Qubo Li

Multi Stage Variable Speed Turbo Compressor for Enhancing Seasonal Energy Efficiency Ratio of Air Conditioners Using R718 as Refrigerant

An air conditioning system using water as refrigerant (R718) that compresses water vapor with multistage stage variable speed axial compressor with intercooling between stages by water injection is considered. Four stage compression with flash intercooling resulted in 50% improvement of coefficient of performance (COP) at full load compared to conventional refrigerants like R134a. The energy-efficiency of an air conditioning unit is specified by seasonal energy efficiency ratio (SEER). SEER is defined as the ratio of cooling output of an air conditioner measured and electrical energy consumption as per AHRI 210/240 during cooling season. The SEER is computed after determining the evaporator cooling capacity and the electrical energy demand of the compressor at each bin temperature using assumed compressor isentropic efficiency, mechanical efficiency and electrical efficiency and multiplying by the weight of each bin temperature to determine the total for the cooling season. As a result of multistage compression, best part load performance of water as a refrigerant and operation of compressor near design point at part load due to variable speed drive, 50–60% improvement in SEER is obtained compared to the best available in the market using conventional refrigerants such as R134a with single stage compression.Copyright

MECHANICAL AND OPTIMIZATION ANALYSES FOR NOVEL WOUND COMPOSITE AXIAL IMPELLER

A mechanical and optimal analyses procedure is developed to assess the stresses and deformations of Novel Wound Composite Axial-Impeller under loading conditions particular to centrifuge. This procedure is based on an analytical method and Finite Element Analysis (FEA, commercial software ANSYS) results. A low-cost, light-weight, high-performance, composite turbomachinery impeller from differently designed patterns will be evaluated. Such impellers can economically enable refrigeration plants using water as a refrigerant (R718). To create different complex patterns of impellers, MATLAB is used for creating the geometry of impellers, and CAD software UG is used to build three-dimensional impeller models. Available loading conditions are: radial body force due to high speed rotation about the cylindrical axis and fluid forces on each blade. Two-dimensional plane stress and three-dimensional stress finite element analysis are carried out using ANSYS to validate these analytical mechanical equations. The von Mises stress is investigated, and maximum stress and Tsai-Wu failure criteria are applied for composite material failure, and they generally show good agreement.Copyright

USING WATER VAPOR AS REFRIGERANT IN MULTISTAGE VARIABLE SPEED TURBO COMPRESSOR TO IMPROVE SEASONAL ENERGY EFFICIENCY RATIO OF AIR CONDITIONING

An air conditioning system using water as refrigerant (R718) that compresses water vapor with multistage stage variable speed axial compressor with intercooling between stages by water injection is considered. Four stage compression with flash intercooling resulted in 50% improvement of coefficient of performance (COP) at full load compared to conventional refrigerants like R134a. The energy efficiency of an air conditioning unit is specified by seasonal energy efficiency ratio (SEER). SEER is defined as the ratio of cooling output of an air conditioner measured and electrical energy consumption as per AHRI 210/240 during cooling season. The SEER is computed after determining the evaporator cooling capacity and the electrical energy demand of the compressor at each bin temperature using assumed compressor isentropic efficiency, mechanical efficiency and electrical efficiency and multiplying by the weight of each bin temperature to determine the total for the cooling season. As a result of multistage compression, best part load performance of water as a refrigerant and operation of compressor near design point at part load due to variable speed drive, 50%–60% improvement in SEER is obtained compared to the best available in the market using conventional refrigerants such as R134a with single stage compression.

Static, Dynamic and Failure Behavior of a Novel Axial Composite Impeller for Water Chiller

Centrifugal forces applied to an impeller due to spinning generate large stresses. Aerodynamic forces are also imparted on the blade varying with time. These two forces play different roles during compressor events. Damage accumulated from these events results in the fatigue failure of impeller material and structure. Therefore, it is important to design the impeller against fatigue failure. The finite element method has been used in the study of impeller fracture mechanics and is regarded as an important tool in the design and analysis of impeller structures. A novel axial composite impeller manufactured through filament winding technology was invented by Michigan State University to compress water vapor as refrigerant. In this study dynamic and fatigue behavior of this composite impeller were analyzed using commercial code ANSYS. To begin with, load cases were identified, calculated and evaluated. Static analysis was performed using a full 3-D finite element model and the critical zone where fatigue failure begins was extracted to determine life assessment positions. Secondly, aerodynamic forces imparted on the blade were obtained from FLUENT; so that damage from dynamic stresses could be calculated. Finally, based on the FEM and FLUENT simulation results, a linear damage accumulation model was employed as a damage estimation rule to predict life of the composite impeller. A conservative life of 6498 h is given by this method.Copyright