Refrigerators
The Physics Hypertextbook™
© 1998-2008 by Glenn Elert -- A Work in Progress
All Rights Reserved -- Fair Use Encouraged
Discussion
introduction
A refrigerator is any kind of enclosure (like a box, cabinet, or room) whose interior temperature is kept substantially lower than the surrounding environment.
The term "refrigerator" was coined by a Maryland engineer, Thomas Moore, in 1800. Moore's device would now be called an "ice box" -- a cedar tub, insulated with rabbit fur, filled with ice, surrounding a sheet metal container. Moore designed it as as a means for transporting butter from rural Maryland to Washington, DC. Its operating principle was the latent heat of fusion associated with melting ice.
The term "air conditioning" was coined by Stuart Cramer in 1905 to describe his system for regulating the temperature and humidity inside a textile factory in the South (the humidity regulation was seen as more important than the temperature regulation). Willis Carrier also designed climate control systems for industry.
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.
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.
An early pioneer who did much to promote "controlled air" was Willis Carrier, a mechanical engineer who worked at the Buffalo Forge Company in Buffalo, New York. Subsequent subsidiary companies carrying his name helped conquer the temperature-humidity relationship, marrying theory with practicality. Starting in 1902, he designed a spray-type temperature and humidity controlled system. His induction system for multi-room office buildings, hotels, apartments and hospitals was just another of his air-related inventions. Many industry professionals and historians consider him the "father of air conditioning."
There are several basic refrigeration techniques:
- ice box (or dry ice box)
- cold air systems
- vapor-compression: the current standard method of refrigeration used in home refrigerators, home air conditioners and heat pumps (Kelvin's idea, refrigerate the environment in the winter, store "cold" in the ground for use in the summer)
- vapor-absorption: the Electrolux refrigerator with no moving parts
- thermoelectric
cold air refrigeration
Physician Dr. John Gorrie, Apalachicola, Florida, 1849. Rapidly expanding gases are cooled. Intended to cool hospital wards. Hot air was considered "bad", was thought to be the origin of tropical diseases, thus the name "malaria". Died before commercial models could be made. Design improved by William Siemans of Germany. Dr. Gorrie may have also invented the ice cube tray in its current form.
By widening the vessel … from the bottom upward the removal of the block of ice is … rendered more easy ….
To further facilitate the removal of the ice from the vessels [they are] made a little smaller at the bottom than at the top ….
schematic diagram
indicator diagram
vapor compression refrigeration
In 1834 an American inventor named Jacob Perkins obtained the first patent for a vapor-compression refrigeration system, it used ether in a vapor compression cycle.
- Joule-Thomson (Kelvin) expansion
- Low pressure (1.5 atm) low temperature (-10 to +15 °C) inside
- High pressure (7.5 atm) high temperature (+15 to +40 °C) outside
[magnify]
Follow along with this discussion using vapor-compression.pdf.
Note: liquids are not ideal gases, liquids are nearly incompressible.
- compressor
cold vapor from the evaporator is compressed, raising it temperature and boiling point
adiabatic compression
T, b.p. ~ P
work done on the gas - condenser
hot vapor from the compressor condenses outside the cold box, releasing latent heat
isothermal, isobaric condensation (horizontal line on PV diagram)
high temperature
T (hot)
latent heat of vaporization Q (hot) - expansion valve (throttling valve)
hot liquid from the condenser is depressurized, lowering its temperature and boiling point
adiabatic, isochoric expansion (vertical line on PV diagram)
T, b.p. ~ P
no work done W = 0 - evaporator
cold liquid from the expansion valve boils inside the cold box, absorbing latent heat
isothermal, isobaric boiling (horizontal line on PV diagram)
low temperature
T (cold)
latent heat of vaporization Q (cold)
indicator diagram
vapor absorption refrigeration
Oliver Evans, USA, 1805, proposed but not built, evaporated sulfuric acid absorbed by water.
The first absorption machine was developed by Edmond Carré in 1850, using water and sulphuric acid. His brother, Ferdinand Carré developed the first ammonia/water refrigeration machine in 1859. Ferdinand Carré, France, ammonia absorption refrigerator, 1859. Established commercial success in the Confederate States during the US Civil War, since Union ice was not being transported to the South.
vapor absorption refrigerators can be powered by any heat source: natural gas, propane, kerosene, butane?
schematic diagram -- vapor-absorption-fridge.pdf
- generator
ammonia-water solution heated to generate bubbles of ammonia gas - separator
ammonia gas bubbles out of solution - condenser
ammonia gas condenses - evaporator
ammonia liquid evaporates - absorber
ammonia gas absorbed by water
indicator diagram
performance
not efficiency, but coefficient of performance
Carnot diagrams for refrigerators of increasing performance. [magnify]
refrigerants
These notes are a disaster.
The first true refrigerator (as opposed to an icebox) was built by Jacob Perkins in 1834. It used ether in a vapor compression cycle. The first vapor absorption refrigerator was developed by Edmond Carré in 1850, using water and sulfuric acid. His brother, Ferdinand Carré, demonstrated an ammonia/water refrigeration machine in 1859. Since 1834 more than 50 chemical substances have been used as refrigerants including …
- amines
- methyl amine
- ethyl amine
- chlorides
- ethyl chloride
- methyl chloride / methylene chloride
- ethers
- nitrous ether
- sulfuric ether / sulfuric (ethyl) ether
- halocarbons
The current standard refrigerants since the 1940s. See comments below.- chlorofluorocarbons (CFCs)
- hydrochlorofluorocarbons (HCFCs)
- hydrocarbons
In Europe, and particularly in Germany, simple hydrocarbon compounds are used in small quantities for domestic refrigerators. Due to their flammability and explosive potential, they are not suitable for applications requiring larger cooling capacities.- propane
- butane / isobutane
- sulfur compounds
- sulfur dioxide
Sulfur dioxide is a heavy, colorless, poisonous gas with a pungent, irritating odor familiar as the smell of a just-struck match. - sulfuric acid
- sulfur dioxide
- miscellaneous
- ammonia
Prior to the 1930s and 1940s, ammonia was the primary working fluid for vapor compression refrigeration. Largely abandoned for home use due to its toxicity, but still in widespread use in industrial applications. Also used in vapor-absorption refrigerators. - carbon dioxide
Used under higher pressure than the other fluids.
- ammonia
| Historical Introduction of Refrigerants | ||
| year | refrigerant / absorbant | chemical formula or makeup |
|---|---|---|
| 1830s | caoutchoucine | distillate of india rubber |
| 1830s | sulfuric (ethyl)ether | CH3CH2-O-CH2-CH3 |
| 1840s | methyl ether (R-E170) | CH3-O-CH3 |
| 1850 | sulfuric acid / water | H2SO4 / H2O |
| 1856 | ethyl alcohol | CH3-CH2-OH |
| 1859 | ammonia / water | NH3 / H2O |
| 1866 | chymogene | petrol ether and naphtha |
| 1866 | carbon dioxide | CO2 |
| 1860s | ammonia (R-717) | NH3 |
| 1860s | methyl amine (R-630) | CH3(NH2) |
| 1860s | ethyl amine (R-631) | CH3-CH2-(NH2) |
| 1870 | methyl formate (R-611) | HCOOCH3 |
| 1875 | sulfur dioxide (R-764) | SO2 |
| 1878 | methyl chloride (R-40) | CH3Cl |
| 1870s | ethyl chloride (R-160) | CH3-CH2Cl |
| 1891 | sulfuric acid with hydrocarbons | H2SO4, C4H10, C5H12, (CH3)2CH-CH3 |
| 1900s | ethyl bromide (R-160B1) | CH3-CH2Br |
| 1912 | carbon tetrachloride | CCl4 |
| 1912 | water vapor (R-718) | H2O |
| 1920s | isobutane (R-600a) | (CH3)2CH-CH3 |
| 1920s | propane (R-290) | CH3-CH2-CH3 |
| 1922 | dielene (R-1130) | CHCl=CHCl |
| 1923 | gasoline | hydrocarbons |
| 1925 | trielene (R-1120) | CHCl=CCl2 |
| 1926 | methylene chloride (R-30) | CH2Cl2 |
| 1940s | chlorofluorocarbons | CxFyClz |
| Source: | Trade-Offs
in Refrigerant Selections: Past, Present, and Future. James M. Calm and David A. Didion. Trane, Inc. |
|
The first mechanical refrigerators had to be connected to the sewer system to dispose of the refrigerant on a regular basis. In the 1930s and 1940s the halocarbon refrigerants (commonly known by such trade names as "Freon," "Genetron," "Isotron," etc.) were developed, giving the industry a strong push into the household market because of their suitability for use with small horsepower motors.
The most important members of the group have been
- trichloromonofluoromethane (R-11)
- dichlorodifluoromethane (R-12)
- chlorodifluoromethane (R-22)
- dichlorotetrafluoroethane (R-114)
- trichlorotrifluoroethane (R-113)
pause
- appropriately volatile
- low boiling points
- low surface tension
- low viscosity
- non reactive (stable)
- non toxic (vapor may be irritating, however)
- non corrosive
- non carcinogenic
- non flammable
Stable? Yes. Too stable! Stays around and accumulates in the atmosphere. Shifts the equilibrium between O2 and O3 in the stratosphere. global warming. Production of chlorofluorocarbons (CFCs) ended in 1995 in developed countries.
Production of R-12 was halted by the Clean Air Act on January 1, 1996. Today the remaining supplies are product which has been recovered and reclaimed back to a Chemically Pure State in accordance to ARI - 700 Standard. The ARI Standard is basically a virgin specification. Persons arguing that the supply of virgin product is still available is probably unrealistic, since most of the reserves were depleted in the 1st year. DoD Public Law prohibits the purchase of R-12 except for existing systems, when retrofit has been determined by technical staff to be prohibitive. Senior or Executive approval of this product to be purchased is required.
| CFC Trade Names | ||||
| trade name | corporation | trade name | corporation | |
|---|---|---|---|---|
| Arcton | Imperial Chemicals | Genetron | Allied Signal | |
| Daiflon | Daikin Industries | Halon | ASP International | |
| Eskimon | ?? | Isceon | Rhone-Poulenc | |
| Forane | Elf Atochem | Isotron | Pennsylvania Salt | |
| Freon | Du Pont | Jeffcool | Jefferson Chemical | |
| Frigen | Hoechst | Kaltron | Joh. A. Benckiser | |
| Ucon | Union Carbide | |||
| Properties of Freon 12 (25 °C and 1 atm except where indicated) | ||
| property | value | |
|---|---|---|
| generic name | R-12 | |
| chemical name | dichlorodifluoromethane | |
| chemical formula | CF2C2 | |
| molecular mass | 120.913 | u |
| color | none | |
| odor | ether-like | |
| flammability | non | |
| occupational exposure limit | 1000 | p.p.m. |
| boiling point | −29.75 | °C |
| melting point | −158 | °C |
| critical temperature | 111.97 | °C |
| critical pressure | 4136 | kPa |
| saturated vapor pressure | 652 | kPa |
| density, liquid | 1311 | kg/m3 |
| density, vapor | 36.83 | kg/m3 |
| specific heat capacity, liquid | 971 | J/kg·K |
| specific heat capacity, vapor | 617 | J/kg·K |
| latent heat of vaporization | 139.3 | kJ/kg |
| thermal conductivity, liquid | 0.0743 | W/m·K |
| thermal conductivity, vapor | 0.00958 | W/m·K |
| viscosity (+15 °C) | 0.20 | mPa·s |
| Physical Poperties of Some Significant Refrigerants | ||||
| property | ammonia | carbon dioxide | sulfur dioxide | freon 12 |
|---|---|---|---|---|
| formula | NH3 | CO2 | SO2 | CF2Cl2 |
| molecular weight | 17 | 44 | 64 | 121 |
| normal boiling point (°C) | −34 | −78 | −10 | −30 |
| latent heat (kJ/mol) | 24 | 25 | 25 | 22 |
| flammable | yes | no | no | no |
| pressure at 0 °C (atm) | 4 | 35 | 2 | 3 |
| pressure at 50 °C (atm) | 20 | > 60 | 9 | 12 |
| Source: Refrigerants for the 21st Century, William Gumprecht, ChemCases | ||||
Summary
- A refrigerator is any kind of enclosure (like a box, cabinet, or room) whose interior temperature is kept substantially lower than the surrounding environment.
- Types of Refrigerators
- non-mechanical
- for example: ice box, root cellar, wine cellar
- are not often considered true refrigerators
- mechanical
- vapor compression
- vapor absorption
- multievaporator, cascade
- gas cycle, air cycle
- pulse tube
- thermoacoustic
- electronic
- thermoelectric
- magnetic, magneto-calorific
- non-mechanical
- An air conditioner is a mechanical system in a room, building, or vehicle
for controlling …
- temperature (by providing cool air),
- humidity (by providing dry air),
- and ventilation (by providing fresh air).
- A heat pump is a device for moving heat
mechanically.
- A heat pump can move heat against the temperature gradient (from cold to hot).
- Refrigerators and air conditioners are examples of heat pumps.
- In common usage, the tem heat pump often refers to air conditioners
that can be run …
- "forward" to cool a building in summer by extracting heat from the building and depositing it in the environment (refrigerating the building and heating the environment) or
- "backward" to warm a building in winter by extracting heat from the environment and depositing it in the building (refrigerating the environment and heating the building).
- Energy is conserved in the operation of a heat pump.
- The heat extracted from the cold reservoir (Qc) plus the work done by the system (W) is equal to the heat deposted in the hot reservoir (Qh).
- The coefficient
of performance (COP) is the ratio of the useful energy output of
a system to the mechanical work required to operate it.
- The COP is a measure of the effectiveness of a mechanical device or system at performing some task.
- The COP of a heat pump used as …
- an air conditioner or refrigerator is the ratio of the heat extracted to the mechanical work required to operate it.
- a heater is the ratio of the heat deposited in the room to the mechanical work required to operate it.
| conservation of energy | coefficient of performance | |
|---|---|---|
| air conditioner and refrigerator | Qc + W = Qh | COP = Qc ∕ W |
| heat pump used for heating | Qc + W = Qh | COP = Qh ∕ W |
Problems
practice
- Write something.
- Answer it.
- Write something else.
- Answer it.
- Write something different.
- Answer it.
- Write something completely different.
- Answer it.
numerical
- problems
Resources
- general
- cold air refrigerator (ice box)
- Improved Process for the Artificial Production of Ice (pat. 8080, yr. 1851), John Gorrie, US Patent & Trademark Office
- refrigerants
- ammonia
- Ammonia Refrigerators, Ammonia Refrigeration Technicians Association (ARTA) <www.nh3tech.com>
- chlorofluorocarbons
- Groppi A, Polettini A, Lunetta P, Achille G, Montagna M. A fatal case of trichlorofluoromethane (Freon 11) poisoning. Tissue distribution study by gas chromatography-mass spectrometry. Journal of Forensic Science. Vol. 39, No. 3. (May 1994): 871-6.
- Ozone Depletion, Environmental Protection Agency (EPA)
- Ozone Secretariat, United Nations Environment Programme (UNEP)
- sulfur dioxide
- Bolton Hall HazMat Incident, University of Wisconsin, Milwaukee (14 July 2000)
- other
- Refrigerants for the 21st Century, William Gumprecht, ChemCases Properties of Refrigerants and Refrigerant Mixtures Database, NIST
- ammonia
- thermoacoustics
- Thermoacoustic Refrigeration, Pennsylvania State University
- vapor-compression refrigerator
- How Refrigerators Work, Marshal Brain, How Stuff Works
| Another quality webpage by Glenn Elert |
 |
home | contact bent | chaos | eworld | facts | physics |