Introduction to HVAC
Contents of Chapter 1
Instructions
Objectives of Chapter 1
1.1 Introduction
1.2 Brief History of HVAC
1.3 Scope of Modern HVAC
1.4 Introduction to Air-Conditioning Processes
1.5 Objective: What is your system to achieve?
1.6 Environment For Human Comfort
The Next Step
Summary
Bibliography
Instructions
Read the material of Chapter 1. Re-read the parts of the chapter that are emphasized in the summary and memorize important definitions.
Objectives of Chapter 1 Chapter 1 introduces the history, uses and main processes of heating, venti- lating and air conditioning. There are no calculations to be done. The ideas
will be addressed in detail in later chapters. After studying the chapter, you
should be able to:
Define heating, ventilating, and air conditioning.
Describe the purposes of heating, ventilating, and air conditioning. Name and describe seven major air-conditioning processes.
Identify five main aspects of a space that influence an occupant’s comfort.
1.1 Introduction
Heating, Ventilating, and Air Conditioning (HVAC) is a huge field. HVAC
systems include a range from the simplest hand-stoked stove, used for comfortheating, to the extremely reliable total air-conditioning systems found in sub- marines and space shuttles. Cooling equipment varies from the small domestic unit to refrigeration machines that are 10,000 times the size, which are used in industrial processes.
Depending on the complexity of the requirements, the HVAC designer must
consider many more issues than simply keeping temperatures comfortable.
This chapter will introduce you to the fundamental concepts that are used by
designers to make decisions about system design, operation, and maintenance.
1.2 Brief History of HVAC
For millennia, people have used fire for heating. Initially, the air required to keep the fire going ensured adequate ventilation for the occupants. However, as central furnaces with piped steam or hot water became available for heating, the need for separate ventilation became apparent. By the late 1880s, rules of
thumb for ventilation design were developed and used in many countries.
In 1851 Dr. John Gorrie was granted U.S. patent 8080 for a refrigeration machine. By the 1880s, refrigeration became available for industrial purposes. Initially, the two main uses were freezing meat for transport and making ice.
However, in the early 1900s there was a new initiative to keep buildings cool
for comfort. Cooling the New York Stock Exchange, in 1902, was one of the
first comfort cooling systems. Comfort cooling was called “air conditioning.” Our title, “HVAC,” thus captures the development of our industry. The term “air conditioning” has gradually changed, from meaning just cooling to the
total control of:
• Temperature
• Moisture in the air (humidity)
• Supply of outside air for ventilation
• Filtration of airborne particles
• Air movement in the occupied space.
Throughout the rest of this text we will use the term “air conditioning” to include all of these issues and continue to use “HVAC” where only some of the elements of full air conditioning are being controlled. To study the historical record of HVAC is to take a fascinating trip through the tremendous technical and scientific record of society. There are the pioneers such as Robert Boyle, Sadi Carnot, John Dalton, James Watt, Benjamin Franklin,
John Gorrie, Lord Kelvin, Ferdinand Carré, Willis Carrier, and Thomas Midg- ley, along with many others, who have brought us to our current state. Air- conditioning technology has developed since 1900 through the joint accom-
plishments of science and engineering.
Advances in thermodynamics, fluid
mechanics, electricity, electronics, construction, materials, medicine, controls,
and social behavior are the building blocks to better engineered products of
air conditioning.
Historical accounts are not required as part of this course but, for the enjoy-
ment and perspective it provides, it is worth reading an article such as Mile-
stones in Air Conditioning, by Walter A. Grant
1 or the book about Willis Carrier,The Father of Air Conditioning.
2 The textbook Principles of Heating, Ventilating, and Air Conditioning,
3 starts with a concise and comprehensive history of the HVAC industry.
HVAC evolved based on:
• Technological discoveries, such as refrigeration, that were quickly adopted
for food storage.
• Economic pressures, such as the reduction in ventilation rates after the 1973
energy crisis.
• Computerization and networking, used for sophisticated control of large
complex systems serving numerous buildings.
• Medical discoveries, such as the effects of second hand smoke on people,
which influenced ventilation methods.
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