A novel hybrid system coupled liquid dehumidification
with absorption
refrigeration driven by solar energy is proposed. Traditional and
advanced exergy and exergoeconomic analyses of the system are conducted
to ascertain the degree of irreversibility and potential improvement
for each component. Based on the advanced exergy and exergoeconomic
analyses, the effects of air humidity, segment temperature, and refrigeration
temperature on the total exergy destruction and cost rates of the
system are obtained. The total avoidable exergy destruction rate,
avoidable exergy destruction cost rate, and avoidable investment cost
rate of the system are selected as objective functions and optimized
by using nondominated sort genetic algorithm-II. The results show
that the total exergy destruction rate and the total exergy destruction
cost rate reach 262.39 kW and 8.563 $/h, respectively. The generator
and regenerator have higher cost rates of the irreversibility overall
system, achieving the values 3.536 and 2.430 $/h, respectively. The
absorber has the highest investment cost rate in the whole system.
The endogenous parts of the exergy destruction and cost rates are
much higher than the exogenous parts in the system. Multiobjective
optimization results show that optimal values for the total avoidable
exergy destruction rate and the exergy destruction cost rate are 50.99
kW and 1.60 $/h, which are 4.15 and 9.14% lower than those calculated
by single-objective optimization, respectively. This study provides
a potential way to utilize solar energy for dehumidification and refrigeration.
Foundation pit excavation is common in urban construction, while safety evaluation is always significant in every specified project. The soil material properties, groundwater level, excavation method, supporting structure, monitoring points’ arrangement, and so on distinguish from one site from another. Thus, many studies have looked into the safety and reliability of designated projects. This paper was based on the co-construction underground tunnel project of a deep foundation pit excavation in Suzhou, China. This paper aimed to perform a safety evaluation on this foundation pit by means of numerical simulation for parameter influence analysis, as well as scientific comparison with in-site monitoring data. To minimize the energy consumption and contribute to the carbon neutrality, a brief energy consumption analysis was also conducted. The results indicated that the maximum deformation of the foundation pit bottom is 4.5 cm and the deformation of the foundation pit is within the allowable range. The maximum horizontal displacement of each excavation is approximately at 10 m to 12 m of the diaphragm wall and the largest deformation is 28 mm. The maximum ground settlement is less than 16 mm, which confirmed the safety during excavation. It is ideal that the above deformation law will provide a reference for similar projects. Furthermore, this research simulated and monitored the whole cycle of foundation pit excavation, and contributes to savings in energy consumption and limiting of carbon emissions.
In geological engineering, a series of safety problems caused by expansive mudstone are common, such as slope instability and roadbed up-arch. In this paper, the mineral composition of mudstones in the Xining area was analyzed by X-ray diffraction (XRD), and the microstructural and morphological changes of mudstones after water absorption were observed by scanning electron microscopy (SEM) test to analyze the internal factors and microstructural evolution patterns of water absorption and swelling of mudstones. Based on the microstructural units, the mudstones were defined into two categories, one is N-type mudstone with flat sheet-like stromatolite units, and the other is SN-type mudstone with more clastic particle units. Water absorption experiments were conducted on the rock samples to study the microstructure of these two types of mudstones under different water absorption conditions. The pore characteristics of the mudstones were analyzed by using Image-Pro Plus to reveal the water absorption mechanism. The results show that the pore area of N-type mudstone is smaller, as well as the distribution of pore diameter. The pore area of N-type mudstone develops rapidly, in the early stage of water absorption, lots of pores are produced, and the pore area of SN-type mudstone shows an overall decreasing trend. The pore area and the number of SN-type mudstones are at a low level after full water absorption. Under the condition of full immersion, water enters the pores rapidly and soluble salts are dissolved in large quantities. The change of water absorption rate of mudstone with time can be divided into the stage of sudden increase, decrease and stability of water absorption rate. Then, based on the stress theory, the relationship between the macroscopic expansion process and the microstructure of mudstone was analyzed. Finally, the energy basis of mudstone water absorption is discussed. In the swelling of mudstone, the energy gradually turns into swelling strain energy.
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