Purdue University

Purdue e-Pubs International Compressor Engineering Conference

School of Mechanical Engineering

1988

Scroll Compressor Design Criteria for Residential Air Conditioning and Heat Pump Applications, Part I: Mechanics James W. Bush Copeland Corporation

John P. Elson Copeland Corporation

Follow this and additional works at: http://docs.lib.purdue.edu/icec Bush, James W. and Elson, John P., "Scroll Compressor Design Criteria for Residential Air Conditioning and Heat Pump Applications, Part I: Mechanics" (1988). International Compressor Engineering Conference. Paper 605. http://docs.lib.purdue.edu/icec/605

This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at https://engineering.purdue.edu/ Herrick/Events/orderlit.html

3CHQJ,L COMPRESSOR DESIGN CRI'l'ERIA

~OR

RES cDENTIH

AIR CONDITIONING AND HEA'r PUMP APPLICATIONS

PART I: t·1ECHANICS

James W. Bush Mgr. - New Products Design and Analysis

John P. Elson Mgr. - New Products

New Products Department Copeland Corporation Sidney, Ohio U.S.A. ABSTRACT The application of scroll compressor technology to the residential air conditioniong and heat pump markets has generated a variety of compressor design approaches to address special system requirements. This paper >till revie>t both special design needs of this application and unique scroll design concepts used to address these needs. Design concept discussions >till include: • • •

Scroll compliance - radial and axial High pressure versus lO>t pressure shell Bearing sys terns

Scroll compressor technology, in comparison to other positive displacement types, >till be outlined in terms of energy efficiency, noise and vibration, durability, and field application. Both inherent design advantages and design challenges >till be reviewed for scroll compressors.

INTRODUCTION A scroll concept was identified early in the twentieth century as steam engine expander [1), and shortly after >tas recognized as having potential as a gas compressor [2] [3]. Until recently, both technology and motivation for high

compressor performance were not sufficient to warrant engineering

resources

to develop the design as a production product. Even today, some vie>t the scroll as an object of curiosity >tith limited potential to compete >tith existing positive displacement compressor technologies. It is the objective of this paper to demonstrate the scroll compressor to be the clearly superior design technology of the future. Included in this revie>t is a discussion of both scroll technology and design criteria necessary to meet the rugged demands of a high performance, high durability air conditioning and heat pump compressor. Being a relatively ne>t technology for serious development, engineers have approached scroll design from many directions >tith the result being interesting technical differences of opinion as to the best design approach. One example of thia is the decision to use either a low pressure or high pressure compressor housing. Reciprocating compressors generally ernploy a low pressure housing, while

fixed vane rotary Scroll compressors due tion today.

compressors generally operate >ti th a high pressure housing. with either a high or low pressure housing are both in pro-

THE SCROLL ADVANTAGE Regardless of the design approach, scroll compressors have inherent advantages over comparable reciprocating and rotary technologies. Most important of these is efficiency where the scroll potential is approximately 10 percent better than competing technologies. Figure 1, which illustrates a breakdown of compressor

83

~ach loss for ener•gy the shows technology, difference primary between scroll and other technologies to be the 3. 0 --J,,;:;.:..:..-1 near zero valve and gas In g0neral, flow loss. the scroll (;ompres:Jur is more ~ fficient due t':.l a. 68.0 flow nearly continuous

74.2

68.0

process with the ab::::ence of valve lo~s, excellent and se;;li.nt> potenti.al, enhanced

effi-

th~nnal

USEFUL WORK

ciency.

to addLtion In SCROLL PISTON ROTARY i.nh,.rently high mechanFIGURE I Leal ,, ffic Leney, scroll compressor efficiency is COMPRESSOR LOSS ANALYSIS I ARI- 1990 PROJECTED) further enhanced in an air conditioning and heat pump system due to the compressor's near 100 Figure 2 illuspercent volu.netric efficiency at all operating conditions. trates system cooling and heat.cng capacity when both scroll and reciprocating

50;-------------- ------------------ ------------------ ----, Demand System Capacity (Piston) Systom CapeCIIY (Scroll)

~ /.-::;/

40

/

30

2zZ?:>~

-~~

Lower /

.,

57"

Capacity

_-'

Higher

-Higher S~ER - Less Cycling -Belter Dehumidification

~

Capacity "Better Comfort

20

10

Less Supplemental Heat

15

25

35

55

45

65

75

85

95

105

Ambient Temperature (Deg. F)

Figure 2 System Capacity vs. Residence Demand For u::HH:l. U> fHitL::;t'y a typic'"ll three-ton re.~idential requirement. comparison, both cornpr=i!sGors yi.~ld the samta system capacity at the 95cli" ambient r;;tLng paint. 1-low"ver, at th~ l•r

shaft

ga.p4 misalig nment also tJ:ontro l.s the :=d.r scroll

Many

compr~sso~s

butlt 11dio~ th~ conc~pt of benrin g ~ousLng wit~~ hot[l m~~n b1~tw-een

l''igur'~

l'dyo'..lt

th:LS

.1

been s~ngle

b~arLnB3

Soe Sl.;riJll s mht 1li)to~. Whi. Lq mOrt! G00'hr. i.i.onn. l in

thl"' 12. and

l1av~

;::,.pp.-:t['f~ntlJ

c).pprot-h~h

lLmite( 'l A.lr gap

r•:q_u"i.r~s

c~ontrGl,

(~ost

FIGURE 12

SCROLL LAYOUT - OVERHUNG_.M.QIQR

~~rre(:tiv~~,

dc.:.ar,u

of oversi zed bearin gs, ~n the form rotors , and exc~ss over"3. ll height .

c-:cJncet~sions

(:!o11.:1t~rbored

erably

more

li:l!~l:J convcn tion.r~t.l but consid rten ~ e;n rtpp:"or-v:h w~1 ].·~h t s sorncwh a. t See gs on eithqr side of the motor. bea.rln main hhJ ~.:h~-~ i.:; to plt-3.r.:l' t=:ffer;tlV'~ of a expt-~nse and ~~ffoi;"t (~'l{tra. 7nt a.ppar1 the t.hLs lnvolvr~D Wh·L1S! 13. l?l.gUrt~ size, rni..nimum thg ben13f its of rnin1.tnum ber:l.Lin g ber.lri.n g hollsi.n g, seeond~ry and P.limin Ht·Lon of rotot"" countet"bor~, l, contro gap air rigid nmf·)nt, angu1f- lr mi3A.~ie

90

Leduc t i.on

in

ht:d gh t provide a t:ost wh.ich ie!

max unum

~ffiL~'iency

at

~quiv>·fl:lh:), ' 1\'anfl. J~lpan Soc. Vol. 51, c_,_. t.G6, pp. IOf3:-19fl"l, 1995.

[5]

l'l':'l!"ishit~l,

[6]

ru!->'1,

J.~

1

G.~rillat,

C~,.rapreEJst:J:;.~c~" P;_~r~lUf.::'

J.,

~)e1.bel~

s.,

"Dil~~n~':lion .l Optimi.zati on of Gc:rol~ 1 Vo1. j , pp. 840-

i91j6 CorrqJr':"sSC!'" En~in,..:!.";rinr:; Cunfer~Ui')r.,::

P5l, 19ec..

92