Izvestiya vuzov. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

Heat transfer intensification in emergency cooling heat exchanger of nuclear power plant using air-water mist flow

9/30/2019 2019 - #03 Nuclear power plants

Abed A.H. Shcheklein S.E. Pakhaluev V.M.

DOI: https://doi.org/10.26583/npe.2019.3.02

UDC: 621.039:532.574

Advanced nuclear power plants are equipped with passive systems for emergency decay heat removal from reactor equipment (PEHRSs) in case of development of accidents accompanied with primary cooling circuit leakage and for transferring heat to the final heat absorber (ambient air). Here, intensity of heat dissipation to air from the heat exchanger outer surface achieved by buoyance induced natural convection is extremely low, which necessitates the need to expand heat conductivity surfaces and to apply different types of heat transfer intensifiers (grooves, ribs and extended surfaces, positioning at higher altitudes, etc.). Intensity of heat removal is also strongly dependent on the ambient air temperature (disposable temperature head).

Construction of nuclear power plants in countries with high ambient temperatures (Iran, Bangladesh, Egypt, Saudi Arabia and others) with characteristic high level of ambient air temperature imposes additional requirements on the expansion of heat exchange surfaces.Results of experimental investigation of intensification of heat exchange by low energy-intensity ultrasound supply of super-small liquid droplets (size ~3 mm) in the cooling air are provided in the present paper. In such case, transfer of heat between the cooled surface and cooling airflow involves the following three physical effects: convection, conductive heat exchange and evaporation of water droplets. The latter two effects weakly depend on the ambient air temperature and ensure active heat removal in any type of situation.

Investigation was performed using high-precision calorimeter with controlled rate of heat supply (between 7800 and 12831 W/m2) imitating heated surface within the range of Reynolds numbers from 2500 to 55000 and liquid (water) flow rates from 23.39 to 111.68 kg/m2·h–1.

he studies demonstrated that presence of finely dispersed water results in significant increase of heat transfer compared with the case of application of purely air-cooling. With fixed heat flow energy efficiency increases with increasing concentration of water reaching the values in excess of 600 W/m2·degree–1, which is 2.8 times higher than for the case of air-cooling. Application of the suggested technology for intensification of heat exchange in dry cooling towers of nuclear and thermal power plants used in the conditions of hot and extreme continental climate is possible subject to further investigation for the purpose of specification of optimal ranges of heat exchange intensification.


  1. Dmitriev S.M., Morozov A.V., Remizov O.V. Passive Core Cooling Systems for Various Types of Nuclear Reactors. N. Novgorod, NGTU Publ., 2013, 77 p. (in Russian).
  2. Zhang Y., Qiu S., Su G., Tian W. Design and transient analyses of emergency passive residual heat removal system of CPR1000. Nuclear Engineering and Design. 2012, v. 242, pp. 247-256.
  3. Maio Vitale Di, Naviglio D., Giannetti A., Manni F. An innovative pool with a passive heat removal system. Energy. 2012, v. 45(1), pp. 296-303.
  4. Mousavian S., D’Auria F., Salehi M. Analysis of natural circulation phenomena in VVER-1000. Nuclear Engineering and Design. 2004, v. 229(1), pp.25-46.
  5. Andrushechko S.A., Afrov A.M., Vasilyev B.Yu., Generalov V.N., Kosourov K.B., Semchenkov Yu.M., Ukraintsev V.F. NPP with VVER%1000 TYPE reactor. From Physical Basics of Exploitation to Evolution Design. Moscow. Logos Publ., 2010, 604 p. (in Russian).
  6. Zvirin Yu. A review of natural circulation loops in PWR and other systems. Nucl. Eng. Design. 1981, v. 67, pp. 203-225.
  7. Safety Assessment Report. Novovoronezh NPP%2 Power Unit No. 1. Chapter 12. Safety Systems. Moscow. JSC Atomenergoproect Publ., 2013, 240 p. (in Russian).
  8. Galiev K., Yaurov S., Goncharov Y., Volnov A. Experience of commissioning of the V-392M reactor plant passive heat removal system. Nuclear Energy and Technology. 2017, v. 3(4), pp. 291-296.
  9. Li X., Gurgenci H., Guan Z., Sun Y. Experimental study of cold inflow effect on a small natural draft dry cooling tower. Applied Thermal Engineering. 2018, v. 128, pp. 762-771.
  10. Yang L.J., Wu X.P., Du X.Z., Yang Y.P. Dimensional characteristics of wind effects on the performance of indirect dry cooling system with vertically arranged heat exchanger bundles. International Journal of Heat and Mass Transfer. 2013, v. 67, pp. 853-866.
  11. Fahmy M., Nabih H. Impact of ambient air temperature and heat load variation on the performance of air-cooled heat exchangers in propane cycles in LNG plants. – Analytical approach. Energy Convers. Manage. 2016, v. 121, pp. 22-35.
  12. Bhatti M., Savery C. Augmentation of Heat Transfer in a Laminar External Gas Boundary Layer by the Vaporization of Suspended Droplets. Journal of Heat Transfer. 1975, v. 97(2), p. 179.
  13. Wataru N., Heikichi K., Shigeki H. Heat transfer from tube banks to air/water mist flow. International Journal of Heat and Mass Transfer. 1988, v. 31(2), pp. 449-460.
  14. Wang T., Dhanasekaran T. Calibration of a Computational Model to Predict Mist/Steam Impinging Jets Cooling With an Application to Gas Turbine Blades. Journal of Heat Transfer. 2010, v. 132(12), pp. 122201.
  15. Hayashi Y., Takimoto A., Matsuda O. Heat transfer from tubes in mist flows. Experimental Heat Transfer. 1991, v. 4(4), pp. 291-308.
  16. Hayashi Y., Takimoto A., Matsuda O., Kitagawa T. Study on Mist Cooling for Heat Exchanger: Development of High-Performance Mist-Cooled Heat Transfer Tubes. JSME International Journal. Ser. 2, Fluids Engineering, Heat Transfer, Power, Combustion, Thermophysical Properties. 1990, v. 33(2), pp. 333-339.
  17. Huang X.G., Yang Y.H., Hu P. Experimental study of falling film evaporation in large scale rectangular channel. Annals of Nuclear Energy. 2015, v. 76, pp. 237-242.
  18. Kudo T., Sekiguchi K., Sankoda K., Namiki N., Nii S. Effect of ultrasonic frequency on size distributions of nanosized mist generated by ultrasonic atomization. Ultrasonics Sonochemistry. 2017, v. 37, pp. 16-22.
  19. Allais I., Alvarez G., Flick D. Modeling cooling kinetics of a stack of spheres during mist chilling. Journal of Food Engineering. 2006, v. 72(2), pp. 197-209.
  20. Allais I., Alvarez G. Analysis of heat transfer during mist chilling of a packed bed of spheres simulating foodstuffs. Journal of Food Engineering. 2001, v. 49(1), pp. 37-47.

nuclear power plants particulate cooling air-water mist water concentration heat exchange intensification