HVAC Systems Design Handbook part 1

This chapter is devoted to ‘‘fundamental’’ fundamentals—certain principleswhich lay the foundation for what is to come. Starting with theoriginal author’s suggested thought process for analyzing typical problems,the reader is then exposed to a buzzword of our time: valueengineering. Next follows a discussion of codes and regulations, politicalcriteria which constrain potential design solutions to the boundsof public health and welfare, and sometimes to special interest groupsponsored legislation....
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HVAC Systems Design Handbook part 1 Source: HVAC Systems Design Handbook Chapter HVAC Engineering Fundamentals: 1 Part 1 1.1 Introduction This chapter is devoted to ‘‘fundamental’’ fundamentals—certain prin- ciples which lay the foundation for what is to come. Starting with the original author’s suggested thought process for analyzing typical prob- lems, the reader is then exposed to a buzzword of our time: value engineering. Next follows a discussion of codes and regulations, polit- ical criteria which constrain potential design solutions to the bounds of public health and welfare, and sometimes to special interest group sponsored legislation. The final sections of the chapter offer a brief review of the basic physics of heating, ventilating, and air conditioning (HVAC) design in discussions of fluid mechanics, thermodynamics, heat transfer, and psychrometrics. Numerous classroom and design office experiences remind us of the value of continuous awareness of the physics of HVAC processes in the conduct of design work. 1.2 Problem Solving Every HVAC design involves, as a first step, a problem-solving pro- cess, usually with the objective of determining the most appropriate type of HVAC system for a specific application. It is helpful to think of the problem-solving process as a series of logical steps, each of which must be performed in order to obtain the best results. Although there are various ways of defining the process, the following sequence has been found useful: 1. Define the objective. What is the end result desired? For HVAC the objective usually is to provide an HVAC system which will control 1Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. HVAC Engineering Fundamentals: Part 1 2 Chapter One the environment within required parameters, at a life-cycle cost com- patible with the need. Keep in mind that the cost will relate to the needs of the process. More precise control of the environment almost always means greater cost. 2. Define the problem. The problem, in this illustration, is to select the proper HVAC systems and equipment to meet the objectives. The problem must be clearly and completely defined so that the proposed solutions can be shown to solve the problem. 3. Define alternative solutions. Brainstorming is useful here. There are always several different ways to solve any problem. If re- modeling or renovation is involved, one alternative is to do nothing. 4. Evaluate the alternatives. Each alternative must be evaluated for effectiveness and cost. Note that ‘‘doing nothing’’ always has a cost equal to the opportunity, or energy, or efficiency ‘‘lost’’ by not doing something else. 5. Select an alternative. Many factors enter into the selection process—effectiveness, cost, availability, practicality, and others. There are intangible factors, too, such as an owner’s desire for a par- ticular type of equipment. 6. Check. Does the selected alternative really solve the problem? 7. Implement the selected alternative. Design, construct, and op- erate the system. 8. Evaluate. Have the problems been solved? The objectives met? What improvements might be made in the next design? Many undertakings fail, or are weak in the end result, due to failing to satisfy one or more of these problem-solving increments. There is an art in being able to identify the key issue, or the critical success factors, or the truly beneficial alternative. Sometimes the evaluation will be clouded by constraint of time, budget, or prejudice. Occasion- ally there is an error in assumption or calculation that goes un- checked. The best defense against disappointment is the presence of good training and good experience in the responsible group. 1.3 Value Engineering Value analysis or value engineering (VE) describes a now highly so- phisticated analytical process which had its origins in the materiel shortages of World War II. In an effort to maintain and increase pro- duction of war-related products, engineers at General Electric devel- oped an organized method of identifying the principal function or ser- vice to be rendered by a device or system. Then they looked at the current solution to see whether it truly met the objective i ...