Goble, G. H.

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Purdue UniversityPurdue e-PubsInternational Refrigeration and Air ConditioningConference School of Mechanical Engineering1992A Drop-In CFC-12 Replacement for AutomotiveAirconditioningG. H. GobleUSAFollow this and additional works at: http://docs.lib.purdue.edu/iraccThis document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu foradditional 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.htmlGoble, G. H., "A Drop-In CFC-12 Replacement for Automotive Airconditioning" (1992). International Refrigeration and AirConditioning Conference. Paper 200.http://docs.lib.purdue.edu/iracc/200A DROP-IN CFC-12 REPLACEMENT FOR AUTOMOTIVE AIRCONDITIONING by George B. Goble 286 W. Navajo w. Lafayette, IN 47906 ABSTRACT There currently exists a large number (millions) of automobiles with air conditioning systems designed to use CFC-12 as the refrigerant along with plans to produce ~uch systems into the 1992-1995 time frame. During the 1992-1995 period, new production will transition to HFC-134a refrigerant based systems or other technologleS which offer zero or llttle ozone depletion. CFC-12 based systems will finally cease production around 1995, but they will have a lifetime of about 10 years, extending the need for CFC-12, or a substitute until the year 2005 or so. This paper will present a ternary blend of refrigerants which may be able to be used as a transitlon refrigerant in CFC-12 designed automotive air conditioners until HFC-l34a and other technologies are able to take over. Performance, oil miscibllity, flammability, toxicity, and testing with a commercial dehydrant/leak sealant wlll be discussed. INTRODUCTION A ternary blend of HCFC-22, HCFC-142b (chlorodifluoroethane), and small amount of R-600a (isobutane) has been found to provlde acceptable operation on several automoblle airconditioning systems designed for use with CFC-12. Some capacity increase has been noted in most systems, probably from the blend being non-azeotropic, leading to better utilization of the condenser and evaporator [1]. This blend features 95% less ozone depletion potential (ODP) than does CFC-12 (ODP of 0.05 vs CFC-12 with ODP 1.0). This blend is 55% HCFC-22, 37% HCFC-142b, and 8% isobutane by weight and is compatible with m1nera1 a1ls currently used in CFC-12 systems. Test~ng began in August 1990 in two vehicles, a 1990 Pontiac Trans-sport, and a 1978 Datsun 810. A 1979 Grand Prix was added ln October 1990. By March 1992, some 150 vehicles were running th1s blend~ Only one failure has occurred. A 1984 Bulck Century had a DA-6 compressor fall. The tear down of the compressor revealed the thin Teflon plston rlngs had broken, and fragments had lodged in the valves, holding them open, Local mechanlCS state this is an extremely common failure mode for this compressor (with R-12), and one mechanic reported he changed 38 DA-6 compressors in a two month period during the summer of 1991 which had falled for the same reasons. The rerna1ning intact Teflon piston rings~ did not appear to be swollen or affected by th1s blend. Currently~ theLe 1s no ~eason to suspect this blend as being the cause of thls failure. The first cwo veh1cles were instrumented wlth gauge manifolds (all copper lines) in the passenger compartment along with thermocouple probes, so temperatures and pressures could be monitored in real life drivlng situations. The 1990 Transsport, ran the standard CFC-12 charge for the first year of its life, it then was charged with the ternary blend. After 8 months no loss of charge was noted from performance and pressures. Refrigerant has remained clear and dry as observed in an installed liquid line sight glass. PERfORMANCE Testing of this blend has shown significant (around 2-7,C) decrease ln discharge air temperatures ac ambient temperatures over 27'C over thac of what CFC-12 did. Condensation and evaporation of the refrigerant appear to occur over a larger band or "glide", thus achieving better utilization of the evaporator and condenser. At lower ambients, the capacity (cooling) of this blend drops off to approximately that of CFC-12, mostly from the reduc-tion in head pressure. Different systems perform differently. CCOT (ori-fice) systems generally show more increase in capacity than do expansion valve systems. Compressor discharge temperatures d~d run sl~ghtly higher 607 than with R-12. Hot ambient (32-J~ ° C) days produced d~scnarge temperatures inothe aooc range. The same syst@mS had R~l2 discha~ge temperatures in the 70 C range (average city driving). Even though. slightly higher, the compressor discharge line temperatures are still low enough to prevent refrigerant/oil breakdown. OIL MISCIBILITY In addition to refrigerat~on effect, the isobutane makes this blend miscible in standard mineral oils used in CFC-12 systems. Neither HCFC-22 nor HCFC-142b by itself are very miscible with mineral ails used in CFC-12 systems at evaporator temperatures (O'C). The "Upflow" evaporators and large diameter suction lines commonly found in R-12 systems may cause problems with o~l return to the compressor, resulting in compressor failure, when the refrigerant is not miscible in the 011 being used (2] . This blend stayed dissolved in oil (20% oil) by volume, at o'c (approx-imate evaporation temperature in auto A/C systems) with Suniso 5GS (525 SUS viscosity) mineral oil of the type used in auto A/C systems. Suniso 3GS (150 SUS v~scosity) mineral oil (naphthanic) and Virginia KMP 150 viscosity min-eral oil (paraffinic) also stayed dissolved in refr1gerant at O'C. Both 150 viscosity oils were completely dissolved at -lS'c. Around 10% (by volume) of Suniso 525 SUS viscosity oil dissolved 1n the refrigerant at -18'c. This 525 v~scosity oil is normally used in auto A/C systems wh~ch only operate at o<c or higher. Typically, around 10% by volume, oil is circulated with the refrigerant in auto A/C systems. FLAMMABILITY The current blend could not be ignited, even after a 4 month leak down test (over 1/2 the charge had been lost) . It should be noted that even CFC-12 can be "flammable", when it contains dissolved oil, and a rapid release occurs. The oil atom~zes into a fine mist and can be ignited. It has been reported that HC~C-22/HCFC-142b mixtures are nonflammable up to concentra-tions of 69% weight of HCFC-142b [3]. Many unonflammable'• refrigerants, which contain hydrogen atoms, can become flammable if mixed with large amounts of air under pressu~e. Such examples include HCFC-22 and HFC-134a. For this reason, this blend and other refrigerants and blends containing hydrogen atoms should not be · diluted with air, and pressurized (such as for leak test1ng), Diluting the refr~gerant with dry nitrogen ~s ok. Being a non-azeotrope, this blend will change composition during the leaking process. Recharg1ng (topping off), systems with partial charges is prohibited. The entlre charge must first be removed, and a recharge don~ with new (non recycled) material. Repeated topping off of leaking systems could lead to this blend becoming flammable, thus the requirement of always doing a full recharge with new material. This requirement should not impact automotive air conditioning severely. This difficulty rapidly becomes pro-hibitive in large commercial systems, where topp~ng off leaking systems is the normal mode of operat~on. Non-azeotropic blends will be cumbersome in anything except automotive and small systems due to the requirement that the whole charge be removed. Reconstitution of leaking non-azeotropic blends to known composition is beyond the scope of almost all service technicians. TOXICITY Unlike the new genel:"ation of "hyperfluorinat.ect•• refrigerants, all of the ingredients of this blend have existed for decades and their propert~es are well known. HCFC-142b is commerc~ally available in large quantities. LEAKING AND LEAK SEALING IN CARS !t has been observed, that a large percentage of older (4 years or older) cars, seem to have continual slow refrigerant leaking problems. Even when the leaks are identified and repaired, many are low on charge by the following summer. New leaks form, and/or hose d1ffusion may be occurring 60B and may be undetectable due to the large surface areas or difficult to access areas. Airconditioning serv~ce shops, often can only repair uobvious 11 leaks or change 11 bad 11 components. Some leaks have been observed to be temperature sensitive (e.g. only leaks in the winter when parts contract) Many cars are continually recharged at 2 month to 1 year intervals; since the leaks are impossible to find/repair. Many owners of older cars are not willing to pay the cost of an entire new system be~ng installed (often over $1000), JUSt because the leaks cannot be found and repaired. State laws are being enacted (such as Florida, 7/1/91), which prohibit auto-mobiles from 1eav~ng a serv~ce shop unless the leak is repaired. If the leak is not repaired, then the CFC-12 must be removed from the system before ~eleasing the car to the owner. Mechanics have report@d to the author that they have encounte~ed certain brands of connectors which always leak small amounts of charge, even if they are new and this has led to much frusLration as they cannot be properly Jjfixed~'. A commercial silane based dehydrant and sealantJ has been tes~ed with this blend. System drying and sealing of leaks has been observed to be sat-isfactory for the two week to 1 year "leak rates". This also stopped dif-fus~on through hoses and helped prevent composition changes in the blend due to leaking. Elimination of constant recharging reduces the "effective" (per car) ODP further. If a car ''saves'' five additional recharges in 1ts llfe-t1me, then the effective ODP becomes 0.01 for a 99% reduct~on in ozone de-pletion from R-12. Shaft seal leaks were not repaired, but they were reduced. Use of thlS sealant requires the system be 11 dry'', w1th no s~gnif­icant moisture trapped in the dr1er. The sealant manufacturer requires that the drier be changed prior to use. Experience has found this to be tru_e. Using this blend (~ith sealant) on ·~et" systems (without changing the drier), resulted in the sealant be1ng neutralized and no sealing action. No harm was caused be this action oLher Lhan sealant being wasted. The systems continued to perform (and leak) normally. Changing the drier and orifice are always good refr1gerat1on practices. Old driers can have their desiccant bags break, and clog the system w~th clay from the desiccant binder. PROCEDURES Being a non-azeotropic blend, certain procedures must be followed to prevent composition changes. The mos~ obvious is that the system mus~ be "liquid charged", carefully to avoid slugging the compressor. Systems w~th partially leaked charges, should be discharged before recharging, to ach1eve a known composition. This problem is greatly reduced by the addition of th'e above sealant. Under the "1990 Clean A~r Act", this blend cannot be vented to the environment after certain dates (mostly in 1992), depending on ~he type of serv1ce (mobile airconditioning, fixed, size of service shop, etc). It can be ii:recovered" (pumped 1nto a tank) with CFC-12 rec:overy equipmenr. and returned to Lhe manufacturer to be reclaimed to new standa~ds or be destroyed, it cannot be reused on site. CONCLUSIONS The author believes this blend can be used to keep ex1st1ng and future CFC-12 automotive airconditioning systems runn1ng until they reach their normal end of life. This blend may take some pressure off. the race to get HFC-134a, its complex lubricants and field procedures operational, for retrofitting existing CFC-12 systems which fail in the field. Be1ng a blend~ '•custom" ref:rige:rants can be made for extra performance in hot humid climates with minor system modifications (a high pressure cutout switch) . Testing is currently ongoing in this area. It is possible to del1ver sub-freezing air continuously at ambients of 38°C (highway driving). US and foreign patents pending. REFERENCES [1] Kruse,. H. 11 The advantages of non~azeotropic refrigerant mixtures for heat pump applications" Int. J, Refrig. 1981 vol 4 May pp 119-125 [2) ASHRA~, 1984 Systems Handbook, pp 29.11 [3] Kuijpers, L., M1ner, S., '"rhe CFC issue and the CFC foz:um at the 1988 Purdue IIR conference", Int. J" Refrig. 1989 vol 12 May pp. 123 609 

A Drop-In CFC-12 Replacement for Automotive Airconditioning

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A Drop-In CFC-12 Replacement for Automotive Airconditioning

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