Abstract
Heat transfer to a turbulent flow of supercritical pressure (SCP) fluids under intense heating conditions is considered. The problem of heat transfer deteriorating under high heat loads and the reasons of its origination are analyzed. The results of hydraulic measurements in a flow and its structure using “two pressure drop” method and sounding technique in the regimes of normal and deteriorated heat transfer are presented. The existed correlations on normal heat transfer are analyzed and assessed as to their accuracy. It is pointed out that all the correlations developed using “old” thermophysical properties existed before implementing IAWPS-97 must be corrected. Respective recommendations on this problem and the new correlation for normal heat transfer are presented.
TopIntroduction
Presently, along with combined-cycle installations, supercritical pressure (SCP) power units constitute the basis of the power engineering of the developed countries. At the initial steam parameters of 25 MPa and 540oC their efficiency is about 43-45% and at 30 MPa and 700oC will reach 48-50%. Regarding these indices, as well as the level of capital investments, nuclear power engineering with the efficiency of electricity generation of about 32-33% is far behind the common thermal power engineering, Due to this reason, a possibility of introducing power cycles with SCP water as a working fluid into nuclear power engineering is widely discussed, Certain scientific and design problems concerning nuclear power plants of new generation are worked out also (see Kirillov, 2001, Pioro, 2007, Gabaraev, 2006).
A success in these affairs to a great extent depends on a thorough knowledge and rational using of a great scientific and engineering basis that was elaborated in XX century. In connection with the new practical tasks the problems of heat transfer in the near-critical region require further studying concerning to application of SCP coolants under concrete conditions of promising technologies and apparatuses.
The authors of this Chapter also conducted certain work on studying SCP-coolant heat transfer, generalizing the experimental data mass, and describing engineering aspects of its application. The results presented in four interconnected publications (Kurganov, 2012, 2013-1, 2013-2, 2014), many problems are analyzed in Kurganov, 2018. This Chapter contains the main scientific conclusions and recommendations that follow from the works conducted.
Key Terms in this Chapter
Thermal Acceleration: Is an increase in local flow velocity due to a considerable decrease in the coolant density in a heated flow.
Normal Heat Transfer: Is the regime, which is qualitatively close to the turbulent flow of a coolant with constant thermophysical properties.
Archimedes (Buoyancy) Forces Effect: Flow distortion due to local decrease in density and increase in thermal-expansion coefficient value.
Two Pressure Drop Technique: The method of experimentally determining flow pressure drop components by comparing pressure drop values at heated and adiabatic sections of channel located in a consecutive order.
Deteriorated Heat Transfer: Is the regime with considerable wall temperature peaks.