This paper presents the effect of artificial roughness on the absorber plate for the double pass solar air heater duct. The roughness used on the absorber plate is of zig-zag square shape protrusions. It is observed that the protrusions on the one side of the absorber plate will form dimples on its other side. So there will be combined effect of protrusions and dimples on the heat transfer characteristics of the double pass solar heater.
Thermal and thermo hydraulic performance of the double pass solar air heater have been investigated for Reynolds number ranges of 6000-18000, for fixed values of relative longway length (L/e), relative shortway length (S/e), relative roughness height (e/) and aspect ratio of 25, 21.875, 0.03 and 10 respectively. Overall heat transfer coefficient of the system has also been evaluated and compared with the smooth duct.
Table of Contents
1. Introduction
2. Experimental Set-up
3. Results & Discussions
3.1. Variation of heat transfer coefficient with mass flow rate.
3.2. Variation of overall heat transfer coefficient with mass flow rate.
3.3. Variation of Thermal Efficiency with mass flow rate.
3.4. Variation of Thermohydraulic efficiency with mass flow rate.
4. Conclusion
Research Objective and Scope
The primary objective of this study is to conduct an experimental investigation into the heat transfer characteristics and thermal performance of a double pass solar air heater (DPSAH) duct featuring a zig-zag square shape protruded absorber plate, compared against a smooth duct system.
- Performance analysis of DPSAH with artificial roughness.
- Evaluation of overall heat transfer coefficient.
- Determination of thermal and thermohydraulic efficiency.
- Experimental comparison between roughened and smooth absorber plates.
- Impact analysis of mass flow rate variations (Reynolds number 6000-18000).
Excerpt from the Book
3. Results & Discussions
Experimental data of heat transfer and pressure drop in the roughened duct as a function of system and operating parameters have been reported and discussed in the present section.
3.1. Variation of heat transfer coefficient with mass flow rate.
Fig.5 gives the variation of heat transfer coefficient of (upper and lower channel of the duct) with mass flow rate. It is observed that heat transfer coefficient of both roughened and smooth absorber plate increases with increase in mass flow rate. It is observed that the heat transfer coefficient of both roughened and duct in the upper channel is more as compared to the lower channel. Heat transfer coefficient of zig-zag square shape roughened duct is more as compared to the DPSAH with smooth duct.
Chapter Summaries
1. Introduction: Outlines the necessity of enhancing heat transfer in solar air heaters and justifies the use of artificial roughness as a performance improvement technique.
2. Experimental Set-up: Describes the physical design of the test rig, including dimensions, measurement instrumentation, and the configuration of the zig-zag square shape protruded absorber plate.
3. Results & Discussions: Presents experimental data and graphical analyses regarding the effects of mass flow rate on heat transfer coefficients and overall system efficiencies.
3.1. Variation of heat transfer coefficient with mass flow rate.: Details the observation that higher mass flow rates lead to increased heat transfer in both the upper and lower channels.
3.2. Variation of overall heat transfer coefficient with mass flow rate.: Highlights that the roughened plate design provides a 62.5% improvement in the overall heat transfer coefficient compared to smooth ducts.
3.3. Variation of Thermal Efficiency with mass flow rate.: Discusses the positive correlation between mass flow rate and thermal efficiency, noting a 30.95% increase for the roughened duct.
3.4. Variation of Thermohydraulic efficiency with mass flow rate.: Analyzes the efficiency gains in thermohydraulic performance, which are found to be 29.41% higher in the proposed design.
4. Conclusion: Summarizes the study's findings, confirming that the zig-zag square shape protrusions significantly enhance the thermal and hydraulic performance of the DPSAH.
Keywords
Double pass solar air heater, Overall heat transfer coefficient, Thermal efficiency, Thermohydraulic efficiency, Artificial roughness, Zig-zag square protrusion, Reynolds number, Absorber plate, Solar energy, Heat transfer enhancement, Duct flow, Pressure drop, Experimental validation.
Frequently Asked Questions
What is the core focus of this research?
The research focuses on investigating how artificial roughness, specifically in the form of zig-zag square shape protrusions on an absorber plate, impacts the performance of a double pass solar air heater (DPSAH).
What are the central themes discussed?
The study centers on heat transfer characteristics, pressure drop analysis, and the resulting thermal and thermohydraulic efficiencies of solar air heater systems.
What is the primary objective of the work?
The goal is to experimentally determine whether the zig-zag square shape protrusion design improves thermal performance and heat transfer coefficients compared to conventional smooth duct systems.
Which scientific method is utilized?
The authors utilize an experimental approach, constructing a test rig, measuring variables like mass flow rate and temperature, and applying empirical relationships for data reduction.
What is covered in the main body?
The main body covers the experimental design, the mathematical models used for data reduction, and a detailed analysis of results regarding heat transfer coefficient and efficiency variations.
Which keywords characterize the work?
Key terms include DPSAH, Overall heat transfer coefficient, Thermal efficiency, Artificial roughness, and Zig-zag square protrusion.
How much does the zig-zag design improve overall heat transfer?
The study reports an overall heat transfer coefficient improvement of 62.5% for the roughened plate compared to a smooth duct.
What operating range was investigated?
The performance was investigated for a Reynolds number range of 6000 to 18000.
Why are dimples mentioned in the abstract?
The protrusions on one side of the absorber plate create dimples on the other side, creating a combined effect that influences the overall heat transfer characteristics.
- Quote paper
- Barjinder Singh Gill (Author), Brij Bhushan (Author), Tarun Mahajan (Author), 2016, Performance investigation of double pass solar air heater duct having zig-zag square shape protruded absorber plate, Munich, GRIN Verlag, https://www.grin.com/document/338381
