Propene/isobutane mixtures in heat pumps: An experimental investigation

Fluid Retrofit for Existing Vapor Compression Refrigeration Systems and Heat Pumps: Evaluation of Different Models

“…For example, propane showed in the experiments a maximum evaporation temperature of 7.33 • C and an isentropic compressor efficiency of 52%, whereas the values for R134a, which were also the basis for the calculation of propane, are 9.89 • C and 47% ( Table 1). The isentropic compressor efficiency is of special importance since it differs significantly for different fluids (e.g., isobutane: 46%, propene: 64%) and also has a large influence on the COP of the entire process [11]. The marginal differences in the calculated COPs in the simulation level I were therefore only due to deviating fluid properties such as the evaporation enthalpy or the heat capacity ratio (κ = c p /c v ).…”

“…If instead a replacement fluid for a given existing system is needed then things change because e.g., it can no longer be assumed that the compressor will work equally well with any fluid. Similar approaches are seen in experimental studies which investigate the general suitability and efficiency of different fluids in a laboratory scale test-rig [6,[11][12][13] or in single components like compressors or heat exchangers [14][15][16]. These investigations often lead to interesting heuristics, but they are not very helpful in finding replacement fluids for a concrete plant since the COP, heat flow rates and compressor power of another concrete system will have with a different fluid cannot be estimated.…”

“…The secondary mass flow rates in the heat exchangers were also adjustable and were calibrated gravimetrically. The exact specifications of the system components and installed instrumentation can be found in Reference [11]. The recording and processing of the measured values were carried out in LabVIEW [17], while enthalpies, entropies and further thermodynamic properties were calculated with REFPROP [18].…”

Heat pump working fluid selection—economic and thermodynamic comparison of criteria and boundary conditions

“…Such comparisons, as recently performed by e.g. Venzik et al (2017), may only be considered as reasonable when the comparison seeks to find a fluid for an application with constant temperature reservoirs, or when second law efficiencies are used to compare the performances, because they only compare the cycle performance, while neglecting the integration into the boundary conditions. However, the main benefit of mixed working fluids does not lie within the internal cycle itself, but rather in a better integration into boundary conditions with temperature glides, meaning a more efficient heat transfer at smaller temperature differences to sink and source.…”

Analysis of temperature glide matching of heat pumps with zeotropic working fluid mixtures for different temperature glides

“…Many numerical and experimental studies were conducted in order to optimize the heat pump performance for a specific application by choosing from a limited set of mixtures and analyze operational issues in experimental setups, e.g. [12]. A comprehensive review about this topic was conducted by Mohanraj et al in [6].…”