The energy separation and the increase of heating effect and the decrease of cooling effect in the vortex tube with various gases, such as R41, R32, R23, R290, R134a, R1234yf, was studied in the numerically simulated. The pressure field and temperature field and velocity field of the vortex tube were analyzed with R41. The results show that the R41 in the vortex tube, the cold and hot performance will best, the maximum temperature difference what be between cool area and hot area is 5.2 K. The numerical results show that flow motion inside the vortex tube presents extraordinary complicated behavior; The flow inside the vortex tube exist an outer region of quasi-free vortex flow and an inner region of quasi-forced vortex flow; there are the parallel flow, reverse flow and secondary flow in the vortex tube, The interface between parallel flow and reverse flow is that the energy separation place in the vortex tube.

Unfavorable transport properties have always been pointed out as the key factors that hinder the application of ammonia/ionic liquids (NH ₃ /ILs) in absorption cycles, while heat and mass transfer of these new fluids in components have been rarely reported. In this study, a corrugated plate heat exchanger is selected as the geometry for exploring the absorption of NH ₃ in the proposed NH ₃ /ILs working fluids. The process is studied making use of a semi-empirical framework: experimental data is needed to determine unknown information of heat and mass transfer, and a numerical model is developed making use of frequently applied theories. In addition, relevant transport properties of the NH ₃ /ILs working fluids are modeled based on collected experimental data. The proposed model is used to study the heat and mass transfer performance during the absorption of NH ₃ vapor into NH ₃ /ILs fluids. Distribution of local parameters and overall heat and mass transfer characteristics are obtained. The performance of absorption of NH ₃ into different working fluids is investigated as well. The overall heat transfer coefficient is found around 1.4 kW/(m ² ·K) for the most promising working fluid NH ₃ /[emim][SCN].

Increasing helium use in research and production processes necessitates separation techniques to secure sufficient supply of this noble gas. Energy-efficient helium production from natural gas is still a big challenge. Membrane gas separation technology could play an important role. Herein, a novel poly(p-phenylene benzobisimidazole) (PBDI) polymeric membrane for helium extraction from natural gas with low He abundance is reported. The membranes were fabricated by a facile interfacial polymerization at room temperature. The thin and defect-free membrane structure was manipulated by the confined polymerization of monomers diffusing through the interface between two immiscible liquids. Both He/CH₄ selectivity and He permeance are competitive over those of other commercial perfluoropolymers. Even at low He content of 1%, separation performance of the PBDI membrane transcended the current upper bound. The unprecedented selectivity (>1000) together with the excellent stability (∼360 h) endows PBDI membranes with a great potential for energy-efficient industrial recovery and production of this precious He resources from reservoirs with low abundance.

Negative transport properties have always been pointed out as the key factors that hinder the application of ammonia/ionic liquids (NH3/ILs) in the absorption cycles, while heat and mass transfer of these new fluids in components have been rarely reported. The authors selected corrugated plate heat exchangers as the geometry to explore the absorption of the proposed working fluids. In this paper, a modeling method and a continuous absorption-desorption setup are introduced. Absorption process is modeled with the two-resistance theory by introducing a gas-liquid interface. Analytical heat transfer results and mass transfer from penetration theory are applied. With the model, distribution of local parameters and overall heat and mass transfer characteristics of an absorber in a cooling application are obtained. The overall heat transfer coefficient of an absorber for a refrigeration application is around 1350 W/(m²K) for the studied NH3/IL working fluids. An experimental setup is developed for further model improvement.

For absorption refrigeration, it has been shown that ionic liquids have the potential to replace conventional working pairs. Due to the huge number of possibilities, conducting lab experiments to find the optimal ionic liquid is infeasible. Here, we provide a proof-of-principle study of an alternative computational approach. The required thermodynamic properties, i.e., solubility, heat capacity, and heat of absorption, are determined via molecular simulations. These properties are used in a model of the absorption refrigeration cycle to estimate the circulation ratio and the coefficient of performance. We selected two ionic liquids as absorbents: [emim][Tf₂N], and [emim][SCN]. As refrigerant NH₃ was chosen due to its favorable operating range. The results are compared to the traditional approach in which parameters of a thermodynamic model are fitted to reproduce experimental data. The work shows that simulations can be used to predict the required thermodynamic properties to estimate the performance of absorption refrigeration cycles. However, high-quality force fields are required to accurately predict the cycle performance.

Ionic liquids (ILs), as novel absorbents, draw considerable attention for their potential roles in replacing water or LiBr aqueous solutions in conventional NH₃/H₂O or H₂O/LiBr absorption refrigeration or heat pump cycles. In this paper, performances of 9 currently investigated NH₃/ILs pairs are calculated and compared in terms of their applications in the single-effect absorption heat pumps (AHPs) for the floor heating of buildings. Among them, 4 pairs were reported for the first time in absorption cycles (including one which cannot operate for this specific heat pump application). The highest coefficient of performance (COP) was found for the working pair using [mmim][DMP] (1.79), and pairs with [emim][Tf₂N] (1.74), [emim][SCN] (1.73) and [bmim][BF₄] (1.70) also had better performances than that of the NH₃/H₂O pair (1.61). Furthermore, an optimization was conducted to investigate the performance of an ideal NH₃/IL pair. The COP of the optimized mixture could reach 1.84. Discussions on the contributions of the generator heat and optimization results revealed some factors that could affect the performance. It could be concluded that the ideal IL candidates should show high absorption capabilities, large solubility difference between inlet and outlet of the generator, low molecular weights and low heat capacities. In addition, an economic analysis of the AHP using NH₃/[emim][SCN] working pair with plate heat exchangers was carried out based on heat transfer calculations. The results indicated that the NH₃/IL AHP is economically feasible. The efforts of heat transfer optimization in the solution heat exchanger and a low expense of ILs can help the IL-based AHP systems to become more promising.

Monte Carlo (MC) simulations in ensembles with a fixed chemical potential or fugacity, for example the grand-canonical or the osmotic ensemble, are often used to compute phase equilibria. Chemical potentials can be computed either with an equation of state (EoS) or from molecular simulations. The accuracy of the computed chemical potentials depends on the quality of the (critical) parameters used in the EoS and the applied force field in the simulations. We investigated the consistency of both approaches for computing fugacities of the industrially relevant gases CO₂, CH₄, CO, H₂, N₂, and H₂S. The critical temperature (T_c), pressure (P_c), and acentric factors (ω) of these gases are computed from MC simulations in the Gibbs ensemble. The effect of cutoff radius and tail corrections on the computed values of T_c, P_c, and ω is investigated. In addition, MC simulations in the Gibbs ensemble are used to compute the VLE of the 15 possible binary systems comprising the gases CO₂, CH₄, CO, H₂, N₂, and H₂S, and the ternary systems CO₂/CH₄/H₂S and CO₂/CO/H₂. Binary interaction parameters (k_ij) of these natural/synthesis gas mixtures are obtained by fitting the Peng-Robinson (PR) EoS to the binary VLE data from the MC simulations. The computed properties from the MC simulations are compared with the PR EoS, the GERG EoS, and experimental results. The MC results show that including tail corrections in the simulations is crucial to obtain accurate critical properties. The force fields used for the gases can reproduce the fugacities of the gases within 5% of the experimental data. The dew-point curves of all the 15 binaries were predicted correctly by the MC simulations, but the bubble-point curves for the systems H₂/CO, CH₄/H₂, H₂S/N₂, and H₂S/CO significantly deviate from the experiments.