Note: Descriptions are shown in the official language in which they were submitted.
WO 95/09335 217 2 8 4 3 PCT/US9-1/11116
APPARATUS FOR MAXIMIZING AIR CONDITIONINC~
AND/OR REFRIGERATION SYSTEM EFFICIENCY
1. Field of the Invention
This invention generally relates to the field of mechanical refrigeration and air
S conditioning and more particularly to improving efficiency of colllpression-type
refrigeration and air conditioning systems.
2. Background of the Invention
In the operation of commercial freezel~, refrigel~tol~, air conditioners and
other colllpression-type refrigeration systems, it is desirable to m~ximi7e refrigeration
capacity while minimi7.ing total energy con~ulllplion. Specifically, it is nPcçs~ry to
operate the systems at as low a collll)lession ratio as possible without the loss of
capacity that normally occurs when colllplessor colllplession ratios are reduce 1 This
is accomplished by ~uppressillg the formation of "flash gas". Flash gas is the
spontaneous fl~hing or boiling of liquid refrigerant res hing from pressure losses in
refrigeration system liquid refrigerant lines. Various techniques have been developed
to eli...i-~te flash gas. However, collvellLional m~-fhotlc for ~up~lessillg flash gas can
subst~nti~lly reduce system efficiency by increasing energy co~ ion.
Fig. 1 represents a conventional m~ch~nic~l refrigeration system of the type
- typically used in a supermarket freezer. Specifically, col.lples~or 10 colllpresses
refrigerant vapor and discharges it through line 20 into con~len~er 11. Con~1en~er 11
con~len~es the refrigerant vapors to the liquid state by removing heat aided by
circnl~ting fan 31. The liquid refrigerant next flows through line 21 into receiver 12.
From receiver 12, the liquid refrigerant flows through line 22 to counter-flow heat
exc}l~nger (not shown). After passing through exchanger 13, the refrigerant flows via
line 23 through thermostatic exran~ion valve 14. Valve 14 ~xp~n~ls the liquid
refrigerant to a lower pres~ule liquid which flows into and through evaporator 15
S~ E S~E~ (RU! E 26)
WO95/09335 2 ~ 7 2 8 4 3 PCT/US9-1/11116 1--
where it evaporates back into a vapor absorbing heat. Valve 14 is c- nn~cted to bulb
16 by capillary tube, 30. Bulb 16 throttles valve 14 to regulate te~ elaLules produced
in evaporator 15 by the flow of the refrigerant. Passing through evaporator 15, the
e~p~nded refrigerant absorbs heat relul ..;ng to the vapor state aided by circulating fan
32. The refrigerant vapor then returns to co~ ,lessor 10 through line 24.
In order to keep the refrigerant in a liquid state in the liquid line, the
refrigerant pr~s~ure is typically m~int~ined at a high level by keeping the refrigerant
temperature at condenser 11 at a i.~ini---~"" of approximately 95o F. This minim~lm
conde.n~ing ~elllpel~lulc; ",~inli.i,lc pressure levels in receiver 12 and thus the liquid
lines 22 and 23 above the flash or boiling point of the refrigerant. At 95 F.
condencing l~lllpe~ l~, this pl`eS~Illt; for example would be; 125 PSI for refrigerant
R12, 185 PSI for refrigerant R22 and 185 PSI for refrigerant ~502. These
temperature and ples~ul~ levels are snfflcient to ~upples~ flash gas formation in lines
22 and 23 but the coll~/elllional means of m~int~ining such levels by use of high
colllpressor discharge pleS~Illes limits system efficiency.
Various means are used to m~int~in the telll~lalure and pressure levels stated
above. For example, Fig. 1 shows a fan unit 31 connected to sensor 17 in line 21.
Controlled by sensor 17, fan unit 31 is r~;s~ol~si~e to contl~ncP.r telllpel~lure or
plt;s~ul~ and cycles on and off to regulate condenser heat ~licsir~tion. A plc;s~ule
le~pollsi~/e bypass valve 18 in con~1encer output line 21 is also used to m~int~in
pr~ure levels in receiver 12. Normally, valve 18 is set to enable a free flow ofrefrigerant from line 21a into line 21b. When the pl~iSult:; at the output line of
condencer 11 drops below a predetermined minimllm, valve 18 operates to permit
co~ re~sed refrigerant vapors from line 20 to flow through bypass line 20a into line
21b. The addition to vapor from line 20 into line 21b increases the pres~ure in
receiver 12, line 22 and line 23, thereby ~u~pres~ih~g flash gas.
The foregoing system elimin~tes flash gas, but is energy inefficient. First,
m~int~ining a 95~F. con~-n~er telllpel~lule limits colll~ressor capacity and increases
energy consu~ Lion. Although the 95 F. ~ el~Lule level m~int~in~ sufficient
WO 95/09335 217 2 ~ ~ 3 3 PCT/US94/11116
IJleS~ul`e to avoid flash gas, the r~s~ nt elevated pressure in the system produces a
back ~les~ule in the conden~er which increases compressor work load. The operation
of bypass valve 18 also increases back pl~S~Ulc in the conden~er. In addition, the
release of hot, co,ll~)lc~sed vapor from line 20 into line 21 by valve 18 increases the
S refrigerant specific heat in the receiver. The added heat necessitates yet a higher
pressure to control flash gas formation and reduces the cooling capacity of the
refrigerant, both of which reduce efflciency.
Another approach to ~u~Jles~ing flash gas has been to cool the liquid
refrigerant to a ~ ;lalule sulJ~ y below its boiling point. As shown in Fig.
1, a subcooler unit 40 has been used in line ~2 for this purpose. However, subcooler
unitsrequireadditional m~cl.i~.GJy andpower, increasing e4ui~lllentandoperating cost
and reducing oveMll operating efficiency.
Other methods for controlling the operation of refrigeration ~y~l~uls are
disclosed in US. Pat. Nos. 3,742,726 to F.ngli~h, 4,068,494 to Kramer, 3,589,140to Osborne and 3,988,9()4 to Ross. For example, Ross liscloses the use of an extra
colll~lessor to increase the pressure of gaseous refrigerant in the system. The high
plc;S~ure gaseous refrigerant is then used to force liquid refrigerant through various
parts of the system. However, each of these ~y~le~ls is complex and requires
extensive purchases of new equipment to retrofit t~ ting systems. The expenses
involved in the purchase and operation of these methods usually outweigh the savings
in power costs.
A more recent method of controlling the formation of flash gas in the iiquid
line was disclosed in US Pat. No. 4,599,873 by R. Hyde. This method involves theuse of a m~gnetic~lly coupled cellllifugal pump placed in the liquid line as seen in
Fig. 2. Fig. 2 shows a vapor line 114, a condenser 116, a fan unit 118, a liquid line
120, a receiver 122, a pump 124 and 125, a liquid line 126, a heat exchanger 128,
aliquidline 129, avalve 130, aline 131, acontrol 132, anevaporator 134, afanunit138, and a vapor line 140. The purpose of this method is to illl~)l.ve system
effiçi-~nf,y by allowing system condensing ~l~ssules and temp~ldlul~s to be reduced
WO 95/09335 PCT/US9 1/11116 ~
2172~3
as ambient tempel~lwes reduce. The cellllifugal pump 124 adds pl~;s~ule to the liquid
line 126 at the point where the liquid line exits from the Condens(~.r 116 or receiver
122 without the use of colllplessor horsepower. This method of using a ce~ irugal
pump to add plt;S~UIt; reduces the amount of flash gas that forms in the liquid line,
S but does not ~-,limin~te it altogether.
Purthermore, e~ ;on of the centrifugal pump curve in Fig. 3 shows that
as flow increases, the ples~ule added by the c~nl~irugal pump decreases. However,
as flow of refrigerant liquid through the liquid line increases the pres~ul~ drop in the
liquid line increases by the square of the velocity. This colllbination of effects as
shown in Fig. 4. causes the cellllirugal pump to only reduce the formation of flash
gas during certain low flow con-lition~, below point A in Fig. 4. As refrigerant flow
increases at high load Con~liti(m~ and the l,res~ule added by the centrifugal pump
decreases, the formation of flash gas begins to increase again and system capacity is
lost when it is needed most.
Ahother deficiency of the previously described centrifugal pumping method is
that the centrifugal pump is located within the liquid line itself. If the c~llllirugal
pump fails to operate L,ropelly for any reason, it becollles an obstruction to flow of
refrigerant liquid seriously i...lu;.;,~E the operation of the refrigeration system.
The most serious deficiency of the previously described centrifugal ~ulllping
method however, is caused by the state of the refrigerant at the outlet of the condenser
116 or receiver 122. The liquid refrigerant at this location in ~e system is commonly
at or very near the saturation point. Any vapor ~at forms at the inlet of the
cellllirugal pump due to incomplete conden~tion or slight drop in pr~ssule caused by
the pump suction or any other reason will cause the cellL.i[ugal pump to cavitate or
vapor lock and lose prime. This renders the cellllirugal pump ineffective until the
system is stopped and restarted again, and is very detrim~nt~l to pump life and
reliability. Due to the constantly varying conditions of operation of the refrigeration
system this can occur with great regularity.
Wo gs/09335 2 1 7 2 8 ~ 3 5 PCT/US94/11116
A further development pertaining the fields of mechanical air con-litinning and
refrigeration relating to system o~l;",i~i~lion is ~ close~l by U.S. Pat. No. 5,150,580
also by R. Hyde. This development, seen in Fig. 2., involves the transfer of some
small amount of liquid refrigerant from the outlet of the ce~ irugal pump 124 in the
S liquid line 126 to be injected via conduit 136 into the collll"~ssor discharge line 114
by means of the added prt;s~ure of the cellLIirugal pump 124 in the liquid line. The
purpose of injection this liquid into the discharge line is to desuperheat the compressor
discharge vapors before they reach the conden~çr to reduce condenser pressure and
thereby reduce the co",p,~ssor discharge ples~u,e. This development is said to
improve system efficiency at high ambient te",pe,~lu,es when air conditioning systems
work the hardest and system ples~u,es are the highest
Again, however, as system p,~s~ures increase and refrigerant flow rates
increase at higher loads, the increased flow rate of reffigerant causes more y~es~ùl~;
loss through the con-l~.ns~.r. However, this same increased flow rate causes less
ples~ule to be added to the liquid by the cel~l~irugal pump 124 in the liquid line 126.
Thus, less liquid is by~assed via conduit 136 into the colllplessor discharge line and
less superheat is ~li",in~l~l at the time when more reduction is needed. And at some
point the lJres~ule loss through the condenser is greater than the p,es~u,~ added by the
cel,LIirugal pump and the effect is lost entirely.
Obviously, there lel"aills a need to provide a stable pl~ iUIe increase in the
liquid line 126 to completely t~li---i-~5~1e the forrnation of flash gas, and likewise a
stable ~,es~u,e increase in the liquid injection line 136 to completely desuperheat the
co"~ essor discha,ge vapors if the i",l.,oYe,l-ent in system efficiency is to be realized
on a COQ~I~ull and reliable basis regardless of system configuration or refrigerant flow
rate or vapor content.
In addition, since the energy conmmrtion of the compressor reduces with a
reduction in con-le.n~ing ~"~pe~lu~e, and it is the object of the aforementi~nedtechnology to operate the system at as low a con~l~n~ing telllpt;l~lule/discharge
plessult; as possible, a further need exists to reduce con~1en~ing ~ el~lule~,
WO 95/0933!!i PCT/US9-1/11116
~72~3 6
particularly during times of high ambient tempeMtures. This has previously been
achieved by using a water cooled conc~Pn~-r in place of an air cooled condenser.Water cooled conden~Prs are much more expensive and weigh more than air cooled
condensers when used as original equipment. The use of water cooled condensers also
involves water tr~oAtmçnt and disposal concerns. These weight, cost and water quality
concerns are even more restricting when it is desired to exrhAnge air cooled
con-~çn~ers with water cooled condensers. There is a need then to develop a simple
and effective way to modify air cooled cont~en~çrs into water cooled condensers.
The objectives of the present invention are to:
1) Reliably and con~tAntly increase the ~ ;S:jUIe in the liquid line to ~Up~lt;Ss
the formation of flash gas without l)nnece~Arily IllAi~ \g a high system pressure,
and without the possibility of obstructing the flow of refrigerant through the liquid
line.
2) To reliably and constantly inject the correct amount of liquid into the
co""),essor discl~e line to IllAx;llli~P the heat L.~n~rel in the condenser.
3). To illlploYe the operating efficiency of coll,pression-type refrigeration and
air con~li1~oning ~y~Lellls in a con~L~ul, controlled and reliable basis regardless of
system configuration or refrigerant flow rate.
4). To ,.l~xil-.i,e the refrigeration capacity of refrigeration and air conditioning
systems in a con~L~Ill, controlled and reliable basis regardless of system configuration
or refrigerant flow rate.
5). To economically and con~LA~ y suyyless the formation of flash gas in
refrigeration and air conditioning systems without illlpAil ;.~g refrigeration capacity and
efficiency regardless of system configuration or refrigerant flow rate.
WO 95/09335 PCT/US9~/11116
~72~3
6). To economically and reliably modify air cooled cQnd~on~ers to achieve the
benefits of water cooled con-le.n~çrs without the high weight, cost and water quality
problems, thus reducing the con~on~ing telllpeldlure/compressor discharge pressure
during periods of high ambient lelll~e,dlules for the purpose of extenlling the benefits
of low head pres~ e operation.
7). To provide a way to inexpensively retrofit existing refrigeration systems
to attain the foregoing objects on a reliable and controllable basis regardless of the
system configuration or refrigerant flow rate.
8). To provide a method of dulo,~,AIic~lly reducing the flow rate of the
pulll~ g ~pald~US to match the refrigerant flow rate in large refrigeration or air
cl n~itioning systems that have some unloading capability to match the load.
9)Further, the previous objects must be met in a way that will not be
detrim~.n~l to the system in the event of failure of the installed pumping mechanism
or conden~er cooling mech~ni~m
9). Still further, the above objects must be reliably met regardless of the
presence of some vapor in the liquid at the inlet of the pumping arrangement since the
liquid is at or near saturation.
10). Moreover, the above objects must be met in a way that can be adjusted
to satisfy a majority of the wide range of system configurations found in the field.
This invention provides for the refrigeration or air conditioning system to be operated
in a way which "~ ";~.e~ energy efficiency and ~u~)p-~sses flash gas formation
regardless of system configuration or refrigerant flow rate.
This invention further provides for the modification of air cooled c-)nrlen~ers to
achieve the benefits of water cooled con~en~çrs without the weight, cost and water
quality co~ normally ~so~ d with water cooled conden~e.rs.
WO 95/09335 ............. . ' . PCT/US9~/11116 ~
~728~ 8
The foregoing and other objects, features, and advantages of the invention will
become more readily apparellt from the following description of a preferred
embodiment, which proceeds with reference to the figures.
3. S~mm~ry of the Invention
S The invention entails the use of a positive displacement pump magnetically
coupled to a drive motor located in a conduit arrangement that is parallel to the liquid
line of the refrigeration system as in Fig. S This parallel conduit arrangement also
inc~ e$ a pl`t;S`7ule reg~ ting valve that will regulate the amount of pl~7Ult; added
to the liquid line by the parallel pump and piping arrangement. In addition, a check
valve is located in the liquid line to ~ the ple,sule diflerelllial added to theliquid line. This parallel piping arrangement is desirable in order to allow a constant,
pre-d~L~ ed pres,ule to be added to the liquid line regardless of variations in flow
rate of the liquid refrigerant. In addition, the parallel piping arrangement allows the
system to operate without liquid line obstruction in the event of pump failure.
Fur~er, a pump is added to ~e liquid injection line that is connect~ between
the liquid line and the collll~ressor discharge line for the purpose of desuperheating the
compressor dischal~e vapors. This pump insures a constant flow of liquid refrigerant
to the coluyl~ssor disch~ge line to fully de-,u~ellleat the collll)ressor discllarge vapors.
The preferred method would entail the use of a positive displacement pump, but any
suitable ç,ulllyillg method can be used.
Also, the above pump can be controlled by a variable speed drive mech~nism
The variable speed drive mechanism is controlled by two (2) temperature sensors. One
temperature sensor is located on the condenser to sense ~ led temperature of therefrigerant in the condenser. The other l~n~pelalule sensor is located at the inlet of the
condenser d~wlls~ of the point of liquid injection into the compressor dischargeIine to sense amount of superheat in the discharge line. The speed of the pump
located in the liquid injection line is varied by the ~tt~checl variable speed drive by
means of the sensed Lt;lllpel~Lure differelltial to provide just the proper amount of
wo gs/09335 ~17 2 8 ~ 3 PCT/US94/11116
liquid injection into the discharge line to adequately desuperheat the compressor
discharge vapors for optimum heat transfer in the c5)nden~er regardless of the
refrigerant flow rate or amount of superheat present in the co~l~ylessor discharge
vapors.
S In addition, this invention entails the use of a precisely controlled ultrasonic fogger
to produce a regulated fine spray of water that evaporates quickly as it enters the
condenser entering air stream. The fine mist of water is controlled to reduce the
condenser entering air temperature by evaporation of the mist, and to wet the surface
of the condenser coil without producing any excess that would run off the conden~er.
The purpose of the mist is to lower the condenser entering air temperature to the wet
bulb tellly~ ule lller~y reducing the con-ien~ing temperature/l,les~ule of the system.
4. Description of the Drawings
Figure 1 is a schem~tic diagram of a typical refrigeration system, as previouslydescribed.
lS Figure 2 is a schematic diagram of a refrigeration system including the prior art as
previously described. including the liquid injection for de~ul)ellle~ g.
Figure 3 is a diagram of a typical ce,lllirugal pump curve showing yles~ul~ added vs.
flow rate.
Figure 4 is a diagram of yleS:,ule loss through a piping system vs. flow rate with the
cellllirugal pump curve superimposed over it.
Figure S is a schem~tic diagram of a refrigeration system inchlding the present
invenhon.
WO 95/09335 217 2 8 ~-~ PCT/US91/11116 1--
Figure 6 is a more ~Pt~ilecl diagram of the parallel piping arrangement with positive
displ~cernent pump, ~les~ule differential regulating valve and check valves of the
present invention.
Figure 7 is a more det~ile~ diagram of the preferred method of adding yle~sule to the
liquid injection line including tne optional ~,~;re,-ed control method.
Figure 8 is a diagram of the duplex l~u~lping arrangement used to match ch~ngin~refrigerant flow rate in larger systems with unloading capabilities.
Figure 9 is a diagram of the ultrasonic fogger arrangement in the condenser entering
air stream of a previously air cooled condenser.
Figure 10 is a blown up depiction of a l.rek~ d embodiment of the pump(s) of thepresent invention.
5. Detailed D~scli~lion of the Preferred Embodime~t
Referring now to Fig 5, a closed circuit co~ ession-type refrigeration system
includes a colllplessor 10, a condenser 11, an optional receiver 12, an expansion valve
14 and an evaporator 15 connPctPcl in series by conduits defining a closed-loop
refrigerant circuit. Refrigerant gas is compressed by compressor unit 10, and routed
through discharge line 20 into conden~er 11. A fan 31 facilitates heat rli~siration
from condenser 11. Another fan 32 aids evaporation of the liquid refrigerant in
evaporator 15. The colllpressor 10 receives warm refrigerant vapor at yles~,ule Pl and
colll~lesses and raises its ~res~uie to a higher ple~sure P2. The condenser cools the
col~ ;ss~d refrigerant gases and con~ n~es the gases to a liquid at a reduced ~les~ule
P3. From condenser 11, the liquefied refrige~nt flows through line 21 into receiver
12 in cases where there is Cu~ y a receiver in the system. If there is no receiver
in the system the con~3en~eA refrigerant flows directly into the liquid line 22.Receiver 12 in turn discharges liquid refrigerant into liquid line æ.
WO 95/09335 ~17 2 8 ~ 3 PCT/US9~11 1 1 16
11
Figure 6 shows a positive displ~ement pump 41, driven by electric motor 42
m~gn~tic~lly coupled to the pump head is positioned in conduit arr~ngemPnt 60
parallel to the liquid line 22 at the outlet of the receiver or con(len~er to p~ uli~e the
liquid refrigerant in the line to an increased pressure P4. This parallel piping- S arrangement 60 also inclu~es the pl~;S~iUle differential regulating valve 45 and a check
valve 46 arranged as shown in Fig. 6 to provide for a constant added pressure (P4 -
P3) regardless of refrigerant flow rate or vapor content. A check valve 47 is added
to the liquid line 22 to m~int~in the ples~ule differential between line 22 and line 23
(see FIG. 7). An adjustable ~les~ure regulating valve 45 can also be used to more
accurately match the ples~ul~; differential required or to f~cilit~te changes that may
be needed in the ~ S~iUIe dirr~r~ al added. The yres~ule dirrele~llial of the
regulating valve 45 (FIG. 6) determines the amount of ples~ule that is added to the
system. Dirrert;lll amounts of pres~ule can be added to the liquid line 22 as neceS~ry
for each difrelel~l system configuration by using dirrel~ l yl~ule dirrel~lllial valves
or by adjusting the valve to a specific ples~ule as n-~lecl. As the flow rate of the
system varies in conduit 22, more or less refrigerant flows through parallel conduit
22a (FIG. 6) and yres~ule regulating valve 45 so the refrigerant flow into and out of
the parallel piping all~lgelllent 60 always m~t~hçs the flow rate through conduit 22
and 23 and the pres~ul~ differential (P4 - P3) remains comlz...l
From parallel piping all~lgel~ent 60, the liquid refrigerant flows into the
liquid line 23 (FIG. 7). Some of the liquid refrigerant flows through conduit 25 and
through pump 43 into c~ lessor discharge line 20 to ~e~-.pe.l-t-~t the co,llylt;~sor
discharge vapor. Pr~rel~bly pump 43 would be a yOSiliVt; displ~cemt~.nt pump
controlled by variable speed drive 44. The speed of the pump is d~lerl,lined by the
tempeMture dirrt;l~lllial between the con~-n~ing l~lllpel~lule of the refrigerant in
contl~.n~er 11 as sensed by bulb 49 and the t~;lllpel~lule of the superheated refrigerant
in line 20 as sensed by bulb 48.
The rem~in(l~r of the liquid refrigeMnt from the paMllel piping arrangement
60 flows llllou~ll the line and through an optional c~,ulller-current heat exch~n~er (not
shown) to thermost~tic exp~n~ion valve 14. Thermostatic t~xp~n~ion valve 14 exp~n(l~
WO 95/09335 PCT/US9~/11116 1--
~28~3
12
the liquid refrigerant into evaporator 15 and reduces the refrigerant pres~u,e to near
P1. Refrigerant flow through valve 14 is controlled by temperature sensing bulb 16
positioned in line 24 at the output of evaporator 15. A capillary tube 30 connects
sensing bulb 16 to valve 14 to control the rate of refrigerant flow through valve 14
S to match the load at the evaporator 15. The expanded refrigerant passes through
evaporator 15 which, aided by fan 32, absorbs heat from the area being cooled. The
rxr~nd~A, warmed vapor is returned at ples~u-t; Pl through line 24 to colllp,essor 10,
and the cycle is repeated.
Pump 41 and pressul~e regulating piping arrangement 60 is preferably located
as close to leceiver 12 or the outlet of condenser 11 as possible, and may be easily
in~t~ll~ in existing systems without extensive purchases of new equipment. Pump
41 must be of sufflcient capacity to increase liquid refrigerant pressure P3 by
whatever p,es~u,e is necec~-y to elimin~te the formation of flash gas in the liquid line
23 (FIG. 7). The pump must also be capable of adding a Coh~l~ull plt;s~ule to the
liquid line regardless of the presence of some vapor in the incoming liquid refrigerant
in line 22. A positive displ~rement pump and pressure regulating valve located in a
parallel piping arrangement 60 most effectively, economically and reliably provides
this capability.
Pump 41 must also be capable of adding a co~ l pressure to the liquid line undercon-lition~ of variable refrigerant discharge rates from valve 14, including conditions
in which valve 14 is closed.
In systems where the refrigerant flow rate varies signifi~ntly~ the ~ùnlpillg
arrangement must be able to vary its flow rate by a similar amount. In these cases,
a duplex pumping arrangement, Figure 8, is used. The duplex pumping arrangement
2~ consists of two pumps piped in parallel each with either a single speed, two speed or
variable speed motor and a control mech~ni~m capable of adjusting the speed of one
or both pumps to match the flow rate of the refrigerant in the refrigeration circuit.
This duplex pumping arrangement is typically used in systems that have multiple
c.,lllyressors or coll,pre~ors with the capability of llnlo~ling to signifir~ntly reduce
I Wo ss/o933s ~ 1 7 2 S ~ 3 PCT I Sg4/~ 6
the refrigerant flow rate The duplex pumping arrangement controls tie into the system
controls to adjust the pump or pumps speed to match the compressor loading thereby
- ~c11ing the refrigerant flow rate
During the higher outside ambient temperature conditions, the ultrasonic fogger
S al)l)dldlus as shown in figure 9 would be activated by an adjustable l~11,pe1dture
control set to ambient te""~)elatu,e The fogger would reduce the condenser entering
air temperature of the conventional air cooled conden~r from the dry bulb
temperature to the wet bulb temperature to sim~ te the performance of an evapo,dLi~re
con-len~er. This reduction in entering air temperature would result in a loweredconden~ing ~e111pe1dlurt;/~les~u1e, thus reducing co.--p.essor energy co1~u-11~lion
during higher outside ambient conditions
Operation
Referring to Fig 5, co",p,essor 10 co",piesses the refrigerant vapor which
then passes through discharge line 20 to con-len~er ll. In the con-~enser ll, atpressure P2, heat is removed and the vapor is liquefied by use of ambient air orwater flow across the heat exchange.. At contlen~er ll, l~---pe-dlu-e and p.~ssll-e
levels are allowed to fl~ ct 1~t~ with ambient air tempe-dlu,c;s in an air-cooled system,
or with water te.. pe~dlures in a water-cooled system to a .. in;.. 1 conden~ing
pressure/le..1pe,~lu,~e that has previously been set at about 95 P. This previously set
minim11rn contlen~ing temperature has been neces~ y to prevent the formation of flash
gas in the liquid line 22. The previously set n.ini.. n. was n.~;nl;.in~l by reducing air
or water flow across the heat exchanger of conci~n~er l l to reduce heat transfer from
the con~enser. Further decreasing the con~ n~ing te,--~e,~lu-es increase system
efficiency in two ways: l) The lower ~)-es~u-e dir~.~1.Lial of the compressor lOincreases the col--E)-essor volumetric efficiency according to the formula Vc= 1 +C-
C*(VI/V2) where V~ is volumetric efficiency, C is the cl~ nce ratio of the
compressor, Vl is the specific volume of the refrigerant vapor at the beginning of
co,..~.ession~ V2 is the specific volume of the refrigerant vapor at the end of
WO 95/09335 PCT/US91tllll6 ~
~728~3
.
col"p,ession, and 2) The lower liquid refrigerant temperature at the outlet of the
condenser results in a greater cooling effect in the evaporator.
The negative effect of reducing condensing temperatures below this previously
set ..-i-~i...~.,.. has been the formation of flash gas in the liquid line 23 (FIG. 7), which
when passed through expansion valve 14 reduced the net refrigeration effect of the
evaporator 15. The net result was a reduction of energy consumption per unit time
by the compressor, but a ~im~llt~neous reduction capacity of the system causing an
increase in compressor run time resulting in no net energy savings.
When the refrigeration or air conditioning system is morlified with the present
invention as in Fig. 5, the .. ini.. --.. conden~ing temperature and pressure can be
reduced .~ignific~ntly without the loss of capacity mentioned above due to the pressure
added to the liquid line by the pump 41 and parallel piping arrangement. As the
ambient air e"lpe,alu,e or water temperature used to cool the condenser becomes
lower, the efficiency of the compressor improves, and the capacity of the evaporator
increases, since no flash gas has been allowed to form in the liquid line. This is most
beneficial with refrigeration systems that operate year around and can take advantage
of the cooler ambient te",pel~tures.
As ambient air ~ell,pe,alure or cooling water telllpelaLule increases the
con(len~ing lel"pe,~lule and prt;s~u,e of the refrigeration or air con(litioning system
also increases and efficiency is reduced. In order to im~luve efficiency at these
higher ambient con-lition~ when air conditioning and refrigeration systems are at or
near maximum capacity, liquid refrigerant is bypassed from the liquid line 23 (Fig.
7) into the colllplessor discharge line 20. Since there is some amount of p,es~u,e lost
as the refrigerant passes through the condenser 11, making cnnden~r exit pressure P3
lower than e"l~ ce pies~ule P2, a pump is needed to add enough pressule to insure
flow of liquid from the liquid line 23 intû the discharge line 20. The preferredmethod is to use a positive displ~cem~nt pump, driven by a variable speed drive,controlled by the lelllpelalul~ differential between the superhP~ted colllplessûr
discharge vapor tel~til~lure T2 and the conden~ing lel,lpe,alule T3. As the
~ WO 95/09335 PCT/US9~/11116
21~2~4~
temperature differential becomes greater, the variable speed drive would cause the
positive di~pl~rement pump to pump more liquid into the discharge line 20 to
decrease the superheat. When the superheat LG~ eldlule and the conden~inE
temperature were the same, the refrigerant vapor entering the c~ n-l-on~çr would be at
5 the saturation point and the speed of the positive displ~rem~nt pump would stabilize
to a pre-set speed to ~ the condition.
This method of superheat suppression insures that the refrigeMnt vapor is
entering the condenser at saturation res~ ing in the o~ulilllulll conditions for heat
ll~rel thereby ol)!i---i~i.-g the efficiency of the condçn~er. This portion of the
invention is most beneficial at higher ambient temperature.
In addition, a method of further i"lpruving air cooled con(~en~er efflciency at
higher ambient tempe,dLulGs is by the use of the previously described ultrasonic fogger
a~dlus to reduce the condenser entering air IGIll~eldlulG from dry bulb to wet bulb
temperature. The ultrasonic fogger appdldlus would dispense a controlled fog of 10
micron sized water particles into the entering air stream of the previously air cooled
con-l~n~er to sim~ te the performance of an G~oldlivG cnndçn~çr. The amount of
this fog would be varied with the condenser load, entering air temperature and/or wet
bulb depression to just dispense enough fog to saluldte the entering air stream. This
would achieve the benefits of reducing the elllGrillg air ~GlllpGldlulG from the dry bulb
lelllpeldture to the wet bulb temperature without the need for other water pumps,
drain pans, sumps, water tre~tmçnt or blowdown ~;ullGIllly associated with evaporative
con~l~n~çrs.
Referring to Figure 10, the pump(s) of the present invention con~istc of an
outer driving magnet 200, a stationary cup 201, and an O-ring seal 202. The pumpfurther includes an inner driven magnet 203, a rotor assembly 204 and vanes 205.The pump further includes an O-ring seal 206 and brass head 207.
Taken together, both parts of the invention i"lpro~e system performance and
~ffleit~ncy over the full range of operating contlition~ and lG"lpG,dtules.
WO9~/09335 2~ 728~3 PCT/US9~/11116 ~
16
The use of m~gnetically-coupled rotary-vane pumps as positive displacement
pumps for pumping refrigerants has been found to be startlingly effective and they
have been found to exhibit a surprisingly long life. Once the vanes are worn to the
extent that they are properly seated and sealed, subsequent wear is almost negligible.
S This discovery has resulted in very effective use of these m~gn~tic~lly-coupled rotary-
vane pumps as positive displacement pumps for ~u-l,phlg refrigerants in non-
compressor-type refrigeration cycles. This application is particularly effective when
a compressor-type refrigeration cycle (preferably with the help of the present
invention) is used to store refrigeration, for exarnple, in the form of ice, during low
energy cost periods and then the col~ s~or is turned off during peak energy costperiods. During the peak period, the magnetically-coupled rotary-vane pump of the
present invention (ideally the same pump used to increase the efficiency of the
co",l~re~sor cycle) is used to circulate the same refrigerant through the ice, through
the same conduits, and through the same cooling coils (ev~o.ator), to cool the
conditioned space during peak energy cost periods.
Another aspect of the present invention is the use of starting torque control
means for the positive displacement pump. Typically, when a positive displacement
pump is placed into the liquid line of an air conditioning or refrigeration system, the
electric motor driving it is energized when the compressor is energiæd. This creates
two problems when the pump head is full of refrigerant upon start-up, as it is
normally the case. First, excessive torque is required to bring the pump head up to
speed while it is adding pressure to the liquid. Second, the rapid acceleration of the
pump rotor will cause temporary, but signific7/nt, cavitation that may damage the
pump.
The solution to both problems is to ramp the motor and pump up to operating
speed slowly. This can be accomplished by using a device called a "soft starter".
This device will bring the motor up to full speed over a period of 1 or more seconds,
depending on its design.
WO 95109335 PCT/US9-1/llllG
~ ~172813
Upon normal start-up, a standard electric motor will go from O R.P.M. to its
full speed of 3450 R.P.M. in less than 1 second. This causes excessive torque
re~luire-lle lls and cavitation when such a motor is coupled to a positive displacement
pump that is full of a liquid near saturation. If the acceleration rate of the motor and
pump head is slowed down so that it comes up to speed in preferably between 2 and
8 seconds, for example, the excessive torque and cavitation problems are avoided.
The variation in start-up acceleration can be accomplished by several means:
1. using an induction coil in series with the electric motor, or 2. redecigning the
motor windings to give less start-up torque, therefore slower starting speed, or 3.
in~t~lling a separate "soft start" electronic component to a standard motor that varies
the voltage to the motor.
Having described and illustrated the principles of the invention in a preferred
embodiment thereof, is should be apparent that the invention can be modified slightly
in arrangement and detail without departing from such principles. In that regard, this
patent covers all modific~1ion~ and variations falling within the spirit and scope of the
following claims:
