Performance Analysis of a Twin Rotary Compressor
For a twin rotary compressor, a computer simulation program has been developed. With R22, predicted cooling capacity, compressor input and EER were found to be in good agreement with experimental results. Calculated P-V diagram was also compared well to that of measurement. With the simulation program, parametric study has been performed to investigate effects of cylinder dimensions on R410A twin rotary compressor performance. Over the ranges of cylinder dimensions studied, some variations were found for volumetric, adiabatic and mechanical efficiencies, but overall compressor performance did not change much. Discharge port configuration was found to have large effect on adiabatic efficiency, but not much on volumetric efficiency.
Development of High Efficiency Dual Cylinder Type Rotary Compressor
We conducted numerical and experimental analysis tO improve the efficiency of dual-cylinder rolling piston type rotary compressors by varying cylinder height H, diameter D and eccentricity E by developing a simulator for obtaining the optimum combination of the cylinder dimensions. As a result, the lower ratio of cylinder height to diameter tends toward higher efficiency. The experimental results correspond to the numerical analysis. This investigation includes the reduction of superheat loss during the suction process of a compressor with a thermally isolated cylinder and the acquirement of optimum design conditions for an eccentric bearing. The numerical and experimental results show that a thermally isolated cylinder and an eccentric bearing with optimum design are effective for high efficiency. The results show that the total efficiency of a 3/4 ton prototype dual-cylinder rotary compressor with these effective improvements is higher than that of a conventional single-cylinder type with equivalent capacity. INTRODUCTION In recent years, due to their low noise level and small vibration, scroll compressors are being used more and more. However, rolling piston type rotary compressors are still widely used in small capacity residential air conditioners ( 0.5 to 1.5 KW ) in Japan. The trend of rotary compressors is currently shifting from the conventional single-cylinder type to the dual-cylinder type which has the advantages of a low noise level and small vibration due to its small torque fluctuation. However, the efficiency of a dual-cylinder type is lower than that of a singlecylinder type with equivalent capacity, due to a large leakage loss per unit of displacement. Except for some studies on dynamic analysis [1-2], there are few studies on the improvement of rotary compressor efficiency. This paper presents the contents and effects of improvement for obtaining high efficiency by utilizing numeriCal and experimental analysis. It concludes that the optimization of the cylinder dimensions and the adoption of a thermally isolated cylinder and an eccentric bearing with optimum design are effective for high effic1ency.
Optimum Combination of Dimensions for High Mechanical Efficiency of a Rolling-Piston Rotary Compressor
The suction volume of a rolling-piston type rotary compressor is determined on the basis of the major dimensions, such as the rolling-piston diameter, the cylinder dept h and the cylinder bore. It becomes clear that there are many combinations of majo r dimensions that yield a rolling-piston rotary compressor with the same suction volume . This paper presents the mechanical efficiency for various combinations of major dimen sions and an optimum combination diagram showing which combination ensures th e best mechanical efficiency. In order to examine the physical basis for the optimum combination of major dimensions, the frictional power loss at each pair of compresso r elements is shown. INTRODUCTION The rolling-piston rotary compressor, used in most low capacity air conditioners, eJChibits superior performance in terms of high mechanical efficiency. The primary rea son for this high efficiency is the rolling piston. Fluid lubrication occurs between th e rolling piston and the crank pin, resulting in a substantial decrease in the sliding spee d of the blade relative to the rolling piston (see Refs. (II and (2]). Thus, the rolling pis ton effectively decreases the frictional power losses between the crank pin and the blad e (2, 3]. The frictional power loss at each pair of compressor elements depends mainly upon the corresponding constraint force. The constraint forces depend not only upon th e cylinder pressure and the inertial forces but also upon the major dimensions, such a s 'the rolling-piston diameter, the cylinder depth and the cylinder bore. It is suggeste d here that the suction volume of the rolling-piston rotary compressor is determined b y these major dimensions and, consequently, there are many combinations of majo r dimensions that yield a rolling-piston rotary compressor with the same suction volume . Therefore, the constraint force and the frictional power Joss at each clement pa ir change, depending upon the selected combination of major dimensions, and this result s in different mechanical efficiencies. Thus, selection of the optimum combination o f major dimensions is necessary to ensure a high mechanical efficiency for the rolling piston rotary compressor. The mechanical efficiency was calculated for variou s possible combinations of major dimensions, and it could be shown that there is a n optimum combination of major dimensions. In addition, this paper presents an optimum combination diagram which shows which combination ensures the best mechanica l efficiency. In addition to this diagram, the physical basis for the optimum combinatio n of major dimc;m;ions is examined by showing the characteristics of the frictional powe r loss at each pair.