U.S. patent application number 13/795675 was filed with the patent office on 2014-01-23 for method for controlling a laundry drying machine with heat pump system and laundry drying machine controlled by such method.
This patent application is currently assigned to WHIRLPOOL CORPORATION. The applicant listed for this patent is WHIRLPOOL CORPORATION. Invention is credited to JAMES P. CAROW, MOEED MUKHTAR, JURIJ PADERNO, PAOLO SPRANZI.
Application Number | 20140020260 13/795675 |
Document ID | / |
Family ID | 46679114 |
Filed Date | 2014-01-23 |
United States Patent
Application |
20140020260 |
Kind Code |
A1 |
CAROW; JAMES P. ; et
al. |
January 23, 2014 |
METHOD FOR CONTROLLING A LAUNDRY DRYING MACHINE WITH HEAT PUMP
SYSTEM AND LAUNDRY DRYING MACHINE CONTROLLED BY SUCH METHOD
Abstract
A laundry drying machine with a heat pump system comprises a
process air circuit including a rotating drum, a blower and a
heater, a refrigerant circuit including a compressor, a condenser,
an expansion device, an evaporator, the condenser and evaporator
being in heat exchange relationship with the process air circuit,
an auxiliary condenser cooled by an air flow driven by a fan, and
at least two temperature sensors placed in the process air circuit
and/or in the refrigerant circuit. A method for controlling the
laundry drying machine includes receiving an input indicating a
desired behavior of the laundry drying machine selected from the
group consisting of optimized use of energy, overall drying time
and fabric care, and controlling components of the machine
according to signals from the two temperature sensors and according
to the desired behavior.
Inventors: |
CAROW; JAMES P.; (SAINT
JOSEPH, MI) ; MUKHTAR; MOEED; (SAINT JOSEPH, MI)
; PADERNO; JURIJ; (NOVATE MILANESE, IT) ; SPRANZI;
PAOLO; (BORGOSATOLLO, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WHIRLPOOL CORPORATION |
Benton Harbor |
MI |
US |
|
|
Assignee: |
WHIRLPOOL CORPORATION
Benton Harbor
MI
|
Family ID: |
46679114 |
Appl. No.: |
13/795675 |
Filed: |
March 12, 2013 |
Current U.S.
Class: |
34/427 |
Current CPC
Class: |
D06F 58/20 20130101;
D06F 58/206 20130101; D06F 2103/50 20200201; D06F 58/30 20200201;
D06F 2105/26 20200201 |
Class at
Publication: |
34/427 |
International
Class: |
D06F 58/20 20060101
D06F058/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 23, 2012 |
EP |
12177506.8 |
Claims
1. A method for controlling a laundry drying machine with a heat
pump system comprising a process air circuit including a rotating
drum, a blower and a heater, a refrigerant circuit including a
compressor, a condenser, an expansion device, an evaporator, the
condenser and evaporator being in heat exchange relationship with
the process air circuit, an auxiliary condenser cooled by an air
flow driven by a fan, and at least two temperature sensors placed
in the process air circuit and/or in the refrigerant circuit, the
method comprising: receiving an input indicating a desired behavior
of the laundry drying machine selected from the group consisting of
optimized use of energy, overall drying time and fabric care, and
controlling components of the laundry drying machine according to
signals from the two temperature sensors and according to the
desired behavior.
2. A method according to claim 1, wherein at least two components
of the laundry drying machine are controlled.
3. A method according to claim 2, wherein the at least two
components to be controlled are selected from the group consisting
of blower, heater, compressor and fan.
4. A laundry drying machine comprising: a heat pump system
comprising a process air circuit including a rotating drum, a
blower and a heater, a refrigerant circuit including a compressor,
a condenser, an expansion device, an evaporator, the condenser and
evaporator being in heat exchange relationship with the process air
circuit, an auxiliary condenser cooled by an air flow driven by a
fan, at least two temperature sensors placed in the process air
circuit and/or in the refrigerant circuit, a user interface
configured to allow a user to choose a desired behavior of the
laundry drying machine selected from the group consisting of
optimized use of energy, overall drying time and fabric care, and a
control unit coupled to the user interface and configured to
control components of the laundry drying machine according to
signals from the two temperature sensors and according to the
desired behavior.
5. A laundry drying machine according to claim 4, wherein at least
two of the components are adapted to be controlled.
6. A laundry machine according to claim 5, wherein the at least two
components to be controlled are selected from the group consisting
of the blower, the heater, the compressor, and the fan.
Description
RELATED APPLICATION
[0001] This application claims the priority benefit of European
Patent Application 12177506.8 filed on Jul. 23, 2012, the entirety
of which is hereby incorporated by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to methods for controlling a
laundry drying machine with a heat pump system comprising a process
air circuit including a rotating drum, a blower and a heater; a
refrigerant circuit including a compressor, a condenser, an
expansion device, an evaporator, the condenser and evaporator being
in heat exchange relationship with the process air circuit, and an
auxiliary condenser cooled by an air flow driven by a fan; and at
least two temperature sensors placed respectively in the process
air circuit and in the refrigerant circuit.
BACKGROUND
[0003] The so called "hybrid" heat pump dryers, in which the
process air is heated either by the condenser of a refrigerant
circuit and by an auxiliary heater are well known in the art.
Moreover, a hybrid heat pump dryer having an auxiliary condenser
with an auxiliary fan (cooled by ambient air) is known from
European Patent Application EP 999302.
[0004] Usually such hybrid heat pump dryers, despite being very
efficient in term of use of energy, offer to the user only a quite
limited range of choices for the drying process, for instance
degree of final humidity content of laundry, or long or short
drying cycle. Such few and simple choices can on one hand limit the
operational ranges of the machine, and on the other hand limit the
possible choices of the users which may depend on several
factors.
SUMMARY
[0005] The purpose of this disclosure is therefore a goal oriented
control method, which increases the choices of the user, and which
can particularly optimize a choice on low energy consumption, on
cycle overall time, or on fabric care of a hybrid heat pump
household tumble dryer, with an optimized balance between heating
and cooling power.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Further advantages and features of the disclosed methods and
laundry dryers according to the disclosure will become clear from
the following detailed description, with reference to the attached
drawings in which:
[0007] FIG. 1 is a schematic view of a hybrid heat pump tumble
dryer;
[0008] FIG. 2 is a block diagram showing a dual loop control
architecture according to the disclosure;
[0009] FIGS. 3-5 are examples of control implementations according
to different choices of the user based on energy strategy, time
strategy and fabric care strategy, respectively;
[0010] FIG. 6 is a block diagram showing a prior-art control
loop;
[0011] FIG. 7 is a diagram showing the temperature and residual
moisture content behavior in a dryer using the prior-art control
system of FIG. 6; and
[0012] FIGS. 8-10 are diagrams showing example energy optimized
cycle temperature behaviors, time optimized cycle temperature
behaviors and fabric care optimized cycle temperature behaviors,
respectively.
DETAILED DESCRIPTION
[0013] With reference to FIG. 1, the process air circuit is the one
that involves the evaporation of the water retained by the fabric
and it is made up of a rotating drum 10 actuated by an electric
motor and containing a certain amount of clothes, a process air
blower 12 that sets the circuit process airflow, a condenser 14 and
an heating element 16 that heat the air going inside the drum 10,
an evaporator 18 where the moisture contained in the process air
can condense, an auxiliary condenser 20 (sub-cooler), a compressor
22, an expansion tube 23, and a fan 26 for cooling the auxiliary
condenser 20 with ambient air.
[0014] The clothes dryer comprises also a NTC temperature sensor T1
placed on the process air exhaust from the drum 10, and a NTC
sensor T2 placed in the refrigerant circuit downstream from the
compressor 22, the temperature sensors T1 and T2 being connected to
a control process unit 28 that drives all components of the clothes
dryer according to certain processes.
[0015] The clothes dryer can also include also other components,
for example, an accumulator upstream of the compressor 22, which is
not shown in FIG. 1 for sake of clarity.
[0016] An air channel conveys the process air to the evaporator 18,
where the vapor contained in the air condenses due to the low
temperature.
[0017] The heat pump circuit is the one that involves the
refrigerant that with its phase variation transfers heat to the air
circuit. The temperature sensor T2 that measures the refrigerant
temperature may alternatively be placed in a position different
from compressor outlet, for instance in the capillary tube or other
places. The auxiliary fan 26 increases the heat exchange on the
auxiliary condenser 20.
[0018] Also the temperature sensor T1 may be placed in a different
position than the one shown in FIG. 1, but in any case it is placed
in the moist air circuit, by the drum outlet, the blower 12 or the
evaporator 18.
[0019] The second temperature sensor T2, instead of being placed in
the refrigerant circuit, may alternatively be placed in the moist
air circuit in a position different from the first sensor T1, for
instance by the heater 16, the condenser 14, or the auxiliary
condenser 20.
[0020] The controllable variables of the system, which may be
continuously adjusted or simply ON/OFF, are the compressor speed,
the process air blower speed, the heating element power and the
auxiliary fan speed.
[0021] Those variables are controlled in order to provide and
remove the right quantity of energy respectively by means of the
condenser 14 plus the heating element 16 and the evaporator 18, by
compromising between evaporation and condensation.
[0022] In the most of the cases, to reduce the cost of the system,
the motors of the compressor 22 and the process air blower 12 are
constant speed motors, therefore it is not possible to change their
speeds.
[0023] According to a common practice of controlling the clothes
dryer, the compressor 22 is kept on for the entire drying cycle
while the heater 16 switches on/off in order to manage the
temperature of the tumble dryer by feeding back the drum exhaust
temperature measured by sensor T1. Indeed, the drum output
temperature is usually a good approximation of the clothes
temperature which is therefore kept under control.
[0024] Since it is required that the compressor stay on, due to
inefficiency in turning off and on the heat pump system, and to
prevent shifting in the working point of the system that would
result in less energy removed in the evaporator 18, thus less
condensation and overheating of the compressor 22, its temperature
has to be controlled. Therefore when the temperature of the
compressor 22, sensed by sensor T2, reaches a certain value close
to the high limit temperature switch off, the auxiliary fan 26 is
turned on.
[0025] The feedback is usually made through hysteresis control,
i.e. the heater 16 and the auxiliary fan 26 are switched on when
the feedback temperature is below a predefined threshold and
switched off when it is above a second predefined threshold.
[0026] Up to now we have described a dryer which can be controlled
either according to prior art or according to the disclosure. As a
matter of fact the main drawback of the known control system is the
difficulty in creating a customized appliance behavior aiming to
optimize system performances according to customer choices, who may
desire to save energy, to save time or alternately to prefer a more
gentle treatment of clothes, for instance by keeping the drying
temperatures lower.
[0027] The methods according to the disclosure can control every
component of the clothes dryer, and preferably both the auxiliary
cooling fan 26 and the heater 16 of a tumble hybrid heat pump
dryer, optimizing alternatively energy consumption, drying time or
fabric care according to a selection made by the user by means of a
user interface 30. This selection can be done through a button,
touch display, cycle selection, etc.
[0028] Once the user has made his/her selection, the system
temperatures can be controlled by means of several actuators for
the auxiliary cooling fan 26, the heater 16, the compressor 22, and
the process air blower 12. The way all these actuators are used
affects the overall system performances in terms of energy
consumption, cycle duration, water extraction efficiency, final
moisture retention at the end of the cycle, fabric care (wrinkles,
shrinkage, etc.), etc..
[0029] The present disclosure provides therefore methods of
choosing how to use these actuators in the different parts of a
drying cycle.
[0030] The disclosure is effective even in the case of one or more
of the actuators cannot be continuously controlled, e.g. fixed
speed compressor, fixed speed fan, etc.
[0031] According to the disclosure, the drying cycle is
conceptually divided in three phases of variable duration: warm up
(WU), mid phase (MP) and cool down (CD). In the following
descriptions, the three phases will be identified by means of two
temperature measurements and cycle length.
[0032] In particular, naming:
[0033] t.sub.0=0 the beginning of the cycle,
[0034] t.sub.end the time at the end of the cycle,
[0035] t.sub.20=0.2*t.sub.end,
[0036] t.sub.50=0.5*t.sub.end,
[0037] t.sub.70=0.7*.sub.tend,
[0038] t.sub.80=0.8*t.sub.end,
[0039] T.sub.1.sub.--.sub.start the value of temperature T.sub.1
measured at time t.sub.0,
[0040] T.sub.1.sub.--.sub.mid the maximum value of temperature
T.sub.1 measured from t.sub.0 to t.sub.50,
[0041]
T.sub.1.sub.--.sub.threshold=(T.sub.1.sub.--.sub.mid-T.sub.1.sub.---
.sub.start)*0.8+T.sub.1.sub.--.sub.start,
[0042] t.sub.r1 the first time at which the temperature T.sub.1 is
greater than T.sub.1.sub.--.sub.threshold,
[0043] T.sub.2.sub.--.sub.start the value of temperature T.sub.2
measured at time t.sub.0,
[0044] T.sub.2.sub.--.sub.mid the maximum value of temperature
T.sub.2 measured from t.sub.0 to t.sub.50,
[0045]
T.sub.2.sub.--.sub.threshold=(T.sub.2.sub.--.sub.mid-T.sub.2.sub.---
.sub.start)*0.8+T.sub.2.sub.--.sub.start,
[0046] t.sub.r2 the first time at which the temperature T.sub.2 is
greater than T.sub.2.sub.--.sub.threshold,
[0047] t.sub.WU=min(t20, tr1, tr2)
[0048] t.sub.MP.sub.--start=max(t.sub.20, t.sub.WU*1.2)
[0049] t.sub.MP_end=t.sub.70
[0050] .sub.tCD.sub.--.sub.start=t.sub.80
[0051] The following definitions of the three phases of the cycle
are given:
[0052] Warm up (WU): starts at time t.sub.0 and ends at time
t.sub.WU
[0053] Mid phase (MP): starts at time t.sub.MP.sub.--start and ends
at time t.sub.MP.sub.--.sub.end
[0054] Cool down (CD): starts at time t.sub.CD.sub.--.sub.start and
ends at time t.sub.end
[0055] Moreover, naming:
[0056] P.sub.WU the average power absorbed by the heating element
during WU phase
[0057] P.sub.MP the average power absorbed by the heating element
during MP phase
[0058] P.sub.CD the average power absorbed by the heating element
during CD phase
[0059] S.sub.F.sub.--.sub.WU the average speed of the auxiliary fan
during WU phase
[0060] S.sub.F.sub.--.sub.MP the average speed of the auxiliary fan
during MP phase
[0061] S.sub.F.sub.--.sub.CD the average speed of the auxiliary fan
during CD phase
[0062] S.sub.C.sub.--.sub.WU the average speed of the compressor
during WU phase
[0063] S.sub.C.sub.--.sub.MP the average speed of the compressor
during MP phase
[0064] S.sub.C.sub.--.sub.CD the average speed of the compressor
during CD phase
[0065] S.sub.B.sub.--.sub.WU the average speed of the process air
blower fan during WU phase
[0066] S.sub.B.sub.--.sub.MP the average speed of the process air
blower fan during MP phase
[0067] S.sub.FB.sub.--.sub.CD the average speed of the process air
blower fan during CD phase
[0068] In case of discrete control the averages are computed taking
in account 0 as OFF and 1 as ON.
[0069] The disclosed controller 28 will be provided with the
possibility to operate in at least two of the following cycles
based on a selection made via the user interface 30, to which the
following values of parameters apply:
[0070] Energy Optimized Cycle, characterized by having:
P.sub.MP<0.2*P.sub.WU, P.sub.CD<0.2*P.sub.WU
S.sub.f.sub.--.sub.WU<0.25*S.sub.F.sub.--.sub.MP,
S.sub.f.sub.--.sub.CD>S.sub.F.sub.--.sub.WU
S.sub.C.sub.--.sub.CD=<S.sub.C.sub.--.sub.MP,
S.sub.C.sub.--.sub.CD=<S.sub.C.sub.--.sub.WU
S.sub.B.sub.--.sub.WU=<S.sub.B.sub.--.sub.MP=<S.sub.B.sub.--.sub.C-
D
[0071] Time Optimized Cycle, characterized by having:
0.5*P.sub.WU<P.sub.MP<1.2*P.sub.WU,
P.sub.CD<1.2*P.sub.WU
S.sub.f.sub.--.sub.WU<0.25*S.sub.F.sub.--.sub.MP,
S.sub.f.sub.--CD>S.sub.F.sub.--.sub.WU
S.sub.C.sub.--.sub.CD=<S.sub.C.sub.--.sub.MP,
S.sub.C.sub.--.sub.CD=<S.sub.C.sub.--.sub.WU
S.sub.B.sub.--.sub.WU=<S.sub.B.sub.--.sub.MP=<S.sub.B.sub.--.sub.C-
D
[0072] Fabric Care Optimized Cycle, characterized by having:
0.2*P.sub.WU<P.sub.MP<0.5*P.sub.WU,PCD<0.25*P.sub.WU
S.sub.f.sub.--.sub.WU<0.25*S.sub.F.sub.--.sub.MP,
S.sub.f.sub.--.sub.CD>S.sub.F.sub.--.sub.WU
S.sub.C.sub.--.sub.CD=<S.sub.C.sub.--.sub.MP,
S.sub.C.sub.--.sub.CD=<S.sub.C.sub.--.sub.WU
S.sub.B.sub.--.sub.WU=<S.sub.B.sub.--.sub.MP=<S.sub.B.sub.--.sub.C-
D
[0073] Of course the above parameter values are only examples and
they can change depending on the actual dryer in which the methods
according to the disclosure are implemented.
[0074] A conceptual scheme which is shown in FIG. 2, changes both
auxiliary fan motor speed and heating power according to two
temperature measurements by the sensors T1 and T2, thus controlling
the energy delivered to the load inside the drum 10 and the energy
removed from the refrigerant giving the possibility to optimize
different system performance objectives.
[0075] One example of the possible implementations of the control
strategy shown in FIG. 2, considering for sake of simplicity that
the process air blower 12 and compressor 22 are maintained at a
constant speed during the cycle, for the energy, the time and the
fabric care strategy are respectively drawn in the FIGS. 3-5. In
the examples of FIGS. 3-5, the temperature sensed by sensor T1 is
the drum outlet temperature while the temperature sensed by sensor
T2 is the capillary temperature of the refrigerant circuit.
[0076] The control strategy according to the disclosure has been
compared with a simple known strategy in which the hysteresis on T1
controls the heater actuation while the hysteresis on T2 controls
the fan actuation, as shown in FIG. 6, referred to a drying cycle
of a 4 kg load.
[0077] With the control system shown in FIG. 6, example results are
shown in FIG. 7, which shows an energy consumption of 1.69 kWh and
a drying time around 92 minutes. In the diagrams, reference A
indicates the temperature of process air entering the drum 10,
reference B indicates the temperature of air measured at the
exhaust of the drum 10, reference C indicates the capillary
temperature of the refrigerant circuit, and reference D indicates
the residual moisture content of the fabric inside the drum 10.
[0078] The example energy optimized cycle shown in FIG. 8
(corresponding to the example control scheme of FIG. 3), reveals a
lower energy consumption around 1.54 kWh (-9%) and a drying time
around 98 minutes (+8%) compared to the control system of FIGS. 6
and 7.
[0079] The example time optimized cycle shown in FIGS. 4 and 9 has
a comparable energy consumption 1.72 kWh (+2%) and a comparable
drying time, around 90 minutes (-1%).
[0080] The example fabric optimized cycle shown in FIGS. 5 and 10
keeps the fabric temperature low and avoids the temperature
increase at the cycle end and therefore reduces the stress on the
fabric. In terms of performances, the energy absorbed is slightly
below the reference cycle of FIGS. 6 and 7, i.e. 1.6 kWh (-5%) but
the drying time is increased lasting 118 minutes (+29%).
* * * * *