Thermal Analysis Of Nuclear Reactors

In this thesis the flow and heat transfer characteristics of the nuclear reactor were studied theoretically and experimentally. It contains as follows:Fuel rod steady state and unsteady state heat conductions are treated from both analytical and numerical view points convection heat transfer without phase change and with phase change are both treated experimentally, flow in natural convection loops is treated experimentally and analytically. Studies on flow and heat transfer characteristics of nuclear reactor were already performed systematically, so this thesis paid attention to the characteristics at " passive concept" conditions: low pressure, low heat flow, low velocity, natural circulation of coolant etc. It has some features as follows:(1) Conduction with internal heat source is the heat transfer model in fuel rods. A new 2-dimensional numerical program is developed by present author by using improved calculation method for steady state and unsteady state heat conduction.An another 2-dimensional numerical program is performed for simulation of microwave ceramic sintering, microwave heating is a perspective method for UO₂ pellets sintering.(2) Convection without phase change can be divided into free convection and forced convection. Free convection heat transfer in vertical annular channel-internal cylinder wall with an uniformheat flux and the external thermally insulated is experimentally studied and also experimentalresearch for an inclined cylinder is carried out.Forced convection heat transfer correlation for transition flow is obtained by experiments.(3) Convection with phase change includes nucleate boiling and critical heat flux. For pool boiling in confined narrow space on experimental work is performed (By using "LHLA" Liquid Heating Intensification Apparatus) the effect of boiling in a narrow confined space on natural convection intensification is proved.For Critical Heat Flux (CHF) on small diameter cylinder some new experimental results are presented and for CHF in a confined space a new correlation is obtained based on existing experimental data.(4) Flow in natural circulation loops have been used recently in nuclear reactors. A theoretical model is presented for the multiple loop thermosyphons under the natural convection boundary condition.It is also investigated in detail experimentally under natural convection boundary condition.