Inverse Methods for Design and Control of Thermal Systems: Validation in a 2-D Visible Light Enclosure

Abstract

Inverse methods have recently been introduced and applied to the design and control of thermal systems, particularly to systems where radiative transfer is the main heat transfer mode. The results of the steady state design of a representative radiative system using inverse methods have been experimentally validated on a modeled physical system. Few experiments have been developed to validate radiative transfer calculations even in simple systems. This is because it is difficult to separate other modes of energy transfer from radiative transfer, and, in transient systems, thermal inertia effects often mask the precise measurement of radiative effects. The present study is a continuation of the earlier validation work, performed to further study and eventually validate the inverse design and control methods by modeling and designing a simplified physical thermal system. A main focus of the present study is to exploit the similarities between thermal radiative systems lacking thermal inertia and visible light systems. Because of the absence of thermal capacitance, the response of a visible light system depends intrinsically on the state of the light source. The present study considers the inverse design of a newly developed experimental apparatus designed to simulate a low capacitance, two-dimensional radiative enclosure. The apparatus relies on the direct analogy between visible light and radiative heat transfer in a cold, low capacitance system where conduction and convection are suppressed. The system is designed so that both steady state and transient conditions can be achieved. The enclosure is equipped with individually controlled low-power lamps as the source of radiant flux, and these mimic radiant heaters in a real system. The design surface is instrumented with light detectors so that the intensity of the illumination on this surface can be quantified and eventually compared with the design goal. This paper illustrates the characteristics and capabilities of the experimental setup, along with the validity of inverse methods for steady state inverse design of the enclosure to achieve specified conditions on the design surface and sequent validation of the results on the experimental system.