An extensive literature search is conducted to identify 445 potential R-11, R-113, and R-114 replacement refrigerants for high-temperature heat pumping applications. Once more restrictive sorting criteria are imposed and once the search is limited to R-114 replacements, the viable candidates are reduced to fifty-six, namely, thirty-six pure fluids and twenty low temperature glide zeotropes.

Prior to analyzing the fifty-six potential replacement refrigerants in detail, the Peng-Robinson Equation of State is used to determine the optimum thermodynamic parameters for R-114 replacements in high-temperature heat pumping applications. The critical temperature, the ideal gas specific heat at constant pressure, and the acentric factor are shown to be the three thermodynamic parameters which determine the performance (Heating Coefficient of Performance and Volumetric Heating Capacity, COP_H and VHC, respectively) of refrigerants operating in idealized vapor compression refrigeration cycles. It is shown that: (1) The optimal range of critical temperature depends on the desired VHC. (2) To maximize COP_H, the ideal gas specific heat at constant pressure (evaluated at the critical temperature) should have values ranging from approximately 48 kJ kmol^-1 K^-1 (11.5 Btu lbmol^-1 °R^-1) to approximately 104 kJ kmol^-1 K^-1 (24.9 Btu lbmol^-1 °R^-1), and to increase VHC, the ideal gas specific heat at constant pressure (evaluated at the critical temperature) should have values less than approximately 138 kJ kmol^-1 K^-1 (33.0 Btu lbmol^-1 °R^-1). (3) To increase COP_H, the acentric factor should have larger values, and to increase VHC, the acentric factor should have smaller values. Therefore, trade-offs become necessary due to the conflict between COP_H and VHC.

Then, the report demonstrates, through several examples of potential R-114 replacement refrigerants, the step-by-step procedure to implement the methodology described in, for example, Reid et al. (1987) and Poling et al. (2001)—and illustrated in recent publications by Brown (2007a, 2007b)—for evaluating the thermodynamic performance potentials of alternative refrigerants. This methodology allows one to estimate quickly and easily several key thermodynamic parameters, namely, critical temperature, critical pressure, critical density, ideal gas specific heat at constant pressure and acentric factor from knowing only a refrigerant’s normal boiling point temperature and its molecular structure. Once these key parameters are known, the Peng-Robinson Equation of State formulation implemented in REFPROP 8.0 (Lemmon et al. 2007) easily can be used to predict a refrigerant’s Heating or Cooling Coefficient of Performance and Volumetric Heating or Cooling Capacity. The power of this methodology is that one can predict easily and quickly the performance potentials of a large number of refrigerants that are not-so-well-described, as well as ones that are, limiting the need for expensive and time consuming experimentation or detailed equation of state modeling. Then, once this preliminary investigation is complete, one can focus on a shortened, much more limited list of potential replacement refrigerants.

Finally, this methodology is used to evaluate fifty-six potential R-114 replacement refrigerants for high-temperature heat pumping applications. In particular, the fifty-six refrigerants consist of thirty-six pure fluids and twenty low temperature glide zeotropes. An idealized vapor compression refrigeration cycle is used to estimate the performance potentials (Coefficient of Performance and Volumetric Heating Capacity) of the fifty-six refrigerants. In addition to the Coefficient of Performance and Volumetric Heating Capacity, other basic cycle data are provided for each refrigerant. Furthermore, some other relevant data, i.e., global warming potential, flammability, and toxicity are provided. Of the fifty-six refrigerants, thirteen of them should receive further consideration as potential R-114 replacement refrigerants. Three of them—R-245eb, R-245ca, and R-245fa are lower-pressure fluids (implying larger systems); eight of them—SF5CF2H, R-E236fa, R-E245cb1, R-236ca, R-236ea, R-143, R-236cb, and R- 254cb—have similar operating pressures (implying similarly sized systems); and two of them— R-764 and R-717 are higher-pressure fluids (implying smaller systems) with high compressor discharge temperatures.

Units: Dual