Minimum entropy generation due to heat transfer and fluid friction in a parabolic trough receiver with non-uniform heat flux at different rim angles and concentration ratios

Abstract

In this paper, Monte Carlo ray-tracing and computational fluid dynamics are used to numerically investigate the minimum entropy generation due to heat transfer and fluid friction in a parabolic trough receiver. The analysis was carried out for rim angles in the range 40 o -120 o , concentration ratios in the range 57-143, Reynolds numbers in the range 1.02×10 4 -1.36 ×10 6 and fluid temperatures in the range 350 -650K. Results show existence of an optimal Reynolds number at any given combination of fluid temperature, concentration ratio and rim angle for which the total entropy generation is a minimum. The total entropy generation was found to increase as the rim angle reduced, concentration ratio increased and fluid temperature reduced. The high entropy generation rates at low rim angles are mainly due to high peak temperatures in the absorber tube at these low rim angles. Keywords:

Thermal performance and entropy generation analysis of a high concentration ratio parabolic trough solar collector with Cu-Therminol®VP-1 nanofluid

“…The realistic heat flux profile on the receiver's absorber tube is non-uniform in the tube's circumferential direction [11,14].…”

“…As the concentration ratios increase, it can be expected that the receiver thermal loss and heat transfer irreversibilities will increase due to the high temperatures and temperature gradients at these high concentration ratios [9][10][11]. To improve the thermal performance of the receiver as the concentration ratios increase, heat transfer enhancement will play a significant role.…”

Influence of optical errors on the thermal and thermodynamic performance of a solar parabolic trough receiver

“…Studies on the thermal performance of parabolic trough receivers have shown that the heat flux distribution on the receiver has a notable effect on the receiver's thermal and thermodynamic performance (Mwesigye et al, 2014b, He et al, 2011, Lu et al, 2013. The heat flux distribution is also expected to affect the temperature distribution in the receiver's absorber tube.…”

“…In another study, Jeter (1987) showed analytically the computation of the intercept factor and optical efficiency of parabolic trough concentrators. Other authors have used Monte Carlo ray tracing to determine heat flux distribution on a receiver tube of a parabolic trough system and subsequently analysed the thermal performance of the system (He et al, 2011, Cheng et al, 2012, Mwesigye et al, 2014b, Xiao et al, 2014. In these studies and some other studies available in literature, the detailed influence of optical errors on the thermal and thermodynamic performance of the parabolic trough system is not presented.…”

Multi-objective and thermodynamic optimisation of a parabolic trough receiver with perforated plate inserts

“…As such, improved heat transfer performance will be essential to minimise absorber tube temperature gradients as well as improve the performance and reliability of the receiver at these high concentration ratios. More still, an increase in concentration ratios leads to increased entropy generation rates due to the increased finite temperature differences as concentration ratios increase [8,9]. As such, heat transfer enhancement can also act to minimise the entropy generation in the receiver.…”