ASSESSING THE DESIGN AND FABRICATION OF DOMESTIC DEEP FREEZER
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This project is on the design and fabrication of deep freezer for the preservation of items/products and making the items to cool.
The project is able to develop a simple efficient economical and environmental friendly refrigeration system (A freezer) towards better technological advancement in Nigeria.
This project modifies the existing refrigeration system with the use of R-600a which is ozone friendly, and non-contaminant like previous refrigerant of the hydrofluoric-carbon, HFC and CFC like R-12, and R22 which has been phased out according to the general convection at Britain in 1996.
The cooling load obtained was 10682KW, and co-efficient of performance be minimized.
The material used were mild steel and the inner pipe of the cabinet i.e. evaporator in order to minimize corrosion.
For the better improvement of this work, low power consumption of the compressor refrigeration was used so as to maintain the rate of cooling and freezing of large items/products.
And the outer dimensions are: length-1245mm, breadth-895mm-0. 895m, Height-906mm-0.96m and the inner dimensions are Iength-1225mm-1.225m; Breadth-895mm-0.895m, Height-886mm- 0.886m.
The ice cream being sold at the corner stores, the frozen vegetable for dinner, the refreshing water for drinking at the office, water cooler are all dependent on the science of refrigeration.
Refrigeration in its specialized forms in a comparative modern development which has been in practice for generations, and its application in controlling environmental condition has made possible some outer space programs and many other scientific and commercial activities as it can be obtained in our houses and on the farm which is considered as an example of a natural refrigeration techniques, the porous clay jugs used in hot desert countries for cooling water, the ice box, for food preservation etc. (Raymond, C.G. (1973).
This write up presents the principle of mechanical refrigeration in vapor compression refrigeration system and it application which gives a clear understanding about the design and operation of the unit.
1.1 LITERATURE REVIEW
Refrigeration is branch of engineering that is concerned with the science of producing and maintaining temperature below that of the surrounding atmosphere [Raymond, C.G. (1973)].
It also the process of removing heat from the substance.
Before the advent of mechanical refrigeration, water was kept cool by storing in semi-porous pots, so that the water could seep through and evaporate.
The evaporation carried away heat and cooled the water [Raymond, C.G. (1 973)].
The first development took place in 1834 when Perkins proposed a hand operated compressor working machine.
In 1851 came Gorries and in 1856 Lind developed a machine working on ammonia [Andrew, D. & Alfred, (1970)].
The development was considered quickened in the forties when Dupent put in the market, a family of new working substances, the floor chloro derivate of methane,1 ethane etc. under the name of ferons; then followed the liquefaction of other permanent gases included helium in 1908.
[Andrew, D. & Alfred, F.B. (1970)].
In 1926, Ginque and Diebye independently proposed adiabatic demagnetization of a paramagnetic salt.
In 19th century application of mechanical refrigeration in fields other than ice making including direct cooling and freezing of perishables foods, air conditioning for industry and human comfort [[Andrew, D. & Alfred, F. B. (1970)].
1.2 GENERAL DEFINITION AND DEVELOPMENT
Refrigeration may be defined as the process of removing heat from a substance.
The American society of Engineers defines refrigeration as “the science of producing and maintaining temperature below that of the surrounding atmosphere”.
This implies the development of temperature differential rather than the establishment of a given temperature level.
Therefore refrigeration is accomplished by establishing temperatures differentials and evaporation of liquids or combination of both methods for removing heat from a substances in a refrigeration i.e. heat is put into the working substance at lower pressure and temperature and provide the latent heat to make it boil and change to vapor.
The vapor is then compressed to a high pressure and temperature at which the superheated gas can be removed and the fluid is turn to liquid.
The total cooling effect will be the heat transferred to the working fluid in the evaporator [Raymond, C. G. (1973)].
In any refrigeration process, three basic factors are involved which are: Heat change, pressure control and liquid gas relationship, therefore a working system will require a connection between the condenser and the inlet to the evaporator to complete the circuit.