Numerical and experimental investigation of heat transfer in a solar receiver with a variable aperture

Abstract

Variable aperture can assist in maintaining semi-constant temperatures within a receiver's cavity under transient solar loading. An in-house code has been developed to model a receiver and effectively control its components to achieve semi-constant temperatures under transients. The code consists of a full optical analysis performed via the Monte Carlo ray tracing method in addition to a transient two-dimensional heat transfer analysis. The system studied consists of a cavity type solar receiver with 60 mm radius fixed aperture on the cavity body, a variable aperture mechanism mounted on the receiver's flange, and a 7 kW Xenon arc solar simulator. A composite shape consisting of a hemisphere attached to a cylinder is proposed to model the Xenon arc. The in-house code has been experimentally validated through experimental tests for different input currents to the solar simulator, volumetric flow rates, and aperture's radii. The optical analysis was validated based on heat flux measurements, where it had percentage errors of 0.8, 0.5, 1.1, and 3.2% for the peak power, total power, half width, and half power. For the heat transfer model, percentage errors of 3.2, 2.9, and 5.3% at the inlet, center, and outlet sections of the receiver were determined for different flow rates using maximum input current and opening radius. The aperture mechanism was capable of maintaining an exhaust temperature of 250°C based on actual Direct Normal Irradiance data. Results showed that the variable aperture is a promising apparatus even in applications where the maximum temperatures are desired based on an observed optimum radius of 57.5 mm.

High-Quality AB Bilayer Graphene Films by Direct Solar-Thermal Chemical Vapor Deposition

“…A variable aperture mechanism for solar cavity receivers has been reported in prior work, and the solar receiver was modeled through Monte Carlo ray tracing and transient heat transfer analysis of the receiver . The variable aperture was implemented on the solar cavity to regulate temperature and to compensate for the sun’s transient behavior through predictive models and PID control.…”

“…A variable aperture mechanism for solar cavity receivers has been reported in prior work, 42 and the solar receiver was modeled through Monte Carlo ray tracing and transient heat transfer analysis of the receiver. 43 The variable aperture was implemented on the solar cavity to regulate temperature and to compensate for the sun's transient behavior through predictive models and PID control. Additionally, supplemental heat sources using Joule heating can provide precise control of temperature, similar to the studies on plasma-assisted hot wall furnaces 44 and photon-assisted excitation with electron or ion irradiation, 45 where two heat sources are used for graphene synthesis.…”

Analyze of thermal performance and thermal stress and distribution on inverted solar cavity receiver

“…The results include a numerical and experimental analysis and show that the conical cavity is optimal. Abuseada et al [8] studied heat transfer in a solar collector with variable aperture. Optical analysis was performed using Monte Carlo Ray Tracing (MCRT) to simulate the source radiation.…”

Open volumetric air receiver: An innovative application and a major challenge

“…Teng and Xuan (2018) proposed a solar receiver, equipped with the metal coated mirrors, to enhance the outlet temperature of air and the thermal efficiency. Abuseada et al (2019) introduced and analyzed a variable aperture volumetric receiver, to control the receiver temperature, for continually varying heat flux and weather conditions.…”