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Air Conditioning System Modeling for Car Fuel Economy ... 1295967/FULLTEXT01.pdf · PDF file The automotive air conditioning system is the greatest auxiliary load of a vehicle, having

Jul 18, 2020

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  • Master of Science Thesis

    KTH School of Industrial Engineering and Management

    Energy Technology EGI- 2018-619

    Division of Applied Thermodynamics and Refrigeration

    SE-100 44 STOCKHOLM

    Air Conditioning System Modeling for

    Car Fuel Economy Simulation

    Arturo Alejandro Torres Arevalo

    Changhao Han

  • Master of Science Thesis EGI 2018:619

    Air Conditioning System Modeling for Car

    Fuel Economy Simulation

    Arturo Alejandro Torres Arevalo

    Changhao Han

    Approved

    Examiner

    Samer Sawalha

    Supervisor

    Samer Sawalha

    Commissioner

    Contact person

  • iii

    Abstract

    The automotive air conditioning system is the greatest auxiliary load of a vehicle, having a considerable impact on its fuel consumption and CO2 emissions. For this reason, forecasting the influence that this sys- tem has on the fuel economy of a car is desired. The present work is dedicated to model the air conditioning system of a plug-in hybrid ve- hicle in order to predict its energy consumption.

    GT-SUITE was chosen as the simulation tool, where the air condi- tioner, which is a vapor-compression refrigeration system, was mod- eled by specifying its components: compressor, evaporator, thermal expansion valve and condenser. Moreover, additional sub-systems which influence the energy consumption were also considered, these are the vehicle’s cabin and the battery cooling loop.

    The simulated model shows good agreement with test data for impor- tant parameters such as the compressor power consumption and the air temperature after the evaporator. The percent difference between the test data and the simulation for the auxiliary power consumption (energy consumed by the A/C compressor and the charging load of the low voltage battery) is 6.25%.

  • iv

    Sammanfattning

    På ett fordon utgör luftkonditioneringssystem den främsta extraordi- nära energibelastningen, vilket har stor påverkan på bränsleförbruk- ning och koldioxidutsläpp. Av detta skäl är det önskvärt att förutse det inflytande som detta system har på fordonets bränsleekonomi. Detta arbete är har för avsikt att simulera luftkonditioneringssystemet för ett plug-in hybridfordon för att förutsäga energiförbrukningen.

    GT-SUITE valdes som simuleringsverktyg, där klimatanläggningen, som är ett ångkomprimerat kylsystem, modellerades genom att speci- ficera komponenterna: kompressor, förångare, värmeutvidgningsven- til och kondensor. Dessutom beaktades ytterligare delsystem som på- verkar energiåtgången, nämligen fordonets hytt och batterikylnings- loop.

    Den simulerade modellen visar en god korrelation med testdata för be- tydelsefulla parametrar såsom kompressorns energiförbrukning och lufttemperaturen efter förångarsteget. Den procentuella skillnaden mel- lan testdata och simuleringen för den extra energiförbrukningen (ener- gi som förbrukas av A/C-kompressorn och laddningen av lågspän- ningsbatteriet) är 6,25%.

  • v

    Acknowledgements

    We would like to express our gratitude to our KTH professor and su- pervisor Samer Sawalha, who gave us the technical background that made possible for us to obtain this thesis.

    Furthermore, we express our gratitude to our CEVT supervisors: Lei Xu and Anna Rimark, who provided us with the necessary guidance and tools that helped us accomplish this work. Additionally, we would like to thank our manager at CEVT: Sofia Ore, whose optimism and sympathy helped us communicate with our colleagues and create a positive work environment.

    Finally, Arturo would like to thank the Mexican National Council for Science and Technology (CONACYT) together with the Mexican En- ergy Ministry (SENER) for providing the financial resources needed to obtain his master’s degree through the scholarship: "CONACYT- SECRETARIA DE ENERGIA- SUSTENTABILIDAD ENERGETICA ref.: 601279 / 439254”

  • vi

    Abbreviations and Acronyms

    AAC Automotive Air Conditioning

    A/C Air Conditioning

    EPA Environmental Protection Agency (United States)

    EV Electric Vehicle

    GHG Greenhouse Gas

    HEV Hybrid Electric Vehicle

    HVAC Heating, Ventilation, and Air Conditioning

    IEA International Energy Agency

    PHEV Plug-in Hybrid Electric Vehicle

    PID Proportional-Integral-Derivative

    UDDS Urban Dynamometer Driving Schedule

  • Contents

    1 Introduction 1 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.4 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

    2 Literature Review 4 2.1 Automotive HVAC models . . . . . . . . . . . . . . . . . 4 2.2 A/C Compressor Control . . . . . . . . . . . . . . . . . . 6 2.3 Driving Cycles . . . . . . . . . . . . . . . . . . . . . . . . . 7

    2.3.1 SC03 Driving Cycle . . . . . . . . . . . . . . . . . . 7

    3 Current A/C system 9 3.1 Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2 Condenser, Battery Radiator, and Evaporator . . . . . . . 11 3.3 Chiller and Battery Cooling Circuit . . . . . . . . . . . . . 11 3.4 A/C Blower and Condenser Fan . . . . . . . . . . . . . . 12 3.5 High and Low Voltage Battery . . . . . . . . . . . . . . . . 12 3.6 Thermal Expansion Valve . . . . . . . . . . . . . . . . . . 12

    4 System Modeling 14 4.1 Solver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.2 Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.3 Heat Exchangers . . . . . . . . . . . . . . . . . . . . . . . 17 4.4 Cabin and Air Loop . . . . . . . . . . . . . . . . . . . . . . 19 4.5 HV Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

    4.5.1 Battery Cooling Circuit . . . . . . . . . . . . . . . 21 4.5.2 Battery Current Coupling . . . . . . . . . . . . . . 22

    4.6 Fans and pumps . . . . . . . . . . . . . . . . . . . . . . . . 23 4.7 Thermal Expansion Valves . . . . . . . . . . . . . . . . . . 24

    vii

  • viii CONTENTS

    4.8 Pipes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

    5 Validation 26 5.1 Battery Model Validation . . . . . . . . . . . . . . . . . . . 26 5.2 A/C System Validation . . . . . . . . . . . . . . . . . . . . 29

    5.2.1 Air Temperature after the Evaporator . . . . . . . 29 5.2.2 Compressor Speed . . . . . . . . . . . . . . . . . . 32 5.2.3 Compressor Power Consumption . . . . . . . . . 32 5.2.4 Cabin Temperature . . . . . . . . . . . . . . . . . . 35

    6 Results 36 6.1 SC03 Test Conditions . . . . . . . . . . . . . . . . . . . . . 36 6.2 Simulation Results . . . . . . . . . . . . . . . . . . . . . . 37

    7 Conclusions 39

    Bibliography 41

  • List of Figures

    2.1 SC03 Driving Cycle [28] . . . . . . . . . . . . . . . . . . . 8

    3.1 A/C system with battery cooling loop . . . . . . . . . . . 10 3.2 Simplified compressor control strategy . . . . . . . . . . . 11

    4.1 Compressor map (example) [30] . . . . . . . . . . . . . . . 16 4.2 Modeled compressor in GT-SUITE . . . . . . . . . . . . . 17 4.3 Discretization of both “master” and “slave” objects for

    both crossflow (right) and counterflow (left) heat exchang- ers [31] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

    4.4 Sources of heat from the ambient, and heat transferred from the mass to the cabin . . . . . . . . . . . . . . . . . . 19

    4.5 Cabin Air Loop . . . . . . . . . . . . . . . . . . . . . . . . 20 4.6 Thermal and electrical parts of the HV battery (exam-

    ple) [32] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.7 Battery Cooling Circuit . . . . . . . . . . . . . . . . . . . . 22 4.8 High Voltage Battery in GT-SUITE . . . . . . . . . . . . . 23 4.9 Low Voltage Battery in GT-SUITE . . . . . . . . . . . . . . 23 4.10 ‘TXVDetail4Quadrant’ template[34] . . . . . . . . . . . . 25

    5.1 Actual and Simulated Battery Temperature . . . . . . . . 27 5.2 Different Natural Convection Heat Transfer Coefficients

    for Battery Cooling . . . . . . . . . . . . . . . . . . . . . . 28 5.3 Battery Temperature Validation . . . . . . . . . . . . . . . 29 5.4 P-h Diagram at 1162.3s (Before Modification) . . . . . . . 30 5.5 P-h Diagram at 1159.5s (After Modification) . . . . . . . . 31 5.6 Air Temperature After the Evaporator Validation . . . . . 31 5.7 Compressor Speed Validation . . . . . . . . . . . . . . . . 32 5.8 Compressor Power Validation . . . . . . . . . . . . . . . . 33 5.9 Refrigerant Mass Flow Rate through the evaporator . . . 34

    ix

  • x LIST OF FIGURES

    5.10 Cabin Temperature Validation . . . . . . . . . . . . . . . . 35

    6.1 Laboratory Ambient Air Temperature for the Cold-Start and Warm-Start Cases . . . . . . . . . . . . . . . . . . . . 37

    6.2 Auxiliary Power Consumption Comparison . . . . . . . . 38

  • Chapter 1

    Introduction

    1.1 Background

    Between 1971 and 2015 the world’s energy consumption more than doubled. In this time the transport sector share in the total final energy consumption increased from 23% to 29% [1]. This sector, which ac- counts for 23% of the current global GHG emissions related to energy, will need to deliver considerable emission reductions if the countries wish to meet their GHG goal [2]. To provide a solution for this prob- lem, a roadmap was outlined by the European Commission to reduce

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