**9. Hydrocarbons as refrigerants**

Hydrocarbon refrigerants, which do not contain any halogen atom, are promising substitute for CFC-12. Hydrocarbons are environmentally safe, efficient, and technologically reliable refrigerants and insulation foam-blowing agents. Hydrocarbons are naturally occurring substances formed from fossilized plant matter, and found throughout the world as oil and natural gas. Lower paraffin's such as propane, butane, and isobutene were successfully used as refrigerant before the advent of chlorofluorocarbons**.** The thermodynamic properties of the hydrocarbons are much better than any of the other alternatives known. (Refer the **Table 4**). Hydrocarbons are available at low price all over the world and are compatible with commonly used lubricants and materials of construction used in refrigeration systems. Hydrocarbons are relatively cheap to produce and they are readily available in most parts of the world.

The need to find substitutes for CFCs during the 1990s has led refrigeration industry back to using hydrocarbons which have no impact on the ozone layer and insignificant contribution to global warming. Since 1992, hydrocarbon refrigeration has become the technology of choice in many domestic markets in Western Europe. In Germany, 100 per cent of the industry has already converted to hydrocarbon technology. All of the major European companies, such as Bosch/Siemens, Electrolux, Liebherr, Miele, Quelle, Vest frost, Whirlpool, Bauknecht, Foron, and AEG are selling hydrocarbon refrigerators. They are available in many sizes, and a wide variety of models, including some with no-frost freezer compartments. There are over 100 different hydrocarbon refrigerator models on the European market.

The main drawback of these refrigerants is their high inflammability, which has prohibited their use. But modern innovations have greatly improved the safety of hydrocarbon technologies. Besides due to very low charge of hydrocarbons (the amount of propane or butane in a domestic hydrocarbon refrigerator is only 40 to 60 g equivalent to two to six cigarette lighters, depending on the size of the refrigerator) in small capacity refrigeration system inflammability does not present a problem The present level of technological development and safety measures available have made it possible to use hydrocarbons as working fluids in domestic refrigerators. Most consumers in Southern countries are already familiar with hydrocarbons in the form of LPG (liquid petroleum gas a propane and butane mix), as it is widely used for cooking in the home. According to Pearson of Star Refrigeration over 50 million refrigerators using hydrocarbon as a refrigerator have been produced and not a single accident due to flammability was reported. The main motivation to adopt hydrocarbons in spite of their high inflammability is their being **eco-friendly**. The hydrocarbons do not destroy ozone layer and their GWPs are hundred times lower than that of CFCs and ten times lower than other CFC substitutes. Among hydrocarbon pure fluids, propane and isobutene are finding much attention as a substitute to CFC-12 in recent years [14].

#### **9.1 Propane (HC-290)**

Propane has been tested in the small capacity refrigeration systems. Propane can be considered as an alternative for HCFC-22.The high latent heat requires low
