Refrigerators

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:

  1. ice box (or dry ice box)
  2. cold air systems
  3. 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)
  4. vapor-absorption: the Electrolux refrigerator with no moving parts
  5. 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 Siemens 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.


[slide]

Follow along with this discussion using vapor-compression.pdf.

Note: liquids are not ideal gases, liquids are nearly incompressible.

  1. 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
  2. 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)
  3. 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
  4. 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

  1. generator
    ammonia-water solution heated to generate bubbles of ammonia gas
  2. separator
    ammonia gas bubbles out of solution
  3. condenser
    ammonia gas condenses
  4. evaporator
    ammonia liquid evaporates
  5. absorber
    ammonia gas absorbed by water

indicator diagram

performance

not efficiency, but coefficient of performance

COPreal = QC
QH − QC
COPideal = TC
TH − TC


[slide]

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 …

year refrigerant chemical formula
1830s caoutchoucine (distillate of india rubber)
1830s ethyl ether CH3CH2-O-CH2-CH3
1840s methyl ether (R-E170) CH3-O-CH3
1850 sulfuric acid H2SO4/H2O
1856 ethyl alcohol CH3-CH2-OH
1859 ammonium hydroxide NH3/H2O
1866 chymogene (petrol ether and naphtha)
1866 carbon dioxide CO2
1860s ammonia (R-717) NH3
1860s methylamine (R-630) CH3-NH2
1860s ethylamine (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 blended with hydrocarbons
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 dichloroethene (R-1130) CHCl=CHCl
1923 gasoline  
1925 trichloroethylene (R-1120) CHCl=CCl2
1926 methylene chloride (R-30) CH2Cl2
1940s chlorofluorocarbons CxFyClz
Historical introduction of refrigerants
Source: Radermacher and Hwang, University of Maryland

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

pause

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.

trade name corporation   trade name corporation
Arcton Imperial Chemicals   Halon ASP International
Daiflon Daikin Industries   Isceon Rhone-Poulenc
Eskimon ????   Isotron Pennsylvania Salt
Forane Elf Atochem   Jeffcool Jefferson Chemical
Freon Du Pont   Kaltron Benckiser
Frigen Hoechst   Khladon ????
Genetron Allied Signal   Ucon Union Carbide
CFC Trade Names
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
melting point −158
critical temperature 111.97
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 ℃) 0.20 mPa s
Properties of Freon 12
(25 ℃, 1 atm except where indicated)
property ammonia carbon dioxide sulfur dioxide freon 12
formula NH3 CO2 SO2 CF2Cl2
molecular weight 17 44 64 121
normal boiling point (℃) −34 −78 −10 −30
latent heat (kJ/mol) 24 25 25 22
flammable yes no no no
pressure at 0 ℃ (atm) 4 35 2 3
pressure at 50 ℃ (atm) 20 > 60 9 12
Physical poperties of some significant refrigerants Source: William Gumprecht, Kennesaw State University