An Experimental Study on a Sodium Loop-type Heat Pipe for Thermal Transport from a High-temperature Solar Receiver

Abstract

A loop-type heat pipe was fabricated and tested to transport high-temperature thermal energy from a solar receiver in a CSP application. The purpose of the heat pipe in this study was to transport an 800-W thermal load at 1000 K to a specific energy conversion device 0.5 m in distance from the solar receiver. The container wall and transport lines of the loop-type heat pipe were made of stainless steel 304, and the working fluid was sodium. The evaporator and condenser were disk-type containers with diameters of 122 and 216 mm, respectively, though both had a height of 20 mm. The diameters of the vapor and liquid lines were 12.7 and 9.53 mm, respectively. The total length of the loop was approximately 1.4 m. A pillar structure with a diameter of 43 mm and height of 114 mm was installed in the center region of the condenser to interface with an AMTEC device that had a unique geometry. It was desired that the upper surface of the condenser as well as the whole outer surface of the pillar would have temperatures as close as possible during heat discharge. As one of the unique features in this study, the liquid line was located close to the vapor line for a preheating effect to reduce the frozen-startup time. The influence of the fill charge ratio of the working fluid as well as operating conditions such as the thermal load and the cooling condition in the condenser were analyzed with respect to the performance indices of the heat pipe, including the effective thermal conductance, the thermal resistance, and the maximum temperature difference. The optimum fill charge ratio of the heat pipe was 32% based on the evaporator volume.

Solar Receiver with Integrated Thermal Storage for a Supercritical Carbon Dioxide Power Cycle

“…Brayton's receiver technologies are responsive to the aforementioned specifications, while employing different technology elements tested under previous DOE programs. Alkali metal heat pipe solar absorbers have been analyzed and tested by DOE contractors under the ASCS [9] program, Sandia National Labs, NASA, Argonne National Labs, Los Alamos National Labs [10], and other institutions [11] over a three decade period. Gas-heating solar receivers have likewise received significant attention over past decades for Brayton, Stirling, and indirect cycles, and recently have been identified by the DOE as one of the three likely technology paths towards the next generation receiver for use with high efficiency CSP systems.…”

“…A model is needed that can quickly and accurately calculate these output parameters for various receiver geometries. A finite difference model was created in EES that discretizes one side of one cell in the receiver into 5 nodes in width, and 20 nodes in length [11]. Since the nose sees a significant flux, it too is discretized into 5 nodes radially and 20 nodes in length.…”

Solar Receiver with Integrated Thermal Storage for a Supercritical Carbon Dioxide Power Cycle

“…Brayton's receiver technologies are responsive to the aforementioned specifications, while employing different technology elements tested under previous DOE programs. Alkali metal heat pipe solar absorbers have been analyzed and tested by DOE contractors under the ASCS [9] program, Sandia National Labs, NASA, Argonne National Labs, Los Alamos National Labs [10], and other institutions [11] over a three decade period. Gas-heating solar receivers have likewise received significant attention over past decades for Brayton, Stirling, and indirect cycles, and recently have been identified by the DOE as one of the three likely technology paths towards the next generation receiver for use with high efficiency CSP systems.…”

Overview on recent photovoltaic module cooling methods: advances PVT systems

“…The system had been able to exhibit good temperature uniformity and excellent thermal conductivity. Beforehand, in an investigation conducted by Boo et al [49] on loop heat pipes filled with different ratios of sodium. They concluded that the fill ratio has an effect on thermal resistance, effective thermal conductivity, startup time and as well as isothermal characteristics.…”