Improvement of Power Saving in R134a Air-Conditioning System

Improvement of Power Saving in R134a Air-Conditioning System Masahide Ishikawa, Takayoshi Matsuno, TOYOTA MOTOR CORPORATION Kazuhito Miyagawa, DENSO CORPORATION 1

Presentation Outline Impact of A/C on Fuel Consumption Approaches to A/C Power Saving - A/C Cycle & System Efficiency Improvement - A/C Control Efficiency Improvement - Coordination With Powertrain - Vehicle Thermal Management Improvement 2

Influence of A/C on Fuel Consumption Fuel Consumption (km/l) 15 Actual Running Mode: 9 % Compact Car LA4: Stop Ratio 17% Yearly 10 5 A/C Off A/C on (yearly) Compressor (39) Temperature ( o C) Humidity (%) Sun Load (W/m 2 ) Fresh / Recirculated Air Blower Speed Evaporator Outlet Air Temperature ( o C) Clutch (3) Cooling Fan (9) Blower (38) Idle up (11) Fuel Consumption Increase Ratio (%) 25 50 0 Fresh Low 10 Yearly (9%) Impact on Fuel Consumption Components Compressor, Condenser, etc Influence of Vehicle Thermal Management Running Condition Constant Speed, Acceleration/Deceleration Idling, Electric load is also a major item. 3

Compressor (39) Impact on Fuel Consumption 9 38 3 11 Yearly (9%) Increase Evaporator Inlet Air Temperature (5-10 o C) (4) Assumption by Thermal Data at Re-Entry of Heated Air (10-15 o C) (4) Idling and 40 km/h Running Fuel Consumption Increase Ratio (%) Thermal Management Improvement: Evaporator Air Inlet Temperature Reduction Preventing Hot Air Recirculation Constant Speed 22 Accelerating 22 22 38 Decelerating Idling 38 18 0 25 50 75 100 Fuel Consumption Increase Ratio (%) LA4 Yearly (9%) Large Effect When Idling and Decelerating (Accelerating In Summer) A/C Control Considering Running Condition Coordination Control with Powertrain 4

Approach to A/C Power Saving Impact on A/C Fuel Consumption A/C Cycle, System & Components Running Condition Vehicle Heat Personal Preference A/C Cycle & System Efficiency Improvement (including components) A/C Control Efficiency Improvement Coordination with Powertrain Thermal Management Improvement 5

A/C Cycle System Efficiency Improvement Subcool Cycle & Improvement of Subcool condenser Improvement of Compressor s Efficiency & Variable Displacement Compressor System A/C Control improvement Coordination with Powertrain Vehicle Thermal Management Improvement 6

180 160 Condenser Efficiency Improvement Q/F = Performance/(core width x core height) High-performance Subcool Subcool type 140 Multi-Flow Q/F 120 100 Serpentine 80 60 40 1980 1985 1990 1995 2000 2005 2010 7

Operating Principle of Subcool Cycle Subcooling Pressure Subcool Reciever Condenser Increase In Effective Refrigerant GAS Exp.Valve Evaporator Compressor Liquid Improved Cooling Performance Enthalpy 8

Effect of Subcool Condenser 10% Power Saving For Equivalent Performance Subcool Condenser Cooling Performance (kcal/h) 4500 4250 11.8% 5.7% Multi-Flow Condenser Power Consumption (PS) 2.0 1.5 780 10% 600 700 800 Compressor Speed (rpm) 9

Condenser Performance Improvement Mollier Diagram Subcool Effect Subcool Q Q Q + Q Subcool Effect Gives Q Extra Cooling 1. Enhance Heat Transfer (Improved Tube & Fin Efficiency) Conventional 16 mm 1.7 mm 7.8 mm Newest 1.0 mm 5.4 mm 16 mm (approximate dimensions) Compressor Load Ratio Effect 100 90 80 11% Down 2. Increased Core Effective Area Conventional Newest Tank Height Side Plate Height Old Current 10

Compressor Efficiency Improvement Compressor Efficiency (%) 0.7 0.6 0.5 0.4 Latest Compressor Exceeds 70%. HFC134a 1980 1985 1990 1995 2000 Year 2005 11

Continuously Variable Displacement Compressor Max Displacement Piston Piston Stroke Max Pd Ps Pc Control Valve Pc = Ps Piston Stroke Partial Displacement Piston Stroke Max~Min Pd Shaft Swash-Plate Control Valve Ps Pc Control Valve Pc Ps Piston Stroke 12

Characteristics of Variable Displacement Compressor Analysis Method Divide into Compressor Efficiency and Cycle Performance practice practice Isentropic Process theory practice System Comp. efficiency ad Pd Td Ps Ts theory practice Pressure 13 theory Cycle enthalpy Variable Displacement Comp System is improved.

Effect of Variable Displacement Compressor System Torque 0 100%/ON-OFF Variable Displacement Comp. Torque Better In the performance controlled region, the variable displacement compressor system shows a better performance than the fixed compressor system 14

A/C Cycle System efficiency improvement A/C Control improvement Power saving control Humidity control Coordination with Powertrain Vehicle Thermal Management Improvement 15

Power saving Control using external variable compressor Conventional Control (Internal Variable Compressor) Temp. Tin Evap. Tin 20deg. Te Te 3deg. H/C Tout Tout 15deg. Economy Control Logic TEO ( o C) Target of Air Temp. after Evaporator Demist Power Saving Comfort Humidity 15 External Variable 10 Current: 5 Internal Variable 0 0 5 10 15 20 25 30 35 Ambient Temperature TAM ( o C) Power saving Control (External Variable Compressor) Temp. Evap. H/C Tin Te Tin 20deg. Te 12deg. Tout Tout 15deg. Effect Power Consumption ratio 1 0-30% Economy Conventional 16

Absolute Humidity(g/kg ) 25 20 15 10 5 0 Humidity Control (1) Relative Humidity 100% 80% 60% 40% 20% 0 5 10 15 20 25 30 Temp. Cowl adopted by PRIUS Dehumidify Heater core Evaporator Blower Compressor Condenser -Control the outlet air temp. & humidity by changing the evaporator temperature (TEO) 17

Configuration Ambient sensor High-side Pressure sensor Exp. Thermistor Evap out Air temp Te High pressure Ph Ambient temp Ta A/C Switch Condenser Evaporator Humidity Control (2) A/C ECU Calculate: Duty ratio Comp power Cabin temperature and Humidity 18 Comp. Control Valve Evap out air temp. ( ) 12 0 Effect Windshield humidity target: 90% Demist Demist Line Minimum dehumidification Cabin humidity Target: 60% Humidity Comfort Zone w/o Humidity control No Reheat With Humidity control 0 5 15 25 35 Ambient temperature ( ) w/o Humidity Control With Humidity Control Conditions: 25 C-50% Blower: M1-20% 0 1 Power Consumption Ratio

A/C Cycle System efficiency improvement A/C Control improvement Coordination with Powertrain Vehicle Thermal Management Improvement 19

Coordination with Powertrain Approach Driving condition Driver s request Engine Output (Driving) Comp.Power Comp. Air-condition Cooperative control E/G-A/C with external compressor Compressor management Displacement Control due to Cooling performance Displacement control due to Compressor power 20

Control Pattern for Compressor Power Control Acceleration Control Cooling Performance Comp power consumption Reduce comp displacement during Acceleration Current (Ps control) New control Much Power saving with minimum performance reduction Time Deceleration Control Comp power consumption A/C fuel consumption Store the cool air during Deceleration (Displacement: Maximum) Fuel cut Store cold air Discharge the cold air Improve fuel consumption Time Vehicle speed Acceleration Cruising Deceleration Stop(Idle) Time Compressor is run for required cooldown performance with minimum power consumption. Idle speed is suitably controlled based on compressor power consumption. 21

A/C Cycle System efficiency improvement A/C Control improvement Coordination with Powertrain Vehicle Thermal Management Improvement Reduction of Vehicle Heat Prevention of Heated Air Re-entry into Condenser 22

Vehicle Thermal Management Improvement 1. Reduction of Vehicle Heat Load Heat Insulation (Roof) Heat Insulation (Pillar) Solar Radiation Absorption Glass (Rear) Solar radiation Absorption Glass (Side) Effect Item Heat Insulation (Roof, Pillar) Solar Radiation Absorption Glass (Rear, Side) Effect of Heat load reduction -6% -3% 23

Vehicle Thermal Management Improvement 2. Prevention of Heated Air Re-entry into Condenser Shutter Stops Heated Air Re-Entry Shutter Engine Heated Air Lower Cover Lower Cover Shutter Effect Condenser Inlet Air Temperature Reduced by 6 o C 24

Example of Application to Vehicle Power Consumption Ratio 1 0.9 0.8 0.7 0.6 0.5 Toyota COROLLA Nearly 20% Subcool System Serpentine Condenser Subcool Condenser Compressor Improvement ad 0.62 ad 0.68 1993 Model 2001 Power Consumption of Compressor After 30minutes at Idling 25

Summary Many A/C Power Saving Technologies Have Been Developed; A/C Cycle & System Efficiency Improvement A/C Control Efficiency Improvement Coordination With Powertrain Vehicle Thermal Management Improvement Some Already Adopted in Mass-production Vehicles Technologies Will Be Further Expanded in the Future. 26