Performance Analysis of a Three-Tube Serpentine Receiver in a Parabolic Trough Solar Collector for Domestic Applications

Abstract

This paper investigates the optical and thermal performance of a parabolic trough solar collector integrated with a three-tube serpentine absorber. Driven by the increasing demand for efficient and compact solar thermal systems for domestic applications, this configuration aims to overcome the limitations of traditional single-tube receivers, such as limited residence time and uneven temperature distribution. Employing a combined simulation methodology, including three-dimensional ray tracing in COMSOL Multiphysics for optical simulation and conjugate heat transfer simulations in ANSYS Fluent for fluid temperature analysis, the study evaluates performance under four focal alignment conditions (100%, 90%, 80%, and 70%) to replicate real-world solar tracking variations. Findings indicated that multi-tube serpentine receivers provided significantly better thermal uniformity, higher outlet temperatures, and improved tolerance to optical misalignment compared to the single-tube design, making it a viable option for compact solar preheating systems.

Introduction

Context and Motivation:
The global push toward renewable energy emphasizes solar thermal systems as efficient solutions for domestic low-to-medium temperature needs, like water heating. Parabolic Trough Collectors (PTCs) concentrate sunlight onto absorber tubes to heat fluids. Traditional single straight-tube receivers face efficiency limits in compact domestic systems due to restricted heat transfer surface and fluid residence time.

Design Innovation:
To improve heat transfer, a three-tube serpentine receiver design was developed. This configuration increases surface area and fluid residence time by splitting flow through parallel serpentine paths in a main tube and two preheater tubes. The tubes are copper for high thermal conductivity, arranged to distribute thermal load and enhance convective heat transfer.

System and Simulation Setup:

• The parabolic reflector (1220 mm wide, 1668 mm long) focuses sunlight onto the tubes at a nominal focal length of 606.5 mm.

• The receiver tubes were modeled at four focal distances (100%, 90%, 80%, and 70% of nominal) to simulate real-world misalignment or solar tracking variations.

• Simulations used COMSOL Multiphysics (ray tracing and optical modeling) and ANSYS Fluent (thermal-fluid analysis) with laminar flow, inlet water temperature 300 K, and low velocity.

Optical and Thermal Performance:

• Ray Tracing: Showed that at perfect alignment (100% focal length), most solar rays concentrated on the central tube with less on side tubes. Slight defocusing (90%-80%) spread rays more evenly across all tubes, while significant misalignment (70%) caused a broad, less intense distribution, lowering efficiency but still capturing some solar energy due to multiple tubes.

• Heat Flux Distribution: Heat flux was highest at the center tube under perfect alignment and became more diffuse with misalignment. The serpentine multi-tube design helped capture scattered rays better than a single tube, improving thermal load distribution and reducing losses.

• Thermal-Fluid Analysis: Using spatially varying heat flux as boundary conditions, simulations assessed fluid temperature distribution and outlet temperature, demonstrating enhanced heat transfer and thermal performance of the serpentine multi-tube design under different focal conditions.

Key Takeaway:

The three-tube serpentine receiver design in a parabolic trough collector shows improved thermal performance and robustness against focal misalignment, making it a promising option for efficient, compact domestic solar thermal applications.

Conclusion

This study successfully investigated the optical concentration efficiency and thermal performance of a parabolic trough solar collector integrated with a three-tube serpentine absorber under various focal alignment conditions. The combined modeling approach using Siemens NX, COMSOL Multiphysics, and ANSYS Fluent effectively linked geometric design, solar flux behaviour, and fluid temperature distribution. The ray tracing simulations confirmed that while perfect focal alignment leads to highly concentrated solar flux on the central tube, this configuration also benefits from the spreading of reflected rays under slight misalignment. The three-tube design demonstrated better tolerance to optical misalignment by capturing a broader portion of the distributed rays, thereby improving system resilience. The thermal analysis revealed that the three-tube configuration, particularly at 90% focal alignment, achieved high outlet temperatures in the main tube while effectively preheating the fluid in the adjacent serpentine paths. This indicates that the multi-tube serpentine geometry not only enhances heat transfer but also provides structural and operational robustness under realistic solar tracking errors. The three-tube serpentine receiver offers tangible advantages, including improved fluid residence time, volumetric heating, and distributed flux absorption, contributing to better thermal management. Its efficiency even at suboptimal focus makes it well-suited for real-world conditions where solar incidence varies throughout the day.

References

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Copyright

Copyright © 2025 Mr. Krishna Yadav, Mr. Mrigendra Singh, Ms. Priyanka Malviya. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.