In this study, a vibrating nozzle using the waste vibration energy of the compressor body was installed in the suction flow path to improve the efficiency of the compressor through the pre-compression. To this end, the behavior of the suction valve according to the vibrating nozzle and the mass flow rate of the refrigerant entering the compression chamber were numerically analyzed. The results showed that the mass flow rate increased proportionally as the angle of the vibration nozzle increased. Among the profile shapes of the vibration nozzle, the concave or straight shape showed the highest mass flow rate. Considering the ease of machining, the straight shape is more favorable. On the other hand, as the operating frequency and stroke of the vibration nozzle increased, the mass flow rate also increased proportionally. It can be seen that the largest nozzle angle, operating frequency, and stroke are favorable for pre-compression unless the suction flow is restricted.. In the future, it is necessary to apply the vibrating nozzle system to an actual compressor model to experimentally check the compressor's cooling power, compression work and EER.
Abstract The compressor of a refrigerator accounts for approximately 60-80% of the total energy consumption necessary for the refrigeration cycle. This study investigates the implementation of a pre-compression system featuring a vibrating nozzle, with the goal of enhancing the efficiency of a linear compressor. By utilizing this pre-compression system, the cooling capacity and efficiency of the compressor are expected to improve. The numerical results show that the pre-compression system leads to an improvement of approximately 1.7% in cooling capacity compared to the baseline model. Furthermore, an increase of approximately 0.1 in EER was observed, confirming the feasibility of incorporating a pre-compression system with a vibrating nozzle.
The new thermal management models of linear compressors have been recently reported. These models adopt the simplified transient flow effects to shorten the excessive analysis time. Among the unsteady flow effects of the linear compressor, the effect of the gap flow between the compressor housing and the body due to the body vibration on the heat transfer performance was studied in this paper. For this study, a numerical analysis for the unsteady axisymmetric flows was performed by using CFD (Computational Fluid Dynamics). The results show that the high-speed refrigerant flows occurred in the gap between the compressor housing and the body, which contribute to increasing the heat transfer from high temperature refrigerants in the housing to the outside air. In addition, as the gap decreases, the refrigerant flow rate through the gap increases and the heat transfer rate increases as well.
Refrigerators used in homes occupy a large portion of the power consumption. In addition, most of the power consumption of the refrigerator is used by the compressor. Therefore, it is necessary to study on the improvement of compressor efficiency to save energy. In this study, the suction system was changed to improve the efficiency of the linear compressor. For this, numerical analysis was performed by linking the 1 dimensional lumped model and the 2 dimensional axisymmetric CFD model. The numerical analysis results were also compared with the experimental results. As a result of the numerical analysis, the model with modified suction system increased EER by about 0.25% compared to the basic model, which was also confirmed by experiment.
Energy saving in household refrigerators becomes more important as the usage of household refrigerators have been increasing every year. Since a compressor in the refrigerator consumes more than 80% of its total energy, it is necessary to reduce the energy consumption of the compressor. In this paper, the convective heat transfer coefficients on the compressor housing for both natural convection and forced convection were measured. Then, the effect of convective heat transfer coefficient on the power consumption of a refrigerator was investigated using a thermal management analysis. The results showed that convective heat transfer coefficient for forced convection is higher by 7.8 W/m²K compared to the natural convection. In addition, through the thermal management analysis, it was found that the increase in convective heat transfer coefficient reduces the refrigerator power by about 4.8% improving EER by 0.9%.
The refrigerant temperature of a compressor increases due to heat generated in the discharge chamber and the motor. The increase of the suction temperature raises the superheat resulting in EER reduction. Thus, accurate superheat prediction is needed for the design of an efficient compressor. In this paper, the unsteady flow analysis is performed using CFD to predict the superheat. The results show that the suction temperature increases by about 26 °C which agrees well with the experiments.
Abstract The increase of the superheat is one of several factors adversely affecting the efficiency of the refrigeration cycle. To this end, it is important to release the heat inside the compressor. Therefore, in this paper, we have increased the convective heat transfer coefficient inside the compressor by utilizing the vibration of the moving part of the compressor. The results show that reducing the gap between the shell and the moving part increases the flow velocity in the gap resulting in the increase of convective heat transfer coefficient.
In recent years, technology has been developed the way the volume of the portable communication device is reduced but its performance is maintained. The COF(Chip On Film) packaging method is used due to the densification of the lead pitch, especially for the display driver IC. During COF packaging, lead break and film detachment could occur by the high bonding temperature and pressure, and possibility for lead interference can emerge by deformation of leads. In this study, a new double-column arrangement of leads is considered to increase lead density further than the existing zigzag arrangement of leads, and nonlinear structural analysis was carried out to examine whether the interference can occur. The results showed that stress and deformation of the corner region appear relatively higher than those of central region, and interference did not occur by the lead strain for the double-column arrangement of leads with pitch of 25μm. Therefore, double-column lead arrangement can improve lead density by about 176% compared to the zigzag lead arrangement
A compressor in the refrigerator uses about 80% of the total consumption power required for refrigerating cycle. In this study, we consider the auxiliary piston equipped with a valve that can be controlled to open and close in order to dramatically increase the efficiency of a linear compressor. Turbocharger using the auxiliary piston was to improve the cooling capacity and efficiency of the compressor. The numerical results show that the cooling capacity was considerably improved by approximately 40.6% compared to that of the baseline model. In addition, COP increased about 7.6% indicating that the turbocharger was very efficient
Abstract The cascade refrigeration cycle system has been used mainly to obtain the ultra-low temperature. In this study, the effects of internal and outdoor temperatures at chamber on the heat capacity of fin-tube heat exchangers were examined. In addition, refrigerant line patterns as well as refrigerant type for cascade cycle were optimized. The results in this study show that the refrigerant line patterns have greater effect on the sensible capacity than the total capacity. Also, the condenser heat release rate for R717-R744 cycle varies the ratio of 46 % with outdoor temperature by comparing with that of 24% for R134a-R410a cycle.