Parametric design and evaluation of parabolic solar collectors for residence application

Abstract

This thesis deals with a performance study of a parabolic solar collector for residence application. Parabolic trough solar collectors (PTSC) are employed for a variety of applications including steam generation and hot water generation. This thesis deals with the experimental results designed and developed for hot water generation for a residence in Serres, Greece. The new collector performance has been tested according to ASHRAE Standard 93 (2010). The performance of a new PTC hot water generation system with a well insulated hot water storage tank is investigated by a series of extensive tests. Thus we present a prototype of a parabolic trough collector with a 900 and concentration ratio of 3.15 for space heating and domestic hot water (DHW) applications. The design and the performance optimization of a solar collector is being investigated using the most common materials for the collector, as well as structural components for the design, focused on an optimum balance of performance and cost. The development of low cost PTC plays a decisive role in the appliance of this technology. From Iron and stainless steel is consisted of the supportive structure. Iron is used in the external shell of the trough and the support structure while stainless steel was used in the reflective surface material. The receiver is a copper tube. The main features of this solar collector, except the cost-effectiveness, is the low weight, great mechanical resistance and easy to manufacture. Also the thesis presents the theoretical analysis of the relation between the geometric parameters of the parabolic solar collector and the optimum performance of the photo-thermal conversion happening in the PTC. From these analysis results, are determined the geometric characteristics to collect the entire reflected solar beam from the reflector to the receiver and then to the heat transfer fluid (water).The investigation will study, test and improve the thermal performance of solar collector which is critically important for the end users in order to ensure the efficiency of the system. The results of the thermal performance showed that the optical efficiency of the trough of the PTSC collector is 58% and the corresponding heat loss coefficient 3.6 W/m²K. The results of the heat loss coefficients are valid for temperature intervals between 20°C and 57°C. Aim of this thesis is to simulate and study the physical characteristics of the flow field in the tube solar collector. In order to achieve a three-dimensional model at an ANSYS code is used. Numerical solution is carried for the absorber tube using Computational Fluid Dynamics Modeling in (CFX) had been taken for in a fully developed turbulent flow. Two different scenarios have been investigated, one with constant temperature and one with constant heat flux. Results of the flux density, temperature distribution have been collected for the estimation of the local convection heat transfer coefficient. The results were compared with experimental data taken from literature as well as with those which produced from the experiments. From these computational results have been exported correlations of Nusselt number for heat transfer and calculation of the heat transfer coefficient as a function of the conditions in the flow and temperature field inside the solar collector.