Abstract

This document describes the development of a thermal model to explain the behavior of a solar concentration cooker. The model is presented in terms of a coupled system consisting of three ordinary, differential non-lineal equations used to calculate average temperatures of the surface of the reflectors, the surface of the container, and the liquid placed inside the container. Numerical results compared to measurements from experimental tests show that good concordance was obtained. A study of variation was conducted using some of the design parameters of the solar cooker to estimate standard cooking power and thermal efficiency. We conclude that the parameter ‘emittance of selective absorbent film’ on the surface of the cooking pot exerts the greatest influence on the thermal properties assessed.

Abstract

Abstract

Mathematical models for the simulation of the thermal evolution of roller-compacted concrete (RCC) dams during construction constitute an important tool for preventing excessive temperature rise, which may lead to cracking and losses of functionality. Here, we present a framework for the simulation of the thermal process. We define the boundary conditions of the problem using a careful description that incorporates the main heat exchange mechanisms. We adopt both a non-adiabatic and an adiabatic heat generation model for the simulation of the cement hydration. Our numerical framework lets us study the effect of the adopted heat generation model on the thermal field. Moreover, we study the influence of the weather conditions on the evolution of the hydration, and on the starting date of construction. Our simulations have shown that the hydration model has an important influence over the temperature field during the construction and the heat generation rate. Moreover, the hydration process and the temperature evolution are driven by the weather conditions. Once the next lift is cast, its thermal insulation effect makes the hydration take place under quasi-adiabatic conditions. As expected, dams built in cold months are prone to dissipate more heat than those built in warm seasons.