Start-up Characteristics of Linear Compressors in a Refrigeration System


This work investigates the start-up characteristics of linear compressors in a refrigeration system through experiment and simulation. Experiments are carried out by a refrigeration test system with a linear compressor controlled by a LabVIEW platform. A simulation model that considers the nonlinear process of gas force is set up on the basis of Runge-Kutta method for linear compressors. Compared with the experimental results, the simulation errors are within 15%, including the unstable state. The influences of ambient temperature and power frequency on linear compressors are studied through experiments. Unstable phenomena exist at 25°C ambient temperature compared with the designed ambient temperature of 35°C. The unsteadiness mechanism is analyzed by simulation. Simulation analysis indicated that two sensitive stages of linear compressors, namely, starting to pump and touching top dead center, are unstable. Furthermore, properly increasing equivalent mass (approximately 3%) or spring stiffness during the design stage can be a practical method to improve the stability of linear compressors.

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A :

piston sectional area/m2

c :

equivalent damping coefficient/N·s·m−1

c f :

friction damping coefficient/N·s·m−1


electromagnetic force/N

F g :

force load acting on the piston/N

f :

power frequency/Hz

f d :

inherent frequency with damping/Hz

f n :

inherent frequency without damping/Hz

H :

piston stroke/m

I :

effective current/A

i :


K 0 :

electromagnetic force coefficient/N·A−1

k s :

stiffness coefficient of syntonic springs/N·m−1

k d :

stiffness coefficient of discharge springs/N·m−1

k :

equivalent stiffness coefficient/N·m−1

L e :

equivalent inductance/H

m 1 :

moving part mass/kg

m 2 :

frame mass/kg


discrete points of each cycle for simulation

P i :

input power/W

P o :

output power/W

P c :

pressure inside of the cylinder/Pa

p d :

discharge pressure/Pa

p s :

suction pressure/Pa

p :


R e :

equivalent resistance/Ω

r 1 :

leakage rate

U :

effective voltage/V

U a :

voltage amplitude/V

u :

supply voltage/V

v :

piston velocity/m·s−1

X d :

preload distance of discharge spring/m

X i :

piston initial clearance position/m

x t :

dispersed displacement/m

x :

piston displacement/m

η :

compressor efficiency

η m :

linear motor efficiency

κ :

adiabatic index


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We would like to thank the support from the National Natural Science Foundation of China (No. 51576203 and No. 51976229). And this study is also supported by CAS Key Laboratory of Cryogenics, TIPC (No. CRYOQN201908). Dr. Tang M.S. is supported by Youth Innovation Promotion Association, CAS (No. 2018032).

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Correspondence to Mingsheng Tang.

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Zou, H., Li, X., Tang, M. et al. Start-up Characteristics of Linear Compressors in a Refrigeration System. J. Therm. Sci. (2020).

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  • linear compressor
  • start-up
  • dynamic characteristics
  • unsteadiness