Numerical simulation of a parabolic trough collector containing a novel parabolic reflector with varying focal length

•A novel parabolic reflector with axially varying focal length is presented.•Performance enhancement with altered reflector is possible.•Axial non-uniform solar flux around the absorber affects the thermal behavior.•Effects are either positive or negative, depending on the reflector orientation. In this study, a novel parabolic reflector for a Parabolic Trough Collector (PTC) is presented. The reflector contains a varying focal length in lengthwise direction while still maintaining a fixed focal line. Due to this geometry, heat flux around the absorber not only varies circumferentially but also axially. A new geometric design parameter is defined which is the ratio of focal length at the ends, and the effects of it on the thermal behavior are investigated numerically. To represent the heat flux realistically a method is presented by employing a custom code to construct the novel reflector in SolTrace (a ray tracing software), and heat flux profile around the absorber is calculated. This flux is applied to a Computational Fluid Dynamics (CFD) model as a source term and simulations are realized. The coupled model is validated with the experimental results regarding the LS-2 module. Besides the parametric analyses about geometric factor, flow rate optimization analyses are also. As a result of the parametric analyses, a 0.21% rise is achieved for thermal efficiency and a 0.63% increase is achieved for net energy gain as a result of the flow rate optimization study.