25-08-2014, 12:33 PM
DOMESTIC LPG REFRIGERATOR SEMINAR REPORT
DOMESTIC LPG REFRIGERATOR.docx (Size: 1.65 MB / Downloads: 122)
ABSTRACT
Domestic refrigerators annually consume approximately 17,500 metric tons of traditional refrigerants such as Chlorofluorocarbon (CFC) and Hydroflourocarbon (HFC) which contribute to very high Ozone Depletion Potential (ODP) and Global Warming Potential (GWP). Good progress is being made with the phase out of CFC 22 from new equipment manufacture by replacing LPG since it possesses an environmentally friendly nature with no ODP. LPG is expected to results in comparable product efficiencies based on its characteristics. Therefore, this two types of refrigerants (LPG and CFC 22) to be examined using a modified domestic refrigerator in term of their performance characteristics parameters such as pressure and temperature at specified location at the refrigerator and the safety requirements while conducting the experiment. Based on the present work, it is indicate that the successful of using LPG as an alternative refrigerant to replace CFC 22 in domestic refrigerators is possible by getting LPG COP as 13 compared to 10 for CFC22.
INTRODUCTION
In India, more than 80% of the domestic refrigerator utilize HFC 134a as refrigerant, due to its excellent thermodynamic and thermo physical properties. But, HFC 134a has a high global warming potential (GWP) of 1300. There is a need of assess various refrigerant option considering the existing refrigerators in the field and for the future market.
CFC’s are principally destroyed by ultraviolet radiations in the stratosphere; the chlorine released in the high stratosphere catalyzes the decomposition of ozone to oxygen; and ultraviolet radiations penetrates to lower altitudes. Credible calculations of the magnitude of the effect (Hoffman 1987) and his team predicted 3% global ozone emissions of 700 thousand tonnes/year after a hundred years. The ozone impact of car air conditioners also can not be ignored. Hydrofluorocarbons (HFC’s) can be thought of as a replacement, but unfortunately the radiation properties of HFC’s like R-134a make them powerful global warming agents. HFC 134a and the HC blend have been reported to be substitutes for CFC 12, but they have their own drawbacks in energy efficiency, flammability and serviceability aspects of the systems. HFC 134a is not miscible with mineral oil, and hence, polyol ester oil is recommended, which is highly hygroscopic in nature. This hygroscopicity demands stringent service practices, which otherwise results in moisture entry into the system.
Thus, hydrocarbon refrigerants; particularly LPG serves as the best contender to replace CFC’s from domestic refrigerator as well as car air conditioners.
LPG consists mainly of propane (R-290) and butane (R-600), and LPG is available as a side product in local refineries. In Cuba for already several decades LPG is used as a drop-in refrigerant. LPG mixtures have composition of a commercial LPG mixture suitable as ‘drop-in’ replacement for R-12 was calculated crudely as 64% propane and 36% butane by mass. Liquefied petroleum gas (LPG) of 60% propane and 40% commercial butane has been tested as a drop-in suitable for R 134a in a single evaporator domestic refrigerator with a total volume of 10 ft3.
Combustion
The combustion of LPG produces carbon dioxide (CO2) and water vapour but sufficient air must be available. Inadequate appliances flueing or ventilation can result in the production of carbon monoxide which can be toxic.
Vapour Pressure
LPG is a stored as a liquid under pressure. It is almost colourless and its weight is approximately half that of an equivalent volume of water. The pressure inside a closed container in which LPG is stored is equal to the vapour pressure of the liquid and corresponds to its temperature.
LPG GAS CYLINDER
LPG is Liquefied Petroleum Gas. This is general description of Propane (C3H8) and Butane (C4H10), either stored separately or together as a mix.
This is because these gases can be liquefied at a normal temperature by application of a moderate pressure increases, or at normal pressure by application of LPG using refrigeration. LPG is used as a fuel for domestic, industrial, horticultural, agricultural, cooking, heating and drying processes. LPG can be used as an automotive fuel or as propellant for aerosol, in addition to other specialist applications. LPG can also be used to provide lighting through the use of pressure lanterns
CAPILLARY TUBE
The capillary tube is the commonly used throttling device in the domestic refrigeration. The capillary tube is a copper tube of very small internal diameter. It is of very long length and it is coiled to several turns so that it would occupy less space. The internal diameter of the capillary tube used for the refrigeration applications varies from 0.5 to 2.28 mm (0.020 to 0.09 inch). The capillary tube is shown in picture. When the refrigerant enters in the capillary tube, its pressure drops down suddenly due to very small diameter. The decrease in pressure of the refrigerant through the capillary depends on the diameter of capillary and the length of capillary. Smaller is the diameter and more is the length of capillary more is the drop in pressure of the refrigerant as it passes through it.
EVAPORATOR
The evaporators are another important parts of the refrigeration systems. It through the evaporators that the cooling effect is produced in the refrigeration system.It is in the evaporators when the actual cooling effect takes place in the refrigeration systems. For many people the evaporator is the main part of the refrigeration system, consider other part as less useful. The evaporators are heat exchanger surface that transfer the heat from the substance to be cooled to the
refrigerant, thus removing the heat from the from the substance. The evaporators are used for wide variety of diverse application in refrigeration and hence the available in wide variety of shape, sizes and designs. They are also classified in different manner depending on the method of feeding the refrigerant, construction of the evaporator, direction of air circulation around the evaporator, application and also the refrigerant control.
In the domestic refrigerators the evaporators are commonly known as freezers since the ice is made in these compartment.
In the evaporators the refrigerant enters at very low pressure and temperature after passing through the capillary tube. This refrigerant absorbs the heat from the substance that is to be cooled so the refrigerant gets heated while the substance gets cooled. Even after cooling the substance the temperature of the refrigerant leaving the evaporator is less than the substance.
In the large refrigeration plants the evaporator is used for chilling water. In such cases shell and tube type of heat exchanger are used as the evaporators. In such plants the evaporators are classified as:
PRESSURE GAUGES
Many techniques have been developed for the measurement of pressure and vacuums. Instruments used to measure pressure are called pressure gauges or vacuum gauges.A manometer could also referring to a pressure measuring instrument, usually limited to measuring pressures near to atmospheric. The term manometer is often used to refer specifically to liquid column hydrostatic instruments.
BOURDON GAUGE
A Bourdon gauge uses a coiled tube, which, as it expands due to pressure increases cases a rotation of an arm connected to the tube.In 1849 the Bourdon tube pressure gauge was patented in France by Eugene Bourdon. The pressure sensing element is a closed coiled tube connected to the chamber or pipe in while the pressure is to be sensed. As the gauge pressure increases the tube will tend to uncoil, while a reduced gauge pressure will patented France by Eugene Bourdon.
The pressure sensing el cause the tube to coil more tightly. This motion is transferred through a linkage to a gear train connected to an indicating needle. The needle in presented in front of a card face inscribed with the pressure indications associated with particular needle deflections. In a barometer, the Bourdon tube is sealed at both ends and the absolute pressure of the ambient atmosphere is sensed. Differentials Bourdon gauges use two Bourdon tubes and a mechanical linkage that compares the readings
CONSTRUCTION OF THE LPG REFRIGERATOR
The LPGrefrigerator shown in figure. We make the one box of the plywood. The plywood sheet size is 12mm for used the LPG refrigerator. The size of the refrigerator is 724*457*381 mm3. The evaporator is fitted on the upper portion of box insideInside the refrigerator, we also put the thermo-coal sheet, because of the cold air cannot the transfer from inside to outside of refrigeratorThe schematically diagram of the LPG refrigeration system is shown in next page. The gas tank is connect by pipes to the capillary tube. The capillary tube is fitted with evaporator. The evaporator coiled end is connect to the stove by another gas circulation pipe. When two pressure gauge is put between capillary tube and gas tank, and another is put the end of the evaporator.
WORKING LPG REFRIGERATOR
The basic idea behind LPG refrigeration is to use the evaporation of a LPG to absorb heat. The simple mechanism of the LPG refrigeration working is shown in figure.
CAUSES AND PRECAUTION
• Explosion in space Any refrigerant with vapour pressure above ambient can flash to a larger volume. The potential increase in volume is greater if combustion of lubricant or refrigerant occurs. Explosion venting may be necessary to limit pressure rise to what the space can safely withstand. 2 kPa can blow window glass off a building.
• Fire Combustible lubricant and refrigerant must be discharged safely outside a building when a fire occurs especially if the heat of combustion exceeds 200 MJ.
• Asphyxiation or poisoning All refrigerants except air and oxygen are asphyxiations. Ventilation must prevent serious injury or death on a sudden total release of refrigerants. The quantity of ventilation necessary varies greatly between refrigerants.
• Flying metal System must comply with piping and pressure vessels codes.
• Corrosion or chemical reaction LPG refrigerants are non-reactive and chemically stable at refrigeration temperature.
• Chemical or cold burns Accidental contact between skin and cold metal must be prevented by insulation. Accidental releases of liquid refrigerant must drain safely.
CONCLUSION
After performing this project “LPG Refrigeration”, we conclude that refrigeration effect is produced with the use of LPG.
From observation table, we conclude that, the regulating valve is fully open that, we achieve the chamber temperature down from 38ºC to 10ºC in a 100 minute. We achieve the evaporator temperature down from 1ºC to -9.3ºC in a same time interval.
We put the water in one plastic bottle in the evaporator. The initial temperature of water is 35 ºC. From observation table, we conclude that, the condition of regulating valve is fully opened, the same time period we achieve the temperature of water is 0.30 ºC.
We also conclude that, the capillary tube is maximum pressure of gas cylinder is reduces the less then of 1 psi. The capillary tube is more suitable throttling device in LPG refrigeration system.
This system is cheaper in initial as well as running cost. It does not require an external energy sources to run the system and no moving part in the system so maintenance is also very low.
We also conclude that, we try the burnt to the exhaust LPG, the pressure of exhaust gas is less than 1 psi, the small flame produce by the burner.
This system most suitable for hotel, industries, refinery, chemical industries where consumption of LPG is very high.