U.S. patent application number 11/840544 was filed with the patent office on 2008-03-06 for heat pump.
Invention is credited to Hidefumi Araki, Takanori Shibata, Yasuo TAKAHASHI.
Application Number | 20080053127 11/840544 |
Document ID | / |
Family ID | 39149641 |
Filed Date | 2008-03-06 |
United States Patent
Application |
20080053127 |
Kind Code |
A1 |
TAKAHASHI; Yasuo ; et
al. |
March 6, 2008 |
HEAT PUMP
Abstract
A heat pump includes an evaporator 10 evaporating water; a steam
compressor 1 compressing the vapor generated by the evaporator 10;
a vapor supply duct 31 adapted to supply the vapor 30 compressed by
the compressor 1 to steam-utilizing facility 2; a measuring device
91 for measuring a state of vapor between the evaporator 10 and the
compressor 1; and a valve 81 adjusting an amount of vapor flowing
in the compressor 1 based on information from the measuring device
91.
Inventors: |
TAKAHASHI; Yasuo; (Mito,
JP) ; Shibata; Takanori; (Hitachinaka, JP) ;
Araki; Hidefumi; (Hitachi, JP) |
Correspondence
Address: |
MATTINGLY, STANGER, MALUR & BRUNDIDGE, P.C.
1800 DIAGONAL ROAD
SUITE 370
ALEXANDRIA
VA
22314
US
|
Family ID: |
39149641 |
Appl. No.: |
11/840544 |
Filed: |
August 17, 2007 |
Current U.S.
Class: |
62/238.7 ;
29/890.07; 62/528 |
Current CPC
Class: |
Y02P 80/15 20151101;
Y10T 29/49396 20150115; Y02P 80/154 20151101; F01K 3/006
20130101 |
Class at
Publication: |
062/238.7 ;
029/890.07; 062/528 |
International
Class: |
F25B 27/00 20060101
F25B027/00; B23P 17/00 20060101 B23P017/00; F25B 41/06 20060101
F25B041/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2006 |
JP |
2006-235868 |
Claims
1. A heat pump comprising: an evaporator evaporating water; a
compressor compressing the vapor generated by said evaporator; a
vapor supply duct adapted to supply the vapor compressed by said
compressor to a steam-utilizing facility; and means for adjusting
an amount of vapor flowing in said compressor.
2. A heat pump comprising: an evaporator evaporating water with
heat from a heat source; a compressor compressing the vapor
generated by said evaporator; a vapor supply duct adapted to supply
the vapor compressed by said compressor to a steam-utilizing
facility; and a bleed duct adapted to bleed vapor from said
compressor or from said vapor supply duct and lead the vapor to
said evaporator.
3. A heat pump comprising: an evaporator evaporating water through
heat exchange with exhaust heat; a compressor compressing the vapor
generated by said evaporator; a vapor supply duct adapted to supply
the vapor compressed by said compressor to a steam-utilizing
facility; a measuring device measuring a flow rate of vapor between
said evaporator and said compressor; a bleed duct adapted to bleed
vapor from said compressor or from said steam supply duct and lead
the vapor to said evaporator; a valve adjusting an amount of vapor
led to said evaporator through said bleed duct; and a controller
controlling said valve based on information from said measuring
device.
4. The heat pump according to claim 2, wherein said evaporator
internally includes a gas phase area and a liquid phase area, and
allows the vapor from said bleed duct to flow in said gas phase
area.
5. A heat pump comprising: an evaporator evaporating water through
heat exchange with exhaust heat; a compressor compressing the vapor
generated by said evaporator, said compressor including an inlet
guide vane; a vapor supply duct adapted to supply the vapor
compressed by said compressor to a steam-utilizing facility;
measuring means for measuring a state of vapor between said
evaporator and said compressor; and a controller controlling said
inlet guide vane based on information from said measuring
means.
6. The heat pump according to claim 1, further comprising means for
adjusting pressure and a flow rate of vapor after the compression
by said compressor and before the supply to said steam-utilizing
facility.
7. The heat pump according to claim 1, further comprising a storage
tank storing vapor after the compression by said compressor and
before the supply to said steam-utilizing facility.
8. A method of controlling a heat pump in which water is evaporated
in an evaporator through heat exchange with exhaust heat to
generate vapor, the vapor generated is increased in temperature and
in pressure by a compressor and the vapor increased in temperature
and in pressure is supplied to a steam-utilizing facility, the
method comprising the steps of: measuring a state quantity of the
vapor generated by said evaporator; bleeding the vapor during or
after the increase in pressure in said compressor in response to
the measuring result; and introducing to said evaporator the vapor
thus bled.
9. A method of controlling the heat pump of claim 5, wherein said
inlet guide vane provided for said compressor is controlled based
on the information from said measuring means.
10. A controller for a heat pump in which vapor generated by an
evaporator is compressed by a compressor and supplied to a
heat-utilizing facility, comprising: adjusting means for adjusting
a flow rate of vapor flowing in said compressor; wherein said
adjusting means is controlled based on the flow rate information of
the vapor flowing in said compressor.
11. A method of modifying a heat pump including an evaporator
evaporating water, a compressor compressing the vapor generated by
said evaporator, and a duct adapted to supply the vapor compressed
by said compressor to a steam-utilizing facility, the method
comprising the step of: additionally providing a bleed duct adapted
to bleed vapor from said compressor or the vapor supply duct and
lead the vapor to said evaporator, and a valve adapted to adjust an
amount of vapor led from said compressor or the vapor supply duct
to said evaporator.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a heat pump for supplying
vapor.
[0003] 2. Description of the Related Art
[0004] Operation control for a steam generator or boiler is
performed when steam is supplied to factories or the like.
JP-A-2002-195508 discloses such operation control, i.e., a
technique for controlling steam pressure and steam flow through
burn control of the boiler and a technique for maintaining a boiler
water level at a set value through feed pump control.
SUMMARY OF THE INVENTION
[0005] In a case where a heat pump provided with a steam compressor
is used to feed steam to factories, etc., control has not
sufficiently been studied for dealing with variations in production
of steam or a working medium resulting from temperature
fluctuations of the heat source of the heat pump.
[0006] It is an object of the present invention is to provide a
high-reliable heat pump that enables control for dealing with
variations in steam production resulting from temperature
fluctuations of exhaust heat which is a heat source.
[0007] To achieve the above object, there is provided a heat pump
including: an evaporator evaporating water; a steam compressor
compressing the vapor generated by the evaporator; a vapor supply
duct adapted to supply the vapor compressed by the steam compressor
to a steam-utilizing facility; and means for adjusting an amount of
vapor flowing in the compressor.
[0008] The present invention can provide a high-reliable heat pump
that enables control for dealing with variations in vapor
production resulting from temperature fluctuation of exhaust heat
which is a heat source.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a system configuration diagram of a heat pump
according to a first embodiment of the present invention.
[0010] FIG. 2 is a system configuration diagram of a heat pump
according to a second embodiment of the present invention.
[0011] FIG. 3 is a system configuration diagram of a heat pump
according to a third embodiment of the present invention.
[0012] FIG. 4 is a configuration diagram of an evaporator included
in the heat pump according to the third embodiment.
[0013] FIG. 5 is a partially enlarged view of a compressor of a
heat pump according to a fourth embodiment of the present
invention.
[0014] FIGS. 6A and 6B are partially enlarged views of the
compressor of the fourth embodiment.
[0015] FIGS. 7A and 7B indicate a pressure ratio vs. steam flow and
efficiency vs. pressure ratio of the compressor included in the
heat pump according to the fourth embodiment.
[0016] FIG. 8 is a system configuration diagram of a heat pump
according to a fifth embodiment of the present invention.
[0017] FIG. 9 is a system configuration diagram of a heat pump
according to a sixth embodiment of the present invention.
[0018] FIG. 10 is a system configuration diagram of a heat pump
according to a seventh embodiment of the present invention.
[0019] FIG. 11 is a system configuration diagram of a heat pump
according to a conventional example.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Nowadays, a steam generator or boiler is predominantly used
to supply steam to steam demanders such as paper factory and a
garbage and sewage plant. The steam supplied to factories or the
like has its clear usage in many cases, which requires installation
of a boiler that has specifications meeting desired steam pressure
and steam supply. A steam demander may request adjustable steam
supply in some cases; therefore, it is desirable that a boiler be
able to adjust the steam supply in the range of about .+-.20%.
[0021] A technique for controlling the pressure and flow of steam
produced by a boiler is known as a technique for meeting such
requirements. Examples of the control technique include a technique
for controlling burning of a boiler for such control and a
technique for controlling a feed pump for maintaining a boiler
water level at a set value.
[0022] In recent years, in view of effective utilization of energy,
it has been promoted to allow an exhaust heat recover system to
effectively utilize exhaust heat from factories, electric booster
stations, buildings and the like that was not effectively utilized
so much until now. One of the exhaust heat recovery systems is a
heat pump.
[0023] Under such background, the inventors have continued a study
of effectiveness with respect to use of a heat pump when steam is
supplied to a demander and acquired the following knowledge.
[0024] If a heat pump is used to supply steam to a steam demander,
use of a system as below is advantageous in terms of energy
efficiency. This system is provided with an evaporator that uses
water as a working medium and exhaust heat as a heat source. The
steam generated by the evaporator is increased in temperature and
in pressure by a compressor. The high-temperature and high-pressure
steam thus obtained is supplied to the demander. Use of water vapor
as the working fluid of the compressor provides an advantage that a
transferable energy amount per medium weight can dramatically be
increased as compared with use of other working fluids.
[0025] However, use of such a system needs to deal with the
following two problems: One of them is that the temperature of
exhaust heat currently wasted without effective use is as low as
about 80.degree. C. or lower. The other is that the temperature of
exhaust heat constantly fluctuates.
[0026] To deal with the first point, the inventors paid attention
to the following: A heat pump configured to generate steam by
allowing an evaporator to perform heat exchange between water and a
heat source can effectively take in heat from even a heat source
with lower temperature if the pressure of the working fluid is set
at low pressure. In particular, if the pressure of the steam
generated by the evaporator is set at negative pressure, exhaust
heat with a temperature lower than 100.degree. C. can effectively
be utilized. Specifically, as described in the following
embodiments, if the pressure of the steam generated by the
evaporator is set at 0.014 MPa, even a 60.degree. C.-exhaust heat
can sufficiently effectively utilized as a heat source.
[0027] The second point is next described. Temperature fluctuations
of exhaust heat which is a heat source lead to variations in the
quantity, pressure and temperature of the steam generated by the
evaporator. Incidentally, liquid is usually present in an
evaporator during steady operation and the relative humidity in the
evaporator is about 100% at all times. The pressure and temperature
of the steam generated by the evaporator have the relationship in
which if one of them is determined, the other is unambiguously
determined. The compressor is set so as to enable optimum operation
when working fluid has a certain given pressure and flow rate.
Therefore, the variations in steam amount and in steam pressure
degrade operability of the compressor. In addition, the variations
in steam amount and in steam pressure increase a risk of surging
occurrence, which deteriorates reliability of the compressor.
[0028] This problem is specific to the heat pump that uses exhaust
heat as a heat source. The steam boiler described above is operated
to supply steam, therefore, it is easy to exercise optimum control
for the steam flow and steam pressure in supplying steam. On the
other hand, if a heat pump is used, exhaust heat which is a heat
source is not heat generated for steam supply but heat generated by
another system. Since this heat is secondarily used, it is
difficult to control the temperature of exhaust heat along with the
operation of the heat pump.
[0029] The following embodiments describe configurations of the
heat pump for solving the secondary problem described above and the
function and effects thereof. The secondary problem is that in the
steam supply system using the heat pump, temperature variations of
the heat source deteriorate the reliability and operability of the
compressor. A heat pump in which water is used as a working medium
and the pressure of the steam generated by an evaporator is set at
a negative pressure is detailed below.
(Explanation of a Heat Pump)
[0030] A configuration of a heat pump is first described with
reference to FIG. 11. FIG. 11 is a system configuration diagram of
a heat pump which is a conventional example. The heat pump 200 of
FIG. 11 is configured such that it includes an evaporator which
uses exhaust heat as a heat source, vapor generated by the
evaporator is increased in temperature and in pressure by a
compressor, and the high-temperature and high-pressure vapor is
supplied to a demander. Specifically, the heat pump includes the
evaporator 10, a steam compressor 1 and an electric motor 16. The
evaporator 10 generates a saturate vapor 23 through heat exchange
between supply water 20 and exhaust heat 51 which is an external
heat source. The compressor 1 compresses the saturated vapor 23
generated. The electric motor 16 is coaxially connected through a
shaft 17 to the compressor 1 and to a gear 15 for driving the
compressor 1. The compressor 1 in this example is a four-stage
compressor composed of a first stage compressor 11, a second stage
compressor 12, a third stage compressor 13 and a fourth stage
compressor 14; however, the number of stages is not necessarily
four as long as its specifications meet a predetermined pressure
ratio. A plurality of compressors may be used instead of the
multi-stage compressor 1.
[0031] In the compressor 1, a portion of the supply water 20 is
supplied by the pump 50 to a humidification system 61 installed
between the first stage compressor and the second stage compressor
via a line 42, to a humidification system 62 installed between the
second stage compressor and the third stage compressor via a line
43, and to a humidification system 63 installed between the third
stage compressor and the fourth stage compressor via a line 44.
Water vapor which is the working fluid of the steam compressor 1 is
intermediate-cooled by the atomized water from each humidity
system. In addition, if the number of stages of the steam
compressor is different from that of this example, a humidity
system is installed between adjacent stages to intermediate-cool
vapor.
[0032] A description is made of flow of the working fluid in the
heat pump. The supplied water 20 is supplied as liquid water 21 in
a fluid state to the evaporator 10. The liquid water 21 is heated
in the evaporator 10 by the exhaust heat 51 which is an external
heat source such as factory exhaust heat or the like, and is
increased in temperature to a saturated temperature. A portion of
the liquid water 21 is evaporated into a vapor. The vapor generated
by the heat exchange flows as a saturated vapor 23 in the first
stage compressor 11 of the steam compressor 1. The saturated vapor
23 is increased in temperature and in pressure by the first stage
compressor 11 to become a high-temperature and high-pressure
superheated vapor 24. The superheated vapor 24 is humidified by the
humidification system 61 installed between the first stage
compressor 11 and the second stage compressor 12 to be cooled and
led to the second stage compressor 12. The vapor thus led is
compressed by the second stage compressor 12 to become a
high-temperature and high-pressure superheated vapor 26, which is
then humidified and cooled by the humidification system 62
installed between the second stage compressor 12 and the third
stage compressor 13. This vapor 27 is increased in temperature and
in pressure by the third stage compressor 13 to become a
superheated vapor 28, which is humidified and cooled by the
humidification system 63 installed between the third stage
condenser 13 and the fourth stage condenser 14. This vapor 29 is
further increased in temperature and in pressure by the fourth
stage compressor 14 to become a superheated vapor 30, which is
supplied through a steam supply duct 31 to a facility 2 such as
factories that need vapor.
[0033] A description is next made of the specific operation of the
heat pump paying attention to the state of the working fluid. The
supply water 20 that is to flow in the heat pump 200 enters the
evaporator 10 as about-15.degree. C.-liquid water 21. The
evaporation temperature of the evaporator 10 is set at 53.degree.
C. The liquid water 21 is heated by an about-60.degree. C.-external
high-temperature heat source 51 in the evaporator 10 to take
evaporation latent heat therefrom and phase-changes from a liquid
phase to a gas phase. The vapor generated in the evaporator 10 is
led to the steam compressor 1 as the saturated vapor 23 having a
saturated temperature of 53.degree. C. and a saturated vapor
pressure of 0.014 MPa. Mass flow of the saturated vapor 23 at this
time is about 1.2 kg/s. The saturated vapor 23 is increased in
pressure to a predetermined pressure ratio of about 2.4 by the
first stage compressor 11 of the steam pressure 1 and becomes the
superheated vapor 24 increased to a pressure of 0.034 MPa and to a
temperature of about 160.degree. C. at the outlet of the first
stage compressor 11. The superheated vapor 24 is sprayed with water
of about 0.05 kg/s by the humidification system 61 to lose
evaporation latent heat, cooled to about 72.degree. C. near
saturated vapor temperature, and enters the second stage compressor
12 at a mass flow of 1.25 kg/s. The vapor that has flowed in the
second stage compressor 12 is compressed to a predetermined
pressure ratio of about 2.2 to become the superheated vapor 26
increased in pressure to 0.074 MPa and in temperature to about
180.degree. C. The superheated vapor 26 is sprayed with water of
about 0.06 kg/s, cooled to about 91.degree. C. near the saturated
steam temperature, and enters the third stage compressor 13 at a
mass flow of 1.31 kg/s. This vapor is compressed in the third stage
compressor 13 to a predetermined pressure ratio of about 2.0 to
become the superheated vapor 28 increased in pressure to 0.15 MPa
and in temperature to about 190.degree. C. The superheated vapor 28
is sprayed with water of about 0.065 kg/s by the humidification
system 63, cooled to about 110.degree. C. near the saturated steam
temperature, and enters the fourth stage compressor 14 at a mass
flow of 1.38 kg/s. The vapor that entered the fourth stage
compressor 14 is compressed to a predetermined pressure ratio of
about 1.8 to become the superheated vapor 30 increased in pressure
to 0.27 MPa and in temperature to about 200.degree. C. This
superheated vapor 30 is supplied as an industrial heat source via
the vapor supply duct 31 to the facility 2 such as paper factories,
food factories, chemical factories and other factories that utilize
vapor.
[0034] Incidentally, the compressor is a machine that increases the
pressure of the working fluid sucked therein, and a ratio of
pressure before and after increased is called a pressure ratio. It
is assumed that the pressure ratio of the steam compressor 1 in the
present heat pump is about 19.
[0035] A system that generates vapor by means of a boiler in
supplying the vapor to the facility 2 that needs vapor is such that
most energy for generating vapor depends on thermal energy from
fuel charged. In contrast, the system that uses the heat pump of
each embodiment of the present invention can take in exhaust heat
wastefully released and the innumerable thermal energy of ambient
environment. Therefore, it is possible to dramatically increase
energy efficiency. In addition, the intermediate cooling is
performed in which the compressor working fluid is cooled between
the adjacent stages of the compressor. Therefore, the compressor
power can be reduced to increase the efficiency of the system.
[0036] A description is next made of an operational problem
encountered when the heat pump is used for steam supply.
[0037] The exhaust heat 51 which is the heat source of the
evaporator 10 has conventionally been wastefully released. The
temperature and flow rate of such exhaust heat 51 are not usually
constant, that is, fluctuate.
[0038] For example, about-15.degree. C. water may be supplied and
the exhaust heat 51 may be supplied as fluid to the evaporator 10
with an evaporation temperature of 53.degree. C. and with a
saturated steam pressure of 0.014 MPa. In this case, it is assumed
that an amount of heat that is supplied from the exhaust heat into
the system is reduced by 5% due to reductions in exhaust
temperature and in flow rate of the exhaust heat. Incidentally, the
reduction in the amount of heat corresponds to a reduction in
exhaust heat supply flow rate by 5% when it is assumed that the
exhaust heat supply temperature rate is constant. On the other
hand, it corresponds to a reduction in exhaust heat supply
temperature by about 0.5.degree. C. when it is assumed that the
exhaust heat supply flow rate is constant. In this case, the supply
water 21 obtains energy through heat exchange with the exhaust heat
51 in the evaporator 10. A portion of the supply water becomes a
saturated vapor at an evaporator temperature of 53.degree. C. This
saturated vapor has a pressure of 0.014 MPa and a temperature of
53.degree. C. In this case, the flow rate of the vapor generated in
the evaporator 10 reduces by about 5%. The reduction in the amount
of vapor generated in the evaporator 10 reduces the flow rate of
vapor flowing in the steam compressor 1. An inlet flow angle of the
vapor flowing in the compressor deviates, the performance of the
compressor degrades and a pressure ratio due to a reduction in
suction flow rate increases. Thus, the surge margin of the
compressor is likely to reduce. The surge margin refers to the
margin between a pressure ratio causing a surging phenomenon and a
pressure ratio of an actual operation point. The surging phenomenon
refers to a phenomenon in which as the pressure ratio rises,
pressure involving intense sound, intense flow pulsation and
mechanical vibration abruptly occur at a point where the pressure
ration is reached, which makes the operation of the compressor
unstable.
[0039] A reduction in flow rate of the steam flowing in the steam
compressor 1 increases the pressure ratio of the compressor. Since
the pressure of the vapor flowing in the compressor has a constant
saturated steam pressure, the increase in pressure ratio leads to
increases in pressure and in temperature of superheated vapors 24,
26, 28 at the respective outlets of the compressors. The
superheated vapors 24, 26 and 28 increased in temperature and
pressure are sprayed with the planned amount of water by the
humidification systems 61, 62 and 63, respectively. Since the
temperature of the superheated vapor is too high, it is unlikely to
provide sufficient intermediate cooling. If the sufficient
intermediate cooling is not provided, the power of the compressor
is increased, which leads to reduced efficiency of the system. In
addition, the vapor at the outlet of the steam compressor increases
in pressure and in temperature compared with the predetermined
vapor conditions, which may not meet the requested vapor
conditions.
[0040] As described above, the heat pump that uses an external heat
source such as the exhaust heat 51 requires the following: The
surge margin of the steam compressor 1 is ensured to enhance
reliability with respect to the fluctuations in the amount of vapor
generated in the evaporator 10 caused by the fluctuations of the
heat energy supplied from the exhaust heat 51 during the rated
operation. Degradation in the performance of the steam compressor 1
due to the fluctuations in the flow rate of vapor is suppressed.
The vapor of the desired conditions is supplied to the facility 2.
The heat pump of the present invention that meets the requirements
mentioned above will hereinafter be described in detail through
embodiments.
Embodiment 1
[0041] A first embodiment of the present invention is detailed with
reference to FIG. 1, which is a system configuration diagram of a
heat pump according to the first embodiment of the invention. For
simplification, the heat pump 100A of the embodiment is such that a
steam compressor 1 is a single stage compressor and intermediate
cooling is not performed.
[0042] A description is made of a problem of variation in vapor
flow rate of the heat pump due to the fluctuations of exhaust heat
and of a method of solving the problem with reference to FIG. 1.
Water 21 with a temperature of about 15.degree. C. is heated by
exhaust heat 51 in an evaporator 10 to generate a saturated vapor
23 with a temperature of 53.degree. C. and with a pressure of 0.014
MPa. If the fluctuations of the exhaust heat which is a heat source
reduce the amount of heat given to the water by the exhaust heat by
5%, however, the amount of vapor generated in the evaporator 10 is
reduced by 5%. This saturated steam 23 flows in the steam
compressor 1 and is compressed herein to become a saturated vapor
30. A portion of the saturated vapor 30 is led via a bleed duct 71
through the opening and closing of a valve 81 to the evaporator 10
by about 0.06 kg/s which corresponds to a difference between a
rated flow and an actual flow and is mixed with the saturated vapor
in the evaporator 10. The remainder of the superheated vapor 30 is
supplied to the facility 2 that needs vapor.
[0043] The flow rate of the superheated vapor led from the bleed
duct 71 to the evaporator 10 is controlled by a controller 120. The
controller 120 determines the flow rate of the superheated vapor to
be led from the bleed duct 71 to the evaporator 10 based on the
data of the flow rate and pressure of the vapor from a measuring
device 91 installed between the evaporator 10 and the steam
compressor 1. The valve 81 is controlled to control the amount of
superheated vapor to be led from the bleed duct 71 to the
evaporator 10 so that the flow rate and pressure of the vapor may
become respective desired values.
[0044] The present embodiment is configured as below. The pressure
and flow rate of the saturated vapor 23 flowing in the steam
compressor is measured and based on the measurement values, a
portion of the superheated vapor 30 increased in pressure in the
steam compressor 1 is led to the evaporator 10 by the control of
the valve 81 and mixed with the saturated vapor 23. Thus, the inlet
flow rate of the steam compressor 1 substantially becomes rated
flow. This can suppress the reduction of the surge margin caused by
increased pressure ratio due to reduction in the flow rate of the
working fluid of the compressor. In addition, since the compressor
can usually operate within the design point, also reduction in the
efficiency of the steam compressor resulting from the fluctuations
in flow rate, which can enhance the reliability of the operation of
the heat pump.
[0045] Since the present embodiment includes means for adjusting an
amount of vapor flowing in the compressor 1, the exhaust heat whose
temperature always fluctuates can effectively be utilized. In
addition, the present embodiment includes the bleed duct 71 which
bleeds vapor from the compressor 1 or the vapor supply duct 31.
Therefore, the amount of vapor to be generated by the evaporator 10
can be adjusted.
[0046] The present embodiment describes the function and effect of
the heat pump including the measuring device 91, the bleed duct 71
and the valve 81. However, a heat pump provided with the measuring
device 91 can easily be modified by additionally providing the
bleed duct 71 and the valve 81 as in the present embodiment,
thereby providing the same function and effects. It is preferred
that a controller connected to the valve 81 and to the measuring
device 91 be additionally provided or an existing controller be
connected to the valve 81 and to the measuring device 91.
[0047] In the present embodiment, the measuring device 91 capable
of detecting the flow rate and pressure of the saturated vapor 23
is installed between the steam compressor 1 and the evaporator 10.
This is because of the following: Since the flow rate of the vapor
flowing in the steam compressor 1 serves as an input signal used
for controlling an angle of a variable stator vane equipped in the
steam compressor and for controlling opening and closing of the
valve 81 for bleed vapor, it is necessary to measure the flow rate
of the vapor with as much accuracy as possible. It is conceivable
that the amount of vapor is estimated from measurement of
temperature of the exhaust heat 51 which is a heat source. In this
case, it is necessary to calculate the amount of vapor flowing in
the steam compressor 1 by adding thereto the superheated vapor bled
from the steam compressor 1 and led to the evaporator 10 via the
duct 71. In view of measurement accuracy, therefore, it is
preferable that the amount of vapor flowing in the steam compressor
1 be directly measured by a measuring device installed between the
steam compressor 1 and the evaporator 10. It is more desirable to
install the measuring device 91 outside than inside the evaporator
10 in order to eliminate the estimations of the amount of bled
vapor and mixture loss of the bled vapor. Taking into account the
pressure loss of a duct and the like, it is more desirable to
install the measuring device as closer as possible to the steam
compressor 1 than to the evaporator 10. Problems to be considered
when the measuring device 91 is installed are not only detection
accuracy but also, e.g., installation space and easiness of
installation. Therefore, the installation site of the measuring
device 91 is not limited to a site between the steam compressor 1
and the evaporator 10. Any place may be allowable as long as the
flow rate of the vapor 23 can be measured directly or indirectly
through calculation.
Embodiment 2
[0048] A second embodiment of the present invention is described
with reference to FIG. 2, which is a system configuration diagram
of a heat pump according to the second embodiment of the present
invention. A steam compressor 1 is of a four-stage configuration in
which a mainstream vapor is intermediate-cooled by humidification
systems 61, 62, 63 each provided between adjacent stages. A portion
of a superheated vapor 24 at an outlet of a first stage compressor
11 is led to an evaporator 10 through a bleed duct 72.
[0049] In the heat pump of the embodiment, when a measuring device
91 detects the flow rate and pressure of the saturated vapor 23
generated by the evaporator 10, if the saturated vapor 23 may not
meet rated flow, a controller 120 controls a valve 81 based on the
data from the measuring device so that a portion of the superheated
vapor 24 increased in pressure in the first stage 11 may be led
from a bleed duct 72 to the evaporator 10. The remainder of the
superheated vapor 24 is intermediate-cooled with water-spray by the
humidification system 61 and flows in the second stage 12. With
such a configuration, a reduction in the amount of vapor flowing in
the first stage compressor 11 can be suppressed, whereby the
reduction of the surge margin of the first stage compressor 11 can
be suppressed. However, since the portion of the superheated vapor
24 is led to the evaporator 10, the flow rate of vapor flowing in
the second stage compressor 12 is reduced to a level lower than
rated flow. The reduction in the flow rate of the vapor led to the
second stage compressor raises pressure ratios of the second stage
compressor 12 and of the subsequent stage compressors, which may
probably reduce the surge margin.
Embodiment 3
[0050] A third embodiment of the present invention is described
with reference to FIG. 3. This embodiment is different from the
second embodiment in that a bleed duct 73 communicating with an
evaporator 10 from an outlet of a fourth stage compressor 14 which
is a final stage compressor is provided as a system that extracts
vapor from the steam compressor 1 to the evaporator 10. The
embodiment is the same as the second embodiment in the other points
such as a point in which a controller 120 controls a valve 82 on
the basis of data from a measuring device 91.
[0051] As shown in FIG. 3, the present embodiment has a system that
leads a portion of the superheated vapor 30 flowing out from the
outlet of the fourth stage compressor 14 which is the final stage
compressor, to the evaporator 10 via a bleed duct 73. This makes it
possible that the flow rate of the full stages of the steam
compressor 1 is made substantially equal to a planned value. Thus,
the surge margin can be ensured over the full stages of the steam
compressor 1. The present embodiment describes the steam compressor
1 which is configured as a four-stage compressor including first
through four stage compressors. A steam compressor composed of a
plurality of stages is configured such that a portion of
superheated vapor is bled from the outlet of the final stage
compressor and led to the evaporator 10. This makes it possible to
operate the steam compressor with a high degree of reliability.
Incidentally, the usual steam boiler is operated with the pressure
of vapor to be supplied made constant. The heat pump of the present
embodiment can maintain the pressure of vapor to be supplied at a
predetermined pressure, therefore, it is possible to introduce the
heat pump as the substitute for a steam boiler.
[0052] FIG. 4 is an enlarged view of the evaporator 10 of the
present embodiment. A description is made of how to introduce a
bleed vapor from the steam compressor 1 through the bleed duct to
the evaporator 10 with reference to FIG. 4.
[0053] The water in the evaporator 10 is divided into a liquid
phase 102 and a gas phase 103. The water 21 is fed to the liquid
phase 102. A pipe line 52 adapted to obtain heat energy from the
exhaust heat 51 through heat exchange is arranged in the liquid
phase 102 so as to provide heat energy to the liquid phase 102. The
bleed duct 73 adapted to introduce bleed vapor from the steam
compressor is installed in the gas phase 103.
[0054] About 15.degree. C. water is supplied to the liquid phase
102 of the evaporator 10 kept at about 0.014 MPa which is saturated
vapor pressure and heated by the exhaust heat 51 to boil at an
evaporation temperature of 53.degree. C. The water changed into gas
evaporates as a saturated vapor 105. If the amount of heat supplied
from the exhaust heat 51 is reduced, the flow rate of the vapor
generated in the evaporator 10 is reduced. To compensate for the
reduction, a superheated vapor is led from the discharge side of
the steam compressor through the bleed duct 73 to the evaporator
10. The mixed vapor 23 of the superheated vapor and saturated vapor
105 flows in the steam compressor 1.
[0055] Incidentally, it is preferred that the superheated vapor led
to the evaporator through the bleed duct 73 be led to the gas phase
103. If the superheated vapor is supplied to the liquid phase 102,
it is condensed in the liquid phase 102 so that condensation latent
heat is used as energy to raise the temperature of the liquid phase
102. The energy of the bleed vapor is in minute amount relative to
the heat energy of the exhaust heat so that the amount of vapor
flowing into the steam compressor is not changed as such. Thus, it
is difficult to achieve the primary object of compensating for the
reduction in the flow rate of the vapor 23 by increasing the amount
of vapor. In the case where the superheated vapor is supplied to
the path between the outlet of the evaporator 10 and the steam
compressor 1, if a bleed vapor is simply led to the middle of the
duct, the temperature and velocity are likely to be nonuniform in
the duct, causing a pressure loss. To uniformly mix the bleed vapor
with the saturated vapor, it is necessary to additionally install a
device for promoting the mix in the vicinity of the introducing
portion, which makes the system complicate to increase cost.
[0056] The evaporator 10 of the present embodiment is configured to
supply a bleed vapor to the gas phase 103. This allows the
superheated vapor supplied via the bleed duct 73 to sufficiently
mix with the saturated vapor 105. Consequently, the mixed vapor 23
having relatively uniform temperature can be allowed to flow in the
steam compressor 1.
Embodiment 4
[0057] A fourth embodiment of the present invention is described
with reference to FIGS. 5, 6A, 6B, 7A and 7B. Unlike the above
embodiments, the present embodiment adopts a technology in which an
inlet guide vane is controlled to deal with variations in vapor
production in an evaporator 10 due to exhaust heat
fluctuations.
[0058] FIG. 5 is an enlarged view of a first stage compressor 11 of
a steam compressor according to the present embodiment. Referring
to FIG. 5, the first stage compressor 11 is configured to include a
rotary axis 64 and to allow vapor 60 which is working fluid to flow
in from the left side in the figure and flows out upward. As
described above, since the heat pump of the present embodiment uses
exhaust heat 51 as a heat source, the flow rate of the vapor 60
flowing in the steam compressor 1 varies due to fluctuations of the
exhaust heat 51. The present embodiment includes an inlet guide
vane 61 installed on the upstream side of a centrifugal compressor
impeller 62 in order to meet the performance of the steam
compressor in spite of the variations in vapor amount. The inlet
guide vane 61 is turnably installed. In response to the flow rate
of vapor detected on the downstream side of the evaporator 10, the
inlet guide vane 61 is turned to open or close the inlet path of
the compressor for controlling the amount of vapor flowing in the
steam compressor 1. In general, also an air compressor used in a
gas turbine is provided with an inlet guide vane. During the rated
operation of the gas turbine, the mass flow of air which is working
fluid of the compressor is substantially constant. Thus, the inlet
guide vane is hardly controlled at all during the rated operation.
The reason for use of the inlet guide vane is to ensure the
performance and surge margin of the compressor by following the
variations in flow rate encountered when the gas turbine is
started. Since the exhaust heat fluctuates even during the rated
operation of the steam compressor 1 in the present embodiment, the
flow rate of vapor flowing in the compressor is constantly detected
by a measuring device 91 and the inlet path is opened or closed in
response to the flow rate.
[0059] A description is next made of how the opening-closing of the
inlet path influences the flow of the working fluid to the
compressor impeller 62 with reference to FIGS. 6A and 6B. FIGS. 6A
and 6B illustrate a cross-sectional shape of the blade taken along
the dashed line 63 of FIG. 5. The impeller 62 rotates in the
direction of arrow 65 at circumferential velocity 97. The working
fluid 60 flows in the compressor impeller 62 in parallel to the
axial direction. The inlet guide vane 61 is also installed parallel
to the axial direction as shown in FIG. 6A. It is assumed that the
inlet guide vane 61 has a stagger angle of 0.degree. in this case.
If the stagger angle of the inlet guide vane 61 is 0.degree., a
triangle formed by velocity 98 (absolute velocity), as view from an
absolute field, of the working fluid flowing out from the inlet
guide vane and velocity 92 (relative velocity), as viewed from the
rotation field of the impeller), of the working fluid flowing in
the impeller 62 is called a velocity triangle. Incidentally, an
angle 93 formed between the absolute velocity and the relative
velocity corresponds to the inlet flow angle of the impeller.
[0060] In a state where the stagger angle of the inlet guide vane
61 is 0.degree., if the flow rate of vapor flowing in the
compressor reduces due to the exhaust heat fluctuations to reduce
the absolute velocity, the inlet flow angle 94 of the vapor flowing
in the impeller 62 increases. This deviation in the inlet flow
angle relative to the impeller 62 causes the higher pressure loss
of the impeller blade and the performance degradation of the
compressor. If the stagger angle 95 of the inlet guide vane 61 is
increased as shown in FIG. 6B, the vapor is turned at the outlet of
the inlet guide vane 61. Thus, the inlet flow angle 96 of the vapor
flowing in the impeller can be set substantially equally to the
inlet flow angle 93 for the rated flow. As a result, the reduction
in the higher pressure loss of the impeller blade 62 and the
degradation in the performance of the compressor can be suppressed.
If the inflow Mach number of the compressor impeller 62 is almost
equal to as high as supersonic, the stagger angle 95 of the inlet
guide vane 61 is increased to form a turning angle at an impeller
inlet. Thus, a high Mach number shock loss can be reduced to
improve compressor efficiency.
[0061] The effect of the inlet guide vane 61 is described with
reference to FIG. 7. FIG. 7A indicates a pressure ratio relative to
the vapor flow of the steam compressor 1 and FIG. 7B indicates
efficiency relative to the pressure ratio. Curves A, B and C in
FIGS. 7A and 7B indicate respective characteristics of the steam
compressor 1 for a certain vapor flow. Characteristic A indicates
the characteristic of the steam compressor 1 encountered when a
vapor amount is the rated flow. Point 200A on the characteristic A
indicates a rated flow, a rated pressure ratio and rated
efficiency. If exhaust heat fluctuations reduce vapor flow, an
operation point moves from 200A to 201A, in which the pressure
ratio rises and the efficiency is down. In this case, the inlet
guide vane 61 is turned to widen the inlet path, which changes the
characteristic of the compressor 1 from characteristic A to
characteristic C and the operation point moves from 201A to 200C.
The operation pressure ratio is substantially constant; therefore,
the optimum efficiency for the characteristic of the compressor 1
can be provided while increasing the flow rate of vapor flowing in
the compressor 1. Similarly, if exhaust heat fluctuations increase
vapor flow, an operation point moves from 200A to 203A, in which
the pressure ratio is down and the efficiency is down. In this
case, the inlet guide vane 61 is turned to narrow the inlet path,
which changes the characteristic of the compressor 1 from
characteristic A to characteristic B and the operation point moves
from 203A to 200B. The operation pressure ratio is substantially
constant, therefore, the optimum efficiency for the characteristic
of the compressor 1 can be provided while reducing the flow rate of
vapor flowing in the compressor 1.
[0062] The steam compressor 1 of the present embodiment needs to
consider both the increased and decreased flow rates of vapor due
to exhaust heat fluctuations. If an impeller is designed at a
design point where the inlet guide vane is disposed at the inlet of
the compressor, it is desirable, therefore, to design the impeller
in a state where the stagger angle of the inlet guide vane 61 is
not 0.degree.. That is to say, the stagger angle of the inlet guide
vane is set so that the vapor flow may not be maximized during the
steady operation. Even if the vapor amount generated in the
evaporator 10 is reduced due to the exhaust heat fluctuations or
the like, the amount of vapor flowing in the steam compressor is
increased by controlling the inlet guide vane 61. Thus, a heat pump
is provided that can stably supply steam to the facility 2.
[0063] Incidentally, the heat pump provided with the inlet guide
vane disposed at the inlet of the steam compressor according to the
present embodiment may be equipped with the bleed structure
described above in which the superheated vapor of the steam
compressor is supplied to the evaporator. With this configuration,
the higher reliable system can be operated that deals with the
fluctuations of the exhaust heat which is a heat source.
Embodiment 5
[0064] A fifth embodiment of the present invention is described
with reference to FIG. 8. FIG. 8 is a configuration diagram
illustrating a heat pump according to the fifth embodiment. It is
to be noted that like reference numerals designate the same or
corresponding parts as those shown in FIGS. 1 to 3 and 10 and
detailed explanation is omitted. The heat pump of the present
embodiment is different from that shown in FIG. 11 in that a
throttle valve 106 is provided in a line adapted to supply the
superheated vapor 30 flowing out from the fourth stage compressor
14 of the steam compressor 1 to the facility 2.
[0065] A feature of the heat pump according to the present
embodiment is described with reference to FIG. 8. If an amount of
vapor flowing in the steam compressor 1 is reduced due to exhaust
heat fluctuations for example, a pressure ratio is increased in the
compressor as shown in FIG. 7A. The saturated vapor pressure of the
evaporator 10 is constant, that is, not changed by the exhaust heat
fluctuations. The first stage compressor 11 has an inlet pressure
of 0.014 MPa. The pressure ratio at the inlet is constant and the
pressure ratios of the compressor stages are increased so that
pressure at the compressor outlet is raised. The reduction in flow
rate at each stage increases the pressure ratio so that the
discharge pressure at the fourth stage compressor 14 becomes a
level higher than a planned value. In contrast, the pressure of
vapor the facility 2 need is constant.
[0066] Since the present embodiment includes the throttle valve
106, the pressure of vapor supplied to the facility 2 can be kept
constant, thereby achieving stable supply of a superheated vapor.
Incidentally, also the heat pump of the present embodiment can
concurrently be provided with the above-described bleed structure
or the inlet guide vane.
Embodiment 6
[0067] A sixth embodiment of the present invention is described
with reference to FIG. 9. FIG. 9 is a configuration diagram
illustrating a heat pump according to the sixth embodiment. It is
to be noted that like reference numerals designate the same or
corresponding parts as those shown in FIGS. 1 to 3 and 10 and
detailed explanation is omitted. This embodiment is different from
that shown in FIG. 11 in that an accumulator 107 serving as a
storage tank is disposed in the middle of the line adapted to
supply to the facility 2 a superheated vapor 30 flowing out from a
fourth stage compressor 14 of the steam compressor 1.
[0068] The accumulator 107 is generally used in boiler
installations to store excess steam from a boiler during load
fluctuations and it is used for a sudden lack of steam. Similarly
to this concept, also the heat pump of the present invention can
use the vapor stored in the accumulator 107 for reduction in vapor
flow due to fluctuations of exhaust heat. In addition, the
accumulator 107 is used to suppress variations in pressure of the
vapor supplied to the facility 2. Also the heat pump of the present
embodiment can concurrently be equipped with the above-described
bleed structure or the inlet guide vane.
Embodiment 7
[0069] If the heat pump of the sixth embodiment is concurrently
equipped with the bleed structure described earlier, it
particularly produces a significant effect. A description is made
of a seventh embodiment in which the accumulator 107 of the sixth
embodiment is installed in the heat pump of the third embodiment
shown in FIG. 3. FIG. 10 is a configurational diagram illustrating
the heat pump of the present embodiment.
[0070] If the amount of vapor generated by the evaporator 10 is
reduced due to fluctuations of the exhaust heat 51, the controller
120 exercises control based on vapor flow information from the
measuring device 91 so that the bleed valve 81 is opened to lead a
portion of the superheated vapor 30 to the evaporator through the
bleed duct 73. In addition, the controller 120 exercises control so
that vapor is supplied from the accumulator 107 so as to compensate
for the reduction of vapor resulting from the bleeding of the
superheated vapor 30 supplied to the facility 2. The heat pump of
the present embodiment is configured in this way to use the vapor
stored in the accumulator 107 to compensate for the reduction of
the amount of vapor supplied to the facility 2 resulting from the
bleeding of vapor. Thus, the heat pump of the present embodiment
can stably supply a desired amount and pressure of vapor to the
facility 2 that requires vapor.
* * * * *