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Elementary Numerical Analysis

This paper presents a detailed model for the compression process of a scroll compressor, which is used for investigating a compressor's performance under different operating conditions and subject to design changes. Upon defining the compressor chambers as suction chambers, compression chambers and discharge chambers, a geometry study was conducted and the governing mass and energy conservation equations were developed for each chamber. Models for the refrigerant flow in the suction and discharge processes, radial and flank leakage, and heat transfer between the gas and scroll wraps were combined with the conservation equations. The state of the refrigerant changes with a period of angle 2π, and thousands of step are used to solve the governing differential equations during each period. It is assumed that in each step the compressor is in steady state. Since the differential equations for the different chambers are coupled, all these equations are solved simultaneously using a nonlinear equation solver. A description of the corresponding computer code and some results are included in this paper. Verification of the compression process model can be referred to that of the overall model, which is described in Chen et al. [Chen Y, Halm N, Braun J, Groll E. Mathematical modeling of scroll compressors—part II: overall scroll compressor modeling. International Journal of Refrigeration 2002;25(6):751–764.].

Mathematical modeling of scroll compressors. Part I: compression process modeling

This paper reviews the major research on refrigerant injection techniques in detail. Liquid and vapor refrigerant injection techniques are discussed and compared. The current research on refrigerant injection techniques falls into two categories: system level research and component level research. The system level research is focused on low ambient temperature heating, heat pump water heating, high ambient temperature cooling, cycle comparison, and control strategy development. Internal heat exchanger and flash tank cycles are the two typical cycles for refrigerant injection. These two cycles are discussed and compared in detail. The component level research is focused on employing different types of compressors, variable speed compressors, the injection process, and the flash tank. Different types of compressors employing refrigerant injection are presented. Based on the literature study, the potential future research directions are presented and discussed. The flash tank cycle control strategy and refrigerant charge management strategy are worth further research efforts. Compressor design can be improved in order to optimize the performance with refrigerant injection. The appropriate design of flash tanks plays a vital role in achieving appropriate two-phase flow patterns in the flash tank. Computational Fluid Dynamics (CFD) modeling can be a useful tool to facilitate the design of the flash tank.

Refrigerant injection for heat pumping/air conditioning systems: Literature review and challenges discussions

Liquid piston gas compression

Advances and challenges in ORC systems modeling for low grade thermal energy recovery

This paper presents the development of a comprehensive simulation model of a horizontal scroll compressor, which combines a detailed compression process model (Chen Y., Halm N., Groll E., Braun J. Mathematical modelling of scroll compressors — part I: compression process modeling, International Journal of Refrigeration 2002;25(6):731–750) and an overall compressor model. In the overall model, compressor components are analyzed in terms of nine different elements. Steady state energy balance equations are established applying the lumped capacitance method. In combination with the detailed compression process model, these equations were implemented into computer code and solved recursively. In this way, the temperature and pressure of the refrigerant in different compressor chambers, the temperature distributions in the scroll wraps, and the temperatures of the other compressor elements can be obtained. Thereafter, power consumption and efficiency of the compressor can be calculated. Tests were used to verify the overall model on a macroscopic basis. Using the simulation program based on the overall compressor model, a parametric study of the scroll compressor was performed, and the effects of internal leakage and heat transfer losses were investigated and some preliminary results were obtained. These results indicate that the comprehensive scroll compressor model is capable of predicting real compressor behavior and useful to the design and optimization of scroll compressors.

Mathematical modeling of scroll compressors — part II: overall scroll compressor modeling

This paper presents a comprehensive model for a hermetic scroll compressor. The model combines models of the compression process including leakage and local heat transfer within the scrolls, frictional losses, motor inefficiencies, and heat transfer within the shell and to the ambient. The model is useful for investigating the impact of design changes on compressor performance. Some sample results are presented in this paper. Detailed validation and an investigation of compressor design improvements are described in a companion paper.

Modeling of Hermetic Scroll Compressors: Model Development

A detailed model for hermetic scroll compressors was presented in a companion paper. The current paper presents validation results for this model based upon detailed experimental measurements and application of the model to study the impact of design changes. The experimental study included a range of operating conditions that were controlled using a hot gas bypass compressor load stand. The model was validated in terms of overall performance predictions (refrigerant mass flow rate, discharge temperature, and compressor power consumption) and predictions of internal measurements (refrigerant pressures within the scrolls as a function of orbiting angle, temperatures along the scroll wraps, and temperatures at various points within the shell). The model performed very well in terms of predicting overall performance and was adequate in predicting the internal measurements. The parametric modeling study identifies some areas for potential improvement. Most significantly, a relative improvement of about 5% in ...

Yu Chen

Papers

Mathematical modeling of scroll compressors. Part I: compression process modeling

Mathematical modeling of scroll compressors — part II: overall scroll compressor modeling

Modeling of Hermetic Scroll Compressors: Model Development

Modeling of Hermetic Scroll Compressors: Model Validation and Application