Heating Performance of a Vapor Injection Heat Pump for Electric Vehicles under Various Startup Conditions
- 주제(키워드) Heat pump , electric vehicle , vapor injection
- 발행기관 고려대학교 대학원
- 지도교수 김용찬
- 발행년도 2018
- 학위수여년월 2018. 2
- 학위구분 박사
- 학과 대학원 기계공학과
- 세부전공 열및유체공학전공
- 원문페이지 123 p
- 실제URI http://www.dcollection.net/handler/korea/000000080308
- 본문언어 영어
- 제출원본 000045932184
초록/요약
A heat pump, which enable the cooling and heating of vehicular cabins, consumes a significant portion of the total energy consumption in electric vehicles (EVs). The efficiency of heat pump is typically degraded owing to cold-weather conditions, so the refrigerant-injection technique has been proposed for improving the system performance and compressor reliability. Even though the heat pump with vapor injection has already been demonstrated to improve the performance of residential and commercial heat pumps at low ambient temperatures, few researches concerning the applications of these vapor injection techniques to the heat pump of EVs are available in the open literature. The objective of this study is to optimize the heating performance of heat pump with vapor injection used in EVs. First, a simulation model for an R134a heat pump with vapor injection is developed and validated by performing thermodynamic analyses with geometrical information. The effects of the injection-port design are investigated using the developed numerical model. Single-injection and dual-injection ports are considered to optimize the coefficient of performance (COP) and isentropic efficiency by controlling the injection mass flow rate. The optimal angles of the single- and dual-injection ports are determined to be 440° and 535°/355° (for pocket A/B), respectively, while the corresponding COPs are improved by 7.5% and 9.8%, respectively, compared to the heat pump without vapor injection at an outdoor temperature of -10 °C. Second, the heating performance of the heat pump with vapor injection for EVs was optimized by examining the internal heat exchanger (IHX) type injection with scroll compressor with respect to the injection-port angle on the scroll compressor and the IHX size. The optimal injection-port angle and the length of IHX were determined to be 620° and 300 mm, respectively. At the injection-port angle of 620°, the COP and isentropic efficiency were 3.5–31.8% and 0.0–19.7% higher than those of other angles of the injection port, respectively. The COP and isentropic efficiency of a 300 mm IHX were 0.0–18.6% and 0.2–11.2% higher than those of other IHX lengths, respectively. The other objective of this study is to investigate the comparison of heating performance characteristic between R1234yf and R134a in the heat pumps for EVs with vapor injection. To achieve the objectives of this study, an R1234yf heat pump in EVs was tested with various operating conditions. The comparison of heating performance characteristic and exergy loss were investigated. The R1234yf heat pump with and without vapor injection showed 5.2–17.2% and 4.2–10.9% of the COP improvement, respectively. The relative isentropic efficiency of the R1234yf heat pump with and without vapor injection were 1.3–17.8% and 3.8–8.0%, respectively. When the cycle configuration was same, the total ELPH (exergy loss per heating capacity) of the R1234yf heat pumps was lower than that of the R134a heat pumps.
more목차
Chapter 1. Introduction 1
1.1 Background 1
1.2 Literature review 5
1.2.1 Numerical Studies of a heat pump used in vehicles 5
1.2.2 A heat pump with a vapor injection technique 6
1.2.3 Drop-in performance of an R1234yf for a heat pump 8
1.3 Objectives and outline of this study 10
Chapter 2. Experimental Setup 12
2.1 Introduction 12
2.2 A heat pump with FT type vapor injection 12
2.3 A heat pump with IHX type vapor injection 15
2.4 Measuring equipment 18
2.5 Test chamber 20
Chapter 3. Numerical Study of the Effects of Injection-port Design on the Heating Performance of an R134a Heat Pump with Vapor Injection used in Electric Vehicles 22
3.1 Introduction 22
3.2 Simulation modeling 24
3.2.1 Modeling of compressor 24
3.2.2 Modeling of heat exchangers 27
3.2.3 Simulation model of heat pump with vapor injection 29
3.3 Validation of simulation model 33
3.4 Results and discussion 35
3.4.1 Geometrical analysis 35
3.4.2 Effects of injection-port angle 38
3.4.3 Dual-injection ports 46
3.5 Summary 54
Chapter 4. Optimal Design and Drop-in Performance Comparison of Vapor Injection Heat Pumps used in Electric Vehicles 55
4.1 Introduction 55
4.2 Test conditions and procedure 57
4.3 Results and discussion 63
4.3.1 Optimization of the injection port 63
4.3.2 Optimization of the IHX 73
4.3.3 Comparison of the heating performance characteristics 82
4.3.4 Comparison of the exergy loss 94
4.4 Summary 97
Chapter 5. Concluding Remarks 99
5.1 Conclusions 99
5.2 Future works 101
