Overall performance of the duplex Stirling refrigerator (original) (raw)
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Maximized Performance of Stirling Cycle Refrigerators
An investigation has been conducted into the performance of free-piston Stirling coolers (FPSC) integrated with well insulated cabinets. An issue of particular importance is identifying test conditions for FPSCs that correspond to known test conditions for cabinets. This depends to some extent on the installation methodology (Berchowitz et al, 1996). Test points for evaluating the potential performance of FPSCs are discussed. Using optimized free convection heat exchangers for both the warm and cold sides together with an optimized FPSC, it is shown that significant performance gains are possible for well insulated one-temperature cabinets. Freezers and two-temperature cabinets are expected to have an even greater margin. An evaluation of current level FPSC technology shows that a 25% advantage for a 365 liter one-temperature vacuum insulated cabinet should be achievable. This has been verified in an Engineering Model installation. Independent testing of a second Demonstration Model was unable to confirm these expectations owing mainly to a performance degradation of the cooler. Best estimate performance calculations show that as cabinet heat leak is reduced, the FPSC advantage improves. Mass and volume comparisons of FPSCs and Rankine compressors are included.
Parametric Investigation and Univariant Optimization of Domestic Stirling Refrigerator
International Journal of Energy Research, 2023
As the temperature range of the cooling machine affects the cooling performance, parametric optimization of moderate temperature Stirling refrigerator has valuable concept. In this paper, a nonideal modified simple numerical model was used to investigate the effects of parameters and to propose optimized Stirling refrigerator design for moderate temperature applications. The analysis was conducted through simulating the numerical model using MATLAB code for beta configuration FEMTO-60 prototype operating as a refrigerator. The effects of shuttle heat loss and mass leakage on the cooling performance of domestic Stirling refrigerator have been studied. Moreover, the effects of operating parameters (operating frequency and charging pressure) and design parameters (phase angle, regenerator length and porosity, displacer height, swept volume ratio, and piston diameter to stroke ratio) have been investigated. A cooling power of 625 W and COP of 1.3 have been found at a charging pressure of 22.5 bar and an operating frequency of 6 Hz using the optimized design parameters. The optimized parameters (operating and specified design parameters) could deliver from 48% to 60% more cold production and from 30% to 40% more COP than the existing design with a safe working condition.
Thermodynamic Comparison of Two Types of Stirling Refrigerators
The pulse-tube type of two-piston Stirling refrigerator can improve reliability by moving the expansion piston from the cold end to the ambient temperature end. More recently, the thermoacoustic-Stirling refrigerator further improves reliability by eliminating the expansion piston. The thermoacoustic-Stirling refrigerator uses a traveling-wave loop to achieve the Stirling cycle. Both refrigerators have a pulse tube. By means of thermodynamic analysis of the two refrigerators, this paper draws the following conclusions. Firstly, the pulse tube type of Stirling refrigerator can readily achieve any needed phase shifting by controlling the expansion piston, and it does not have to rely on the flowing resistance of the regenerator and the compliance and inertance effects of the different thermodynamic components that make contributions to phase shifting of the pressure and velocity waves. In contrast, the thermoacoustic-Stirling refrigerator is not able to perform active phase shifting, and its phase shifting mechanism is completely passive and somewhat dissipative because the flow resistance of the regenerator is a necessary part of the passive phase shifting. As a result, the pulse-tube type of two-piston Stirling refrigerator can achieve a little higher efficiency than the thermoacoustic-Stirling refrigerator. Secondly, the standing-wave acoustic field in the compression space of the thermoacoustic-Stirling refrigerator is predominant, resulting in smaller power flow for the same pressure wave amplitude and swept volume. In other words, the thermoacoustic-Stirling refrigerator may give smaller cooling power with the same working conditions and component sizes. Actually, the calculations show that the two-piston Stirling refrigerator gives a much larger cooling capacity than the thermoacoustic-Stirling refrigerator.
Entropie : thermodynamique – énergie – environnement – économie, 2021
The design of a Stirling machine requires the understanding of the processes that govern their operation to predict the optimum operating parameters of the machine. The modified simple model using the geometrical parameters of the FEMTO-ST engine model is applied in this paper to investigate the trend of losses with respect to operating frequency and charging pressure. The variation of pressure drops across the regenerator and heat exchangers have been investigated as functions of operating frequency and charging pressure in order to predict the extent of fluid friction losses. The share of different power and heat losses as well as their effects on cooling performance have been evaluated at the different operating frequencies and charging pressures. The share of fluid friction loss and loss due to regenerator imperfection increase with rotational speed and charging pressure.
Performance of an Alpha-type Stirling Refrigerator with shell and tube condenser and evaporator
2019
Abstract: This paper investigates the performance of an alpha type Stirling refrigerator using shell and tube heat exchanger as evaporator and condenser with helium as a working fluid. The refrigerator is an alpha configuration. The pistons synchronization is driven by a crank-shift mechanism. A computer program in a form of spreadsheet was prepared to solve the refrigerator cycle numerically in the vision of Schmidt theory. The studied parameters are; dimensions of evaporator, condenser, and regenerator, stroke/bore ratio, speed, and phase angle. The study is directed towards the determination of the parameters that result in higher cooling load with a considerable coefficient of performance. The results show that, the refrigerator develops 0.00096 TR/cc, COP/COP Carnot = 0.1346 at 750 rpm. The comparison among the present work and previous ones shows that; the present refrigerator explores an enhancement in COP up to 100%, especially at low-speed levels.
A Gamma type Stirling refrigerator optimization: An experimental and analytical investigation
International Journal of Refrigeration, 2018
In this study, multi-objective optimization of a Gamma type Stirling refrigerator is carried out based on the experimental and analytical results. The cooling capacity and the coefficient of performance (COP) are experimentally investigated for helium and air. Beside to helium and air, carbon dioxide is also considered as the working fluid in the simulation. A non-ideal adiabatic analysis is developed for the simulation. The experimental and simulation results showed that the cooling capacity increases continuously with the rotational speed where the COP has a maximum value. The optimum COP value for helium occurs at higher rotational speed than that of the air. The Design of Experiment (DOE) method is used for multi-objective optimization. Three parameters namely COP, cooling capacity and pressure drop are investigated in this optimization study. Only helium and carbon dioxide are considered for optimization because of their higher specific heat capacity and enthalpy with respect to air. The optimum working pressure for the carbon dioxide takes place at lower pressure than that of helium. When the importance and weight factors equal one, the optimum point for helium is obtained at working pressure and rotational speed of 9 bar and 451.1 rpm, respectively. Where, the optimum point for carbon dioxide is found at working pressure and rotational speed of 3.3 bar and 798.5 rpm, respectively.
Performance of V-type Stirling-cycle refrigerator for different working fluids
International Journal of Refrigeration, 2010
The thermodynamic analysis of a V-type Stirling-cycle Refrigerator (VSR) is performed for air, hydrogen and helium as the working fluid and the performance of the VSR is investigated. The V-type Stirling-cycle refrigerator consists of expansion and compression spaces, cooler, heater and regenerator, and it is assumed that the control volumes are subjected to a periodic mass flow. The basic equations of the VSR are derived for per unit crank angle, so time does not appear in the equations. A computer program is prepared in FORTRAN, and the basic equations are solved iteratively. The mass, temperature and density of working fluid in each control volume are calculated for different charge pressures, engine speeds, and for fixed heater and cooler surface temperatures. The work, instantaneous pressure and the COP of the VSR are calculated. The results are obtained for different working fluids, and given by diagrams.
Stirling machine for cooling production at intermediate temperature range
2021
The Stirling technology presents an opportunity to achieve environmental protection in terms of greenhouse gas emissions and global warming. It is an alternative technology to vapour compression cycles that use refrigerant fluids. The described system is a Beta Stirling refrigerator working with nitrogen for cooling production at moderate temperature. The cooling performances are studied under different rotational speeds and heat loads. We have carried out experimental results with heat load to simulate the cooling capacity from 0 W (no load) to 650 W in the cooling temperature range-70°C to 20°C. The coefficient of performances and cooling efficiency are discussed.
The application of Stirling cooler to refrigeration
IECEC-97 Proceedings of the Thirty-Second Intersociety Energy Conversion Engineering Conference (Cat. No.97CH6203), 1997
The application field of the free-piston Stirling Cooler, Model 100A of Global Cooling BV in the refrigeration has been studied. The cooling effectiveness of the free-piston Stirling Cooler which means small capacity with better efficiency, large range of temperature and capacity modulated operation is of much use to cool a space insulated well. One practicable application is suggested here, in which FPSC and secondary heat transfer fluid are used to the single temperature refrigerator (60 liter) instead of conventional vapor compression machines. In the freezer operation at-20°C inside cabinet, the steady-state test results show 25% improvement in energy consumption over original one. The application of free-piston Stirling Cooler to a freezer at lower temperature shows great potentials also.
Thermodynamic Analysis of the Stirling Duplex Machine
Advanced Engineering Forum
The Stirling Duplex concept, in which a Stirling engine drives a Stirling heat pump, has many energy and environmental benefits. This machine is essentially composed of three movable elements, a working piston and two displacers, in the same enclosure. The machine has two circuits of non-polluting working fluid, in both parts, engine and refrigerator.The compatibility of the Stirling machine with any type of thermal energy as an external combustion engine contributes to its industrial interests and scientific research. In this paper, a study is presented to estimate Stirling Duplex$'$s parameters and efficiencies by considering the adiabatic model. It appears that the Stirling Duplex is more efficient as a heat pump than as a refrigerating machine.