Auto Cascade Research Articles

Isothermal measurement and modeling of VLE properties for 2,3,3,3-tetrafluoroprop-1-ene + trifluoromethane + tetrafluoromethane ternary system at temperatures from 253.15 K to 273.15 K

Abstract At present, the difficulty in the research of auto cascade refrigeration system lies in the selection of the mixed refrigerant ratio and the design of system process. Accurate thermodynamic data is the key to solve those problems. In this paper, isothermal vapor liquid equilibrium (VLE) behavior was experimentally studied for the strongly-zeotropic ternary mixture 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) + trifluoromethane (R23) + tetrafluoromethane (R14) at 253.15 K, 263.15 K, and 273.15 K. The pressures and the vapor mass fractions were found to be thermodynamically consistent and were satisfactorily correlated with the NRTL-RK model and the MUNIFAC-SRK model. The average absolute relative deviations of pressure (AARD-p), and the average absolute deviations of vapor phase mass fraction (AAD-y1, AAD-y2 and AAD-y3) are less than 0.25%, 0.0032, 0.0048 and 0.0040 for the MUNIFAC-SRK model, respectively, which are better than those of 0.4%, 0.0138, 0.0198 and 0.0049 for the NRTL-RK model. The results of the MUNIFAC-SRK model showed excellent agreement with the experimental values. The isothermal three-dimensional VLE behavior and the isothermal-isobaric ternary VLE diagrams under 1500 kPa were also established using a flash calculation method.

SECOND LAW ANALYSIS OF AUTO CASCADE REFRIGERATION CYCLE USING MIXED HYDROCARBON REFRIGERANT R-600A /R-290/ R170

Experimental and theoretical analysis investigations are achieved on the performance of the three-stage auto cascade refrigeration system. Energy and exergy analysis of auto cascade system is considered using zeotropic mixed hydrocarbon refrigerant R-600a/R-290/R-170 at different mass fractions of (25.5/42.5/32), (24.25/42.75/33), (23/43/34) and (20.5/43.5/36) %. The experimental work was performed on test rig for three stages auto cascade refrigeration system of one ton capacity which is designed and constructed for the present study. The theoretical analysis was carried out using a simulation software PROII based on EES and REFPROP software. The investigated results of the mixed refrigerant R600a/R-290/R170 have showed an enhancement in COP and cycle capacity by about 12.39% and 15% respectively, and the evaporator temperature of the system has approached a relatively lower value of -60.3°Cat mass fraction (23/43/34) compared to the average value of the other mass ratios. The higher values of the exergy efficiency observed for the condenser, evaporator and compressor were 0.92, 0.87 and 0.7 respectively. Comparison of the auto-cascade performance with R-600a/R-290/R-170 at mass fraction (23/43/34) has displayed an enhancement around 45.3 % in the cycle capacity and 39% reduction in the evaporator temperature compared to the mixed refrigerant R-134a/R-410A at mass fraction (70/30). The theoretical results have displayed a reasonable agreement compared to the experimental results with deviations 33%, 22%, and 18% in COP, cycle capacity and overall exergy efficiency respectively.

Investigation on vapor liquid equilibrium for strongly-zeotropic ternary mixture of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) + trifluoromethane (R23) + tetrafluoromethane (R14)

The cubic equation of state/excess Gibbs free energy (CEoS/GE) model is a new idea to predict non-ideal systems. In this study, the Peng-Robinson (PR) EoS combined with the Wong-Sandler (WS) mixing rule and the modified UNIFAC group contribution activity model was used to calculate the vapor liquid equilibrium (VLE) data. The average absolute relative deviations (AARD) of pressure and the average absolute deviations (AAD) of the vapor phase mass fraction between the calculated results and experimental data are 0.87% and 0.005 for fluoroethane (R161)+2,3,3,3-tetrafluoroprop-1-ene (R1234yf) over the temperature range of (283.15–323.15K) and at pressures varying from 0.4MPa to 1.8MPa, respectively. The liquid and vapor phase mass fraction deviations are within ±0.028 and ±0.025 for difluoromethane (R32)+pentafluoroethane (R125)+1,1,1,2-tetrafluoroethane (R134a) system at temperatures of (205–350K), respectively. The VLE behavior for the strongly-zeotropic mixture of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf)+trifluoromethane (R23)+tetrafluoromethane (R14) which is suitable for the three-stage auto cascade refrigeration system was calculated at pressures of (0.2–2.2MPa) and the corresponding three-dimensional phase diagrams were constructed. It was found that the sliding temperature increases with the decrease of pressure and the maximum predicted sliding temperature reached 73K.

Solar-assisted auto-cascade heat pump cycle with zeotropic mixture R32/R290 for small water heaters

In this study, a novel solar-assisted auto-cascade heat pump cycle (SAHPC) operating with the zeotropic mixture of R32/R290 for small water heaters is proposed. In the SAHPC system, a cascade heat exchanger (CHEX) associated with a phase separator is used to achieve auto cascade cycle and enhance the overall system performance. The performances of the SAHPC are evaluated by using the developed mathematical model, and then compared with the conventional air-sourced heat pump cycle (CAHPC). Simulation results show the SAHPC has 4.23–9.85% and 4.37–9.68% improvements in COP and volumetric heating capacity compared with those of the CAHPC, respectively, under the same operating conditions. However, the improvement of performance of this novel cycle largely depends on the absorbing heat ratio and the zeotropic composition. It is expected that this new cycle will be beneficial to developing dual-source coupled heat pump applications.

Mixed refrigerant composition shift due to throttle valves opening in auto cascade refrigeration system

Auto cascade refrigeration (ACR) cycle with phase separators is widely used in the cryogenic system. The composition of mixed refrigerant has a great effect on the performance of the system. Based on the assumption of infinite volume of phase separator, ACR system with one phase separator is simulated in this paper. The variation of refrigerant composition under different valves opening is obtained. A related experimental system is set up to verify the variation. The result shows that when the valve opening connected to the evaporator increases or the valve opening under the phase separator decreases, the low-boiling component concentration of the working mixture passing through the compressor and condenser increases, while the high-boiling component concentration decreases. Furthermore, the variations of condensation pressure and evaporation pressure under different valves opening are also observed. This paper is helpful to deepen the understanding of ACR system.

Research on the Auto Cascade Refrigerating Cycle System

An auto cascade refrigerating cycle system was built up in the laboratory. By changing the parameters of the operation process, the law of the operation and the effect on performance of the system were studied. When the extrinsic parameters changed, the performances of the system were measured. The paper analyzed that the evaporation temperature and the temperature of the inlet of the cooling water affect on the efficiency of the system and the pressure rate. The result shows that when the temperature of the cooling water is given, the COP of the system goes down with the decrease of the evaporation temperature. And when the evaporation temperature is given, the COP of system goes down with the increase of the condensate temperature. The pressure rate increases when the temperature of the cooling water gets higher. When both the evaporation temperature and the temperature of the cooling water are given, the COP of a R22/R23 system is higher than that of an R134a/R23 system.

Study on Energy Efficiency of a Low Temperature Refrigeration System

Based on conservation of mass, total mass balance equation and component mass balance equation, mathematical models of thermodynamic for the auto cascade refrigeration cycle are established. Thermophysical properties in solving the governing equation are called from the NIST REFPROP7.0. Thermodynamic properties of the auto cascade refrigeration cycle using binary mixtures, namely, R170/R290, R23/R227ea, R116/R134a, R23/R134a, R170/R600a, R170/R600 and R170/R152a as refrigerants is evaluated. R170/R600a is selected for the low temperature refrigeration system, and the influences of cycle mole fraction, compression ratio and evaporating pressure on the cycle performance are analysed.

00/03641 Thermodynamic analysis of binary and ternary silicate systems by a structural model

The cubic equation of state/excess Gibbs free energy (CEoS/GE) model is a new idea to predict non-ideal systems. In this study, the Peng-Robinson (PR) EoS combined with the Wong-Sandler (WS) mixing rule and the modified UNIFAC group contribution activity model was used to calculate the vapor liquid equilibrium (VLE) data. The average absolute relative deviations (AARD) of pressure and the average absolute deviations (AAD) of the vapor phase mass fraction between the calculated results and experimental data are 0.87% and 0.005 for fluoroethane (R161) + 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) over the temperature range of (283.15–323.15 K) and at pressures varying from 0.4 MPa to 1.8 MPa, respectively. The liquid and vapor phase mass fraction deviations are within ±0.028 and ±0.025 for difluoromethane (R32) + pentafluoroethane (R125) + 1,1,1,2-tetrafluoroethane (R134a) system at temperatures of (205–350 K), respectively. The VLE behavior for the strongly-zeotropic mixture of 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) + trifluoromethane (R23) + tetrafluoromethane (R14) which is suitable for the three-stage auto cascade refrigeration system was calculated at pressures of (0.2–2.2 MPa) and the corresponding three-dimensional phase diagrams were constructed. It was found that the sliding temperature increases with the decrease of pressure and the maximum predicted sliding temperature reached 73 K.