M o n t r e a l P r o t o c o l, O E W G - 3 0, G e n e v a, 1 5 - 1 8 J u n e 2 0 1 0 1 XIX/8 Report on HCFC Alternatives for High Ambient Temperature.

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XIX/8 Report on HCFC Alternatives for High Ambient Temperature Regions

Lambert KuijpersRoberto Peixoto

TEAP, co-chairs UNEP Refrigeration TOC

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Decision XIX/8

At MOP-19 in Montreal, Decision XIX/8 was taken related to HCFC alternatives and specific climatic conditions:

To request the TEAP to conduct a scoping study addressing the prospects for the promotion and acceptance of alternatives to HCFCs in the refrigeration and air conditioning sectors in Article 5 Parties, with specific reference to specific climatic conditions and unique operating conditions, such as those in mines that are not open pit mines, in some Article 5 Parties;

To request the TEAP to provide a summary of the outcome of the study referred to in the preceding paragraph in its 2008 progress report with a view to identifying areas requiring more detailed study of the alternatives available and their applicability

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Status 2010

Decision XIX/8 asks for guidance on the replacements for HCFC-22, which is a commonly used refrigerant under hot ambient conditions

An RTOC sub-committee was assembled Delay in 2008 was due to problems in gathering accurate

commercial product data from different countries Delay in 2009 was due to logistics, including difficulties

in organising visits to South African mines Final report review at TEAP meeting 2010

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High Temperatures in Many Places

Location 10 Years 20 Years 50 Years Phoenix, Arizona 47.5 48.2 49.2 Sacramento, California 43.5 44.5 45.7 Imperial, California 49.9 51.0 52.5 Salt Lake City, Utah 40.0 40.7 41.7 Las Vegas, Nevada 46.0 46.6 47.5 Bahrain Intl Airport 45.6 46.4 47.5 Kuwait Intl Airport 51.0 51.6 52.3 Jeddah, Saudi Arabia 47.7 48.9 50.4 Riyadh [ASUD AFB], Saudi Arabia 46.6 47.1 47.6

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• A wide variety of candidate refrigerants (HFC, HFC based blends, HCs) can replace HCFC-22 in very hot climates

• Refrigerant selection pays attention to:• Global Warming Potential,• Cooling capacity at elevated ambient

temperatures,• Energy consumption, energy efficiency and

related impacts on electricity supplies,• availability of the refrigerant alternatives and

suitable equipment.

Refrigerants for High Ambient Temperature Air Conditioning

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R-410A & R-407C Have Inferior Technical Performance to R-22 in AC

• In AC, the primary global replacement, especially for the dominant air-cooled designs, is R-410A

• One component of this blend, HFC-125, has a comparatively low critical point temperature (66oC), resulting in a rapidly declining capacity and efficiency as condensing temperatures approach the critical temperature of the blend

• The same effect occurs with the blend R-407C

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Elaborated Analyses

For AC, condensing temperatures have been varied between 35 and 65 C

65 C condensation may occur at ambient temperatures in the range of 45-52 C, if no precautions in design taken

Even if 65 C condensing temperature would lead to substantial efficiency and capacity decreases, note that this temperature will only occur during part of a season, leading to much lower impact on annual performance

Additional system design features (such as night operation combined with cold storage) have positive effects

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Refrigerant Efficiencies at Various Condensing Temperatures

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Refrigerant Condensing temperature (C) Refrigerant

35 40 50 60 65

HCFC-22 6.28 5.08 3.57 2.64 2.29 HCFC-22

HFC-32 6.03 4.85 3.35 2.43 2.09 HFC-32

HFC-134a 6.41 5.18 3.62 2.66 2.30 HFC-134a

HC-290 6.31 5.09 3.54 2.58 2.23 HC-290

R-407C 6.23 5.01 3.47 2.51 2.15 R-407C

R-410A 6.01 4.800 3.27 2.32 1.95 R-410A

HC-600a 6.54 5.30 3.74 2.78 2.42 HC-600a

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• Application engineers will need to oversize equipment to compensate for the reduced capacity at the design ambient temperature

• In most cases R-410A or R-407C will need to be sized 5-10% larger than HCFC-22 equipment to compensate for the lower capacity at ambient temperatures up to 50C

• The increased capital cost of oversizing the equipment will be about 3% for a 10% increase in capacity

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Refrigerants for High Ambient Temperature Air Conditioning

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The natural refrigerant HC_290 can replace HCFC-22 in low charge applications (small window and portable room air conditioners). When replacing HCFC-22 with HC-290 one needs to consider appropriate design changes to minimise the refrigerant charge of HC-290 to comply with the applicable codes and standards on refrigerant charges and flammability

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Refrigerants for High Ambient Temperature Air Conditioning

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HFC-32 and HFC-32 in blends are candidates for the longer-term replacement of R-410A

The refrigerant HFC-32 is very moderately flammable

HFC-32 has a GWP approximately one third of the GWP of R-410A and exhibits much better high ambient performance than R-410A

Design changes required to convert from R-410A to HFC-32 are minor

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Emerging Refrigerants for High Ambient Temperature Air Conditioning

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Refrigerants for High Ambient Temperature Refrigeration

• The primary global replacement for commercial refrigeration is R-404A. The two components of this blend are HFC-125 and HFC-143a, both having relatively low critical temperatures causing a rapidly declining capacity and efficiency as condensing temperatures approach the critical temperature of the blend

• The study examines the suitability of R-404A, HCs, CO2 and ammonia as candidate HCFC-22 alternatives for very hot climates

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• For stand alone equipment, in high ambient temperature conditions, one high-GWP refrigerant (HFC-134a) and three low-GWP refrigerants (HC-600a, HC-290 and possibly HFC-1234yf) can be used with the current refrigeration technologies

• For centralized systems, low-GWP toxic and flammable refrigerants can be used in indirect systems conditions because there is no significant variation of the evaporation temperature

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Refrigerants for High Ambient Temperature Refrigeration

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• HFC blends with high GWP, such as R-404A or even R-422D or R-427A can be used, but for those two blends the refrigerating capacity could be lower by about 5% and the efficiency could also be lower by 5-10%

• HCs, such as HC-290 and HC-1270, can be used at high ambient temperature since they exhibit relatively low discharge temperatures compared to HCFC-22. However, refrigerant quantities have to be limited for safety reasons

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Refrigerants for High Ambient Temperature Refrigeration

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The new low-GWP short-lived HFC-1234yf as well as new low-GWP blends can be expected to be commercialised during the next three years

These new low-GWP refrigerants might also be used in indirect systems or cascading systems with CO2 either as a refrigerant (in the low stage) or as a heat transfer fluid

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Refrigerants for High Ambient Temperature Refrigeration

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Refrigerants for Deep Mines

• The technology for deep mines is rather different than for high-ambient temperature operation

• The ambient heat rejection (refrigerant condensing) temperatures generally are less extreme in mines

• In addition, with low humidity, heat rejection typically employs water cooling towers rather than air-cooled condensers (i.e., the governing performance parameter is the wet-bulb rather than the dry-bulb temperature)

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Refrigerants for Deep Mines

A study tour of deep mines was made to South Africa in the second part of 2009

During the tour, leading mining companies, the engineering firms supporting them, researchers, and government contacts were consulted to verify the problems and confirm the solutions

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• Most newer mine chillers in the last decade have used HFC-134a, or ammonia (R-717)

• However, some older and some small mines use HCFC-22

• Some newer installations use HCFC-123 to attain high efficiencies

• Some recent systems use water (R-718) as a refrigerant in a vacuum, with a vapour-compression flash cycle to produce ice slurries directly

• Some proposed systems would use air (R-729) in air-standard reverse Brayton cycles

Refrigerants for Deep Mines

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Summary for both AC & Refrigeration

Some HFC blends that are alternatives for HCFC-22 have a low critical point temperature (66oC), resulting in a rapidly declining capacity and efficiency as condensing temperatures approach the blend critical temperature

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Summary (AC)

In most cases equipment using R-410A or R-407C will only need to be sized 5-10% larger than HCFC-22 equipment to compensate for the lower capacity at ambient temperatures up to 50C

As a HCFC-22 alternative, HC-290 is suitable in low charge applications (<250 g) with appropriate design changes to comply with all applicable codes/standards

HFC-32 is a candidate for the (longer-term) replacement of R-410A

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Summary (Refrigeration)

The use of indirect systems is possible at high ambient temperature conditions

R-404A, or even R-422D or R-427A can be used, but the refrigerating capacity and the efficiency would decrease by about 5% and 5-10%

HCs such as HC-290 and HC-1270 can be used in hot climates; they exhibit relatively low discharge temperatures compared to HCFC-22

The new low-GWP short-lived HFC-1234yf and new low-GWP blends can be expected during the next three years; they may also be used in indirect systems

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Summary (Deep Mines)

The ambient heat rejection (refrigerant condensing) temperatures generally are less extreme in mines. In addition, heat rejection typically employs water cooling towers rather than air-cooled condensers

Most mine chillers in the last decade have used HFC-134a, or ammonia (R-717)

HCFC-22 old chillers can be mostly replaced by HFC-134a and ammonia chillers