MODELLING OF MOBILE AIR- CONDITIONING SYSTEMS FOR ELECTRIC VEHICLES

Transcription

1 MODELLING OF MOBILE AIR- CONDITIONING SYSTEMS FOR ELECTRIC VEHICLES 4th European Workshop MAC and Vehicle Thermal Systems 2011 B. Torregrosa, J. Payá, J.M. Corberán Torino, December 2 nd, 2011

2 Content Motivation Objectives Models Results Conclusions 2

3 Motivation Motivation Objectives Models Results Conclusions Recent support of electric vehicles (EVs) (EU: 7th Framework Programme, national EV development plans) From NREL estimations, up to 20% increase in fuel consumption due to MAC in summer Limited waste heat available from the EV motor (2-3 40ºC) for heating and defogging in winter MAC causes a large shortening of EV autonomy Need for: Tools to assist MAC design Efficient MAC technologies 3

4 Objectives Motivation Objectives Models Results Conclusions ICE Project: develop an innovative Mobile Air Conditioning system for an EV Magnetocaloric heat pump technology Innovative design and control of the thermal power distribution loop Development of models to assist the design of MAC systems Thermal load calculation Heat pump and HEXs performance Selection of equipment Parametric studies Optimisation of MAC system and EV autonomy 4

5 Motivation Objectives Models Results Conclusions Overall model I v T AC T AC P T e, RH e T pass RH pass T driv RH driv H P EL INPUTS External conditions Speed (driving cycle) Control settings (target T) MAIN OUTPUTS Car cabin temperature and RH AC outlets temperature Power consumption 5

6 Motivation Objectives Models Results Conclusions Overall model Supply water flow Supply water T Supply air flow Supply air T HEAT PUMP ELECTRICAL SYSTEMS Set point Car speed RADIATOR LOOP Return water T Amb. Supply air RH CABIN Cabin air T (multizone) AMBIENT Air temperature Air relative humidity Solar irradiation Ambient Car speed Cabin air RH (multizone) 6

7 Cabin model Motivation Objectives Models Results Conclusions Simulation of the car cabin s thermal behaviour Two zones: driver and passengers Inertia of seats and car body I G e,pass I S eq,b,pass I S eq,b,driv G pass G mass,pass Q I S eq,pass (1-α) m AC,driv I S eq,driv G driv G e,driv m AC,pass m AC,pass m ψ α m AC,driv m v m pass,e m driv,pass m r,driv PASSENGERS DRIVER 7

8 Cabin model Motivation Objectives Models Results Conclusions 0D model based on energy and mass balances. Each zone: 4 differential equations DRIVER ZONE CAR BODY Inertia of the car body Heat transfer Heat transfer Solar irradiation between car body between car body absorbed by the car and cabin air and outside air body 8

9 Cabin model Motivation Objectives Models Results Conclusions 0D model based on energy and mass balances. Each zone: 4 differential equations DRIVER ZONE CAR BODY CABIN MASSES Inertia of the cabin masses Solar irradiation absorbed by the cabin masses Heat transfer between cabin masses and air 9

10 Cabin model Motivation Objectives Models Results Conclusions 0D model based on energy and mass balances. Each zone: 4 differential equations DRIVER ZONE CAR BODY CABIN MASSES CABIN AIR TEMPERATURE Inertia of Supply air flow Return air flow Heat transfer the cabin air between car body Heat transfer Sensible load Air from flow between Air flow between and cabin air between cabin passengers driver zone and driver zone and masses and air passengers zone due passengers zone due to stack effect to AC distribution 10

11 Cabin model Motivation Objectives Models Results Conclusions 0D model based on energy and mass balances. Each zone: 4 differential equations DRIVER ZONE CAR BODY CABIN MASSES CABIN AIR TEMPERATURE CABIN AIR HUMIDITY Humidity of the air flow due to Change stack in cabin effect air humidity Supply air flow humidity Humidity of the air Return air Water flow vapour from flow due to AC humidity passengers (latent distribution load) 11

12 Cabin model Validation Motivation Objectives Models Results Conclusions Pasajeros 2 kw 2 kw 12

13 Motivation Objectives Models Results Conclusions Heat pump model Efficient reversible heat pump for EV Condenser brazed plate HEX refrigerant-to-water Compressor scroll type variable speed R134a Detailed modeling of each component using IMST-ART. Physical and performance based models Losses in pipes and valves Assembling of single components to form the heat pump Evaporator microchannel HEX refrigerant-to-air Liquid-to-suction HEX 13

14 Motivation Objectives Models Results Conclusions Heat pump model Efficient reversible heat pump for EV T out,cond P, COP INPUTS Secondary flows Secondary inlet T Control settings T out,evap MAIN OUTPUTS Secondary outlet T Power consumption Performance Assembling of single components to form the heat pump 14

15 Motivation Objectives Models Results Conclusions Heat pump model Heat exchangers Physical based 1D models PLATE HE IMST-ART COIL HE 15

16 Motivation Objectives Models Results Conclusions Heat pump model Compressor Variable speed, scroll type Performance based model Comp. eff. Compressor efficiency ε = f(r p, n) VALIDATION Speed (rpm) Pressure ratio Volumetric efficiency η v = f(r p, n) Vol. eff. Speed (rpm) Pressure ratio 16

17 Motivation Objectives Models Results Conclusions Heat pump model Validation Winter IMST - ART TEST Temperature [ C] T air radiator T water T outlets 2000 rpm 3000 rpm Time [min] 4000 rpm 5000 rpm 6000 rpm Externa Temperature 10.0 C Fresh Air Mode Max. dev. = 3.3% Air flow = 505 scm/h Water flow = 2 m 3 /h 17

18 Heat pump model Validation Summer Motivation Objectives Models Results Conclusions Temperature [ C] C TEST External Temperature 35.0 C Fresh Air Mode Outlet mean 17.5 C Time [s] IMST - ART Compressor at full speed Air temperature = 17.1 ºC Deviation = 2.3% Air flow = 505 scm/h Water flow = 2 m 3 /h 18

19 Motivation Objectives Models Results Conclusions Radiator loop model Simulation of the external loop of the heat pump Te, RHe T r v INPUTS Heat to the external loop Coolant mass flow External conditions (T, RH) Speed (driving cycle) T s MAIN OUTPUTS Supply and return temp. Radiator s thermal power 19

20 Motivation Objectives Models Results Conclusions Radiator loop model Simulation of the external loop of the heat pump Inertia and losses Effectiveness method Sensible and latent processes QQ rrrrrr = mm aaaaaa εε h aaaaaa _iiii h ssssss _II 20

21 Radiator loop model Radiator model Motivation Objectives Models Results Conclusions Performance based model HEX can be scaled up or down * * ESDU 86018, Effectiveness NTU Relationships for the Design and Performance Evaluation of Two-Stream Heat Exchangers (1991) 21

22 Motivation Objectives Models Results Conclusions Results Thermal load WINTER Outside: T=0ºC I=0 Comfort: DRIV: T=20ºC PASS: T>10ºC 7 passengers + driver DRIV: Fresh air PASS: Full recirculation No dehumidification ICE PROJECT DESIGN CONDITIONS SUMMER Outside: T=35ºC RH=60% I=0 Comfort: T=25ºC RH<50% 7 passengers + driver Full recirculation LOAD (kw) WINTER SUMMER STEADY WARM UP 1h STEADY COOL DOWN 1h Driv Pass Driv Pass Driv Pass Driv Pass SENSIBLE LATENT TOTAL , SHR 83%

23 Motivation Objectives Models Results Conclusions Results Thermal load WINTER Outside: T=0ºC I=0 Comfort: DRIV: T=20ºC PASS: T>10ºC No passengers Time to target: 1h No dehumidification HARDEST OCCUPANCY CONDITIONS SUMMER Outside: T=35ºC RH=60% I=0 Comfort: T=25ºC RH<50% Full occupancy Time to target: 1h LOAD (kw) WINTER SUMMER FRESH AIR FULL RECIRCULATION % - 68% 23

24 Motivation Objectives Models Results Conclusions Results Heat pump performance WINTER: 0ºC/80%RH Outside: T=0ºC I=0 Comfort: T=20ºC 7 passengers + driver Fresh air No dehumidification Heating power : 5.12 kw Electric power : 1.65 kw COP 3.1 Energy consumption 0.54 kwh Heat pump compressor Electrical resistance Magnetocaloric system (expected) kwh Autonomy % % % 24

25 Motivation Objectives Models Results Conclusions Results Heat pump performance SUMMER: 35ºC/60%RH Outside: T=35ºC RH=60% I=0 Comfort: T=25ºC RH<50% 7 passengers + driver Full recirculation Cooling power : 2.84 kw Electric power : 0.78 kw COP 4.0 Heat pump compressor Magnetocaloric system (expected) kwh Autonomy % % Energy consumption 0.25 kwh 25

26 Conclusions Motivation Objectives Models Results Conclusions A powerful but simple model of a Mobile Air-Conditioning system for an EV has been developed The model shows very good agreement with experimental data from the IVECO Daily minibus The results are very useful to predict the thermal load, heat pump performance and help with the sizing of the components MAC has a great impact on the autonomy of EVs. Both the technologies and operating conditions must be chosen carefully: Efficient MAC technologies such as heat pumps: - 8 to 14% autonomy Air recirculation with efficient heat pumps: - 4% autonomy Expected results with magnetocaloric heat pump: - 2 to 4% autonomy Next steps: Including auxiliary systems (pumps and fans) energy consumption Waste heat from electrical systems Magnetocaloric heat pump 26

27 THANK YOU FOR YOUR ATTENTION 4th European Workshop MAC and Vehicle Thermal Systems 2011 Torino, December 2 nd, 2011