Air-Conditioning and Mechanical Ventilation (ACMV) Systems

1 Air-Conditioning and Mechanical Ventilation (ACMV) Systems 1 Table of Contents 1. Air-Conditioning chilled water system 1 Vapour-compression refrigeration cycles 2 Function of main components 3 Types of Air-Conditioning Systems 4 Components and layouts of central chilled water system 12 Measurement and calculation of chilled water system performance 16 Measurement and instrumentation requirements 24 Chiller performance based on IPLV, NPLV and Singapore Standards 27 Optimisation of chilled water system 30 Air-cooled to water-cooled chiller 30 Chiller efficiency and life cycle costing 34 Chiller sizing and configuration 40 Peak and off-peak operation 46 Consolidation of chilled water Systems 48 Chiller sequencing strategies 51 Chilled and condenser water temperature reset 54 Condenser tube cleaning and water treatment 61 Thermal energy storage Systems 62 District cooling Systems 66 2.

2 Pumping Systems 68 Types of pumping Systems 68 system characteristic curves 70 Pump sizing 78 Pump characteristic curves 81 Pump operating point 83 Losses in piping Systems 88 Affinity laws 92 Constant and variable flow Systems 93 Optimisation strategies for pumping Systems 101 system serving multiple buildings 107 Reset of pump set-point 109 Pump performance and operation requirements based on Singapore Standards 110 2 3. Air handling Systems 113 Main components 113 Types of air handling Systems 113 All-air Systems 113 Air-water Systems 117 All-water Systems 118 Types of fans and their performances 119 Fan and system characteristic curves 120 Fan sizing 126 Fan operating point 129 Losses in ducting Systems 134 Affinity laws 140 Constant and variable air volume AHU Systems 141 Losses in filter and cooling coils 143 Air flow rate optimisation 146 Coil face velocity 148 Fan efficiency 149 Reset of fan set-point 150 Modified air handling Systems 152 Primary air handling unit (PAU) 152 Duel path AHU 153 Make-up air unit (MAU)

3 154 AHU with direct expansion Systems 155 AHU with solid desiccant Systems 156 AHU with energy recovery Systems 157 Displacement Ventilation system 160 Heat pump system 161 Fan performance and operation requirements based on Singapore Standards 163 4. Psychrometrics of Air-Conditioning processes 165 Properties of moist air 165 Determination of moist air properties using Psychrometric chart 169 Types of heat gain in spaces 171 Processes involve in AHU and spaces 171 Sensible heating 171 Sensible cooling 172 Mixing of two air streams 173 3 Cooling and dehumidification of air 177 Heat loads for AHU 178 Ventilation effects 179 Handling of sensible and latent cooling load of spaces 182 Air-Conditioning space requirements based on Singapore Standards 186 5. Cooling tower Systems 187 Configuration of cooling tower Systems 187 Heat transfer processes in cooling towers 189 Selection of cooling towers 194 Optimisation strategies of cooling towers 195 Installation of cooling towers 199 Maintenance of cooling towers 200 Cooling tower performance based on Singapore Standards 203 6.

4 Case study on retrofitting of chilled water system 205 4 Preface For a tropical climate like Singapore, Air-Conditioning and Mechanical Ventilation (ACMV) system is required to operate throughout the year to maintain thermal comfort inside the buildings. ACMV system consumes about 60% of the total energy consumption of a typical commercial building. Energy efficient design and optimisation of the ACMV system contribute significantly in reducing energy consumption and achieving cost savings. Designing and operating the central Air-Conditioning Systems in an energy efficient manner while maintaining the recommended Indoor Air Quality (IAQ) remains a challenge for design engineers and operators. More industrial facility and building owners and professionals are interested to understand the energy efficient design and optimisation opportunities for the ACMV Systems to trim their overall operating costs.

5 Electricity is the main form of energy used to operate the ACMV Systems . Non-renewable fossil fuels such as oil, gas and coal are generally used to generate the electricity. These fossil fuels during combustion emit carbon dioxide, which contributes to global warming. Since the ACMV Systems of commercial buildings and industrial plants consume a significant amount of electrical energy, government agencies in many countries including Singapore s National Environment Agency (NEA) and Building and Construction Authority (BCA) are also promoting proper energy management of the ACMV Systems as a means to trim carbon dioxide emissions. This reference manual (monograph) on ACMV Systems is developed mainly for the professionals who are interested to broaden their knowledge in energy efficient design, optimisation and operation of the ACMV Systems to reduce the energy and operating costs as well as the students who are specializing in energy Systems .

6 The monograph is written based on the author s experience in research and energy saving projects for over 10 years. Many actual case studies and examples with technical analysis presented in this document have been successfully implemented. The readers can confidently apply the concepts on their individual needs. The monograph contains five self-contained chapters on the different aspects and Systems relating to the energy management of the ACMV Systems . Chapter 1 provides an introduction to the Air-Conditioning chilled water system , vapour-compression refrigeration cycles, types of Air-Conditioning Systems , components and layouts of central chilled water Systems , measurement and calculation of chilled water system performance, optimisation strategies of chilled water system based on design and operational aspects and the thermal energy storage Systems . 5 Chapter 2 is devoted to different types of pumping Systems used in chilled water Systems , interaction of pump and system characteristic curves, pump sizing, applications of affinity laws, constant and variable flow Systems and optimisation strategies for pumping Systems .

7 Chapter 3 deals with different types of air handling Systems used in ACMV Systems , types of fans and their performances, interaction of fan and system characteristic curves, selection of fan, applications of affinity laws, constant and variable air volume AHU Systems , energy management strategies for air handling Systems and modified air handling Systems . Chapter 4 covers the Psychrometrics of Air-Conditioning processes, properties of moist air, determination of moist air properties, types of heat gain in spaces, processes involve in AHU and spaces which include mixing of different air streams, cooling and dehumidification of air as well as Ventilation effects. Chapter 5 discusses the different configurations of cooling tower Systems , heat transfer processes in cooling towers, selection and optimisation strategies for cooling towers, installation and maintenance of cooling towers. Finally, a case study on retrofitting of central chilled water system is presented in Chapter 6.

8 Some materials of this reference manual (monograph) have been reproduced from ASHRAE Handbooks and Singapore Standards SS591:2013, SS530: 2014, SS553, SS531: Part 1: 2006 and SS530:2014 with the permission of ASHRAE and SPRING Singapore, respectively. All rights reserved by ASHRAE and SPRING Singapore. I am extremely grateful to my past and present colleagues, especially Professor Wijeysundera and Dr. Lal Jayamaha, without whom I would not have been able to successfully complete so many research projects, energy audits and energy saving projects. Finally, I would like to express my sincere thanks to my wife Minni, son Shadman and daughter Suhi for their continued patience, understanding and support throughout the preparation of this monograph, which involved many long hours when my face was glued to my computer screen. Dr. Md Raisul Islam 6 1 Chapter-1: Air-Conditioning Chilled Water system 1.

9 Air-Conditioning Chilled Water system The purpose of an Air-Conditioning and Mechanical Ventilation system is to maintain comfort condition in the air-conditioned space irrespective of the outdoor ambient condition. Comfort condition usually refers to a specific range of temperature, relative humidity, cleanliness and distribution of air to meet the comfort requirements of the occupants in air-conditioned spaces. For a tropical country like Singapore, outdoor ambient temperature is generally higher than the comfort temperature of conditioned spaces. Therefore, Air-Conditioning chilled water Systems are required to operate throughout the year to maintain the comfort condition in the commercial buildings, hotels, hospitals, industrial buildings etc. Central Air-Conditioning plant is the single largest energy consumer that consumes about 60% of the total energy consumption of a typical commercial building.

10 Wise selection of the components of central Air-Conditioning plant and energy smart control and operation strategies may contribute to the significant energy and cost savings. In this section of the reference manual, the working principles of central Air-Conditioning chilled water Systems will be discussed. Methodologies for the evaluation of the energy performance and relative advantages and disadvantages of different types of chilled water Systems will be presented. Finally, the opportunities for the energy savings and relevant control strategies will be elaborated. Learning Outcomes Participants will be able to: i. Analyse the pressure -enthalpy diagram and identify the influences of operating variables on chiller performance. ii. Evaluate the performance of the chilled water Systems . iii. Select appropriate chilled water Systems based on cooling load behavior of the buildings and other considerations.