Fengwu Bai

The selection and assemblage of approximation functions and disposal of its singularity in axisymmetric DRBEM for heat transfer problems

Abstract In this paper, a group of approximation functions f with summed form are developed in the dual reciprocity boundary element method (DRBEM) based on the three-dimensional Poisson-type equation whose right-hand side is radial basis function. The singularity on symmetrical axis of the function f is eliminated by integral averaging and selecting different assemblage of the functions f on the basis of the different characteristic of computational domains. By solving the transient heat conduction problems in solid cylinder and sphere, the laminar convective heat transfer problem in tube and the solid–liquid phase change process of sphere, the feasibility of present selecting and assembling function f and its singularity processing are well proved.

The Specific Heat at Constant Pressure in the Latent Functional Fluid with Microencapsulated Phase-Change Materials

The specific heat at constant pressure is an important thermophysical parameter in the latent functional fluid with microencapsulated phase-change materials. It expresses the special function of the functional fluid. However, a uniform and correct formula to calculate the specific heat has been lacking. In this paper, on the basis of the theorem of thermodynamics and two-phase flow, the relation between the specific heat of the mixture and every phase, and the latent heat, the volume fraction, the mass fraction of every phase, and other thermophysical parameters is theoretically deduced by a thermodynamic derivative method. The effect of different physical parameters on the specific heat of the mixture is further discussed.

Numerical Simulation of Flow and Heat Transfer Process of Solid Media Thermal Energy Storage Unit

A sensible heat storage unit with a hollow cylinder of solid media was studied semi-analytically. The heat transfer process in the heat storage medium was solved by using an integral approximate method. The forced convective heat transfer inside the tube was coupled with the heat conduction in the heat storage media. This method enables evaluation of the performance of the storage device in transient conditions. For the operation considerations, only fully developed turbulent flow is calculated. Different heat transfer fluids such as water and air with variable thermal properties dependent of temperature are used in calculations. Concrete and cast iron are selected as heat storage materials. From the simulation results presented in this paper, the thermal conductivity, the distance between the tubes, heat transfer fluid, tube size and flow velocity are the key parameters for such heat storage unit design.

Thermal analysis of honeycomb ceramic air receiver

This study investigated the heat transfer between air flow and honeycomb ceramic air receiver. A one-dimensional model of the receiver was established considering the distribution of the solar radiation within the channel and the radiative heat transfer between the inner surfaces. The sensitivity studies had been done to explore the influences of the absorber geometric parameters, the incident solar radiation and the air flow rate on the receiver steady-state thermal efficiency and outlet air temperature. The minimal absorber length was analyzed to ensure high thermal efficiency, which is significant for the receiver design and optimization.

Experimental and numerical investigation of a packed-bed thermal energy storage device

This paper presents a pilot-scale setup built to study a packed bed thermal energy storage device based on ceramic balls randomly poured into a cylindrical tank while using air as heat transfer fluid. Temperature distribution of ceramic balls throughout the packed bed is investigated both experimentally and numerically. Method of characteristic is adopted to improve the numerical computing efficiency, and mesh independence is verified to guarantee the accuracy of numerical solutions and the economy of computing time cost at the same time. Temperature in tests is as high as over 600 °C, and modeling prediction shows good agreements with experimental results under various testing conditions when heat loss is included and thermal properties of air are considered as temperature dependent.

Analysis of the turbulent heat transfer in solar power tower molten salt receiver tube

Central Receiver System (CRS) with molten salt (MS) technology represents the most cost effective and leading candidate technology for electricity generation for stand-alone Solar Power Plants. But MS has a high freezing point, and the tube alloy also can not stand long time with high temperature in MS circumstances. Tube freezing, leaking and salt decomposing are very likely to happen during the operation, especially under the unstable and non-uniform solar incidence flux. The conventional heat transfer correlations are not well available to deal with the MS receiver, for the heat flux are inconstant and non-uniform and only heat one side of the receiver tube, and the thermal properties of MS are also changed with temperature. By using a commercial CFD software FLUENT, this paper presents the results and analysis of the heat transfer in MS receiver tube with steady non-uniform heat flux around the circumference. This results will do some help to the 100kW MS receiver design and fabrication in the next step in DAHAN SPT project.