Practical Fundamentals of Heating, Ventilation and Air Conditioning (HVAC) for Engineers and Technicians

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1 Presents Practical Fundamentals of Heating, Ventilation and Air Conditioning (HVAC) for Engineers and Technicians Revision 11.2 Website:

2 IDC Technologies Pty Ltd PO Box 1093, West Perth, Western Australia 6872 Offices in Australia, New Zealand, Singapore, United Kingdom, Ireland, Malaysia, Poland, United States of America, Canada, South Africa and India Copyright IDC Technologies All rights reserved. ISBN: All rights to this publication, associated software and workshop are reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher. All enquiries should be made to the publisher at the address above. Disclaimer Whilst all reasonable care has been taken to ensure that the descriptions, opinions, programs, listings, software and diagrams are accurate and workable, IDC Technologies do not accept any legal responsibility or liability to any person, organization or other entity for any direct loss, consequential loss or damage, however caused, that may be suffered as a result of the use of this publication or the associated workshop and software. In case of any uncertainty, we recommend that you contact IDC Technologies for clarification or assistance. Trademarks All logos and trademarks belong to, and are copyrighted to, their companies respectively. Acknowledgements IDC Technologies expresses its sincere thanks to all those engineers and technicians on our training workshops who freely made available their expertise in preparing this manual.

3 Contents 1 Introduction to HVAC General Principles of thermodynamics Temperature and its measurement Pressure and temperature relationship Laws of thermodynamics Fundamentals of heat transfer Fundamentals of fluid flow 11 2 Psychrometry Introduction to psychrometry The properties of air Understanding the psychrometric charts Psychrometric processes Air conditioning systems-summer and winter 40 3 Requirements of Comfort air conditioning General Air purification methods Thermodynamics of the human body Role of clothing Comfort and comfort chart Design considerations Requirements of temperature and humidity-high heat load industries Recommended inside design conditions Outside summer design conditions for some foreign cities Types of Ventilation Systems Effect of vertical temperature gradient & corrective measures Factors considered in air distribution systems indoor Indoor Air Quality Design of ventilation systems 84

4 4 Heating & Cooling Load Calculation Procedure General Definitions Design considerations Internal Sensible and Latent Heat Load components Design condition - indoor & outdoor conditions External Load components Miscellaneous heat sources Fresh air load Design of air-conditioning system By-pass factor (bf) consideration HVAC Systems Heating systems Warm air heating systems Sizing heating systems Hot water heating system Steam heating systems Electric heating systems District heating system Warm air curtains Air-conditioning systems: General Air Handling Units Functional variations in the design Fan coil unit Capacity calculation of an air handling unit Variable air volume (VAV) systems General System concept Different VAV systems Duct design, air flow and its distribution Air flow and pressure losses Dynamic losses in ducts Duct design Duct arrangement systems Air distribution system inside space Ventilation systems Effect of vertical temperature gradient and corrective measures 212

5 8 Insulation of Air-conditioning systems Introduction Desired properties of an ideal insulating material Factors affecting thermal conductivity Types of insulation materials Heat transfer through insulation Economical thickness of insulation Insulated systems Importance of relative humidity for the selection of insulation Air-conditioning equipment Air filters Humidifiers Dehumidifiers Fans and blowers Grills and registers Refrigeration General Methods of refrigeration Air refrigeration system Vapor compression refrigeration system Absorption refrigeration system Refrigerants Refrigerant nomenclature Important refrigerants Refrigeration equipment Controls and Instrumentation Objectives Introduction Definitions Elements of control Types of control system Methods of control Selection of a control system Typical control systems Control specifications Conclusion 336

6 12 Installation, Commissioning, Operation, Testing & Maintenance Objectives Installation Charging the refrigeration unit Adding oil to the compressor Commissioning Other service operations Operational activities Do s and don ts Maintenance Economics Fault finding and troubleshooting Objectives Introduction Faults Troubleshooting Green House effect and future refrigerants Objectives General The greenhouse effect History of CFCs Ozone depletion by CFCs and the greenhouse effect Global warming potential (GWP) and Ozone depleting potential(odp) Montreal protocol (1987) Kyoto protocol Future refrigerants to replace CFCs 383 Appendices 389 Appendix A: Symbols and units used in psychometric tables 389 Appendix B: Properties of refrigerants 397 Appendix C: Practical exercises 405 Appendix D: Equations 425 Appendix E: Testing, Adjusting and Balancing in HVAC systems 485 Appendix F: Conversion Tables 501 Appendix C1: Practical Exercises-Supplement 507 Appendix C2: Practical Exercises-Supplement-Psychrometric Chart Plotting 587

7 1 Introduction Objectives 1.1 General After reading this chapter the student should be able to: Refresh his knowledge on the engineering basics Understand the laws of thermodynamics Air conditioning for human comfort was considered a luxury a few decades ago, but now it has become a necessity in life. The air conditioning industry is rapidly developing throughout the world. More than 10 million window installations are being installed each year and residential central cooling installations are enjoying similar popularity. Apart from reasons for comfort alone, air conditioning is commonly used nowadays in various industries such as food, automobiles, hotels, textiles and many more. On Earth, not only pollution from smoke is on the rise but pollution from dust is also playing havoc with our lives. Air conditioning plays a vital role in keeping out smoke and dust which could harm our health. Similarly, air conditioning has an important role to play in the preservation of food. At present, there is hardly any sector of the economy that is not dependent on this industry. In fact in most areas of industry, HVAC systems are considered to be a basic necessity. It is thus important to become part of this industry and this course is targeted at providing you with the basic knowledge and technology to play a role in designing, installing and commissioning HVAC systems. The following gives an overview of the basic principles of thermodynamics, which play a key role in understanding HVAC systems.

8 2 Practical Fundamentals of Heating, Ventilation & Air-conditioning (HVAC) For Engineers and Technicians 1.2 Principles of Thermodynamics Force, Newtons In simple language, force is defined as a push or a pull. It is anything that has a tendency to set a body into motion, to bring a body to rest or change the direction of any motion Pressure, Pascals Pressure is the force exerted per unit area. It may be described as the measure of intensity of a force exerted on any given point on the contact surface. Whenever a force is evenly distributed over a given area the pressure at any point on the surface is the same. It can be calculated by dividing the total force exerted by the area (on which the force is exerted). Atmospheric pressure The Earth is surrounded by an envelope of air called the atmosphere, which extends upward from the surface of the earth. Air has mass and due to gravity exerts a force called weight. The force per unit area is called pressure. This pressure exerted on the Earth s surface is known as atmospheric pressure. Gauge pressure Most pressure measuring instruments measure the difference between the pressure of a fluid and the atmospheric pressure. This is referred to as gauge pressure. Absolute pressure Absolute pressure is the sum of gauge pressure and atmospheric pressure. Vacuum If the pressure is lower than the atmospheric pressure, its gauge pressure is negative and the term vacuum is applied to the magnitude of the gauge pressure when the absolute pressure is zero (i.e. there is no air present whatsoever). The relationships among absolute pressure, gauge pressure, atmospheric pressure and vacuum are shown graphically in the Figure 1.1.

9 Introduction Density Work Energy Figure 1.1 Relationship between absolute, gauge and vacuum pressures In the above figure P a is the atmospheric pressure P gauge is the gauge pressure P ab is the absolute pressure P vacuum is the vacuum pressure It is defined as the mass of a substance divided by its volume or the mass per unit volume. ρ = mass/volume Specific Volume is defined as the reciprocal of density or volume per unit mass. v = V/m Specific Weight (Ws) is defined as the weight of a substance divided by its volume or the weight per unit volume. Ws = m/v If a system undergoes a displacement under the action of a force, work is said to be done; the amount of work being equal to the product of force and the component of displacement parallel to the force. If a system as a whole exerts a force on its surrounding and a displacement takes place, the work that is done either by or on the system is said to be external work. A body is said to possess energy when it is capable of doing work. In more general terms, energy is the capacity of a body for producing an effect. Energy is classified as

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