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Published in David A. Cardwell, David C. Larbalestier, Aleksander I. Braginski, Handbook of Superconductivity, 2023
Figure F1.1.13 shows the first commercial pulse tube cryocooler (a GM-type), which was introduced in Japan in 1993, and made available worldwide later in similar versions. It utilizes the U-tube geometry and is driven with a Gifford–McMahon compressor requiring about 800 W of input power. A rotary valve provides the pressure oscillation and is located some distance from the cold head to reduce EMI from the valve motor. The oscillating frequency is about 1 Hz. This pulse tube provides 2 W of refrigeration at 77 K. Figure F1.1.14 shows a commercial two-stage 4 K pulse tube cryocooler (GM-type) that provides 0.5 W at 4.2 K with about 5 kW of input power. Figure F1.1.15 shows an example of a space-qualified pulse tube cryocooler (Stirling-type) designed for cooling infrared sensors. It can provide 7 W of cooling at 80 K with 125 W of compressor input power at 300 K (15% of Carnot) (Raab and Tward, 2010). Several have flown in space with some logging more than 10 years of continuous operation with no degradation (Raab and Tward, 2010; Ross, 2016). It uses the latest technology in flexure-bearing compressors to reduce the size and mass of the compressor. The cold head is an inline arrangement, and the reservoir volume is an annular volume outside the left linear compressor. The total mass is about 4.3 kg. Commercial Stirling-type pulse tube cryocoolers are available with refrigeration powers up to 1 kW at 80 K.
Refrigeration Lubricants
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
Mark R. Baker, Michael G. Foster
The requirement to meet tighter efficiency targets has resulted in the following: Increase in the use of variable speed and linear compressor technology. Improvement gains of more than 30% can be achieved.Increased interest in low GWP refrigerants (ammonia, carbon dioxide, hydrocarbons, R-1234yf, etc.).Shift to lower-viscosity lubricants.Shift to screw and scroll compressors. In general, screw and scroll compressors have the advantages of higher reliability, higher efficiency, and lower noise.
Challenges in implementation of a moving coil linear compressor in a household refrigerator
Published in International Journal of Ambient Energy, 2022
Amit Jomde, Virendra Bhojwani, Suhas Deshmukh
A linear compressor is well known for its excellent performance in Stirling cryocooler, space application. Minimum linkages, lesser friction points and lower noise characteristics make the linear compressor more promising in the space application. The same technology has not emerged as an alternative compression technology for ground applications such as home refrigerators, air conditioners, electronic cooling. The compressor plays a vital role in the vapour compression refrigeration (VCR) system. The compressor is the heart of the VCR system as it compresses the working fluid (refrigerant), increasing its pressure to release heat further in the cycle during condensation. The reciprocating compressors are the conventional compressors for household refrigeration application. These compressors have their drawbacks such as a high rate of wear, friction and lateral forces by the piston on the cylinder walls and increasing noise level during the conversion of rotary motion to linear motion using the crank and connecting rod mechanism. The linear compressor technology offers various advantages vis-a-vis a reciprocating compressing machine. It comprises a spring-piston arrangement, driven by a linear motor. A linear motor reduces the mechanical losses, noise level and the lateral forces in linear compressor operation. Hence, this technology is very silent in operation. In addition to this, a linear compressor is a resonant machine, i.e. the dynamic behaviour of the oscillating components of compressor results in maximum efficiency under resonance condition.
Resonance analysis of opposed piston linear compressor for refrigerator application
Published in International Journal of Ambient Energy, 2019
Suneeta Phadkule, Sohel Inamdar, Asif Inamdar, Amit Jomde, Virendra Bhojwani
The modern linear compressor technology offers various advantages over a reciprocating compressor. This is the most popular among recent compression technologies. It uses a spring–mass arrangement (the piston mounted on a mechanical spring system) driven by a linear motor. An opposed piston linear compressor uses a linear motor for reciprocation of the piston, hence directly reducing the frictional losses involved in the reciprocating compressor. Since, the motor forces are in the direction of motion of the piston, side forces are zero. Hence, it leads to a silent operation. This arrangement reduces frictional losses and other mechanical losses, increasing the efficiency. The progress in the fields of cryogenics, refrigeration and air conditioning has kept increasing demands for the development of the compressors with higher efficiencies.
Performance predictions and parametric analysis of a valved linear compressor using a mathematical model
Published in International Journal of Ambient Energy, 2018
Amit Jomde, A. Anderson, Virendra Bhojwani, Mitali Deshmukh
A Linear compressor is one of the highest available efficiency compression technologies. A linear compressor consists of an oscillating motor and a piston rigidly coupled to it. Oscillations of the linear motor are directly transferred to the piston. The piston performs compression and suction alternately similar to the reciprocating compressor. Since the crank and the connecting rod mechanism are absent in the linear compressor the friction losses are less and mechanical efficiency of the linear compressor is more. Lee et al. (2004) reported the significance the linear compressor for air conditioning systems. The present paper reports the potential of the mathematical model developed by the authors and various parameters predicted by the code. Pollak et al. (1978) developed a mathematical model explaining certain characteristics of the oscillating electrodynamic compressor which have been observed experimentally. The sensitivity of efficiency with driving frequency and pressure ratio with mass flow rate has been presented. Liang et al. (2014) compared a novel oil-free linear compressor and crank-drive reciprocating compressor. The measurements were done using nitrogen as a refrigerant. The motor performance and overall efficiencies of two compressors have been reported. The motor efficiency of the moving magnet linear compressor is higher than that of a conventional induction motor used in the crank-drive reciprocating compressor at low power inputs. The linear compressor has been developed and reported for vapour compression systems Lee et al. (2000), Lee et al. (2004), Kim and Jeong, (2013), Kim and Jeong, (2014), Liang et al. (2013), Park et al. (2002), Reed et al. (2005). Bradshaw, Groll, and Gorimella (2013a, 2013b) worked on sensitivity analysis of a linear compressor for electronics cooling, energy recovery, and its benefits.