U.S. patent application number 13/886452 was filed with the patent office on 2013-11-28 for method and device for controlling operation of heat pump unit.
This patent application is currently assigned to MAYEKAWA MFG. CO., LTD.. The applicant listed for this patent is MAYEKAWA MFG. CO., LTD.. Invention is credited to Noriyuki ARATA, Shuji FUKANO, Takanori KUDO, Hisashi NAKAJIMA, Hiroshi USHIROKAWA.
Application Number | 20130312438 13/886452 |
Document ID | / |
Family ID | 46313385 |
Filed Date | 2013-11-28 |
United States Patent
Application |
20130312438 |
Kind Code |
A1 |
KUDO; Takanori ; et
al. |
November 28, 2013 |
METHOD AND DEVICE FOR CONTROLLING OPERATION OF HEAT PUMP UNIT
Abstract
The temperature of high-temperature water at the exit of a
condenser is maintained to be within a setting range by control of,
under an operation with all cylinders, capacity of a reciprocating
compressor in the period between a maximum allowable load and a
minimum load for lubrication, at which the flow of a lubrication
oil pump is ensured, based on the revolution-speed control of a
drive motor that drives the reciprocating compressor and by control
of the capacity of the reciprocating compressor at the minimum load
for lubrication or less based on the combination of the control of
decreasing the number of operation cylinders and the
revolution-speed control of the drive motor. In addition, a heating
mechanism is provided on an inlet path of the reciprocating
compressor to prevent the liquefied refrigeration flow of a
refrigerant liquid to the reciprocating compressor during the
operation or at the start.
Inventors: |
KUDO; Takanori; (Tokyo,
JP) ; ARATA; Noriyuki; (Tokyo, JP) ;
USHIROKAWA; Hiroshi; (Tokyo, JP) ; FUKANO; Shuji;
(Tokyo, JP) ; NAKAJIMA; Hisashi; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MAYEKAWA MFG. CO., LTD.; |
|
|
US |
|
|
Assignee: |
MAYEKAWA MFG. CO., LTD.
Tokyo
JP
|
Family ID: |
46313385 |
Appl. No.: |
13/886452 |
Filed: |
May 3, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/JP2010/073459 |
Dec 24, 2010 |
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13886452 |
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Current U.S.
Class: |
62/84 ;
62/129 |
Current CPC
Class: |
F25B 2339/047 20130101;
Y02B 30/741 20130101; F25B 31/002 20130101; F25B 2600/0253
20130101; F25B 25/005 20130101; F25B 49/022 20130101; F25B
2700/21173 20130101; F25B 1/02 20130101; F25B 2700/21161 20130101;
F25B 30/02 20130101; F25B 2500/16 20130101; Y02B 30/70 20130101;
F25B 2400/074 20130101 |
Class at
Publication: |
62/84 ;
62/129 |
International
Class: |
F25B 30/02 20060101
F25B030/02 |
Claims
1. A method for controlling an operation of a heat pump unit that
uses NH.sub.3 as a refrigerant, has a compressor, a condenser, an
expansion valve, and an evaporator, and constitutes a heat pump
cycle, the compressor being a reciprocating compressor having a
plurality of cylinders, a drive motor that drives pistons of the
cylinders, and also having a lubrication oil pump driven by the
drive motor, the method comprising: a first step of detecting
temperature of heat-exchanging fluid at an exit of the condenser or
the evaporator, the heat-exchanging fluid being heat-exchanged with
the NH.sub.3 refrigerant at the condenser or the evaporator; a
second step of maintaining the temperature of the heat-exchanging
fluid at the exit of the condenser or the evaporator to be within a
setting range by control of, under an operation with all the
cylinders, capacity of the reciprocating compressor in a period
between a maximum allowable load and a minimum load for
lubrication, at which a flow of a lubrication oil pump is capable
of being ensured, based on revolution-speed control of the drive
motor that drives the reciprocating compressor; and a third step of
maintaining the temperature of the heat-exchanging fluid at the
exit of the condenser or the evaporator to be within the setting
range by control of the capacity of the reciprocating compressor at
the minimum load for lubrication or less based on a combination of
control of decreasing the number of operation cylinders and the
revolution-speed control of the drive motor.
2. The method for controlling the operation of the heat pump unit
according to claim 1, comprising: a fourth step of maintaining the
NH.sub.3 refrigerant flowing into a refrigerant inlet path at
temperature not less than a saturation temperature by a heating
mechanism provided on the refrigerant inlet path of the
reciprocating compressor in order to prevent liquefied
refrigeration flow of the NH.sub.3 refrigerant to the reciprocating
compressor.
3. The method for controlling the operation of the heat pump unit
according to claim 1, wherein the inlet path is shut off at a stop
of the heat pump unit by a shut-off valve provided on the inlet
path of the reciprocating compressor in order to prevent the
liquefied refrigeration flow at a start of the reciprocating
compressor.
4. The method for controlling the operation of the heat pump unit
according to claim 1, comprising: a fifth step of making, at a stop
of the reciprocating compressor, pressure of high-pressure
refrigerant gas of an outlet path of the reciprocating compressor
equal to pressure on a side of the evaporator in order to prevent
liquefaction at a high-pressure part of the reciprocating
compressor.
5. The method for controlling the operation of the heat pump unit
according claim 1, comprising: a sixth step of making, at the start
of the reciprocating compressor, pressure of high-pressure
refrigerant gas of an outlet path of the reciprocating compressor
equal to pressure on a side of the evaporator in order to decrease
a start torque of the reciprocating compressor.
6. A unit for controlling an operation of a heat pump unit that
uses NH.sub.3 as a refrigerant, has a compressor, a condenser, an
expansion valve, and an evaporator, and constitutes a heat pump
cycle, the compressor being a reciprocating compressor having a
plurality of cylinders, a drive motor that drives pistons of the
cylinders, and also having a lubrication oil pump driven by the
drive motor, the heat pump unit comprising: a temperature sensor
that detects temperature of heat-exchanging fluid at an exit of the
condenser or the evaporator, the heat-exchanging fluid being
heat-exchanged with the NH.sub.3 refrigerant at the condenser or
the evaporator; and a controller that maintains the temperature of
the heat-exchanging fluid at the exit of the condenser or the
evaporator to be within a setting range by controlling capacity of
the reciprocating compressor in a period between a maximum
allowable load and a minimum load for lubrication, at which a
lubrication state of the reciprocating compressor is capable of
being ensured with a flow of the lubrication oil pump, based on
revolution-speed control of the drive motor that drives the
reciprocating compressor and by controlling the capacity of the
reciprocating compressor at the minimum load for lubrication or
less based on a combination of the revolution-speed control of the
drive motor and cylinder-number control.
7. The unit for controlling the operation of the heat pump unit
according to claim 6, wherein a heating mechanism is provided on a
refrigerant inlet path of the reciprocating compressor to maintain
the NH.sub.3 refrigerant flowing into the refrigerant inlet path at
temperature not less than saturation temperature thereby preventing
liquefied refrigeration flow of the NH.sub.3 refrigerant to the
reciprocating compressor.
8. The unit for controlling the operation of the heat pump unit
according to claim 7, wherein the heating mechanism is a heater
provided on the inlet path of the reciprocating compressor.
9. The unit for controlling the operation of the heat pump unit
according to claim 7, wherein the heating mechanism has the inlet
path of the reciprocating compressor formed into a dual-pipe
structure, introduces refrigerant gas outlet from the reciprocating
compressor or a refrigerant liquid on a side of the exit of the
condenser into an outer pipe of the dual-pipe structure, and heats
the inlet path with heat retained in the refrigerant gas or the
refrigerant liquid.
10. The unit for controlling the operation of the heat pump unit
according to claim 7, wherein the heating mechanism causes part of
refrigerant gas outlet from the reciprocating compressor to be
divided and poured into the inlet path thereby heating the inlet
path with heat retained in the refrigerant gas.
11. The unit for controlling the operation of the heat pump unit
according to claim 7, wherein the heating mechanism covers the
reciprocating compressor with a detachable heat-insulating
jacket.
12. The unit for controlling the operation of the heat pump unit
according to claim 6, wherein a pressure-equalizing mechanism is
provided that makes pressure of high-pressure refrigerant gas in an
outlet path of the reciprocating compressor equal to pressure on a
side of the evaporator at a stop or start of the reciprocating
compressor.
13. The unit for controlling the operation of the heat pump unit
according to claim 12, wherein the pressure-equalizing mechanism
has a heat exchanger provided on the outlet path of the
reciprocating compressor or the condenser, causes a cooling medium
to flow into the exchanger at the stop of the heat pump unit, and
condenses and liquefies the refrigerant gas to decrease the
pressure of the refrigerant gas of the outlet path.
14. The unit for controlling the operation of the heat pump unit
according to claim 6, wherein a second heat pump unit having a
heat-pump-cycle constituting apparatus is provided, the evaporator
is incorporated in a high-pressure side refrigerant path of the
second heat pump unit to be constituted as a cascade condenser that
uses heat retained in a refrigerant of the second heat pump unit as
a heat source, and pressure of the high-pressure side refrigerant
path of the second heat pump unit is regulated in order to maintain
the temperature of the heat-exchanging fluid at the exit of the
condenser to be within the setting range.
15. The unit for controlling the operation of the heat pump unit
according to claim 14, wherein a condensed refrigerant liquid of
the second heat pump unit is supercooled by the cascade condenser,
and the supercooled refrigerant liquid is caused to return to a
low-pressure side refrigerant circulation path of the second heat
pump unit.
16. The unit for controlling the operation of the heat pump unit
according to claim 14, wherein the cascade condenser is arranged in
parallel with a condenser of the second heat pump unit, and a flow
of the refrigerant of the condenser is regulated to regulate
condensing pressure of the condenser.
17. The unit for controlling the operation of the heat pump unit
according to claim 14, wherein the cascade condenser is arranged in
series between the condenser of the second heat pump unit and the
compressor, and either a flow of the refrigerant of the condenser
is regulated or condensing pressure of the condenser is regulated
by an outlet pressure regulation valve provided between the cascade
condenser and the condenser.
Description
TECHNICAL FIELD
[0001] The present invention relates to an operation control method
and an operation control unit that implement the stable supply of
high-temperature water or low-temperature water at desired
temperature by means of a heat pump unit that uses an NH.sub.3
refrigerant.
BACKGROUND ART
[0002] From the viewpoint of global environmental protection,
natural refrigerants having a small ozone depletion potential (ODP)
and a small global warming potential (GWP) have been conventionally
promoted as operation refrigerants for heat pump units instead of
chlorofluorocarbons. Since CO.sub.2 serving as a natural
refrigerant has a small ODP of 0 and a small GWP of 1, allows
high-temperature hot-water supply, and has high COP, it has been
practically used in hot-water supply machines for home and business
uses.
[0003] However, the CO.sub.2 refrigerant has higher pressure than
general refrigerants at ambient atmospheric temperature and thus
cannot be used in existing equipment. Therefore, equipment
supporting the pressure of CO.sub.2 is required to be newly
constructed besides a pipe system, which gives rise to the problem
that an equipment expense becomes high. In view of this, heat pump
units that use an NH.sub.3 refrigerant serving as a natural
refrigerant, having an ODP of 0 and a GWP of nearly equal to 0,
having high latent heat of evaporation, and having high cooling or
heating performance have been commercially available and
practically used as energy-saving alternate boiler functions for
producing high-temperature water. [0004] Patent Documents 1 and 2
disclose heat pump units that use an NH.sub.3 refrigerant. [0005]
Patent Document 1: Japanese Patent Application Laid-open No.
2008-255919 [0006] Patent Document 2: WO 2010/13590
[0007] High-temperature water produced by the heat pump unit is
used for heating, hot-water supply, industrial process heating,
washing, disinfection, snow melting, or the like. In such a use, an
operation for continuously supplying hot water at fixed temperature
is required. In addition, if the load is decreased, the temperature
of the water circulated from the side of the load is increased.
Therefore, the capacity control of the heat pump unit is required.
Moreover, the cooling or heating performance of the heat pump unit
becomes different depending on changes in the heat source and the
ambient temperature of the heat pump unit. Therefore, operation
control corresponding to such changes is required. In order to
continuously supply hot water at fixed temperature, the
proportional control of the capacity of a compressor is required
according to fluctuations in the load and the ambient
temperature.
[0008] Further, in order to produce high-temperature water at 50 to
100.degree. C., the pressure of the NH.sub.3 refrigerant exceeds
1.5 MPa on the low-pressure side and 5 MPa on the high-pressure
side of a heat pump cycle. Therefore, the pressure of the
refrigerant depends on fluctuation factors such as operation
conditions and ambient temperature, which gives rise to the problem
that the refrigerant-side surface temperature of an inlet pipe, the
compressor, and an outlet pipe at the stop and that of the inlet
pipe and the compressor during the operation fall below the
saturation temperature of the pressure of the NH.sub.3 refrigerant
gas to liquefy the NH.sub.3 refrigerant gas.
[0009] Furthermore, if the pressure of the NH.sub.3 refrigerant gas
of the inlet path of the compressor is increased, the temperature
of the inlet pipe cannot follow such an increase, which results in
the likelihood of the high-temperature NH.sub.3 refrigerant gas
being brought into contact with the inlet pipe and liquefied. In
case that the compressor sucks the liquefied refrigerant in, the
metal contact of a piston, a piston ring, or the like occurs, which
may cause damage on equipment and components.
DISCLOSURE OF THE INVENTION
[0010] In view of the problems of the related art, the present
invention has an object of allowing the supply of high-temperature
water or the like at desired temperature, e.g., at 50 to 90.degree.
C. at all times without degrading the COP regardless of
fluctuations in the load and the surrounding environment with a
heat pump unit that uses an NH.sub.3 refrigerant.
[0011] In addition, the present invention has a second object of
eliminating liquefied refrigeration flow to a compressor during an
operation or at the stop of the operation and preventing damage on
equipment, components, or the like constituting the compressor.
[0012] To this end, the present invention provides a method for
controlling an operation of a heat pump unit that uses NH.sub.3 as
a refrigerant, has a compressor, a condenser, an expansion valve,
and an evaporator, and constitutes a heat pump cycle. The method
includes a first step of detecting temperature of heat-exchanging
fluid at an exit of the condenser or the evaporator, the
heat-exchanging fluid being heat-exchanged with the NH.sub.3
refrigerant at the condenser or the evaporator; a second step of
maintaining the temperature of the heat-exchanging fluid at the
exit of the condenser or the evaporator to be within a setting
range by control of, under an operation with all the cylinders,
capacity of the reciprocating compressor in a period between a
maximum allowable load and a minimum load for lubrication, at which
a flow of a lubrication oil pump is capable of being ensured, based
on revolution-speed control of the drive motor that drives the
reciprocating compressor; and a third step of maintaining the
temperature of the heat-exchanging fluid at the exit of the
condenser or the evaporator to be within the setting range by
control of the capacity of the reciprocating compressor at the
minimum load for lubrication or less based on a combination of
control of decreasing the number of operation cylinders and the
revolution-speed control of the drive motor.
[0013] In the method of the present invention, the reciprocating
compressor, which is relatively less costly and whose capacity is
easily controlled, is used as a compressor. Further, while
detecting the temperature of the heat-exchanging fluid at the exit
of the condenser or the evaporator, the capacity of the
reciprocating compressor in the period between the maximum
allowable load and the minimum load for lubrication at which the
flow of the lubrication oil pump is capable of being ensured is
controlled based on the revolution-speed control of the drive motor
under the operation with all the cylinders. In addition, in the
case of such a load or less, the capacity is controlled based on
the combination of the cylinder-number control and the
revolution-speed control of the drive motor.
[0014] Thus, proportional control relative to the load is made
possible with the COP maintained at a high level. In addition, with
the proportional control relative to the load made possible, the
liquefaction of the refrigerant is prevented in the inlet pipe of
the compressor. Moreover, with the temperature of the
heat-exchanging fluid at the exit of the condenser or the
evaporator maintained so as to fall within the setting range, the
production of the heat-exchanging fluid at desired high or low
temperature is made possible.
[0015] Since the circulation amount of the refrigerant is decreased
with a decrease in the capacity of the compressor, there is room
for the evaporation performance of the evaporator. Therefore, the
evaporation temperature is increased, which results in an increase
in the inlet pressure. Because of this, the temperature of an inlet
pipe transitionally falls below the saturation temperature of the
NH.sub.3 refrigerant, which may cause NH.sub.3 refrigerant gas to
be condensed and liquefied.
[0016] In the method of the present invention, the NH.sub.3
refrigerant flowing into a refrigerant inlet path may be maintained
at temperature not less than saturation temperature by a heating
mechanism provided on the refrigerant inlet path of the
reciprocating compressor in order to prevent liquefied
refrigeration flow of the NH.sub.3 refrigerant to the reciprocating
compressor.
[0017] In this case, the heating mechanism may be operated in
advance before the control of decreasing the capacity of the
compressor. Thus, the liquefied refrigeration flow of the NH.sub.3
refrigerant to the compressor can be reliably prevented during the
operation or at the stop of the heat pump unit. Therefore, since
the lubrication of equipment and components constituting the
compressor can be satisfactorily ensured, the abnormal abrasion of
the sliding part of the compressor can be prevented.
[0018] In the method of the present invention, the inlet path may
be shut off at a stop of the heat pump unit by a shut-off valve
provided on the inlet path of the reciprocating compressor in order
to prevent the liquefied refrigeration flow at a start of the
reciprocating compressor. In a case in which the heat source of the
heat pump unit is different in various ways, the inlet path is shut
off by the shut-off valve if the temperature of the compressor is
low at the stop of the heat pump unit. Thus, the liquefied
refrigeration flow from the inlet path to the compressor is
prevented, whereby the foaming of lubricating oil and the abnormal
abrasion of the sliding part of the compressor can be reliably
prevented at the start of the compressor.
[0019] In the method of the present invention, the high-pressure
refrigerant gas of the outlet path of the reciprocating compressor
may be released to the side of the evaporator (low-pressure part)
having the inlet shut-off valve at the stop of the reciprocating
compressor to minimize the difference between the high pressure and
the low pressure of the reciprocating compressor and prevent the
liquefaction at the high-pressure part of the reciprocating
compressor. The high-pressure refrigerant gas of the outlet path is
released to the side of the low-pressure evaporator immediately
after the stop of the reciprocating compressor, whereby the
compressor outlet path side is cooled by ambient temperature and
the NH.sub.3 refrigerant inside a compression chamber is liquefied
and condensed. Therefore, the risk of damaging the inner equipment
of the reciprocating compressor can be reduced at the next
start.
[0020] In addition, in the method of the present invention, the
high-pressure refrigerant gas of the outlet path of the
reciprocating compressor may be released to the side of the
evaporator (low-pressure part) having the inlet shut-off valve at
the start of the reciprocating compressor to minimize the
difference between the high pressure and the low pressure of the
reciprocating compressor and decrease the start torque of the
reciprocating compressor. The smaller the pressure difference
between the inlet path and the outlet path at the start of the
compressor, the smaller the start torque of the drive motor of the
compressor is required. Therefore, the high pressure of the outlet
path of the compressor is made equal to pressure on the side of the
evaporator at the start of the compressor, whereby the start torque
of the drive motor can be decreased.
[0021] A unit for controlling an operation of a heat pump unit of
the present invention is directly applicable to the implementation
of the method of the present invention. The heat pump unit uses
NH.sub.3 as a refrigerant, has a compressor, a condenser, an
expansion valve, and an evaporator, and constitutes a heat pump
cycle, the compressor being a reciprocating compressor having a
plurality of cylinders, a drive motor that drives pistons of the
cylinders, and also having a lubrication oil pump driven by the
drive motor. The heat pump unit includes a temperature sensor that
detects temperature of heat-exchanging fluid at an exit of the
condenser or the evaporator, the heat-exchanging fluid being
heat-exchanged with the NH.sub.3 refrigerant at the condenser or
the evaporator; and a controller that maintains the temperature of
the heat-exchanging fluid at the exit of the condenser or the
evaporator to be within a setting range by controlling capacity of
the reciprocating compressor in a period between a maximum
allowable load and a minimum load for lubrication, at which a
lubrication state of the reciprocating compressor is capable of
being ensured with a flow of the lubrication oil pump, based on
revolution-speed control of the drive motor that drives the
reciprocating compressor and by controlling the capacity of the
reciprocating compressor at the minimum load for lubrication or
less based on a combination of the revolution-speed control of the
drive motor and cylinder-number control.
[0022] In the unit of the present invention, the reciprocating
compressor, which is relatively less costly and whose capacity is
easily controlled, is used as a compressor. While detecting the
temperature of the heat-exchanging fluid at the exit of the
condenser or the evaporator, the capacity of the reciprocating
compressor in the period between the maximum allowable load and the
minimum load for lubrication at which the flow of the lubrication
oil pump is capable of being ensured is controlled based on the
revolution-speed control of the drive motor under the operation
with all the cylinders. In addition, in the case of such a load or
less, the capacity is controlled based on the combination of the
cylinder-number control and the revolution-speed control of the
drive motor.
[0023] Thus, proportional control relative to the load is made
possible with the COP maintained at a high level. In addition, with
the proportional control relative to the load made possible, the
liquefaction of the refrigerant is prevented in the inlet pipe of
the compressor. Moreover, with the temperature of the
heat-exchanging fluid at the exit of the condenser or the
evaporator maintained so as to fall within the setting range, the
production of the heat-exchanging fluid at desired high or low
temperature is made possible.
[0024] In the unit of the present invention, a heating mechanism
may be provided on a refrigerant inlet path of the reciprocating
compressor to maintain the NH.sub.3 refrigerant flowing into the
refrigerant inlet path at temperature not less than saturation
temperature thereby preventing liquefied refrigeration flow of the
NH.sub.3 refrigerant to the reciprocating compressor. The NH.sub.3
refrigerant is maintained at the saturation temperature or more as
described above, thereby preventing the liquefaction of the
NH.sub.3 refrigerant. Thus, the liquefied refrigeration flow of the
NH.sub.3 refrigerant to the compressor can be reliably prevented
during the operation or at the stop of the heat pump unit.
Therefore, since the lubrication of equipment and components
constituting the compressor can be satisfactorily ensured, the
abnormal abrasion of the sliding part of the compressor can be
prevented.
[0025] In the unit of the present invention, the heating mechanism
may be a heater provided on the inlet path of the reciprocating
compressor. Thus, with a simple and low-cost configuration, the
liquefied refrigeration flow of the NH.sub.3 refrigerant to the
compressor can be reliably prevented.
[0026] The heating mechanism may have the inlet path of the
reciprocating compressor formed into a dual-pipe structure,
introduce refrigerant gas outlet from the reciprocating compressor
or a refrigerant liquid on a side of the exit of the condenser into
an outer pipe of the dual-pipe structure, and heat the inlet path
with heat retained in the refrigerant gas or the refrigerant
liquid. Thus, there is an advantage in that no special energy
source is required since the heat retained in the refrigerant is
used.
[0027] The heating mechanism may cause part of the refrigerant gas
outlet from the compressor to be divided and poured into the inlet
path thereby heating the inlet path with the heat retained in the
refrigerant gas. Since the sensible heat portion of the refrigerant
gas can be used for heating the inlet path, the heating efficiency
can be improved.
[0028] The heating mechanism may cover the compressor with a
detachable heat-insulating jacket. Thus, the installing
construction can be simplified and carried out at low cost.
[0029] In the unit of the present invention, a pressure-equalizing
mechanism may be provided that releases high-pressure gas in an
outlet path of the reciprocating compressor to a side of the
evaporator (low-pressure part) of the inlet shut-off valve at a
stop or start of the reciprocating compressor. The high-pressure
refrigerant gas of the outlet path is released to the side of the
low-pressure evaporator immediately after the stop of the
reciprocating compressor, whereby the high-pressure side of the
compressor is cooled by ambient temperature and the NH.sub.3
refrigerant on the inside is liquefied and condensed. Therefore,
the risk of damaging the inner equipment of the reciprocating
compressor can be reduced at the next start.
[0030] In addition, the high pressure of the outlet path is made
equal to low pressure on the side of the evaporator at the start of
the compressor, whereby the start torque of the drive motor can be
decreased at the start.
[0031] The pressure-equalizing mechanism may have a heat exchanger
provided on the outlet path of the reciprocating compressor or the
condenser, cause a cooling medium to flow into the exchanger at the
stop of the heat pump unit, and condense and liquefy the
refrigerant gas to decrease the pressure of the refrigerant gas of
the outlet path. Thus, the pressure difference between the inlet
path and the outlet path of the compressor can be reduced, and the
start torque of the drive motor of the compressor can be decreased.
Note that the refrigerant pressure of the outlet path can be
accurately regulated with the regulation of the temperature or the
flow of the cooling medium. Therefore, the pressure difference
between the inlet path and the outlet path can be accurately
regulated.
[0032] In the unit of the present invention, a second heat pump
unit having a heat-pump-cycle constituting apparatus may be
provided, the evaporator of the heat pump unit may be incorporated
in a high-pressure side refrigerant path of the second heat pump
unit to be constituted as a cascade condenser that uses heat
retained in a refrigerant of the second heat pump unit as a heat
source, and pressure of the high-pressure side refrigerant path of
the second heat pump unit may be regulated in order to maintain the
temperature of the heat-exchanging fluid at the exit of the
condenser to be within the setting range. Thus, the heat-exchanging
fluid can be heated at high temperature, thereby making it possible
to respond to a demand by a requestor that requires the
heat-exchanging fluid at high temperature.
[0033] In addition, when the heat retained in the second heat pump
unit is used as a heat source, the condensing temperature of the
second heat pump unit becomes different depending on seasons, e.g.,
40.degree. C. in the summer and 15.degree. C. in the winter, which
greatly fluctuates the temperature of the heat source. If the
condensing temperature becomes 15.degree. C., the COP is reduced
and the amount of the drawn heat is decreased, which may not allow
the heat-exchanging fluid to be set at desired temperature.
Conversely, with the regulation of the pressure of the
high-pressure side refrigerant path of the second heat pump unit,
the heat-exchanging fluid can be regulated at setting
temperature.
[0034] Note that in the above configuration provided with the
second heat pump unit, a condensed refrigerant liquid of the second
heat pump unit may be supercooled by the cascade condenser, and the
supercooled refrigerant liquid may be caused to return to a
low-pressure side refrigerant circulation path of the second heat
pump unit. Thus, the refrigeration effect of the second heat pump
unit can be enhanced.
[0035] In addition, the cascade condenser may be arranged in
parallel with a condenser of the second heat pump unit, and a flow
of the refrigerant of the condenser may be regulated to regulate
condensing pressure of the condenser. Thus, in the summer, some of
the condensing load of the second heat pump unit is born and
lightened by the cascade condenser and the condensing temperature
of the refrigerant of the condenser of the second heat pump unit is
decreased, while the heat source of the cascade condenser is
ensured. As a result, it becomes possible to perform a
high-efficiency operation with improved COP. In the winter, the
condensing load of the second heat pump unit is decreased, and the
ratio of the amount of heat to be used as the heat source of the
cascade condenser is increased. As a result, it becomes possible to
perform the high-efficiency operation of the heat pump unit.
[0036] Accordingly, in a case in which the temperature of the
heat-exchanging fluid at the exit of the condenser is variably
controlled and operated so as to be increased in the heat pump
unit, the condensing load is controlled in parallel with the second
heat pump unit. Thus, the temperature of the condensed liquid
heat-exchanged with the cascade condenser is increased, which
facilitates the high-efficiency operation. With the planned control
of these operation conditions in the summer and the winter, the
total operation efficiencies of the heat pump unit and the second
heat pump unit can be optimized throughout the year. Thus, since
the temperature of the heat source corresponding to the initial
condensing pressure of the heat pump unit can be ensured, the
heat-exchanging fluid can be heated at the initial temperature.
[0037] In the above configuration, the cascade condenser may be
arranged in series between the condenser of the second heat pump
unit and the compressor, and either a flow of the refrigerant of
the condenser may be regulated or condensing pressure of the
condenser may be regulated by an outlet pressure regulation valve
provided between the cascade condenser and the condenser. Thus,
since the sensible heat portion besides the overheat portion of the
refrigerant of the second heat pump unit can be effectively used,
the heat source of the cascade condenser can be ensured even if the
capacity of the second heat pump unit is small. In addition, the
condensing pressure of the refrigerant gas of the second heat pump
unit is regulated by the outlet pressure regulation valve to
decrease the condensing temperature. Thus, the operation efficiency
of the second heat pump unit can be improved.
[0038] According to the present invention, there is provided a
method for controlling an operation of a heat pump unit that uses
NH.sub.3 as a refrigerant, has a compressor, a condenser, an
expansion valve, and an evaporator, and constitutes a heat pump
cycle. The method includes a first step of detecting temperature of
heat-exchanging fluid at an exit of the condenser or the
evaporator, the heat-exchanging fluid being heat-exchanged with the
NH.sub.3 refrigerant at the condenser or the evaporator; a second
step of maintaining the temperature of the heat-exchanging fluid at
the exit of the condenser or the evaporator so as to fall within a
setting range by control of, under an operation with all the
cylinders, capacity of the reciprocating compressor in a period
between a maximum allowable load and a minimum load for lubrication
at which a flow of the lubrication oil pump is capable of being
ensured based on revolution-speed control of the drive motor that
drives the reciprocating compressor; and a third step of
maintaining the temperature of the heat-exchanging fluid at the
exit of the condenser or the evaporator so as to fall within the
setting range by control of the capacity of the reciprocating
compressor at the minimum load for lubrication or less based on a
combination of control of decreasing the number of operation
cylinders and the revolution-speed control of the drive motor.
Therefore, it is possible to make proportional control relative to
the load while maintaining the high COP. Thus, it becomes possible
to produce the heat-exchanging fluid at desired temperature and
prevent the liquefaction of the refrigerant in the inlet pipe of
the compressor.
[0039] According to the present invention, there is provided a unit
for controlling an operation of a heat pump unit that uses NH.sub.3
as a refrigerant, has a compressor, a condenser, an expansion
valve, and an evaporator, and constitutes a heat pump cycle, the
compressor being a reciprocating compressor having a plurality of
cylinders, a drive motor that drives pistons of the cylinders, and
a lubrication oil pump driven by the drive motor. The heat pump
unit includes a temperature sensor that detects temperature of
heat-exchanging fluid at an exit of the condenser or the
evaporator, the heat-exchanging fluid being heat-exchanged with the
NH.sub.3 refrigerant at the condenser or the evaporator; and a
controller that maintains the temperature of the heat-exchanging
fluid at the exit of the condenser or the evaporator so as to fall
within a setting range by controlling capacity of the reciprocating
compressor in a period between a maximum allowable load and a
minimum load for lubrication at which a lubrication state of the
reciprocating compressor is capable of being ensured with a flow of
the lubrication oil pump based on revolution-speed control of the
drive motor that drives the reciprocating compressor and by
controlling the capacity of the reciprocating compressor at the
minimum load for lubrication or less based on a combination of the
revolution-speed control of the drive motor and cylinder-number
control. Therefore, it is possible to achieve the same function and
the effect as those achieved according to the method of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 is an entire configuration diagram of a heat pump
unit according to a first embodiment of the method and the unit of
the present invention;
[0041] FIG. 2 is an explanatory diagram showing a heating mechanism
provided on a compression inlet path in the first embodiment;
[0042] FIG. 3A is a diagram showing a method for controlling the
capacity of a compressor and shows a comparative example;
[0043] FIG. 3B is a diagram showing the method for controlling the
capacity of the compressor and shows the capacity control of the
first embodiment;
[0044] FIG. 3C is a diagram showing the method for controlling the
capacity of the compressor and shows exceptional capacity
control;
[0045] FIG. 4A is a diagram showing experimental data on the
following capability of the temperature of hot water relative to
the capacity control of the compressor;
[0046] FIG. 4B is a diagram showing experimental data on the
following capability of the temperature of hot water relative to
the capacity control of the compressor and shows the capacity
control of the present invention;
[0047] FIG. 5 is an explanatory diagram showing another heating
mechanism;
[0048] FIG. 6 is an explanatory diagram showing still another
heating mechanism;
[0049] FIG. 7 is an explanatory diagram showing still another
heating mechanism;
[0050] FIG. 8 is an entire configuration diagram of a heat pump
unit according to a second embodiment of the method and the unit of
the present invention; and
[0051] FIG. 9 is an entire configuration diagram of a heat pump
unit according to a third embodiment of the method and the unit of
the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0052] Hereinafter, the present invention will be described in
detail using embodiments shown in the figures. Note, however, that
the scope of the invention is not limited thereto by the sizes,
materials, shapes, relative arrangements, or the like of
constituents described in the embodiments unless otherwise
specifically described.
[0053] A description will be given of a first embodiment of the
method and the unit of the present invention based on FIGS. 1 and
2, FIGS. 3A to 3C, and FIGS. 4A and 4B. FIG. 1 shows a heat pump
unit 10A of the embodiment. The heat pump unit 10A is composed of a
high-pressure side heat pump unit 12 and a low-pressure side heat
pump unit 40 that use NH.sub.3 as a refrigerant. The type of the
refrigerant used in the low-pressure side heat pump unit 40 is not
particularly limited. The NH.sub.3 refrigerant may be used.
[0054] The high-pressure side heat pump unit 12 is configured to
have a multi-cylinder type reciprocating compressor 16, e.g., the
reciprocating compressor 16 having six cylinders, a condenser 18,
an expansion valve 20, and a cascade condenser 22 on refrigerant
circulation paths 14a to 14c through which the NH.sub.3 refrigerant
is circulated. The multi-cylinder type reciprocating compressor 16
has a drive motor 24, an inverter 26 that controls the number of
the revolutions of the drive motor 24, and a lubrication oil pump
28 that supplies lubricating oil o remaining in a crankcase 30 to
each equipment and component inside the compressor in conjunction
with the revolution of a crankshaft.
[0055] The low-pressure side heat pump unit 40 is configured to
have a compressor 44, a condenser 46, a receiver 48, an expansion
valve 50, and a surge drum 52 on refrigerant circulation paths 42a
to 42e. The type of the compressor 44 is not particularly limited.
In addition, the surge drum 52 and an evaporator 54 are connected
to each other by second refrigerant circulation paths 56a and 56b,
and a refrigerant liquid is circulated from the surge drum 52 to
the evaporator 54 by a liquid pump 58. The evaporator 54
incorporates a circulation pipe 60 through which cold water for
various cooling purposes or a cooling medium w produced by a
refrigerating unit (not shown) or the like is circulated, and the
cooling medium w is supplied to the evaporator 54. Heat is
exchanged between the refrigerant liquid and the cooling medium w
in the evaporator 54, and some of the refrigerant liquid is
returned to the surge drum 52 as refrigerant gas.
[0056] The refrigerant gas inside the surge drum 52 is supplied to
the compressor 44 for compression and then condensed by the
condenser 46. After being temporarily stored in the receiver 48,
some of the condensed refrigerant liquid r1 is gasified via the
expansion valve 50 and returned to the surge drum 52. Some of the
refrigerant gas, r2, which passes through the refrigerant
circulation path 42a, is introduced into the cascade condenser 22
of the high-pressure side heat pump unit 12 via a branch pipe 62a.
The cascade condenser 22 is connected to the refrigerant
circulation paths 42a to 42e so as to be in parallel with the
condenser 46.
[0057] The refrigerant gas r2 introduced into the cascade condenser
22 is indirectly head-exchanged with the NH.sub.3 refrigerant via
the pipe of the cascade condenser 22 and the heat transfers to the
NH.sub.3 refrigerant. The refrigerant liquefied in the cascade
condenser 22 is returned to the refrigerant circulation path 42d
via a branch pipe 62b. Note that the refrigerant circulation path
42a is provided with a flow regulation valve 64 upstream of the
condenser 46. By the regulation of the flow of the refrigerant gas
supplied to the condenser 46 with the flow regulation valve 64, the
condensing pressure of the refrigerant gas r2 supplied from the
branch pipe 62a to the cascade condenser 22 is regulated.
[0058] The gasified NH.sub.3 refrigerant heat-exchanged with the
refrigerant gas r2 in the cascade condenser 22 is supplied to the
multi-cylinder type reciprocating compressor 16 for compression and
then condensed by the condenser 18. The condenser 18 is connected
to a circulation path 34 for high-temperature water, and
high-temperature water is continuously circulated from a supply
destination A to the condenser 18. The NH.sub.3 refrigerant gas is
heat-exchanged with the high-temperature water for cooling and
condensing. The high-temperature water h heated at 50 to
100.degree. C. by the condenser 18 is supplied to the supply
destination A. At the supply destination A, the high-temperature
water h is used for heating, hot-water supply, a heat source for
industrial process, washing, disinfection, snow melting, or the
like.
[0059] The condensed NH.sub.3 refrigerant liquid is depressurized
by the expansion valve 20 and heat-exchanged with the refrigerant
gas r2 supplied from the low-pressure side heat pump unit 40 in the
cascade condenser 22 for gasification. On the exit side of the
circulation path 34 of the condenser 18, a temperature sensor 36
that detects the temperature of the high-temperature water h is
provided.
[0060] A controller 66 receives a detection value from the
temperature sensor 36. In addition, the controller 66 can control
the operation of the inlet valve of the reciprocating compressor 16
to control the number of operation cylinders and can control the
inverter 26 to control the speed of the revolutions of the
reciprocating compressor 16. Moreover, the controller 66 can
control a drive motor 45 of the compressor 44 via an inverter (not
shown) and can control the opening degrees of the expansion valves
20 and 50 and the flow regulation valve 64.
[0061] Further, a cooler 32 is provided on an outlet path 14b
between the multi-cylinder type reciprocating compressor 16 and the
condenser 18. Cooling water c is circulated inside the cooler 32,
and the NH.sub.3 refrigerant gas passing through the cooler 32 is
cooled by the cooling water c to depressurize the NH.sub.3
refrigerant gas.
[0062] Furthermore, as shown in FIG. 2, a heating mechanism 70A is
provided on the inlet path 14a of the reciprocating compressor 16.
In FIG. 2, the heating mechanism 70A is composed of an inlet pipe
constituting the inlet path 14a, a heat retaining member 702 that
includes a heater therein and covers the inlet pipe, a temperature
sensor 704 that detects the temperature of the inlet pipe, and a
temperature sensor 706 and a pressure sensor 708 that respectively
detect the temperature and the pressure of the NH.sub.3 refrigerant
gas flowing through the inlet pipe. Furthermore, the inlet pipe is
provided with a shut-off valve 72 that shuts off the inlet pipe at
the stop of the heat pump unit 10. The detection values of these
sensors are input to the controller 66, and the operation of the
shut-off valve 72 is controlled by the controller 66.
[0063] Under such a configuration, the heat pump unit 10A is
operated by the control of the speed of the revolutions of the
drive motor 24 and the number of the cylinders of the reciprocating
compressor 16 with the controller 66. As shown in FIG. 3A, if the
speed of the revolutions of the multi-cylinder type reciprocating
compressor 16 is fixed and the temperature of the high-temperature
water h detected by the temperature sensor 36 is controlled so as
to fall within a setting range based on only the cylinder-number
control, the capacity of the multi-cylinder type reciprocating
compressor 16 is controlled stepwise. For example, in a case in
which control is made so as to increase and decrease two of the
cylinders of the multi-cylinder type reciprocating compressor 16,
the multi-cylinder type reciprocating compressor 16 is controlled
stepwise so as to have a capacity of 100%, 67%, and 33%. In the
horizontal axis of FIGS. 3A to 3C, the performance of the
multi-cylinder type reciprocating compressor 16 under the maximum
allowable speed of the revolutions and an operation with all the
cylinders is set as 100%. In the vertical axis, the COP is set at 1
under a capacity of 100%.
[0064] As shown in FIG. 3A, if the detection value of the
temperature sensor 36 is controlled so as to fall within a setting
range based on only the cylinder-number control, the detection
value does not successfully fall within the setting range, which
may cause hunting. FIG. 3B shows the control method of the
embodiment in which the cylinder-number control and the
revolution-speed control are combined together. In a state in which
the compressor has a capacity of 100%, the speed of the revolutions
of the compressor is decreased. Then, the speed of the revolutions
of the compressor is decreased under the operation with all the
cylinders until the capacity corresponding to the minimum speed of
the revolutions at which the lubrication performance of the
reciprocating compressor 16 can be maintained by the lubrication
oil pump 28. In this manner, the capacity control is made. If the
capacity is further decreased, the number of the operation
cylinders is decreased to four but the speed of the revolutions of
each of the cylinders is increased instead. Since the COP of the
reciprocating compressor can be improved with low speed of the
revolutions, the reciprocating compressor is operated with low
speed of the revolutions as much as possible.
[0065] It is assumed that the maximum allowable speed of the
revolutions is set at 1500 rpm and the minimum speed of the
revolutions is set at 900 rpm under the operation with the six
cylinders. At this time, the maximum allowable speed of the
revolutions under the operation with four of the cylinders is set
to be less than the minimum speed of the revolutions by several
percents under the operation with the six cylinders, whereby the
capacity of the compressor can be continuously PID-controlled
regardless of a change in the number of the cylinders. The same
setting is also made when shifting from the operation with four of
the cylinders to the operation with two of the cylinders.
[0066] FIG. 3C shows the exceptional operation method of a case in
which a high-load operation is continued for a long period of time
due to a demand for hot water and a low-load operation is required
to be continued even if there is no demand for hot water. In this
case, the revolution-speed control is made during the operation
with the six cylinders, and the reciprocating compressor is
operated only with the minimum speed of the revolutions under the
operation with four of the cylinders and the operation with two of
the cylinders. Thus, it becomes possible to perform the operation
with high COP.
[0067] According to the embodiment, the temperature of the
high-temperature water h is detected by the temperature sensor 36,
and the speed of the revolutions and the number of the cylinders of
the reciprocating compressor 16 are controlled such that the
detected value falls within a setting range. In addition, during
the operation, the heating mechanism 70A is operated in advance so
as to prevent the NH.sub.3 refrigerant gas from being liquefied
according to fluctuations in the pressure of NH.sub.3 refrigerant
gas together with the detection of the temperature sensors 704 and
706 and the pressure sensor 708. At the start of the heat pump unit
10A, the heating mechanism 70A is also operated in advance to
perform temperature control. At the stop of the operation of the
heat pump unit 10A, the inlet path 14a is shut off by the shut-off
valve 72 to prevent liquefied refrigeration flow at the start. For
example, the liquefaction of the refrigerant on the side of the
reciprocating compressor 16 is prevented at the start if the
circulation of the cold water w serving as the heat source of the
evaporator 54 is not stopped due to a special reason on the side of
the refrigerant unit, the high-pressure side heat pump unit 12 is
stopped, and the temperature of the refrigerant is decreased from
the side of the evaporator 54.
[0068] Moreover, before the start of the reciprocating compressor
16, the cooler 32 is operated in advance to decrease the
refrigerant pressure of the outlet path 14b. Thus, the start torque
of the reciprocating compressor 16 can be decreased.
[0069] Further, by the control of the opening degree of the flow
regulation valve 64 with the controller 66, the condensing pressure
of the condenser 46 is regulated. Furthermore, by the control of
the condensing pressure of the refrigerant gas of the low-pressure
side heat pump unit 40 in the cascade condenser 22, the operation
conditions of the high-pressure side heat pump unit 12 required to
make the temperature of the high-temperature water h fall into a
setting range can be ensured.
[0070] FIGS. 4A and 4B show an operation example of a case in which
the control is made so as to increase and decrease two of the
cylinders in the reciprocating compressor having the six cylinders.
FIG. 4A shows an example as a comparative example in which only the
cylinder-number control is made, and FIG. 4B shows an example of
the embodiment in which the cylinder-number control and the
revolution-speed control are made in combination. The control is
targeted at the temperature of the hot water at the exit of the
condenser 18. In FIG. 4A, the performance of the reciprocating
compressor 16 changes stepwise relative to continuous changes in
the load of the supply destination A with time. The temperature of
the hot water at the exit fluctuates relative to a setting
temperature, which results in a deviation. In addition, hunting is
caused in the capacity of the reciprocating compressor 16 depending
on the amount of the load of the supply destination A.
[0071] In FIG. 4B, the performance of the reciprocating compressor
16 continuously follows continuous changes in the load of the
supply destination A with time, and the load of the supply
destination A and the performance of the compressor almost
correspond to each other. Therefore, there is almost no deviation
between the temperature of the hot water at the exit and the
setting temperature.
[0072] According to the embodiment, the capacity of the
reciprocating compressor 16 can be continuously PID-controlled
based on the combination of the revolution-speed control and the
cylinder-number control of the reciprocating compressor 16
according to changes in the load of the use destination A.
Therefore, the temperature of the high-temperature water h can be
caused to accurately fall into the setting range. Accordingly,
high-temperature water at 50 to 100.degree. can be continuously
supplied to the supply destination A at all times. In addition,
since the opening degree of the flow regulation valve 64 is
controlled by the controller 66 to regulate the condensing pressure
of the condenser 46 of the low-pressure side heat pump unit 40, the
operation of the high-pressure side heat pump unit 12 for adjusting
the temperature of the high-temperature water h to the setting
temperature can be facilitated.
[0073] Moreover, since the inlet path 14a of the reciprocating
compressor 16 is maintained at temperature not less than the
saturation temperature of the NH.sub.3 refrigerant by the heating
mechanism 70A during the operation or at the start, the NH.sub.3
refrigerant gas is not liquefied and the liquefied refrigeration
flow of the refrigerant liquid to the reciprocating compressor 16
is not caused. Thus, abnormal abrasion at the sliding part of the
compressor and the foaming of lubricating oil at the start of the
compressor can be prevented. Further, since the inlet pipe is shut
off by the shut-off valve 72 at the stop of the heat pump unit 10A,
the liquefied refrigeration flow is not caused even at the
stop.
[0074] Furthermore, since the cascade condenser 22 is arranged in
parallel with the condenser 46 of the low-pressure side heat pump
unit 40 and the flow of the refrigerant to be supplied to the
condenser 46 is regulated by the flow regulation valve 64, the
amount of the refrigerant gas to be supplied to the cascade
condenser 22 can be regulated by the flow regulation valve 64
regardless of changes in the operation conditions of the
low-pressure side heat pump unit 40. Therefore, in the summer, some
of the condensing load of the low-pressure side heat pump unit 40
is born and lightened by the cascade condenser 22 and the
condensing temperature of the refrigerant of the condenser 46 is
decreased while the heat source of the high-pressure side heat pump
unit 12 is ensured. Thus, it becomes possible to perform a
high-efficiency operation with improved COP.
[0075] In the winter, the condensing load of the low-pressure side
heat pump unit 40 is decreased by the high-pressure side heat pump
unit 12, and the ratio of the amount of heat to be used as the heat
source of the high-pressure side heat pump unit 12 out of the
amount of heat retained in the condensed refrigerant liquid of the
low-pressure side heat pump unit 40 is increased. Thus, it becomes
possible to perform the high-efficiency operation of the heat pump
unit 10.
[0076] Accordingly, in a case in which the temperature of the
NH.sub.3 refrigerant at the exit of the condenser 18 is variably
controlled and operated so as to be increased in the heat pump unit
12, the condensing load is controlled in parallel with the
low-pressure side heat pump unit 40. Thus, the temperature of the
condensed liquid of the low-pressure side heat pump unit 40
heat-exchanged with the cascade condenser 22 is increased, which
facilitates the high-efficiency operation. With the planned control
of these operation conditions in the summer and the winter, the
total operation efficiency of the heat pump unit 10 can be
optimized throughout the year. Thus, since the temperature of the
heat source corresponding to the initial condensing pressure of the
heat pump unit 10 can be ensured, the heat-receiving fluid can be
heated at the initial temperature.
[0077] Next, a description will be given of a modified example of
the heating mechanism 70A based on FIG. 5. A heating mechanism 70B
is structured so as to dualize an inlet pipe constituting the inlet
path 14a. That is, the inlet pipe is used as an inner pipe, an
outer pipe 712 is provided on the outside of the inner pipe, and
branch pipes 714a and 714b that connect the condenser 18 and the
outer pipe 712 to each other are provided. The branch pipe 714a is
provided with an opening and closing valve 716 controlled to be
opened and closed by the controller 66. Other configurations are
the same as those of the heating mechanism 70A.
[0078] In the heating mechanism 70B, the condensed refrigerant
liquid at high temperature is introduced from the condenser 18 into
the outer pipe 712 as required to heat the inlet pipe. Since the
heating mechanism 70B uses heat retained in the refrigerant liquid
as a heat source, there is an advantage in that no special energy
source is required. In addition, since the refrigerant liquid is
supercooled by heat exchange in the inlet path 14a, contribution is
made to an improvement in the COP of the heat pump unit 10A.
[0079] Next, a description will be given of still another modified
example of the heating mechanism 70A based on FIG. 6. A heating
mechanism 70C shown in FIG. 6 is provided with a bypass 718 that
connects the inlet path 14a and the outlet path 14b of the
reciprocating compressor 16 to each other, and the bypass 718 is
provided with an opening and closing valve 720 controlled to be
opened and closed by the controller 66. Other configurations are
the same as those of the heating mechanism 70A.
[0080] In the heating mechanism 70C, the opening and closing valve
720 is opened as required to introduce the outlet refrigerant gas
into the inlet path 14a to heat the inlet path 14a. Since the
heating mechanism 70C can use the sensible heat of the outlet
refrigerant gas as a heat source by directly introducing the outlet
refrigerant gas into the inlet path 14a, there is an advantage in
that the heating efficiency can be improved.
[0081] Note that this modified example may be configured such that
the bypass 718 is spirally arranged around the inlet path 14a, the
inlet path 14a is heated by the sensible heat of the outlet
refrigerant gas, and the heated outlet refrigerant gas is returned
to the outlet path 14b. Alternatively, the modified example may be
configured such that the inlet pipe is of the dual-pipe structure
as shown in FIG. 5, the bypass 718 is connected to the outer pipe
to introduce the outlet refrigerant gas to heat the inner pipe with
the sensible heat of the outlet refrigerant gas, and the heated
outlet refrigerant gas is returned to the outlet path 14b. Under
such configuration examples, the pressure of the refrigerant gas of
the outlet path 14b is required to be increased by .DELTA.P the
pressure loss caused when the refrigerant gas passes through the
bypass 718. To this end, a diaphragm is provided on the outlet path
14b downstream of the branch part of the bypass 718 to increase the
pressure of the outlet refrigerant gas, and a connection part for
the returned refrigerant gas is provided on the outlet path 14b
downstream of the diaphragm.
[0082] Next, a description will be given of still another modified
example of the heating mechanism 70A based on FIG. 7. A heating
mechanism 70D has a detachable heat-insulating jacket 722 that
covers all of a head cover 25, components 27 such as a compression
mechanism, pistons, and a cylinder sleeve, the lubrication oil pump
28, and the crankcase 30 each constituting the reciprocating
compressor 16; an oil heater 724 that humidifies lubricating oil
inside the crankcase 30; a temperature sensor 726 that detects the
temperature of a cylinder wall; a pressure sensor 728 that detects
the pressure of the inlet refrigerant gas; and a temperature sensor
730 that detects the temperature of the inlet refrigerant gas. The
detection values of these sensors are input to the controller 66.
In addition, the temperature sensor 706 and the pressure sensor 708
(not shown) that respectively detect the temperature and the
pressure of the refrigerant gas inside the inlet pipe are
provided.
[0083] According to the heating mechanism 70D, the reciprocating
compressor 16 can be entirely humidified with a simple and low-cost
unit. In addition, since the heat-insulating jacket 722 is
detachable, it may be installed as required and is thus easily
handled.
[0084] The heat-insulating jacket 722 entirely humidifies the
reciprocating compressor 16 to prevent the liquefaction of the
refrigerant gas inside the compressor with ambient temperature
after the reciprocating compressor is stopped. With the conduction
of heat from the lubricating oil o inside the crankcase 30
maintained at constant high temperature by the oil heater 724, by
means of the controller 66 the entire compressor including inner
equipment and the head cover 25 is maintained at temperature not
less than the saturation temperature of the pressure of the
refrigerant gas inside the compressor in the stopped state to
prevent the liquefaction of the refrigerant. Thus, a decrease in
hydraulic pressure due to the foaming of refrigerating-machine oil
at the normal start of the reciprocating compressor is prevented,
and damage on the components of the compressor due to the
interposition of the refrigerant liquid is prevented.
[0085] In the first embodiment, the number of the operation
cylinders includes but not limited to six, four, and two based on
the cylinder-number control of the reciprocating compressor 16 and
may include odd numbers or integers.
[0086] In the first embodiment, the heat source of the cascade
condenser 22 may include, besides the refrigerant liquid supplied
from the low-pressure side heat pump unit 40, the waste heat of
process fluid, hot water exhausted from a cooling tower, sewage
processing water, hot water exhausted from an air conditioner,
waste steam, or the like of an adjacent plant and natural heat
retained in hot-spring heat, lake water, river water, seawater,
groundwater, soil, outside air, or the like.
Second Embodiment
[0087] Next, a description will be given of a second embodiment of
the method and the unit of the present invention based on FIG. 8.
In a heat pump unit 10B of the embodiment, the outlet refrigerant
gas of the compressor 44 is directly introduced into the cascade
condenser 22 via the outlet path 42a by the low-pressure side heat
pump unit 40. In addition, the branch pipe 62b that returns the
heat-exchanged refrigerant from the cascade condenser 22 is
connected to the condenser 46. Moreover, the branch pipe 62b is
provided with an outlet pressure regulation valve 68 whose opening
degree is controlled by the controller 66. That is, the cascade
condenser 22 is arranged in series upstream of the condenser 46.
Other configurations are the same as those of the first
embodiment.
[0088] According to the embodiment, the cascade condenser 22 is
arranged in series upstream of the condenser 46. Therefore, even if
the capacity of the low-pressure side heat pump unit 40 is small,
performance for supplying a heat source to the high-pressure side
heat pump unit 12 besides the sensible heat portion of overheat
refrigerant gas can be sufficiently ensured. Accordingly, the
higher-temperature water h can be produced by the high-pressure
side heat pump unit 12. In addition, the condensing pressure of the
condenser 46 of the low-pressure side heat pump unit 40 is
regulated by the outlet pressure regulation valve 68 to decrease
the condensing pressure of the condenser 46. Thus, since the
condensing temperature is decreased, the COP of the low-pressure
side heat pump unit 40 can be improved.
Third Embodiment
[0089] Next, a description will be given of a second embodiment of
the method and the unit of the present invention based on FIG. 9.
In a heat pump unit 10C of the embodiment, the refrigerant gas
outlet from the compressor 44 is condensed by the condenser 46 and
then temporarily stored in the receiver 48. The refrigerant liquid
r1 stored in the receiver 48 is sent to the cascade condenser 22
via the refrigerant circulation path 42c and used as the heat
source of the high-pressure side heat pump unit 12. After being
used as the heat source in the cascade condenser 22, the
refrigerant liquid r1 is returned to the surge drum 52 via the
refrigerant circulation path 42d. Other configurations are the same
as those of the first embodiment.
[0090] Besides the function and the effect achieved according to
the first embodiment, the embodiment can enhance the refrigeration
effect of the low-pressure side heat pump unit 40 in a manner in
which the refrigerant liquid r1 is supercooled by the use of the
refrigerant liquid r1 condensed in the low-pressure side heat pump
unit 40 as the heat source of the high-pressure side heat pump unit
12.
[0091] Note that any of the first to third embodiments refers to a
case in which the high-temperature water h at desired temperature
is produced by the condenser 18, but the present invention is not
limited thereto and can also be applied to a case in which
low-temperature water at desired temperature or other
low-temperature refrigerants are produced by the evaporator 54.
INDUSTRIAL APPLICABILITY
[0092] According to the present invention, a heat pump unit that
uses an NH.sub.3 refrigerant can stably supply high-temperature
fluid or low-temperature fluid at desired temperature for various
purposes at all times without degrading the COP regardless of
fluctuations in the load and the surrounding environment.
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