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Studies on the Control Method of Optimal Heat Rejection Pressure in CO2 Heat Pump : 이산화탄소 열펌프의 최적 고압 제어 방법에 대한 연구
DC Field | Value | Language |
---|---|---|
dc.contributor.advisor | 김민수 | - |
dc.contributor.author | 신창수 | - |
dc.date.accessioned | 2017-07-14T03:47:10Z | - |
dc.date.available | 2017-07-14T03:47:10Z | - |
dc.date.issued | 2014-02 | - |
dc.identifier.other | 000000017467 | - |
dc.identifier.uri | https://hdl.handle.net/10371/123983 | - |
dc.description | 학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부(멀티스케일 기계설계전공), 2014. 2. 김민수. | - |
dc.description.abstract | For the last two decades, numerous environmental problems have affected all throughout the world. Among these problems, global warming and ozone depletion is severely under attack resulted from the use of conventional synthetic refrigerants. Thus, many researchers have endeavored to utilize alternative refrigerants in order to overcome this problem. Above all, carbon dioxide, called CO2, is well appreciated and eco-friendly as an alternative refrigerant because it has low global warming potential (GWP) and ozone depletion potential (ODP), compared to the other synthetic refrigerant such as hydrochlorofluorocarbon (HCFC) or hydrofluorocarbon (HFC).
Usually, transcritical cycle is built in a CO2 refrigeration cycle where CO2 is employed as a refrigerant owing to its low critical temperature. In addition, high-side pressure of the CO2 refrigeration system is much higher than that of the conventional refrigeration system. In this way, coefficient of performance (COP) which is a main index of the system performance is highly sensitive to high pressure, called heat rejection pressure, at the gas cooler. In conclusion, optimization of the heat rejection pressure is a must to study performance of transcritical CO2 cycle. In this study, a control method of optimal heat rejection pressure in CO2 heat pump is investigated. First of all, one control parameter is analyzed by various conditions of the system and proposed. In sequence, basic experiment was performed in the transcritical CO2 cycle with internal heat exchanger, changing the compressor operating frequency and expansion valve opening. Moreover, change of refrigerant charge amount had an effect on the system performance. As a result, maximum COP was appeared at the smaller opening when the compressor speed existed in the lower state. An optimal refrigerant charge amount was occurred at a certain condition. Results were confirmed with suggested control method by conducting control experiment. The point where controlled parameter and current COP of a steady-state system are encountered called an operating point. Error was calculated with the difference between the value of parameter and maximum system COP. It was presented that if various conditions with setting control parameter were capable to use for real-time control in a transient–state system on the basis of result analysis in this study. | - |
dc.description.tableofcontents | Contents
Abstract i Contents iv List of Tables vii List of Figures viii Nomenclatures x CHAPTER 1. INTRODUCTION 1 1.1 Background of the Study 1 1.2 Literature Review 6 1.2.1 Characteristics of CO2 heat pump system and advancement 6 1.2.2 Various approaches to optimization in CO2 cycles 13 1.3 Objectives and Scope of the Study 17 CHAPTER 2. CONTROL METHOD STUDY ON THE OPTIMAL HEAT REJECTION PRESSURE 19 2.1 Introduction 19 2.2 Concept 20 2.3 Various Conditions for Setting Control Parameter 22 2.3.1 Gas cooler outlet conditions 22 2.3.2 Compressor-side conditions 24 2.3.3 Determination of control parameter 27 2.4 On-line Control Method 29 2.4.1 Outline of the control method 29 2.4.2 Application to PI controller 30 2.4.3 Capacity control and efficiency control 33 CHAPTER 3. EXPERIMENTAL STUDY ON THE CO2 HEAT PUMP USING CONTROL METHOD 37 3.1 Introduction 37 3.2 Experimental Setup 38 3.3 Measurement and Data Reduction 46 3.3.1 Measurement 46 3.3.2 Data reduction 48 3.4 Basic Experiment for Characteristics of CO2 Heat Pump 52 3.4.1 Experimental procedure 52 3.4.2 Data on the gas cooler outlet and the compressor suction 54 3.4.3 A trend of COP and capacity 60 3.4.4 Control parameter verification 64 3.5 Control Experiment with On-line Control Method 67 3.5.1 Experimental background 67 3.5.2 Experimental procedure 67 3.5.3 Results of the on-line control method 70 3.6 Limitation 73 CHAPTER 4. CONCLUSION 75 References 76 Abstract (Korean) 83 | - |
dc.format | application/pdf | - |
dc.format.extent | 2201630 bytes | - |
dc.format.medium | application/pdf | - |
dc.language.iso | en | - |
dc.publisher | 서울대학교 대학원 | - |
dc.subject | Control method | - |
dc.subject | Optimal heat rejection pressure | - |
dc.subject | Control parameter | - |
dc.subject | CO2 heat pump | - |
dc.subject.ddc | 621 | - |
dc.title | Studies on the Control Method of Optimal Heat Rejection Pressure in CO2 Heat Pump | - |
dc.title.alternative | 이산화탄소 열펌프의 최적 고압 제어 방법에 대한 연구 | - |
dc.type | Thesis | - |
dc.contributor.AlternativeAuthor | Chang Soo Shin | - |
dc.description.degree | Master | - |
dc.citation.pages | xi, 84 | - |
dc.contributor.affiliation | 공과대학 기계항공공학부(멀티스케일 기계설계전공) | - |
dc.date.awarded | 2014-02 | - |
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