What makes air cold

The postwar building spree was underpinned by the idea that all of these new buildings would consume incredible amounts of power, and that this would not present any serious problems in the future. In , the journal Energy and Buildings published an article by the British conservative academic Gwyn Prins , arguing that the American addiction to air conditioning was a symbol of its profound decadence. With some exceptions — Japan, Australia and Singapore were early adopters.

Now, however, air conditioning is finally sweeping across the rest of the world. If the march of air conditioning across the US tracked its postwar building and consumption boom, its more recent expansion has followed the course of globalisation. As the rest of the world adopts more Americanised ways of building and living, air conditioning follows. In the s, many countries across Asia opened up to foreign investment and embarked on an unprecedented urban building spree.

Over the past three decades, about million people in India have moved to cities; in China, the number is more than million. From New Delhi to Shanghai, heavily air-conditioned office buildings, hotels and malls began to spring up.

These buildings were not only indistinguishable from those in New York or London, but were often constructed by the same builders and architects. They thought that meant progress. As the rate and scale of building intensified, traditional architectural methods for mitigating hot temperatures were jettisoned.

Leena Thomas, an Indian professor of architecture at the University of Technology in Sydney, told me that in Delhi in the early s older forms of building design — which had dealt with heat through window screens, or facades and brise-soleils — were slowly displaced by American or European styles. Just like the US in the 20th century, but on an even greater scale, homes and offices were increasingly being built in such a way that made air conditioning indispensable.

So they simply built and relied on technology to fix it later. Lall says that even with affordable housing it is possible to reduce the need for air conditioning by designing carefully. But he argues that, in general, developers are not interested. They want to storey blocks close to one another. This reliance on air conditioning is a symptom of what the Chinese art critic Hou Hanru has called the epoch of post-planning. Today, planning as we traditionally think of it — centralised, methodical, preceding development — is vanishingly rare.

Markets dictate and allocate development at incredible speed, and for the actual inhabitants, the conditions they require to live are sourced later, in a piecemeal fashion. Over coffee recently in London, the influential Malaysian architect Ken Yeang lamented what he viewed as the loss of an entire generation of architects and builders to a dependency on fossil fuels to control the environment.

To its proponents, air conditioning is often presented as a simple choice that consumers make to improve their lives as they climb the economic ladder.

This refrain is as familiar in Rajasthan now as it was in the US 70 years ago. In her book Vietnam, Mary McCarthy reflected on this subtle restriction of choice in American life. There is plenty of room for improvement. The invention of air conditioning predates both the first aeroplane and the first public radio broadcast, and the underlying technology has not changed much since One scheme to encourage engineers to build a more efficient air conditioner was launched last year by the Rocky Mountain Institute RMI , a US-based energy policy thinktank, and endorsed by the UN environment programme and government of India.

The aim is to design an air conditioner that is five times more efficient than the current standard model, but which costs no more than twice as much money to produce. They have received more than a hundred entries, from lone inventors to prominent universities, and even research teams from multibillion-dollar appliance giants. But, as with other technological responses to climate change, it is far from certain that the arrival of a more efficient air conditioner will significantly reduce global emissions.

The more they jiggle and move about, the hotter the temperature! Knowing this renowned physicist's words, one might wonder why a pocket of air in motion — i. When you sit in front of a fan on a hot day, the blades propel air molecules toward you, speeding them up and smacking them against your skin. Why don't these energetic molecules burn? In the upper reaches of the atmosphere, the decreasing density means that even if the temperature were constant, it would FEEL like the temperature was going down.

This lowering of temperature with altitude is called the "lapse rate" and a standard lapse rate is about 3deg Fahrenheit per feet. This can change from degrees F depending on variables like pressure, humidity, etc. If you want to learn more about it, search for information on the tropopause.

Answered by: Frank DiBonaventuro, B. They are constantly banging into each other and into things around them. When you blow up a balloon, the air molecules bang into the insides of the balloon and that is what makes the balloon expand. This motion is a form of kinetic energy. Things that moves and have mass have kinetic energy. Air molecules move and have mass, so they have kinetic energy. Air temperature is essentially a measure of the average kinetic energy of the air molecules.

The faster the molecules move, the higher their kinetic energy and therefore the higher their temperature. Agreed Pretty good stuff. Agreed with the others on the water analogy. What is the effect on the efficiency of the system if the actual condensing units are shaded lower temp vs in the hot sun themselves with high cabinet temperature? Great, very clear article Great, very clear article Allison. I was trying to explain this to a customer the other day to no avail…I will now email them the link to this article.

Thank you! I had to read through the gravity analogy twice before I began to understand it…still not sure I get it. Great article. What people Great article. What people want is comfort so the dehumidification and the cooling are separte functions. Save energy by using programmable thermostats.

Be ready for the upcoming Demand Response opportunities that will ask that the compressor be turned off just for a short period to avoid the peak demand and the fossil fuel to meet it. Allison, great idea to cover Allison, great idea to cover basic refrigeration cycle. How about a primer on pschrometrics? The compressor serves the purpose of greatly raising the pressure of the gas, so the condensation point is also raised.

For example, at 95F, my system has a high side pressure of lbs. Steve, installing AC on north Steve, installing AC on north or northeast side of house or otherwise providing shade will increase both capacity and efficiency. Keeping sun off the condenser is a great strategy in new construction when the cost may be next to nothing often depends on location of air handler, as well as aesthetic and noise considerations. If you plant vegetation or build a shading structure, just be sure to respect the mfr recommended clearances.

For heat pumps, ideal placement would put the unit in direct sun in the AM and shaded after noon. Outstanding, you could not Outstanding, you could not have made it clearer, with the exception of the gravitational analog How do you find the time……. Kevin L. David Butler did a great job explaining why the temperatures are different in a comment below yours. Steve : I was focusing only on the thermodynamics of air conditioning in this article.

Naturally, a better building envelope and ducts inside make the home more efficient and the equipment more durable, as will right-sizing. Improving the conditions of the condensing unit also help. Mark T. I wanted to avoid as much of the technical terminology as I could to keep this post simpler, though.

Stefan : Thanks! I hope the other person finds it as understandable. David K. Thanks for mentioning it. David B. Carl C. Mike : Mike : Thanks for the info about Gorrie. He used the ammonia cycle to cool air about 30 years before Gorrie was making ice in Florida. Donald B. The refrigerant coming out of the expansion valve does evaporate to a small degree.