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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Heat Transfer Enhancement in a Parabolic Trough Receiver Using Perforated Conical Inserts

Aggrey Mwesigye
Department of Mechanical and Aeronautical Engineering, University of Pretoria; Ryerson University, 350 Victoria St, Toronto, ON M5B 2K3, Canada

Tunde Bello-Ochende
Department of Mechanical Engineering, University of Cape Town, Cape Town, Private Bag X3, Rondebosch, 7701, South Africa

Josua Petrus Meyer
Department of Mechanical and Aeronautical Engineering, University of Pretoria, Pretoria, Private Bag X20, Hatfield, 0028, South Africa

DOI: 10.1615/IHTC15.sol.009150
pages 7665-7679


KEY WORDS: Solar energy, Heat transfer enhancement, Heat transfer performance, Parabolic trough receiver, Perforated conical inserts, Reynolds number, Temperature gradients

Abstract

The presence of circumferential temperature gradients as well as high peak temperatures in receivers of parabolic trough collector systems significantly affects their performance as well as their durability. As parabolic trough systems with higher concentration ratios become feasible, increased heat transfer performance becomes essential to reduce these circumferential temperature differences and peak temperatures as well as reduce heat transfer irreversibilities. In this paper, heat transfer enhancement in a parabolic trough receiver using perforated conical inserts was numerically investigated. The analysis was carried out for dimensionless insert’s cone angles in the range 0.40-0.90, dimensionless insert spacing in the range 0.06-0.18 and dimensionless insert size in the range 0.45-0.91. The flow was considered fully developed turbulent with Reynolds numbers in the range 1.02×104 ???? Re ???? 7.38 × 105. The heat transfer fluid temperatures used were 400 K, 500 K, 600 K and 650 K. The numerical solution was obtained using the finite volume method and the realizable k-???? model for turbulence modeling. From the study, the use of perforated conical inserts in the receiver’s absorber tube increased the heat transfer performance in the range 5 - 124% with fluid friction penalty in the range 1.36 – 69.00 times compared with a receiver having a plain absorber tube. The thermal enhancement factors based on constant power comparison with a plain tube in the range 0.53 – 1.14 were obtained. Correlations for heat transfer and fluid friction were also developed and presented.

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