Hydrocarbons as Alternatives

Notes POE = polyolester PAG = polyalkylene glycol safety group = (A or B) lower and high toxicity, respectively (1, 2, or 3) not flammable, low and high flammability. a GWP for integrated time horizon and based on 3,500 kg C02 per kilogram of R11. 

Hydrocarbons such as R290 have been in use for years because they have good thermodynamic and transport properties, as well as low cost and low toxicity [7], Large refrigeration plants in the petrochemical industry typically use R290. Household appliance manufacturers in Europe use isobutene (R600a) [7], In all, U.S. auto manufacturers do not want the potential liability issues associated with the use of a hydrocarbon as a potential refrigerant [7], 

Knowledge of chemical structures and how molecules will behave based on those structures is a great asset in predicting refrigerant response. As Table 9.6 shows, the evaporator temperatures and thus much of the cooling is similar to that of R1345a without the detrimental environmental effects. 

Surface tension (mN/m) Liquid density (kg/m3) Vapor density (kg/m3) Liquid viscosity (uPa.s) Vapor viscosity (uPa.s) 

Liquid specific heat (kJ/kg K) Vapor specific heat (kJ/kg K) 

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Hence, naphthalene, phenanthrene, pyrene, and biphenylene are alternant hydrocarbons, while azu-lene, pyracylene, and its isomers are non-alternant conjugated hydrocarbons. The idea of classification of hydrocarbons as alternant and non-alternant goes back to Coulson and Longuet-Higgins and the early days of HMO theory. An important property of alternant hydrocarbons, as opposed to non-alternant, is that for alternant systems all HMO eigenvalues come in pairs Xu while this is not the case for nonalternant systems. It is interesting to mention that this particular mathematical property of alternant... 

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