PPC907BE101 3BHE024577R0101 模拟量自动化输出卡 ABB
引进
本章致力于“基本”原则，即为未来奠定基础的某些原则。从
原著作者提出的分析典型问题的思维过程，读者将接触到我们这个时代的流行语：价值
工程接下来讨论规范和法规，以及将潜在设计解决方案限制在界限内的政治标准
公共卫生和福利，有时是特殊利益集团
由立法赞助。本章的后几节提供了一个简要说明
采暖、通风和空调基础物理回顾
（HVAC）在流体力学、热力学和热力学讨论中的设计，
热传递和湿度。众多的教室和设计
办公室经验提醒我们不断意识到
设计工作中暖通空调过程的物理学。
1.2问题解决
作为一步，每个暖通空调设计都涉及问题解决过程，通常以确定合适的为目标
特定应用的HVAC系统类型。思考是有益的
作为一系列逻辑步骤的问题解决过程，每个
这必须被执行以获得佳结果。虽然
定义流程有多种方法，如下顺序
已发现有用：
1.确定目标。期望的终结果是什么？用于暖通空调
目标通常是提供一个HVAC系统，该系统将控制：
来源：暖通空调系统设计手册
下载自数字工程图书馆@McGraw-Hill（www.digitalengineeringlibrary.com）
版权所有©2004麦格劳-希尔公司。版权所有。
任何使用均受网站上给出的使用条款的约束。
2.一章
所需参数范围内的环境，其寿命周期成本与需求兼容。请记住，成本将与
过程的需要。几乎可以更地控制环境
这总是意味着更大的成本。
2.定义问题。在本图中，问题在于选择
适当的暖通空调系统和设备，以满足目标。这个
问题必须明确和完整地定义，以便
可以显示解决问题的解决方案。
3.确定替代解决方案。头脑风暴在这里很有用。
解决任何问题总是有几种不同的方法。如果涉及改建或翻新，一种选择是什么也不做。
4.评估备选方案。必须对每个备选方案进行评估
为了有效性和成本。请注意，“无所事事”总是有代价的
等于不这样做而“失去”的机会、能量或效率
还有别的。
5.选择备选方案。许多因素影响了选择
过程有效性、成本、可用性、实用性等。
还有无形因素，如业主对特定类型设备的需求。
6.检查。选择的替代方案真的解决了问题吗？
7.实施所选备选方案。设计、构建和操作系统。
8.评估。问题解决了吗？目标实现了吗？
在下一个设计中可能会有哪些改进？
许多事业由于失败而失败，或终变得软弱
以满足这些问题解决增量中的一个或多个。有
能够识别关键问题或关键成功的艺术
或真正有益的选择。有时评估
将受到时间、预算或偏见的限制。假设或计算中偶尔会出现未检查的错误。防止失望的好方法是
良好的培训和责任团队的良好经验。
PPC907BE101 3BHE024577R0101 模拟量自动化输出卡 ABB
PPC907BE101 3BHE024577R0101 模拟量自动化输出卡 ABB
ntroduction
This chapter is devoted to ‘‘fundamental’’ fundamentals—certain principles which lay the foundation for what is to come. Starting with the
original author’s suggested thought process for analyzing typical problems, the reader is then exposed to a buzzword of our time: value
engineering. Next follows a discussion of codes and regulations, political 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 process, 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
Source: HVAC Systems Design Handbook
Downloaded 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.
2 Chapter One
the environment within required parameters, at a life-cycle cost compatible 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 remodeling 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 particular type of equipment.
6. Check. Does the selected alternative really solve the problem?
7. Implement the selected alternative. Design, construct, and operate 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. Occasionally there is an error in assumption or calculation that goes unchecked. The best defense against disappointment is the presence of
good training and good experience in the responsible group.
PPC907BE101 3BHE024577R0101 模拟量自动化输出卡 ABB
