OUT of the air stream at the outlet of the evaporator. The flow rate of the re frigerant depends on the evaporation temperature. The 30 higher the evaporation temperature, the higher is the flow rate of the refrigerant and the heating and cooling power WO 2013/064236 PCT/EP2012/004520 4 of the heat pump system. In fact, the higher evaporation temperature causes a higher evaporation pressure and a higher density at the inlet of the compressor. At the same time, the temperature of the air stream depends on the con 5 densation temperature of the refrigerant. Thus, it would be advantageous, if the transitory time is relative short and the temperatures of the air stream increase fast. EP 1 664 647 Bl discloses a drying apparatus for drying a 10 subject, wherein the refrigerant is circulated through the compressor, a radiator, an expansion mechanism and the evaporator. The drying air is heated by the radiator, flown to the subject to be dried and dehumidified by the evapora tor. A part of the drying air heated by the radiator flows 15 through a bypass circuit directly to the evaporator without coming into contact with the subject to be dried. It is an object of the present invention to provide a laun dry dryer with a heat pump system, which allows a shortened 20 transitory phase by low complexity. The object of the present invention is achieved by the laundry dryer according to claim 1. 25 According to the present invention the air stream circuit includes a recirculation channel, wherein an inlet of said recirculation channel is arranged between an air stream outlet of the first heat exchanger and an inlet of the laundry drum and an outlet of said recirculation channel is 30 arranged between an air stream outlet of the second heat WO 2013/064236 PCT/EP2012/004520 5 exchanger and an air stream inlet of the first heat ex changer. The present invention provides a recirculation of the air 5 stream from the connection between the air stream outlet of the first heat exchanger and inlet of the laundry drum to the connection between the air stream outlet of the second heat exchanger and the air stream inlet of said first heat exchanger. In particular, the recirculation of the air 10 stream is activated during the transitory phase or warm-up phase of the drying cycle. In this case, only a part of the air stream is transferred into the laundry drum. The recir culation channel provides an increasing of the temperature of the air stream during the transitory mode is speeded up. 15 Thus, the drying cycle is shortened. For example, the air stream fan is arranged downstream of the first heat exchanger, wherein the inlet of the recircu lation channel is preferably arranged downstream of said 20 air stream fan. Alternatively, the air stream fan is arranged upstream of the first heat exchanger, wherein the outlet of the recir culation channel is preferably arranged upstream of said 25 first heat exchanger. Preferably, the recirculation channel comprises at least one airflow adjusting device or corresponds with at least one airflow adjusting device, wherein said airflow adjust 30 ing device is provided for opening and closing the recircu- WO 2013/064236 PCT/EP2012/004520 6 lation channel. Thus, the recirculation channel is control lable. For example, the airflow adjusting device is provided for 5 opening and closing the recirculation channel by an on-off mode. Alternatively, the airflow adjusting device may be provided for a continuous opening and closing of the recirculation 10 channel, so that the amount of the recirculated air stream is controlled or controllable by the airflow adjusting de vice. Further, the airflow adjusting device is controlled or con 15 trollable in dependence of the temperature of the air stream. In particular, the airflow adjusting device is con trolled or controllable in dependence of the temperature of the air stream at an inlet of the laundry drum. Moreover, the airflow adjusting device may be controlled or control 20 lable in dependence of the temperature of the air stream at an air stream inlet of the first heat exchanger. Additionally or alternatively, the airflow adjusting device is controlled or controllable in dependence of the tempera 25 ture of the refrigerant. For example, the airflow adjusting device is controlled or controllable in dependence of the temperature of the refrigerant at a refrigerant inlet of the first heat exchanger. In a similar way, the airflow ad justing device may be controlled or controllable in depend 30 ence of the temperature of the refrigerant at a refrigerant outlet of the first heat exchanger.

WO 2013/064236 PCT/EP2012/004520 7 According to another example, the airflow adjusting device is controlled or controllable according to a predetermined time scheme. 5 For example, the airflow adjusting device comprises at least one flap. Further, the airflow adjusting device may comprise at least one valve. 10 The first heat exchanger acts as a gas cooler, if the re frigerant remains in a gaseous state. In another situation the first heat exchanger may act as a condenser, if the re frigerant at least partially transfers from the gaseous state to a liquid state. 15 The second heat exchanger acts as a gas heater, if the re frigerant remains in the gaseous state. In contrast, the second heat exchanger acts as an evaporator, if the refrig erant at least partially transfers from the liquid state to 20 the gaseous state. The invention will be described in further detail with ref erence to the drawings, in which 25 FIG 1 shows a schematic diagram of a heat pump system for a laundry dryer according to a first embodiment of the present invention, FIG 2 shows a schematic diagram of the heat pump system 30 for the laundry dryer according to a second embodi ment of the present invention, and WO 2013/064236 PCT/EP2012/004520 8 FIG 3 shows a schematic diagram of temperatures of an air stream at several point of an air stream channel as a function of the time. 5 FIG 1 illustrates a schematic diagram of a heat pump system for a laundry dryer according to a first embodiment of the present invention. The heat pump system includes a closed refrigerant circuit 10 and an air stream circuit 12 for the 10 drying air. The refrigerant circuit 10 includes a compressor 14, a con denser 16, an expansion device 18 and an evaporator 20. The compressor 14, the condenser 16, the expansion device 18 15 and the evaporator 20 are switched in series and form a closed loop. The air stream circuit 12 includes the evapo rator 20, the condenser 16, an air stream fan 24, a laundry treatment chamber 26, preferably a rotatable drum, and a recirculation channel 22. The evaporator 20, the condenser 20 16, the air stream fan 24 and the laundry drum 26 are switched in series and form a loop. The recirculation chan nel 22 is arranged anti-parallel to the condenser 16 and air stream fan 24. In other words, the re-circulation chan nel 22 is arranged parallel to the laundry drum 26 and 25 evaporator 20. The drying air stream circuit 12 is preferably a closed loop in which the process air is continuously circulated through the laundry storing chamber. However it may also be 30 provided that a (preferably smaller) portion of the process air is exhausted from the process air loop and fresh air WO 2013/064236 PCT/EP2012/004520 9 (e.g. ambient air) is taken into the process air loop to replace the exhausted process air. And/or the process air loop is temporally opened (preferably only a short section of the total processing time) to have an open loop dis 5 charge The condenser 16 comprises an air stream inlet and an air stream outlet as well as a refrigerant inlet and a refrig erant outlet. In a similar way, the evaporator 20 comprises 10 an air stream inlet and an air stream outlet as well as a refrigerant inlet and a refrigerant outlet. The refrigerant is compressed by the compressor 14 and con densed by the condenser 16. The refrigerant is laminated in 15 the expansion device 18 and vaporized in the evaporator 20. The air stream is driven by the air stream fan 24 and passes through the laundry drum 26 removing water from wet laundry. Then, the air stream is cooled down and dehumidi fied by the evaporator 20, heated up in the condenser 16 20 and re-inserted into the laundry drum 26 again. By the recirculation channel 22 a part of the air stream flows from the outlet of the condenser 16 directly to the inlet of said condenser 16 via the air stream fan 24 during 25 a transitory phase of the drying cycle. This part of the air stream passes by the laundry drum 26 and the evaporator 20 through the recirculation channel 22. Then, this part of the air stream is mixed with that part of the air stream, which comes from the evaporator. In this way, the tempera 30 ture of the air stream at the inlet of the condenser 16 in creases, so that the temperatures of the air stream at the WO 2013/064236 PCT/EP2012/004520 10 outlet of the condenser 16 and at the inlet of the evapora tor 20 increase as well. Thus, the partially recirculation of the air stream from the outlet to the inlet of the con denser 16 allows an increasing of the temperatures of the 5 air stream and a shortening of the transitory phase of the drying cycle. An airflow adjusting device, for example a pivoting flap, a valve, a valve assembly or another similar device, is pro 10 vided in order to open and close said recirculation channel 22. Thus, the recirculation channel 22 can be activated and deactivated by the airflow adjusting device. Preferably, the airflow adjusting device is arranged within the recir culation channel 22. The airflow adjusting device is not 15 explicitly shown in FIG 1. Preferably, the recirculation channel 22 is interconnected between the outlet of the air stream fan 24 and the inlet of the condenser 16 as shown in FIG 1. In other words, an 20 inlet of the recirculation channel 22 is arranged down stream of the air stream fan 24. Since the recirculation channel 22 can be activated and de activated by the airflow adjusting device, the heat pump 25 system can work in two different operation modes, namely in a partial recirculation mode and in a traditional mode. In the partial recirculation mode the airflow adjusting device is opened or partially opened, so that a part of the air stream is recirculated from the outlet to the inlet of the 30 condenser 16. In the traditional mode the airflow adjusting device is closed, so that the complete air stream from the WO 2013/064236 PCT/EP2012/004520 11 outlet of the condenser 16 is transferred to the inlet of the laundry drum 26. The traditional mode corresponds with a heat pump system without the recirculation channel 22. 5 The recirculation channel 22 provides an increasing of the temperature of the air stream is speeded up during the transitory mode. Thus, the increasing of the condensation and evaporation temperatures of the refrigerant is also speeded up and the transitory phase is shortened. Only a 10 part of the air stream passes through the recirculation channel 22. The main part of the air stream passes through the laundry drum 26 and evaporator 20 in the same way as in a conventional heat pump system. 15 The partial recirculation mode is switched off by closing the airflow adjusting device. Preferably, the partial re circulation mode is switched off, if the temperature of the air stream at the air stream inlet and/or the air stream outlet of the condenser 16 reach a predetermined value. 20 Further, the partial recirculation mode may be switched off, if the temperature of the refrigerant at the refriger ant inlet and/or the refrigerant outlet of the condenser 16 reaches a predetermined value. Moreover, the partial recir culation mode may be switched off after a predetermined 25 time. For example, said predetermined time starts, when the compressor 14 begins to work. When the recirculation chan nel 22 is closed by the airflow adjusting device, then the complete air stream passes through the laundry drum 26, the evaporator 20 and the condenser 16. 30 WO 2013/064236 PCT/EP2012/004520 12 Further, the airflow adjusting device can be continuously opened and closed, so that the amount of the air stream through recirculating channel 22 is variable. Thus, the amount of the recirculated air stream can be adapted to the 5 thermodynamic conditions of the heat pump system. Addition ally, the changeover from the partial recirculation mode and to the traditional mode can be smoothed. The above heat pump system with the recirculation channel 10 22 is also suitable, if the refrigerant, e.g. carbon diox ide, operates at least at the critical pressure in a high pressure portion and eventually in a low pressure portion of the refrigerant circuit 10, so that the refrigerant is always in the gaseous state and no condensation and eventu 15 ally no evaporation occur. FIG 2 illustrates a schematic diagram of the heat pump sys tem for the laundry dryer according to a second embodiment of the present invention. The heat pump system includes the 20 closed refrigerant circuit 10 and the air stream circuit 12 for the drying air. The refrigerant circuit 10 includes the compressor 14, the condenser 16, the expansion device 18 and the evaporator 20 25 switched in series and forming a closed loop. The air stream circuit 12 includes the evaporator 20, the air stream fan 24, the condenser 16, the laundry drum 26 and the recirculation channel 22. The evaporator 20, the air stream fan 24, the condenser 16 and the laundry drum 26 are 30 switched in series and form a loop. The recirculation chan nel 22 is arranged anti-parallel to the air stream fan 24 WO 2013/064236 PCT/EP2012/004520 13 and the condenser 16. In other words, the re-circulation channel 22 is arranged parallel to the laundry drum 26 and evaporator 20. 5 In the second embodiment the air stream fan 24 is arranged upstream of the condenser 16, while the air stream fan 24 is arranged downstream of the condenser 16 in the first em bodiment. Further, the outlet of the recirculation channel 22 is arranged, preferably, upstream of the air stream fan 10 24. FIG 3 illustrates a time development of the temperatures of the air stream at several points of the air stream channel. The temperature T-LD-OUT of the air stream at the outlet of 15 the laundry drum 26 corresponds with the temperature T-EV IN of the air stream at the inlet of the evaporator 20. The temperature T-EV-OUT of the air stream at the outlet of the evaporator 20 corresponds with the temperature T-CO-IN of the air stream at the inlet of the condenser 16. The tem 20 perature T-CO-OUT of the air stream at the outlet of the condenser 16 corresponds with the temperature T-LD-IN of the air stream at the inlet of the laundry drum 26. At the beginning of the drying cycle the above temperatures 25 T-LD-OUT, T-EV-OUT and T-CO-OUT of the air stream are at the ambient temperature T-AM. The temperature T-CO-OUT of the air stream at the outlet of the condenser 16 increases during the transitory phase. The temperature T-LD-OUT of the air stream at the outlet of the laundry drum 26 can de 30 crease marginally, but increases during the substantial part of the transitory phase. The temperature T-EV-OUT of WO 2013/064236 PCT/EP2012/004520 14 the air stream at the outlet of the evaporator 20 decreases at first, but increases during the substantial part of the transitory phase. However, during the first half of the transitory phase the temperature T-EV-OUT of the air stream 5 at the outlet of the condenser 16 is below the ambient tem perature T-AM. During the steady state phase the tempera tures T-LD-OUT, T-EV-OUT and T-CO-OUT of the air stream are substantially at constant values. 10 The heat pump system with the recirculation channel 22 al lows a shorter transitory phase of the drying cycle. Thus, the time for the drying cycle is reduced. That part of the cycle, in which the temperature T-EV-OUT becomes lower than the ambient temperature T-AM is reduced or eliminated. 15 Although illustrative embodiments of the present invention have been described herein with reference to the accompany ing drawings, it is to be understood that the present in vention is not limited to those precise embodiments, and 20 that various other changes and modifications may be af fected therein by one skilled in the art without departing from the scope or spirit of the invention. All such changes and modifications are intended to be included within the scope of the invention as defined by the appended claims.

WO 2013/064236 PCT/EP2012/004520 15 List of reference numerals 10 refrigerant circuit 12 air stream circuit 5 14 compressor 16 first heat exchanger, condenser, gas cooler 18 expansion device 20 second heat exchanger, evaporator, gas heater 22 recirculation channel 10 24 air stream fan 26 laundry drum T-LD-OUT temperature at the outlet of the laundry drum T-EV-OUT temperature at the outlet of the evaporator 15 T-CO-OUT temperature at the outlet of the condenser T-LD-IN temperature at the inlet of the laundry drum T-EV-IN temperature at the inlet of the evaporator T-CO-IN temperature at the inlet of the condenser T-AM ambient temperature

Claims

1. A laundry dryer with a heat pump system comprising a refrigerant circuit (10) for a refrigerant and an air 5 stream circuit (12) for an air stream, wherein - the refrigerant circuit (10) includes a compressor (14), a first heat exchanger (16), an expansion de vice (18) and a second heat exchanger (20) con nected in series and forming a closed loop, 10 - the air stream circuit (12) includes at least one air stream fan (24), a laundry drum (26), the sec ond heat exchanger (20) and the first heat ex changer (16), - the refrigerant circuit (10) and the air stream 15 circuit (12) are thermally coupled by the first heat exchanger (16) and the additional heat ex changer (22), - the first heat exchanger (16) is provided for heat ing up the air stream and cooling down the refrig 20 erant, and - the second heat exchanger (24) is provided for cooling down the air stream and heating up the re frigerant, characterized in, that 25 the air stream circuit (12) includes a recirculation channel (22), wherein an inlet of said recirculation channel (22) is arranged between an air stream outlet of the first heat exchanger (16) and an inlet of the laundry drum (26) and an outlet of said recirculation 30 channel (22) is arranged between an air stream outlet WO 2013/064236 PCT/EP2012/004520 17 of the second heat exchanger (24) and an air stream inlet of the first heat exchanger (16).

2. The laundry dryer according to claim 1, 5 characterized in, that the air stream fan (24) is arranged downstream of the first heat exchanger (16), wherein the inlet of the re circulation channel (22) is arranged downstream of said air stream fan (24). 10

3. The laundry dryer according to claim 1, characterized in, that the air stream fan (24) is arranged upstream of the first heat exchanger (16), wherein the outlet of the 15 recirculation channel (22) is arranged upstream of said first heat exchanger (16).

4. The laundry dryer according to any one of the preceding claims, 20 characterized in, that the recirculation channel (22) comprises at least one airflow adjusting device or corresponds with at least one airflow adjusting device, wherein said airflow ad justing device is provided for opening and closing the 25 recirculation channel (22).

5. The laundry dryer according to claim 4, characterized in, that the airflow adjusting device is provided for opening 30 and closing the recirculation channel (22) by an on-off mode. WO 2013/064236 PCT/EP2012/004520 18

6. The laundry dryer according to claim 4 or 5, characterized in, that the airflow adjusting device is provided for a continu 5 ous opening and closing of the recirculation channel (22), so that the amount of the recirculated air stream is controlled or controllable by the airflow adjusting device. 10

7. The laundry dryer according to any one of the claims 4 to 6, characterized in, that the airflow adjusting device is controlled or control lable in dependence of the temperature of the air 15 stream.

8. The laundry dryer according to claim 7, characterized in, that the airflow adjusting device is controlled or control 20 lable in dependence of the temperature of the air stream at an inlet of the laundry drum (26) and/or at an air stream inlet of the first heat exchanger (16).

9. The laundry dryer according to any one of the claims 4 25 to 8, characterized in, that the airflow adjusting device is controlled or control lable in dependence of the temperature of the refriger ant. 30

10. The laundry dryer according to claim 9, WO 2013/064236 PCT/EP2012/004520 19 characterized in, that the airflow adjusting device is controlled or control lable in dependence of the temperature of the refriger ant at a refrigerant inlet of the first heat exchanger 5 (16) and/or at a refrigerant outlet of the first heat exchanger (16).

11. The laundry dryer according to any one of the claims 4 to 10, 10 characterized in, that the airflow adjusting device is controlled or control lable according to a predetermined time scheme.

12. The laundry dryer according to any one of the claims 4 15 to 11, characterized in, that the airflow adjusting device comprises at least one flap. 20

13. The laundry dryer according to any one of the claims 4 to 12, characterized in, that the airflow adjusting device comprises at least one valve. 25

14. The laundry dryer according to any one of the preceding claims, characterized in, that the first heat exchanger (16) acts as a gas cooler and 30 the second heat exchanger (20) acts as a gas heater, if the refrigerant remains in the gaseous state. WO 2013/064236 PCT/EP2012/004520 20

15. The laundry dryer according to any one of the preceding claims, characterized in, that 5 the first heat exchanger (16) acts as a condenser and the second heat exchanger (20) acts as an evaporator, if the refrigerant at least partially transfers from the liquid state to the gaseous state. 10