Comparative Numerical Study on Global Heat Transfer Process in Micro-Channel Gas Coolers with Different Structures

Document Type : Regular Article


1 College of Food Science and Technology, Shanghai Ocean University, China

2 Shanghai Professional Technology Service Platform on Cold Chain Equipment Performance and Energy Saving Testing Evaluation, China

3 Shanghai Engineering Research Center of Aquatic Product Processing & Preservation

4 National Experimental Teaching Demonstration Center for Food Science and Engineering (Shanghai Ocean University), China



A numerical simulation of global heat transfer process in three types of micro-channel heat exchangers was investigated in this paper: spiral double-pipe micro-channel heat exchanger (DPHE), cross-plate micro-channel heat exchanger (CPHE), and shell and tube micro-channel heat exchanger (STHE). The inner tubes of all three heat exchangers have a diameter of 1 mm and are charged with CO2 as refrigerant. A detailed analysis of the heat exchanger's global heat transfer process was carried out, which is entirely different for different structures. The heat transfer characteristics of supercritical CO2 were analyzed by considering the operating pressure, the refrigerant mass flux, the cooling water mass flux, and the heat exchanger refrigerant inlet temperature. The relationship between the CO2 heat transfer coefficient (hCO2) and CO2 bulk temperature (Tb,CO2) was analyzed in detail. The pseudo-critical temperature (Tpc) mainly determines where the peak CO2 heat transfer coefficient occurs. When Tb,CO2 < Tpc , the rise in Tb,CO2  is accompanied by an increase in the heat transfer coefficient, which reaches a maximum when Tb,CO2 is a little bit higher than the pseudo-critical temperature, the heat transfer coefficient curve begins to decline as  Tb,CO2 continues to rise. Higher peak heat transfer coefficients can be achieved at higher pressures. Increased refrigerant mass flux always results in larger heat transfer coefficients. The influence of the refrigerant inlet temperature of the heat exchanger in the Tb,CO2 < Tpc  region on the heat transfer coefficient is more significant than expected. In this study, different flow patterns on heat transfer due to different structures were compared. The best heat transfer was achieved using a spiral double-pipe micro-channel heat exchanger (DPHE). It consistently reaches the highest heat transfer and the lowest outlet temperature under the same operating conditions‎.


Bennett, K. and Y. Chen. (2020). One-way coupled three-dimensional fluid-structure interaction analysis of zigzag-channel supercritical CO2 printed circuit heat exchangers. Nuclear Engineering and Design 358, 110434.##
Cai, H. fei, Y. yan Jiang, T. Wang, S. qiang Liang and Y. ming Zhu. (2020a). Experimental investigation on convective heat transfer and pressure drop of supercritical CO2 and water in microtube heat exchangers. International Journal of Heat and Mass Transfer 163, 120443.##
Cai, H. fei, S. qiang Liang, C. hong Guo, T. Wang, Y. ming Zhu and Y. yan Jiang. (2020b). Numerical investigation on heat transfer of supercritical carbon dioxide in the microtube heat exchanger at low reynolds numbers. International Journal of Heat and Mass Transfer 151, 119448.##
Chen, W., Z. Yang, L. Yang and M. K. Chyu. (2018). Numerical investigation of heat transfer and flow characteristics of supercritical CO2 in U-duct. Applied Thermal Engineering 144, 532–539.##
Ehsan, M. M., Z. Guan and A. Y. Klimenko. (2018). A comprehensive review on heat transfer and pressure drop characteristics and correlations with supercritical CO2 under heating and cooling applications. In Renewable and Sustainable Energy Reviews 92, 658–675.##
Eskandari Manjili, F. and M. Cheraghi. (2019). Performance of a new two-stage transcritical CO2 refrigeration cycle with two ejectors. Applied Thermal Engineering 156, 402–409.##
Fronk, B. M. and S. Garimella. (2011). Water-coupled carbon dioxide microchannel gas cooler for heat pump water heaters: Part II - Model development and validation. International Journal of Refrigeration 34(1), 17–28.##
Guo, J., M. Xiang, H. Zhang, X. Huai, K. Cheng and X. Cui. (2019). Thermal-hydraulic characteristics of supercritical pressure CO2 in vertical tubes under cooling and heating conditions. Energy 170, 1067–1081.##
Guoqing, S. (2015).  Study on fluid flow and heat transfer in a mini channel tube-in-tube heat exchanger. In Chinese.##
Han, Y., Y. Liu, M. Li and J. Huang. (2012). A review of development of micro-channel heat exchanger applied in air-conditioning system. Energy Procedia 14, 148–153.##
Jiang, P. X., Y. Zhang and R. F. Shi. (2008). Experimental and numerical investigation of convection heat transfer of CO2 at supercritical pressures in a vertical mini-tube. International Journal of Heat and Mass Transfer 51(11–12), 3052–3056.##
Jiang, P. X., Y. Zhang, Y. J. Xu and R. F. Shi. (2008). Experimental and numerical investigation of convection heat transfer of CO2 at supercritical pressures in a vertical tube at low Reynolds numbers. International Journal of Thermal Sciences 47(8), 998–1011.##
Jiang, P. X., Y. Zhang, C. R. Zhao and R. F. Shi. (2008). Convection heat transfer of CO2 at supercritical pressures in a vertical mini tube at relatively low reynolds numbers. Experimental Thermal and Fluid Science 32(8), 1628–1637.##
Katz, A., S. R. Aakre, M. H. Anderson and D. Ranjan. (2021). Experimental investigation of pressure drop and heat transfer in high temperature supercritical CO2 and helium in a printed-circuit heat exchanger. International Journal of Heat and Mass Transfer 171, 121089.##
Kim, M. H. and C. W. Bullard. (2001). Development of a microchannel evaporator model for a CO2 air-conditioning system. Energy 26(10), 931–948.##
Kim, S. G., Y. Lee, Y. Ahn and J. I. Lee. (2016). CFD aided approach to design printed circuit heat exchangers for supercritical CO2 Brayton cycle application. Annals of Nuclear Energy 92, 175–185.##
Lei, X., J. Zhang, L. Gou, Q. Zhang and H. Li. (2019). Experimental study on convection heat transfer of supercritical CO2 in small upward channels. Energy 176, 119–130.##
Li, J., J. Jia, L. Huang and S. Wang. (2017). Experimental and numerical study of an integrated fin and micro-channel gas cooler for a CO2 automotive air-conditioning. Applied Thermal Engineering 116, 636–647.##
Liang, Y., Z. Sun, M. Dong, J. Lu and Z. Yu. (2020). Investigation of a refrigeration system based on combined supercritical CO2 power and transcritical CO2 refrigeration cycles by waste heat recovery of engine. International Journal of Refrigeration 118, 470–482.##
Ma, T., W. X. Chu, X. Y. Xu, Y. T. Chen and Q. W. Wang. (2016). An experimental study on heat transfer between supercritical carbon dioxide and water near the pseudo-critical temperature in a double pipe heat exchanger. International Journal of Heat and Mass Transfer 93, 379–387.##
Nekså, P., H. Rekstad, G. R. Zakeri and P. A. Schiefloe. (1998). CO2-heat pump water heater: Characteristics, system design and experimental results. International Journal of Refrigeration 21(3), 172–179.##
Pan, M., X. Bian, Y. Zhu, Y. Liang, F. Lu and G. Xiao. (2020). Thermodynamic analysis of a combined supercritical CO2 and ejector expansion refrigeration cycle for engine waste heat recovery. Energy Conversion and Management 224, 113373.##
Rigola, J., G. Raush, C. D. Pérez-Segarra and A. Oliva. (2005). Numerical simulation and experimental validation of vapour compression refrigeration systems. Special emphasis on CO2 trans-critical cycles. International Journal of Refrigeration 28(8), 1225–1237.##
Saeed, M., A. S. Berrouk, M. Salman Siddiqui and A. Ali Awais. (2020). Numerical investigation of thermal and hydraulic characteristics of sCO2-water printed circuit heat exchangers with zigzag channels. Energy Conversion and Management 224(August), 113375.##
Sanaye, S., N. Khakpaay, A. Chitsaz, M. Hassan Yahyanejad and M. Zolfaghari. (2020). A comprehensive approach for designing, modeling and optimizing of waste heat recovery cycle and power generation system in a cement plant: A thermo-economic and environmental assessment. Energy Conversion and Management, 205(September 2019), 112353.##
Soloveva, O., S. Solovev and R. Yafizov. (2021). Hydrodynamics and Convective Heat Transfer in Open Cell Foam with Micropores. Transportation Research Procedia 54, 64–68.##
Wang, D., B. Yu, W. Li, J. Shi and J. Chen. (2018). Heating performance evaluation of a CO2 heat pump system for an electrical vehicle at cold ambient temperatures. Applied Thermal Engineering 142(July), 656–664.##
Wang, H. and S. M. Kissick. (2020). Modeling and simulation of a supercritical CO2-liquid sodium compact heat exchanger for sodium-cooled fast reactors. Applied Thermal Engineering 180, 115859.##
Wang, Q., Z. Song, Y. Zheng, Y. Yin, L. Liu, H. Wang and J. Yao. (2019). Coupled convection heat transfer of water in a double pipe heat exchanger at supercritical pressures: An experimental research. Applied Thermal Engineering 159, 113962.##
Xu, R. N., F. Luo and P. X. Jiang. (2015). Experimental research on the turbulent convection heat transfer of supercritical pressure CO2 in a serpentine vertical mini tube. International Journal of Heat and Mass Transfer 91, 552–561.##
Yang, D., J. Xie, J. Lv and J. Wang. (2017). An Experimental and Numerical Study of Helix Tube Gas Cooler for Super-Critical Carbon Dioxide. Journal of Chemical Engineering of Japan 50(12), 900–908.##
Yang, J., B. Yu and J. Chen. (2019). Improved genetic algorithm-based prediction of a CO2 micro-channel gas-cooler against experimental data in automobile air conditioning system. International Journal of Refrigeration 106, 517–525.##
Yang, Z., W. Chen and M. K. Chyu. (2018). Numerical study on the heat transfer enhancement of supercritical CO2 in vertical ribbed tubes. Applied Thermal Engineering 145, 705–715.##
Zhang, S., X. Xu, C. Liu, X. Liu, Z. Ru and C. Dang. (2020). Experimental and numerical comparison of the heat transfer behaviors and buoyancy effects of supercritical CO2 in various heating tubes. International Journal of Heat and Mass Transfer 149.##
Zhang, Y., M. Peng, G. Xia and T. Cong. (2019a). Numerical investigation on local heat transfer characteristics of S-CO2 in horizontal semicircular microtube. Applied Thermal Engineering 154, 380–392.##
Zheng, Y., P. X. Jiang, F. Luo and R. N. Xu. (2019b). Instability during transition to turbulence of supercritical pressure CO2 in a vertical heated serpentine tube. International Journal of Thermal Sciences 145(September 2018), 105976.##
Zhu, Y., Y. Huang, S. Lin, C. Li and P. Jiang. (2019). Study of convection heat transfer of CO2 at supercritical pressures during cooling in fluted tube-in-tube heat exchangers. International Journal of Refrigeration 104, 161–170.##