LPG as Refrigerant

Kiran Pagar — Sat, 12 Sep 2009 11:37:53 +0000

Brief Information About LPG as Refrigerant

In India, more than 80 % of the domestic refrigerators utilize HFC134a as refrigerant, due to its excellent thermodynamic and thermo physical properties. But, HFC134a has a high global warming potential (GWP) of 1300. There is a need to assess various refrigerant options 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 radiation penetrates to lower altitudes. Credible calculations of the magnitude of this effect (Hoffman 1987) and his team predicted 3% global ozone depletion for constant CFC emissions of 700 thousand tonnes/year after a hundred years. The ozone impact of car air conditioners also cannot 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. HFC134a and the HC blend have been reported to be substitutes for CFC12, but they have their own drawbacks in energy efficiency, flammability and serviceability aspects of the system. HFC134a 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 refrigerators 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 substitute for R134a in a single evaporator domestic refrigerator with a total volume of 10 ft3.

LPG can offer following advantages when used as a refrigerant:

1)   The cooling capacity of LPG is 10% higher than R-12 and the vapour pressure is appropriate.
2)   LPG is naturally occurring and non-toxic.
3)   Use of LPG as a refrigerant also improves the overall efficiency by 10 to 20%.
4)   The ozone depletion potential (ODP) of LPG is 0 and global warming potential (GWP) is 8 which is significantly negligible as compared to other refrigerants.
5)   Apart from environment friendly, use of LPG also gives us lot of cost advantages.
6)   LPG does not form acids and thereby eliminates the problem with blocked capillaries.
7)   There is 60% reduction in weight of the system due to higher density of LPG.

The only disadvantage of using LPG as a refrigerant is its flammability. It is highly flammable. This paper elaborates various precautions that need to be taken to safely use LPG as a refrigerant. The amount of LPG used for each appliance should be too small in order to avoid any risk for technicians and customers. Thus by minimizing the possibility of leak and following some international standards, the use of LPG as a refrigerant can be safely implemented.

Emissions

Kiran Pagar — Thu, 10 Sep 2009 06:21:35 +0000

Emission:

Whenever, any fuel is burnt, we receive energy as main product and many other products. In general we will call them as”Emissions”. So, Emission is product of combustion of fuels which may contain, smoke, carbon monoxide, sulphur compounds, particulates, nitrogen compounds (popularly known as NOX) fumes etc.

Need For Emission Control:

In 20th century, growing technology have handed us with great machines and gadgets. One of them is Internal Combustion Engine (I.C. Engine). Growing technology demanded for more use of energy which we extracted from burning of fuels. This have lead us to the most horrible problem today “Air Pollution”. Air pollution is simply the presence of undesirable gases in undesirable quantities in the air. This have lead to more serious phenomenon of Global Warming. These are just main problems but there are so many local problems which may differ place to place.

Main source of emission is fuel burnt in the I.C. Engine (about 42% of overall emissions).

Emission Details:

1. Emissions from Spark Ignition Engine:

Major emission from S.I. Engine are listed below.

Carbon Monoxide (CO).
Hydrocarbons (HC).
Oxides of Nitrogen (NOX).

2. Emissions from Compression Ignition Engine:

Major emissions from C.I. Engine are listed below.

Carbon Monoxide (CO).
Unburnt Hydrocarbons (HC).
Oxides of Nitrogen (NOX).
Sulphur Di Oxide.
Invisible Emissions.
Metallic Particulates.
Visible Emissions.
Smoke.

So, from these lists we can say that diesel engines are more harmful to environment than that of petrol one.

This is the brief information of emission sources and emissions. We will see in detail about emission control in next article.

References:

[1] http://en.wikipedia.org/wiki/Air_pollution

[2] http://www.naturalnews.com/emissions.html

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