A Review of Heat Pipes: its Types and Applications

This article introduces the paper 'A Review of Heat Pipes: its Types and Applications' published by 'International Journal of Engineering Research & Technology (IJERT)'.

1. Overview:

Title: A Review of Heat Pipes: its Types and Applications
Author: Mr. Chetan Sharma, Mr. Sumeet Sharma, Dr. Dasaroju Gangacharyulu
Publication Year: March-2019
Publishing Journal/Academic Society: International Journal of Engineering Research & Technology (IJERT)
Keywords: Heat pipe; thermosyphon; nanoparticles; thermal resistance; thermal performance.

2. Abstracts or Introduction

Heat pipes are recognized as exceptional heat transfer devices, often termed "superconductors of heat" due to their superior heat transfer and extraction capabilities. The performance of heat pipes is significantly influenced by gravitational and capillary forces, which vary with tilt angle, thereby affecting overall performance. This review paper elucidates the principles of thermosyphons, including their operational mechanisms and the impact of gravity. Furthermore, it provides a comprehensive overview of various heat pipe types, specifically micro heat pipes (M.H.P.), loop heat pipes (L.H.P.), and variable conductance heat pipes (V.C.H.P). The incorporation of nanoparticles into the working fluid is also discussed as a method to reduce thermal resistance and enhance thermal performance.

The evolution of heat management is critical in modern electronics. Heat pipes offer an effective solution for heat dissipation challenges in electronic equipment. Invented by Jacob Perkins in 1936, with the first capillary-driven heat pipe patented by Richard Gaugler in 1945 and rediscovered by George Grover in 1963, heat pipes are highly efficient in heat handling with minimal loss. A heat pipe consists of a sealed container with a wick-lined internal wall and is typically divided into three sections: the evaporator, adiabatic, and condenser sections. In operation, heat applied to the evaporator section causes the working fluid to evaporate, which then travels to the condenser section due to a pressure difference, releasing latent heat. The condensate returns to the evaporator section via capillary action through the wick. While similar to thermosyphons, heat pipes uniquely utilize a wick to facilitate condensate return. Key components include the container material, working fluid, and wick material. Heat pipes find applications in die casting and injection moulding, space systems (satellite isothermalisation), solar water heaters, de-icing, electronic component cooling, and internal combustion engines. Figure 1.1 illustrates a schematic of a heat pipe.

3. Research Background:

Background of the Research Topic:

The increasing prevalence of heat generation in electronic devices necessitates effective heat dissipation solutions to maintain operational efficiency and prevent system failure. Traditional methods of heat management are often insufficient for modern, high-density electronics, driving the need for advanced thermal management technologies. Heat pipes emerge as a promising technology to address these challenges due to their high thermal conductivity and passive operation.

Status of Existing Research:

The concept of heat pipes dates back to the mid-20th century, with significant milestones including early inventions and the rediscovery that highlighted their potential for efficient heat transfer. Existing research has explored various aspects of heat pipe technology, including different designs, working fluids, and applications. Prior studies have investigated the performance of thermosyphons and heat pipes under varying conditions, such as inclination angles and filling ratios [2]. Furthermore, the integration of nanotechnology, specifically nanofluids, into heat pipes has been a focus of recent research to enhance their thermal performance [3, 5, 8, 15, 16]. Applications in diverse fields, from space technology to electronic cooling and renewable energy systems, have been actively explored [7, 9, 10].

Necessity of the Research:

This review is essential to consolidate the current understanding of heat pipe technology, particularly focusing on recent advancements and variations in design and application. Given the continuous evolution of thermal management needs and the ongoing research into enhancing heat pipe performance, a comprehensive review is necessary to provide experts and researchers with an updated overview of the field. This review addresses the working principles, different types, and the impact of nanofluids on heat pipe performance, offering valuable insights for both academic and practical applications in thermal engineering.

4. Research Purpose and Research Questions:

Research Purpose:

The primary purpose of this review paper is to provide a comprehensive overview of heat pipe technology. This includes detailing their fundamental working principles, categorizing and describing the various types of heat pipes available, and exploring their diverse applications across different industries. A significant focus is placed on examining the impact of incorporating nanoparticles into the working fluid to enhance the thermal performance of heat pipes.

Key Research:

This review paper addresses several key research areas within heat pipe technology:

Thermosyphon Operation and Gravity Effects: Analyzing the operational principles of thermosyphons and the influence of gravitational forces on their performance.
Classification of Heat Pipe Types: Providing a detailed discussion of different heat pipe types, including micro heat pipes (M.H.P.), loop heat pipes (L.H.P.), variable conductance heat pipes (V.C.H.P.), and pulsating heat pipes (P.H.P.).
Nanofluid Enhancement: Investigating the effects of adding nanoparticles to the working fluid on the thermal resistance and overall thermal performance of heat pipes.
Applications of Heat Pipes: Reviewing the wide range of applications for heat pipes, including but not limited to die casting, injection moulding, space applications, electronic cooling, and renewable energy systems.

Research Hypotheses:

As a review paper, this study does not explicitly formulate research hypotheses in the traditional sense. However, it implicitly operates under the premise that:

Heat pipes are highly effective heat transfer devices due to their inherent design and operational principles.
The incorporation of nanoparticles into the working fluid can significantly enhance the thermal performance of heat pipes by reducing thermal resistance and improving heat transfer coefficients.
Different types of heat pipes are designed to address specific application requirements and operating conditions, offering versatility in thermal management solutions.

5. Research Methodology

Research Design:

This study employs a literature review design. It systematically examines and synthesizes findings from existing scholarly articles and research papers to provide a comprehensive understanding of heat pipe technology.

Data Collection Method:

The data for this review was collected through an extensive search and examination of published research papers in the field of heat transfer and heat pipe technology. The authors compiled information from various journals and conference proceedings to gather relevant data and findings.

Analysis Method:

The analysis method used is qualitative synthesis. The authors critically reviewed and summarized the findings of the selected papers, categorizing the information based on different aspects of heat pipe technology, such as types, working principles, performance enhancement techniques (e.g., nanofluids), and applications. The analysis focuses on identifying trends, common findings, and variations in the reported research to present a cohesive overview of the current state of knowledge.

Research Subjects and Scope:

The research subjects are heat pipes and related technologies, including thermosyphons and nanofluids in heat pipes. The scope of the review encompasses:

Types of Heat Pipes: Micro Heat Pipes (M.H.P.), Loop Heat Pipes (L.H.P.), Variable Conductance Heat Pipes (V.C.H.P.), Thermosyphons, and Pulsating Heat Pipes (P.H.P.).
Working Fluids: Including conventional fluids and nanofluids.
Performance Parameters: Thermal resistance, heat transfer coefficient, thermal efficiency, and operational limits.
Applications: Die casting, injection moulding, space applications, electronic cooling, solar water heaters, and other relevant industrial and technological uses.

6. Main Research Results:

Key Research Results:

The reviewed literature highlights several key findings regarding heat pipe technology:

Enhanced Fin Efficiency using Oscillating Heat Pipes: Nuntaphan et al. [1] demonstrated that replacing solid wire fins with oscillating heat pipes in heat exchangers under forced convection increases heat transfer effectiveness by 10% and fin efficiency by over 5%.
Influence of Inclination Angle and Filling Ratio on Thermosyphons: Noie et al. [2] found that in two-phase closed thermosyphons, condensation heat transfer coefficient and heat transfer rate increase with higher filling ratios. Optimal performance varied with inclination angle, with maximum heat transfer at 30° inclination for 22% and 30% filling ratios, and at 45° for a 15% filling ratio.
Improved Thermal Efficiency with Alumina Nanofluid: Teng et al. [3] reported a 16.8% enhancement in thermal efficiency of heat pipes using alumina nanofluid at a 1% concentration compared to base fluid.
Performance of Copper-Water Heat Pipes: Idrus et al. [4] observed good thermal performance in 10 mm diameter copper-water heat pipes at heat inputs of 70-80 W and inclination angles between 30° and 60°.
Reduced Thermal Resistance with Silver Nanofluid: Kang et al. [5] showed that increasing the concentration and particle size of silver nanoparticles in heat pipes reduces thermal resistance. Heat pipe wall temperature increase was less significant with silver nanofluids compared to pure water under varying heat loads.
Loop Heat Pipe Advantages: Jose et al. [7] emphasized the high efficiency, compact size, high heat flux capability, long-distance energy transfer, wide operational environment range, and low entrainment possibility of loop heat pipes, noting their suitability for applications like thermoelectric generators and electronic cooling.
Enhanced Heat Transfer with Iron Oxide Nanofluid in Thermosyphons: Huminic et al. [8] found that using iron oxide nanofluids in thermosyphons significantly increased heat transfer rates compared to DI-water. A 2% and 5.3% concentration of iron oxide nanoparticles increased heat transfer rates by 19% and 22.2%, respectively, while also reducing thermal resistance.
Pulsating Heat Pipe Characteristics: Han et al. [9] and Hudakorn et al. [11] highlighted pulsating heat pipes (PHPs) for their simple structure, low cost, excellent heat transfer, and flexibility. Hudakorn et al. [11] found that horizontal orientation of PHPs can lead to evaporator dry-out, while vertical orientation may cause flooding.
Effect of Inclination Angle on Thermosyphon Operation: Grooten et al. [12] determined that thermosyphons with R-134a working fluid perform optimally at an 83° inclination angle. Operation limiting heat flux reduces with increasing saturation temperature and decreasing inclination angle.
Water-Copper Nanofluid in Open Loop Pulsating Heat Pipes: Riehl et al. [13] observed improved operation and higher thermal conductance in open loop pulsating heat pipes using water-copper nanofluid compared to pure water.
Performance of n-Pentanol Aqueous Solution in Heat Pipes: Senthilkumar et al. [14] demonstrated superior performance of heat pipes using aqueous solutions of n-pentanol compared to water, attributed to the positive gradient of surface tension with temperature, making it suitable for high heat load applications.
Aluminum Oxide Nanofluid in Sintered Wick Heat Pipes: Moraveji et al. [15] investigated aluminum oxide nanofluids in sintered wick copper heat pipes, showing reduced wall temperature and thermal resistance with nanofluids compared to pure water.
Performance of Screen Mesh Heat Pipes with Alumina Nanofluid: Ghanbarpour et al. [16] found that 5% concentration alumina nanofluid improved screen mesh heat pipe performance under variable heat input, but 10% concentration led to performance deterioration.

Analysis of presented data:

The reviewed data consistently indicates that heat pipes are highly effective heat transfer devices, and their performance can be further enhanced by incorporating nanofluids. Nanoparticles such as alumina, silver, iron oxide, and copper oxide, when added to the working fluid, generally reduce thermal resistance and improve heat transfer characteristics. However, the optimal concentration of nanofluids and operating conditions, such as inclination angle and filling ratio, are critical factors influencing performance. Different types of heat pipes, like loop heat pipes and pulsating heat pipes, offer specific advantages for various applications, highlighting the versatility of heat pipe technology in thermal management.

Figure Name List:

Figure 1.1 A schematic of heat pipe

7. Conclusion:

Summary of Key Findings:

This review concludes that heat pipes are highly effective devices for addressing heat dissipation challenges due to their exceptional thermal conductivity. The thermal performance of heat pipes is demonstrably improved by the addition of nanoparticles to the working fluid, which reduces thermal resistance and enhances heat transfer. The miniaturization capabilities of heat pipes make them particularly suitable for applications with limited volume constraints, solidifying their position as a widely utilized heat dissipation technology.

Academic Significance of the Study:

This study provides a consolidated and updated review of heat pipe technology, synthesizing findings from recent research. It contributes to the academic field by offering a comprehensive resource for researchers and engineers interested in heat transfer and thermal management. The review highlights the advancements in nanofluid-enhanced heat pipes and the diverse range of heat pipe types, serving as a valuable reference for future research and development in this area.

Practical Implications:

The practical implications of this review are significant for engineers and designers in various industries. The findings underscore the benefits of using heat pipes, particularly with nanofluids, for improved thermal management in applications such as die casting, injection moulding, electronics cooling, and space technology. The review informs the selection and implementation of heat pipe technology by highlighting the performance characteristics of different types and the advantages of nanofluid enhancement, leading to more efficient and reliable thermal management solutions.

Limitations of the Study and Areas for Future Research:

As a literature review, this study is limited by the scope and availability of published research. The review provides a general overview but may not delve into the specific details of every study cited. Future research could focus on:

Optimization of Nanofluids: Further investigation into the optimal types, concentrations, and dispersion methods of nanoparticles to maximize heat pipe performance and long-term stability.
Advanced Heat Pipe Designs: Exploring novel heat pipe designs and configurations to enhance performance and expand application areas.
Application-Specific Studies: Conducting more targeted research on the application of heat pipes in specific industries, such as die casting and advanced electronics, to optimize designs for particular thermal management challenges.
Long-Term Performance and Reliability: Investigating the long-term performance and reliability of nanofluid-enhanced heat pipes under various operating conditions to ensure their practical viability in industrial applications.

8. References:

[1] Samana, T., Kiatsiriroat, T. and Nuntaphan, A., 2014. Enhancement of fin efficiency of a solid wire fin by oscillating heat pipe under forced convection. Case Studies in Thermal Engineering, 2, pp.36-41.
[2] Noie, S.H., Sarmasti Emami, M.R. and Khoshnoodi, M., 2007. Effect of inclination angle and filling ratio on thermal performance of a two-phase closed thermosyphon under normal operating conditions. Heat transfer engineering, 28(4), pp.365-371.
[3] Teng, T.P., Hsu, H.G., Mo, H.E. and Chen, C.C., 2010. Thermal efficiency of heat pipe with alumina nanofluid. Journal of alloys and compounds, 504, pp.S380-S384.
[4] Idrus, F., Mohamad, N., Zailani, R., Wisnoe, W. and Abdullah, M.Z., 2014. Thermal performance of a cylindrical heat pipe for different heat inputs and inclination angles. In Applied Mechanics and Materials (Vol. 661, pp. 148-153). Trans Tech Publications.
[5] Kang, S.W., Wei, W.C., Tsai, S.H. and Yang, S.Y., 2006. Experimental investigation of silver nano-fluid on heat pipe thermal performance. Applied Thermal Engineering, 26(17-18), pp.2377-2382.
[6] Plawsky, J., 2017. Wickless heat pipes in microgravity. Physics today, 70(9).
[7] Jose, J. and Baby, R., 2018, August. Recent advances in loop heat pipes: A review. In IOP Conference Series: Materials Science and Engineering (Vol. 396, No. 1, p. 012060). IOP Publishing.
[8] Huminic, G., Huminic, A., Morjan, I. and Dumitrache, F., 2011. Experimental study of the thermal performance of thermosyphon heat pipe using iron oxide nanoparticles. International Journal of Heat and Mass Transfer, 54(1-3), pp.656-661.
[9] Han, X., Wang, X., Zheng, H., Xu, X. and Chen, G., 2016. Review of the development of pulsating heat pipe for heat dissipation. Renewable and Sustainable Energy Reviews, 59, pp.692-709..
[10] Chan, C.W., Siqueiros, E., Ling-Chin, J., Royapoor, M. and Roskilly, A.P., 2015. Heat utilisation technologies: A critical review of heat pipes. Renewable and Sustainable Energy Reviews, 50, pp.615-627.
[11] Hudakorn, T., Terdtoon, P. and Sakulchangsatjatai, P., 2008. Effect of inclination angle on performance limit of a closed-end oscillating heat pipe. American Journal of Engineering and Applied Sciences, 1(3), pp.174-180.
[12] Grooten, M.H.M. and Van Der Geld, C.W.M., 2010. The effect of the angle of inclination on the operation limiting heat flux of long R-134a filled thermosyphons. Journal of heat transfer, 132(5), p.051501.
[13] Riehl, R.R. and dos Santos, N., 2012. Water-copper nanofluid application in an open loop pulsating heat pipe. Applied Thermal Engineering, 42, pp.6-10.
[14] Senthilkumar, R., Vaidyanathan, S. and Sivaraman, B., 2011. Performance investigation of heat pipe using aqueous solution of n-Pentanol with different inclinations. Journal of mechanical science and technology, 25(4), p.923.
[15] Moraveji, M.K. and Razvarz, S., 2012. Experimental investigation of aluminum oxide nanofluid on heat pipe thermal performance. International Communications in Heat and Mass Transfer, 39(9), pp.1444-1448.
[16] Ghanbarpour, M., Nikkam, N., Khodabandeh, R., Toprak, M.S. and Muhammed, M., 2015. Thermal performance of screen mesh heat pipe with Al2O3 nanofluid. Experimental Thermal and Fluid Science, 66, pp.213-220.

9. Copyright:

This material is "Mr. Chetan Sharma, Mr. Sumeet Sharma, Dr. Dasaroju Gangacharyulu"'s paper: Based on "A Review of Heat Pipes: its Types and Applications".
Paper Source: https://www.ijert.org/research/a-review-of-heat-pipes-its-types-and-applications-IJERTV8IS030025.pdf

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