A new CO2 refrigeration system with two-phase ejector and parallel compression for supermarkets.

This study explores the integration of parallel compression and a two-phase ejector in transcritical CO2 refrigeration systems, aiming to improve efficiency and performance. This innovative approach bridges the gap between conventional approaches and explores new energy-saving potential. The study uses thermodynamic modeling, mathematical simulation, and in-depth analysis to look at energy and exergy performance in a new configuration for applications in the retail sector at medium evaporation temperatures. The work investigates thermodynamic phenomena in a novel cycle with steady-state conditions, low pressure differentials, and adiabatic efficiency. The model is validated against experimental and theoretical published data, revealing component-specific exergy destruction and key parameters. The novel cycle efficiently extracts heat at higher temperatures, outperforming conventional and parallel cycles. Exergetic efficiency surpasses the standard cycle, with gas cooler pressure and temperature dependence enhancing efficiency by 40%-45%. The distribution of exergy destruction percentages reveals efficiency determinants, emphasizing heat exchange optimization and ejector responsiveness in energy dissipation dynamics. The study investigates the coefficient of performance (COP) dependence on gas cooler pressure and temperature, revealing superior performance compared to conventional cycles. COP increases by 50% at 80 bars, indicating enhanced efficiency. The new cycle offers exceptional efficiency gains, with a COP enhancement of over 75% for evaporator temperature transitions. Comparative analysis shows a COP superiority of up to 53% for lower evaporator temperatures and 20% for higher evaporator temperatures, demonstrating substantial energy savings and improved performance across various operating conditions.

Exergy and Exergoeconomic Analysis of a Cogeneration Hybrid Solar Organic Rankine Cycle with Ejector.

Solar energy is utilized in a combined ejector refrigeration system with an organic Rankine cycle (ORC) to produce a cooling effect and generate electrical power. This study aims at increasing the utilized share of the collected solar thermal energy by inserting an ORC into the system. As the ejector refrigeration cycle reaches its maximum coefficient of performance (COP), the ORC starts working and generating electrical power. This electricity is used to run the circulating pumps and the control system, which makes the system autonomous. For the ejector refrigeration system, R134a refrigerant is selected as the working fluid for its performance characteristics and environmentally friendly nature. The COP of 0.53 was obtained for the ejector refrigeration cycle. The combined cycle of the solar ejector refrigeration and ORC is modeled in EBSILON Professional. Different parameters like generator temperature and pressure, condenser temperature and pressure, and entrainment ratio are studied, and the effect of these parameters on the cycle COP is investigated. Exergy, economic, and exergoeconomic analyses of the hybrid system are carried out to identify the thermodynamic and cost inefficiencies present in various components of the system.

Simulations of Magnetohemodynamics in Stenosed Arteries in Diabetic or Anemic Models.

Pulsatile flow simulations of non-Newtonian blood flow in an axisymmetric multistenosed artery, subjected to a static magnetic field, are performed using FLUENT. The influence of artery size and magnetic field intensity on transient wall shear stress, mean shear stress, and pressure drop is investigated. Three different types of blood, namely, healthy, diabetic, and anemic are considered. It is found that using Newtonian viscosity model of blood in contrast to Carreau model underestimates the pressure drop and wall shear stress by nearly 34% and 40%, respectively. In addition, it is found that using a magnetic field increases the pressure drop by 15%. Generally, doubling the artery diameter reduces the wall shear stress approximately by 1.6 times. Also increasing the stenosis level from moderate to severe results in reduction of the shear stress by 1.6 times. Furthermore, doubling the diameter of moderately stenosed artery results in nearly 3-fold decrease in pressure drop. It is also found that diabetic blood results in higher shear stress and greater pressure drop in comparison to healthy blood, whereas anemic blood has a decreasing effect on both wall shear stress and pressure drop in comparison to healthy blood.

Computational modeling of non-Newtonian blood flow through stenosed arteries in the presence of magnetic field.

Steady flow simulations of blood flow in an axisymmetric stenosed artery, subjected to a static magnetic field, are performed to investigate the influence of artery size, magnetic field strength, and non-Newtonian behavior on artery wall shear stress and pressure drop in the stenosed section. It is found that wall shear stress and pressure drop increase by decreasing artery size, assuming non-Newtonian fluid, and increasing magnetic field strength. In the computations, the shear thinning behavior of blood is accounted for by the Carreau-Yasuda model. Computational results are compared and found to be inline with available experimental data.