Three-dimensional analysis and numerical optimization of combined natural convection and radiation heat loss in solar cavity receiver with plate fins insert

The numerical study and optimization of combined laminar natural convection and surface radiation heat transfer in solar cavity receiver with plate fins is presented in this paper. Minimizing heat loss in cavity receivers is seen as an effective way to enhance the thermal performance and the use of plate fins has been proposed as a low cost means to minimize heat loss. Firstly, the influence of operating temperature, emissivity of the surface, orientation and the geometric parameters on the total heat loss from the receiver was investigated. It was observed that convective heat loss is largely affected by the angle of inclination of the receiver, the presence of fins and the number of fins in the receiver. As for the radiation heat loss it was observed that it is mainly influenced by the properties of the cavity receiver surface. The radiation heat loss was found to be constant at all the angles of the receiver. Significant reduction in natural convection heat loss from the cavity receiver was accomplished by using the plate fins whereas radiation heat loss was marginally reduced by about 5%. Secondly, the optimization was conducted to obtain the optimal fin geometry and lastly, the overall thermal efficiency of the receiver was presented at different operating temperatures. The overall cavity efficiency marginally increased by approximately 2% with the insertion of fin plates although the convective heat loss was suppressed by about 20%. This is due to the fact that radiation heat loss dominates at high operating temperatures compared to convective heat loss.National Research Foundation and University of Pretoriahttp://www.elsevier.com/locate/enconman2016-09-30hb201

Numerical modelling and optimisation of natural convection heat loss suppression in a solar cavity receiver with plate fins

This study details the numerical modelling and optimization of natural convection heat suppression in a solar cavity receiver with plate fins. The use of plate fins attached to the inner aperture surface is presented as a possible low cost means of suppressing natural convection heat loss in a cavity receiver. In the first part of the study a three-dimensional numerical model that captures the heat transfer and flow processes in the cavity receiver is analyzed, and the possibilities of optimization were then established. The model is laminar in the range of Rayleigh number, inclination angle, plate height and thickness considered. In the second part of the study, the geometric parameters considered were optimized using optimization programme with search algorithm. The results indicate that significant reduction on the natural convection heat loss can be achieved from cavity receivers by using plate fins, and an optimal plate fins configuration exit for minimal natural convection heat loss for a given range of Rayleigh number. Reduction of up to a maximum of 20% at 0 receiver inclination was observed. The results obtained provide a novel approach for improving design of cavity receiver for optimal performance.Department of Mechanical and Aeronautical Engineering, University of Pretoria and the National Research Foundation.http://www.elsevier.com/locate/renene2016-02-28hb201

Tensor Polarized Deuteron Capture by the Hydrogen Isotopes

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Tensor Polarized Deuteron Capture by the Hydrogen Isotopes

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

High Magnetic Field ESR in the Haldane Spin Chains NENP and NINO

We present electron spin resonance experiments in the one-dimensional antiferromagnetic S=1 spin chains NENP and NINO in pulsed magnetic fields up to 50T. The measured field dependence of the quantum energy gap for B||b is analyzed using the exact diagonalization method and the density matrix renormalization group method (DMRG). A staggered anisotropy term (-1)^i d(S_i^x S_i^z + S_i^z S_i^x) was considered for the first time in addition to a staggered field term (-1)^i S_i^x B_st. We show that the spin dynamics in high magnetic fields strongly depends on the orthorhombic anisotropy E.Comment: 4 pages, RevTeX, 4 figure

Progress on the Experimental Search for Charge Symmetry Breaking (CSB) in n-p Scattering

This work was supported by the National Science Foundation Grant NSF PHY 81-14339 and by Indiana Universit

An Experimental Test of Charge Symmetry in n-p Scattering

This work was supported by the National Science Foundation Grants NSF PHY 78-22774 A03, NSF PHY 81-14339, and by Indiana Universit