https://orcid.org/0000-0001-9160-9388
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ABSTRACT
A small-scale solar parabolic trough collector system coupled with a jacketed vessel was designed and evaluated for its performance and quality of the products manufactured in it. The prototype having a 7.026 m2 aperture and 88.38° rim angle was installed in Mehsana, Gujarat, India. The study was conducted in May–June 2022 at different flow rates of sigma therm-k. The useful heat rate ranged from 567.82 W to 861.25 W. The daily average thermal efficiency was obtained in the range of 9.81–14.61% and maximum thermal efficiency achieved during the milk trials was 31.51%. Similarly, maximum absorber temperature achieved during stagnation was 193.4°C and during absorber fluid flow condition was 146.5°C. The maximum convective heat transfer coefficient of 49.5 W/m2K was calculated at Reynold number 1822 and Nusselt number 24.12. It was found that the quality parameters of manufactured milk products were at par with domestic food safety standards. Direct normal irradiance was found to be the most influencing factor followed by the initial milk load. The present system is a potential substitute for various small-scale Indian traditional heat-desiccated milk products, where higher thermal efficiency is not the primary requirement and emphasis is more on the importance of ease of operation.
Nomenclature
| W | = | Width, m |
| f | = | focal distance, m |
| L | = | trough length, m |
| A | = | area, m2 |
| C | = | concentration ratio |
| D | = | diameter, m |
| t | = | thickness |
| Cp | = | specific heat capacity, kJ/kg K |
| Gb | = | solar beam radiation, W/m2 |
| h | = | convective heat transfer coefficient, W/m2K |
| k | = | thermal conductivity, W/m K |
| m | = | mass flow rate, kg/s |
| Re | = | Reynold number |
| Nu | = | Nusselt number |
| Pr | = | Prandtl number |
| Q | = | heat flux, W |
| T | = | temperature, °C |
| V | = | volumetric flow rate, m3/s |
| V | = | velocity, m/s |
| N | = | motor shaft rotational speed, rpm |
| U | = | overall heat transfer coefficient, W/m2K |
| Greek Symbols | = | |
| ϕ | = | rim angle |
| η | = | efficiency |
| ρ | = | density, kg/m3 |
| μ | = | dynamic viscosity, Pa s |
| ν | = | kinematic viscosity, m2/s |
| ε | = | emittance |
| ρm | = | reflectivity of mirror |
| α | = | absorptivity |
| τ | = | transmittivity |
| Subscripts and superscripts | = | |
| a | = | aperture |
| eff | = | effective |
| rim | = | rim |
| i | = | inner |
| o | = | outer |
| sur | = | absorber surface |
| avg | = | average |
| t | = | tube |
| exp | = | experimental |
| amb | = | ambient |
| HTF | = | heat transfer fluid |
| j | = | jacket |
| m | = | milk |
| in | = | inlet |
| out | = | outlet |
| th | = | thermal |
| abs | = | absorber |
| u | = | useful |
| f | = | fluid |
| b | = | bulk |
| Abbreviations | = | |
| TIDP | = | traditional Indian milk (dairy) product |
| SPTC | = | solar parabolic trough collector |
| PTC | = | parabolic trough collector |
| HTF | = | heat transfer fluid |
| LPM | = | liter per minute |
| DNI | = | direct normal irradiance |
| M.S. | = | mild steel |
| S.S. | = | stainless steel |
| AISI | = | American Iron and Steel Institute |
| VFD | = | variable frequency drive |
| Hz | = | hertz |
| PTFE | = | polytetrafluoroethylene |
| RTD | = | resistance temperature detector |
| PT-100 | = | platinum resistance temperature detector |
| TT | = | temperature transducer |
Acknowledgements
Himanshu R. Patel would like to thank “Dudhsagar Research and Development Association, Dudhsagar Dairy” for its financial support in present research study.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Additional information
Funding
Notes on contributors
Himanshu R. Patel
Himanshu R. Patel, a Ph.D. student at Ganpat University’s Faculty of Engineering and Technology, specializes in solar thermal energy conversion technology. Concurrently, he serves as an Assistant Professor in the Dairy Engineering Department at Mansinhbhai Institute of Dairy and Food Technology, Dudhsagar Dairy Campus, Mehsana, Gujarat, India. His research centers on energy conversion, conservation, and sustainable development through the application of solar energy.
Vikram B. Patel
Dr. Vikram B. Patel, Professor and Head of Mechanical Engineering at L.D. College of Engineering, brings 25 years of academic and 5 years of industrial experience. With extensive contributions as Board of Study chairman, academic council member, associate dean, and governing council member across various universities, he has guided over 32 PG dissertations and four Ph.D. students. Dr. Patel’s expertise spans manufacturing, material science, and solar energy. Notably, he has organized 10+ faculty development programs, seminars, and conferences.