Research on pressure drop characteristics of CO 2 flow boiling based on flow pattern in horizontal Minichannel
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ORIGINAL
Research on pressure drop characteristics of CO2 flow boiling based on flow pattern in horizontal Minichannel Zhang Liang 1
&
Jiang Linlin 2 & Liu Jianhua 1 & Yuan Yunxiao 1 & Zhang Jiawen 1
Received: 15 July 2019 / Accepted: 30 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The experimental study of the frictional pressure drop characteristics of flow boiling heat transfer of CO2 in a horizontal minichannel with an inner diameter of Φ1.5 mm was carried out. Experimental conditions: heat flux (7.5 ~ 30 kW•m−2), mass flow rate (50 ~ 600 kg•m−2•s−1), saturation temperature (−40 ~ 0 °C), vapor quality (0 ~ 1). The comparison between the experimental results and theoretical flow pattern diagrams shows that the change of heat flux has little effect on the frictional pressure drop at high vapor quality area, but it has a decisive effect on the dryout and mist flow areas. The mass flow rate is the most important factor affecting the frictional pressure drop which has a decisive effect on the flow pattern experienced during the heat transfer process. The saturation temperature has an important influence on the flow pattern transition characteristics and the friction pressure drop decreases with the increase of saturation temperature. The influence of vapor quality on the frictional pressure drop is mainly caused by the flow pattern change in the minichannel. The flow visualization study shows that the theoretical flow pattern diagram can better reflect the flow pattern of CO2 in the phase-change heat transfer process and the transition trend of flow pattern under different working conditions. Keywords CO2 . Minichannel . Flow boiling . Frictional pressure drop . Flow pattern
Nomenclature Specific heat, J•kg−1•K−1. cp D Hydraulic diameter, m D Hydraulic diameter, m G Mass flow rate, kg•m−2•s−1 g Gravity acceleration, m•s−2 k Thermal conductivity, W•m−1•K−1 L Test section length, m m Mass flux, kg•s−1 h Enthalpy, kJ•kg−1 q Heat flux, W•m−2 T Temperature, °C x Vapor quality ΔP Pressure drop λ Prediction accuracy, % * Zhang Liang [email protected] 1
Refrigeration Technology Institute, University of Shanghai for Science and Technology, Shanghai, People’s Republic of China
2
Nantong Vocational University, Shanghai 200093, People’s Republic of China
MAD RAD
Mean absolute deviation, % Mean relative deviation, %
Greek symbols ρ Density, kg/m3 ε Uncertainty degree σ Surface tension, N/m α Vapor void fraction Subscripts a Acceleration F Frictional pre Preheat sul Subcool tp Two-phase l Liquid phase lv Latent heat leak Leakage heat r refrigeration x Mid-position in Inner out Outer
Heat Mass Transfer
1 Introduction
2 Experimental device and data processing
The minichannel heat exchanger has the advantages of compact structure, large unit volume contact area and small refrigerant filling amount, etc. For the widely used hydrofluorocarbon (HFC) and hydrochlorofluorocarbon (HCFC) refrigerants, the heat transfer coefficient increases significantly with the decrease of the tube diam
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