Numerical study on heat transfer performance of vacuum tube solar collector integrated with metal foams

Abstract

Applying vacuum tube solar collector is one effective way to reduce heat loss in solar collection. However, low conductivity of pure water leads to poor heat transfer performance in vacuum tube. In order to enhance heat transfer in tube, a novel vacuum tube solar collector using water as medium and metal foams as filler is presented, which consists of outer glass tube, inner metal tube and metal foam filler. The heating process of vacuum tube with metal foam filler of different structural parameters (porosity in range of 0.8991-0.9546 and PPI of 5, 10 and 20) is numerically studied and local thermal equilibrium model is applied.The temperature distribution of vacuum tube collectors with and without metal foam filler are compared. The impact of porosity and PPI on heat transfer performance is obtained. The results show that metal foams plays a great role in heat transfer enhancement for vacuum tube solar collector. Thermal performance of the novel vacuum tube solar collector is influenced by porosity and PPI of metal foams. Compared with traditional vacuum tube solar collector, the proposed vacuum tube solar collector has better thermal performance and greater potential in solar building integration.