Experimental Investigation of a Domestic Refrigeration Appliance Based on Exergy Destruction

Since refrigeration appliances consume more than 15% of electrical energy over the globe, many solutions have been proposed to enhance the efficiency of these appliances. However, the solutions mostly rise the expenditure and complexity of the appliances, making these methods less feasible for manufacturing. Therefore, some inexpensive and less complicated modifications should be proposed to enhance the efficiency and performance of the appliances affordably. This paper presents a new solution using unutilized cooling capacity of evaporator for cooling compressor. The experimental exergy analysis of a domestic refrigerator in which the suction pipe absorbs heat from the compressor shell illustrates a 12.64% reduction in total irreversibility, as well as a 5% and 4% of increase in cooling capacity and coefficient of performance, respectively. Moreover, the appliance with the modified cycle needs 18.2% less refrigerant than the normal design. This idea would be an affordable and practical way to enhance the efficiency of refrigeration appliances as well as decrease the manufacturing costs. This study proposes recommended design guidelines for more efficient refrigeration appliances to be used in designing compressors

Multi-objective optimization of a plate heat exchanger thermal energy storage with phase change material

The plate heat exchanger thermal energy storage system is recognized as a highly efficient form of latent heat thermal energy storage. However, existing studies show that the efficiency and performance of these thermal energy storage systems are significantly affected by the design variables, indicating the need of optimization studies. This investigation thus conducts a response surface modeling analysis based on validated computational fluid dynamics simulations. Four design variables of the system are identified, and through response surface modeling the values of five responses such as average power and average effectiveness are predicted within the defined range of the design variables. A multi-objective optimization model then determines the optimal configuration of design variables for all responses, based on the response surface modeling and validated simulations. The results indicate that the optimal design has 21.4 % higher effectiveness than the normal design. The system also achieves maximum performance by employing 5 mm of the phase change material section thickness considering all the efficiency parameters. Moreover, charging the system over 10 °C above the PCM's melting temperature significantly decreases efficiency while providing minimal enhancement to power.Peer reviewe

Numerical investigation of a plate heat exchanger thermal energy storage system with phase change material

Plate-type thermal energy storage systems (PTESs) have been proposed to mitigate the effect of the low thermal conductivity of phase change materials on the performance and efficiency of thermal energy storage systems. Nevertheless, a prompt reduction in the thermal power of PTESs due to the drop/rise in the outlet temperature at the early stage of the charging/discharging process has not been well resolved. To remedy this, the current study proposes a modified PTES and presents a computational fluid dynamics model of this PTES for performance and efficiency analysis. The results show that the outlet temperature of the modified PTES is constant for 100 min in the melting and 33 min in the solidification processes, while this temperature drops/raises almost immediately in the similar PTESs after starting these processes. In addition, the presented PTES shows an improvement of 75 % and 28.6 %, respectively, in the energy storage capacity per unit volume and effectiveness than a roll-bonded PTES.publishedVersionPeer reviewe

Sub- and Supercritical Water Liquefaction of Kraft Lignin and Black Liquor Derived Lignin

To mitigate global warming, humankind has been forced to develop new efficient energy solutions based on renewable energy sources. Hydrothermal liquefaction (HTL) is a promising technology that can efficiently produce bio-oil from several biomass sources. The HTL process uses sub- or supercritical water for producing bio-oil, water-soluble organics, gaseous products and char. Black liquor mainly contains cooking chemicals (mainly alkali salts) lignin and the hemicellulose parts of the wood chips used for cellulose digestion. This review explores the effects of different process parameters, solvents and catalysts for the HTL of black liquor or black liquor-derived lignin. Using short residence times under near- or supercritical water conditions may improve both the quality and the quantity of the bio-oil yield. The quality and yield of bio-oil can be further improved by using solvents (e.g., phenol) and catalysts (e.g., alkali salts, zirconia). However, the solubility of alkali salts present in black liquor can lead to clogging problem in the HTL reactor and process tubes when approaching supercritical water conditions

Pelvic floor disorders and health-related quality of life in older women : Results from the Women's Gynaecological Health study in Lieto, Finland

Objective: The aim of this study was to analyse the prevalence of pelvic floor disorders and to describe health-related quality of life (HRQoL) among older women. We also compared participants' HRQoL with the age-matched general female population and analysed factors associated with HRQoL. Study design: This is a population-based study of a cohort of women born in 1948 and in 1950 (n = 143) which is also part of the Women's Gynaecological Health study in Lieto, Finland. Methods: The data were collected by questionnaires which pertained to socio-demographics, health-related variables, pelvic floor disorders and HRQoL (15D). Linear model was conducted to estimate a model of factors that associated with HRQoL. Results: The prevalence of urinary incontinence, faecal incontinence and pelvic organ prolapse was 50%, 13% and 12%, respectively. The overall HRQoL score of the study cohort is broadly similar to that of the age-matched general Finnish female population (mean +/- SD15D scores 0.905 +/- 0.084 vs 0.912 +/- 0.077). Higher number of medications was the most important explanatory factor for lower HRQoL. Conclusion: Urinary incontinence was common; however, the impact on HRQoL was minor. The overall HRQoL score of the study cohort was broadly similar to that of age-matched general female population. Women who used a higher number of medications had lower HRQoL compared to women who used fewer medications.Peer reviewe

Improving inorganic composition and ash fusion behavior of spruce bark by leaching with water, acetic acid, and steam pre-treatment condensate

The present study evaluates the effect of water and acetic acid washing on the chemical composition of spruce bark in-depth. Also, washing with steam explosion condensate (SEC) was investigated which is a novel attempt. The leaching kinetics of troubling elements (TE) was studied to understand the leaching behavior of TEs and for upscaling the process. Furthermore, to study the ash transformation behavior of TEs in pre-treated and raw bark at high temperatures (500–1500 °C), thermodynamic equilibrium modeling (TEM) was also performed. The result of washing pre-treatment shows high removal of TEs: 22–97% Na, 46–82% Cl, 14–79% K, 14–65% Mg, 25–50% S, 3–22% Ca, 12–36% P, 3–43% Si, and 6–35% N. Continuous removal of TEs was seen with increasing washing duration where most of TEs followed a second-order leaching kinetics. Acid washing results in a much higher and quicker removal for all TEs than water washing. Due to the acidic nature of the SEC, it shows similar removal of TEs as the 0.1 M acetic acid solution. TEM reveals that the transformation behavior of TEs in bark changes considerably after pre-treatment. Pre-treated bark shows the formation of fewer problematic compounds responsible for fouling, slagging, and corrosion at typical gasification and combustion temperatures, such as KCl, K2SO4, K2CO3, KOH, Na2SO4, NaCl, and K-, Na-, P-, and Ca-slag. Though best washing efficiency was seen for longer washing durations, 10 min washing with 0.1 M acetic acid or SEC may be adequate for practical applications.publishedVersionPeer reviewe

Ash chemistry in chemical looping process for biomass valorization : A review

Chemical looping process (CLP) is a novel carbon capture technology for biomass valorization. Low-cost and robust oxygen carrier (OC) is crucial for industrialization of CLP. However, ash in solid fuels will unavoidably deposit on OC and even react with OC, leading to severe agglomeration and sintering which could not only degrade the full functionality of OC but also make the complete separation of ash and OC challenging. In order to holistically elucidate the ash chemistry in CLP, this review has systematically analyzed the effect of ash compositions in biomass on CLP efficiency, the impact of ash components on physicochemical properties and oxygen transfer capacity of OC, as well as the melting and agglomeration behaviors of ash components. Specifically, both inhibition and enhancement effects of various ash components have been illustrated. Particularly, the influence of alkali and alkaline earth metals in biomass ash on agglomeration of OC has been analyzed in detail. Four mechanisms are summarized to explain the agglomeration and melting process, including coating-induced, melting-induced, ash deposition-melting, the layer joint and bridge joint mechanisms. Ultimately, strategies are proposed to effectively mitigate adverse impacts of ash and recycle useful metals for industry use and re-synthesis of OC. To promote future development of CLP, perspectives are provided to guide the novel design of next generation OC in terms of structural and compositional optimization.Peer reviewe

The effect of metal dissolution on carbon production by high-temperature molten salt electrolysis

High-temperature molten salt electrolysis is suitable for the production of carbon morphologies such as carbon nanotubes and nano-onions. In this study, CO2 was electrochemically reduced to solid carbon by molten lithium carbonate electrolysis in an Inconel 625 vessel at a fixed temperature of 750°C. Four different cathodes (clean nickel, used nickel, stainless steel, and galvanized steel) were used to determine the effect of the electrode material on the morphology produced. The carbonaceous products obtained were analyzed with scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), Raman microscopy, and X-ray diffraction (XRD). With nickel cathodes, the dominant forms of carbon were spherical, whereas tubular structures dominated with steel-based cathodes. Nano-onion was the structure of carbon with the least metal impurities. Iron was discovered to promote carbon nanotube growth. In the presence of iron, nanotube wool was also found. A greater number of different morphologies were observed when the amount of metal impurities increased. The correlation found between XRD results and sample masses suggests that the amount of metal impurities in the sample varied more than the carbon content. Thus, the yield of the process can be expected to be fairly similar between parallel experiments.publishedVersionPeer reviewe

Effect of different washing parameters on the fuel properties and elemental composition of wheat straw in water-washing pre-treatment : Part 1: Effect of washing duration and biomass size

Washing pre-treatment significantly improves the fuel properties and composition of agricultural residues, though still requires further development before being applied on the industrial scale. So, to improve the efficiency of the washing pre-treatment, four basic parameters were modified in the present study, and presented in two separate and consecutive articles as Part 1: washing duration and biomass size; and Part 2: washing temperature and solid-to-liquid (S:L) ratio. In Part 1, to evaluate the effect of washing duration and sample size, three different sample sizes of wheat straw were used – 3 cm, 1 cm, and 0.05–0.08 cm, and each size was washed for 0 min, 2 min, 5 min, 10 min, 30 min, 60 min, and 180 min. The biomass composition, heating values, energy loss, and fouling and slagging propensity were evaluated for both treated and untreated samples. As a function of increasing the washing time and reducing the sample size, continuous improvements in fuel properties and fouling and slagging propensity were observed. Washing for longer durations shows best improvement in fuel properties, with a much lower fouling and slagging tendency due to the high removal of potassium (up to 68%), chlorine (up to 87%), sulphur (up to 74%), nitrogen (up to 46%), and ash (up to 39%). For biomass size, smaller sizes resulted in better washing efficiency, while larger sizes showed similar trends in washing. As shorter washing durations and a larger sample size are more favourable for industrial applicability and show considerable improvement, such cases were further modified by varying the temperature and S:L ratio (presented in Part-2).publishedVersionPeer reviewe

Effect of different washing parameters on the fuel properties and elemental composition of wheat straw in water-washing pre-treatment : Part 2: Effect of washing temperature and solid-to-liquid ratio

The present work is the second part of a study conducted to evaluate the effect of basic parameters on the efficiency of water washing pre-treatment. As per the results of Part-1, large sizes and shorter washing durations are favourable for industrial applications, yet low to moderate fouling and corrosion can be expected from them on combustion. The aim of the present study was to further improve the efficiency of the washing pre-treatment for rather short washing durations (5 and 10 min) and a large feedstock size (3 cm) by optimizing the temperature and solid-to-liquid (S:L) ratio. The washing temperatures considered were 20 °C, 40 °C, 60 °C, and 80 °C, while the S:L ratios considered were 1:15, 1:20, 1:30, 1:40, and 1:50. Fuel composition, heating values, energy loss, and fouling and slagging propensity were evaluated. Increasing the washing temperature resulted in the greater removal of ash (25–37%), K (42–55%), Cl (60–81%), S (32–61%), Mg (52–68%), N (17–25%), P (11–37%), and Ca (14–29%). On increasing the S:L ratio, improvement in the removal of ash (27–35%), Cl (73–84%), S (41–59%), and N (21–40%) was also observed. For practical applications, an S:L ratio of 1:15 was found adequate compare to higher S:L ratios. The washing of 3 cm sized wheat straw for 10 min at 40 °C with a 1:15 S:L is recommended for industrial applications, as it shows the least fouling propensity and energy loss.publishedVersionPeer reviewe