Variable Refrigerant Flow Systems: Advances and Applications of VRF

Description

This book compiles the latest research, development, and application of VRF systems with contributions from various experts who pioneered and contributed to the development of the VRF system. This book presents the fundamental issues related to the real application and behaviour of the VRF system based on the long-term monitoring of the installed system. With our experience of pandemic which COVID-19 is an airborne, the spread of the virus is very fast. With this, the heating, ventilating and air-conditioning (HVAC) system is a major player in the maintenance and control of indoor environment to minimize the spread of the virus. As the variable refrigerant flow (VRF) system is a versatile HVAC system in which it can operate at different conditions, the application of the VRF system is very important to control the indoor environmental conditions. Thus, the publication of this book is important with the present situation and the future possible situation which the control of indoor spaces is very important. With this, this book will serve as a reference for building designer, contractors, building regulators and students. Preface Contents About the Editors 1 Trends in Variable Refrigerant Flow Systems 1.1 Introduction 1.2 Variable Refrigerant Flow (VRF) System 1.3 Applications 1.4 Conclusions References 2 Evaluating the Ignition Hazard of Alternative Refrigerants for Variable Refrigerant Flow Systems 2.1 Introduction 2.2 Fundamentals of Combustion Characteristics of Alternative Refrigerants 2.2.1 Evaluating the Physical Hazard Because of Fire and Explosion 2.2.2 Classification of the Alternative Refrigerant from Flammability 2.3 Physical Hazard of A2L Refrigerants Assuming Conceivable Accident Scenarios 2.3.1 Outline 2.3.2 Is A2L Refrigerant Ignited by a Commercial Lighter? 2.3.3 Is A2L Refrigerant Jet Leaked with High Pressure Ignited? 2.3.4 Full-Scale Experiment to Evaluate the Ignitability and Combustion Strength of A2L Refrigerant Leaked from the VRF System 2.4 Summary References 3 Flow Boiling Heat Transfer of Low GWP Refrigerant R1234yf with the Entrancement of Lubricating Oil in Small Diameter Tubes 3.1 Introduction 3.2 Experimental Apparatus 3.3 Results and Discussions 3.3.1 Solubility of R1234yf and Lubricating Oil (PAG (VG46)) 3.3.2 Flow Pattern Observation 3.3.3 Heat Transfer Coefficient 3.3.4 Pressure Drop 3.4 Conclusions References 4 Analysis of Air Side Cooling and Dehumidification Performance in Evaporator in Direct Expansion (DX) Variable Refrigerant Flow (VRF) Air-Conditioning (A/C) System 4.1 Introduction 4.1.1 Direct Expansion (DX) Air Conditioning (A/C) System 4.1.2 Indoor RH Level and Its Effect on Human Thermal Comfort 4.1.3 Suitable Range of Indoor RH for Thermal Comfort 4.1.4 Variable-Speed Compressor and Supply Fan in a DX A/C Unit 4.1.5 Modeling the Heat and Mass Transfer Taking Place on the Airside of DX Air Cooling Coils 4.1.6 Proposition 4.2 Experimental Station 4.2.1 Detailed Descriptions of the Experimental System and Its Major Components 4.3 A Calculation Method for Steady State Equipment SHR of DX Air Conditioning Units 4.3.1 Assumptions 4.3.2 Development of the New Calculation Method 4.4 Dehumidification Effects on the Airside of the SPR of a DX Air Cooling Coil 4.4.1 A Calculation Procedure for Evaluating Dehumidification Effect on the Airside of a SPR 4.5 Results and Discussion 4.5.1 Uncertainty Analysis 4.6 A Modified LMED Method for Evaluating the Total Heat Transfer Rate of a Wet Cooling Coil Under Both Unit and Non-Unit Lewis Factors 4.6.1 Development of the m-LMED Method 4.6.2 Validation of the m-LMED Method 4.6.3 The Procedure for Applying the m-LMED Method 4.6.4 Discussion 4.7 Conclusions References 5 Application of Machine Learning and Artificial Intelligence in Design, Optimization, and Control of VRF Systems 5.1 Introduction 5.2 The Working Principle of a VRF System 5.3 Different Approaches for AL and ML to Use in VRF Systems 5.4 Literature Review 5.5 Fault Detection and Diagnosis of the VRF System Using Data Driven Methods References 6 Energy Efficient Variable Refrigerant Flow Systems for Modern Buildings 6.1 Introduction 6.2 Energy Scenario in Buildings 6.2.1 Need for Energy Efficient and Sustainable Buildings 6.2.2 Energy Efficient HVAC Systems in Buildings 6.3 Variable Refrigerant Flow (VRF) Systems 6.3.1 Attributes of VRF Systems 6.3.2 Amalgamation of Control Systems in VRF 6.4 Assessment of VRF Systems for Buildings 6.4.1 Advanced Intelligent Control Methodologies 6.4.2 Cooling Application 6.4.3 Heating Application 6.4.4 Key Property Indicators for Fulfilling VRF Integration in Buildings 6.5 Feasibility of VRF Systems for Modern Buildings 6.5.1 Energetic Potential 6.5.2 Economic Prospects 6.5.3 Merits and Challenges 6.5.4 Scope for Future Research 6.6 Conclusions References 7 Behavior of a Variable Refrigerant Flow System in a Controlled Simulated Dynamic Environment 7.1 Introduction 7.2 Evaluation Procedure 7.2.1 Conditions 7.2.2 VRF System 7.2.3 Evaluation Conditions 7.2.4 Performance Evaluation 7.3 Results and Discussion 7.3.1 Behavior of the VRF System 7.3.2 Performance of the VRF System 7.4 Conclusions References 8 An Air Enthalpy Method for Measuring the Thermal Capacity of an Installed Variable Refrigerant Flow System 8.1 Introduction 8.2 Methodology 8.2.1 Test Facility 8.2.2 Test Specimen 8.2.3 Test Method 8.2.4 Test Evaluation 8.3 Results and Discussion 8.3.1 Air Fan Rotation and Flow Rate Correlation 8.3.2 Indoor Units Air Fan 8.3.3 Air Flow and Air Enthalpy 8.3.4 Thermal Capacity 8.4 Conclusions References 9 Field Test and Evaluation of VRF System 9.1 Background of Field Test 9.2 Methodology of On-Field Performance Measurement 9.2.1 Water Temperature Difference Method 9.2.2 Air Enthalpy Difference Method 9.2.3 Refrigerant Enthalpy Difference Method 9.2.4 Comparison of Field Measurement Methods 9.3 Field Performance Test and Evaluation of VRF (of On-Field Performance Measurement Methods) 9.3.1 Measurement and Tracking to Actual Performance 9.3.2 Field Performance Test Standard 9.4 Summary and Prospect References 10 Variable Refrigerant Flow (VRF) System Field Test and Data Analysis Methodologies 10.1 Introduction 10.2 VRF System Field Tests in the Literature 10.3 VRF System Field Test Method 10.4 A Case Study in a Campus Office Building 10.5 Comparisons Between Quasi-Steady State (QSS) and Time Average Metrics 10.6 Conclusions References