CA1286750C - Automatic reset of chilled water setpoint temperature control - Google Patents
Automatic reset of chilled water setpoint temperature controlInfo
- Publication number
- CA1286750C CA1286750C CA000528339A CA528339A CA1286750C CA 1286750 C CA1286750 C CA 1286750C CA 000528339 A CA000528339 A CA 000528339A CA 528339 A CA528339 A CA 528339A CA 1286750 C CA1286750 C CA 1286750C
- Authority
- CA
- Canada
- Prior art keywords
- setpoint
- temperature
- leaving
- reset
- load
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
- F25B49/022—Compressor control arrangements
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B1/00—Compression machines, plants or systems with non-reversible cycle
- F25B1/04—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type
- F25B1/053—Compression machines, plants or systems with non-reversible cycle with compressor of rotary type of turbine type
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Devices That Are Associated With Refrigeration Equipment (AREA)
- Control Of Temperature (AREA)
- Air Conditioning Control Device (AREA)
Abstract
AUTOMATIC RESET OF CHILLED WATER
SETPOINT TEMPERATURE CONTROL
ABSTRACT OF THE DISCLOSURE
A control system for controlling the reset of a leaving temperature setpoint of a refrigeration system. A microcom-puter system receives two data pairs entered by an operator corresponding to the amount of reset at one load and another amount of reset at another load, and receives refrigeration system operating parameters indicative of entering chilled water temperature and leaving chilled water temperature. The microcomputer processes these signals to generate a reset for the leaving chilled water temperature setpoint.
SETPOINT TEMPERATURE CONTROL
ABSTRACT OF THE DISCLOSURE
A control system for controlling the reset of a leaving temperature setpoint of a refrigeration system. A microcom-puter system receives two data pairs entered by an operator corresponding to the amount of reset at one load and another amount of reset at another load, and receives refrigeration system operating parameters indicative of entering chilled water temperature and leaving chilled water temperature. The microcomputer processes these signals to generate a reset for the leaving chilled water temperature setpoint.
Description
~ 36~75~
.~ 1 A~T~IIC RESET OF CHILL~D WA~FR
SETPOINT TEMPERATURE CONTROL
Background ~f the Inventio-n ~he-~resent.inventiun rela~es..to me~h~ds ~f oper~tin~ and control sy~t~ms for ~2friger~tion syst~ms and, mo~,e ~articu-larly, to ~thods of~Dperating and c~ntrol systems for capacity control devices, such as compressor inlet ~uide vanes, i~ ~entrifugal vapor compressi~n re~r.igeIation 3ystems where~y ~he-temperature Df ~he chilled ~ater leaving the .chiller is ~ut~atically.raised a~ the..cooling.load ~ecr~ses.
Generally, Yefrigeration systems.inclu~e an evaporator or 1~ chilleT,-a.--compre~sorj.and a condenser.. Usually, a heat : transer fluid is circulated th~ough tu~ing in the evaporator thereby forming a heat t~ansfer coil in the evaporator to t~ansfer..h~at~rQm th~ ~eat ~r~nsfeT luid flowing t~rough -the-tu~ -to--re*ri~er~nt in the-e~aporator. ...~he heat transfer 1uid chilled in the.*ubing in the ev~pora~Dr is normally water or glycol which is circ~lated to a r~mote location to.sa~isfy a T~frigeI~tion lDad. .The refrigerant in ~he evaporat~ e~7aporates as it absor~s heat from the water flowing thrDugh the tu3~.ing in: the evaporator,- and the com-.25 pressor o~rates .to ext~act this refrigerant.vapor,from the.~v~poratm, ~:o~ ress ~:his ~e~riger~n~ vapDr, and to discharge- the compressf~d vapor ..~o the condenser. .In the rondense~the r~frigel~nt.vapar is ~densed and. deliveTed ~ack to ~e- evap~ator ~here .the refrigeration. ;cycle ~egins 3 0 ~sin .
:~ ma~iTDi;~ p~ating ~ici~ncy, `it is,.:desi~able.: to ~a~ch the amo~m;t.of wDrk dolLe-.~by th~ c~mp~essQ:r to-th4 work n~ieded . -~o sa~is~y the. ~frig~rP~ion lc~ad plac2d on the ~efrigeratiDn 3~ . ' syistem.' ( =ollly, thiis is done by capacity control ~eans w~ich--adjust t~he amo~i~ of refriKerant vapor flowing through ~.2~3~7~
~he c~mp~essor. The capacity c~trol ~eans ~ay be a device ~uch as guide ~anes-which are positioned hetween the compres-;sor and the evapo~atoI which move ~etween a fully open and a fully elosed posi~i~n ~n ~espDnse to ~he temper~ture of ~he chillæd wa~er leaving ~he chilled wat~r coil in the evapora-tor. When the e~apora~or chilled wat~r tempera~ure falls, indicatin-g a red~ction in refrigerati~n load o~ the refriger-ation.system, the guide vanes-move t~ard their clo~ed position, decrea~ing the amount o~ refrigerant vapor flowing t~rou~h the-compres~r. Thi~ decreas~s the amo~nt Df work that ~st b~ ~on~-~y the compres~or.the~eby de~reasing the amount of energy ne~ded to.~erate th~-~efrige~tion system.
At the same tIme, this has.~he effect of increasing the temperature of the chilled water le~ving the e~aporator. In contrast, when th ~emp.erature of the.leavin~ chilled water rises, indicating an increase in load on the refrigeration -system,--the guide.van~s move t~ward their fully open posi-tion.. ~his~ncreases.the ~mDunt . Qf v~Dr...flowing thrDugh the compTes~r ~md- the c~p~e~sor does-~o~e wo~k the~eb~sr d{~creas-ing the t~mperatur4 of the chill~d water leavin~ the evapora-tor and allowing the refriger~tion ~y~tem to respond to the -incTeased ~frige~a~ion.load. In~this manner, the c~mpresso~ !
operat~s to maintain the temperatu~e o~ the ~hille~ water leavin~ the evaporator z~, o~ within a certain ran~e of, a set pDint ~e~erature. The`:l~avi~g chilled water temperature setpDint may ~fiually ~e`adj~sted at.~he operato~'s p nel and once set wil~ con~l~l the ~mperatur~e of-the leaving chilled water~t the~sel~cted~setpDint re~ardless Df the machine load.
Many diffel~nt capacity control syst~ms ~re known for con-olling.a ~fri~atlon ~ys.~m-:in.the ma~ner desrIi~ed above...~or ~xample, ~ne s~ch contrDl sys~m, a:.model ~P-8142-~24 ~llectronic.Chiller C~ntrol available fr~m the BaTber~Colman Company`havin~ a place.of business in Rockf~rd, Illinols, adjusts-a capacity control devic~ in a ~2867 refrigeration system as a function of the deviation of evaporato~ chilled wa~er te~perature from a desired s~t point te~pera~ur~. ~hen the leaving chilled ~ate~ temperature deviates from the sel~cted set point ~emperatur~ by a pr4de-*ermine~.~mountsthe capacity ca~trol device is ~on*inuously adju~ted ~y an ac~ua~Dr which is continuously energized by a stream of ~lectrical pul~es supplied to the actuato~. The predet~rmined amount of ~mpe~ature d~viation ~e~ore the act~ato~ ïs cont~nuously eYergiæed-prDvides a t~mperature deadband.in ~hic~ t~e cap~city.control,device i~ no~ adj~st-ed. ~he ~ulse Tate of the ~tream.o electrical pulses ~upplied to ~he actuator det~rmines the-,overall r~te of adjustment of the capacity control device.. This-pulse rate may be s~t at either'a ~inimum, ~iddle, or ma~Imum value thereby ~rovidin~ a limited..eapabil~ty.-f~r tailoring opera-tion of the co~trol system to meet specific jo~ requir~m~nts of a particular jo~ ~plica*io~ fo~ the.refrigeration sys~em.
~owevel, As with ~ost capaci*y~ con~rvl systems, once.the 'l`eaving chilled WateT t mperature setpoint is selected, the leavin~ chilled wat~r tempe~ature will-~e cDntrolled t,.the selected se~point tempeIature from zero load to full load, while the ~tering-chille~ water Emperature will devi~te from the.leaving chilled water temper~ture in a.lineaT
f~shion fr~m zero ~T ~t zeYo.load ~o design ~T at full.load.
' O~eTatin~ a capacity ~Dnt~ol ~ys*~m, ~weveT, with a fixed leaving chiIlèd water se*point is-not very ene~gy efficient at low loads7 because ~hç refrig~ati~n system is ~till maintaining a leaving chilled ~ater te~perature,~hzt i~ lower than that which is actu~lly needed to ensure c~m~rt in the space being.~ooled. ~h~s th~ere ~xi~tfi;a.need to develop apa~i*y ~trol te~m~es f m ,chill~r~,which.. ca~ r~ducP ', ~ner~y cDn~umptio~ at l~wer load~'~y raising ~he ~mp~rat~re of the ~illed wat~.14aving ~he `c~ille~ as the coolin~..load decreases.
6~SO
. 4 Summary of the Invention Therefore, it :i5 an object of the present invention to provide a si~ple, efficient, and e~fective micTocomputer system for c~n~rolling the capacity of a refrig~ration syst~.
It is another object ~f the pres~nt inve~*ion to provide an - easily programma~le microcomputer system for controlling the setpoi~ of the c~illed:wat~r leaving the.chiller directly ir.
.sesponse to.~hanges~ the cDoling load.
Thes~ ~nd other ~jects of the-present i~vention are attained ` --. by a capacity co~trol syst~m for:a.refrigeration ~ystem c~mprising a capacity~ontrol dévice f~r contr~lling refrig-1~ -e~nt ~low in the refri~eration system,..a microcomputer for resetting the leaving c~illed wate~-temperatuTe setpoint in .accordance with selec~ed parameters, and means fol generating ~irst and sec~nd signals.indic~*iv~ o~ a.sensed.*emp~r~ure -of ~he heat-tTansfer flui-d entering the:chiller and a ~ensed tempe~ature o~ the heat transfer ~luid-leaving the-chilleT, respectively. ~he fil~t and second signals are supplied to .*he micrDcomputer which deteTmi~es. ~he sched~le of~reset foT
the leaving chilled water tempe~atur~ s2tpoin~ in accordance with tuo.data pairs programmed by the .system operator into the micTocomputer. ~ach data pai~ ~nsists.of.a--~emperatuTe diffeT~nce ~nd-~:desiI~d-valu~of ~eset:a~.the-~emp~rat~re diff~rence. ~hus the leaving ~hiIled water t~mpeTature ~ setpoint ~an uary with..load,. either f~m minimum to ma2imum load oT ~twe~n any twD..intermediate.l~ad values~ The .30:- capacity control devi~.is ad~ ed.~to~con~rol ref~igerant : fl~w in the ~frigeratiDn sys*em in r~sp~nse to ~e control .~. signal ~nerAte~:~y.~he-mi~r~comp~t~r~ .By ~lec~ing ~iffer-en-~ data pai~ Dperation of the capaci~y: con~rol devi~e may ~ ~ Pasily,-eficiently, ~nd e~fectively tailored t~ ~eet 35` specific 30b re4~irements of a particular Jo~ BppliCation for the r~frigeration syst-em b~ es~a~lishing a-reset schedule ~o~
~, ~
the leaving chill~d water t~perature setpoint based ~n~-the load.
Brief Descripti~n of the ~rawin~s Still'other objects and ~dvantages Df t~e pres~nt inv~ntion will.be appalent fTom th,e f~llowing detailed desrripti~n of - the pr,esent inv~ention.in conjunction with the acc~mpanying `~ drawings; in;which th~ Teference.numerals designat~ e or cornesp~ndi~g paTts t~ro~ghout-thP same, in which:
Figure 1 is a.~rhEma~ic.illustratio~ of a c~ntri~ugal vapor co~prPssion Tefri~elati~r. system ~ith a control.syst~m fDr . var~in~ ~he ca~acity 'of the r~frigera*ion sys~m according to . the principles of the present invention; and 1~
Figur~ 2 is a ~raph of chilled water t~mperature as a func-*ion of load.
'' Desc~i~ti~n-of-the Pref~rled E~bodiment -C Referring to ~igu~e 1~ a ~apQr compressiDn refrigeration system 1 is shown having a centri.ugal compressor 2 with a control-system 3 for:varying the,ca~acity of the.. refrigera- ;
.. ti~n-system l ~ccording to the principles of the present : inven~iDn. As shown in ~ig~¢e 1, ~ .refrigera~ion system 1 2~ includes a.c~ndens~r 4`, an ~YaporatDx 5 a~d.a poppet valve 6.
In op~r~tion, ~omp~ed- g~D~S re~Tigelant~ iS dis~arged :Erom t~e compressor 2 thrcu~h compressoT discharge line 7 to the sondenser 4 wherei~ the ~aseous lefrigerant i~ cond ~ed y relatively-cool ,c~nd~sing water flowing-,th~ h tubing 8 3~ in th~ cDndens~ 4. ~he ~ondensed llqllid refri~rant from the L:ondenser-4 pa6s~ th~oug~ t~e :~opp~t valve ~ in refrig-erant~ ne 9~ D,~ oTatDr.5.~ ~ 'liq~id r~friger~nt in *he -e~apor~r ~ i6 ev~ora~ed ~o cool-a.hea~.transf~r fluid, ' ~uch as watEr ~r ~lycol, fl~wing thr~ugh tubing 1~ in the . .35--:'evap~ra`tor 5. ~his chilled heat transfer 'fluid is used to :- .cool~a-.~uilding D~ is:used fo~ other ~uch purpo~es. Th~
~8~7~0 . 6 gaseous.refrige~ant from the evaporator 5 ~lows through : compressor suction line 11 back to ~ompressor 2 undeT the -control ~f comp~essor inlet guide vanes 12. The gaseous refrigerant en~ing the c~mpxessor 2 thrc~gh the g~ide vanes 12 is compressed by the.compl~ss~r 2 and d~scha~ged 'r~m t~e ~ompressoT 2 through the.c~mpleissor discharge line 7 ~o complete the ref~igeration cycle.. ~his ~fri~e~atiGn cycle ... is continuously repeated d~ri~g nDrmal operation of the re~rigeration system l.
~e c~mp~esso~-inlet ~uide vane~.l2 are ~p~ed and closed by -.~ guide vane actuator l~ cont~clled ~y th~ ciRpacity control - system 3 which-cDmp~i es a sys~em interface.~o~rd 167 a -~ proce~sor board 17, a set point and display board 18, and an 1~ analo~ldigital.converter 19. Also, temp'erature siens~r 13 for sensing the te~perature of th~ heat transfer fluid leaving the e~pori~tor~5 ~hrough ~he tu~ing lO an~ tempera~re sensor l~.fol sensing the t~mperatu~e Df th~ehea~.tr~nsfer 1uid entering the evapora~or 5 through-the-tubi~g 10~ is c~nnPcted ~y electrical lines ~O and 22 directlv t~ the A/D conver~er 19 .
Pre~erably, the temperature siens~rs 13 a~d 15 are a tem~era-ture responsive-resistance.d~vices such as ~-t~ermistors ~5 having their seD~ing~pDTtions.lo~ated in ~ heat transfer ~luid in.the ~u~ing lO in ~he evaporat~r ~ with-th~;Y resis-tan~e moni*ored.by the A/D.converter 19, as shown in ~igure . 1. 0~ course, a~ will ~e readily apparent to ~ne of-ordinary .`~skill.i~ the art-to which the pTesent inventiorl pertains, the 30 t~esature sensors 13 and 15 may:be anv of a varie~y o~ ;
t~mp~rat~re sens~rs:suitable ~or g~nerating a signal indiea--ti~ of the--t~p~ratu~-of t~.hea~ tran~f~r ~luid.in th,e ` ~u~ing.lD in the ~vapo~a~DI-~.and or s~pplying~th~se gener-. a~ed`signals:to ~he A/D.:cDnv~t~s 19.
3~ I
The proces~or boa~d 17 may be any devic~, or c~mbinati~n ofdevices, capable o* -receiving a plurality of input signals, prDcessing ~he rec~ived inp~t si~nals according to pTepro~r~mme~ proced~res, and producing d~si~ed output ~ rol 3ignals.in.respons~ to ~he.r2ceived and.processed input signals7 in a ~anner according to t~e principles of *he present inv~n~ion. ~r ex~mple, the processor ~oard 17 may - romprise a.microc~mputer~ such as a model 8031 microco~put~r ~v~ilabl~.from.I~tel C~rporation ~hich has a place o~ busi-n~ss at 5a~ta Clar~, Califo~nia.
Als~, pre~esably,.~he A/D ~on~ert~r l9 is a dual ~slope A/D
- c~nverter which shall pro~ess all analog i~puts-into digital :~ outputs a~d which is suitable for use with the processor 1~: board 17-. A1SD~ .it sh~uld be not~d tha~7.although the A/D
c~nve~ter is shown as a sepalate ~odule in Fi~ure 17 this A/D
converter 19 may ~e phvsically ~art of the.processor board 17 in an..actual ca~aci~J contrDl system 3.
~urther, pre~Tably, the.~et pDint and display board 18 compris~s a Yisual display, including, foT example, light - .emi~ing ~io~es ULEDls)-.Dr liquid crystal display..(LCD's) devices ~D~ming a ~Nlti-~igit display which is under the COntTO1 of the ~rDcessoT ~oard 17. A1SD~ .the set point and display ~oa~d 18-includes a de~ice, such as- a ~e7 pad which ~e~ves as ~ata ~n*ry pDr.t as~ell as .a pr~.gr~m~lng~-~oo fo~-~ntering the data p~irs to 4sta~1ish a ~set schedule ~r the~chilled wate~ leavin~-the evapora~or 5 through the .. ~V~o~Rt~ chilled water:.~u~in~ 10.
3~) .Stil^l furth~r, ~T~ferably, the system interface board 16 .. in~lu~sr~s le2s~.0ne.swi~ching ~vice~ su~h as a mDdel SC-14D tria~ availa~le from ~en~ral Elect~ic, Corp. which has B plac~ usiness at.Auburn, ~ew York, which is.us~d as a 3~ s~itchin~ element for controlling a supply of electTical - p~uer In~.sh~wn~ through electrical lines 21 to the guide 2 367S~3 . ~
vane actuator 14. The triac switches on the system interface ~ard 16 ar~ cDnt~olled in respons~,to control signals Yeceived by the triac switches f~m the process~r ~oard,17.
In this ~anner, elect~ial power i8 supplied *hrough the 5 : ~lec$ric~1`;,1ine.21:to th~.guide vane actua~or 14-under ~ontrol o~ the pr~cessol ~oard 17 *o operate Ihe guide vane actuato~ 14 in the ~anner accor~ing to the pri~ciples of the :present invention:'which is described in,detail ~elow. Qf .coulse, a~ will ~ Ieadily appaTent ~o o~e of ordinary skill in the aTt tG whic~ the pre~ent Inventi~n p~r~ain~, switching devices other than tTiac switche~ may be ~sed in c~ntrolling power.flow fr~m the~po~er supply (not shDw~ through the electTical li~e~ o the.guide`vane actuator,l4 in response to output control signals fro~ the pTocessor bDard 17.
'~he guide vane actuator 14 ~y ~e any device sui~a~le for driving ~he guid~ vane~ l~ tow~Id ~eith~.their open or closed ;.positiun-in,-r~s~,nse to`:~e~ectrical p~w.e~ sig~als ~ecei~ed via elect~ical linè 21. ~ For example, the guide-vane actuato~ 14 20 : may ~ an electric:~otoT~ suc~ as a model MC-3~1 ~otor availa~le fro~ the Bar~eT-Colnan C~m~any having a place of usi~ess ~n RDckfo~d, Il~insis~,for driving the.guide vanes 12 toward either ~heir open or'closed p~ition-dep~nding on ~: which ~ne of two tsiac 6witches ~on the syst~m interface ~oard 2~ 16 is ~ct~a~ed in sesponse to con~xol.signals.r~ceived by ~he triao:~witches fr~m.the~ p~OcesSD~ ~oard''1'7.` The guide van~
actuator 14.,drives ~he guide-vanes'12 toward:either t~eiT
fully-:`open OT fully -elosed position at a cons~-ant, ~ixed~ate only during~that p~tion D~ a selected ~se.time interval 3D durin~ which-~he~ appropriate trai~:~witch. Dn the ~y5~m in~r~ace ~ard 16:i~,ac~uated.
~æf~rring`n~w to'.,~i~ure.~2,' a~dashed ~tsaigh~-line curv~ h, is ~hown which.rep~e~n*s the.leaving chill~d:wAte~:t~mpeTature ~3~-- which a pri~-art contsol system withDut reset would produce.
t`: . Also, a solid sloped:line curve B is shown which repres~nts 8675( . 9 ~-the leaving chilled ~at~r tempeTatU~e setpoint o~ the present inven~ion ~ith reset. These setpoints are ax~itrary. lhe -amount o~ ~set that is to ~ applied is computed ~y the ~icro~Tocessor after two da~a pai~ a~e ~n*ered into the setpnint ~nd display boa~d by ~he Op~ratOT by wa~ o~ ~h~ k~y ~ad. .~y havl~g th~ ~icr~pTocessol ~utomatically ~just ~he chilled wat~T setpoint as a func~ion of l~ad, the operator ~ay ~educ~ energy consumptio~ during certain load conditi~ns.
~ ~he-Enteri~g c~ ed ~ate~ tempeT~ture corresponding to curve A wi~hout ~set, is sh~wn-~y,dashed slope~ ~rve C.while . eurYe D, ~2p~ese~ts the ~nte~ing chilled w~eT t~peratuxe during any load cDndi~i~n with the d~sired r~set D~ curve B.
~he v~rtical a~is ~f ~igure-,2 is the t~ era~ure,o~ the ' `chilled water enteling and leaving the evapo~ator. The 15 : horizon~al axis of''Figure 2 is the lo~d,on the refIigeration system. Also sh~wn on the hvrizontal axi~ is a typical set of ~ valu~s. ~he:val~e of 10, chosen foY ~vaporator ~ at :full load, was ~n aI~itr~ry chDice.
ln the ~ampl~ given in ~igure 2, the curve label~d A illus-.trates an arhitrar~ setp~in~ fo~ the leavi~g chilled water temp~r~tue and t~e curve labeled B.illustra~es the coTre-. sponding leaving chilled water ~emperature wqth th~ desiredamount:~f reset applied. `Thus,: in the ~xample, assuming a 2~ design.~Tof 10~-~t:lOOZ load, the operator desi~es the ~efTigæration syste~ to ~ntrol`the tem~erat~re:of^the leavin~ chilled wate~ at 45F-when the:load is lOD%~and 50F
when the load is OZ. Thus:the opera~or woul~ input two data pairfi into ~he micr~computer, the first data pair ~ould ~e a res~t o~ 5F at ~T - 0F and ~he second data.pair would be a res~* Df 0F ~t ~T:= lOF. Accordingly, with the data pai~s in :- th~:~xample ~n~u~t~d into:*h~ ~etp~i~*::and:display ~oard.18, ~s:~h~e-cooli~g lo~d chang~s, t~e micIop~oces~or wlll calc~-la~e a-:new leaving ~hilled wate~ temperat~re setpoint to 3~ -~nsue that the leaving ~hilled water tem~rature is the . -cor~ect value`for ~he load con~i~ions.. If or ex&mple ~he ~8~750 lo~d decreased from 100% to 20%, wi~h the ab~v~ data pai~s .: inputted, the leaving chilled water temperature setpoint `~uld inc~eafie fTom 4~F to 4gF, whereas without setpoint ~eset the leaving ~hilled wate~ ~mperatur~ ~etpoint wD~ld emai~ at 4~F. Thus,-ener~y cons~m~tion is ~duced as the ..~hilled water l~aving the chiller.i~ Taised ~ the ~ooling load decreases.
. ~ny n~m~e~ of data pairs ca~ be-inp~tted.int~ the 8etpoint ~nd di~lay board dep~nding ~pon ~he desired setpDint.
While ~his in~ntion h~s been des~ibed with reference to a particular em~odiment discl~sed herein, it is ~o~ cDnfined to - the details set orth:herein and this application is intended to cov~r a~y modifications or changes as :may cume within the ~oope of the i~ention.
.~ 1 A~T~IIC RESET OF CHILL~D WA~FR
SETPOINT TEMPERATURE CONTROL
Background ~f the Inventio-n ~he-~resent.inventiun rela~es..to me~h~ds ~f oper~tin~ and control sy~t~ms for ~2friger~tion syst~ms and, mo~,e ~articu-larly, to ~thods of~Dperating and c~ntrol systems for capacity control devices, such as compressor inlet ~uide vanes, i~ ~entrifugal vapor compressi~n re~r.igeIation 3ystems where~y ~he-temperature Df ~he chilled ~ater leaving the .chiller is ~ut~atically.raised a~ the..cooling.load ~ecr~ses.
Generally, Yefrigeration systems.inclu~e an evaporator or 1~ chilleT,-a.--compre~sorj.and a condenser.. Usually, a heat : transer fluid is circulated th~ough tu~ing in the evaporator thereby forming a heat t~ansfer coil in the evaporator to t~ansfer..h~at~rQm th~ ~eat ~r~nsfeT luid flowing t~rough -the-tu~ -to--re*ri~er~nt in the-e~aporator. ...~he heat transfer 1uid chilled in the.*ubing in the ev~pora~Dr is normally water or glycol which is circ~lated to a r~mote location to.sa~isfy a T~frigeI~tion lDad. .The refrigerant in ~he evaporat~ e~7aporates as it absor~s heat from the water flowing thrDugh the tu3~.ing in: the evaporator,- and the com-.25 pressor o~rates .to ext~act this refrigerant.vapor,from the.~v~poratm, ~:o~ ress ~:his ~e~riger~n~ vapDr, and to discharge- the compressf~d vapor ..~o the condenser. .In the rondense~the r~frigel~nt.vapar is ~densed and. deliveTed ~ack to ~e- evap~ator ~here .the refrigeration. ;cycle ~egins 3 0 ~sin .
:~ ma~iTDi;~ p~ating ~ici~ncy, `it is,.:desi~able.: to ~a~ch the amo~m;t.of wDrk dolLe-.~by th~ c~mp~essQ:r to-th4 work n~ieded . -~o sa~is~y the. ~frig~rP~ion lc~ad plac2d on the ~efrigeratiDn 3~ . ' syistem.' ( =ollly, thiis is done by capacity control ~eans w~ich--adjust t~he amo~i~ of refriKerant vapor flowing through ~.2~3~7~
~he c~mp~essor. The capacity c~trol ~eans ~ay be a device ~uch as guide ~anes-which are positioned hetween the compres-;sor and the evapo~atoI which move ~etween a fully open and a fully elosed posi~i~n ~n ~espDnse to ~he temper~ture of ~he chillæd wa~er leaving ~he chilled wat~r coil in the evapora-tor. When the e~apora~or chilled wat~r tempera~ure falls, indicatin-g a red~ction in refrigerati~n load o~ the refriger-ation.system, the guide vanes-move t~ard their clo~ed position, decrea~ing the amount o~ refrigerant vapor flowing t~rou~h the-compres~r. Thi~ decreas~s the amo~nt Df work that ~st b~ ~on~-~y the compres~or.the~eby de~reasing the amount of energy ne~ded to.~erate th~-~efrige~tion system.
At the same tIme, this has.~he effect of increasing the temperature of the chilled water le~ving the e~aporator. In contrast, when th ~emp.erature of the.leavin~ chilled water rises, indicating an increase in load on the refrigeration -system,--the guide.van~s move t~ward their fully open posi-tion.. ~his~ncreases.the ~mDunt . Qf v~Dr...flowing thrDugh the compTes~r ~md- the c~p~e~sor does-~o~e wo~k the~eb~sr d{~creas-ing the t~mperatur4 of the chill~d water leavin~ the evapora-tor and allowing the refriger~tion ~y~tem to respond to the -incTeased ~frige~a~ion.load. In~this manner, the c~mpresso~ !
operat~s to maintain the temperatu~e o~ the ~hille~ water leavin~ the evaporator z~, o~ within a certain ran~e of, a set pDint ~e~erature. The`:l~avi~g chilled water temperature setpDint may ~fiually ~e`adj~sted at.~he operato~'s p nel and once set wil~ con~l~l the ~mperatur~e of-the leaving chilled water~t the~sel~cted~setpDint re~ardless Df the machine load.
Many diffel~nt capacity control syst~ms ~re known for con-olling.a ~fri~atlon ~ys.~m-:in.the ma~ner desrIi~ed above...~or ~xample, ~ne s~ch contrDl sys~m, a:.model ~P-8142-~24 ~llectronic.Chiller C~ntrol available fr~m the BaTber~Colman Company`havin~ a place.of business in Rockf~rd, Illinols, adjusts-a capacity control devic~ in a ~2867 refrigeration system as a function of the deviation of evaporato~ chilled wa~er te~perature from a desired s~t point te~pera~ur~. ~hen the leaving chilled ~ate~ temperature deviates from the sel~cted set point ~emperatur~ by a pr4de-*ermine~.~mountsthe capacity ca~trol device is ~on*inuously adju~ted ~y an ac~ua~Dr which is continuously energized by a stream of ~lectrical pul~es supplied to the actuato~. The predet~rmined amount of ~mpe~ature d~viation ~e~ore the act~ato~ ïs cont~nuously eYergiæed-prDvides a t~mperature deadband.in ~hic~ t~e cap~city.control,device i~ no~ adj~st-ed. ~he ~ulse Tate of the ~tream.o electrical pulses ~upplied to ~he actuator det~rmines the-,overall r~te of adjustment of the capacity control device.. This-pulse rate may be s~t at either'a ~inimum, ~iddle, or ma~Imum value thereby ~rovidin~ a limited..eapabil~ty.-f~r tailoring opera-tion of the co~trol system to meet specific jo~ requir~m~nts of a particular jo~ ~plica*io~ fo~ the.refrigeration sys~em.
~owevel, As with ~ost capaci*y~ con~rvl systems, once.the 'l`eaving chilled WateT t mperature setpoint is selected, the leavin~ chilled wat~r tempe~ature will-~e cDntrolled t,.the selected se~point tempeIature from zero load to full load, while the ~tering-chille~ water Emperature will devi~te from the.leaving chilled water temper~ture in a.lineaT
f~shion fr~m zero ~T ~t zeYo.load ~o design ~T at full.load.
' O~eTatin~ a capacity ~Dnt~ol ~ys*~m, ~weveT, with a fixed leaving chiIlèd water se*point is-not very ene~gy efficient at low loads7 because ~hç refrig~ati~n system is ~till maintaining a leaving chilled ~ater te~perature,~hzt i~ lower than that which is actu~lly needed to ensure c~m~rt in the space being.~ooled. ~h~s th~ere ~xi~tfi;a.need to develop apa~i*y ~trol te~m~es f m ,chill~r~,which.. ca~ r~ducP ', ~ner~y cDn~umptio~ at l~wer load~'~y raising ~he ~mp~rat~re of the ~illed wat~.14aving ~he `c~ille~ as the coolin~..load decreases.
6~SO
. 4 Summary of the Invention Therefore, it :i5 an object of the present invention to provide a si~ple, efficient, and e~fective micTocomputer system for c~n~rolling the capacity of a refrig~ration syst~.
It is another object ~f the pres~nt inve~*ion to provide an - easily programma~le microcomputer system for controlling the setpoi~ of the c~illed:wat~r leaving the.chiller directly ir.
.sesponse to.~hanges~ the cDoling load.
Thes~ ~nd other ~jects of the-present i~vention are attained ` --. by a capacity co~trol syst~m for:a.refrigeration ~ystem c~mprising a capacity~ontrol dévice f~r contr~lling refrig-1~ -e~nt ~low in the refri~eration system,..a microcomputer for resetting the leaving c~illed wate~-temperatuTe setpoint in .accordance with selec~ed parameters, and means fol generating ~irst and sec~nd signals.indic~*iv~ o~ a.sensed.*emp~r~ure -of ~he heat-tTansfer flui-d entering the:chiller and a ~ensed tempe~ature o~ the heat transfer ~luid-leaving the-chilleT, respectively. ~he fil~t and second signals are supplied to .*he micrDcomputer which deteTmi~es. ~he sched~le of~reset foT
the leaving chilled water tempe~atur~ s2tpoin~ in accordance with tuo.data pairs programmed by the .system operator into the micTocomputer. ~ach data pai~ ~nsists.of.a--~emperatuTe diffeT~nce ~nd-~:desiI~d-valu~of ~eset:a~.the-~emp~rat~re diff~rence. ~hus the leaving ~hiIled water t~mpeTature ~ setpoint ~an uary with..load,. either f~m minimum to ma2imum load oT ~twe~n any twD..intermediate.l~ad values~ The .30:- capacity control devi~.is ad~ ed.~to~con~rol ref~igerant : fl~w in the ~frigeratiDn sys*em in r~sp~nse to ~e control .~. signal ~nerAte~:~y.~he-mi~r~comp~t~r~ .By ~lec~ing ~iffer-en-~ data pai~ Dperation of the capaci~y: con~rol devi~e may ~ ~ Pasily,-eficiently, ~nd e~fectively tailored t~ ~eet 35` specific 30b re4~irements of a particular Jo~ BppliCation for the r~frigeration syst-em b~ es~a~lishing a-reset schedule ~o~
~, ~
the leaving chill~d water t~perature setpoint based ~n~-the load.
Brief Descripti~n of the ~rawin~s Still'other objects and ~dvantages Df t~e pres~nt inv~ntion will.be appalent fTom th,e f~llowing detailed desrripti~n of - the pr,esent inv~ention.in conjunction with the acc~mpanying `~ drawings; in;which th~ Teference.numerals designat~ e or cornesp~ndi~g paTts t~ro~ghout-thP same, in which:
Figure 1 is a.~rhEma~ic.illustratio~ of a c~ntri~ugal vapor co~prPssion Tefri~elati~r. system ~ith a control.syst~m fDr . var~in~ ~he ca~acity 'of the r~frigera*ion sys~m according to . the principles of the present invention; and 1~
Figur~ 2 is a ~raph of chilled water t~mperature as a func-*ion of load.
'' Desc~i~ti~n-of-the Pref~rled E~bodiment -C Referring to ~igu~e 1~ a ~apQr compressiDn refrigeration system 1 is shown having a centri.ugal compressor 2 with a control-system 3 for:varying the,ca~acity of the.. refrigera- ;
.. ti~n-system l ~ccording to the principles of the present : inven~iDn. As shown in ~ig~¢e 1, ~ .refrigera~ion system 1 2~ includes a.c~ndens~r 4`, an ~YaporatDx 5 a~d.a poppet valve 6.
In op~r~tion, ~omp~ed- g~D~S re~Tigelant~ iS dis~arged :Erom t~e compressor 2 thrcu~h compressoT discharge line 7 to the sondenser 4 wherei~ the ~aseous lefrigerant i~ cond ~ed y relatively-cool ,c~nd~sing water flowing-,th~ h tubing 8 3~ in th~ cDndens~ 4. ~he ~ondensed llqllid refri~rant from the L:ondenser-4 pa6s~ th~oug~ t~e :~opp~t valve ~ in refrig-erant~ ne 9~ D,~ oTatDr.5.~ ~ 'liq~id r~friger~nt in *he -e~apor~r ~ i6 ev~ora~ed ~o cool-a.hea~.transf~r fluid, ' ~uch as watEr ~r ~lycol, fl~wing thr~ugh tubing 1~ in the . .35--:'evap~ra`tor 5. ~his chilled heat transfer 'fluid is used to :- .cool~a-.~uilding D~ is:used fo~ other ~uch purpo~es. Th~
~8~7~0 . 6 gaseous.refrige~ant from the evaporator 5 ~lows through : compressor suction line 11 back to ~ompressor 2 undeT the -control ~f comp~essor inlet guide vanes 12. The gaseous refrigerant en~ing the c~mpxessor 2 thrc~gh the g~ide vanes 12 is compressed by the.compl~ss~r 2 and d~scha~ged 'r~m t~e ~ompressoT 2 through the.c~mpleissor discharge line 7 ~o complete the ref~igeration cycle.. ~his ~fri~e~atiGn cycle ... is continuously repeated d~ri~g nDrmal operation of the re~rigeration system l.
~e c~mp~esso~-inlet ~uide vane~.l2 are ~p~ed and closed by -.~ guide vane actuator l~ cont~clled ~y th~ ciRpacity control - system 3 which-cDmp~i es a sys~em interface.~o~rd 167 a -~ proce~sor board 17, a set point and display board 18, and an 1~ analo~ldigital.converter 19. Also, temp'erature siens~r 13 for sensing the te~perature of th~ heat transfer fluid leaving the e~pori~tor~5 ~hrough ~he tu~ing lO an~ tempera~re sensor l~.fol sensing the t~mperatu~e Df th~ehea~.tr~nsfer 1uid entering the evapora~or 5 through-the-tubi~g 10~ is c~nnPcted ~y electrical lines ~O and 22 directlv t~ the A/D conver~er 19 .
Pre~erably, the temperature siens~rs 13 a~d 15 are a tem~era-ture responsive-resistance.d~vices such as ~-t~ermistors ~5 having their seD~ing~pDTtions.lo~ated in ~ heat transfer ~luid in.the ~u~ing lO in ~he evaporat~r ~ with-th~;Y resis-tan~e moni*ored.by the A/D.converter 19, as shown in ~igure . 1. 0~ course, a~ will ~e readily apparent to ~ne of-ordinary .`~skill.i~ the art-to which the pTesent inventiorl pertains, the 30 t~esature sensors 13 and 15 may:be anv of a varie~y o~ ;
t~mp~rat~re sens~rs:suitable ~or g~nerating a signal indiea--ti~ of the--t~p~ratu~-of t~.hea~ tran~f~r ~luid.in th,e ` ~u~ing.lD in the ~vapo~a~DI-~.and or s~pplying~th~se gener-. a~ed`signals:to ~he A/D.:cDnv~t~s 19.
3~ I
The proces~or boa~d 17 may be any devic~, or c~mbinati~n ofdevices, capable o* -receiving a plurality of input signals, prDcessing ~he rec~ived inp~t si~nals according to pTepro~r~mme~ proced~res, and producing d~si~ed output ~ rol 3ignals.in.respons~ to ~he.r2ceived and.processed input signals7 in a ~anner according to t~e principles of *he present inv~n~ion. ~r ex~mple, the processor ~oard 17 may - romprise a.microc~mputer~ such as a model 8031 microco~put~r ~v~ilabl~.from.I~tel C~rporation ~hich has a place o~ busi-n~ss at 5a~ta Clar~, Califo~nia.
Als~, pre~esably,.~he A/D ~on~ert~r l9 is a dual ~slope A/D
- c~nverter which shall pro~ess all analog i~puts-into digital :~ outputs a~d which is suitable for use with the processor 1~: board 17-. A1SD~ .it sh~uld be not~d tha~7.although the A/D
c~nve~ter is shown as a sepalate ~odule in Fi~ure 17 this A/D
converter 19 may ~e phvsically ~art of the.processor board 17 in an..actual ca~aci~J contrDl system 3.
~urther, pre~Tably, the.~et pDint and display board 18 compris~s a Yisual display, including, foT example, light - .emi~ing ~io~es ULEDls)-.Dr liquid crystal display..(LCD's) devices ~D~ming a ~Nlti-~igit display which is under the COntTO1 of the ~rDcessoT ~oard 17. A1SD~ .the set point and display ~oa~d 18-includes a de~ice, such as- a ~e7 pad which ~e~ves as ~ata ~n*ry pDr.t as~ell as .a pr~.gr~m~lng~-~oo fo~-~ntering the data p~irs to 4sta~1ish a ~set schedule ~r the~chilled wate~ leavin~-the evapora~or 5 through the .. ~V~o~Rt~ chilled water:.~u~in~ 10.
3~) .Stil^l furth~r, ~T~ferably, the system interface board 16 .. in~lu~sr~s le2s~.0ne.swi~ching ~vice~ su~h as a mDdel SC-14D tria~ availa~le from ~en~ral Elect~ic, Corp. which has B plac~ usiness at.Auburn, ~ew York, which is.us~d as a 3~ s~itchin~ element for controlling a supply of electTical - p~uer In~.sh~wn~ through electrical lines 21 to the guide 2 367S~3 . ~
vane actuator 14. The triac switches on the system interface ~ard 16 ar~ cDnt~olled in respons~,to control signals Yeceived by the triac switches f~m the process~r ~oard,17.
In this ~anner, elect~ial power i8 supplied *hrough the 5 : ~lec$ric~1`;,1ine.21:to th~.guide vane actua~or 14-under ~ontrol o~ the pr~cessol ~oard 17 *o operate Ihe guide vane actuato~ 14 in the ~anner accor~ing to the pri~ciples of the :present invention:'which is described in,detail ~elow. Qf .coulse, a~ will ~ Ieadily appaTent ~o o~e of ordinary skill in the aTt tG whic~ the pre~ent Inventi~n p~r~ain~, switching devices other than tTiac switche~ may be ~sed in c~ntrolling power.flow fr~m the~po~er supply (not shDw~ through the electTical li~e~ o the.guide`vane actuator,l4 in response to output control signals fro~ the pTocessor bDard 17.
'~he guide vane actuator 14 ~y ~e any device sui~a~le for driving ~he guid~ vane~ l~ tow~Id ~eith~.their open or closed ;.positiun-in,-r~s~,nse to`:~e~ectrical p~w.e~ sig~als ~ecei~ed via elect~ical linè 21. ~ For example, the guide-vane actuato~ 14 20 : may ~ an electric:~otoT~ suc~ as a model MC-3~1 ~otor availa~le fro~ the Bar~eT-Colnan C~m~any having a place of usi~ess ~n RDckfo~d, Il~insis~,for driving the.guide vanes 12 toward either ~heir open or'closed p~ition-dep~nding on ~: which ~ne of two tsiac 6witches ~on the syst~m interface ~oard 2~ 16 is ~ct~a~ed in sesponse to con~xol.signals.r~ceived by ~he triao:~witches fr~m.the~ p~OcesSD~ ~oard''1'7.` The guide van~
actuator 14.,drives ~he guide-vanes'12 toward:either t~eiT
fully-:`open OT fully -elosed position at a cons~-ant, ~ixed~ate only during~that p~tion D~ a selected ~se.time interval 3D durin~ which-~he~ appropriate trai~:~witch. Dn the ~y5~m in~r~ace ~ard 16:i~,ac~uated.
~æf~rring`n~w to'.,~i~ure.~2,' a~dashed ~tsaigh~-line curv~ h, is ~hown which.rep~e~n*s the.leaving chill~d:wAte~:t~mpeTature ~3~-- which a pri~-art contsol system withDut reset would produce.
t`: . Also, a solid sloped:line curve B is shown which repres~nts 8675( . 9 ~-the leaving chilled ~at~r tempeTatU~e setpoint o~ the present inven~ion ~ith reset. These setpoints are ax~itrary. lhe -amount o~ ~set that is to ~ applied is computed ~y the ~icro~Tocessor after two da~a pai~ a~e ~n*ered into the setpnint ~nd display boa~d by ~he Op~ratOT by wa~ o~ ~h~ k~y ~ad. .~y havl~g th~ ~icr~pTocessol ~utomatically ~just ~he chilled wat~T setpoint as a func~ion of l~ad, the operator ~ay ~educ~ energy consumptio~ during certain load conditi~ns.
~ ~he-Enteri~g c~ ed ~ate~ tempeT~ture corresponding to curve A wi~hout ~set, is sh~wn-~y,dashed slope~ ~rve C.while . eurYe D, ~2p~ese~ts the ~nte~ing chilled w~eT t~peratuxe during any load cDndi~i~n with the d~sired r~set D~ curve B.
~he v~rtical a~is ~f ~igure-,2 is the t~ era~ure,o~ the ' `chilled water enteling and leaving the evapo~ator. The 15 : horizon~al axis of''Figure 2 is the lo~d,on the refIigeration system. Also sh~wn on the hvrizontal axi~ is a typical set of ~ valu~s. ~he:val~e of 10, chosen foY ~vaporator ~ at :full load, was ~n aI~itr~ry chDice.
ln the ~ampl~ given in ~igure 2, the curve label~d A illus-.trates an arhitrar~ setp~in~ fo~ the leavi~g chilled water temp~r~tue and t~e curve labeled B.illustra~es the coTre-. sponding leaving chilled water ~emperature wqth th~ desiredamount:~f reset applied. `Thus,: in the ~xample, assuming a 2~ design.~Tof 10~-~t:lOOZ load, the operator desi~es the ~efTigæration syste~ to ~ntrol`the tem~erat~re:of^the leavin~ chilled wate~ at 45F-when the:load is lOD%~and 50F
when the load is OZ. Thus:the opera~or woul~ input two data pairfi into ~he micr~computer, the first data pair ~ould ~e a res~t o~ 5F at ~T - 0F and ~he second data.pair would be a res~* Df 0F ~t ~T:= lOF. Accordingly, with the data pai~s in :- th~:~xample ~n~u~t~d into:*h~ ~etp~i~*::and:display ~oard.18, ~s:~h~e-cooli~g lo~d chang~s, t~e micIop~oces~or wlll calc~-la~e a-:new leaving ~hilled wate~ temperat~re setpoint to 3~ -~nsue that the leaving ~hilled water tem~rature is the . -cor~ect value`for ~he load con~i~ions.. If or ex&mple ~he ~8~750 lo~d decreased from 100% to 20%, wi~h the ab~v~ data pai~s .: inputted, the leaving chilled water temperature setpoint `~uld inc~eafie fTom 4~F to 4gF, whereas without setpoint ~eset the leaving ~hilled wate~ ~mperatur~ ~etpoint wD~ld emai~ at 4~F. Thus,-ener~y cons~m~tion is ~duced as the ..~hilled water l~aving the chiller.i~ Taised ~ the ~ooling load decreases.
. ~ny n~m~e~ of data pairs ca~ be-inp~tted.int~ the 8etpoint ~nd di~lay board dep~nding ~pon ~he desired setpDint.
While ~his in~ntion h~s been des~ibed with reference to a particular em~odiment discl~sed herein, it is ~o~ cDnfined to - the details set orth:herein and this application is intended to cov~r a~y modifications or changes as :may cume within the ~oope of the i~ention.
Claims (5)
1. A control system for controlling the reset of a leaving chilled fluid temperature setpoint in a refrigera-tion system of the type which includes a microprocessor system and an evaporator wherein a refrigerant absorbs heat from a heat transfer fluid passing therethrough, comprising:
means for entering at least two data pairs into the microcomputer and for generating a signal corresponding to each of said entered data pairs wherein the first data pair corresponds to the amount of reset from a fixed leaving chilled fluid temperature setpoint at a first load and the second data pair corresponds to the amount of reset from said fixed leaving chilled fluid temperature setpoint at a second load;
means for generating a first control signal which is a function of the temperature of the heat transfer fluid entering the evaporator; and processor means for receiving said signal corre-sponding to each of said entered data pairs, and said first and second control signals, for processing the received signals according to preprogrammed procedures to determine a setpoint temperature for the heat transfer fluid leaving the evaporator for the actual load on the refrigeration system.
means for entering at least two data pairs into the microcomputer and for generating a signal corresponding to each of said entered data pairs wherein the first data pair corresponds to the amount of reset from a fixed leaving chilled fluid temperature setpoint at a first load and the second data pair corresponds to the amount of reset from said fixed leaving chilled fluid temperature setpoint at a second load;
means for generating a first control signal which is a function of the temperature of the heat transfer fluid entering the evaporator; and processor means for receiving said signal corre-sponding to each of said entered data pairs, and said first and second control signals, for processing the received signals according to preprogrammed procedures to determine a setpoint temperature for the heat transfer fluid leaving the evaporator for the actual load on the refrigeration system.
2. A control system as set forth in claim 1 wherein said processor means determines said setpoint temper-ature in proportion to the entered data pairs and the differ-ence between entering and leaving temperature of the heat transfer medium.
3. A method of resetting a leaving chilled liquid temperature setpoint of a refrigeration system, having a microcomputer system and an evaporator wherein a refrigerant absorbs heat from the chilled liquid passing therethrough, which comprises:
generating a first setpoint signal corresponding to a first data point entered into the microprocessor;
generating a second setpoint signal corresponding to a second data point entered into the microprocessor;
generating a first temperature signal corresponding to actual entering chilled liquid temperature;
generating a second temperature signal correspond-ing to actual leaving chilled liquid temperature; and generating an output signal in proportion with a predetermined relationship of said first and second setpoint signals, and said first temperature and said second tempera-ture signals.
generating a first setpoint signal corresponding to a first data point entered into the microprocessor;
generating a second setpoint signal corresponding to a second data point entered into the microprocessor;
generating a first temperature signal corresponding to actual entering chilled liquid temperature;
generating a second temperature signal correspond-ing to actual leaving chilled liquid temperature; and generating an output signal in proportion with a predetermined relationship of said first and second setpoint signals, and said first temperature and said second tempera-ture signals.
4. A method as set forth in claims 3 wherein said first entered data point corresponds to a data pair corre-sponding to the amount of reset from a fixed leaving chilled liquid temperature setpoint at a first load condition, and said second entered data point corresponds to a data pair corresponding to the amount of reset from said fixed leaving chilled liquid temperature setpoint at a second load condition.
5. A method as set forth in claim 4 wherein said output signal is generated in proportion to the sum of said setpoint signal and the difference between said first and said second temperature signals.
Applications Claiming Priority (2)
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US82540586A | 1986-02-03 | 1986-02-03 | |
US825,405 | 1986-02-03 |
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KR (1) | KR930004391B1 (en) |
CA (1) | CA1286750C (en) |
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GB8702008D0 (en) * | 1987-01-29 | 1987-03-04 | Calibre Energy Systems Ltd | Energy producing source control |
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Family Cites Families (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1414102A (en) * | 1964-09-24 | 1965-10-15 | Carrier Corp | Improvements to control systems |
US4201061A (en) * | 1978-03-22 | 1980-05-06 | Carrier Corporation | Automatic chilled water setpoint temperature control |
US4282718A (en) * | 1979-09-12 | 1981-08-11 | Borg-Warner Corporation | Evaporator inlet water temperature control system |
GB2156098B (en) * | 1984-02-18 | 1987-07-29 | Heat Trace Ltd | Control of electric heating apparatus |
US4506516A (en) * | 1984-04-06 | 1985-03-26 | Carrier Corporation | Refrigeration unit compressor control |
US4538422A (en) * | 1984-05-14 | 1985-09-03 | Carrier Corporation | Method and control system for limiting compressor capacity in a refrigeration system upon a recycle start |
US4589060A (en) * | 1984-05-14 | 1986-05-13 | Carrier Corporation | Microcomputer system for controlling the capacity of a refrigeration system |
US4539820A (en) * | 1984-05-14 | 1985-09-10 | Carrier Corporation | Protective capacity control system for a refrigeration system |
US4546618A (en) * | 1984-09-20 | 1985-10-15 | Borg-Warner Corporation | Capacity control systems for inverter-driven centrifugal compressor based water chillers |
DE3601817A1 (en) * | 1986-01-22 | 1987-07-23 | Egelhof Fa Otto | CONTROL DEVICE FOR THE REFRIGERANT FLOW FOR EVAPORATING REFRIGERATION SYSTEMS OR HEAT PUMPS AND EXPANSION VALVES ARRANGED IN THE REFRIGERANT FLOW |
GB8702008D0 (en) * | 1987-01-29 | 1987-03-04 | Calibre Energy Systems Ltd | Energy producing source control |
-
1987
- 1987-01-28 CA CA000528339A patent/CA1286750C/en not_active Expired - Lifetime
- 1987-02-02 GB GB8702265A patent/GB2191021B/en not_active Expired - Lifetime
- 1987-02-03 FR FR878701279A patent/FR2593897B1/en not_active Expired - Lifetime
- 1987-02-03 KR KR1019870000842A patent/KR930004391B1/en not_active IP Right Cessation
- 1987-02-03 JP JP62024411A patent/JPS62182555A/en active Pending
Also Published As
Publication number | Publication date |
---|---|
GB8702265D0 (en) | 1987-03-11 |
FR2593897B1 (en) | 1991-02-22 |
GB2191021A (en) | 1987-12-02 |
GB2191021B (en) | 1990-03-07 |
KR930004391B1 (en) | 1993-05-27 |
KR870008162A (en) | 1987-09-24 |
FR2593897A1 (en) | 1987-08-07 |
JPS62182555A (en) | 1987-08-10 |
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