Performance of DuPont ISCEON MO99 refrigerant (R · PDF fileMinimal TXV or Control Setting...

Dr. Charles C. Allgood and C. Curtis Lawson DuPont Chemicals and Fluoroproducts Wilmington, DE, USA

13th International Refrigeration and Air Conditioning Conference at Purdue University, West Lafayette, IN 12-15 July 2010

Performance of DuPont™ ISCEON® MO99™ refrigerant

(R-438A) in R-22 refrigeration and air conditioning systems

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Agenda

Refrigerant Properties Refrigerant Performance

•  Lab Tests •  Field Retrofits

Oil Management Considerations •  Solubility/Viscosity •  Oil Return Tests

Summary and Conclusions

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R-438A: Retrofit Refrigerant for R-22 HFC/HC Blend: R-32/R-125/R-134a/R-600/R-601a

(8.5/45/44.2/1.7/0.6) ASHRAE Designation: R-438A

ASHRAE Safety Classification: A1

ODP: Zero

GWP: 1890 (SAR), 2264 (AR4)

EPA SNAP Listed: Yes

UL Certification: Yes

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R-438A: Key Advantages Similar Pressure-Enthalpy Characteristics to R-22 at Low, Medium, and High Temperature Conditions

•  Use Existing TXVs, Line Sets

Compatible with MO, AB, and POE Lubricants •  No Lubricant Change Needed in Most Systems

Uses standard HFC compatible filter driers, leak detectors, seals/gaskets

•  Change critical elastomeric seals/gaskets exposed to R-22

R-438A Provides a Low Cost option for retrofit of R-22 Direct Expansion Refrigeration and Air Conditioning Equipment

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R-438A Material Compatibility Similar elastomer, plastic, and metal material compatibility as other HFC refrigerants Elastomeric seals and gaskets previously exposed to R-22 have higher potential as possible leak sources in HFC Retrofit

•  Elastomer aging can cause embrittlement, deformation of seal •  Less elastomer swell with HFCs

Recommend replacing critical elastomeric seals and gaskets on retrofit to any HFC, including R-438A

•  The older the system, the higher probability of leaks •  Common leak sources are seals on Schrader cores, ball and

solenoid valve stems, liquid receiver gauges

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Evaporator Pressure Comparison (based on 40.6°C Average Condenser T; subcool liquid to 35°C)

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Condenser Pressure Comparison (based on -6.7°C Avg Evaporator T; 5.6°C subcooling from Avg

Condenser T)

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R-438A Capacity Comparison

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R-438A COP Comparison

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Summary: R-438A Performance Relative to R-22 LT MT HT

Capacity (%) - 6 -8 -7

COP (%) +7 -1 -2

Suction P (kPa) -14 -21 -21

Discharge P (kPa)

+21 +21 +34

Discharge T(°K) -12* -23 -17

Temperature Glide (°K)

+3.6 +3.3 +3.9

LT: -31.7°C avg evap T, 40.6°C avg cond T, 18.3°C return gas T, 5.6°C subcool from avg cond T MT: -6.7°C avg evap T, 40.6°C avg cond T, 18.3°C return gas T, 5.6°C subcool from avg cond T HT: 7.2°C avg evap T, 46.1°C avg cond T, 18.3°C return gas T, 8.3°C subcool from avg cond T *Assumes liquid injection to maintain maximum of 135°C discharge T

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R-438A Field Retrofits Wide Range of Direct Expansion R-22 Equipment

Successfully Retrofitted with R-438A:

Commercial Air Conditioning •  Roof Top Units •  Indoor Packaged Units •  DX Chillers •  Split Systems

Residential Air Conditioning Refrigeration (Low and Medium Temperature)

•  Self Contained Systems •  Condensing Units •  Rack Systems

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R-438A Field Retrofits Field Results similar to Lab Results

•  Similar COP •  5-10% Lower Capacity •  Similar Case Temperatures

No Oil Change in Most Systems •  Good Oil Return in Systems with Oil Separators •  10-20% POE addition recommended in Systems with Liquid

Receiver & No Oil Separator

No TXV or Line Set Changes Minimal TXV or Control Setting Adjustments Recommend Replacement of Critical Elastomeric Seals in any HFC retrofit

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Energy Consumption Comparison Rooftop A/C Unit

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Energy Consumption Comparison Rooftop Condensing Unit

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Energy Consumption Comparison Supermarket Rack

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R-438A/MO – Oil Management Considerations 1)   Oil Solvency

•  POE has higher solvency power than MO •  Higher solvency oil can “scour” debris and carbon deposits

and cause plugging of valves and filters

2) Oil Solubility in Refrigerant •  Primary Method of Oil Return from Liquid Receiver •  Systems with high oil discharge and no oil separator and a

liquid receiver may need a small amount of POE (10-20%) to assist oil return

3) Oil Viscosity •  Solubility/Miscibility of refrigerant in oil lowers viscosity of oil/

refrigerant mixture •  Small % HC in R-438A lowers MO or AB viscosity in cold

evaporator

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Oil Solvency Power of POE vs MO

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HFC/MO (R-407A/3GS)

HFC/HC/MO (R-438A/3GS)

Oil Viscosity vs. Temperature for HFC(HC)/MO

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R-438A/Mineral Oil – Oil Return Testing

Testing Objectives: Determine Impact on Oil Return for R-438A/MO in A/C systems under challenging operating conditions : 1. Variable Line Velocities (2-12 m/sec) 2. Excessive Oil Discharge from Compressor 300 cc out of 950 cc (~30%) slug

3. Floodback Conditions - Liquid Refrigerant in Accumulator

Note: Tests 1 & 2 at AHRI Cooling “A” Conditions; Test 3 at Low Temperature Heating Mode

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Test Setup for Oil Return Tests Outdoor Room Indoor Room

Condensing Unit

Variable Size Suction Riser 1.9 cm ( ¾”) - ~11.7 m/sec (Typical Velocity) 2.85 cm (1-1/8”) - ~ 5.1 m/sec (Design Limit) 4.13 cm (1-5/8”)- ~2 m/sec (Low Velocity)

Accumulator

Discharge Line

Condenser

Compressor Oil Sump

Level

Oil Injection Bomb Liquid Line

From Evaporator

To Evaporator

Oil Injection Manifold

Not to Scale

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Accumulator and Compressor Modified w/ Level Tube and Video Camera

Compressor Sump Oil Level

Accumulator Liquid Level

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Oil Return Testing for R-438A

1. Impact of Line Velocity

Objective: Study oil return for non-miscible lubricant-refrigerant pairs (e.g. R-438A/MO) under typical and poor line velocity conditions.

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R-438A/3GS Oil Return – Line Velocity Tests

-Install Desired Suction Line Riser for test Condition: Test Condition Line Size Line Velocity “Typical” ¾” (1.9 cm) ~ 2300 ft/min (11.7 m/s)

“Low Design Limit” 1-1/8” (2.85 cm) ~ 1000 ft/min (5.1 m/s)

“Below Design” 1-5/8” (4.13 cm) ~ 400 ft/min (2.0 m/s)

-Evacuate system, charge system with R-22 (R-438A) and 3GS Oil (950cc) -Set Test Chamber for ARI Cooling “A” Conditions

-Start up system, monitor oil level in compressor sump via level tube

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Oil Return Test Results - Typical Line Velocity

Typical Line Velocity

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Oil Return Test Results – Low Design Limit Line Velocity

Velocity at Low Design Limit

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Oil Return Test Results – Below Design Line Velocity

Velocity Below Design Limits

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Oil Return Testing for R-438A

2. Impact of Large Oil Discharge Event

Objective: Study oil return after a large quantity of oil is discharged out of compressor for non-miscible lubricant-refrigerant pairs (e.g. R-438A/MO) at typical and poor line velocity conditions.

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Oil Return Challenge – Post Compressor Oil Injection Test Methodology

Outdoor Room Indoor Room

Condensing Unit

Accumulator

Discharge Line

Condenser

Compressor Oil Sump

Level

Oil Injection Bomb

Liquid Line

From Evaporator

To Evaporator

Monitor Compressor Sump Oil Level Over

Time

Not to Scale

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R-438A/3GS Oil Return – Oil Injection Tests -Install Suction Line Riser for test Condition:

Test Condition Line Size Line Velocity “Typical” ¾” (1.9 cm) ~ 2300 ft/min (11.7 m/s)

“Low Design Limits” 1-1/8” (2.85 cm) ~ 1000 ft/min (5.1 m/s)

“Below Design” 1-5/8” (4.13 cm) ~ 400 ft/min (2.0 m/s)

-Evacuate system, charge with R-22 (R-438A) and 3GS Oil (650cc out of 950cc only ) -Set Test Chamber for ARI Cooling “A” Conditions, Start up system, Monitor oil level in compressor sump via level tube

-Run for 4 hrs, Inject oil slug (300cc (30%)) into liquid line @ T= 240 min, Monitor oil level in compressor sump via level tube

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Oil Injection Test Results 30% of oil charge removed from compressor

and injected into liquid line

Typical Line Velocity

Velocity at Low Design Limit

Velocity Below Design Limit

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Oil Return Test Results – Post Compressor Oil Injection

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Oil Return Testing for R-438A

3. Study of Suction Line Accumulators

Objective: Investigate potential for non-miscible lubricant-refrigerant pairs (e.g. R-438A/MO) to potentially trap oil in suction line accumulators by formation of a two phase mixture.

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Oil and Liquid Refrigerant Return via Orifice

Vapor Return

From Coil

To Compressor

R-22/MO R-438A/MO

Can a two phase mixture be sustained in the Accumulator

and trap oil ?

?

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Impact of Suction Line Accumulators on Oil Return for R-438A/MO

Test Considerations:

•  Similar to Issue in Liquid Receivers, but •  Accumulators designed for liquid return (orifice) •  Accumulators designed for transient operation

•  Worst case: Flood back conditions i.e. Heat pump in Low Temperature Heating mode

Experiments: •  Modify Accumulator for Visual Observation •  Also Measure Compressor Sump Oil Level •  Test at Worst Case Conditions •  Force Flooding of Suction Accumulator by TXV and/or overcharging

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Accumulator Floodback Test Conculsions

Compressor • Compressor Sump Oil Levels remain Stable w/flooded Accumulator

Accumulator • Turbulent Mixing/Boiling/Agitation • Constant Rising/Falling Liquid Levels • Difficult to accurately measure Levels

• No Phase Separation Observed while System On • Small Oil Heel Remains in Accumulator (below level of orifice) independent of oil/refrigerant pair

System • Stable Operation with both R-438A/MO and R-22/MO

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Accumulator Floodback Test Steady - State Heating Mode (-1°C/21°C)

R-438A/MO

R-22/MO

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Oil Return Tests - Results and Conclusions

R-438A/Mineral Oil maintains compressor oil levels despite:

•  Poor line Velocities

•  Large oil discharge rates

•  Flooded Suction Line Accumulators

Majority of oil slug returns very quickly •  Last traces return as well over time • 

R-438A/MO and R-22/MO steady state oil levels differ slightly, but both provide adequate compressor lubrication

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Summary and Conclusions R-438A is Low Cost Option for Retrofit of R-22 Direct Expansion Refrigeration and Air Conditioning Equipment

•  Similar Performance to R-22 •  Non-Ozone Depleting •  Nonflammable

Similar Pressure-Enthalpy Characteristics to R-22 at Low, Medium, and High Temperature Conditions

•  Use Existing TXVs, Line Sets •  Minimal Adjustments to Settings

Can be used with MO, AB, or POE Lubricants •  No Lubricant Change Needed in Most Systems

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