In this paper, a curved wavy channel was proposed to further enhance the thermal performance of the conventional wavy channel. A three-dimensional model of the curved wavy channel was established with defining the overall curvature. The flow behavior and heat transfer in the wavy and curved wavy channels were numerically investigated under various wave amplitudes. The mechanism behind the observed phenomena was revealed by analyzing the synergy between velocity and temperature fields. The results indicated that the Nusselt numbers in curved wavy channels with amplitudes of 0.40 mm and 0.80 mm can be raised by 44.3% and 15.3% compared to those in conventional wavy channels. The parametric study showed that the flow resistance is more sensitive to the wavelength. For a given amplitude, curved wavy channels always show a better field synergy than conventional wavy channels. In addition, an inferior field synergy was observed near the suction side in both types of wavy channels, which indicates that the purposive improvement needs to apply to these locations. This study also found that the field synergy angle has limitations in characterizing the heat transfer intensity in the channel with small wavelengths. This is because that extremely chaotic flow patterns caused by small wavelengths result in a negative dot product of temperature gradient and velocity over a large area.

Spiral channels are widely used as the core heat exchangers in latent thermal storage units. This study aims to develop a novel spiral channel characterized by wavy sidewalls for high-efficiency convective heat transfer in tube side. The amplitude of the wavy sidewalls is designed to grow from the inlet to the outlet along flow direction. The thermal characteristics in the spiral-wavy channel were numerically investigated under the boundary condition of constant wall temperature, since latent heat storage units mainly work under isothermal condition. The comparison was carried out between a smooth-spiral channel and a spiral-wavy channel in terms of the heat transfer capacity, friction factor, dimensionless temperature distributions and development of boundary layers. At a given heat transfer rate, the required length of the spiral-wavy channel is only 63.5% of that of the smooth-spiral channel, which implies that the energy density and efficiency of a heat storage unit can be improved remarkably. The increase in pressure drop brought by the spiral-wave channel is less important compared with the improvement of thermal performance, suggesting its potential in heat transfer enhancement and energy saving. The present work is expected to motivate the design of compact and high-efficiency heat exchangers for thermal energy storage and extraction.

As the most commonly used power battery in electric vehicles, lithium-ion battery is sensitive to the operation temperature. The performance and lifespan of lithium-ion battery are strongly dependent on its working temperature. Various thermal management systems have been developed to maintain batteries’ operating temperature within an appropriate range. A properly designed thermal management system relies upon the understanding of battery’s heat-generation characteristics and the temperature effect on its discharging performance. In this research, an experimental investigation is carried out to study the electro-thermal characteristics of the commercial prismatic ternary lithium-ion battery under three thermal conditions. Constant temperature condition is built to explore the effect of the operating temperature, while near-adiabatic condition and natural-convection condition are employed to study the heat-generation characteristics of lithium-ion battery. The results show that the effect of operating temperature on discharge performance becomes more pronounced as the discharge rate increases. It is found that the surface temperature decreases when the battery discharges at small rates within the capacity ranged from 17Ah to 27Ah, demonstrating that the reversible heat makes up a large proportion of battery heat generation.

The effective thermal conductivities (ETCs) of porous electrodes in electrolyte are of rather significance for determining the thermal conductivity of Li-ion battery which is an important factor in designing battery thermal management system and predicting battery thermal behaviour. In this study, the representative Li-ion battery consisting of a Li(NiCoMn)O2 positive electrode and a graphite negative electrode was chosen to explore the ETCs of porous electrodes. The effects of ETCs of porous electrodes on the Li-ion battery’s thermal conductivity were firstly discussed, and the ETCs were analysed based on its internal configuration and basic assumptions. Most importantly, the ETCs bounds of porous electrodes were acquired using basic thermal conductivity models and the limits of ETCs were obtained based on Maxwell 2 model combined with volume fractions of electrolyte. The results show that the ETCs of porous electrodes in electrolyte are obviously lower than the thermal conductivities of active materials, namely Li(NiCoMn)O2 and graphite. In addition, the ETCs of porous electrodes are not constant but variable values caused by the variation of volume fractions of electrolyte in porous electrodes which indicates that the volume fractions of electrolyte should be considered for accurately estimate the thermal conductivity of commercial Li-ion battery.

Heat transfer rate in curve channel decreases with channel curvature since the secondary flow turns weak with the decrease of centrifugal force. In this paper, the periodical wave wall structure is introduced into curve channel for improving heat transfer rate in the curve channel with small curvature. The channel radius is not constant anymore but varies periodically based on a cosinoidal function. Three-dimensional numerical investigation was carried out to explore the flow and heat transfer characteristics in the curve-wave channel, and the effects of wave frequency and average curvature on the heat transfer performance were analysed. The results show that the heat transfer rate in curve channel can be improve up to 95.50% due to the periodical wave wall structure, while the friction factor increases by 53.94%. The effect of periodical wave wall structure gets obvious with the increase of Re. Heat transfer in curve-wave channel can be further enhanced by increasing wave frequency of channel wall. In addition, the effect of wave wall structure on heat transfer is dependent on the overall curvature of curve-wave channel and stronger for larger-curvature curve-wave channel. The performance factors of all the curve-wave channels are almost above 1, indicating that this structure can be used as an economic passive heat transfer enhancement method.

Flow and heat transfer in curve channel have been studied extensively due to the presence of the secondary flow induced by the centrifugal force. However, for the curved channel with small curvature, weakened centrifugal force reduces the intensity of secondary flow and heat transfer enhancement is attenuated accordingly. For sake of maintaining high heat transfer efficiency in curve channel with a wide range of curvature, periodical wave structure was introduced into the smooth-curve channel by this study. A three-dimensional model of the curve-wave structure was established and numerical simulation was carried out to explore the flow characteristics and heat transfer performance in the proposed channel. In addition, the effects of the wave amplitude on the channel performance were analyzed. The results showed that the heat transfer of smooth-curve channel can be enhanced remarkably by applying wave structure on the channel wall, and the overall performance factor indicates that the heat transfer argumentation outweighs the pressure loss penalty. It was also found that the heat transfer in the curve wave channel can be further enhanced by increasing wave amplitude. The most effective heat transfer enhancement can be achieved based on the evaluation of the overall performance factor. (C) 2019 Elsevier Ltd. All rights reserved.

The relationship between lithium-ion battery performance and operating temperature is of significance in designing battery thermal management system (BTMS). In this study, two different thermal conditions, namely constant temperature condition and near-adiabatic condition are established to explore charging/discharging characteristics and heat generation behaviors of the lithium-ion battery with Li(NixCoyAlz)O-2 cathode. The objective of creating near-adiabatic condition is to discover the effect of the heat generated by battery itself on charging/discharging characteristics. The experimental results show that the battery charging characteristics are nearly independent on the charging temperature ranged from 20 degrees C to 40 degrees C, while the battery charging/discharging performance degrade dramatically for the battery temperature lower than 20 degrees C. Although the heat generated by battery itself may accelerate battery degradation during cycling due to the adverse effect of excessive temperature, however it improves the discharging performance in a suitable temperature range. This implies that a battery pack may have an excellent discharging performance without BTMS intervention at a moderate discharging rate (e.g., 0.5 C). The irreversible heat could be regarded as the sole heat source term to simplify the battery thermal model due to negligible thermal effect caused by the small amount of reversible heat when the battery is discharged at higher discharging rates.

The lithium ion battery has been widely applied in the fields of electric vehicles and electronic products due to its advantages of high power density, long lifespan and low self-discharging, etc. In this study, two lithium ion batteries are adopted to explore the effects of different thermal conditions on battery’s performance. One of thermal conditions makes battery close to adiabatic condition similar to the thermal condition of battery pack without any thermal management system. Another thermal condition is constant temperature condition employed to simulate the thermal condition of battery pack with thermal management system. The experimental results show that (i) next chargeable capacities of these batteries are dependent on the previous dischargeable capacities for all thermal conditions; (ii) dischargeable capacities of these batteries markedly decrease with the increase of the discharge rates under 20°C constant temperature condition; (iii) dischargeable capacities are independent on discharge rates under close to adiabatic condition because the obvious battery temperature rise can offset the adverse effects of higher discharge rates on battery’s performance. Although higher battery temperature is conductive to weaken or eliminate the adverse effects of higher discharge rates, excessively high temperature can also accelerate battery aging and easily cause battery thermal runaway, which indicates that it is necessary for battery pack with thermal management system to control thermal conditions of batteries.

•Natural convection in melt phase causes a remarkable promotion of melting interface evolution.•LHTES unit with annular fins exhibits promising potential for enhancing melting heat transfer.•An optimal group fin parameter is recommended towards maximizing phase change heat transfer.•Fins should be equipped with proper design other than excessive numbers to maximize heat transfer.

Latent heat thermal energy storage (LHTES) is a promising way to smooth the discrepancy between energy supply and demand, and it is now becoming increasingly significant in the heating and cooling of buildings. However, the low thermal conductivity of the available PCMs require more efficient configuration of LHTES system in reducing the melting time. In order to evaluate the dynamic thermal performances of LHTES unit in shell and tube heat exchanger, the two-HTF-passage configuration and single-pass configuration are numerically investigated. The results show that the central and annular injection in two-HTF-passage configuration has little influence on the transient melting interface location and temperature in the PCM domain and both can effectively enhance the phase change heat transfer, but the HTF tube injection in single-pass configuration shows a significantly poor performance.

The modern development of electric vehicle requires higher power density to be packed into a battery pack. It is always expected that the battery can be arranged as much as possible, however, which leads to the serious thermal management issue due to the heat generation inside the battery packs. As extreme temperature affects performance, reliability, safety and lifespan of batteries, thermal management of battery system is critical to the success of all electric vehicles. The objective of this study is to explore the air cooling capability on the temperature uniformity and hotspots mitigation of a compact battery pack subject to various air flow paths, airflow rates. The numerical results show that the improvement of effective heat transfer areas between air-coolant and battery surfaces is able to obviously lower the maximum temperature and improve the maximum temperature difference in the densely-packed battery box.

The unearthed relics in archaeology museum are usually being presented to the public as still partly connected to their primitive environment. Migration of moisture may cause the carbonate from the soil being deposited on the relic’s surface and some carbonates would react with the penetrating SO2 to form sulphates, which will change the relics’ primitive form and material properties. In this research, experiments were carried out to clarify the migration mechanism of water and salt in a soil-relic-atmosphere coupling environment. The research results show that there existing a one-way transport of moisture from the soil-relics to the air even though the relative humidity approximates to 100%. Meanwhile, the effects of soil properties, air temperature, relative humidity and salt concentration on the transports of moisture and salt are identified.

Due to the characteristics of large surface area-to-volume ratio and inter-connected ligament structure, open-cell metal foams are promising materials for enhancing heat transfer in forced convection and have been researched for thermal applications in thermal management systems, air-cooled condensers and compact heat sinks for power electronics. However, the tortuous complex flow path inside metal foams leads to relatively higher pressure drop, which requires larger system pumping power. Hence, it is important to study the heat transfer performance of metal foam compared to its flow resistance characteristics. Detailed experimental study of forced convection subjected to constant heat flux in metal foams is conducted in the present paper. The objective of the investigation is to compare the heat transfer performance and hydraulic characteristics of aluminum foams with different pore densities. The tested aluminium foam samples are of 50.0mm (L) × 25.0mm (W) × 12.0mm (H) in geometric dimensions and pore densities are of 5ppi, 10ppi and 40ppi, respectively. Experiments are performed in forced convective heat transfer using deionized water as the cooling fluid. To minimize the heat loss, the test section is built adiabatically with Teflon and polycarbonate materials. The inlet flow velocity, the temperature distribution on the heating surface and the pressure drop across the metal form are measured. Based on the analysis of experimental data, it is found that convective heat transfer performance in high ppi foam is higher than that in low ppi foam, while the pressure drop shows the opposite trend for a given flow rate.

Many forms of electronic equipment, of necessity, must be located in an outdoor environment. Such equipment in typical form may be battery packs or telecom-equipment. It is essential that these facilities be protected from a wide range of ambient temperatures and solar radiation. To this end, cabinet enclosures with proper thermal management have been developed to house such electronic equipment in a highly weather tight manner, especially for battery cabinet. Often the batteries are of a lead-acid construction which is known to be adversely affected by temperature extremes in terms of battery performance and life. Therefore, it is important to maintain the cabinet temperature ideally for ensuring battery stability and extending battery lifespan. In this paper, physical and mathematical models are established to investigate the flow field and temperature distribution inside an outdoor cabinet, which contains 24 batteries with two configurations of two-layer and six-layer respectively. The cabinet walls are maintained at a constant temperature by a refrigeration system and the ambient temperature is up to 50 °C according to the practical situation. The flow field and temperature distribution are analyzed with and without consideration of solar radiation. An experimental facility is then developed to measure the battery surface temperatures and to validate the numerical simulation. The differences between the CFD and experimental results are within 2%, which confirms the CFD model.