Experimental investigation on heat transfer characteristics of smooth tube with downward flow

Abstract In the range of pressure from 11.5 to 28 MPa, mass flow rate from 450 to 1550 kg m−2 s−1, and heat flux at inner wall from 50 to 585 kW m−2, an experiment was conducted to investigate the heat transfer characteristics of water in a vertical downward tube. The temperature distribution in the tube wall was obtained. The effects of heat flux on heat transfer coefficient and wall temperature were analyzed and the corresponding empirical correlations were presented. The heat transfer coefficients of vertical downward flow were compared with that of vertical upward flow. The experimental results show that at subcritical and near critical pressure, dryout and departure from nucleate boiling (DNB) can occur in vertical downward tube. With the increase of heat flux, heat transfer deterioration occurs ahead and the peak wall temperature after heat transfer deterioration increases obviously. At supercritical pressure, the wall temperature increases slowly with fluid enthalpy when the bulk temperature is lower than the pseudo-critical temperature and increases considerably when the bulk temperature is higher than the pseudo-critical temperature. In the pseudo-critical enthalpy region, the heat transfer is enhanced.

[1]  J. Thome,et al.  Convective Boiling and Condensation , 1972 .

[2]  D. Che,et al.  Structure and Performance of a 600MWe Supercritical CFB Boiler with Water Cooled Panels , 2009 .

[3]  V. A. Kurganov,et al.  Heat transfer and hydraulic resistance of supercritical-pressure coolants. Part I: Specifics of thermophysical properties of supercritical pressure fluids and turbulent heat transfer under heating conditions in round tubes (state of the art) , 2012 .

[4]  Q. Bi,et al.  Experimental investigation on heat transfer characteristics of high pressures water in a vertical upward annular channel , 2013 .

[5]  Dong-Keun Yang,et al.  Self-compensating characteristic of steam–water mixture at low mass velocity in vertical upward parallel internally ribbed tubes , 2010 .

[6]  Xu Cheng,et al.  Experimental and numerical investigation of turbulent convective heat transfer deterioration of supercritical water in vertical tube , 2012 .

[7]  Afshin J. Ghajar,et al.  Similarities and differences in the flow patterns and void fraction in vertical upward and downward two phase flow , 2012 .

[8]  Dong-Keun Yang,et al.  Experimental investigation on heat transfer characteristics of low mass flux rifled tube with upward flow , 2011 .

[9]  Min-Soo Kim,et al.  Experimental study on the evaporative heat transfer and pressure drop of CO2 flowing upward in vertical smooth and micro-fin tubes with the diameter of 5 mm , 2008 .

[10]  J. Howell,et al.  Convective heat transfer in the entrance region of a vertical tube for water near the thermodynamic critical point , 1999 .

[11]  A. F. Polyakov,et al.  Heat Transfer under Supercritical Pressures , 1991 .

[12]  Emad W. Jassim,et al.  Refrigerant pressure drop in chevron and bumpy style flat plate heat exchangers , 2006 .

[13]  Jin Ho Song,et al.  Heat transfer characteristics of a supercritical fluid flow in a vertical pipe , 2008 .

[14]  Henryk Anglart,et al.  Post-dryout heat transfer to high-pressure water flowing upward in vertical channels with various flow obstacles , 2012 .

[15]  Kefa Cen,et al.  Study on coal combustion characteristics in a W-shaped boiler furnace , 2001 .

[16]  M. Ishii,et al.  Interfacial area transport of vertical upward steam–water two-phase flow in an annular channel at elevated pressures , 2013 .

[17]  J. C. Chen.  Correlation for Boiling Heat Transfer to Saturated Fluids in Convective Flow , 1966 .

[18]  Igor Pioro,et al.  Heat transfer to supercritical fluids flowing in channels—empirical correlations (survey) , 2004 .

[19]  Donghong Zheng,et al.  CFD simulations of hydrodynamic characteristics in a gas-liquid vertical upward slug flow , 2007 .

[20]  Predrag Stojan Hrnjak,et al.  Experiment and visualization on R134a upward flow in the vertical header of microchannel heat exchanger and its effect on distribution , 2013 .

[21]  Dong Yang,et al.  Experimental investigation on heat transfer and frictional characteristics of vertical upward rifled tube in supercritical CFB boiler , 2011 .