Showing papers on "Heat pipe published in 2021"

Battery thermal management system based on the forced-air convection: A review

Abstract: With the popularization of lithium ion battery cells, the battery thermal management system (BTMS) has been paid much attention since it is important in ensuring the safety and performance of lithium ion battery pack. Although the BTMS based on the forced-air convection with the advantage of low-cost, simple, and tight design has been favored by practical applications in electric vehicles and electrochemical energy storage stations, the forced-air convection is always criticized for its low cooling efficiency and low-temperature uniformity. Thus, extensive investigation has been conducted to optimize the BTMS based on the forced-air convection. This paper reviews the developments on the application of forced-air convection into BTMS in terms of preheating and cooling. Firstly, the thermal models for battery cells are introduced from the perspective of the lumped model and electrochemical model. Meanwhile, the methods to simulate the flow field are also presented. The computational fluid dynamics and short-cut methods have been compared in the paper. The main optimization route is summarized which includes optimization of pure forced-air convection, the combination with phase change material(PCM), and integration with heat pipe. For the optimization of the pure forced-air convection, four technical routes are concluded, which are the location of inlets and outlets, flowing tunnel, controlling strategy, and flowing state. As for the hybrid BTMS based on forced-air convection with heat pipe and PCM, some extra structures such as mesh or finned structure are also included for enhancing the heat dissipation. Finally, some perspectives and outlooks on BTMS based on the forced-air convection are put forward for future development.

A review on the applications of micro-/nano-encapsulated phase change material slurry in heat transfer and thermal storage systems

Abstract: In modern heat transfer systems, thermal storage not only causes the balance between demand and supply, but also improves the heat transfer efficiency in these systems. In the present study, a comprehensive review of the applications of micro- or nano-encapsulated phase change slurries (MPCMs/NPCMs), as well as their effects on thermal storage and heat transfer enhancement, has been conducted. MPCMs/NPCMs have a myriad of applications and various usages such as pipe and channel flows, photovoltaic/thermal, solar heaters, air conditioning systems, storage tanks and heat pipes that have been categorized and studied. It was found that there are many advantageous adding MPCM/NPCM to the base fluid. The most important effect is that the addition of PCMs to the base fluid can intensify the capacity of energy absorption in the base fluid. These materials can absorb a high proportion of received energy by changing their phase and prevent temperature increment of the base fluid. Thereupon, the specific heat of the fluid in the presence of the micro-/nano-capsules increases. Moreover, in most studies reviewed, heat transfer coefficient and Nusselt number increase by the addition of micro-/nano-capsules to the base fluid. Also, the addition of MPCM/NPCM to the base fluid could make this material pumpable, although increment in the concentration of micro-/nano-capsules raises the viscosity of the working fluid and thereupon the pumping power. On the other hand, for a same heat load, the pumping power decreases due to the lower required flow rate in comparison with pure working fluid. The most important factor that must be considered in the application of MPCMs/NPCMs is the complete phase change of the material. Given the favorable thermal and fluid characteristics of MPCMs/NPCMs, the utilization of these materials could be a promising method to transfer heat and store it with high efficiency and low pumping power.

Development and validation of a TRNSYS type to simulate heat pipe heat exchangers in transient applications of waste heat recovery

Abstract: Heat pipe heat exchangers (HPHEs) are being more frequently used in energy intensive industries as a method of low-grade waste heat recovery. Prior to the installation of a HPHE, the effect of the heat exchanger within the system requires modelling to simulate the overall impact. From this, potential savings and emission reductions can be determined, and the utilisation of the waste heat can be optimised. One such simulation software is TRNSYS. Currently available heat exchanger simulation components in TRNSYS use averaged values such as a constant effectiveness, constant heat transfer coefficient or conductance for the inputs, which are fixed during the entire simulation. These predictions are useful in a steady-state controlled temperature environment such as a heat treatment facility, but not optimal for the majority of energy recovery applications which operate with fluctuating conditions. A transient TRNSYS HPHE component has been developed using the Effectiveness-Number of Transfer Units (ɛ-NTU) method and validated against experimental results. The model predicts outlet temperatures and energy recovery well within an accuracy of 15% and an average of 4.4% error when compared to existing experimental results, which is acceptable for engineering applications.

Numerical simulation of double diffusive convection and electroosmosis during peristaltic transport of a micropolar nanofluid on an asymmetric microchannel

Abstract: A numerical computation is performed to analyze the double diffusive convection in micropolar nanofluids flow governed by peristaltic pumping in an asymmetric microchannel, in the presence of thermal radiation and an external magnetic field. The highly nonlinear governing equations are diluted by using desirable physical assumptions such as lubrication approximation and low zeta potential. Convective boundary conditions are employed. This enables us to determine numerical estimates of various physical flow variables such as velocity, pressure gradient, spin velocity, temperature of the nanofluid, concentration of solute, and volume fraction of nanoparticles for sundry parameters like micropolar parameter, coupling parameter, solutal Grashof number, thermophoretic diffusion coefficient, Grashof number, thermal radiation parameter and Helmholtz–Smoluchowski velocity with the aid of bvp4c function built-in command of MATLAB 2012b. Influence of each relevant parameter on flow, thermal and species characteristics are computed in this study. Influence of Soret and Dufour parameters are also simulated. This model is applicable to the study of chemical fraternization/separation procedures and various thermal management systems like of heat sinks, thermoelectric coolers, forced air systems and fans, heat pipes, and many more.

Experimental study and numerical simulation of a Lithium-ion battery thermal management system using a heat pipe

Abstract: The use of electric appliances equipped with lithium-ion batteries, have been increasing every day. The energy density of lithium-ion batteries is high; however, their lifespan and performance are heavily influenced by the rise in temperature. Hence, the development of thermal management of the lithium-ion battery is very necessary. One of the most effective methods for battery cooling is the use of heat pipe. Since many batteries are used together in order to generate higher power, it is important to predict their thermal performance. In this study, a lithium-ion battery heat management system equipped with a heat pipe is investigated. Part of a battery pack consisting of two batteries and a made heat pipe is selected and its performance is investigated experimentally. These tests are performed at various ambient temperatures through a made test chamber with the ability to accurately control temperature. In addition, with the help of software, a coupled simulation model for lithium-ion battery cooling with a heat pipe has been developed and compared with experimental data. The experimental results show that although with increasing ambient temperature, the battery surface temperature increases, but due to the decrease in thermal resistance of the heat pipe, the effect of this temperature rise can be moderated and work as an active method. In addition, using forced convection in the condenser section, not only can the battery surface temperature be controlled below 40 °C, but it also distributes the temperature uniformly over the battery surface. The use of the heat pipe also helps to maintain more stable temperature conditions with lower temperature fluctuations in consecutive battery cycles.

Comprehensive review of the recent advances in PV/T system with loop-pipe configuration and nanofluid.

Abstract: Solar photovoltaic/thermal technology has been widely utilized in building service area as it generates thermal and electrical energy simultaneously. In order to improve the photovoltaic/thermal system performance, nanofluids are employed as the thermal fluid owing to its high thermal conductivity. This paper summarizes the state-of-the-art of the photovoltaic/thermal systems with different loop-pipe configurations (including heat pipe, vacuum tube, roll-bond, heat exchanger, micro-channel, U-tube, triangular tube and heat mat) and nanoparticles (including Copper-oxide, Aluminium-oxide, Silicon carbide, Tribute, Magnesium-oxide, Cerium-oxide, Tungsten-oxide, Titanium-oxide, Zirconia-oxide, Graphene and Carbon). The influences of the critical parameters like nanoparticle optical and thermal properties, volume fraction, mass flux and mass flow rates, on the photovoltaic/thermal system performance are for the optimum energy efficiency. Furthermore, the structure and manufacturing of solar cells, micro-thermometry analysis of solar cells and recycling process of photovoltaic panels are explored. At the end, the standpoints, recommendations and potential future development on the solar photovoltaic/thermal system with various configurations and nanofluids are deliberated to overcome the barriers and challenges for the practical application. This study demonstrates that the advanced photovoltaic/thermal configuration could improve the system energy efficiency approximately 15%-30% in comparison with the conventional type whereas the nanofluid is able to boost the efficiency around 10%-20% compared to that with traditional working fluid.

Heat pipes: progress in thermal performance enhancement for microelectronics

Abstract: The aim of this study is to oversee the impact of various techniques on thermal performance of heat pipes and to comprehensively cover the progress made so far in improving thermal performance. Thermal performance of heat pipes has been considerably improved by applying very novel techniques proposed by different investigators. Some major techniques have been reviewed and discussed: use of nanofluids, manufacturing different types of grooves and fins, use of different types of wicks, by inner surface treatment, use of self-rewetting fluids, use of embedded heat pipes that is passive cooling mechanism, using various inclination angles in heat pipes, etc. The presented study concludes that there are diverse methods for thermal performance enhancement of heat pipes each having its own impact level and constraints such as optimized parameters, manufacturing constraints, economic feasibility and commercial barriers. Some techniques show reversion in results when exceeded a certain level, e.g., crossing optimum concentration of nanofluid would reduce thermal performance of heat pipes. This review yields enough knowledge to optimize alteration parameters to get maximum augmentation in results and provides strong insight to decide about, which specific technique should be used for a case.