•A battery thermal management system that uses fins to enhance the combination of thermoelectric cooler and phase change material was established.•Compared the effects of four thicknesses of fins on ...the thermal management performance.•It was proved that adding fins is beneficial to improve the thermal management performance under three working conditions.•The influence of the input current on the cooling power and COP of TEC was analyzed.
In this study, a hybrid active & passive BTMS(Battery Thermal Management System) that uses fins to enhance the combination of TEC(Thermoelectric Cooler) and PCM(Phase Change Material) is shown. The cold side of the TECs produces a cooling effect, which is used to cool the PCM and prevent it from melting completely in a short time, thereby extending the temperature control time. Fins are used to transfer the heat of the PCM to the cold side of the TECs, and effectively cool the batteries at high temperatures. The effects of different fin thicknesses (2 mm-8 mm) and different TEC input currents (1A-6A) on thermal management performance were analyzed by numerical simulation. The results show that the temperature control time was prolonged by 12% when the fins were increased from 2 mm to 8 mm, but the temperature difference increased by 13.7%. When the current changed from 1A to 6A, the temperature control time increased by 87.42%, but the temperature difference and COP became worse. Comprehensive analysis of temperature control time, temperature difference, COP, 4 mm fin thickness, and TEC input current of 3A were optimal for the model in this paper.
Condensation heat transfer characteristics were studied experimentally in order to evaluate the heat transfer performance of horizontal copper heat transfer tubes (smooth and enhanced). Using R410A ...and R32 as refrigerants, condensation heat transfer experiments were carried out for a saturation temperature of 45 °C; inlet vapor quality of the tube was 0.8 and outlet quality was 0.2; refrigerant mass flow rate range was in the range from 68 to 371 kg/(m2·s). Single-phase heat balance verification found that the heat loss is less than 6 %, with the deviation between single-phase experimental results and various correlations being less than 15 %. The condensation heat transfer coefficient increases with an increase in mass flow; as the mass flow rate increases, the turbulence of the liquid flow increases and the liquid film becomes thinner; thermal resistance is reduced and the heat transfer coefficient (HTC) increases. Experimental results determined that the performance factor ratio (enhanced tube/smooth tube) of the three-dimensional surfaces investigated here are greater than 1. Tubeside heat transfer enhancement factor (EF) of the HB/D tube is the highest (max 1.76); its performance is closely related to increasing fluid turbulence and improving drainage. Performance factor (PF) of the HB/D tube (max 1.38) is the highest for most of the flowrates. All this indicates excellent thermal performance. Flow model-based analysis was performed in order to develop a correlation for the condensation heat transfer coefficient and the pressure drop for the enhanced surface tubes. Both prediction models accurately predicted all data points within a limited margin of error.
During compliant face grinding of difficult-to-machine areas like the blade runner surface, significant heat accumulation at the tight interface between the workpiece and tool. This leads to ...limitations in surface integrity and tool life longevity. This study introduces a novel cooling method that incorporates an axially rotating impeller into the cavity of a small compliant grinding tool. The internal impeller structured compliant tool was prepared base on additive manufacturing. Numerical simulations and experimental studies were carried out to investigate its heat transfer mechanisms and its effect on the continuous grinding performance. The findings indicate that while favorable surface roughness and high material removal rates coincide with elevated grinding temperatures, the Shore hardness of the flexible material decreases as the grinding temperature rises. Consequently, there is a reduction in grit cutting depth and an increase in the proportion of rubbing and ploughing grit due to the grit’s height rearranges. The designed internal impeller facilitates the external cooling air with internal vortices to reach the grinding interface zone limiting heat accumulation to below 91.0°C and removing chips to reduce grit adhesion. Consequently, the grinding performance was more consistent, with a stable material removal depth ranging from 97 µm to 103 µm. 3D-printing-based compliant tools provide new insights into consistently high grinding performance for complex parts.
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•Compliant tools incorporated internal-impeller was designed to enhance thermal and grinding performance.•Quantitative analysis of the effect of grinding temperature on the removal mechanism of titanium alloy.•Inner impeller structure enhances heat transfer through the inner wall, interface and chip removal.
•Experiments on flow boiling with R365mfc on sintered porous coating high heat flux tubes.•The effects of mass flux and heat flux on the enhanced heat transfer performance.•The effect of porous ...coatings on the enhanced heat transfer performance.•Maximum heat transfer enhancement has been identified.•Analysis of the bubble and liquid film effect on the enhanced heat transfer mechanisms.•An empirical heat transfer correlation has been proposed for sintered porous coating high heat flux tubes.
Sintered porous coating tubes are high performance heat transfer components which are used to enhance boiling heat transfer. Sintering metal powder particles on the surfaces of plain tubes form porous coatings with numerous cavities which can promote nucleation of bubble generation in boiling processes and thus enhance boiling heat transfer enhancement. In the present study, experiments of the subcooled and saturated flow boiling heat transfer characteristics on the sintered porous coating tubes were conducted. The test tubes with porous coatings have an outer diameter of 25 mm, a length of 1 m and the coating thicknesses are 0.06 mm, 0.12 mm, 0.18 mm, and 0.25 mm, respectively. The heat transfer performance of high flux tubes is evaluated with a mass flow rate ranging from 128.3 to 252.03 kg/m2·s and the saturation temperature of the experimental section is controlled between 45 and 50℃. The influence of flow conditions, heat flux, and properties of the sintered layer on boiling heat transfer was discussed. The results indicate that sintered porous media can effectively reduce the degree of superheating required for boiling heat transfer, but they also inevitably increase in flow resistance. Remarkably, the heat transfer enhancement due to the porous media increases up to a certain point and then decreases, while the flow resistance increases as the sintered layers thicken. The maximum heat transfer coefficient of the sintered tube with a sintered thickness of 0.06 mm is 1.6 times greater than that of a smooth tube. However, increasing the thickness of the porous layer does not always enhance heat transfer. The effects of different particle sizes of the sintered grains and the thickness of the sintered layers under the conditions of subcooled boiling and the onset of nucleate boiling have been analyzed to understand the physical mechanisms. An empirical heat transfer correlation has been proposed according to the experimental results for the sake of design calculation in industry.
•Hydro-thermal performance of RWVGs were studied numerically and experimentally.•The effects of β and H2/D on heat transfer and flow performance are obtained.•The maximum overall heat transfer ...performance is 1.18.•The simulation results agree well with the experimental results.•The correlations of Nu and f are given based on the numerical data.
In this paper, the heat transfer and flow behavior of a circular tube fitted with rectangular winglet vortex generators (RWVGs) are investigated numerically and experimentally with uniform heat flux boundary conditions for Reynolds number ranging from 5000 to 17,000. Water is employed as working fluid. The RWVGs are inserted into the tube, with the slant angle β of 10°, 20°, 30°, 35°, respectively. The asymmetric winglet height is set on the one side at H1/D = 0.5, and on the other side at H2/D = 0.2, 0.3, 0.4, and 0.5, respectively. The effects of β and H2/D on the heat transfer and flow behavior are studied numerically by employing FLUENT software. The results show that the RWVGs can agitate the cold fluid from the core flow region to the tube wall, and therefore, enhancing the mixing of hot and cold fluids. The Nusselt number and friction factor increase with the increase of β, or H2/D. Specifically, the Nusselt number and friction factor are increased at 1.16–2.49 times and 2.09–12.32 times, respectively, compared with the plain tube. The Performance Evaluation Criterion (PEC) increases first, and then decreases with the increase of β and H2/D. The maximum PEC is found to be 1.18 for β = 30°, H2/D = 0.5 and Re = 5000. Based on numerical data, new correlations of Nu and f by using four nondimensional parameters are also developed. The experimental platform is set up and the numerical results agree well with those of the experiment. In addition, the mechanism of heat transfer enhancement of RWVGs can be well explained by the principle of field synergy.
Simultaneous application of nanoparticles and porous media to enhance heat transfer inside an annulus is investigated numerically. Two-phase mixture model along with Darcy–Brinkman–Forchheimer ...relation has been implemented for nanofluid flow simulation in porous media. Different configurations consisting of various porous layer thicknesses, porous layer positions (at inner/outer wall of the annulus), and its permeabilities are analyzed as a function of nanoparticle concentrations and Reynolds from the view point of the first and the second laws of thermodynamics. A new PN (performance number) – defined as the ratio of enhanced heat transfer to pressure loss – is introduced to better judge the first law's performance of configurations. Results showed that the configuration's parameters, nanoparticles concentration and Reynolds number have considerable effects on both the performance and entropy generation numbers. For configurations with high permeabilities (Da = 0.1, 0.01), PN has an increasing trend with porous layer thickness; while for configurations with low permeabilities (Da = 0.0001), PN has a decreasing trend with porous layer thickness; and for configurations with a moderate permeability (Da = 0.001), an optimum thickness corresponds to PN. The study of the second law also reveals that an optimum porous media thickness exists for each nanofluid flowing in a porous medium at a specific Reynolds.
•Nanofluid and porous media are used simultaneously to enhance heat transfer.•2-phase mixture model used to simulate forced convection of nanofluid in an annulus.•Darcy–Brinkman–Forchheimer model employed for fluid flow simulation in porous media.•A new performance number introduced to better judge about first law's performance.•An optimal porous radius exists for moderate Darcy's to maximize performance number.
With recent advances in micro- and nanofabrication, superhydrophilic and superhydrophobic surfaces have been developed. The statics and dynamics of fluids on these surfaces have been well ...characterized. However, few investigations have been made into the potential of these surfaces to control and enhance other transport phenomena. In this article, we characterize pool boiling on surfaces with wettabilities varied from superhydrophobic to superhydrophilic, and provide nucleation measurements. The most interesting result of our measurements is that the largest heat transfer coefficients are reached not on surfaces with spatially uniform wettability, but on biphilic surfaces, which juxtapose hydrophilic and hydrophobic regions. We develop an analytical model that describes how biphilic surfaces effectively manage the vapor and liquid transport, delaying critical heat flux and maximizing the heat transfer coefficient. Finally, we manufacture and test the first superbiphilic surfaces (juxtaposing superhydrophobic and superhydrophilic regions), which show exceptional performance in pool boiling, combining high critical heat fluxes over 100W/cm2 with very high heat transfer coefficients, over 100kW/m2K.
The heat-transfer enhancement of nanofluids has made them attractive and the subject of many theoretical and experimental researches over the last decade. Of the theoretical approaches employed to ...investigate nanofluid properties, molecular dynamics (MD) simulation is a popular computational technique that is widely used to simulate and investigate thermophysical properties of nanofluids. In this paper, we review and discuss the MD studies conducted on the thermophysical properties of nanofluids, considering the thermal conductivity and shear viscosity as two important factors for the industrial application of nanofluids. In this study, after introducing different MD methods to calculate those parameters, we classify and review various influential effects including the volume fraction of nanoparticles, nanofluid temperature, Brownian motion of the nanoparticles, as well as the nanoparticle shape and size in terms of the thermal conductivity and viscosity of nanofluids. Viscosity has been studied to a lesser extent than the thermal conductivity of nanofluids. In our review, we note the similarities and differences between previous MD reports on nanofluids, and we highlight gaps and potential ideas that may be of interest for future studies.
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