Steam condensation by heat pipes

Advancements in energy-efficient building technologies: An enhanced lee model for precision simulation and optimization of heat pipe applications

This paper addresses the challenges the policymakers face concerning the EU decarbonization and total electrification roadmaps towards the Paris Agreement set forth to solve the global warming problem within the framework of a 100% renewable heating and cooling target. A new holistic model was developed based on the Rational Exergy Management Model (REMM). This model optimally solves the energy and exergy conflicts between the benefits of using widely available, low-temperature, low-exergy waste and renewable energy sources, like solar energy, and the inability of existing heating equipment, which requires higher exergy to cope with such low temperatures. In recognition of the challenges of retrofitting existing buildings in the EU stock, most of which are more than fifty years old, this study has developed a multi-pronged solution set. The first prong is the development of heating and cooling equipment with heat pipes that may be customized for supply temperatures as low as 35 °C in heating and as high as 17 °C in cooling, by which equipment oversizing is kept minimal, compared to standard equipment like conventional radiators or fan coils. It is shown that circulating pump capacity requirements are also minimized, leading to an overall reduction of CO2 emissions responsibility in terms of both direct, avoidable, and embodied terms. In this respect, a new heat pipe radiator prototype is presented, performance analyses are given, and the results are compared with a standard radiator. Comparative results show that such a new heat pipe radiator may be less than half of the weight of the conventional radiator, which needs to be oversized three times more to operate at 35 °C below the rated capacity. The application of heat pipes in renewable energy systems with the highest energy efficiency and exergy rationality establishes the second prong of the paper. A next-generation solar photo-voltaic-thermal (PVT) panel design is aimed to maximize the solar exergy utilization and minimize the exergy destruction taking place between the heating equipment. This solar panel design has an optimum power to heat ratio at low temperatures, perfectly fitting the heat pipe radiator demand. This design eliminates the onboard circulation pump, includes a phase-changing material (PCM) layer and thermoelectric generator (TEG) units for additional power generation, all sandwiched in a single panel. As a third prong, the paper introduces an optimum district sizing algorithm for minimum CO2 emissions responsibility for low-temperature heating systems by minimizing the exergy destructions. A solar prosumer house example is given addressing the three prongs with a heat pipe radiator system, next-generation solar PVT panels on the roof, and heat piped on-site thermal energy storage (TES). Results showed that total CO2 emissions responsibility is reduced by 96.8%. The results are discussed, aiming at recommendations, especially directed to policymakers, to satisfy the Paris Agreement.

Nanofluid is a new type of heat transfer medium formed by adding metal or non-metal in liquid medium in a certain proportion and manner, which has many advantages over the traditional working fluid. Combining heat pipes with nanofluids and using nanofluids as the working material of heat pipes can reduce thermal resistance and effectively improve the heat transfer performance of heat pipes. This paper provides a relevant overview of heat pipes and nanofluids, and introduces the relevant classifications of heat pipes, the working principle and the relevant research on nanofluid-enhanced boiling heat transfer. It conducts a literature review on the application of nanofluids in heat pipes, and finally proposes possible future research directions.

Coal spontaneous combustion is one of the major disasters in coal storage and coal transportation. Consequently, coal fire prevention and control technology is one of great significance to the safe operation of coal mines. Heat pipe is a passive heat transfer device by phase change method. Thermal energy can be transported from the underground to the surface continuously by the heat pipe effect, so that it is expected to diffuse concentrated heat and reduce the temperature of the coal pile, which is effective for preventing coal spontaneous combustion. The experiment removing thermal energy from the underground coal is carried out in order to identify the feasibility of the heat pipe heat extraction heat from the coal dump. The results out of the present experimental conditions were shown that the application of heat pipes are contributing to extinguishing coal fire as well as for energy recovery utilization purpose.

A comprehensive review of heat pipe: Its types, incorporation techniques, methods of analysis and applications

A heat pipe is an excellent heat transfer device, widely used in electronics cooling. Nanofluids have superior thermophysical properties. Researchers noticed that nanofluids are very effective working fluids as they enhanced the heat transfer characteristics of heat pipes (HPs). Mono nanofluids have their limitations regarding the applications in heat pipes. Therefore, the research community extends its work toward the application of hybrid nanofluids. In the present investigation, the authors used TiO2/H2O and (TiO2 + MWCNT)/H2O as working fluid in the HP for a wide range of power input (50–100 watts). The authors noticed the significant enhancement in the performance of HP using hybrid nanofluids. The mechanisms/causes of enhancement in the TPHP have been identified.

The Compatibility of Mild Carbon Steel and Water in a Heat Pipe Application

The rapid development of transportation electrification brings unprecedented opportunities and challenges as well to the technological improvement of high-power-density motors. As the major restriction of motor performance, thermal issues attract more attention recently and the heat pipe (HP), due to its high thermal conductivity and lightweight characteristics, is identified as a promising solution. Though HPs have been attempted in cooling systems of electrical machines, their thermal benefits still need to be fully understood. This article provides a comprehensive review and performs a series of experimental investigations to fill the technology gaps for the HP application in electrical machines. First, the HP technology is briefly introduced, followed by a detailed review on its applications in different locations of electrical machines with corresponding thermal improvements reported. Then, experimental tests are conducted to investigate the correlation between the HPs’ parameters and their cooling effectiveness, including cross-sectional shape, bending angle, fins arrangement, and inclination angle. The obtained results and conclusions could provide a guideline for the promotion of HPs in the next-generation electrical machines for future transportation.

The contribution is listed possible application of heat pipes in systems for obtaining heat from flue gas of small heat sources. It is also stated in the contribution design an experimental device on which to study the impact of fill (the quantity, type of load) at various temperature parameters (temperature heating and cooling) thermal power transferred to the heat pipe. Is listed measurement methodology using heat pipes designed experimental facility, measurement results and analysis of the results obtained.

The development of high performance and high density packaging electronic devices has led to the concentration of heat generation in smaller areas, resulting in the formation of "hotspots", i.e., regions of high heat flux. Localized high temperatures can adversely affect the performance of electronic components or cause high thermal stress. Therefore, there is an urgent need to develop thin, high performance cooling devices that can achieve effective heat dissipation in confined spaces. Micro/nanofabrication technologies offer solutions to address these challenges. Heat pipes, as efficient passive cooling devices, are widely used for heat dissipation in various electronic devices. High capillary pumping performance and heat transfer area capillary wicks can be obtained through micro/nanoprocessing technology. This paper presents a comprehensive review on the types and applications of heat pipes and discusses the principles of enhancing heat transfer in heat pipes through micro/nanostructures. Furthermore, summarizes various fabrication methods for micro/nanostructured heat pipes, including chemical and oxidation treatment, laser processing, lithography technology and etching processes, electrical discharge machining, electrochemical deposition and so on. Finally, the characteristics of various fabrication methods together with the issues and challenges faced in the development of heat pipes are presented.

This volume provides information on recent progress in spacecraft thermal control and the supporting disciplines of conduction, thermal radiation, and heat pipe theory and application. Four problem areas are considered: conduction heat transfer, radiation heat transfer, thermal control, and heat pipes. The topics covered include finite-element methodology for transient conduction/forced-convection thermal analysis; effects of surface finish on thermal contact resistance between different materials; mathematical models for wide-band nongray gas radiation in spherical and cylindrical geometries; thermal design, analysis and testing of the Shuttle remote manipulator arm; porous heat pipe; and transient behavior of liquid trap heat-pipe thermal diodes. Also discussed is the thermal design concept for a high-resolution UV spectrometer.

This article focuses on passive systems that are used in energy and thermal-fluid applications. These passive systems do not have moving parts and are reliable and cost-effective. Fluid motion in these passive devices could be driven by capillary force, gravity, osmotic pressure, and/or concentration gradient. The fundamental mechanisms and limitations of transport phenomena for passive systems are highlighted, followed by their applications in heat pipes, fuel cells, thermal energy storage, and desalination systems. The capabilities of the passive systems are limited by the balance between the driving force and transport resistance. Based on the fundamental understanding of fluid flow and phase change in passive systems, this study proposes associated transport phenomena and quantitative criteria to determine the maximum heat transfer rate, the transport distance, and minimum pore size of wick structures (when relevant) in these passive devices. This article concludes with the discussion of challenges and future opportunities of passive systems.

Introduction HEAT PIPE CHARACTERISTICS The Role of Capillarity in Heat Transport Pressure and Temperature Distributions Heat Transport Limits Heat Pipe Startup References HEAT PIPE TECHNOLOGY Heat Transport Fluids Containment and Wick Materials Wick Characteristics Heat Pipe Fabrication Environmental Influences on Heat Pipe Operation Heat Pipe Systems References FLUID FLOW IN A HEAT PIPE The Nature of the Flow Process General Pressure Drop Formulation Frictional Pressure Drop for Constant Surface Mass Flux Frictional Pressure Drop for Nonconstant Surface Mass Flux Hydraulic Diameter Frictional Pressure Drop in a Porous Flow Passage Frictional Pressure Drop for Convective Cooling References HEAT TRANSPORT LIMITS Capillary Pumping Limit Sonic Limit Entrainment Limit Boiling Limit Heat Pipe Operational Boundaries Comparison of Calculated and Experimental Heat Transport Limits References HEAT PIPE DESIGN: STEADY STATE Design Criteria and Constraints Heat Pipe Area-Temperature Relations Heat Pipe Internal Dimensions Structural Considerations Additional Design Topics Heat Pipe Exchangeers References HEAT PIPE DESIGN: TRANSIENT BEHAVIOR Heat Pipe Startup Features of the Transient Model Transient Equations Calculational Procedure Assessment of Heat Pipe Startup References DESIGN EXAMPLES Heat Pipe Space Radiator Transient Analysis of the Heat Pipe Space Radiator References Appendices

This paper explores the feasibility of using the heat pipe for steam condensation. In this paper an attempt is made to replace thousands of condenser tubes by hundreds of Heat Pipes.The design details of heat pipe, that is, material of heat pipe, heat pipe length, diameter of heat pipe for condensation purpose is described. The feasibility study was carried out for smooth operation of the heat pipe that is without ceasing during operation. Experimental setup and results of steam condensation studies are presented.

In the infrared system, in order to decrease the background radiation and maximize the sensitivity, cooling down the aft-optic components' temperature is a better choice. Some two-phase devices such as grooved heat pipe or loop heat pipe (LHP) were used to link the cold sink and IR aft-optic components. This paper presented the testing results of cryogenic grooved heat pipes which were used in some infrared test systems in the temperature range of 160~210K with different heat load conditions. Also, some experimental results of cryogenic loop heat pipe were introduced in this paper.