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. This paper discusses the challenges observed during the implementation of the moving coil linear compressor in home refrigerators. The prototype moving coil linear compressor has been developed and tested by integrating to the home refrigerator.

Amit Vishnu Jomde

School of Mechanical Engineering

Engineering and Technology

Virendra Bhojwani

Suhas Deshmukh

MIT-World Peace University (MIT-WPU) is a top educational institute located in Pune, India. It is recognized within&nbsp;UGC under Government of Maharashtra Act No. XXXV 2017.&nbsp;

It is part of the MIT group of institutions (established in 1983) which covers 10+ campuses across India and has more than 50,000+ students enrolled across various disciplines at a given point of time. The institute houses 15 schools ranging from Engineering &amp; Technology, Design, Pharmacy, Commerce, Governance among others. It offers undergraduate, postgraduate and PhD programs among different disciplines.&nbsp;

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MIT World Peace University

Challenges in implementation of a moving coil linear compressor in a household refrigerator

International Journal of Ambient Energy, Taylor & Francis

A prototype of the compressor with moving coil type linear motor has been developed. The developed compressor is integrated with test loop using R134a refrigerant to confirm its performance. The simulation results are validated with the experimental data. The experimental results from the test loop with strokes of 10, 11 and 12 mm for three different pressure ratios of 4, 7, 10 are presented and discussed in this paper. The COP of the system calculated is 1.4 from the test results (for 54 °C condenser temperature and −20 °C evaporator temperature) with the stroke of 10 mm, pressure ratio of 10 and cooling capacity of 134 W. The maximum COP of 2.13 is achieved (for 54 °C condenser temperature and 2 °C evaporator temperature) with the stroke of 12 mm, pressure ratio of 4 and cooling capacity of 325 W. Normal refrigerator compressors utilize lubricant oil but as the refrigerant is changed the oil suitable for particular refrigerant also needs to be changed. The novel linear compressor tested does not utilize lubricant oil. The linear compressor has only one friction point i.e. between the piston and cylinder. The linear compressor utilizes Rulon (low coefficient of friction material) as a special material coated on the piston surface in contact with the cylinder. The oil-free operation of the compressor helps in adapting the refrigerator to different refrigerants without having to consider a change of lubricating oil. Refrigeration system performance with both linear compressor and the conventional reciprocating compressor is measured and compared. System COP with the linear compressor is 18.6% more than with the commercially available reciprocating compressor. The absence of connecting rod and crank mechanism accompanied with oil-free operation due to reduced friction enhance the performance of the linear compressor.

International Journal of Refrigeration, Elsevier

Modelling and measurement of a moving coil oil-free linear compressor performance for refrigeration application using R134a

The opposed piston linear compressor is considered to be the future of silent, reliable and efficient compression technologies. For long valves, less linear compressors have been widely used in cryocoolers for space applications. Recently research has established its high-performance characteristics which are useful in household refrigeration application. Unlike reciprocating compressors which are driven by rotary motors and need a crank connecting rod mechanism to convert rotary into linear motion, a linear compressor is driven by a linear motor which reduces the number of moving parts. This feature makes the compressor more reliable, more efficient and has a silent operation. The piston (suspended on spring stiffness) in the linear compressor is a free piston, i.e. motion of the piston is not constrained hence the performance of the linear compressor is highly dependent on system resonance. Free piston motion offers the unique advantage of ease of modulation, i.e. the stroke of the compressor and hence the delivery mass flow rate coming out of the compressor can be easily controlled by changing the supply voltage. Resonance in the linear compressor is a function of moving mass, spring stiffness and operating or electrical frequency. Achieving resonance in the linear compressor results in maximising the cooling performance of the refrigerator and minimising the input power requirement and hence an increase in the COP of the refrigeration system. The present paper discusses the results from resonance testing of the opposed piston linear compressor for household refrigerator using the fast Fourier transformation analysis. There are different parameters that are considered to optimise the natural frequency of the opposed piston linear compressor, consisting of frequency, moving mass, and spring stiffness. The piston performs compression and suction in a similar manner as in the conventional reciprocating compressor. An opposed piston linear compressor exhibits high energy efficiency due to its simple construction and less moving parts, its mechanical losses are much less than the reciprocating compressor.

Resonance analysis of opposed piston linear compressor for refrigerator application

A mathematical model for a linear compressor with valves is developed. A linear compressor consists of an oscillating motor and a piston rigidly coupled to it. The mathematical model deals with the dynamic equation of a linear compressor consisting of inertia, motor force, and damping. It also solves the electrical circuit equation to estimate the current flowing through the motor circuit. The model considers the dynamic operation of suction and discharge valves. The refrigerant properties are estimated by interfacing the programme with REFPROP to predict the cylinder instantaneous pressure and temperature. Finally, the model predicts the net cooling capacity, compressor input power, and COP for the given compressor geometry. The mathematical model is validated with the experimental results reported by Lee et al. (2004. ‘Linear Compressor for Air-Conditioner.’ L. G. Electronics, international compressor engineering conference, Purdue University, C047, 1–7). Parametric analysis of the compressor is done by varying parameters like input voltage, refrigerant, and superheating temperature of the refrigerant. Results generated by the mathematical model are presented and discussed.

Journal	International Journal of Ambient Energy, Taylor & Francis
Publisher	Taylor & Francis
ISSN	01430750
Open Access	No