Abstract
This paper compares the system performance for two representative capacity control schemes, hot-gas bypass and variable speed compressor in an oil cooler for machine tools. An empirical linear first-order model of each controlled system was obtained from experiments by imposing a stepwise control signal to each actuator of the system. General proportional-integral controllers are designed based on the empirical transfer function models in order to control the target temperature of the oil cooler system. The experiments of starting and thermal load change were conducted to compare their control performance with each other. Especially, coefficient of performance (COP) of the two control schemes under the partial load state was also analyzed in detail. From the analyses of experimental results, the control performance of the target temperature in the two control schemes had almost the same control accuracy of ±0.1 °C at steady state. However, the COP of a variable speed compressor was as many as five-times greater than that of hot-gas bypass in comparable minimum partial load state of 0.5 kW.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
S. W. Lee, H. K. Yeom and K. J. Park, Performance of hot gas bypass type oil cooler system, Journal of Korean Society for Precision Engineering, 26(3) (2009) 73–80.
S. M. Beak, J. H. Choi, J. Y. Byun, C. G. Moon, H. S. Lee, S. K. Jeong and J. I. Yoon, Characteristics of temperature control by hot-gas bypass flow rate on industrial water cooler, Journal of the Korean Society of Marine Engineering, 33(8) (2009) 1129–1136.
S. W. Lee and H. K. Yeom, Performance of thermal error controller to minimize thermal deformation of machine tools, Proceeding of Korean Society for Precision Engineering (2008) 376–380.
C. S. Yi, J. H. Yun, I. G. Jeong, J. S. Suh and C. K. Song, Predicting the oil cooler fan performance of large-sized diesel engines by changing the outlet and torsion angles, Journal of Mechanical Science and Technology, 27(2) (2013) 469–475.
Hua Li, S._S. You, J. I. Yoon and S. K. Jeong, An empirical model for independent control of variable speed refrigeration system, Applied Thermal Engineering, 28 (2008) 1918–1924.
Hua Li, S. S. You and S. K. Jeong, Feedforward control of capacity and superheat for a variable speed refrigeration system, Applied Thermal Engineering, 29 (2008) 1067–1074.
Y. M. Jung, J. Y. Byun, J. I. Yoon and S. K. Jeong, A study on high precision temperature control of an oil cooler for machine tools using hot-gas bypass method, Journal of the Korean Society of Marine Engineering, 33(7) (2009) 1003–1011.
S. K. Jeong and D. B. Lee, Comparison of system performances of hot-gas bypass and compressor variable speed control of water coolers for machine tools, SAREK, 24(1) (2012) 1–8.
J. H. Ahn, Y. J. Joo, I. Y. Cho, H. Kang, Y. C. Kim and J. M. Choi, An experimental study on the performance characteristics of a heat pump system in the heating operation mode with the hot gas bypass, SAREK (2009) 539–543.
M. Yaqub, S. M. Zubair and Jameel-ur-Rehman Khan, Performance evaluation of hot-gas bypass capacity control scheme for refrigeration and air-conditioning systems, Energy, 25 (2000) 543–561.
M. Yaqub, S. M. Zubair and S. H. Khan, Second-law-based thermodynamic analysis of hot-gas bypass, Capacity-control Schemes for Refrigeration and Air-conditioning Systems, Energy, 20(6) (1995) 483–493.
J. W. Choi, I. H. Lee and M. S. Kim, Experimental study on steady state heating performance of a multi-type heat pump system for finding the optimum control variable, Journal of Mechanical Science and Technology, 25(6) (2011) 1415–1422.
J. L. Lin and T. J. Yeh, Modeling, identification and control of air-conditioning systems, International Journal of Refrigeration, 30 (2007) 209–220.
S. C. Kim, D. S. Hong and W. J. Chung, Temperature control for an oil cooler system using PID control with fuzzy logic, Transactions of the Korean Society of Machine Tool Engineers, 13(4) (2004) 87–94.
O. Ekren, S. Sahin and Y. Isler, Comparison of different controllers for variable speed compressor and electronic expansion valve, International Journal of Refrigeration, 33 (2010) 1161–1168.
S. C. Kim, D. S. Hong and W. J. Chung, Temperature control for an oil cooler system using PID control with fuzzy logic, Transactions of the Korean Society of Machine Tool Engineers, 13(4) (2004) 87–94.
C. W. Lee and K. H. Shin, Strip tension control considering the temperature change in multi-span systems, Journal of Mechanical Science and Technology, 19(4) (2005) 958–967.
Author information
Authors and Affiliations
Corresponding author
Additional information
Recommended by Associate Editor Man-Yeong Ha
Seok-Kwon Jeong is a Professor in Department of Refrigeration and Airconditioning Engineering, Pukyong National University. His Ph. D. is from Yokohama National University in 1995. His research interests include automatic control of the refrigeration and airconditioning system, motion control using AC motors, modeling of discrete system, etc.
Dan-Bi Lee received the B.E. and M.E. in Refrigeration and Air-conditioning Engineering from Pukyong National University, Busan, Korea. She works in Pukyong National University. Her research interest is mathematical modeling and optimal control for vapor compression refrigeration system.
Ki-Hak Hong received the B.E. in Refrigeration and Air-Conditioning Engineering from Pukyong National University, Busan, Korea. He is currently pursuing his master’s degree at Pukyong National University. His research interests are dynamic modeling and robust control for refrigeration system.
Rights and permissions
About this article
Cite this article
Jeong, SK., Lee, DB. & Hong, KH. Comparison of system performance on hot-gas bypass and variable speed compressor in an oil cooler for machine tools. J Mech Sci Technol 28, 721–727 (2014). https://doi.org/10.1007/s12206-013-1136-1
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12206-013-1136-1