engineering

Heating, ventilation, and air conditioning

Heating, ventilation, and air conditioning is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Heating, ventilation, and air conditioning rather than just read about it. In short: Heating, ventilation, and air conditioning (HVAC ) systems regulate temperature, humidity, and indoor air quality in vehicles and buildings. They are designed to provide thermal comfort and to control airborne contaminants through heating, cooling, ventilation, filtration, and humidity control.

Key takeaways

Heating, ventilation, and air conditioning belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Heating, ventilation, and air conditioning to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Heating, ventilation, and air conditioning from memory before moving on to harder problems.

Reference excerpt

Heating, ventilation, and air conditioning (HVAC ) systems regulate temperature, humidity, and indoor air quality in vehicles and buildings. They are designed to provide thermal comfort and to control airborne contaminants through heating, cooling, ventilation, filtration, and humidity control. HVAC design considerations include energy efficiency, indoor air quality, maintenance, and environmental impact, particularly in green building projects. In building design, mechanical, electrical, and plumbing engineers may integrate HVAC systems with other building systems (i.e. air-source heat pump water heaters) and use energy modeling to evaluate performance and operating costs.

Summary The three major functions of heating, ventilation, and air conditioning are intertwined. HVAC systems can provide ventilation and maintain pressure relationships between spaces. The means of air delivery and removal from spaces is known as room air distribution.

Individual systems

In modern buildings, the design, installation, and control systems of these functions are integrated into one or more HVAC systems. For very small buildings, contractors normally estimate the capacity and type of system needed and then design the system, selecting the appropriate refrigerant and various components needed. For larger buildings, building service designers, mechanical engineers, or building services engineers analyze, design, and specify the HVAC systems. Specialty mechanical contractors and suppliers then fabricate, install, and commission the systems. Building permits and code-compliance inspections of the installations are normally required for all sizes of buildings.

District networks Although HVAC is executed in individual buildings or other enclosed spaces (like NORAD's underground headquarters), the equipment involved is in some cases an extension of a larger district heating (DH) or district cooling (DC) network, or a combined DHC (District-Heating-Cooling) network. In such cases, the operating and maintenance aspects are simplified, and metering becomes necessary to bill for the energy that is consumed and, in some cases, energy that is returned to the larger system. For example, at a given time, one building may be utilizing chilled water for air conditioning, and the warm water it returns may be used in another building for heating or for the overall heating-portion of the DHC network (likely with energy added to boost the temperature). Basing HVAC on a larger network helps provide an economy of scale that is often not possible for individual buildings, for utilizing renewable energy sources such as solar heat, winter's cold, the cooling potential in some places of lakes or seawater for free cooling, and the enabling function of seasonal thermal energy storage.

History

HVAC is based on inventions and discoveries made by Nikolay Lvov, Michael Faraday, Rolla C. Carpenter, Willis Carrier, Edwin Ruud, Reuben Trane, James Joule, William Rankine, Sadi Carnot, Alice Parker and many others. Multiple inventions within this time frame preceded the beginnings of the first comfort air conditioning system, which was designed in 1902 by Alfred Wolff (Cooper, 2003) for the New York Stock Exchange, while Willis Carrier equipped the Sacketts-Wilhems Printing Company with the process AC unit the same year. Coyne College was the first school to offer HVAC training in 1899. The first residential AC was installed by 1914, and by the 1950s there was "widespread adoption of residential AC".

Heating

Heating is the process of transferring thermal energy to an enclosed space in order to raise or maintain its temperature for the comfort of its occupants. In central heating systems, a central source such as a boiler, furnace, or heat pump supplies thermal energy at a central location, and air, water, or steam transfers that energy to the spaces to be heated, where it is delivered by convection, radiation, or both. Small space heaters may also be used to heat individual rooms.

Generation

Heaters exist for various types of fuel, including solid fuels, liquids, and gases. Another type of heat source is electricity, normally heating ribbons composed of high resistance wire (see Nichrome). This principle is also used for baseboard heaters and portable heaters. Electrical heaters are often used as backup or supplemental heat for heat pump systems. The heat pump gained popularity in the 1950s in Japan and the United States. Heat pumps can extract heat from various sources, such as environmental air, exhaust air from a building, or from the ground. Heat pumps transfer heat from outside the structure to the air inside. Initially, heat pump HVAC systems were only used in moderate climates, but with improvements in low temperature operation and reduced loads due to more efficient homes, they are increasing in popularity in cooler climates. They can also operate in reverse to cool an interior.

Distribution

Water/steam In the case of heated water or steam, piping is used to transport the heat to the rooms. Most modern hot water boiler heating systems have a circulator, which is a pump, to move hot water through the distribution system (as opposed to older gravity-fed systems). The heat can be transferred to the surrounding air using radiators, hot water coils (hydro-air), or other heat exchangers. The radiators may be mounted on walls or installed within the floor to produce floor heat. The use of water as the heat transfer medium is known as hydronics. The heated water can also supply an auxiliary heat exchanger to supply hot water for bathing and washing.

Air

Warm air systems distribute the heated air through ductwork systems of supply and return air through metal or fiberglass ducts. Many systems use the same ducts to distribute air cooled by an evaporator coil for air conditioning. The air supply is normally filtered through air filters to remove dust and pollen particles.

Dangers The use of furnaces, space heaters, and boilers as a method of indoor heating can result in incomplete combustion and the emission of carbon monoxide, nitrogen oxides, formaldehyde, volatile organic compounds, and other combustion byproducts. Incomplete combustion occurs when there is insufficient oxygen; the inputs are fuels containing various contaminants and the outputs are harmful byproducts, such as carbon monoxide, a tasteless and odorless gas with serious adverse health effects.

Ventilation

… excerpt ends here. Continue reading the full article.

Illustrations

Heating, ventilation, and air conditioning: Ventilation duct with outlet diffuser vent. These are installed throughout a building to move air in or out of rooms. In the middle is a damper to open and close the vent to allow more or less air to enter the space. — Ventilation duct with outlet diffuser vent. These are installed throughout a building to move air in or out of rooms. In the middle is a damper to open and close the vent to allow more or less air to enter the space.

Worked examples

Example 1 — a first encounter with Heating, ventilation, and air conditioning

Start with the simplest possible case. Write down what Heating, ventilation, and air conditioning claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Heating, ventilation, and air conditioning before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Heating, ventilation, and air conditioning ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Heating, ventilation, and air conditioning

In research: Heating, ventilation, and air conditioning appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Heating, ventilation, and air conditioning in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Heating, ventilation, and air conditioning is common in secondary-school and first-year university syllabi. It links to neighbouring topics Building biology, Building engineering, Construction, so understanding it makes those chapters shorter.
In everyday life: Look for Heating, ventilation, and air conditioning outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Heating, ventilation, and air conditioning in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Heating, ventilation, and air conditioning means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Heating, ventilation, and air conditioning out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Heating, ventilation, and air conditioning in simple terms?

Why does Heating, ventilation, and air conditioning matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Heating, ventilation, and air conditioning?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Heating, ventilation, and air conditioning.