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Pipes in heat exchanger systems are usually made of metallic materials to achieve a high level of thermal conductivity and thus high efficiency. However, substitution with polymer materials has a great potential. Plastics save weight, can be produced at lower cost and emissions, and are ideal for use in corrosive or chemically aggressive environments, where most metals fail. The challenge, however, is their much lower thermal conductivity in comparison. To reduce this disadvantage, fillers are used to transport thermal energy through the less conductive polymer matrix. In fact, high filler ratios are required to achieve an acceptable level of thermal conductivity for heat exchanger systems. However, these high filler ratios have a significant impact on the material properties of the polymer, such as the flexibility, which is drastically reduced. The result is a brittle material with limited suitability for use in heat exchanger systems. This paper describes a novel approach to effectively increase the thermal conductivity of polymer materials by optimizing the orientation of anisotropic filler particles by die design. Standard pipe extrusion dies result in continuous shear forces in the direction of extrusion. Accordingly, the resulting filler network has a higher thermal conductivity in the axial direction of the pipe than radially through the pipe wall. However, radial heat transfer is essential in pipe heat exchanger systems. To improve this, various die designs for targeted radial alignment of filler particles are discussed in this paper. Furthermore, the potential for improvement of the die designs is investigated. So far, the most efficient die design achieves an increase in thermal conductivity of up to 74 % compared to a standard pipe extrusion die. [ABSTRACT FROM AUTHOR]

Heat exchangers are a common heat transfer mechanism used in a variety of applications ranging from home to industrial, aircraft, and vehicles. The aim of this research is to study the hydrothermal efficiency of a double pipe heat exchanger with helical fins on annular side of counter flow heat exchanger numerically and compare the results of a double tube with and without screw tape. The investigation begins by employing numerical modeling of helical tapes under different configurations, with different pitches (10, 15, and 20) mm and one height of 10 mm as passive heat transfer augmentation strategies, which are simulated using ANSYS 2022 R1 software. The findings reveal that the current work's numerical results and earlier research's experimental findings are in good accord. Furthermore, while using (Helical Tap Insert) (HTI), the thermal performance of the new typical is found to be better than the typical model. Furthermore, it was found that the Nusselt number achieves the highest growth when the pitch (p) is (20) mm and increases the pressure drop. Furthermore, it was discovered that when the pitch (p) is (20) mm and pressure drop is increased, the Nusselt number grows the most. Furthermore, as associated to the typical model, the total thermal effectiveness of heat exchanger for the new model has greater by 9.9%. This difference is due to the fact that in the theoretical study, ideal conditions are assumed. The experimental design, the assumptions, operating circumstances, and accuracy of the devices are taken into account. It was noted that the value of the specified percentage of hydrothermal improvement achieved the highest value in performance for the same case that was with spiral fin and pitch length (20) mm, which is 1.6% compared to the traditional model. [ABSTRACT FROM AUTHOR]

This paper aims to improve the thermal performance of Closed loop pulsating heat pipe (CLPHP) with nanofluid fused with refrigerants. In this paper, the thermal studies were carried out by SWCNT and MWCNT nanofluids fused with R-134a. Experimentation was conducted at 10W heating power and 90° inclination angle, temperature difference from evaporator and condenser were validated. Results indicate that using nanofluid fused with R-134a, could improve the thermal performance of heat pipes. And the readings were taken every two minutes. And the obtained result was plotted to and the result shows the addition of CNT nanofluid to the refrigerant improves the Thermal performance of the closed-loop heat pipe (CLPHP). Compare to SWCNT, MWCNT with R-134a shows better heat transfer and improve the cooling capacity. [ABSTRACT FROM AUTHOR]

Extracting clean Energy through different technologies and producing electricity has played a major role nowadays due to constant growing energy consumption because of increase in population as well as deteriorating effect on atmosphere due usage of fossil fuels. To have an efficient clean energy technology has become the necessity of time. Application of solar thermal energy as Solar cooker, Solar dryer, Solar Water Heater, Solar desalination etc, are widely used in industry and domestic applications. Among these different application of Solar Thermal Energy, Evacuated Tube Collectors are used extensively so far as it proposes less convection losses which arise in solar concentrators from the movement of air over hot receiver surfaces. It is found that use of nanofluid for the thermal performance enhancement of Evacuated tube collector using heat pipe significantly changed scenario of using ETC. With this paper various characteristics of using nano fluid with Evacuated tube collector has been critically reviewed for the thermal performance enhancement of ETC with effect of parameters like weight fraction, filling ratio, type of nano particle. [ABSTRACT FROM AUTHOR]

In order to transfer heat with minimal leakage to surroundings and to increase efficiency energy exchanger systems are used through various methods. the output from the twin-pipe energy exchanger system is essential in terms of both system economics and efficiency. as a result, boosting the rate of thermal gradient rate is important for long-term energy growth. the goal of this study was to review heat transmission and friction properties in the horizontal double pipe heat exchanger. after thorough literature review, it has been concluded that various author has investigated different types of twisted tape insert their experimental and modeling studies and a little work is observed using twisted tape inserts with dimple configurations in a double pipe heat exchanger. [ABSTRACT FROM AUTHOR]

In this paper research has been conducted by varying the internal design of the pipes that are used in the compact air to air heat exchanger to see if the addition of turbulizers in the internal section can result in an improvement in the ΔT at the exit of the pipe. We are also looking at the internal flow characteristics of the air inside the heat exchanger pipes. The drop in pressure at the exit of the pipes because of the addition of the turbulizers has also been investigated. All these analysis have been performed using the commercial software package ANSYS CFX and the results are presented in this paper. [ABSTRACT FROM AUTHOR]

Recently heat transfer enhancement utilizing double pipe heat exchangers had been a key of engineering research topic in different field. The present work illustrates how magnesium oxide nanofluid (MgO) affects the enhancement of heat energy exchange in a double pipe heat exchanger at different concentrations of nanoparticles. The governing equations of heat and fluid flow had been solved using ANSYS FLUENT based upon finite volume scheme. The temperatures for hot and cold streams at the inlet are 50 oC & 25 oC respectively. The volumetric flowrates for hot fluid (8-20) LPM and for cold fluid 8 LPM. The magnesium oxide nanoparticles MgO have concentrations range (0.125 % - 2%) by volume were implemented. According to the findings of the study implemented in sustainable applications and different industries fields, heat energy exchange rises when the volume concentration of nanoparticles increases also. Currently, there are several studies have been conducted to assess the consequence of nanofluid that enhancement heat energy exchange in the double pipe heat exchanger. The type and concentration of nanoparticles in the base fluid play important role in the enhancement of heat energy exchange. This paper illustrated the effect of increased magnesium oxide nanofluid MgO nanoparticles concentration on the heat energy exchange of a double pipe heat exchanger. [ABSTRACT FROM AUTHOR]

This study investigates heat transmission and thermal performance factor characteristics in a tube with coil wire and twisted tape inserts using air as the working fluid. This study investigates heat transmission and thermal performance factor characteristics in a tube with coil wire and twisted tape inserts using air as the working fluid. The goal of this research is to improve forced convection heat transfer in tubes with and without swirl inserts and coil wire inserts for air Reynolds numbers ranging from 10.328×103 to 11.769×103. The impacts of different parameters of heat transfer are considered in this work with heat flux are constant conditions of 600 W/m2 and 800 W/m2 with using the coil wire and twisted tapes with three ratios (y/w = 3, 4 and 5). The test section is a horizontal annular passage with outer diameter 10 cm. The results showed that using coil wire inserts to improve heat transfer coefficient factors in tubes resulted in local heat transfer coefficient percentages of (5.1%) to (7.8%) with heat flux are constant conditions of 600 W/m2 and 800 W/m2, respectively. While tube with swirl inserts provide local heat transfer coefficient percentages of (3.6% to 6.1%) for heat fluxes (600) W/m2 and (800) W/m2, respectively. The obtained results demonstrate that as the twisted ratio (y/w) decreases, the mean Nusselt number and heat transfer coefficient in the tube with twisted tape and coil wire rise. Experimental results is shown, heat transfer coefficient for the coil wire when compared with that of swirl inserts tube were ranged between (10.6%) to (16.5%) and (11.5%) to (17.3%) for the heat flux (600) W/m2. [ABSTRACT FROM AUTHOR]

Investigation still on board for finding the best techniques to develop the thermal and hydraulic performance of the heat exchanger. One of the useful, practical methods for finding the modification is the numerical analysis. This numerical analysis was obtained by modelling and simulation using ANSYS FLUENT software. In this present work five elements were modelled and simulated of three different configuration models, helical tape, rectangular and triangular straight strip inserts were inserted inside the inner pipe. This simulation was employed according to the working operation conditions of the real practical double pipe heat exchanger. The results show that, the helical tape configuration demonstrated the effective enhancing technique of the heat transfer, which is improving the thermo-hydraulic performance of this type of heat exchanger in this study. According to this work, the technique of studying numerically the design enhancement of the heat exchanger can produce an excellent result and gives a good recommendation to transfer it into practical work. [ABSTRACT FROM AUTHOR]

Energy crisis and carbon emission are increasingly prominent issues in our society. As one of the clean energy sources, thermoelectric power generation is a promising alternative energy technology to convert heat into electricity. If there is a heat source, thermoelectric generators can provide electricity for watches, sensors, electronics, spacecraft, etc., and can also be used to recover waste heat, such as automobile exhaust heat, industrial waste heat, ship waste heat, etc. This paper begins with the basic principles of thermoelectric generators and an outlook of thermoelectric materials in different application scenarios. Then, the thermoelectric generator systems, which can be classified into different groups according to their different power generation levels, also the corresponding progress, challenges, and future development are presented. In addition to exploring high-performance thermoelectric materials, the system efficiency of thermoelectric generators is much dependent upon advanced structural design and thermodynamic optimizations. In the previous and present works, some new optimization methods are applied to improve the performance of thermoelectric devices and systems, these include such as the asymmetric design, phase change heat transfer, optimization for thermoelectric devices based on temperature distributions, also heat pipe and converging design for thermoelectric generator systems. These works help breakthrough in thermoelectric power generation from low-level power generation to relatively higher-level power generation. The current progress helps provide a comprehensive insight into thermoelectric power generation technology from micro power supplies to kilowatt systems. [ABSTRACT FROM AUTHOR]

Evaporative cooling has been around since ancient times. As a cooling device, evaporative cooling has several advantages and disadvantages. This paper discusses some of the results of investigations on three types of evaporative cooling, namely direct evaporative cooling, indirect evaporative cooling, and combined evaporative cooling. Cooling media is part of the evaporative cooling that is widely studied. Some researchers also made several innovations to improve the efficiency of evaporative cooling. One of the innovations that will be discussed in this paper is to add heat pipes to evaporative coolers. As a passive heat transfer, heat pipes are expected to increase the efficiency of evaporative cooling without adding high cost. [ABSTRACT FROM AUTHOR]

Binary non-azeotropic mixtures are increasingly used in various heat exchange devices as a heat carrier or working fluid. When using non-azeotropic mixtures, it is necessary to take into account the features of the heat transfer process determined by specific thermodynamics of these mixtures. This paper presents the results of a study of hydrodynamics and heat transfer during circulation of an alcohol-water mixture through a heated cylindrical channel. The inner diameter of the channel is 7.6 mm, the length is 4 m. The experiments were carried out using a mixture of ethyl alcohol and water at mass concentration of the volatile component of 22 %. Mass velocity range is 160–720 kg/(m2·s), the vessel pressure is 0.02 MPa. The operating parameters correspond to both single-phase and two-phase heat transfer regimes. A detailed description of the experimental setup and the results on temperature distribution along the working section are given. It is found that in a non-azeotropic mixture, the vaporization process begins significantly earlier than the equilibrium conditions determine. [ABSTRACT FROM AUTHOR]

The steady state thermodynamic investigation of vapour compression refrigeration system (VCRS) using CNT, Au and HAuCl4 nanoparticles suspended in different proportions in polyalkylene glycol lubricant is carried out and presented in this paper. The most commonly adopted R134a refrigerant is used in the system. The energetic and exergetic analysis are performed for nanoparticles with different volume fractions viz. 0.1% Au, 0.2% Au, 0.1% HAuCl4, 0.2% HAuCl4, 0.1% Au and 0.05% CNT, 0.2% Au and 0.02% of CNT. The experimental test rig is fabricated and tested with the different proportions of nanoparticles. Compressor exit temperature and pressure, condenser exit temperature, evaporator inlet and exit temperature are measured. The energy and exergy efficiency of the system components, cooling capacity, compressor power input and coefficient of performance (COP) of the system are obtained. The suspension of Au, HAuCl4 and CNT nanoparticles up to 0.2% and combination of Au(0.1%, 0.2%) and CNT(0.02%, 0.05%) increases the heat transfer characteristics and thereby system functioning. From the results it is established that the power input decreases by 16.7%, COP increases by 21.3% and the second law efficiency increases by 11.2%. [ABSTRACT FROM AUTHOR]

This paper gives an overview of several published current studies concerning heat transfer enhancement on the double pipe heat exchanger. Since double pipe heat exchanger has drawn much consideration due to simplicity and wide-range utility. The flow manipulation technique to enhance heat transfer in a double pipe heat exchanger has been frequently cited. Also, various research addressing working fluid on a double pipe heat exchanger has been discussed in detail. Another technique is known as surface modification that has an infrequent investigation comparing the other techniques. Correlation of Nusselt number and pressure drop coefficient shown in this overview. Future research opportunities are mentioned. [ABSTRACT FROM AUTHOR]

Heat pipes are promising heat removal devices widely used in a variety of fields ranging from thermal management of electronic components to terrestrial and aerospace applications. Their working principle, phase change of a working fluid, makes them superior to other conventional cooling methods. Heat pipes have been commercially available since the mid of 1960’s. Only in the past few years the electronics industries have embraced heat pipes as reliable, cost-effective solutions for high end cooling applications. This paper presents a detailed review of the materials, applications and performance of heat pipes using nanofluid as working medium. The first section reviews the heat pipes which are operating with nanofluid as working fluid. This section deals with nanofluid of different nanoparticles. The second section reviews heat pipes coated with different types of nanoparticles and third section reviews the performance of heat pipes with nanoparticle coated wick. [ABSTRACT FROM AUTHOR]

Mainly consider the heat conduction between the layers of fabric, the thermal convection between the fabric and the air to establish the model of this paper. Firstly, the heat conduction equation between multilayer fabrics is constructed by the law of conservation of energy and Fourier's law; then, the heat convection equation between the fabric and the air is expressed by Newton's cooling formula; Finally, the thermal conductivity, temperature boundary conditions and temperature load between the fabrics of each layer were determined, and a heat transfer model conforming to the external environment—fabric (I~III)—air layer—human skin system was established. Considering the wide application of finite element in heat transfer, we use ANSYS heat transfer module to calculate the temperature distribution of each layer of the system by using transient thermal analysis method. The simulation results are well fitted to the actual experimental results, and the temperature of each layer is generated. Distribution. [ABSTRACT FROM AUTHOR]

The paper proposes a design of a condensing heat exchanger of thermosyphon loop heat pipe for cooling of electrotechnical box. The heat pipe appears to be a very good cooling device that does not require any mechanical device in its construction. A heat pipe is a structurally simple device capable of transmitting high heat flows over relatively long distances. It may be of circular or other cross-section. If one part of the heat pipe is heated - the evaporator and the other cooled - the condenser, there is a constant evaporation and condensation of the working fluid. The section between the evaporator and the condenser where there is no phase change is called adiabatic section. The heat transfer in the heat pipe is based on the phase change principle. The design of the condensing exchanger must ensure condensation of the vapor phase and heat the environment to the surrounding environment in an ideal state only by natural convection. The article describes the design of a condensing exchanger and the impact of the amount of working fluid on performance heat pipes. [ABSTRACT FROM AUTHOR]

This paper is concerned with design and optimization of cooling system for high-power LED luminaire. Dimension, shape and topology optimization algorithms and their program realization are developed with the use of MathCad for the maximal heat transfer rate, least temperature gradient between LED and fins, minimal weight of cooling system. Thermal design by Comsol Multiphysics showed that the system on the base of heat pipes is the most effective system for high-power LED luminaire. [ABSTRACT FROM AUTHOR]

This paper proposes an approach of calculation of permissible heat fluxes of heat pipe. Simulation algorithms and their program realization are developed with the use of MATCAD. Permissible heat fluxes in the heat pipe are determined accounting operating conditions and properties of capillary-porous materials. This approach allows us to compare heat transfer characteristics of the heat pipe by using different materials and coolant. By employing simulation data heat pipes with mesh wick and groove wick are designed. [ABSTRACT FROM AUTHOR]

The paperdeals with use of LOOP thermosyphonheat pipe to transfer heat from electrotechnical box and describe of construction individual types ofLOOP heat pipes. The LOOP heat pipe is very good cooling device which requires no mechanical parts in their design. LOOP heat pipe use only phase change during heat transfer, without a compressor, fan orpump. LOOP heat pipe is more energy saving compared to conventional cooling systems with forced convection. The main advantage of cooling by heat pipe is that electrotechnical box canbe hermetically closed (dust-free construction), because dust reduces the lifetime of electrotechnical elements in box Lifetime ofLOOP heat pipeequals to the lifetime of construction material. The paper describes mathematical model of LOOP thermosyphon heat pipe (condenser). Compares selectedtypes of working fluids which are filled with a heat pipe and construction materials of heat pipe. [ABSTRACT FROM AUTHOR]

Heat pipes are heat transfer devices capable of transferring large quantities of heat effectively and efficiently. A vapor chamber (VC) is a flat heat pipe. A novel VC with hollow condenser tubes embedded on the top of it is proposed. This paper reports on the experimental thermal performance of three VC devices embedded with hollow tubes and employed as heat sinks. The first device consisted of a VC with a single hollow tube while the other two VCs had an array of multi-tubes with different tube lengths. All three devices were tested under natural and force air convection cooling. An electrical resistance heater was employed to provide power inputs of 10 and 40 W. Surface temperatures were measured with thermocouple probes at different locations around the devices. The results show that temperatures increased with heater input while total device thermal resistances decreased. Force convection results in lower temperatures and lower resistance. Dry-out occurs at high input power and with too much condensing area. There appears to be an optimum fill ratio which depended upon dimensions of the VC and also heating power. [ABSTRACT FROM AUTHOR]

A heat pipe is a passive heat transfer device capable of transferring a large quantity of heat effectively and efficiently over a long distance and with a small temperature difference between the heat source and heat sink. A heat pipe consists of a metal pipe initially vacuumed and then filled with a small quantity of fluid inside. The pipe is separated into a heating (evaporator) section and a cooling (condenser) section by an adiabatic section. In a run-around-coil heating, ventilation and air conditioning system, a wrap-around heat pipe heat exchanger could be employed to increase dehumidification and to reduce cooling costs. The thermal performance of a thermosyphon is dependent upon type of fill liquid, fill ratio, power input, pipe inclination and pipe dimensions. The boiling and condensation processes that occur inside a thermosyphon are quite complex. During operation, dry-out, burn-out or boiling limit, entrainment or flooding limit and geysering occur. These phenomena would lead to non-uniform axial wall temperature distribution in the pipe, or worse still, ineffective operation. In order to have a better understanding of the internal heat transfer phenomena, a visual study using transparent glass tubes and high speed camera recording of the internal flow patterns would be most helpful. This paper reports on an experimental investigation conducted to visualise the flow patterns in straight and Cshape thermosyphons. The pictures recorded enabled the internal flow boiling and condensation pattern occurring inside a straight and a C-shape thermosyphon to be observed. The thermosyphons were fabricated from 10 mm O/D x 8 mm I/D x 300 mm long glass tubes and filled with water with fill ratios from 0.5 - 1.5. The evaporator sections of the thermosyphons were immersed into a hot water tank that was electrically heated from cold at ambient temperature till boiling. Cooling of the condenser section was achieved using a fan. Preliminary results showed that dry-out occurred earlier at lower evaporator temperatures with small fill ratios. Further investigations to determine saturation and thermosyphon wall temperatures with various fill liquids and at different fill ratios, inclinations and pipe sizes are necessary with a more sophisticated video recording system. [ABSTRACT FROM AUTHOR]

Pulsating Heat Pipes, the new two-phase heat transfer devices, with no counter current flow between liquid and vapor have become a modern topic for research in the field of thermal management. This paper focuses on the performance of methanol and distilled water as working fluid in a closed loop pulsating heat pipe (CLPHP). This performances are compared in terms of thermal resistance, heat transfer co-efficient, and evaporator and condenser wall temperature with variable heat inputs. Methanol and Distilled water are selected for their lower surface tension, dynamic viscosity and sensible heat. A closed loop PHP made of copper with 2mm ID and 2.5mm OD having total 8 loops are supplied with power input varied from 10W to 60W. During the experiment the PHP is kept vertical, while the filling ratio (FR) is increased gradually from 40% to 70% with 10% increment. The optimum filling ratio for a minimum thermal resistance is found to be 60% and 40% for distilled water and methanol respectively and methanol is found to be the better working fluid compared to distilled water in terms of its lower thermal resistance and higher heat transfer coefficient. [ABSTRACT FROM AUTHOR]

Pulsating heat pipe (PHP) is a new, promising yet ambiguous technology for effective heat transfer of microelectronic devices where heat is carried by the vapor plugs and liquid slugs of the working fluid. The aim of this research paper is to better understand the operation of PHP through experimental investigations and obtain comparative results for different parameters. A series of experiments are conducted on a closed loop PHP (CLPHP) with 8 loops made of copper capillary tube of 2 mm inner diameter. Ethanol is taken as the working fluid. The operating characteristics are studied for the variation of heat input, filling ratio (FR) and orientation. The filling ratios are 40%, 50%, 60% and 70% based on its total volume. The orientations are 0° (vertical), 30°, 45° and 60°. The results clearly demonstrate the effect of filling ratio and inclination angle on the performance, operational stability and heat transfer capability of ethanol as working fluid of CLPHP. Important insight of the operational characteristics of CLPHP is obtained and optimum performance of CLPHP using ethanol is thus identified. Ethanol works best at 50-60%FR at wide range of heat inputs. At very low heat inputs, 40%FR can be used for attaining a good performance. Filling ratio below 40%FR is not suitable for using in CLPHP as it gives a low performance. The optimum performance of the device can be obtained at vertical position. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of a closed loop Pulsating Heat Pipe (CLPHP) as the demand of smaller and effective heat transfer devices is increasing day by day. PHP is a two phase heat transfer device suited for heat transfer applications, especially suited for handling moderate to high heat fluxes in different applications. A copper made Pulsating Heat Pipe (PHP) of 250 mm length is used in this experimental work with 2 mm ID and 3 mm OD, closed end-to-end in 8 looped, evacuated and then partially filled with working fluids. The evaporation section is 50 mm, adiabatic section is 120 mm and condensation section is 80 mm. The performance characterization is done for two working fluids at Vertical (0°) orientations. The working fluids are Methanol and Ethanol and the filling ratios are 40%, 50%, 60% & 70% based on total volume, respectively. The results show that the influence of various parameters, the heat input flux, and different filling ratios on a heat transfer performance of CLPHP. Methanol shows better performance as working fluid in PHP than ethanol at present orientation for a wide range of heat inputs and can be used at high heat input conditions. Ethanol is better choice to be used in low heat input conditions. [ABSTRACT FROM AUTHOR]