REFRIGERATION HISTORY AND BASICS CLASS NOTES

 

 

REFRIGERATION HISTORY AND

BASICS CLASS NOTES

Refrigeration is lowering of temperature.

Conventional & non-conventional methods

are in use.  Use Silica gel in

the drier cum filter to remove any

moisture. Use steel pipes with

ammonia. Use copper pipes with

halogenated hydrocarbon refrigerants.

PIONEERS IN REFRIGERATION

  1. Jacob Parkinson (1834) Proposed a hand operated compressor machine working on ether

  2. Gorrie’s (1851), air refrigeration machine

  3. Linde (1856) developed a refrigerating machine working on ammonia

  4. Du Pont (1940) developed new series of refrigerants (Fluoro-chloro derivatives of methane, ethane etc. under the trade name of FREONS).

  5. Carre (1860) developed vapor absorption system working on (ammonia+ water)

 PIONEERS IN AIR CONDITIONING

  1. W.H. Carrier (1876-1950) is the father of air conditioning.  He designed the first year round air conditioning system. It provided four major functions of heating, humidifying, cooling and dehumidifying.

  2. A.R. Wolff –He designed air conditioning system for hundred buildings.

PIONEERS IN CRYO-GENICS

  1. Pictet (1877) got the liquefaction of oxygen.

  2. Dewar (1898) made the famous Dewar flask to store liquids at cryogenics temperatures.

  3. Qnnes (1908) got the liquefaction of other permanent gases including helium. It lead to the discovery of super conductivity.

  4. Giauque and Debye (1926) independently proposed the adiabatic demagnetization of a Para-magnetic salt. It can create a temperature near absolute zero.

CONVENTIONAL METHODS OF REFRIGERATION

  1. Vapor compression refrigeration using a reciprocating/rotary/centrifugal compressor

  2. Air refrigeration / Gas refrigeration

  3. Vapor absorption refrigeration

NON CONVENTIONAL METHODS OF REFRIGERATION

  1. Steam-Jet water vapor refrigeration

  2. Thermo-electric refrigeration

  3. Vortex tube refrigeration

  4. Multi-evaporator single compressor refrigeration

  5. Multi-evaporator multi-compressor refrigeration

  6. Multi-compressor refrigeration

  7. Cascade refrigeration

  8. Manufacture of dry ice

  9. Liquefaction of gases by throttling and or reversible expansion

  10. Magnetic cooling

REFRIGERATION

Refrigeration is lowering of temperature. It is of three types.

(a) High temperature refrigeration

Refrigeration producing temperature much above oC. Examples are water coolers and summer air conditioners. It is high temperature refrigeration.

(b) Medium temperature refrigeration

Refrigeration producing temperatures between -2oC and + 2oC. Such applications are Cold stores and fridges. It is medium temperature refrigeration.

(iii) Low temperature refrigeration

Refrigeration producing temperature far below oC. Examples are manufacture of ice and ice cream. Even in a fridge, there is a freezer portion to make ice. It is low temperature refrigeration.

All the three types of refrigeration is achievable by the followings ways.

  1. Refrigeration by dissolving salts in water

  2. Refrigeration with phase change

Liquid to vapor—Freon’s, ammonia, Sulphur dioxide, carbon dioxide

Solid to liquid—natural ice, Solid to gas—dry ice

NOTE: Method 2 is most common. It is a fast method of cooling. Phase change causes large cooling.

3. Refrigeration by expansion of a perfect gas. Achieve  liquefaction of permanent gases.

4. Refrigeration by Magnetic Property- used in micro level study

5.Refrigeration by Thermo-electric property of thermo-couples/ semi conductors – Used for small cooling requirements.

6. Refrigeration by  a Vortex tube – Used for small cooling requirements.

7. Low temperature Refrigeration by Cascade refrigeration- Used for blood preservation and life saving drugs.

8. Low temperature refrigeration by Multi stage compression- Used for blood preservation and life saving drugs.

9. Air as refrigerant causes refrigeration. Air causes air conditioning of all the air crafts of the world.

10. Vapor absorption Refrigeration- used in a variety of practical applications.

11. Refrigeration by multi-evaporator with a single compressor- Used in malls and food processing industries.

12.  Refrigeration by multi-evaporator with multi compressor with single stage compression- Used in malls and food processing industries.

13. Refrigeration by multi-evaporator with multi compressor and multi – stage compression- Used in malls and food processing industries.

TON OF REFRIGERATION

UNIT OF REFRIGERATION (TR)

 1 ton of refrigeration= 1 TR = 211 k J/min

   Measure length in meters.  Measure refrigeration in tons of refrigeration (TR).

1 TR means removal of heat at the rate of 211 kJ/min.

 Achieve value of 211 as follows:

  Heat extracted converts 2000 pounds of water at 320 F into ice at 32 F in 24 hours.

  Conversion of 1 pound of water into 1 pound of ice at 320F extracts 144 BTU.

Heat removed from 2000 pounds in 24 hours will be

= 2000 x 144.  BTU

 Heat removed per minute is = 2000 x 144 / (24 x 60) =200 BTU/min=211 kJ/min

1  Ton = =211 kJ/min=200 BTU/min = 50 k Cal/min

NOTE:    1 BTU=1.055 kJ

 12000 BTU =3025 kcal

1kcal=4.187 kJ)

CALCULATING TONS OF REFRIGERATION

1.  Cooling of air

TR = m. Cp (t exit of refrigerator –t entering refrigerator)/211 = m cdt/ 211

Where m. is rate of air mass flow/min

Cp is the specific heat of air at constant pressure

dt is the decrease of temperature

2. Cooling medium is moist air in an air conditioning 

TR = V.ρ (h in –h out)/211

Where V. is volumetric flow rate of air in Fan Coil Unit or Air Handling Unit

ρ is the density of air

h in is the enthalpy of moist air entering the air conditioner

h out is the enthalpy of moist air leaving the air conditioner

3. Refrigerant phase change causes cooling like R-22 and ammonia

TR = m. (h out –h in)/211

Where m. is rate of mass flow of refrigerant/min

h in is the enthalpy of air entering the evaporator

h out is the enthalpy of air leaving the evaporator 

THUMB RULE FOR 1 TR

(i)   10 m2 floor area in a small office/shop/home

(ii)    25 m2 floor area in a large building hall/complex

(iii)   15 persons in a cinema hall

(iv)   17 m2 floor area in a cinema hall

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