Reduction of convective losses in solar cavity receivers

Abstract

A detailed radiation heat transfer study of a dish-Stirling receiver: The impact of cavity wall radiation properties and cavity shapes AIP Conference Proceedings 1734, 030017 (2016) Abstract. Two design innovations are reported that can help improve the thermal performance of a solar cavity receiver. These innovations utilise the natural variation of wall temperature inside the cavity and active management of airflow in the vicinity of the receiver. The results of computational fluid dynamics modelling and laboratory-scale experiments suggest that the convective loss from a receiver can be reduced substantially by either mechanism. A further benefit is that both radiative and overall thermal losses from the cavity may be reduced. Further work to assess the performance of such receiver designs under operational conditions is discussed.

Experimental correlation of natural convection losses from a scale-model solar cavity receiver with non-isothermal surface temperature distribution

“…3. Some design aspects of this setup were reported in previous publications (Abbasi-Shavazi et al, 2015;Hughes et al, 2016). The model receiver consists of a stainless steel-316L cylindrical cavity, with internal diameter D of 83 mm and wall thickness of 3 mm.…”

“…Solar cavity receivers find frequent use in paraboloidal dish and central tower systems and can be subjected to large concentrations of solar flux. Efforts to increase the operating efficiency of this CST system component have included research on optimised receiver geometries (Asselineau, 2018;Pye et al, 2016;Shuai et al, 2008), utilising the natural variation of receiver surface temperature to reduce convection and radiation losses (Hughes et al, 2016), use of air curtains (Fang et al, 2019;Zhang et al, 2015), use of protective cowling as part of receiver structure (Cagnoli et al, 2019), use of partial or full windows on receiver aperture (Flesch, Robert et al, 2015;Maag et al, 2011;Uhlig et al, 2014), a variable aperture opening mechanism (Najafabadi et al, 2019;Van den Langenbergh et al, 2015), finned internal surfaces (Ngo et al, 2015) and cavity rotation (Wu, W. et al, 2014).…”

“…Results showing non-isothermal temperature profiles along the cavity side wall form one of the important findings from these studies. Hughes et al (2016) implemented a nonisothermal temperature profile as boundary condition for a numerical study of a cavity receiver and noted that the ensuing heat flux results showed that utilising the naturally-occurring variation of temperature across a cavity surface could present opportunities for the recuperation of losses within a cavity, thereby improving the receiver thermal performance. Lin et al (2018) presented results from a numerical study in which, among other parameters, the presence of a cooled receiver front was investigated in an effort to increase receiver efficiency.…”

Optical and thermal performance of bladed receivers

“…Previous work with cavity cavities [15][16][17][18] and convex central tower receivers [19] has highlighted the potential reduction (~40%) in convective heat loss which can be achieved through the use of air jets and air curtains, especially in no-wind conditions. It is less clear whether active airflow features can cost-effectively reduce heat loss for a receiver during windy conditions.…”

Analysis of Air Curtains for Natural Convection Heat-Loss Mitigation

“…There are several techniques have been proposed to enhance the operating functionality of CSP receivers. Active airflow control in the form of an air curtain is a recognized strategy to minimize convective heat losses from CSP receivers, however, most of the works have been focused on cavity receivers [1,6,7,10,12,17,18]. Air curtain is often restricted to reduce heat transfer between horizontally linked volumes.…”