Reciprocating Refrigeration Compressor Research Articles

Vibration-Based Measurement of Activated Cylinders in Reciprocating Machines

Vibration signals from rotating and reciprocating machines provide insights into machine health and operating parameters. Reciprocating machines often feature cylinder deactivation systems for increased efficiency. This article presents a vibration-based method for the detection of activated cylinders in reciprocating machines. Simulated compressor vibration signals demonstrate the effect of cylinder conditions on spectral-coherence and mean-envelope-spectrum (MES) estimates. Physical parameters of the mechanical system and the results of the simulations advise the proposed method. With an appropriately chosen region of interest (ROI), the MES-based indicator (MESbI) correctly identified the number of activated cylinders of a four-cylinder reciprocating refrigeration compressor in both field and laboratory test setups. A discussion section addresses measurement uncertainty and calibration, and provides an example application.

Modelling and Measurement of a Moving Magnet Linear Motor for Linear Compressor

For the purpose of efficiency improvement, a linear motor that performs a linear reciprocating motion can be employed to directly drive the piston in a reciprocating refrigeration compressor without crankshaft mechanism. This also facilitates the modulation of cooling capacity as the stroke and frequency can be readily varied in response to heat load. A novel design of moving magnet linear motor for linear compressor was analyzed in the paper. A finite element analysis (FEA) model was built to simulate the characteristics of the linear motor. Current and displacement signals were measured from a test rig and were defined in the transient FEA model. Transient motor force was simulated with the FEA model and good agreements are shown between the results from the FEA model and interpolated shaft force from static force measurements. Major Losses, such as copper loss and core loss were also computed. Motor efficiency decreased from 0.88 to 0.83 as stroke increased from 9 mm to 12 mm, while the pressure ratio remained unchanged. Comparisons were made between the present moving magnet linear motor and moving coil linear motors. Generally, the moving magnet linear motor demonstrates higher efficiency than moving coil motors, which have significantly higher copper loss. The present moving magnet design with simple structure could be further optimized to improve motor efficiency.

Design Manufacture and Performance Test of A Reciprocating Refrigeration Compressor

Design Manufacture and Performance Test of A Reciprocating Refrigeration Compressor

Optimum Design on Structural Parameters of Reciprocating Refrigeration Compressor Crankshaft

Crankshaft is one of the main components of a piston refrigeration compressor. Its structure parameters influence the reliability and service life. [Research objective] Improve the reliability of the crankshaft and further understand the impact of structural parameters on the strength of the crankshaft. [Research method] The forces acting on crankshaft are analyzed on the basis of dynamic calculation of reciprocating compressor working process. Finite Element Method (FEM) is applied for three-dimensional modeling and static strength analysis. [Research result] The stress at the transition fillet of crankshaft journal under the maximum comprehensive piston force is obtained accordingly. The reliability and accuracy of this model is verified by the experimental results. The influence of the crankshaft with crankpin diameter, center distance of adjacent crankpins and fillet radius on stress concentration has been investigated in detail. The optimal undercut fillet is designed for reducing the maximum stress obviously. The results provide a reference for similar design and production of compressor crankshaft.

Experimental study on stepless capacity regulation for reciprocating compressor based on novel rotary control valve

A capacity-regulation system based on a novel rotary control valve for reciprocating refrigeration compressor is proposed and designed for the first time. The regulation system is mainly composed of a rotary control valve and an adaptive regulation system. The structure and working principle of the rotary control valve is described in detail, and the control process of the adaptive regulation system for the valve is studied together with the program design. In addition, the parameters for the design and control of the rotary control valve are theoretically determined. To verify the feasibility and effectiveness of the proposed system, a three-cylinder reciprocating compressor was adopted as a test device. Experimental results showed that the technology was able to realize continuous stepless capacity regulation for the compressor within the range of (0)10–100%, and power consumption decreased correspondingly with the load reduction.

Dynamic simulation of reciprocating refrigeration compressors and experimental validation

Among the various ways to simulate compressor behaviour, using efficiency definitions such as volumetric, isentropic or effective is relatively easy to perform and rapid when dynamic simulation is required. Calculating these efficiencies and their dependence on operating pressure, refrigerant type, and temperature is on the contrary relatively difficult to estimate. The approach presented here supposes that they depend essentially on two parameters, the dead volume ratio, having a particular influence on volumetric efficiency, and a friction factor mainly influencing both isentropic and effective efficiencies. The bases of the model are tested for a reversible and for a non-reversible reciprocating compressor when simulated over a compression cycle and dead volume ratio and friction factor influence is studied and discussed. Finally, the model is compared to experiments and allows validating the method, giving quite accurate results.

Analysis of oil pumping in a reciprocating compressor

The immediate provision of lubricant oil to the radial and thrust bearings and to the piston–cylinder gap in reciprocating refrigeration compressors is a crucial reliability issue following compressor start-up. The aim of this paper is to present a hydrodynamic analysis of the lubricant oil pumping system of a reciprocating compressor using computational fluid dynamics (CFD). In the present system, oil is pumped from the sump through a reed-type centrifugal pump located at the bottom end of the shaft. The oil flows initially as a climbing film on the internal surface of the shaft before it is directed to the external surface where it flows along a helix channel carved on the shaft wall. The model was implemented on the commercial package Fluent using the volume of fluid (VOF) method to resolve the free-surface oil flow. Parameters regarding the oil behavior during start-up, such as the time required to reach steady-state operation and the associated oil mass flow rate are explored in the manuscript.

Performance analysis of reciprocating compressors through computational fluid dynamics

An experimentally validated numerical analysis of reciprocating refrigeration compressors is presented. The finite-volume methodology is adopted to solve the flow field and a one-degree-of-freedom model is used to describe the valve dynamics. The variation of the computation domain, associated with the valve and piston displacements, is taken into account and the time-dependent flow field and the valve dynamics are coupled and solved simultaneously. The three-dimensional formulation considered in the analysis allowed the simulation of actual suction and discharge muffler geometries. Numerical results were validated with reference to experimental data for valve displacement and pressure in the suction and compression chambers obtained in a calorimeter facility. A study was carried out to identify the contributions of mufflers and valves to the compressor thermodynamic losses.

Heat transfer study of a hermetic refrigeration compressor

This paper presents an analytical study on heat transfer and temperature distribution for a hermetic reciprocating refrigeration compressor using the lumped thermal conductance approach. In this analysis, the intricate components of a hermetic compressor were divided into 46 geometrically simplified discrete elements and each was assumed to be at a uniform temperature. The lumped thermal conductance method was then applied to all the components of the compressor to form 46 simultaneous equations, which were then solved to get the components’ temperatures. The results obtained were in good agreement with measurement. The discrepancies in the prediction lie in the assumptions made in assigning various heat transfer correlations to model the convection heat transfer effects of the fluid and solid surface boundaries, and the simplification made in distributing the various components of the compressor into discrete parts. The results of this study have been applied to actual compressor design in industry and have resulted in improved compressor performance.

An exergy method for compressor performance analysis

An exergy method for compressor performance analysis is presented. The purpose of this is to identify and quantify defects in the use of a compressor's shaft power. This information can be used as the basis for compressor design improvements. The defects are attributed to friction, irreversible heat transfer, fluid throttling, and irreversible fluid mixing. They are described, on a common basis, as exergy destruction rates and their locations are identified. The method can be used with any type of positive displacement compressor. It is most readily applied where a detailed computer simulation program is available for the compressor. An analysis of an open reciprocating refrigeration compressor that used R12 refrigerant is given as an example. The results that are presented consist of graphs of the instantaneous rates of exergy destruction according to the mechanisms involved, a pie chart of the breakdown of the average shaft power wastage by mechanism, and a pie chart with a breakdown by location.

Experimental thermodynamic analysis of a variable-speed open reciprocating refrigeration compressor

An experimental analysis of the thermodynamic behaviour of an open reciprocating refrigeration compressor, whose capacity is modulated by variation of its speed, is hereby presented. The main parameters describing performance and thermodynamic efficiency at several values of suction and discharge pressure and varying speeds, are also presented and discussed. A significant increase of compressor efficiency at lower speeds has been found.

Flow visualization applied to a small refrigeration compressor

This paper describes a flow visualization technique that was used to evaluate qualitatively the gas flow pattern inside a small, hermetically sealed, reciprocating refrigeration compressor. The applicable compressor designs are those in which the suction gas from the evaporator is dumped into the compressor shell, and is then drawn through a muffler into the suction plenum of the compressor. The physical separation of the muffler inlet from the suction gas inlet serves to reduce compressor noise and also provides an easy and convenient means of separating any liquid (compressor oil or liquid refrigerant) from the refrigerant gas. For the flow visualization studies the compressor housing was replaced by a clear plastic shell. Atmospheric air seeded with white smoke was the working fluid. The suction inlet and muffler were parts from a commercial compressor. The flow pulsations were modelled by connecting the muffler outlet to the input plenum of an auxiliary compressor. The flow patterns near the muffler inlet were recorded with a video camera. The mixing of the inlet gas with the gas circulating inside the muffler was studied. The effect of alignment and offset of the muffler inlet relative to the suction inlet, the effect of muffler size, and the effect of a shroud around the muffler were studied. The results were used to guide a companion study of detailed temperature and pressure measurements inside a working compressor.

Solar assisted heat pump

The paper describes a series solar heat pump, using Freon 11 as the working fluid. The heat pump is specifically designed for use in a tropical climate where the normal daytime ambient of above 25°C permits the evaporator to be operated at a high temperature (15–50°C depending on solar input). The use of Freon 11 permits conventional reciprocating refrigeration compressors to be used at elevated temperatures without exceeding design pressure limits. A single unit acts as the evaporator and solar collector. When solar insolation is low the evaporator pressure automatically drops so that energy is received from the atomsphere. However the C.O.P. and output are so low in this mode that the system cannot correctly be termed dual source. The water cooled condenser operates in the temperature range of 35–90°C, the heated water representing the useful output of the system. Operation in the air conditioning mode is not possible due to the large specific volume of Freon 11 at low temperatures. A theoretical analysis is presented to describe the system operation, and the experimental results are shown to agree well with the computer simulation. Average values of C.O.P. of between 2.5 and 3.5 were obtained for the small prototype developed with high side storage temperatures of up to 80°C.

Thermodynamics of a Hermetic Reciprocating Refrigeration Compressor With MCCT-Piston and Valve System

Research Papers Thermodynamics of a Hermetic Reciprocating Refrigeration Compressor With MCCT-Piston and Valve System M. C. C. Tsao M. C. C. Tsao Westinghouse R&D Center, Pittsburgh, Pa. 15235 Search for other works by this author on: This Site PubMed Google Scholar Author and Article Information M. C. C. Tsao Westinghouse R&D Center, Pittsburgh, Pa. 15235 J. Mech. Des. Apr 1981, 103(2): 310-317 (8 pages) https://doi.org/10.1115/1.3254909 Published Online: April 1, 1981 Article history Received: March 1, 1980 Online: November 17, 2009

Simulation of reciprocating gas compressors with automatic reed valves

The simulation of high-speed reciprocating refrigeration compressors was motivated by the needs of design engi neers. In this paper a mathematical model describing the dynamic behavior of a reciprocating compressor is pre sented. The model is semianalytic in that two types of empirical factors are required to relate phenomena not yet analytically predictable. One type is obtained from steady- state tests and the other by trial and error based on com parison with experimental results. Both analog and digital computers were considered as means of simulating the model. Due to nonlinearities in the model, the digital com puter, using Fortran IV, was selected. To evaluate the sim ulation, a one-quarter horsepower 3600-rpm stock com pressor was modified and used as a laboratory vehicle. A typical correlation between the computer simulation and experimental results is given. In general, good correlation was achieved.

冷凍機用圧縮機の最近の動向(<小特集>冷凍機・空気調和)

冷凍機用圧縮機の最近の動向(<小特集>冷凍機・空気調和)