Low-temperature Applications Research Articles

Dion-Jacobson perovskite solar cells: Further optimize the performance by SCAPS-1D simulation techniques

With rising global energy demands and the emergence of novel energy forms, perovskite solar cells (PSCs) are becoming increasingly prominent due to their exceptionally high efficiency in converting power. The advantage of Dion-Jacobson (DJ) type 2D layered perovskite materials lies in their lack of interlayer van der Waals forces, coupled with hydrogen bonds at the extremities, necessitating additional external energy to break through their two-dimensional layered configuration, thereby greatly enhancing the materials' structural integrity. This study utilizes DJ type 2D layered perovskite material to tackle the stability problem. This study aimed to uncover the inherent effects of DJ type 2D perovskite substances by simulating the devices with SCAPS-1D (Solar Cells Capacitance Simulator) and modifying appropriate physical parameters to align closely with the outcomes reported in experiments. Simulation results indicate that factors such as the thickness of the absorber layer, the band gap, the operating temperature, and the thickness of the interfacial defect layer uniquely influence the device's performance. The optimal thickness for the absorbing layer was determined by its ability to absorb light. The aim is to boost the sensitivity of DJ type 2D layered perovskite materials to light across various wavelengths and to refine the PCE. During the simulation, the maximum PCE (26.57%) was attained by enhancing both the band gap width in the absorber layer and the hole transport layer. To delve deeper into the fluctuations in device efficiency in environments with low temperatures, this study established the temperature spectrum between 270 and 300 Kelvin. Investigations revealed that at 272 K, the PCE and FF stood at 28.33% and 83.79% respectively, indicating the effectiveness of DJ type 2D layered PSC in low-temperature applications, preserving structural integrity and superior efficiency relative to other PSCs. Consequently, this study offers a viable approach for creating DJ type 2D layered PSC, ensuring high efficiency and enduring stability in cooler conditions.

Water-Extended Low-Density Granite-Based Geopolymer for Low-Temperature Well Cementing Applications: The Impact of Precursor Selection and Particle-Size Distribution

Summary Well cementing in areas close to the seabed remains a challenge due to unique conditions such as cold temperatures and weaker formations, leading to delayed cement hardening, extended drilling operation, and well integrity issues. Considering Portland cement’s limitations in cold areas and significant CO2 emissions through its manufacturing process, the need for more sustainable alternatives is highlighted. A low-density geopolymer through the water-extended approach was developed based on a previous study on low-temperature applications. Utilizing granite-based materials, this study optimizes the mix design by refining precursor particle sizes, using high-calcium blast furnace slag (BFS), and incorporating an amorphous potassium silicate activator. The research methodology includes sets of well cementing evaluations such as viscosity measurements, pumpability tests, and mechanical strength assessments. In addition, characterization techniques such as particle-size distribution (PSD) analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and isothermal calorimetry were used. These tests were crucial in understanding the material’s behavior under the specified application conditions. The findings reveal that the proposed geopolymer mix exhibits acceptable hardening time and mechanical strength development at lower temperatures, making it suitable for the challenging conditions of cold shallow-depth cementing. The study proves the feasibility of using high water content for geopolymers with acceptable properties and the novelty of its approach in the optimization of precursor particle sizes and the addition of higher calcium BFS. The geopolymer’s performance, even with a high water/solids ratio, highlights its versatility as a potential sustainable and efficient alternative to Portland cement.

Evolved photovoltaic performance of MAPbI3 and FAPbI3-based perovskite solar cells in low-temperatures

Organic-inorganic hybrid perovskites have emerged as an up-and-coming contender for photovoltaic devices owing to their exceptional photovoltaic properties. However, current research predominantly concentrates on their performance under ambient conditions at room temperature. In this work, we delve into the novel territory by investigating MAPbI3-based and FAPbI3-based perovskite solar cells (PSCs) in the temperature range of 300 to 150 K. Remarkable efficiency enhancements of nearly 5% and 20% were obtained at 250 and 210 K, respectively. However, further decreasing the temperature impairs the photovoltaic performance. We propose an underlying mechanism influencing the performance change in perovskite devices at low temperatures by examining the temperature-dependent ultraviolet-visible and photoluminescence spectra results. At the beginning of the cooling process, from 300 to 250 K for MAPbI3 and from 300 to 210 K for FAPbI3, the performance enhancement stems primarily from the enhanced open-circuit voltage by the tuned band gap of the perovskite films. Further lowering the temperature would change the perovskite structure, impairing the performance of PSCs. FAPbI3-based PSCs show a better tolerance in low temperatures owing to the more stable perovskite crystal structure. The present findings offer valuable theoretical guidance for preparing outstanding PSCs for low-temperature applications.

Performance evaluation and optimization of the cascade refrigeration system based on the digital twin model

Cascade refrigeration systems (CRSs) have become the priority choice in low-temperature applications, causing severe energy waste due to the lack of practical control strategies. Currently, refrigeration simulations are mainly based on the simplified thermodynamic or Artificial Intelligence (AI) model. However, the former is insufficiently accurate, while the latter is of unclear thermodynamic significance. By connecting the physical and digital space, the digital twin technology provides exciting opportunities for combining thermodynamic and AI methods. In this paper, an integrated digital twin model for the CRS is innovatively proposed based on the modified semi-empirical model of the twin-screw refrigeration compressor. As a major update, the identification and update method of characteristic parameters is developed based on real-time operating data to ensure performance consistency between digital and physical twins. By comparing with the simplified model, results show that the digital twin model can improve prediction accuracy by 7.42%–23.62%. Founded on the proposed model, the thermodynamic performance of the CRS is evaluated. To facilitate on-site applications, the definition of flat intermediate temperature is given, which is fitted to a control correlation with several easily observed variables as the inputs. Taking a food factory as a case study, simulation results reveal that the optimum intermediate temperature should be significantly lower than the original, and the coefficient of performance (COP) has an average improvement potential of 9.1%. By deploying the optimum strategy under the on-site condition, a superior energy-saving rate of up to 13.1% is attained according to test reports.

Effect of operating regimes on the heat transfer and buoyancy characteristics of supercritical CO2 natural circulation loop - A numerical study

At present, 82% of global energy is generated by fossil fuels which produce substantial emissions and have a significant impact on the environment. Heat transfer devices play a vital role in enhancing the efficiency of power generation systems and mitigating environmental impact. Among various heat transfer devices, natural circulation loops (NCLs) assume significance due to their simplicity and safety. In the present study, numerical investigations were conducted on three-dimensional rectangular circular cross-section supercritical CO2-based NCL across three distinct operating regimes. These regions include the average temperature of NCL maintained near the widom line (near pseudo-critical region), away from the widom line (higher buoyancy region) and very far away from the widom line (deeply supercritical region). The results indicate that in all regions, there is an increase in both the mass flow rate and heat transfer rate as pressure increases. At a pressure of 14 MPa, the maximum heat transfer rate across all regions is observed. Although the higher buoyancy region exhibits a superior heat transfer rate, the near pseudo-critical region demonstrates efficient heat transfer capabilities. For example, at 11 MPa, the temperature difference in the higher buoyancy region exceeds that in the near pseudo-critical region by 73%. However, the reduction in heat transfer rate in the near pseudo-critical region is only 37% compared to the higher buoyancy regions. For low-temperature applications, the near pseudo-critical region effectively transfers heat. However, in high-temperature applications, the sink temperature should be kept in the liquid-like region to maximize system buoyancy.

Additives for Aqueous Zinc-Ion Batteries: Recent Progress, Mechanism Analysis, and Future Perspectives.

Aqueous zinc-ion batteries (ZIBs) stand out as a promising next-generation electrochemical energy storage technology, offering notable advantages such as high specific capacity, enhanced safety, and cost-effectiveness. However, the application of aqueous electrolytes introduces challenges: Zn dendrite formation and parasitic reactions at the anode, as well as dissolution, electrostatic interaction, and by-product formation at the cathode. In addressing these electrode-centric problems, additive engineering has emerged as an effective strategy. This review delves into the latest advancements in electrolyte additives for ZIBs, emphasizing their role in resolving the existing issues. Key focus areas include improving morphology and reducing side reactions during battery cycling using synergistic effects of modulating anode interface regulation, zinc facet control, and restructuring of hydrogen bonds and solvation sheaths. Special attention is given to the efficacy of amino acids and zwitterions due to their multifunction to improve the cycling performance of batteries concerning cycle stability and lifespan. Additionally, the recent additive advancements are studied for low-temperature and extreme weather applications meticulously. This review concludes with a holistic look at the future of additive engineering, underscoring its critical role in advancing ZIB performance amidst the complexities and challenges of electrolyte additives.

Harnessing solar power in industry: Heuristic optimisation design and transient thermal modelling of parabolic trough solar collector networks

This study presents the development of a transient model for designing and optimising parabolic trough solar thermal plants for industrial processes. The model is validated against published experimental data and other models from the literature. A heuristic optimization methodology based on Particle Swarm Optimization (PSO) to maximise the Present Value of the Life Cycle Energy Savings (PVLCES) is employed. This methodology is applied to three case studies. The results highlight the versatility of PTC (parabolic trough collector) technology in handling a wide range of temperatures. Additionally, the study reveals the optimal PTC aperture width dimensions that maximise the capture of solar thermal energy while increasing the solar fraction. Specifically: For low-temperature processes, the optimum aperture width is 5.0 m; in medium-temperature processes, the optimum aperture width increases to 5.5 m; for high-temperature applications, the optimal value is 5.8 m. Finally, the optimised networks achieve the following heat load-to-area ratios: Low-temperature applications: 0.57 kW/m²; medium-temperature applications: 0.58 kW/m²; high-temperature applications: 0.6 kW/m².

Anomalous behaviour of the ionic conductivity of nanoconfined IL -lithium salt mixtures

The effect of salt addition on the protic ionic liquid (IL) ethylimidazolium nitrate is analysed in this work in terms of structural changes measured by NMR, thermal behaviour and ionic conductivity. Additionally, the effect of the immobilization of these mixtures in nano-silica structures on the same properties is also studied. Results show that the influence of salt on the chemical shifts of the signals associated to hydrogen atoms in the apolar regions of the ionic liquid is almost negligible, both in liquid and gel states. The salt accommodates in the polar region of the IL, according to the nanostructured solvation paradigm. The liquid range increases with salt concentration in both states, being this effect especially interesting for high and low temperature applications. The ionic conductivity takes appropriate values to use these compounds as electrolytes in electrochemical devices; pure IL presents 6.9 mS·cm−1 at 298 K rising to 17.38 mS·cm−1 at 323 K and this property decreases with salt concentration in the liquid state, as can be expected. Although gel samples present lower ionic conductivity than liquid samples, an anomalous behaviour can be observed in the ionogel samples upon the salt concentration, characterized by an absolute maximum, 13.26 mS·cm−1 at 323 K, at the lowest salt concentration (0.5 mol·kg−1 of Li+ salt addition), which represents the 12 % higher than the corresponding values of pure ionogel at this temperature.

Thermal Properties Characteristic of Aluminium-Alumina Composite for Solar Water Heating System Application

Thermal Energy Storage (TES) is an energy storage mechanism or material with modern technology at low costs, such as metal, concrete, composites, and others. Aluminum (Al)–Alumina (Al2O3) Composite is a solid material with high strength and hardness characteristics that can work in low-temperature applications. This study aims to analyze the features of the thermal properties of composite materials in the form of thermal conductivity and specific heat capacity. Composite specimens were prepared using powder metallurgy techniques. The weight fraction of alumina in the composite is 35%, 50%, and 65%. There are three (3) composite models, namely C1(35Al-65Al2O3), C2 (50Al-50Al2O3), and C3(65Al-35Al2O3). Models were made using the cold compaction method with a compressive load of around 20-25 MPa, and the specimens were fired in a furnace at a temperature of 550 °C with a holding time of 30 minutes. Scanning Electron Microscopy analyzed the microstructure of the composites. Composite thermal conductivity test using a thermal conductivity apparatus, and composite heat capacity test using a Differential Scanning Calorimetry (DSC). The results showed that C1(35Al-65Al2O3) composite had higher density and specific heat capacity than C2 and C3 composites. The theoretical density and specific heat capacity values of the C1 composite are 3.39 g/cm3 1.36 J/g.°C. However, the value of the thermal conductivity of C1(35Al-65Al2O3) material is lower than the other composites with a value of 0.37 W/m.°C. The greater the percentage by weight of alumina in the aluminum-alumina composite, the more theoretical density and specific heat capacity will also increase. Still, the thermal conductivity of the composite will decrease. Composite C1 35Al-65Al2O3 can potentially be a heat energy storage material used in solar water heating systems because of its high density and heat capacity.

Synergistic Combination of Sb2Si2Te6 Additives for Enhanced Average ZT and Single-Leg Device Efficiency of Bi0.4Sb1.6Te3-based Composites.

Thermoelectric materials are highly promising for waste heat harvesting. Although thermoelectric materials research has expanded over the years, bismuth telluride-based alloys are still the best for near-room-temperature applications. In this work, a ≈38% enhancement of the average ZT (300-473K) to 1.21 is achieved by mixing Bi0.4Sb1.6Te3 with an emerging thermoelectric material Sb2Si2Te6, which is significantly higher than that of most BiySb2-yTe3-based composites. This enhancement is facilitated by the unique interface region between the Bi0.4Sb1.6Te3 matrix and Sb2Si2Te6-based precipitates with an orderly atomic arrangement, which promotes the transport of charge carriers with minimal scattering, overcoming a common factor that is limiting ZT enhancement in such composites. At the same time, high-density dislocations in the same region can effectively scatter the phonons, decoupling the electron-phonon transport. This results in a ≈56% enhancement of the thermoelectric quality factor at 373 K, from 0.41 for the pristine sample to 0.64 for the composite sample. A single-leg device is fabricated with a high efficiency of 5.4% at ΔT = 164 K further demonstrating the efficacy of the Sb2Si2Te6 compositing strategy and the importance of the precipitate-matrix interface microstructure in improving the performance of materials for relatively low-temperature applications.

Spent ion-exchange resin as a new aggregate to enhance specific heat capacity of composite building materials: A case study on gypsum plaster

Spent ion exchange resin (SIER) is a by-product derived from drinking water treatment plants, possessing intriguing physicochemical properties that render it a promising ingredient for composite building materials. Surprisingly, there has been a luck of research investigating its impact on the performance of such materials. This study addresses this gap by characterizing unfired and fired gypsum-based composites with varying SIER weight ratios (10–50 wt%) and firing temperatures (300, 600, and 900°C). X-ray diffraction, scanning electron microscopy, and the hot disk method were employed to explore the effects of SIER on the composites’ thermal-mechanical features. The results revealed the significance of SIER as a promising waste-based aggregate to enhance the specific heat capacity (cp) of gypsum-based composites. With increasing SIER content and firing temperature, the composites demonstrate improved cp, reduced thermal conductivity, and decreased compressive strength. Both unfired and fired composites exhibited an increase in cp, up to 74.4% and 331.8%, respectively. The composite material achieved a noteworthy reduction in thermal conductivity, reaching 0.132 W/m.K, and a specific heat capacity increase to 4491.35 J/kg.K, which surpasses that of the control sample by more than four times (1040 J/kg.K). These newly developed composites hold significant promise as thermal energy storage materials for low-temperature building applications.

Preparation and characterization of palmitic acid/polymer composite phase change materials supported with cross-linked poly(limonene-co-ethylene glycol dimethacrylate) copolymers for low-temperature thermal applications

Limonene-based polymers have a growing interest as being renewable source-derived materials. Here, highly cross-linked porous polymers were synthesized by free radical copolymerization of water-in-oil (w/o) high internal phase emulsions (HIPEs) of limonene and ethylene glycol dimethacrylate (EGDMA). The bio-derived monomer content in the total monomer composition was set to 50 vol%. To vary the openness and permeability of the resulting porous copolymers, synthesized poly(limonene-co-EGDMA) (PLE-x) copolymers were processed via two different approaches as extraction (E) and lyophilization (L). Ultimately, the ring-porous PLE-E or PLE-L copolymers with different degrees of permeability were used as supporting matrices for the development of form-stable palmitic acid@poly(limonene-co-EGDMA) (PA@PLE-E and PA@PLE-L) composite phase change materials (PCMs). The chemical structure, pore morphology, specific surface area, and thermal properties of the PLE based supports and PA@PLE-E / PA@PLE-L composite PCMs were explored. BET specific surface areas of the ring-porous PLE-E and PLE-L frameworks were measured to be 20.5 m2.g−1 and 4.8 m2.g−1. In addition to that, the latent heats of the resulting composite PCMs were found to be 77.4 J.g−1 and 64.1 J.g−1, while the peak melting temperatures were 63.4 °C and 60.7 °C, for PA@PLE-E and PA@PLE-L, respectively. The bio-derived matrices based thermally stable leak-proof PA@PLE-x composite PCMs with proper latent heat storage (LHS) characteristics are ideal candidates as energy materials for passive solar heating applications due to their favorable phase change temperatures.

Study of a Thermochemical Heat Storage Reactor Filled with Polyaluminum Sulfate for Low-Temperature Application

This paper investigates comprehensively the operational dynamics of a thermochemical heat storage (TCHS) reactor for low-temperature applications using polyaluminum sulfate and takes into consideration a developed simulation model with an experimentation validation. Significant concordances were found between the developed simulation model and the experimental results. Results reveal optimized conditions for the charging process using an electrical heater, with a heating temperature of 120°C at 10 K/min over 500 minutes. This achieves full material charging, with stabilized pressure drops at an equilibrium of 80 mbar, corresponding to a temperature of approximately 108°C, and yielding a thermal power of 950 W. An inlet vapor pressure of 18 mbar at 10°C for 5 hours is sufficient to completely discharge the bed, with pressure drops reaching around 30 mbar and a thermal power of 300 after reaction completion. Insights into conversion extents during both processes are provided, along with a remarkable thermal efficiency of 90% and a coefficient of performance (COP) of 97%, surpassing recommended theoretical values (50%). The study suggests further enhancing system performance through the design and implementation of a dedicated heat exchanger. The achievement of 75% of the targeted thermal power specification represents a significant milestone, offering valuable contributions towards the realization of sustainable technological advancements of both the reactor technology of TCHS and state-of-the-art thermal energy storage solutions. From the research, it is possible to infer further suggestions for enhancing this performance by designing and implementing a dedicated heat exchanger for both heat supply and retrieval mechanisms.

Expression and functional analysis of a recombinant aquaporin Z from Antarctic Pseudomonas sp. AMS3.

Aquaporin (AQP) is a water channel protein from the family of transmembrane proteins which facilitates the movement of water across the cell membrane. It is ubiquitous in nature, however the understanding of the water transport mechanism, especially for AQPs in microbes adapted to low temperatures, remains limited. AQP also has been recognized for its ability to be used for water filtration, but knowledge of the biochemical features necessary for its potential applications in industrial processes has been lacking. Therefore, this research was conducted to express, extract, solubilize, purify, and study the functional adaptations of the aquaporin Z family from Pseudomonas sp. AMS3 via molecular approaches. In this study, AqpZ1 AMS3 was successfully subcloned and expressed in E. coli BL21 (DE3) as a recombinant protein. The AqpZ1 AMS3 gene was expressed under optimized conditions and the best optimized condition for the AQP was in 0.5 mM IPTG incubated at 25°C for 20 h induction time. A zwitterionic mild detergent [(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate was the suitable surfactant for the protein solubilization. The protein was then purified via affinity chromatography. Liposome and proteoliposome was reconstituted to determine the particle size using dynamic light scattering. This information obtained from this psychrophilic AQP identified provides new insights into the structural adaptation of this protein at low temperatures and could be useful for low temperature application and molecular engineering purposes in the future.

2,5-Substituted Thiophene Functionalized Semifluorinated Polytriazoles and Evaluation of Low-Temperature Proton Exchange Membrane Application with Elevated Oxidative Stability

2,5-Substituted Thiophene Functionalized Semifluorinated Polytriazoles and Evaluation of Low-Temperature Proton Exchange Membrane Application with Elevated Oxidative Stability

A novel approach for designing efficient and sustainable cooling cycles with low global warming potential refrigerants

With the current legislation on the phase-out of 3rd generation refrigerants, new cooling cycles are expected to operate with 4th generation refrigerants, hence, the need for optimal system performance with these new working fluids. In this study, an innovative optimization approach was applied for the design of cooling cycles with 4th generation refrigerants based on integrating statistical analysis design of experiments (DoE) with molecular modeling using the polar soft-SAFT model. First, a detailed multi-criteria assessment was applied for the selection of 4th generation refrigerants in medium–low temperature applications. Results demonstrated the potentiality of trans-1,3,3,3-tetrafluoroprop-1-ene (R1234ze(E)) or cis-1,2,3,3,3-pentafluoroprop-1-ene (R1225ye(Z)) in terms of environmental, safety, and technical criteria in basic cooling cycles under specific operating conditions. Multi-objective optimization guided using statistical analysis tools were implemented to study potential enhancement in cooling cycle performance using these promising refrigerants in terms of energy and exergy efficiency. This included evaporator and condenser temperature, fluid choice, compression yield, superheating/subcooling degrees, and cycle type. The evaporation and condenser temperature, and the compressor efficiency are shown to monopolize more than three-quarters of the cumulative contribution on system efficiency for those operated with R1234ze(E) in advanced liquid-to-suction line heat exchangers (LL/SL-IHX). Further optimization through examining the effect of heat transfer phenomena assisted in determining optimal operating conditions for new systems operating with low GWP refrigerants, instilling annual cost savings of $1.59 K and reduction in CO2 emissions by 1.02 tCO2-eq compared to the baseline system.

Electrical and Electro-Thermal Characteristics of (Carbon Black-Graphite)/LLDPE Composites with PTC Effect.

Electrical properties and electro-thermal behavior were studied in composites with carbon black (CB) or hybrid filler (CB and graphite) and a matrix of linear low-density polyethylene (LLDPE). LLDPE, a (co)polymer with low crystallinity but with high structural regularity, was less studied for Positive Temperature Coefficient (PTC) applications, but it would be of interest due to its higher flexibility as compared to HDPE. Structural characterization by scanning electron microscopy (SEM) confirmed a segregated structure resulted from preparation by solid state powder mixing followed by hot molding. Direct current (DC) conductivity measurements resulted in a percolation threshold of around 8% (w) for CB/LLDPE composites. Increased filler concentrations resulted in increased alternating current (AC) conductivity, electrical permittivity and loss factor. Resistivity-temperature curves indicate the dependence of the temperature at which the maximum of resistivity is reached (Tmax(R)) on the filler concentration, as well as a differentiation in the Tmax(R) from the crystalline transition temperatures determined by DSC. These results suggest that crystallinity is not the only determining factor of the PTC mechanism in this case. This behavior is different from similar high-crystallinity composites, and suggests a specific interaction between the conductive filler and the polymeric matrix. A strong dependence of the PTC effect on filler concentration and an optimal concentration range between 14 and 19% were also found. Graphite has a beneficial effect not only on conductivity, but also on PTC behavior. Temperature vs. time experiments, revealed good temperature self-regulation properties and current and voltage limitation, and irrespective of the applied voltage and composite type, the equilibrium superficial temperature did not exceed 80 °C, while the equilibrium current traversing the sample dropped from 22 mA at 35 V to 5 mA at 150 V, proving the limitation capacities of these materials. The concentration effects revealed in this work could open new perspectives for the compositional control of both the self-limiting and interrupting properties for various low-temperature applications.

Phosphonate-based supercapacitor electrolyte integrating the advantages of flame retardancy, extreme temperature adaptability, and anti-supergravity

Traditional acetonitrile-based organic electrolytes continue to dominate in carbon-based supercapacitors due to their high performance-to-price ratio. However, its flammability, low extreme temperature applicability, and unknown anti-supergravity limit its application in some special scenarios (e.g., space exploration). For the first time, an electrolyte system based on potassium hexafluorophosphate (KPF6) and diethyl ethylphosphonate (DEEP) as the electrolyte salt and solvent, respectively, was proposed. The KPF6/DEEP system combines excellent flame retardancy, high capacitance performance at high (60 °C) and low (-70 °C) temperatures, anti-supergravity (60 G), and an operating voltage of up to 3.0 V, resulting in a stable and high power energy output of up to 16 Wh kg−1 for carbon-based supercapacitors at −60 °C. These benefits are primarily attributed to the distinct physical properties of DEEP (e.g., flame retardancy, low freezing point, high boiling point, and high compatibility with KPF6). Such outstanding overall performance, which incorporates excellent flame retardancy, extreme temperature adaptability, anti-supergravity, and cycle stability (capacity retention > 95 % after 14,000 cycles), outperforms the traditional acetonitrile-based system, opening up a new option for power devices for some applications with extreme environmental demands.

Thermal performance enhancement of lauric acid using nanomaterials as composite phase change material.

In the present work, lauric acid was taken as a phase change material (PCM), and different nanoparticles (NPs) such as SiO2, TiO2, CuO, and ZnO were taken as the supporting materials. CuO NPs were prepared through the co-precipitation technique; SiO2, TiO2, and ZnO NPs were synthesized via the sol-gel technique. These NPs with different weight fractions were dispersed into molten lauric acid, individually. The variations in thermal properties (phase change temperature and latent heat for solid and liquid) of the prepared composite PCMs due to the dispersion of NPs were observed by DSC analyses. An increase in thermal conductivity of the composite PCMs was observed with the increasing weight fraction of NPs. In order to ascertain the long-term utility, a thermal reliability test was conducted on the composite PCMs with repeated heating and cooling cycles. Also, the specific heats of the pure PCM and the composite PCMs were determined as a function of temperature. Further, the experimental investigation was performed on the pure PCM and the prepared composite PCMs to assess their phase change behavior, and the test results clearly proved that the time required for the complete melting and freezing process of the composite PCMs was less when compared to pure PCM. By considering the above facts, the newly prepared composite PCMs can be recommended as a potential candidate for low-temperature solar heating applications.

Techno-enviro-exergo-economic evaluation of hot water production by waste heat recovery using U-shaped pulsating heat pipe – an experimental study

ABSTRACT The energy crisis and increasing energy demand have prompted scientists and engineers to find ways to recover energy from waste heat. Also, environmental pollution caused by fossil fuels and planning to reduce environmental effects are other reasons for using wasted heat. Many studies have used pulsating heat pipes to transfer thermal energy from high-temperature systems to low-temperature applications and the energy and exergy efficiency of those systems have been investigated, but economic and environmental studies about them have not provided. In this study, the performance of a pulsating heat pipe on the waste heat recovery of a chimney for heating water for household consumption was experimentally investigated. The distilled water with a filling ratio of 60% was considered as the working fluid, and the results are presented for different pulsating heat pipe angles to the horizon from 0 to 90 degrees. Energy and energy analysis and economic and environmental assessments of the waste heat recovery system are presented and discussed. The highest hot water temperature in the reservoir outlet was about 58°C. Also, the CO2 mitigation and cost per cubic meter of hot water generation of the waste heat recovery system were 84.82 tons and 0.1$/m3. Moreover, the efficiency varied from 19% to 54% for horizontal and vertical pulsating heat pipes, respectively.