In this study, a basic organic Rankine cycle (ORC) is introduced in an air separation process for waste heat recovery. Conventional and advanced exergy analyses are adopted to investigate the thermodynamic properties of components in the ORC. A comprehensive thermodynamic model is constructed to improve the advanced exergy analysis in the ORC, thereby encompassing real, theoretical, unavoidable, and hybrid cycles. Nine organic working fluids are introduced to investigate the influence on the ORC performance. ( 1) The conventional exergy analysis reveals the following: (a) The expander constantly demonstrates the maximum exergy efficiency except when R227ea is used. (b) The evaporator constantly exhibits the maximum exergy destruction regardless of the working fluid used. (c) The maximum product exergy is obtained when R114 is used. (d) Key components must focus on the condenser and evaporator to improve the ORC performance.(2) The advanced exergy analysis reveals that the expander demonstrates maximum potential for improvement because its endogenous avoidable exergy destruction accounts for approximately 90% of its real exergy destruction for all working fluids. The expander must be improved to achieve the optimal ORC performance. The advanced exergy analysis can distinguish the source of exergy destruction and the magnitude for possible improvement via the proposed thermodynamic model in this study. The comprehensive thermodynamic model can promote the investigation of the advanced exergy analysis in the ORC.Applying conventional and advanced exergy analyses to investigate the thermodynamic performance of a system or its components is highly recommended.

Indoor air conditioning systems play a crucial role in regulating the environmental conditions of enclosed spaces. The noise generated by such systems can significantly impact human comfort. The multiblade centrifugal fan, as a crucial component of indoor air conditioners, has a significant impact on the performance of the air conditioner. The vortex, which is the primary noise source inside the fan, hinders the aerodynamic noise reduction of the indoor unit. During experimental research and numerical simulation of the indoor unit, the researchers identified the presence of a vortex flow at the outlet of the multiblade centrifugal fan. By analyzing the velocity vector of different cross‐sections in the fan, the researchers determined the formation mechanism and influencing factors of the vortex at the fan's outlet. The addition of fairing sheet plates on the volute wall was explored as a vortex suppression method, which proved effective in weakening and suppressing the vortex. The test results showed that under the same air volume, the noise reduction amplitude of the fan equipped with fairing sheet blades was 1.2 dB at an outlet static pressure of 30 Pa and 0.7 dB at an outlet static pressure of 100 Pa. The research findings suggest that the addition of the fairing sheet can effectively reduce the vortex's intensity, improve the performance of the multiblade centrifugal fan, and reduce the noise.

To improve the stable operating range of centrifugal compressor stage, endwall contouring technology is introduced on the hub-side wall of the vaned diffuser for NASA CC3 centrifugal compressor as a promising technique to redistribute the flow field near the endwall in this paper. The main contents of this paper are listed as follows. First, a specific parameterized endwall contouring guideline is developed based on sinusoidal function and Bézier curve, and three factors are considered, namely, peak height, peak radial position, and frequency coefficient. Then, centrifugal compressor stages with baseline diffuser and contoured endwall diffusers are numerically investigated to reveal the influence of endwall contouring on the stable operating range. Results show that endwall contouring is an effective method to achieve stability enhancement with no evident reduction in stage performance on the design point. CEW13-12 has the most successful combination of endwall contouring parameters, and stall margin is increased by up to 40% for CEW13-12. Finally, the influence mechanism of endwall contouring on the stable operating range is discussed. At the near stall condition, the contouring endwall forces the fluid within the semi vaneless space to deflect toward the suction side to increase the momentum of low-energy fluid in the suction surface boundary layer and reduce the adverse pressure gradient on the suction side, which delay the development of flow separation on the vane leading edge near the shroud side to suppress the onset of rotating stall. At the near choke condition, the contouring endwall has more potential to increase the throat area, resulting in a decrease of throat blockage to improve choke margin. The results show that the endwall contouring technology is a reliable method to achieve stability enhancement of centrifugal compressor stage.

For studying the influence of impingement plates on the fluid flow within the shell-side of the shell-and-tube heat exchanger, two-dimensional numerical simulation is carried out using the Fluent software. The different distances between the impingement plate and the tube bundle are taken into consideration. Meanwhile the research investigates the flow field of the non-perforated impingement plate and the perforated impingement plates with various hole diameters. The results show that the fluid behind the non-perforated impingement plate contacts the tube insufficiently. The farther the distance between the non-perforated impingement plate and the tube bundle is, the more tubes contact with the fluid poorly. The flow field behind the perforated impingement plates is more uniform. The protective effect from flow impacting for impingement plates is positive. The perforated impingement plates are recommended in the engineering design of the shell-and-tube heat exchanger.

All-over-controlled vortex method is an effective tool to inversely design the 3D impeller of a centrifugal compressor. In this method, swirl distribution is treated as a significant input parameter to control the blade shape, impeller flow field, and compressor performance. It is acknowledged that swirl distribution is prescribed by designers mostly relying on the personal experience at the beginning of design. So how to specify the swirl distribution is still a big challenge for impeller designers. Of the most interest in this paper is to provide a theoretical technique that can be readily applied to specify swirl distribution and reduce the dependence on the designers experience. A judgement criterion rCθ – ωr2 is proposed to design the swirl distribution. Based on the streamline curvature method, a 3D centrifugal impeller design program is developed to design centrifugal impeller. The scale and uniformity of rCθ – ωr2 along flow direction are discussed theoretically to conduct the specifying of swirl distribution. The theoretical analysis is verified by a specific centrifugal compressor case. Then commercial CFD software is used to predict the flow field and the performance of the impeller. The results demonstrate that the scale and distribution uniformity of rCθ – ωr2 have a significant effect on the blade shape and the flow field within the impeller, and possible loss can be reduced. For the new designer, it is possible to preliminarily recognize and eliminate the infeasible swirl distribution, and adjust the unsatisfactory swirl distribution using rCθ – ωr2. Proper blade shape and good impeller performance can be achieved with the help of the judgement criterion rCθ – ωr2.