CO2 Air Conditioning and Heating applied to city buses (COACH)

Transcription

1 CO2 Air Conditioning and Heating applied to city buses (COACH) Dr.-Ing. Michael Sonnekalb (Konvekta) Dr.-Ing. Sven Försterling (TLK-Thermo) Dr.-Ing. Wilhelm Tegethoff (TLK-Thermo) VDA-Wintermeeting, Saalfelden, February 12th 29

2 Outline 1 Alternative heating concepts 2 Bus with heat pump test rig 3 Boundary conditions 4 Simulation model 5 Measurements 6 Simulation results 7 Summary

3 Alternative Heating Concepts Fuel based auxiliary heater PTC-element Glow plug Exhaust heat exchanger Viscous heater Latent heat-storage unit Heat pump 9 % 5 % a/c

4 Alternative Heating Concepts eff. work 4% exhaust gas 3% cooling system 2% coolant 24% natural convection + radiation 4% Heat balance of a modern truck-engine [Mollenhauer 27]

5 Alternative Heating Concepts HX ambient HX environment expansionvalve compressor 5 HX cabin HX passenger compartment 6 1 conventionally air conditioning system

6 Alternative Heating Concepts 4 HX passenger HX compartment ambient 3 3/2-way-valve 2 expansionvalve compressor 5 HX cabin 6 HX environment 3/2-way-valve 1 proposal for air-air-heat pump

7 Bus with heat pump test rig City bus MB O45, km, KL 6 AFT CO 2 field test since 1996 compressor hours 18 h a/c 3 h heat pump

8 Bus with heat pump test rig expansion valve Test-bus cabin hx compressor ambient hx 3-way-valve

9 Boundary conditions 1 8 speed gear 5 4 speed [km/h] gear [-] time [s] Driving cycle for city buses [Dreyer 1975]

10 Boundary conditions hours [h] hours sum 1% 8% 6% 4% 2% % Climate data [Kosowski] Climate data and usage behavior for vehicles in Europe: FAT-Study [Strupp]

11 Simulation model Engine Input: n M Parameter: characteristic Output: P_mech H_exhaust Q_cooling T_exhaust mdot_diesel n M Bus Input: w gear Parameter: mass Cw-value tyre friction Output: M n W gear Driving Cycle Input: city bus Parameter: driving behavior Output: w gear Compartment Input: Q_HP Q_AC Q_passengers Q_sun T_ambient phi_ambient mdot_air Output: T_innen phi_innen Parameter: ka-value volume mass N_Pass sun Q_cooling n compressr on/off T_inside Cooling Cycle Input: Output: on/off Q_heat-cool Q_heat-cool T mdot_h2o Parameter: volume HX-Geometry pump characteristic Q_heat-cool Heat Pump Input: n T_ambient T_indoor on/off Output: Q_heat-cool M Parameter: mdot_air displacement HX-geometry compressor characteristic rig geometry Auxiliary heater Input: on/off Parameter: efficiency Output: Q_heater mdot_diesel Controller Input: T_indoor Output: on/off compressor auxiliary heater Q_heating pump on/off Q_heat-cool heater on/off

12 Simulation model HX cabin cabin heater HX ambient TIL-Model for heat pump and cooling cycle HX engine cooler

13 Measurements 9 Heat up measurement versus simulation with air-air-heat pump 8 p discharge 7 pressure [bar] idle, T U = 4 C, heating only with air-air HP p suction Simulation measurement time [min]

14 Simulation results 5 Simulation: COP HP versus ambient temperature fresh air rate: n comp = 715 min % COP HP % 2% % n comp = 1755 min T cabin = 2 C fresh air rate = -5% ambient temperature [ C]

15 Simulation results 4 12 HX cabin heat pump cabin heater coolant 11 heat flow [W] T ambient = - 1 C; fresh air rate = 45%; BS-driving -1 cycle on off on off on off time [s] engine speed [rpm]

16 Simulation results diesel consumption [l/1km] aux. heaterr: fresh air = 45% aux. heater: fresh air = 2% heat pump: fresh air = 45% heat pump: fresh air = 2% aux. heater off: consumption without heating system: 27,7 l/1km consumption due to heating: ambient temperature [ C]

17 Simulation results Annual diesel consumption of city bus heating system 14 1% annual consumption [l/a] rel. economisation 52% auxiliary heater 625 l/a 3 l/a heat pump 8% 6% 4% 2% rel. economisation [%] % fresh air rate [%]

18 Summary - a reversible a/c & heat pump system with R-744 was installed in a city bus - in addition to measurements, a sophisticated simulation model including driving cycle and climate data (Modelica / TIL) has been used to evaluate the thermal behavior of the city bus - the R-744 air-air heat pump system is more efficient than the auxiliary fuel burner - the R-744 a/c system with air-air heat pump system has ecological and economical benefits

19 Thank you for your attention