https://www.mdu.se/

This study focused on the effect of inserting fins into metal foam on the solidification rate. To this aim, a well-designed experimental system with solid-liquid interface visualization was built. Metal foam samples with different fin intervals were prepared for experiments. Solidification process of water saturating in finned metal foam under bottom cooling was experimentally investigated. Results showed that inserting fins into metal foam can make a promotional improvement on solidification rate of water. The solid-liquid interface became curved after inserting fins, compared with metal foam sample without fins. Besides, changing the interval has little effect on the solidification rate.

This study presented an experimental investigation on solidification behavior of fluid saturated in highly porous open-cell copper foams. Particular attention has been made on the effect of pore parameters (pore density and porosity) on the solidification behavior. A purposely-designed apparatus was built for experimental observations. Results showed that the copper foam had a great effect on solidification and the full solidification time can be saved up to 50%, especially preventing the decrease in solidification rate during the later stage of phase change. The smaller the porosity is, the faster the solidification rate will be. Pore density was found to have little influence upon the solidification rate. In addition, the local natural convection does exist but it has a slight effect on solidification, leading to the slant of the solid-liquid interface. 

Industrial parks play a crucial role as a carrier of industrial clusters and energy consumption. Accurately predicting the energy demand and carbon emissions trend is key to scientifically determining the pathways for low-carbon industrial parks. However, exploration in carbon emission prediction on industrial park scale is still in its infancy stage. This paper investigates fuel demand and carbon emissions from 2021 to 2035 in an industrial park in Jiangsu Province, utilizing the Long-range Energy Alternative Planning (LEAP) model to explore the pathways for low carbon development. Energy-saving and emission-reduction effects of different macro-economic policies and micro-energy planning are analyzed based on the energy balance and emission factor methods. Four scenarios are compared: the baseline scenario (BAS), green development scenario (GDS), low carbon scenario (LCS), and strength low carbon scenario (SLS). Results indicated that energy demand under BAS reached at 31.37 Mtce in 2035, and energy-saving rates of GDS, LCS, and SLS in 2035 were 12.94%, 14.00% and 19.08%, respectively. Carbon emissions reached 53.96 MtCO2e in BAS of 2035. However, in the same year, emissions decreased by 24.88%, 43.09%, and 52.52% in GDS, LCS, and SLS, respectively, with SLS being the most suitable for the park.

Due to the intermittency and discontinuity of solar energy, thermal energy storage (TES) using phase change materials (PCMs) is generally required to ensure stable operation in solar heating systems (SHS) during winter. This paper presents the design of a TES unit with different horizontal metal foam filling ratios (60%–100%), and simulations of thermal characteristics, such as complete melting time and heat storage capacity by numerical method. Based on the heating demands of an office building in Xi'an, TES units are combined in parallel and economic indexes are calculated based on static evaluation method, including initial investment and investment payback period. Novelty, the contribution of gradient microstructure to the phase transition process is evaluated from thermophysical properties and economy. Results show that the TES unit with a filling ratio of 90% possesses the shortest complete melting time of 5310 s, which is 87.56% shorter than that of a TES unit with pure PCM. Finally, economic assessments of the engineering application of the partially filled metal foam structure are carried out, and it is determined that the SHS with the TES system of 90% filling ratio requires the least number of 548 TES units, with a payback period of three heating seasons. 

This study presented experimental investigations on the thermal performance of a thermal energy storage (TES) unit with coil tubes. A designed test rig was built and the melting heat transfer characteristics (melting front and temperature distribution) inside the TES unit were examined. The effects of charging flow rate on the overall phase change process were examined. The results showed that natural convection accelerated the thermal energy transport in the melt phase in the top region, but weakened the heat transfer in the bottom region; this resulted in the unmelt PCM at the bottom. The melting heat transfer was overall enhanced by the increase in inlet flow rate, indicating that the full charging time can be shortened by a larger flow rate. 

Thermal energy storage (TES) has been playing a crucial role in addressing the issue of solving the intermittent and random problems in solar energy utilization. The objective of this study is to squarely address and clarify the contribution of metal fin and foam to enhancing the phase change heat transfer by experiments. A novel hybrid fin-foam tube is proposed and its thermal performance is evaluated by experimentally comparing with other three competing structures including bare, fin, and metal foam tubes. A well-designed test rig is built and the energy storage features for the designed four TES tubes are analyzed by the complete melting time, melting front evolution, temperature variation and uniformity, and the temperature response rate. Results show that the fin-foam hybrid structure outperforms the other competing ones, demonstrating a reduction of 83.35% in complete melting time (compared with the bare tube). The transient temperature response is maximized by 529.1%. As for the single structure, both fins and metal foam can improve conductivity of phase change materials. The metal foam does a good favor to improve the uniformity of the temperature field inside the TES tube, but the fins weakened the uniformity. If the design target is temperature uniformity, adding metal foams other than fins can fulfil the task.

This study provides an alternative solution to the improvement on solid–liquid phase change by designing a Y-shaped fin in a nonuniform pattern along the gravity direction. A numerical model is established and validated through the present measurement and data in literature. Six cases with different Y-shaped fins and locations are designed and compared to the original straight fin case. Thermal assessments on the melting fraction, temperature field, velocity distribution, and uniformity for melting are made. Results demonstrate that the nonuniform melting features caused by the local natural convection are significantly eliminated by the novel nonuniform fin structure. The time required for melting the lower PCM is found to occupy more than 50% of the completely melting time. The accurate local heat transfer enhancement measures (bottom enhancement) are conducive to markedly reduce the full melting time by 21.5%, compared to the uniform fin pattern. Upon using finned thermal storage tank for a mobilized thermal storage truck (bare tube tank), the initial investment increases by 44.9% but the profit increases by 393.6% and the payback period reduces by 69.2%. The use of fin tube in heat storage tank can quickly obtain higher returns based on a small increase in initial investment. This work provides new insights into the understandings of the transient phase change process and the strategies for guiding the design for thermal energy storage tank. 

It is universally acknowledged that climate change brings widespread attention to solar greenhouse plant carbon sequestration. Suitable technologies in solar greenhouses were, are, and will be play a leading role in this vital transition. The primary aim of this research is to examine the energy efficiency and carbon sequestration potential of a solar-assisted ground-source heat pump (SAGSHP) heating system. This hybrid system, which integrates a horizontal ground-source heat pump (GSHP) system with PVT and heat storage, can efficiently fulfill the heating demands of a greenhouse and function as a positive energy building. Four plants include cucumber, tomato, cowpea, and lettuce were selected to compare the carbon absorption effects. Results show that the hybrid system outperforms conventional systems, with a coefficient of performance (COP) of 6.71 during peak hours and PVT efficiency over 57.88%, which effectively meet the heat load of the greenhouse and keep the indoor heat comfortable. In addition, for the carbon sequestration potential of four plants, tomato exhibited the highest photosynthetic carbon sequestration of 3522 kgCO2·m−2. Cowpea showed the strongest daily carbon sequestration capacity at 26.86 gCO2m−2d−1 and better economic income. Through the application of this enhanced solar greenhouse, people can enhance the utilization of solar energy, establish flexible interaction between energy and information flow, and make a promising option for sustainable building design. 

This work presented experimental investigations on the thermal energy storage performance of the shell and tube unit with composite phase change materials (PCM). A cylindrical heat storage tank filled with open-cell copper foam was proposed and its melting process characteristics were studied. A designed test system was established to record the PCM real-time temperature data. The results showed that, compared with traditional smooth-tube phase-change heat exchangers, the composite PCM unit accelerated the bottom paraffin melting. The temperature disparity among different height reduced, which resulted in better internal temperature uniformity. Due to the expanded heat transfer area, improved heat transfer coefficient and weakened natural convection, the bottom phase-change materials in the composite-PCM heat-storage unit melt faster. 

Due to the strengths on compact structure and continuously operating ability, a rotary wheel device in rotating packed-bed configuration for adsorption process based on temperature swing has been proposed to achieve CO2 capture in engineering application. The 3D simulations of the rotary adsorption wheel for post-combustion CO2 capture based on non-equilibrium model have not been reported. In this study, considering the non-equilibrium of heat and mass transfer, the mathematical modeling was performed for temperature swing adsorption process in the rotary bisectional adsorption wheel for the cooling-and-feeding process and rinsing-and-heating process. Comparison with the experimental breakthrough data on the fixed packed-bed was performed to validate the model. Distributions of temperature and mass fraction in the rotary adsorption wheel were obtained in three dimensions, based on which a reasonable arrangement of fluid ducting should be set to meet the different concentration requirement of CO2 capture. There is an optimal rotating speed to make the adsorption-outlet N-2 concentration as high as possible and the desorption-outlet N-2 concentration as low as possible. Whether considering the adsorption enthalpy or not in the model can greatly impact the heat and mass transfer characteristics of rotary adsorption wheel. The effects of other parameters including particle size, porosity and adsorbent materials will be further analyzed in the future study.

Melting heat transfer in open-cell metal foams embedded in phase-change materials (PCMS) predicted by the volume-averaged method (VAM) was systematically compared with that calculated using direct numerical simulation (DNS), with particular attention placed upon the contribution of natural convection in the melt region to overall phase change heat transfer. The two-temperature model based on the assumption of local thermal non-equilibrium was employed to account for the large difference of thermal conductivity between metallic ligaments and PCM (paraffin). The Forchheimer extended Darcy model was employed to describe the additional flow resistance induced by metal foam. For the DNS, a geometric model of metal foam based on tetrakaidehedron cells was reconstructed. The DNS results demonstrated significant temperature difference between ligament surface and PCM, thus confirming the feasibility of local thermal non-equilibrium employed in VAM simulations. Relative to the DNS results, the VAM combined with the two-temperature model could satisfactorily predict transient solid-liquid interface evolution and local temperature distribution, although pore-scale features of phase change were lost. The presence of natural convection affected significantly the melting front shape, temperature distribution and full melting. The contribution of natural convection to overall phase change heat transfer should be qualitatively and quantitatively given sufficient consideration from both macroscopic (VAM) and microscopic (DNS) point of views. Besides, practical significance and economic prospective using metal foam in TES unit for WHR system to provide residential heating or hot water is discussed and analyzed.

Thermal energy storage (TES) can effectively recover thermal energy from low-temperature waste heat and it has now been received increasing attentions in practical engineering applications. Nevertheless, the relatively low thermal conductivity of engineering available phase change materials (PCMs) greatly limits the energy efficiency of TES applications. To enhance the phase change process, open-cell metal foam with a porosity of 0.94 and pore density of 15 PPI (pore per inch) was employed to be inserted either in heat transfer fluid (HTF) or in phase change material (PCM). A two-dimensional axis-symmetric problem was numerically solved and was validated through comparing temperature history at selected points. Results demonstrated that the involvement of open-cell metal foam can effectively enhance the phase change heat transfer, greatly reducing the full melting time. By comparing the four cases (without metal foam, inserting metal foam into HTF, PCM and both domains), the case that both HTF and PCM domains were embedded with porous media can provide the best heat transfer enhancement, from which practical applications with thermal engineering may benefit.