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International Conference School of

1980 The Compressor - The tS eps to Maturity A. B. Newton

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Newton, A. B., "The Refrigeration Compressor - The tS eps to Maturity" (1980). International Compressor Engineering Conference. Paper 423. https://docs.lib.purdue.edu/icec/423

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 THE REFRIGERATION COMPRESSOR - THE STEPS TO MATURITY

Alwin B. Newton Visiting Professor, Purdue University and Consultant, York, Pennslyvania 17403

refrigera­ opportunity of less competition. In a Today we are likely to take the depression" for granted just as we take matter of three years the "great tion compressor and I was to become thankful for granted the way the uses of refrigera­ was upon us, into our for having made such a choice. I have re­ tion have intertwined themselves direct­ we think of food mained in the refrigeration and its everyday lives. Whether such as transportation and marketing; ly related fields processing, 1927. accuracy in industrial processes; computer ever since systems; or human comfort, all depend on For ease in discussion I have divided the refrigeration and the refrigeration com­ 1900, locations past into four periods, that prior to pressor. In fact some southern 1925, that from development almost the period from 1900 to owe their industrial and from 1950 to 1975. I to air conditioning in manufact­ 1925 to 1950, entirely also have a few comments about the uring plants, in offices, and in homes, to will car post 1975 period. In each period the say nothing of the air conditioned grossly influ­ . Refrigeration design of was which gets people to of the many forms and applications has be­ enced by which in its many were readily available and understood, and come a way of life, not only in the United of other in the last two periods the choice States, but increasingly in many perceived levels And save refrigerants was based on places in the world. certain applications. An­ heating . of safety for important other major influence on compressor design of drive available and is the heart of any refrig­ has been the type The compressor source of power. eration system except for the very few the which are directly operated by heat such as 1865 to 187 5 a Before 1900 the absorption units. In compressors this period refrigeration compressors were For refrigeration few tens of about 1865. Factories were more made each year. These were massive steam begins their weight like job shops then like the compressor driven with as seen by the 1876 in excess of their factories we now know in tons considerably of Fig.2. The office and in tons of refrigeration. photograph capacity factory management team typical of that time 15,000,000 factory is shown in Fig. 3. At that Today the industry produces some use for driving and one engine driven the Corliss engine was in compressors per year, of machinery, and used for automotive air condi­ various forms compressor type water pumps were in general use. The tioning can produce over three tons of thing with a only 14#, Corliss engine was a massive refrigeration, yet it weighs pulley and flywheel some­ In a great many ways the progress combined drive Fig. 1. times as large as 30' in diameter. But it in refrigeration is more spectacular than the concepts noteworthy was a natural thing to combine in the automotive field. It is engine to provide longer cometh to our of pumps and the Corliss that the ice man no machines. homes and groceries. refrigeration how Since both the engine and the compressor This paper will identify and discuss it was an changes have been accomplish­ had reciprocating components some of these step to use a common shaft for the ed, and indeed what the changes were. If obvious this cranks of both components. And since I have any qualifications to attempt required height because I began to engine rooms often had any chronology it may be often horizontal and the myself to the refrigeration the engine was dedicate compressor cylinder was placed above the industry in 1927 when still in college. I re­ crankshaft in a vertical position. I had tried to identify an area of Eastman Kodak engineers and one call one such compressor at not already flooded with been in operation for rapid growth. The "reverse which I was told had which should have Fig. 4 shows a compound Corliss cycle" as refrigeration was sometimes 70 years. driving a multi-cylinder called was not as broadly understood as the power cycles and seemed to offer the compressor.

344 The typical operating speed of 120 to 180 changers were used rpm allowed for the of the use of poppet type valves , Fig. 5., and bare of considerable mass. arrange­ Since manual control ments for cooling of storages. These was usually employed and the had large flow to internal and the was also controlled considerable mass. These factors manually it was not together at all unusual for with the size and type of compressors and large amounts of to be returned to drives made it desirable the compressor, to keep the and thus most compressors equipment operating once it was had safety heads which started. were spring loaded Hence the need for capacity control soon to remain in a sealed position for all developed. normal operating , but to open in the case liquid entered the cylinders. The Evaporator capacity valve location could be accomplished was usually in the cylinder by adjustment of hand expansion head, or in the valves, or cylinder walls. by valving off portions of the evaporator entirely. If this resulted These early compressors in too low a used a cross-head suction some means of and piston rod rigidly affixed reducing to the piston. compressor capacity was needed and was The piston rod entrance into the cylinder usually accomplished was packed to prevent by opening clearance the leakage of pockets in the compressor cylinder refrigerant. The piston rod, walls. the piston, See Fig. 6. By the end of this period and the valves were the only moving parts some compressors exposed to the refrigerant, were equipped with cylinder and it appears bypass valves. See Fig. 7. that lubrication processes were similar to those used in steam , using various End of Period. By 1900 types of feeders to introduce we see that refrig­ a small eration by mechanical means is well accept­ amount of oil needed. The external moving parts ed. Equipment is large and bulky. Control also used steam engine practices such is almost entirely as oil cups, or Manzel by manual means with lubricators. With clearance pockets and some so little oil exposed to refrigerant cylinder bypass it in use. Steam engines drive most compres­ appears that its excursion to impede heat sors, transfer tho belted drives are in evaporators or condensers was starting to make not a major problem. their appearance. The common refrigerants are ammonia, carbon dioxide, air, with a smattering Refrigerants. Ammonia was the refrigerant of sulphur dioxide. Compressors operate at low speeds, of choice in a large portion of pre-1900 most refrigeration require manual lubrication at reason­ plants. Ice making to sup­ able intervals, valves plement the ice cut from must be seated or ponds and lakes "ground" and are of the poppet was a growing industry. The benefits type, but of with maintenance they have extremely long cold storage for preservation of foods were life. appreciated, and cold storages began to emerge. Certain process cooling was early 1900 to 1925 recognized as an important application of refrigeration, for example in the making During of photographic film. this period the usage of refriger­ ation expanded rapidly. Many plants for manufacture Carbon dioxide was of "artificial ice" were built. used frequently as the Reefer cars refrigerant where ammonia would on railroads were developed have been for long distance shipment hazardous, but the principle of the super­ of perishable critical foods. Some very large cold storage in­ "supercharged" cycle does not seem stallations to have been used. High-side were made, including at least pressures in one system in which the range of 1200-1400 p.s.i. were exper­ ammonia was piped below ienced city streets to numerous stores. Ice with C0 2 and hence these compressors were designed with cream became popular in the corner drug closed crankcases and store and in restaurants. packing around the rotating crank shaft. See Fig. 8. Such systems Small compressors were available by the were used by the Navy and in end of the period some other shipboard applications, for soda fountains, but but ice and were still used to pack required high for a given cooling lots effect. of the . These same compressors were used in conversions of domestic ice boxes to "artificial" refrigeration Air systems were also used quite extensive­ with ly on the unit remote, usually in the basement. shipboard in spite of their large A few industrial power consumption. Even air conditioning install­ the dense air ations were made and one theatre system, which used air under several was cooled atmo­ in 1914. See Fig. 8. These and other spheres pressure, required massive machinery applications and made an expansion signified the growth of the engine a part of the refrigeration industry. cycle as well as a compressor. Chilled brine dis­ Both would tribution was applied to large systems. then be driven by a separate steam engine. Capacity Control. Double-pipe heat ex-

345 Compressors. Compressors got smaller as were, and are still, used to reach lower their speeds were increased to a ran~e of than can be efficiently 300 to 600 rpm. Enclosed crankcases such hanJled by a single stage of compression. as shown in Fig. 7 became more standar-d,_ packing was moved to the rotating It is during this period that the small and the more shaft outside the crankshaft bearing. condensing unit was developed with a units became smaller with or less standardized combination of Steam driven a side-by-side cylinder arrangements. See compressor, electric motor drive, and Electric motors became the usual water cooled , all mounted to­ Fig. 9. 12. driver, and the big pulley of the compressor gether on a common base. See Fig. an outboard bearing to take This unit was widely used in cooling of often required end of the pull of the belt and the weight of the ice cream cabinets, and towards the pulley. Towards the end of the period a the period air cooled models appeared. were tried in small They were used in the early domestic few rotating seals ex­ compressors. , often by converting an isting ice box with an evaporator in the conversions The move to a packed crankshaft instead of ice compartment. In many cases and crosshead meant that all or new installations were made in kitchens a piston rod liquid re­ the moving parts except the drive pulley of apartment houses with the to the refrigerant atmosphere. frigerant piped from a central condensing were exposed from each refrig­ With refrigerants such as ammonia, sulphur unit and a suction return dioxide, and carbon dioxide the solubility erator. with oil was very low, and to some extent with methyl chloride. Refrigerants. The refrigerant of choice for this was also true installations New oils had to be developed to avoid un­ cold storages and other fixed with the refrigerants was ammonia, but smaller systems increas­ desirable reactions chloride, particularly if moisture was present. ingly turned to so2 and to methyl were kept at or near the suction particularly for a1r-cooled condensing Crankcases as mentioned for pressure. units. Central units such , I well remember apartment use used so 2 and became almost standard the day the in such an apart­ Trunk type out upper and lower portion in contact ment we rented sprang a leak. We moved with an made, and with the cylinder and a central portion open in a hurry while repairs were of a suction port in the side of when we returned the plants had succumbed in front were a new the cylinder. See Fig. 7. Valves were and some of the decorations lighter in weight, often being diaphragm color! or finger type with the suction valves in piston and the discharge The increasing use of air conditioning in the head of the of larger C0 valve in the cylinder head. Such valves theatres lead to development 2 instead of being re­ machines which became standard for most could be replaced C0 was non-toxic ground. such applications since 2 and free of fire hazard. See Fig. 13. the usual Cold storages were found to need freezer For the same reasons co 2 became spaces above freezing. To refrigerant on shipboara. The "super­ space and other to re­ accommodate such systems with one compressor, charged" cycle was soon worked out were designed in late the heat rejection to dual suction machines temp­ which the low temperature was in the usual liquid temperature and evaporator position in the cylinder wall, but an erature. provided to be uncover­ additional port was to some extent ed by the piston at its lowest position. Other refrigerants were used was then connected to such as iso-, methyl chloride and This additional port and the higher temperature suction, the methylene chloride in small systems, through this port and in in larger systems, but the use of from which entered a major doing so raised the pressure of the lower these refrigerants did not have pressure gas already in the cylinder to that influence on compressor design. pressure gas. The mixture was of the higher newer appli­ then compressed and discharged in the normal Capacity Control. Many of the Fig. 10 for a verticle compressor cations of refr1geration systems had wider way. See of load than of this type with the low pressure suction and more frequent variations and Fig. 11 for ice plants or cold storages, so the need valve in the piston head, evident. compressor with the suction for better capacity control became a horizontal were adapted to be valve in the cylinder wall. Smaller compressors started and stopped as a means of capacity of providing for two temperatures control, and automatic temperature and Another way developed for this in storage was to use a booster compressor pressure controls were gas from the lower purpose. This required the introduc~ion. to take the refrigerant d1d system and discharge it into of various methods to see that the 011 temperature during the repeated the compressor which receives the higher not leave the crankcase temperature gas directly. Booster systems starts.

346 For larger compressors the use of suction more process refrigeration and for lOOP bypass became more prevalent. Ports could temperatures, and the industry be placed responded. at 1/3 or 2/3 of the piston Heat pumps were introduced, even some with travel, arranged so that when their control capacity control, but the savings valves were were not closed there was negligable of sufficient interest to people at the change in cylinder volume, but when these going prices of other valves energy sources. were opened, the port connected to Many experimental heat pumps were installed suction and the piston was thus prevented with ground source and well from starting water sources, compression until it had and they even made a major article in passed the port. A variety of port arrang­ Readers Digest about 1950. ements could be provided on one or more cylinders to get as many steps of capacity But without doubt the most important event as might be needed, the main precaution during this period being was the development of to maintain enough refrigerant flow the refrigerants by DuPont and to prevent local over heating. The ports . Without could be either such a refrigerant manually or automatically se;ies a large portion of the things jfist controlled. recited would not have occurred. End of Period. By 1925 use of refrigeration The increased use of refrigeration comp­ has become widespread, and is an important ressors and other components part of many in many industries. Small equipment applications indicated the need for has been developed for automatic operation, standards and but better performance informa­ manual control remains on some larger tion of units. The American jobs. Ammonia, carbon Society of dioxide, sulphur Refrigerating Engineers developed the dioxide, are the main refrigerants. Some needed testing standards use of iso-butane, to bring order methyl chloride, and out of chaos, while the American methylene chloride is extant. Society Speeds have of Heating &Ventilating Engineers pro­ been increased until small compressors vided technical operate at background. (These speeds as high as 800 rpm. societies merged in Electric motors drive most the late SO's to form compressors with ASHRAE). Trade associations such as belt and pulley arrangements. While a few ACRMA, are direct REMA and NWAHA were also formed and driven by synchronous motors. contributed to useful See Fig. 14. Many alternating standardization of current equipment, just as the Air Conditioning motors in medium sizes are the repulsion­ and Refrigeration induction type. Domestic Institute is doing today refrigeration by use of a broad concensus process. has started by conversion of ice boxes, and by a few units designed as refrigerators Compressors. In the late 20's the General with mechanical compressors, but the Electric compressor is usually Company introduced the first truly remotely located. hermetic design of compressor Such compressors may be air cooled instead in their of water cooled. domestic refrigerator line. This was the Mechanically refrigerated famous "Monitor ice cream is in most soda Top" refrigerator in which fountains. Re­ the cooled condenser frigeration is still used to make "arti­ surrounded the compressor, and from which the evapor-. ficial ice", and air conditioning has ator started in theatres depended into the cooled compartment. and some factories With a four pole which are sensitive to high . motor directly driving the crank shaft the speed of 1750 rpm was 1925-1950 considered to be venturesome. Initially the refrigerant was so 2, but before many In this period years it was changed to R-12. It was refrigeration has become a about 1930 when must for many purposes. The decentraliza­ Frigidaire introduced tion of the domestic refrigerators with R-12 refrig­ equipment has caused the devel­ erant. Other opment of smaller compressors manufacturers kept their open of relative­ compressor designs for the ly stable designs which can be mass pro­ first decade of duced. Manufacturer's this period with belt driven open drives shops became more and various forms of mechanical modernized. See Fig. 15. The first shaft seals. hermetic compressors appear in domestic refrigerators, By 1933-34 several designs of R-12 comp­ and are followed by semi­ ressors were hermetics as air conditioning available. Large systems becomes using R-12 employed modified ammonia available in small mass produced packages. compressors Availability of such as the 4 cylinder 14" x increases to 10" unit of Fig. 16. For most areas of the country and the house­ the first time hold refrigerator compressors in tonnages of 1/2 to 15 tons is in most every homo. could be placed in Department stores followed theatres or immediately adjacent in to living spaces without the comfort air conditioning, and soon office inherent buildings dangers of NH or so . Several unusual followed suit. World War II lent compressors 3 2 great impetus appeared and though used for to small, even isolated, a time, refrigerators with specialized then faded out of the picture. compressors Examples are the Savage and drives. War suppliers saw need for Arms mecury driven "Archimedes Spiral" compressor (Fig. 17)

34 7 of the R~l2 design. (See Fig. 18) In B-ecause of the solubility and the Zorzi problems in start~ single cylinder accom~ refrigerant in oil, new_ the Zorzi design a the major oil two compression strokes per re~ up were encountered, and plished to provide non~foaming volution. companies endeavored o,ils. The solubility also meant that oil the introduction could be carried with the liquid refrig~ The safety of R~l2 led to greater room air conditioners. erant into the evaporator to a of self~contained previous refrigerants units sat on the floor in front of extent than with the These was not soluble. Oil separ~ a window and drew condenser air in and out in which oil 450# or so. ators were introduced, and various means through the window. Weight was to compressors as shown in within compressors were developed Some had hermetic did return through 19 and 20, but many still had belt separate the oil which figures and assure that it entered the driven compressors using repulsion~induc~ the suction end of the crankcase. Until understood and planned tion motors for dTives. By the of oil in start, induction motors, were for, this change to solubility 30's capacitor was perceived as a major more common as compresso.r drives, and often the refrigerant required some kind of equalizing orifice or problem. valve to permit starting. The large numbers of portable storage boxes services during World War and shapes of compressors came used by the armed New forms new demands on the industry and into being. One firm introduced a line of II put direct justified more rapid development of 3, 5 or 7 cylinder compressors, Air conditioning with each cylinder compressor refinements. driven at 1150 rpm, to better use of ship~ about 5 tons capacity at air became important sized for spaces, and were employed in some conditioning conditions. By use of a board from 15 to 70 tons army quarters. So the refrigeration double shaft motor units quite active in its be furnished from a single industry remained capacity could equipment fields during the war. set of parts for cylinders, valves and normal pistons. Another company folded the radial of design into a The post war period saw a resurgence system used by the foregoing commercial uses. to reduce space require­ air conditioning and "W" configuration conditioners proliferated, and and still others introduced "Vee" Window air ments, whole house air conditioning began to take designs. Coincident with these develop~ latter half of the of numerous "semi~ hold. Through~out the ments was the introduction companies developed for designs with motors in the period specialized hermetic" the manufacture of compressors, so that refrigerant directly driving radial piston their own cylinder many companies who did not have arrangements. One such line had the field of of capacity per compressor designs entered dimensions to give l~ton These were "mass pro~ and was earlier used in 3 and 5 air conditioning. cylinder, duction" enterprises, and the level of ton air conditioners of the water cooled the cost Such tooling involved served to reduce type, for use as "store ". make the increase of to some 15 tons of compressors and to lines expanded rapidly at a more rapid rate. By use of multiple compressors in u.seage proceed capacity by the close of the period the usual compres~ a single unit. sor speed for sizes under 15 tons capacity was 1750 rpm with a few smaller designs Some early designs of open co,mpressors for rpm. with operating with 2~pole motors at 3500 R~l2 used new versions of shaft seals very flat nose surfaces, often made of as co , lowest possible Refrigerants. Such refrigerants 2 materials designed for the and iso~butane were attention had to be SO , methyl chloride friction. Particular completely phased out during this to the cooling of the shaft seal, al~ost given or period. Yet early in the period so 2 had usually by circuiting of refrigerant, of choice for uomestic One compres~ been the refrigerant by a spray of lubricating oil. refrigerators. The developed a "balanced seal" and small commercial sor manufacturer 1934 Refrigerating Data Book states on by mounting the nose on a diaphragm so of the page 138, "The small in capacity supported as to reduce the force added by a few crankcase pressure increased. of 1/20 to 3 h. p. models seal contact as their invasion of the comfort Fig. 21. firms since See cooling field use most of the common re~ with so predominating in the compressors went to thin plate type frigerants 2 Most smaller, and CH Cl in the larger sizes."' valves. Some retained the trunk type 3 came as valve in the piston The change from these refrigerants piston with the suction others of the Freon series others began to place both valves R~l2, and some head, while widely available. in the cylinder head. Some used ring type became to gain more flow area, and reed valves the end of the period, R~ll, R~ll4 were began to appear. At this time valves By valves prevalent on some rotary compressors and seem to have been empirically designed, and R~22 was the subject of experiment. valve breakage was a rather frequent service problem.

348 Capacity Control. The need for capacity aurants, for process needs. For larger control, at least in intermediate and systems engineers understand lar.ger sized machines, design and increased with the most every building planned also plans its air conditioning usages wherein loads typ­ air conditioning system. ically pass through zero at some time of the day, and reach a maximum on rel~tively There is demand for larger factory assem­ few days during the year. Small un1ts have bled units for air conditioning, been generally and in controlled in an on-off some cases for refrigeration. So many manner. Several lines of compressor pro­ units have been installed that cities are vided cylinder unloaders as a standard or beginning to refuse optional the use or disposal of feature during the last hal~ of more water from water cooled refrigeration the period. Most of these systems l1fted and air conditioning the equipment. The re­ suction valve to form a sort of internal sulting move to air cooled bypass and condensing will much attention was placed on place more demands on the compressor. acheiving a low intercept of the "zero capacity" point on the capacity vs. power Automotive air conditioning plot. Fairly is just becom­ rapid operation of the in­ ing available. A large portion dividual cylinder capacity of the controls, with installations are made after the car leaves the resulting short time constant as to the factory, compressor but this will soon change to capacity, and the long time a predominance of factory installations. constants of the refrigeration system caused these systems to act as though continuously Compressors. A number modulated. See of major changes Fig. 22. were immediately ahead for the refriger­ ation compressor. The Some open drive compressors demand was heavy were fitted with for lighter weight equipment, for physic­ two or three speed motors to better adapt ally to load smaller size, and for change to weld­ changes, but since demand charges ed hermetic constructions. were not prevalent, A change from and efficiency was not R-22 began as it was realized as great a concern as later, that a given few were sold. displacement could produce about 60% more capacity End of Period after such a change. Some .. By 1950 small compressors changes in parts were are mass produced in quanity. needed because of Frozen foods the higher pressures, and some new problems have entered the market, and storage and transport developed in oil control because of the received a large impetus from multi-phase solubility World War II usages. Air regimes of oil in conditioning of R-22. Motor developments were public buildings has become a must. needed to Many provide the newly required increased power residences are centrally air conditioned, at acceptable but mostly as retrofits efficiency. To make matters since builders do even more complicated this change not yet consider it needed or especially came at salable. the time when air conditioning equipment Railway air conditioning has went to air improved the cooled condensers. This meant comfort and cleanliness in still higher pressures travel. Some buses are on the discharge air conditioned. side, and resulted as well Packard even offered an air conditioned in higher temp­ automobile. eratures. But soon the 3-horse power R-12 compressor for water cooled applications became a 5-horse power Methods of rating compressors were R-22 compressor well suitable for use in air cooled equipment. defined, and they could be placed into a system of other components with known By ratings to produce 1960, a further move to increase the required results. Most performance of equipment, except in the fractional a given size and weight horse compressor came about with the power sizes was water cooled, using once change from through 4-pole motors to 2-pole motors, thus nearly flow from city water or cooling doubling towers. Some evaporative the refrigeration capacity of a condensers were given frame. A given in use. Compressor designs were bore and then quite produced about three times the stable during the last decade of this period, amount of but usage refrigeration it did some eight or ten was increasing rapidly. years previously! 1950 - 1975 Almost concurrently a number of air source heat pumps were We enter this period with introduced for residential a well developed use with the result that market for frozen foods which could more hours per be kept year of operation was imposed on in freezers in the average food store or in compressors homes, and portions of the time a considerably and with adequate means of trans­ higher portation in the compression ratio existed. Further­ frozen state. Room air more, heat pumps conditioners are being installed of this type go through in great frequent changeover from heating numbers in offices and homes, while whole to cooling house and back again, and have numerous defrost air conditioning equipment is widely periods, available for both of which impose greater homes also. Larger units are on the compressor. available for stores and offices, for rest-

349 the compressor component to suffer were tested in early development phases, Perhaps al­ most from these changes in use was the none went into production. Even the valve system. While plate and reed valves ready accepted cylinder unloading systems, had been used for several decades the tech­ though still used, were not further devel­ determine valve stresses and to oped to give low intercepts at no-load for nology to been optimize valve designs did not exist. One 2-pole R-22 compressors such as had of the many contributions of the Herrick acheived with 4-pole R-12 machines. Laboratories here at Purdue University has research and understanding of Some further use of multi-speed drives was been their ever the compressor valve. Herrick has acheived made during this period. However the recognition of the work done, and decreasing size of standard motor frame worldwide the valve designs now survive their 60 opera­ sizes for a given output has reduced tions per second for thousands of hours, and gains since motor efficiency suffered. their operation at very high pressure ratios, and high pressure levels. I consider this Since 1972, the energy shortages have given one of the major contributions to the con­ new impetus to the potential improvements tinued survival of the refrigeration compres­ in efficiency from variable capacity. sor. However, by 1975, the end of this period no significant changes had been observed. One of the other notable compressor develop­ ments during this period is that of the End of Period. Once again compressors have automotive air conditioning compressor. become physically smaller by use of R-22 Driven at a speed somewhat greater than that to replace R-12, and the change to 2-pole engine, and forced to operate at the motors. Special compressors are mass pro­ of the and highest road speeds, and even during forced duced for automotive air conditioning high speeds, the compressor a large percentage of all cars manufactured downshifts at in survives short periods of 8000 rpm opera­ are air conditioned. Most new homes term operation at 3000 to 4000 large areas of the country are air condi­ tion, .long ones have rpm, and still cools the car at 800 rpm. tioned, and many of the older its capacity to that of the evapor­ been retrofitted. It is unusual to build To match air ator and the condenser, it is usually cycled any large building without full at unusually frequent intervals. conditioning. Aircraft have their own on­ on and off for use on Shaft seals, valve systems, and oil manage­ board air conditioning systems all been developed to acheive the the ground and in the air. Most cross­ ment have buses are air 3000 hours of operation typical of the life country buses and many city of the automobile. The weight of these un­ conditioned. but mass produced compressors, ranges usual, in supermarkets from 14# to 40#. See Fig. 1. The frozen food counters take as much as 20% of the display space. Reciprocating compressors now Refrigerated cases take another 20% at Refrigerants. We in the use either R-12 or R-22 in a very large above freezing temperature.· percentage of applications. Some cold east eat California lettuce throughout still use ammonia, but in most of the winter, and enjoy many other storage systems Cooked such applications R-22 and some other Freon benefits of refrigerated transport. are the most common. foods are frozen in "TV" portions, and are type refrigerants market. Special low temperature applications may an important portion of the food refrigerants, but they Hospitals enjoy better recovery records use some non-Freon in critical are in the large minority. because of the air conditioning areas, and in patient rooms. The 1950's and early Capacity Control. air conditioning 1960's may have been the period of the In short refrigeration and to different means have become the very basis for our so call­ greatest consideration the heart of each of capacity control. The improvements in ed life style. And at efficiency which could be refrigeration system or each air condition­ operation and in refrigeration achieved by applying capacity control had ing system is one or more been recognized. In one case experimental compressors. heat pumps operated with capacity control, and equipped with condenser and evaporator Post 1975 systems which maintained good capacity had The four years since 1975 are the start of heat transfer even at low usage a seasonal COP of 4.1 as corn­ a new era when reductions of energy demonstrated It is also the start pared to the operation of the same units will be paramount. control showing a COP of of an era when another shift in refriger­ without capacity to environmental 2.2 for a season's operation. Yet, the ants might occur due cost of electricity during concerns, but that is too early to predict artificially low larger manufact­ this period did not encourage the at this time. Many of the most of compressors from full development and manufacture of such urers now purchase their manufacturers and thus find it units. specialized more difficult to make innovative .changes Even though many types of capacity control

350 which they by themselves could put into suddenly their products. out of print and available only as But a brief look at what photo copies. might be before us may be enlightening. The most powerful new tool Compressors. In many ways the for capacity design of control is speed control for positive the refr1geration compressor is a mature dis­ technology. placement compressors. Solid state inver­ In addition to understanding tors can be used valves due to the work to change the 60 cycle or here at the Herrick 50 cycle current used in Laboratory, the mathematical modeling most of the world's other of power supplies to any desired frequency functions within the compressor is voltage. and most helpful. Purdue's The frequency determines the models have enabled rotating speed of the compressor manufacturers to develop their own motor so models while the voltage is chosen to give that compressors are more easily design­ operation proper ed for special characteristics at the new frequency. Not only such as can the frequency and higher efficiency. Motor design hence the speed be and frame reduced from the usual 3500 choice are an integral part of the compres­ rpm, but it can sor design, also be increased to a speed such as 4500 and may be considered in the rpm so that effort to save energy. a small compressor can handle short time demands for higher capacity. Induction motors operate Solid state electronics has brought well under these possibility the variable power supply conditions, of efficient speed change over the anly any desired important loss in efficiency being due range into the realm of accomp­ the fact to lishment. Thus compressors that the same slip is needed, what­ which can adapt ever the rpm, to produce to any load by changing their capacity the same torque. be expected. can See Fig. 23. Very likely this loss eliminated can be by use of permanent magnet rotors which would then To improve efficiency of devices operate at synchronous such as speed and avoid slip loss heat pumps which operate over a very wide even at full load. range of suction and discharge pressure, While the compressors are needed possibility of these controlled which under one speed drives is great condition can tolerate the very indeed, the full high suc­ realization of their energy tion pressures from heat taken from a saving poten­ storage at temperatures tial will require much greater attention as high as lOOF or to the possibly llOF, and deliver design of the heat transfer compon­ it at only 20 to ents of the re£rige.ration 40 degrees F higher. Possibly the speed system. New control is the designs will be needed which maintain answer since mass flow high refrigerant a through the valves would be side heat transfer co­ reduced so that efficient even at low they might survive the high density involv­ velocity. So perhaps ed as the gas flows the compressor is leading other components through them. At the in maturity! same time the same compressor must at operate all the pressures and pressure ratios we now impose on it. Toward the Future, While we may think Here is a whole new the refrigerat1on that field which the ability to compressor design and efficiently utilization has control speed opens up for the industry, reached maturity, we should note that within the last and I wonder if the compressor models we few months such have built can new features as speed control have been be extended to predict the introduced results and the needed changes. and applied to reciprocating compressors. While little was said herein To a large extent regarding such other forms of compressors such future thoughts are as rotary speculations, but the need designs or screw compressors, is sufficient to they may be considered justify consideration in depth for such to have reached a improvements. similar stage of maturity as can to design. We feel sure that conferences such as this Refrigerants. in which we are engaged at Purdue's It is doubtful if any new Laboratory, Herrick refrigerants are needed for and the individual efforts of operating rea­ the various design sons. The Freon family covers as teams throughout the range wide a world will produce further of points as is likely to be improvements in needed. The compressor design. Perhaps the concept question of environmental maturity of effects is still before is really the ability to make new us, and could cause designs based changes in either the basic refrigerant, on a wide base of experience, or and thus expect the results in the methods of handling to avoid any to produce the large fraction effects sought. We have come a long of production escaping into from way the atmosphere. the 120 rpm massive compressors of a century ago. Capacity Control. Presently there be seems to an examination of many of the means of capacity control on which experiments were run in the 1950's. It is of interest that many of the patents then issued are now

351 Modern Automotive Air Fig. 2 1865 Compressor Fig. 1 Shop Conditioning Compressor Manufacturing

4 Vertical compressor driven by 3 1865 Office and management Fig. Fig. compound Corliss engine team for compressor manufacturer

Fig. 6 Clearance pockets in Fig. 5 Open type water cylinder wall

352 Fig. 7 Compressor with manual Fig. 8 First theatre to be air-condi- cylinder by-pass tioned, 1914

Fig. 9 Side-by-side engine and compressor Fig. operated at 140 rpm ~0 Vertical compressor used for dual suction pressure

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Fig. 11 Double acting horizontal dual Fig. 12 suction compressor Methyl chloride soda fountain condensing unit

353 for Navy driven Fig. 14 Synochronous motor direct driven Fig. 13 C0 2 compressor by DC motor compressors

Fig. 16 4 cylinder 14" x 10" Freon-12 1920's Fig. 15 Compressor shop of the late compressor made from ammonia unit operated at 180 rpm

Fig. 17 Fig. 17 "Archimedes Spiral" compressor, used mercury liquid

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Fig. 18 zorgi compressor, 2 strokes per Fig. 19 Section sketch of early room revolution air conditioner

Fig. 20 Early room air conditioner with Fig. 21 Water cooled wood cabinent condensing unit for R-12 with balanced seal made from 1934 to about 1966

Fig. 22 Schematic of compressor Fig. 23 Characteristics capacity control used for cylinder of variable by cylinder unloading frequency-variable voltage electrical drive for induction motors

355