Performance Evaluation of a Modified Compound Parabolic Concentrating Collector with Varying Concentration Ratio

Abstract

Thermosyphon based evacuated tube solar collectors have seen exponential growth in the last few decades for domestic hot water applications. The output temperatures of such collectors can be increased by integrating evacuated tube receivers with compound parabolic concentrators (CPCs) to meet many industrial heat loads. This paper presents a new concept of increasing concentration of solar radiation along the length of an evacuated tube receiver coupled with a modified CPC with 52.5° and 38.5° acceptance half-angles at the inlet and outlet sides respectively. The effect of varying concentration ratio in the longitudinal direction is analyzed in terms of increasing heat flux and temperature gradient between the inlet and outlet of the receiver. Monte Carlo ray-tracing analysis confirmed a gradual increase of power density along the length of the receiver paired with the modified CPC. The daily average energy collection by the modified CPC was comparable with that of equal aperture area CPC with a fixed concentration ratio along its length. The experimental results demonstrated about a 15% higher temperature gradient in the case of CPC with a varying concentration ratio as compared to equal aperture area CPC with a fixed concentration ratio single-phase thermosyphon flow.

Additional information

Funding

The authors highly acknowledge and appreciate the financial support of UTP through research grant YUTP (0153-AA-H28) to conduct this research.

Notes on contributors

Javed Akhter

Javed Akhter is a Postgraduate student at the Mechanical Engineering Department, Universiti Teknologi PETRONAS, Malaysia. He is also working as an Assistant Professor at the University of Engineering and Technology Taxila, Rawalpindi, Pakistan, since 2013. His research field covers solar thermal energy systems, non-imaging optical concentrators, heat transfer using nanofluids and solar thermal utilization.

Syed I. Gilani

Syed Ihtsham ul Haq Gilani is working as an Associate Professor at the Mechanical Engineering Department, Universiti Teknologi PETRONAS, Malaysia since 2003. He did a Ph.D. in Mechanical Engineering from the University of Birmingham, UK in 1992. His research interests include solar thermal systems, solar assisted air conditioning systems, solar steaming using power tower or parabolic troughs and energy management system.

Hussain H. Al-Kayiem

Hussain H. Jaafer Al-Kayiem is a Professor at the Mechanical Engineering Department, Universiti Teknologi PETRONAS, Malaysia. He completed a Ph.D. in Mechanical Engineering from the University of Bradford in 1989. His research interests include renewable energies, multi-phase flow, liquid/liquid separation, renewable energies, and thermofluids in plants.

Muzaffar Ali

Muzaffar Ali is working as an Associate Professor at the Department of Energy Engineering, University of Engineering and Technology Taxila, Rawalpindi, Pakistan. His research interests include solar thermal systems design and optimization, HVAC system design and optimization, thermal system modeling and simulation, and sustainable/renewable energy system.