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Design optimization of heat exchangers of an engine waste heat recovery system for a gasoline vehicle based on combined-dimensional thermal flow analysis approach : 복합차원 열유동 해석 기법을 통한 가솔린 자동차용 엔진 폐열 회수 시스템 열교환기의 설계 최적화
DC Field | Value | Language |
---|---|---|
dc.contributor.advisor | 김찬중 | - |
dc.contributor.author | 배석정 | - |
dc.date.accessioned | 2017-07-13T06:17:30Z | - |
dc.date.available | 2017-07-13T06:17:30Z | - |
dc.date.issued | 2015-02 | - |
dc.identifier.other | 000000024975 | - |
dc.identifier.uri | https://hdl.handle.net/10371/118424 | - |
dc.description | 학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2015. 2. 김찬중. | - |
dc.description.abstract | Strict regulations on emission and fuel consumption are expanding worldwide in response to the global warming and the depletion of natural resources. The improvement of fuel efficiency by development of power-train technology has reached its limit.
In this study, a waste heat recovery system based on Rankine cycle is constructed to improve the fuel efficiency of gasoline vehicles. A commercial CFD analysis tool is capable of predicting detailed flow distribution for complex geometries, but it cannot adequately simulate the phase change processes yet. On the other hand, the performance prediction code is one-dimensional, but it can take phase change into account, and enables a quick verification of the effect of change in design factors. In this study, an optimized design process has been established by harmonizing the advantages of these two design techniques. The design of the waste heat recovery system have been performed through combined-dimensional analytical processes. First of all, the system layout has been decided by the one-dimensional analysis. The cycle performance prediction program has been developed to select working fluids through the system performance prediction, design the cycle performance, and decide the design specification of core components. As a result, the system layout containing dual-loop cycles has been designed. The waste heat recovery system consists of an HT (high temperature) loop, in which water, as the HT working fluid, recovers waste heat from the exhaust gas, and an LT (low temperature) loop, in which a refrigerant, as the LT working fluid, recovers heat dissipation from the HT loop, and waste heat from the engine coolant of relatively low temperature. A new design of HT boiler, which recovers waste heat from exhaust gas, has been conducted. The working fluid in the HT boiler experiences a phase change from liquid state to saturated state. At a liquid state, the specific volume of the working fluid is so small that the cross-sectional area must be small, otherwise it would not recover sufficiently the waste heat. On the other hand, at a saturated state, the specific volume of the working fluid grows with quality, i.e., the cross-sectional area of the heat exchanger need to be considerably large compared to that of liquid state. Focusing on this point, three structural concepts have been established, designed via 1D and 3D analytical design process, embodied as prototypes, and assessed by experiments. A novel design process model for an LT condenser has been built, so that the pressure drop is reduced, while the heat transfer performance is maintained close to a target value. The refrigerant has low enough evaporation temperature to recover the waste heat from engine coolant of about 100 ℃, but has small saturation enthalpy. Thus, excessive mass flow rate of the LT working fluid, e.g. over 150 g/s, causes a significant pressure drop to maintain the heat dissipation performance of more than 20 kW. An investigation for multi-pass structural design has been conducted by inspecting the number of passes, and the arrangement of the numbers of tubes, in order to enhance the flow uniformity and reduce the pressure drop of working fluid. The cycle design technology and the combined-dimensional optimization design process for the core heat exchangers are expected to play a role of bridgehead to secure technological competitiveness in the future automotive waste heat recovery field. | - |
dc.description.tableofcontents | Abstract i
List of Tables vii List of Figures viii Nomenclature xii Chapter 1 Introduction 1.1 Background and Motivation 1 1.2 Previous Researches 5 1.2.1 Automotive Rankine Cycle 5 1.2.2 Core Components of Rankine Cycle 8 1.3 Thesis Objectives 10 1.4 Thesis Outline 13 Chapter 2 Design of Cycle and System Layout 2.1 Basic of Rankine Cycle 15 2.2 Selection of the Working Fluid 19 2.2.1 HT Working Fluid 22 2.2.2 LT Working Fluid 25 2.3 Configuration of the System Layout 28 2.3.1 Heat Recovery Conditions 28 2.3.2 Limit Conditions for Cycle Design 30 2.3.3 Design of System Layout 32 2.3.4 Dual-Loop System Layout 42 Chapter 3 Design Process of a High Temperature Boiler 3.1 Role of HT Heat Recovery Exchangers 49 3.2 Design Conditions for an HT Boiler 52 3.3 Concept Design for an HT Boiler 54 3.3.1 Design of Fin and Helical Coil type 54 3.3.2 Design of Circular Shell & Spiral Tube type 57 3.3.3 Design of Rectangular Shell & Spiral Tube type 59 3.4 Analytical Design of HT Boiler 61 3.4.1 Fin & Helical Coil type Design Program 65 3.4.2 Cylindrical Shell & Spiral Tube type Design Program 69 3.4.3 Rectangular Shell & Spiral Tube type Design Process 76 3.5 Drafts of the HT boilers 80 3.6 Performance Evaluation 83 3.6.1 Experimental Apparatus 83 3.6.2 Experimental Conditions and Methods 86 3.6.3 Experimental Results 88 3.7 Conclusion 104 Chapter 4 Design Process of Low Temperature Condenser 4.1 Role of an LT Condenser 106 4.2 Design Conditions for an LT Condenser 109 4.3 Design Model 111 4.4 Design and Analysis Program for the LT condenser 113 4.5 Design and analysis 120 4.5.1 Decision of the Number of Passes 120 4.5.2 Arrangement of the Numbers of Tubes 121 4.5.3 Assessment of the Flow uniformity 124 4.5.4 Decision for the Optimum Design Draft 129 4.6 Experimental Results 133 4.7 Conclusion 139 Chapter 5 Conclusion and Future Works 142 Bibliography 148 국문초록 153 | - |
dc.format | application/pdf | - |
dc.format.extent | 4388656 bytes | - |
dc.format.medium | application/pdf | - |
dc.language.iso | en | - |
dc.publisher | 서울대학교 대학원 | - |
dc.subject | Waste Heat Recovery System | - |
dc.subject | Rankine Cycle | - |
dc.subject | Boiler | - |
dc.subject | Condenser | - |
dc.subject | Thermal Flow Analysis | - |
dc.subject | Combined-dimensional Analysis | - |
dc.subject.ddc | 621 | - |
dc.title | Design optimization of heat exchangers of an engine waste heat recovery system for a gasoline vehicle based on combined-dimensional thermal flow analysis approach | - |
dc.title.alternative | 복합차원 열유동 해석 기법을 통한 가솔린 자동차용 엔진 폐열 회수 시스템 열교환기의 설계 최적화 | - |
dc.type | Thesis | - |
dc.contributor.AlternativeAuthor | Sukjung Bae | - |
dc.description.degree | Doctor | - |
dc.citation.pages | xiii, 155 | - |
dc.contributor.affiliation | 공과대학 기계항공공학부 | - |
dc.date.awarded | 2015-02 | - |
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