A comprehensive model of a novel rotating spool compressor

A comprehensive simulation model of a novel rotating spool compressor is presented. The spool compressor provides a new rotary compression mechanism with easily manufactured components. A detailed analytical geometry model of the spool compressor is presented, which includes the geometry of the vane. This geometry model is included in an overall comprehensive compressor model that includes sub-models for friction, leakage, and heat transfer. The results of the comprehensive model were validated using experimental data from a prototype compressor. The prototype compressor has an overall displacement of 23.9 cm³, and was operated using R410A as the working fluid. The model predicts the volumetric efficiency, discharge temperature, and shaft power of the prototype compressor to within 3.13% MAE, 16.5 K and ?13.2 W average deviation, respectively. The trends and spread in the data indicate that additional effort should be focused on the operation of the active sealing elements within the compressor.     

A lumped-parameter thermal model for scroll compressors including the solution for the temperature distribution along the scroll wraps

A lumped-parameter thermal model is presented to predict the temperature in different chambers and components inside scroll compressors with particular attention to gas superheating in the suction process. Thermal resistances between the components are based on global heat transfer conductances, whereas conduction heat transfer through the scroll wraps is solved via a one-dimensional finite volume method. The thermal model was coupled to a thermodynamic model of the compression cycle and then applied to simulate the compressor performance under different conditions of speed and pressure ratio. The model was able to correctly predict the compressor temperature for operating conditions within the range of those adopted for its calibration. The results showed a strong coupling between the compressor thermal profile and the temperatures of the motor and lubricating oil. It has also been found that heat conduction through the scroll wraps reduces slightly the discharge temperature.     

Modeling of a novel spool compressor with multiple vapor refrigerant injection ports

A model of a novel rotary spool compressor has been developed to explore the effect of multiple injection ports on compressor and cycle performance. The thermodynamic model includes the effects of heat transfer and leakage and is numerically solved to predict the compressor power consumption and mass flow rate. Saturated vapor injection is modeled assuming that the injection pressures and the timing of the injection process can be controlled.The model predicts that adding a single injection port will provide a 12% increase in the cycle coefficient of performance (COP) when the compressor runs at 1907 rpm with R-22 evaporating at ?7 °C, condensing at 49 °C, and 15 °C of superheat. Adding a second, non-optimized injection port increases the COP by 16% compared to the cycle without injection. The model is used to investigate the effect of injection pressure, port location, and port diameter on cycle performance.     

Variable wall thickness scroll geometry modeling with use of a control volume approach

In a scroll-type compressor, compression is achieved through relative contact between two spiral curves. Since the scroll invention by Leon Creux (1905), multiple methods have been developed for calculating scroll geometry. What can generally be considered the most classical method, is defining each scroll curve as the involute of a circle. Gravesen and Henriksen (2001) introduced a new method to calculate scroll geometry by deriving each scroll curve from the radius of curvature parameterized with involute angle. This allows a wide range of involute geometries to be considered not included in the classical method. In this paper, Gravesen's method is extended to the tip region to include all tip geometries involved in a two arc configuration resulting in a more comprehensive scroll geometry definition. Lastly, with parametric representation of all scroll geometry, the pocket volume can be easily solved using a derived control volume approach.     

Modeling and experimental evaluation of an automotive air conditioning system with a variable capacity compressor

A steady state computer simulation model has been developed for refrigeration circuits of automobile air conditioning systems. The simulation model includes a variable capacity compressor and a thermostatic expansion valve in addition to the evaporator and micro channel parallel flow condenser. An experimental bench made up of original components from the air conditioning system of a compact passenger vehicle has been developed in order to check results from the model. The refrigeration circuit was equipped with a variable capacity compressor run by an electric motor controlled by a frequency converter. Effects on system performance of such operational parameters as compressor speed, return air in the evaporator and condensing air temperatures have been experimentally evaluated and simulated by means of developed model. Model results deviate from the experimentally obtained within a 20% range though most of them are within a 10% range. Effects of the refrigerant inventory have also been experimentally evaluated with results showing no effects on system performance over a wide range of refrigerant charges.     

Dynamic analyses for the rotor-journal bearing system of a variable speed rotary compressor

In the rotary compressor, the rolling piston and the contacted rotor-journal bearing system are main moving components. They suffer very large periodically varying loads introduced by the inertia force, the contact force and the gas force. These loads change rapidly with speed variation of the compressor. They always lead to serious vibration of the system, and then result in abrasion and performance reduction. In this paper, the dynamic behavior of the rotor-journal bearing system were calculated by solving three-dimensional numerical model using finite element method, and the vibration characteristics of the system were investigated according to the calculation results. The natural frequencies and vibration modes were obtained. The stress, displacement and axis orbit of the rotor center were calculated considering the speed variation of the motor. Via the established numerical model, vibration characteristics of a newly designed compressor can be predicted, and optimization can be done to reduce the vibration.     

Optimization of an oil charge amount on electric driven scroll compressor for eco-friendly vehicle

The purpose of this study is to optimize the amount of oil charge in the electric driven scroll compressor for eco-friendly vehicles. R134a is used as the refrigerant in the vehicle and Polyolester (POE) oil as the compressor oil. The initial amount of oil was increased at 20 g intervals from 40 g to 120 g, and at each initial amount of oil charge, the back pressure is measured at each step of the complex durability test and under each condition of the performance test. Throughout the test, it is found out that the optimum amount of oil is determined by the back pressure, which is 80 g in this test. The performance of a system is compared with pull-down tests in the actual air conditioning system, and the optimum amount of oil was confirmed. A complex durability test was also evaluated and verified for the durability of the compressor with the confirmed amount of oil.     

The applicability of an existing fluted tube condenser model when used with refrigerant R-407C

Fluted tube-in-tube condensers are key components in energy efficient water heating heat pumps. Rousseau et al. (2003) developed a model that incorporates all the essential features of these heat exchangers. A feature of the model was that it allowed for the extension to simulate heat exchangers for cycles employing zeotropic refrigerant mixtures. This paper investigates the applicability of the model for R-407C condensation inside fluted tube annuli. To evaluate the model experimental data was gathered using a test facility. Comparisons between the experimental results and the model showed an average model accuracy of 48% when predicting the pressure drop and 56% for the log mean temperature difference (LMTD) for the tubes sizes used. Based on these accuracies new enhancement factors were derived and implemented in the model. This resulted in an average difference between the simulated and measured pressure drops of 9.5% and an average difference for the LMTD of 3.3%.     

Research of leakage characteristics of single screw refrigeration compressors with the Multicolumn Envelope Meshing Pair

The Multicolumn Envelope Meshing Pair (MEMP) was proposed and has been applied for the single screw refrigeration compressor (SSRC) to reduce the wear of the meshing pair. However, the geometric model shows its changed shape of the leakage paths compared with the existing straight line envelope meshing pair (LEMP). It is necessary to research the leakage characteristics of the SSRC with MEMP and LEMP, to evaluate the value of the proposed MEMP. In this paper, the geometric model of the leakage paths between star-wheel and screw rotor is established. A two-phase leakage mathematical model for gas-oil flow is presented to predict the gas leakage rate of the SSRC with MEMP. The experiments of the performance of a SSRC with MEMP were conducted to verify the leakage mathematical model. Obtained results show the leakage of the SSRC with MEMP is a little bit smaller than that of the SSRC with LEMP.     

Ejector in R410A vapor compression systems with experimental quantification of two major mechanisms of performance improvement: Work recovery and liquid feeding

This paper presents experimental data and analysis comparing the performance of an R410A ejector vapor compression system to those of a liquid-fed evaporator system and a conventional expansion valve system. The objective was to quantify separately two major improvements of the ejector system: work recovery and liquid-fed evaporator. The ejector system was first compared to a system with liquid-fed evaporator at matching cooling capacities and revealed improvements from 1.9% to 8.4% solely due to the work recovery of the ejector. When compared to a conventional expansion valve system at the same cooling capacity, the ejector setup improved COP from 8.2% to 14.8% due to simultaneous benefits of liquid-fed evaporator and work recovery. Overall ejector efficiencies from 12.2% to 19.2% were achieved.