U.S. patent application number 11/576316 was filed with the patent office on 2009-05-14 for refrigeration system and method with controllable heat recovery.
This patent application is currently assigned to CARRIER CORPORATION. Invention is credited to Pierre Delpech, Michel K. Grabon, Ba-Tung Pham, Philippe Rigal.
Application Number | 20090120110 11/576316 |
Document ID | / |
Family ID | 36142890 |
Filed Date | 2009-05-14 |
United States Patent
Application |
20090120110 |
Kind Code |
A1 |
Grabon; Michel K. ; et
al. |
May 14, 2009 |
Refrigeration System and Method with Controllable Heat Recovery
Abstract
A method for providing controllable amounts of heat recovery
from a refrigerant circuit includes the steps of providing a
cooling circuit comprising a compressor, a condenser, an expansion
device and an evaporator connected in series by refrigerant flow
lines; providing a heat recovery circuit comprising a heat recovery
heat exchanger, the heat recovery circuit being connected to the
cooling circuit so that the heat recovery heat exchanger is in
parallel with the condenser, and the heat recovery heat exchanger
being in heat exchange relationship with a fluid to be heated based
upon an end-user demand for heat; and selectively flowing
refrigerant through the condenser of the cooling circuit and the
heat recovery heat exchanger of the heat recovery circuit so as to
maintain temperature of the fluid within a temperature hand around
a set point provided by the end user.
Inventors: |
Grabon; Michel K.;
(Bressolles, FR) ; Pham; Ba-Tung; (Chassieu,
FR) ; Rigal; Philippe; (Sevigneux, FR) ;
Delpech; Pierre; (Fleurieu-sur-saone, FR) |
Correspondence
Address: |
BACHMAN & LAPOINTE, P.C. (UTC)
900 CHAPEL STREET, SUITE 1201
NEW HAVEN
CT
06510-2802
US
|
Assignee: |
CARRIER CORPORATION
Farmington
CT
|
Family ID: |
36142890 |
Appl. No.: |
11/576316 |
Filed: |
September 30, 2005 |
PCT Filed: |
September 30, 2005 |
PCT NO: |
PCT/US05/35349 |
371 Date: |
March 29, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60615440 |
Sep 30, 2004 |
|
|
|
Current U.S.
Class: |
62/115 ; 62/119;
62/498 |
Current CPC
Class: |
F25B 2700/21163
20130101; F25B 6/00 20130101; F25B 2339/047 20130101; F25B 2400/19
20130101; F25B 2400/06 20130101; F24D 17/02 20130101; F25B 45/00
20130101; F25B 2400/0403 20130101 |
Class at
Publication: |
62/115 ; 62/119;
62/498 |
International
Class: |
F25B 1/00 20060101
F25B001/00; F25D 15/00 20060101 F25D015/00 |
Claims
1. A method for providing controllable amounts of heat recovery
from a refrigerant circuit, comprising the steps of: providing a
cooling circuit comprising a compressor, a condenser, an expansion
device and an evaporator connected in series by refrigerant flow
lines; providing a heat recovery circuit comprising a heat recovery
heat exchanger, the heat recovery circuit being connected to the
cooling circuit so that the heat recovery heat exchanger is in
parallel with the condenser, and the heat recovery heat exchanger
being in heat exchange relationship with a fluid to be heated based
upon an end-user demand for heat; and selectively flowing
refrigerant through the condenser of the cooling circuit and the
heat recovery heat exchanger of the heat recovery circuit so as to
maintain temperature of the fluid within a temperature band around
a set point provided by the end user.
2. The method of claim 1, further comprising a plurality of cooling
circuits and a plurality of heat recovery circuits, and wherein the
selectively flowing step comprises comparing a temperature of the
fluid with a fluid temperature setpoint and increasing a number of
heat recovery circuits which are active when the temperature is
below the fluid temperature setpoint.
3. The method of claim 2, further comprising the step of decreasing
the number of heat recovery circuits which are active when the
temperature is greater than the fluid temperature setpoint.
4. The method of claim 1, further comprising the step of cycling
the heat recovery circuit between an active mode wherein a
substantial portion of refrigerant passes through the heat recovery
heat exchanger and transfers heat to the fluid in heat exchange
relationship with the heat recovery heat exchanger; and an inactive
mode wherein a substantial portion of refrigerant flows to the
condenser.
5. The method of claim 1, further comprising selectively operating
in a cooling mode wherein the heat recovery heat exchanger is not
active, and a heat recovery mode wherein the condenser is not
active, and selectively recovering charge from whichever of the
condenser and the heat recovery heat exchanger is not active.
6. A refrigeration system with controllable heat recovery,
comprising: a cooling circuit having a compressor, a condenser, an
expansion device and an evaporator connected in series by
refrigerant flow lines; a heat recovery circuit having a heat
recovery heat exchanger, the heat recovery circuit being connected
to the cooling circuit so that the heat recovery heat exchanger is
in parallel with the condenser, and wherein the heat recovery heat
exchanger is in heat exchange relationship with a fluid to be
heated based upon an end-user demand for heat; and a control unit
programmed to selectively flow refrigerant through the condenser of
the cooling circuit and the heat recovery heat exchanger of the
heat recovery circuit so as to maintain temperature of the fluid
within a temperature band around a set point provided by the end
user.
7. The system of claim 1, further comprising at least one charge
recovery flow line connected from at least one of the condenser and
the heat recovery heat exchanger to the evaporator.
8. The system of claim 7, wherein the control unit is further
programmed to selectively flow refrigerant through one of the
condenser and the heat recovery heat exchanger, and to recover
charge from the other of the condenser and the heat recovery heat
exchanger through the at least one charge recovery flow line.
Description
CROSS REFERENCE TO PROVISIONAL APPLICATION
[0001] This application claims the benefit of the filing date of
co-pending and commonly owned provisional application Ser. No.
60/615,440, filed Sep. 30, 2004.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a refrigeration system and method
for providing heat recovery on a flexible basis as desired by the
end-user.
[0003] Cooling circuits of refrigeration units frequently include
heat recovery units which allow heat from refrigerant discharged by
the compressor to be used for heating other fluids. One example of
use of this type of system would be in heating water for satisfying
the hot water requirements of a building. This advantageously
allows the use of such heat to satisfy other energy needs.
[0004] The needs of various different buildings or other end-users
in connection with the amount of heat provided to other fluids from
the refrigerant circuit can vary substantially from end-user to
end-user, and further can vary significantly over time for any
end-user.
[0005] Unfortunately, refrigeration systems with heat recovery
circuits are not capable of providing sufficient flexibility to
meet the various demands of different end-users, and further the
time-changing demands of individual end-users.
[0006] It is the primary object of the present invention to provide
a system and method which address these needs.
[0007] Other objects and advantages of the present invention will
appear hereinbelow.
SUMMARY OF THE INVENTION
[0008] In accordance with the present invention, the foregoing
objects and advantages have been readily attained.
[0009] According to the invention, a method is provided for
providing controllable amounts of heat recovery from a refrigerant
circuit, which method comprises the steps of providing a cooling
circuit comprising a compressor, a condenser, an expansion device
and an evaporator connected in series by refrigerant flow lines;
providing a heat recovery circuit comprising a heat recovery heat
exchanger, the heat recovery circuit being connected to the cooling
circuit so that the heat recovery heat exchanger is in parallel
with the condenser, and the heat recovery heat exchanger being in
heat exchange relationship with a fluid to be heated based upon an
end-user demand for heat; and selectively flowing refrigerant
through the condenser of the cooling circuit and the heat recovery
heat exchanger of the heat recovery circuit so as to maintain
temperature of the fluid within a temperature band around a set
point provided by the end user.
[0010] In further accordance with the present invention, the system
may further comprise a plurality of cooling circuits and a
plurality of heat recovery circuits, and the selectively flowing
step may suitably comprise selectively flowing refrigerant through
heat recovery heat exchangers of one or more of the heat recovery
circuits.
[0011] The foregoing system and method allow flexible heating of
fluid with the heat recovery heat exchanger to satisfy different
and changing heat recovery needs of different end-users with a
single system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A detailed description of preferred embodiments of the
present invention follows, with reference to the attached drawings,
wherein:
[0013] FIG. 1 schematically illustrates a single circuit adapted
for cooling and heat reclaim operation according to the
invention;
[0014] FIG. 2 schematically illustrates a multiple-circuit system
embodiment according to the invention; and
[0015] FIG. 3 illustrates operation of a system in accordance with
the present invention to maintain temperature of a fluid within a
particular band utilizing the heat recovery operation of the system
of a present invention.
DETAILED DESCRIPTION
[0016] The invention relates to a refrigeration system which
includes at least one heat recovery circuit. The system can
selectively operate in a conventional cooling mode, and in heat
recovery mode to provide transfer of heat from heated refrigerant
fluid to a fluid which is desired to be heated. One example of such
a fluid is water to meet the hot water requirements of an end-user,
for example, the hot water requirements of a building. The system
of the present invention can be used to heat fluids such as this
water, and functions in such a way that widely varying needs can be
met with the same system. Specifically, the system can be used to
supply heated fluid at a broad range of different temperature
setpoints, and within a selectable range of the setpoint.
[0017] FIG. 1 shows a system 10 which includes refrigeration
circuit having a compressor 12, a condenser 14, an expansion device
16 and an evaporator 18. While the lines which connect these
various components will be further discussed below, it should be
readily appreciated that these components when operated in series
define a typical refrigeration circuit. Compressed refrigerant from
compressor 12 is sequentially passed through condenser 14 and
expansion device 16 to evaporator 18, wherein the refrigerant cools
a stream of air as desired. Refrigerant from evaporator 18 then
returns to compressor 12 to complete the circuit. The refrigerant
exiting the compressor has a temperature which is sufficiently high
that heat can be effectively transferred to other fluids, for
example to water which must be heated to a temperature sufficient
for meeting typical domestic, commercial or industrial hot water
needs.
[0018] FIG. 1 further shows a heat recovery heat exchanger 20 which
is positioned to receive refrigerant from system 10 and exchange
heat from the refrigerant to a separate stream of fluid (shown in
FIG. 2 which is described below) so as to heat this fluid as
desired. This fluid may be water for supplying the hot water needs
of a building, or any other fluid which can advantageously make use
of heat transferred to same from the refrigerant.
[0019] FIG. 1 also shows a control unit 22 which is adapted for
controlling the system 10 to operate in various different modes as
will be further discussed below.
[0020] In order to operate as desired in accordance with the
present invention, system 10 is controlled so as to flow
refrigerant from compressor 12 to either condenser 14 or heat
recovery heat exchanger 20. When refrigerant flows from compressor
12 to heat recovery heat exchanger 20, the high-temperature
refrigerant advantageously transfers heat through heat exchanger 20
to the fluid to be heated as desired.
[0021] A series of valves 24, 26, 28 and 30, are positioned along
lines of system 10 and operated by control unit 22 so as to direct
flow from compressor 12 to condenser 14 or heat recovery heat
exchanger 20, and also to direct flow from these components as
desired. Thus, flow from compressor 12 passes through a compressor
discharge line 32 to a first branch 34 which extends through valve
24 to condenser 14, and through a second branch 36 which extends
through valve 28 to heat recovery heat exchanger 20. From condenser
14, discharge goes through condenser discharge line 38 through a
first branch 40 which flows to expansion device 16, and a second
branch 42 which flows through valve 26 and line 44 to evaporator
18. Flow from evaporator 18 passes through line 46 to compressor
12.
[0022] FIG. 1 also shows check valves 54, 56, which advantageously
serve to maintain flow through the lines of system 10 as
desired.
[0023] Co-pending and commonly owned U.S. patent application Ser.
No. 10/957,181, filed Sep. 30, 2005, discloses a method of managing
refrigerant charge in a system such as that illustrated in FIG. 1,
and discloses methods whereby refrigerant charge stored in
whichever of condenser 14 and heat recovery heat exchanger 20 is
not currently active is used to help maintain a sub-cooling or
saturation temperature within a range or setpoint. This application
(Ser. No. 10/957,181) is incorporated herein, in its entirety, by
reference.
[0024] In cooling mode, the system is operated as described above,
with the valves set to operate without flow through heat recovery
heat exchanger 20. During this operation, while condenser 14 gives
off heat to an outside location as is well known, heat exchanger 20
stores charge and evaporator 18 cools a stream of air to be
conditioned as is well known.
[0025] In heat recovery mode, flow from compressor 12 passes
through line 36 to valve 28 which is open so that refrigerant
enters heat recovery heat exchanger 20. In heat exchanger 20,
refrigerant gives off heat to a fluid to be heated, for example
water. From heat exchanger 20, flow passes to a condenser discharge
line 48 and, from there, passes through line 52 to expansion device
16 and then to evaporator 18. A sensor 58 can advantageously be
positioned along the refrigerant lines, preferably just upstream of
evaporator 16, and is utilized to determine properties of the
refrigerant at that point.
[0026] Control unit 22 is operatively communicated with each of
valves 24, 26, 28 and 30, as well as sensor 58 and advantageously
expansion device 16, as shown by the dashed lines in FIG. 1.
Control unit 22 is advantageously programmed to control the
position of the various valves discussed above based upon
information from sensor 58, and thereby to determine position of
the various valves so as to operate in cooling mode without the
heat recovery heat exchanger, or in heat recovery mode, and to
cycle between these modes as needed. According to the invention, by
cycling between cooling mode and heat recovery mode, a desired
amount of heat between 0 and 100% of the system capability can be
transferred to the fluid to be heated. In the embodiment of FIG. 2
to be discussed below, control unit 22 is preferably also utilized
and would be connected and programmed in similar manner to provide
desired amounts of heat recovery. In this embodiment, programming
of control unit 22 would preferably further include stepped or
otherwise controlled amounts of change in heat recovery mode. In
other words, control unit 22 in the embodiment of FIG. 2 could be
programmed to change or cycle one circuit at a time in order to
maintain a desired temperature of the heat receiving fluid.
[0027] Valves 26, 30 are used to selectively recover charge stored
in whichever one of condenser 14 and heat exchanger 20 is not
active. This charge can help to control the subcooling or
saturation temperature of refrigerant measured at sensor 58. When
charge is to be recovered from condenser 14, valve 26 is opened to
allow charge to flow through lines 42, 44 to evaporator 18, and
when charge is to be recovered from heat exchanger 20, valve 30 is
opened to allow charge to flow from heat exchanger 20 through line
50 to evaporator 18.
[0028] FIG. 2 shows a further system in accordance with the present
invention, with the additional showing being that two different
circuits 10A and 10B are provided, each of which selectively
communicate with evaporator 18 and heat recovery heat exchanger 20.
In this embodiment, circuits 10A and 10B flow to the same
evaporator 18 and the same heat recovery heat exchanger 20,
although other configurations are possible and well within the
broad scope of the present invention.
[0029] The system of FIG. 2 can be operated with circuits 10A, 10B
operated independently in similar fashion to the operation of the
system of FIG. 1. Each circuit 10A, 10B has the same type of
components as discussed above regarding FIG. 1. Thus, further
description of these components is not repeated here.
[0030] FIG. 2 shows heat recovery heat exchanger 20 with a heat
exchange line 60 which would carry the fluid to which heat is being
provided.
[0031] It should readily be appreciated that, depending upon the
needs of an end-user, the system of FIG. 2 can be operated with one
or both of the circuits in heat recovery mode, and that this will
serve to better provide the desired reclaim heat to the
end-user.
[0032] FIG. 3 shows an example of operation of the present
invention. As shown, an end-user would select a set point for
desired temperature of fluid to be treated using the heat recovery
heat exchanger. A reasonable tolerance is utilized to set a band
around the set point, and temperature measurements of the fluid are
made. FIG. 3 shows the change over time of the temperature in such
a system, and begins with the heat reclaim heat exchanger not in
use. As the temperature of the fluid (labeled "condenser water
temperature" in FIG. 3) gradually declines, it eventually hits the
lower threshold of the band around the set point. The system is
programmed such that, when the lower threshold is hit, valves are
controlled to operate at least one circuit in a heat recovery mode
to provide heat to the fluid and thereby keep the fluid temperature
within the band. FIG. 3 shows the temperature of the fluid
increasing accordingly after operation in heat recovery mode. When
the temperature hits an upper threshold of the range surrounding
the set point, the compressor circuit which was being operated in
heat reclaim mode is switched off, and the temperature of the fluid
again drops.
[0033] This cycle is repeated, switching heat reclaim mode on when
the temperature reaches a lower threshold and switching heat
reclaim mode off when the temperature reaches a high level of the
band.
[0034] FIG. 3 shows a simple illustration for a system having only
one heat recovery heat exchanger. It should be appreciated that
with a multiple circuit system, different ranges within the broad
operating band could be adapted to trigger adding more circuits to
heat recovery mode and/or removing one of a plurality of circuits
operating in heat recovery mode so as to provide more flexibility
in maintaining the heated fluid temperature as desired.
[0035] In this regard, according to the invention, control unit 22
is programmed to operate the system in cooling and heat recovery or
reclaim modes, and suitable programming for a two circuit system is
described below. In this description, condenser 14 is referred to
as an air cooled condenser since the condenser is normally cooled
by outside air, and the heat recovery heat exchanger is referred to
as a water cooled condenser since this condenser is cooled by the
fluid to which heat is being transferred, which in one embodiment
is water.
[0036] The software or programming of control unit 22 controls the
changeover from operation in air cooled to reclaim or reclaim to
air cooled modes of operation. In air cooled operation, condenser
14 is considered active, as a major portion of refrigerant is
passed through same, and heat recovery heat exchanger 20 is
considered inactive, as refrigerant flows through this heat
exchanger only in incidental amounts, for example due to an
imperfect valve. The inverse of this definition also applies to use
of the term "active", that is, in heat reclaim mode the substantial
portion of refrigerant flows through heat recovery heat exchanger,
and only incidental amounts of refrigerant flow to condenser
14.
[0037] Changeover from reclaim to air cooled can be caused by: a
manual reclaim select change due to a local, remote or other
command on the unit. A changeover can also be caused by a heat
reclaim temperature change while reclaim has been selected.
According to the invention, an algorithm is provided for monitoring
the entering reclaim sensor temperature and comparing it with the
reclaim setpoint so as to determine if reclaim is active or
not.
[0038] If a reclaim function is currently active, or has been
selected, the reclaim shall become active when the entering reclaim
temperature comes below the reclaim setpoint.
[0039] Based on a difference between reclaim entering water
temperature and the reclaim setpoint, control unit 22 determines if
one or two circuits are required to provide heat reclaim capacity.
In this manner, control unit 22 maintains the temperature of fluid
as close as possible to the desired setpoint, and also avoids
frequent changing from air cooled to reclaim or reclaim to air
cooled cycles. Programming for control unit 22 can further be
illustrated with reference to the below table.
TABLE-US-00001 # of # of circ'ts reclaim circ'ts in in reclaim
hr_ewt select reclaim STATUS CHANGE -- no 0 -2 hr_ewt < rsp -
hr_deadb/2 yes -- +2 rsp - hr_deadb/2 < hr_ewt < yes 0 +1 rsp
- hr_deadb/4 rsp - hr_deadb/2 < hr_ewt < yes 1 Unchanged rsp
- hr_deadb/4 rsp - hr_deadb/4 < hr_ewt < 0 -- Unchanged rsp +
hr_deadb/4 rsp + hr_deadb/4 < hr_ewt < 0 1 Unchanged rsp +
hr_deadb/2 rsp + hr_deadb/4 < hr_ewt < 0 2 -1 rsp +
hr_deadb/2 hr_ewt > rsp + hr_deadb/2 0 -- -2
[0040] According to the invention, pumpdown sessions are
periodically utilized to recover refrigerant volumes stored in the
non-active heat exchanger. Further according to the invention, it
is preferred that both circuits shall not initiate a pumpdown
session at the same time. Each circuit therefore has its own
reclaim function, and the description below is applied for both
circuit.
[0041] For a change from non-reclaim to reclaim operation, the
following procedure is preferred:
[0042] Verify the circuit has run for more than 2 minutes in
cooling mode.
[0043] Turn on the reclaim condenser pump if reclaim select is
enabled.
[0044] Verify that condenser flow is established: if not after 1
minute delay has elapsed, reclaim operation shall be aborted and an
alarm shall be displayed.
[0045] Check whether reclaim water entering requires the circuit to
go to a heat reclaim session and whether the number of air cooled
to reclaim changeovers is not higher than 4 per hour and whether
the last changeover did not occur within a 7 minute delay.
[0046] Wait until saturated condensing temperature minus saturated
suction temperature is higher than 10.degree. F. (10.degree.
C.).
[0047] Start the air condenser pumpdown sequence by opening the
water condenser entering valve, and closing the air condenser valve
3 s later.
[0048] After a 1 minute duration or as soon as the subcooling is
greater than 13.degree. F., reclaim operation is effective.
[0049] For a change from reclaim to non-reclaim mode, changeover is
preferred according to the following procedure:
[0050] Start a water condenser pumpdown sequence by opening the air
condenser entering valve, and closing the water condenser valve 3 s
later.
[0051] If reclaim select is no longer active, turn off condenser
pump.
[0052] According to the invention, a function is preferably run,
for example at every 3 second interval, in order to adjust
subcooling correctly during reclaim operation (a longer interval is
not recommended).
[0053] During a heat recovery operation, too much charge (high
subcooling) can cause high a condensing temperature, and it is
necessary to inject gas into the air condenser by opening the
entering air condenser valve for example by opening the valve once,
for about 3 s, and repeating every 20 s.
[0054] During heat recovery operation, missing gas (refrigerant)
can cause poor heating performance and/or low subcooling. In order
to address this, gas is injected into the water condenser by
opening the leaving air condenser valve once, for about 3 s, every
20 s (This is an air condenser pumpdown as refrigerant is still
resident in the air condenser because its capacity is typically
larger than the reclaim condenser capacity). Such a pumpdown is
efficient only if the delta pressure between air and suction
pressure is correct. Gas injection should not be done if reclaim
water temperature is high or saturated condensing temperature is
not too high or superheat is not too low.
[0055] In this regard, the fluctuation or difference between the
high and low points of the range is dependent, among other things,
upon the power capacity of the fluid which is receiving the heat.
In other words, the more water which is passed through the heat
exchanger, the more gradual will be the change in temperature of
this water. Thus, an end-user can determine what level of stability
is desired in connection with the temperature of the outgoing
liquid, and can adjust the amount of water passing through the heat
reclaim heat exchanger based upon same. As one non-limiting
example, Table 1 below sets forth a series of different stabilities
along with volume of the water needed in connection with same.
TABLE-US-00002 Stability Volume 2.degree. C. 40 l/kW 3.degree. C.
30 l/kW 4.degree. C. 20 l/kW 5.degree. C. 15 l/kW
[0056] It should readily be appreciated that the system and method
of the present invention advantageously provides for extremely
flexible specification of heated fluid requirements of an
end-user.
[0057] It is to be understood that the invention is not limited to
the illustrations described and shown herein, which are deemed to
be merely illustrative of the best modes of carrying out the
invention, and which are susceptible of modification of form, size,
arrangement of parts and details of operation. The invention rather
is intended to encompass all such modifications which are within
its spirit and scope as defined by the claims.
* * * * *