Air Conditioning

Air Conditioning

An air conditioner (often abbreviated to AC in the United States, and air-con in Australia and in Great Britain) is an appliance or mechanism designed to extract heat from an area using a refrigeration cycle. To many people, air conditioners are symbolic of the Western world. In construction, a complete system of heating, ventilation and air conditioning is referred to as HVAC.

An earlier form of air conditioning was invented in Persia (Iran) thousands of years ago in the form of wind shafts on the roof, which caught the wind and passed it through water and blew the cooled air into the building

The 19th century British inventor, Michael Faraday discovered that compressing and liquefying a certain gas could chill air when the liquified gas was allowed to evaporate. His idea remained largely theoretical.

One of the first uses of air conditioning for personal comfort was in 1902 when the New York Stock Exchange’s new building was equipped with a central cooling as well as heating system. Alfred Wolff, an engineer from Hoboken, New Jersey who is considered the forerunner in the quest to cool a working environment, helped design the new system, transferring this budding technology from textile mills to commercial buildings.

Later in 1902, the first modern, electrical air conditioning was invented by Willis Haviland Carrier (1876–1950). His invention differed from Wolff’s in that it controlled not only temperature, but also humidity for improved manufacturing process control for a printing plant in Brooklyn, New York. This specifically helped to provide low heat and humidity for consistent paper dimensions and ink alignment. Later, Carrier’s technology was applied to increase productivity in the workplace, and the Carrier Engineering Company, now called Carrier (a division of United Technologies Corporation), was formed in 1915 to meet the new demand. Later still, air conditioning use was expanded to improve comfort in homes and automobiles. Residential sales didn’t take off until the 1950’s.

In 1906, Stuart Cramer first used the term “air conditioning” as he explored ways to add moisture to the air in his southern textile mill. He combined moisture with ventilation to actually “condition” and change the air in the factories, controlling the humidity so necessary in textile plants.

The first air conditioners and refrigerators employed toxic gases like ammonia and methyl chloride, which resulted in fatal accidents when they leaked. Thomas Midgley, Jr. created the first chlorofluorocarbon gas, dubbed Freon in 1928. The refrigerant proved much safer for humans but not for the atmosphere’s ozone layer. “Freon” is a trade name of Dupont for any CFC, HCFC, or HFC refrigerant, the name of each including a number indicating molecular composition (R-11, R-12, R-22, R-134). The blend most used in direct-expansion comfort cooling is an HCFC known as R-22, and is slated to be phased out for use in new equipment by 2010 and completely discontinued by 2020. R-11 and R-12 are no longer manufactured in the US, the only source for purchase being the cleaned and purified gas recovered from other air conditioner systems.

Types of air conditioning

Refrigeration cycle

Refrigeration Cycle

Refrigeration Cycle

In the refrigeration cycle, a heat pump pumps heat from a lower temperature heat source into a higher temperature heat sink. Heat would naturally flow in the opposite direction. This is the most common type of air conditioning.

A refrigerator works in much the same way, as it pumps the heat out of the interior into the room in which it stands.

This cycle takes advantage of the universal gas law PV = nRT, where P is pressure, V is volume, R is the universal gas constant, T is temperature, and n is the number of moles of gas (1 mole = 6.022 * 10^23 molecules. All quantities are in SI units).

The most common refrigeration cycle uses an electric motor to drive a compressor. In an automobile the compressor is driven by a pulley on the engine’s crankshaft, with both using electric motors for air circulation. Since evaporation absorbs heat, and condensation releases it, air conditioners are designed to use a compressor to cause pressure changes between two compartments, and actively pump a refrigerant around. A refrigerant is pumped into the cooled compartment (the evaporator coil), where the low pressure and load temperature cause the refrigerant to evaporate into a vapour, taking heat with it. In the other compartment (the condenser), the refrigerant vapour is compressed and forced through another heat exchange coil, condensing into a liquid, rejecting the heat previously absorbed from the cooled space.

Humidity


Refrigeration air conditioning equipment usually reduces the humidity of the air processed by the system. The relatively cold (below the dewpoint) evaporator coil condenses water vapor from the processed air, (much like an ice cold drink will condense water on the outside of a glass), sending the water to a drain and removing water vapor from the cooled space and lowering the relative humidity. Since humans perspire to provide natural cooling by the evaporation of perspiration from the skin, drier air (up to a point) improves the comfort provided. The comfort air conditioner is designed to create a 40% to 60% relative humidity in the occupied space.

Refrigerants


“Freon” is a trade name for a family of flourocarbon refrigerants manufactured by DuPont and other companies. These refrigerants were commonly used due to their superior stability and safety properties. Unfortunately, evidence has accumulated that these chlorine bearing refrigerants reach the upper atmosphere when they escape. The chemistry is poorly understood but general consensus seems to be that CFCs break up in the stratosphere due to UV-radiation, releasing their chlorine atoms. These chlorine atoms act as catalysts in the breakdown of ozone, which does severe damage to the ozone layer that shields the Earth’s surface from the strong UV radiation. The chlorine will remain active as a catalyst until and unless it binds with another particle forming a stable molecule. CFC refrigerants in common but receding usage include R-11 and R-12. Newer and more environmentally-safe refrigerants include HCFCs (R-22, used in most homes today) and HFCs (R-134a, used in most cars) have replaced most CFC use.

Evaporation coolers


The aforementioned Persian cooling systems were evaporation coolers. In very dry climates, such affectionately called “swamp coolers” are popular for improving comfort during hot weather. The evaporative cooler is a device that draws outside air through a wet pad. The sensible heat of the incoming air, as measured by a dry bulb thermometer, is reduced. The total heat (sensible heat plus latent heat) of the entering air is unchanged. Some of the sensible heat of the entering air is converted to latent heat by the evaporation of water in the wet cooler pads. If the entering air is dry enough, the results can be quite comfortable. These coolers cost less and are mechanically simple to understand and maintain.

An early type of cooler, using ice for a further effect, was patented by John Gorrie of Apalachicola, FL in 1842, who used the device to cool the patients of his malaria hospital.

A three-stage absorptive cooler exists that first dehumidifies the air with a spray of salt brine. The brine osmotically absorbs water vapor from the air. The second stage sprays water in the air, evaporatively cooling (via absorptive refrigeration) the air. Finally, to control the humidity, the air passes through another brine spray. The brine is reconcentrated by distillation. The system is used in some hospitals because, with filtering, a sufficiently hot regenerative distillation controls airborne organisms.

Absorptive chillers

Absorptive chillers

Absorptive chillers

Some buildings use gas turbines to generate electricity. The exhausts of these are hot enough to drive an absorptive chiller that produces cold water. The cold water is then run through radiators in air ducts for hydronic cooling. The dual use of the energy, both to generate electricity and cooling, makes this technology attractive when regional utility and fuel prices are right. Producing heat, power, and cooling in one system is known as trigeneration.

Power

Air conditioner equipment power in the U.S. is often described in terms of “tons of refrigeration”. A “ton of refrigeration” is defined as the cooling power of one ton US (2000 pounds or 907 kilograms) of ice melting in a 24-hour period. This is equal to 12,000 BTU per hour, or 3510 watts (http://physics.nist.gov/Pubs/SP811/appenB9.html). Residential “central air” systems are usually from 1 to 5 tons (3 to 20 kW) in capacity.

The use of electric/compressive air conditioning puts a major demand on the nation’s electrical power grid in warm weather, when most units are operating under heavy load. In the aftermath of the 2003 North America blackout locals were asked to keep their air conditioning off. During peak demand, additional power plants must often be brought online, usually natural gas fired plants because of their rapid startup. A 1995 study of various utility studies of residential air conditioning concluded that the average air conditioner wasted 40% of the input energy. This energy is lost, ironically, in the form of heat, which must be pumped out. There is a huge opportunity to reduce the need for new power plants and to conserve energy.

In an automobile the A/C system will use around 5 hp (4 kW) of the engine’s power.

Insulation

Insulation reduces the required power of the air conditioning system. Thick walls, reflective roofing material, curtains and trees next to building also cut down on system and energy requirements.

Dry Cleaning

Dry Cleaning

Dry Cleaning is any cleaning process for clothing and textiles using a solvent other than water.

History

Early dry cleaners used petroleum based solvents such as gasoline and kerosene. Concerns over flammability lead William Joseph Stoddard, a dry cleaner from Atlanta, to develop Stoddard solvent as a slightly less flammable alternative to gasoline based solvents. The use of highly flammable petroleum solvents lead to many fires and explosions, which resulted in heavy regulation of dry cleaners.

After World War I dry cleaners began using various chlorinated solvents, because they were much less flammable than petroleum solvents and had much greater cleaning power. By the mid-1930s the dry cleaning industry settled on perchloroethylene (perc) as the ideal solvent. It is stable, nonflammable, and has excellent cleaning power while being gentle to garments.

Solvents used

Modern

  • Perchloroethylene — Perfect solvent, unmatched cleaning performance
  • High flash point hydrocarbons DF-2000 (140*F flash point) — Slightly less flammable and explosive than Stoddard Solvent, not as effective as perchloroethylene.
  • Modified hydrocarbons blends (Pure Dry)
  • Glycol ethers (dipropylene glycol tertiary-butyl ether) (Rynex) — not as effective as perchloroethylene.
  • Cyclic Silicone decamethylcyclopentasiloxane, GreenEarth — not as effective as perchloroethylene. Very Expensive and requires royalties be paid to GE.
  • Supercritical CO2 — Inconsistent performance, machinery is very expensive.

Historical

  • Stoddard Solvent — Very flammable and explosive, 100*F flash point.
  • carbon tetrachloride — Toxic and corrosive
  • trichloroethane — Overly aggressive and harsh
  • Valclene 113 Freon-113 — Ozone destroying CFC, otherwise very nice and non toxic.

Process

A dry cleaning machine is somewhat similar to combination of a domestic washing machine, and clothes dryer.

Garments are placed into a washing/extraction chamber (referred to as the “basket”). This is the core of the dry cleaning machine. The washing chamber contains a horizontal, perforated drum that rotates within an outer shell. The shell holds the solvent while the rotating drum holds the garment load. Depending on the size of the machine the basket capacity will be between 20 and 80 lb of garments.

During the wash cycle the chamber is filled approximately 1/3rd full of solvent and begins to rotate to agitate the clothing. The solvent temperature is controlled at 85*F, as a higher temperature may extract dye from the garments causing color loss. During the wash cycle, the chamber is constantly fed a supply of fresh solvent from the working solvent tank while spent solvent is removed and sent to a filter unit. The ideal flow rate is one gallon of solvent per pound of garments per minute.

A typical wash cycle lasts for 8-15 minutes depending on the type of garments and amount of soiling. During the first three minutes

solvent-soluble soils dissolve into the perchloroethylene and loose insoluble soil from fabrics comes off. It takes approximately ten to twelve minutes after the loose soil has come off to remove all of the ground-in insoluble soil from the garments. Machines using hydrocarbon solvents require a much longer wash cycle of at least 25 minutes because of the much slower rate of solvation of solvent soluble soils (e.g oily stains).

At the end of wash cycle, the machine starts a rinse cycle and the garment load is rinsed with fresh distilled solvent from the pure solvent tank. This pure solvent rinse prevents discoloration of garments caused by soil particles being adsorbed back onto the garment surface from the “dirty” working solvent.

After the rinse cycle the machine begins the extraction process. This process recovers dry cleaning solvent for reuse. Modern dry cleaning machines can recover approximately %99.99 of the solvent used in the cleaning process.

The extraction begins by draining the solvent out of the washing chamber cycle and accelerating the basket to speeds of 350 to 450 rpm, causing much of the solvent to spin free of the fabric. When no more solvent can be spun out, the machine starts its drying cycle.

Solvent processing

Working solvent from the washing chamber passes through several filtration steps before it it returned to washing chamber. The first step is a button trap which prevents small objects (lint, fasteners, buttons, coins etc) from entering the solvent pump.

Next the solvent passes through a filter unit which removes lint and insoluble suspended soils from the solvent. Several different types are used, most filters use an ultra fine mesh to support a thin layer of filter powder (made from diatomaceous earth and activated clays). Some machines use powderless filters which are capable a removing soil particles greater than 30 micrometers from the solvent.

As the machine is used, a thin layer of filter cake (called muck) accumulates on the surface of the lint filter. The muck is removed regularly (once per day) and then further processed to recover any solvent trapped in the muck. Many machines use “spin disc filters” in which the muck is removed from the filter surface by centrifugal action while the filter is back-washed with solvent.

After passing through the lint filter, the solvent passes through an absorptive cartridge filter, this filter is made from activated clays and charcoal and removes fine insoluble soil and non-volatile residues along with dyes from solvent. Finally the solvent passes through a polishing filter which removes any traces of soil not removed by the previous filters. The clean working solvent is then returned to the working solvent tank.

To enhance cleaning power, small amounts of detergent (0.5%-1.5%) are added to the working solvent and are essential to its functionality. These detergents help dissolve hydrophilic soils and keep soil from redepositing on garments. Depending on the machine’s design, either an anionic or cationic detergent is used.

Dry Cleaning wastes

Cooked muck

Cooked Powder Residue – The waste material generated by cooking down or distilling muck. Cooked powder residue is a hazardous waste and will contain solvent, powdered filter material (diatomite), carbon, non-volatile residues, lint, dyes, grease, soils and water.

Sludge


The waste sludge or solid residue from the still. Still bottoms contain solvent, water, soils, carbon and other non-volatile residues. Still bottoms from chlorinated solvent dry cleaning operations are hazardous wastes.

Environment

Perc is toxic and some believe that long-term exposure can cause liver and kidney damage, though no study has conclusively proven that. There are other solvents including:

Your Local Carpet Expert

Australia Carpet Cleaning


Your rugs and carpets attract dirt, allergens, pet dander, pollen, and household dust that vacuums are usually unable to remove. Your couches collects dust and dirt that will ruin your furniture in time if it is not properly cleaned. Air ducts will get clogged with household dust and allergens. Cleaning is needed on a regular basis to ensure this will not happen.

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Our professional home cleaning service can take care of these things so you don’t have to. We take care for your furnishings because we have a deep understanding of which cleaning solutions to use to get the best results. We are familiar with all the different types of fabrics that are in a home and their best cleaning combinations as well as how to best maintain that new look and smell.

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Wood Flooring

Wood Flooring

stainless steel appliances
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furniture, pillows, blankets, etc.
Cleaning Services is a locally based cleaning service provider. To be more accessible to our customers we are available anytime of the day. And since we’re right here in town we can often schedule same day services, too.