Thermal Performance Of System Research Articles

Influence of Hot Water Pipe Position on the Performance of Radiant Floor Heating Systems Integrated with PCM

To address the slow heating and low efficiency issues of traditional macro-packed phase change material (PCM) radiant floor heating systems, this study innovatively explores the impact of altering the eccentric positions of hot water pipes within the PCM encasement, based on computational fluid dynamics (CFD) numerical simulations. Starting with a concentric case as a baseline, the investigation extends to six different configurations achieved by displacing the hot water pipes vertically (upward and downward) and horizontally. The analysis encompasses the PCM's thermal state, temperature dynamics, spatial distribution, and heat flux. The results indicate that the arrangement of hot water pipes with upward and horizontal displacements demonstrates a more positive impact on improving the thermal performance of the PCM radiant floor heating system, with the effect becoming more pronounced as the displacement distance increases. Cases with upward eccentric movement of r/4 (where r is the encasement radius) and r/2 reached the optimal floor temperature of 297.15 K faster than the concentric case by 2 hours and 3.8 hours, respectively, during the heating phase. Cases with horizontal eccentric movement advanced by 0.5 hours and 2.5 hours, respectively. Cases with horizontal displacements of r/4 and r/2 caused smaller temperature fluctuations and provided greater comfort and energy efficiency than those with upward displacements, with average heat flux values being 4.75% and 11.82% lower, respectively. These findings offer theoretical support for the optimization and application of macro-packed PCM floor heating systems.

A methodology for incorporating thermal interference in the design of thermo-active pile groups

This paper introduces innovative practical methodologies for evaluating the thermal performance of thermo-active pile groups. First, a streamlined approach for determining G-functions within such groups, based on the G-function of a single thermo-active pile is introduced. This is accomplished through a newly introduced thermal interaction factor for G-functions quantifying the increase in temperature when a pile is subjected to thermal interference from another pile. Subsequently, the paper proposes a method for calculating the power of piles within thermo-active pile groups when subjected to transient inlet temperatures. A thermal interaction factor for power is derived, quantifying the power reduction resulting from thermal interference due to another pile operating in the vicinity. These simplified methodologies are shown to reproduce the thermal performance of pile groups simulated using three-dimensional thermo-hydraulic analyses with excellent levels of accuracy without the associated computational cost. Finally, the proposed design process is applied to a 3×3 thermo-active pile group subjected to transient thermal loads, yielding accurate estimations of power, G-functions, and temperature changes of the thermo-active pile group. Overall, these simplified methodologies offer a robust framework for evaluating and optimising the thermal performance of thermo-active pile systems.

Novel design and performance analysis of a selectively filtered nanofluid spectrum semi-trough solar concentrated photovoltaic/thermal system

ABSTRACT In this paper, the main novelty is the proposal and performance analysis of a novel selectively filtered nanofluid spectrum semi-trough solar concentrated photovoltaic-thermal (SPVT) system. Experimental preparation and optical tests of Ag-CoSO4/water nanofluid are conducted. The selected nanofluid for the SPVT system has an average absorptance of 53.5% and an average transmittance of 46.5% in 250.0 ~ 2500.0 nm. The optical analysis results show that the optical efficiency of the SPVT system is 94.3% under the optical filtering condition. When the solar tracking error increases to 0.3°, the optical efficiency of the SPVT system can still be kept at 84.8%. This means that the SPVT system has relatively good adaptability on solar tracking error. The operation performance analysis results indicate that under the optical filtering condition, the electric power and photo-electric efficiency of the PV subsystem are 392.1 W and 30.9%, and the thermal efficiency of the SPVT system is 40.7%. Effects of four factors on the thermal performance of the SPVT system are evaluated, which are the inlet nanofluid flow velocity and temperature, environmental temperature and convection heat transfer coefficient between the nanofluid flow channel and air. The results show that the thermal performance of the SPVT system can be improved by properly increasing the inlet nanofluid flow velocity and environmental temperature or by reducing the inlet nanofluid temperature and convection heat transfer coefficient between the nanofluid flow channel and air. When the inlet nanofluid flow velocity increases from 0.002 m/s to 0.004 m/s, the thermal efficiency of the SPVT system increases from 40.9% to 50.7%, and with the inlet nanofluid temperature increased from 6.0°C to 14.0°C, the thermal efficiency decreases from 48.6% to 45.6%. The results of this paper can provide certain reference for research and development works of solar PVT systems in the future.

Buoyancy-driven micropolar ternary hybrid nano-suspension within an oblique incinerator-shaped chamber: Thermal and second law analyses

Since performance of thermal systems may depend on fluids’ thermal conductivities being utilized as coolants, improvement of thermal efficiencies of fluids having micro-structures and involving ternary hybrid nanomaterials may be highly valued. In fact, microrotation of ternary hybrid nanofluids (THNFs) in oblique incinerator-shaped chamber may find applications in industrial processes involving polymeric solutions and lubricants where they help in reduction of drag forces and act as better cooling agent. In view of this, the present study carries out thermal and second law dissection of micropolar THNF within an oblique incinerator-shaped chamber heated from bottom emplacing a roundish heater under a fixed heat flux. The THNF comprises of Al2O3, CNT and graphene as nanoparticles. The study reveals that streamlines and isotherms undergo prominent change due to inclination of the chamber. When Raleigh number and diameter of heater amplify streamlines, microrotations, and entropy generation intensify while average Bejan number whittles down. Average heat transfer rate ameliorates by 4.54 % and 2.17 % when total volume fraction augments from 1.5 % to 3 % and 3 %–4.5 %, respectively. Heat transfer rate reduces by 1.23 %, 0.48 %, 3.33 %, 5.24 %, 2.07 %, and 1.66 % when inclination angle increases from 0° to 90° with inclination angle step 15°.

Theoretical investigation of the combined effects of solar energy and thermal buoyancy around a laminar jet placed in a porous medium

The current research examines the combined effects of solar energy and thermal buoyancy around a laminar jet placed in a porous medium. The governing boundary layer equations are dimensionalized by using appropriate dimensionless variables. The numerical solution of the dimensionless boundary layer equations is obtained using the finite difference method. The impact of physical parameters, which are Darcy number, dimensionless porous medium inertia coefficient, Prandtl number, radiation parameter, and dimensionless fluid's absorption parameter, on velocity and temperature profile, is shown graphically, while the influence of the above parameters on the heat transfer rate is presented in tabular form. It is keenly observed that for Darcy number velocity profile decreases while reverse behavior is noted for temperature distribution. For the dimensionless radiation parameter, both the velocity and temperature profile decrease. The main novelty of the current work is to improve the thermal performance of natural convection heat transfer system in the presence of thermal radiation placed in porous medium.

Tube cross-section flatness optimization to enhance the cooling performance of nanofluid-based photovoltaic thermal systems combined with nano-enhanced phase change material

Photovoltaic (PV) systems have emerged as a crucial technology in transitioning to sustainable energy. Despite their growing prominence, PV panels face challenges related to temperature-induced that can lead to reduced energy output. By considering this, the utilization of cooling systems is useful. In the quest to design the active cooling system for PV panels, a key challenge remains in optimizing tube cross-section configurations. In this study, a validated CFD simulation investigates the impact of the tube cross-section flatness (tube flattening) on the cooling performance of the nanofluid-based photovoltaic thermal system combined with nano-enhanced Phase Change Material (PCM). Evaluation parameters for cooling performance are PV surface temperature (T_s), PCM liquid Fraction (LF), tube pressure drop (ΔP), and the PV temperature uniformity (ΔT). Aluminum Oxide (Al2O3) and Silver (Ag) nanoparticles are used in different concentrations (0 %, 1 %, 5 %, 10 %). Also, using the Response Surface Method (RSM), a multi-objective optimization determines the optimal tube flattening percentage for achieving the best cooling performance. The ideal state entails minimizing T_s, maximizing LF, minimizing ΔP, and minimizing ΔT. The findings indicate that increasing tube flattening leads to a decrease in T_s, a decrease in LF, an increase in ΔP, and a reduction in ΔT. Reducing the T_s and ΔT is a favorable effect but increasing the ΔP and reducing the LF is unfavorable to the system's cooling performance. After evaluating different parameters in the optimized scenarios, the most optimal mode is determined when the system uses Ag nanofluid in 10 % concentration, PCM without nanoparticles, and tube with 44 % flattening. In this scenario T_s, LF, ΔP, and ΔT are respectively 54.04 °C, 37.7 %, 117.67 Pa, and 34.74 °C.

Analysis of charging performance of thermal energy storage system with graded metal foam structure and active flip method

The latent heat thermal energy storage (LHTES) technology based on solid-liquid phase change material (PCM) is characterized by high energy storage density, small volume change, and constant operation temperature, which is widely employed in waste heat recovery, solar thermal utilization, and equipment thermal management. This paper introduces active flipping and graded porous to strengthen natural convection and heat conduction to alleviate the issue of low thermal conductivity and non-uniform phase change of PCM. Based on the fixed grid system, the enthalpy-porosity method combined with time-dependent gravity and non-Darcy porous effect is employed to solve the solid-liquid phase change problem under different porosity gradients, dimensionless flipping times (t*), and modified Ra (Ra*) numbers. Furthermore, the effects of the Ra* on the optimal t* and porosity gradient are also discussed. The results show that the flipping method can significantly enhance flow and heat transfer within the container, improve temperature field uniformity, and increase the proportion of latent heat storage. With the increase of porosity gradient and t*, the melting time initially decreases and then increases and the optimal thermal performance is achieved at a 6 % porosity gradient and t* = 0.4. Compared to the uniform porous structure without flipping, it can shorten melting time by 49.37 % and improve thermal energy storage rate (TESR) by 76.23 %. Additionally, the optimal porosity gradient is 6 % under different Ra*, but the optimal t* decreases with the increase of Ra*. This paper explores the charging performance of the thermal energy storage system with the graded metal foam structure and active flip method, which can contribute to the study of heat transfer enhancement in LHTES technology.

Battery thermal management system by employing different phase change materials with SWCNT nanoparticles to obtain better battery cooling performance

Maintaining a stable temperature within a battery is essential for optimizing the performance of battery thermal management systems. Phase change materials (PCMs) have demonstrated potential in achieving this stability. This study investigates the use of single-walled carbon nanotubes (SWCNTs) dispersed in three PCMs with varying fusion temperatures to regulate the temperature of a lithium-ion battery (LIB) during discharge, a common scenario in electric vehicles. A Computational Fluid Dynamics (CFD) approach was utilized to simulate the liquid-solid transition of the PCMs, incorporating buoyancy forces in the liquid phase surrounding the LIB. The study examined the effects of different C-rates (1, 2, and 3), SWCNT volume fractions (0, 2, and 4 %), and three types of PCMs (RT27, RT35, and RT58) across multiple simulation scenarios to evaluate their impacts on LIB temperature and PCM melting fraction. Results indicate that nano-enhanced PCMs, which exhibit superior convection effects in the liquid phase, significantly enhance battery cooling performance. Specifically, at a C-rate of 1, using a 4 % volume fraction of nanoparticles in the PCM reduces the battery temperature by an average of 4.138 K compared to cases without nanoparticles. Additionally, while nanoparticles are generally reported to have a minor effect on cooling and melting processes, this study reveals that considering the beneficial effects of SWCNTs and the physical properties of the selected PCMs, the cooling performance of LIBs improves by 4.69 percentage points for the scenario with a C-rate of 3, RT58, and ɸ = 0.02. In this particular case, the melting process is more pronounced in the top half of the battery, where the increased velocity magnitude of the melted region contributes to enhanced battery cooling.

Optimizing micro power generation with blended fuels and porous media for H2-fueled combustion

To enhance the combustion stability and thermal performance of micro-thermophotovoltaic system, a combustor inserted porous media and varying channel heights for premixed H2/CH4/Air burning is proposed. The experimental and numerical methods are conducted to investigate the effects of CH4 addition, equivalence ratio, porous media, and chamber setting on combustion characteristics, heat transfer, and flame stability. The results indicate that a small fraction of CH4 addition and porous media insertion both enhance heat release and transfer of H2-fueled combustion, and the optimal CH4 blending ratio is influenced by chemical energy input. Appropriately increasing the equivalence ratio under high flow rates contributes to stabilize the flame and improve the combustor thermal performance. Furthermore, porous media effectively promotes flame stability and heat transfer efficiency, with longer porous media enhancing heat conduction and convection processes, thereby increasing the radiation temperature. Besides, increasing the channel height of the porous media combustor appropriately enhances the electrical power output of the power system. Besides, the maximum electrical output of 9.7 W is obtained in the porous media combustor with a channel height of 11 mm at mc = 20 %, Ф = 1.0 and mf = 9.448 × 10−5 kg/s, which is 7.2 W higher than the free flame combustor with h = 7 mm.

Effect of sawtooth wave distribution plenum with linearly increasing amplitude on the performance of battery thermal management system

Battery heat generation that occurs during battery charging and discharging can lead to excessive and non-uniform battery temperature in the battery pack. As a result, the battery is more vulnerable to rapid degradation and short cycle life. Effective heat dissipation methods therefore become crucial. In the present study, sawtooth waves with linearly increasing wave amplitude and an inlet notch on the distribution plenum (DP) have been introduced in a typical Z-type battery thermal management system (BTMS) to maximise the cooling effectiveness of the System. Numerical analysis is carried out to investigate the effect of various geometric parameters such as saw tooth wave position, saw tooth wave amplitude, saw tooth wave base width, inlet notch width, and inlet notch height on the performance of BTMS. Velocity contours, streamlines, temperature contours, and maximum battery temperature plots are used to discuss the effects of various factors on the operation of a BTMS. Compared with the typical Z-type BTMS, the modified enclosure design reduced the maximum average battery temperature ( T max ) and maximum temperature differential within the battery pack ( Δ T max ) by 5.11 and 9.01 K respectively, which are 1.56% and 94.90% less than the typical Z-type BTMS respectively.

Optimization of the thermal performance of a lobed triplex-tube solar thermal storage system equipped with a phase change material

The thermal performance of a PCM-based triple-tube lobed heat exchanger storage system is here simulated and optimized, including performance improvements via lobed surfaces, Y-shaped fins, dispersed multi-walled carbon nanotubes, and metal foams, to be used in combination, or singly. Such computations are done with the finite volume method under different operating conditions. The reason behind this study is to look for solutions to improve the poor thermal performance of phase change materials (PCMs) as thermal energy storage materials, that limits their compactness and instantaneous heat stored/released. This is the first time that a throughout analysis of this aspect is presented. The result showed that higher modified Stefan number allow to improve melting time of a 50.88 %. The inclusion of lobes and fins resulted in a reduction of roughly 30.54 % in time needed for melting completion, compared to straight tubes. This reduction increases to 74.26 % when lobes are combined with both nanoparticles and metal foam, and to 73.60 % with just foam. The best solution also provides a 228.34 W mean heat rate. This study becomes an option to design tube-in-tube energy storage systems, where the best improvement is achieved by considering a lobed surface together with nano/PCM and foam, whereas the highest enhancement comes from using a metal foam.

Simulation study on thermal performance of solar coupled air source heat pump system with phase change heat storage in cold regions

The development of efficient and clean heating technologies is profoundly significant for the reduction of carbon emissions in cold regions. This paper puts forth a novel solar-coupled air source heat pump system integrated with phase change heat storage technology, which is well-suited for regions with such climatic conditions. A numerical model of the components and coupled systems is established using the lumped parameter method, and an iterative method is employed for the computational solution in MATLAB software. A variety of system performance aspects are then simulated and analysed following the configuration of component structural parameters and initial operating conditions. The results of the simulations indicate that an increase in the phase change temperature interval of the phase change materials leads to a higher average heat release power. In particular, a 2°C increase in the phase change temperature interval results in an increase in the heat release power of over 10%. Furthermore, when the system is applied in typical cold regions, including Kunming, Hangzhou, Lhasa, and Harbin, the average coefficient of performance is 10.23, 8.87, 8.49, and 7.70, respectively. The proportion of solar energy input contributes to an increase in system efficiency across all regions. A case study of Hangzhou reveals that the incorporation of solar energy into the system results in an increase in efficiency of 70.91%. This research provides valuable operational methods and site selection recommendations for engineering practices, laying a theoretical foundation for its widespread application in cold regions.

Entropy production associated with magnetohydrodynamics (MHD) thermo-solutal natural convection of non-Newtonian MWCNT-SiO2-EG hybrid nano-coolant

This article investigates the convective thermal and solutal exchange from the active walls of a trapezium chamber which is filled with multi-walled carbon nanotubes (MWCNT)-silicon dioxide (SiO2)-ethylene glycol-water hybrid nano-coolant. The hybrid nano-coolant exhibits non-Newtonian shear-thinning rheology and is modeled by the power-law viscosity as per an exploratory report. The convection is generated by both the thermal and solutal buoyancy forces in the presence of a magnetic field. Thermophysical properties of the particular nano-coolants are estimated from the temperature-dependent empirical correlation. An in-house FORTRAN code based on the finite volume method (FVM) has been utilized to simulate the non-dimensional controlling equations representing the physical model. By systematically varying the strength of the magnetic field (Ha=0−50) and its direction (δ1=0−90), the volume fraction of nano-coolant (ϕ=0−0.04) and solutal-to-thermal buoyancy ratio (N=−2 to 2), we thoroughly analyzed their impact on the flow field, thermal, and solutal transmission behavior. Significant impacts arising from the shear-thinning nature (n<1) of the nano-coolant were observed, influencing both thermal and solutal transfer rates as reflected in the Nusselt number (Nu) and Sherwood number (Sh). The impact of Ha on Nu and Sh is more substantial for n<1 than the case n=1. The investigation exposed that when Ha=30,δ1=30∘ the average Nu (Nu‾) for nano-ccolants (ϕ=2%) is maximally enhanced by 80% for n=0.6 compared to the case n=1.0. For the same nano-coolant with Ha=30 and δ1=90∘, there is a 128% elevation in the average Sherwood number (Sh‾) when n=0.6 compared to n=1.0. The entropy generation (S‾) inherent to the heat and mass transfer process and hence a criterion (ξ=S‾/Nu‾) is computed to address the system thermal performance from the thermodynamics second law. S‾ increased as n was reduced, indicating that the shear-thinning effect contributed strongly to the entropy generation.

An investigation of heat transfer and optimization of entropy in bio-convective flow of Eyring-Powell nanomaterial with gyrotactic microorganisms

Entropy generation in nanofluid flows is a critical parameter that influences the performance, efficiency, and sustainability of thermal systems. Understanding and optimizing entropy creation can lead to noteworthy advancements in numerous engineering applications, from renewable energy systems to industrial processes and biomedical equipments. The purpose of this article is to examine the entropy produced in the bioconvection flow of Eyring-Powell nanomaterial with gyrotactic microorganisms. The mathematical equations representing the flow are modeled considering the flow towards a porous surface of a cylinder. Together with the effects of the governing parameters, the mass and heat transfer components of the problem are discussed. The thermal effects of different natures are used in a new way. Overall, entropy creation is designed with regard to the second law of thermodynamics. Activation energy, chemical reaction, thermal radiation, and internal friction force effects are accounted for the development of the mathematical model. Coupled non-linear dimensional equations have been altered into ordinary differential equations (ODEs) and then treated using the MATLAB Finite Difference Method (FDM). Consequence of diverse sundry parameters on entropy production, thermal field, mass concentration profile, Bejan quantity, and motile density of microorganisms is deliberated via plots. Through tables, engineering quantities are analyzed. According to the findings, the velocity profile rises as the curvature and Eyring-Powell fluid parameters rise, while it falls when the magnetic parameter is enhanced. Additionally, it is noted that as the curvature variable enhances, the rate of heat transfer and skin friction coefficient decays.

Effects of winter climate parameters on the thermal performance of dynamic rotating latent-energy-storage envelope (DRLESE)

The accurate application of the Dynamic Rotating Latent-Energy-Storage Envelope (DRLESE) system necessitates careful consideration of outdoor climate conditions, which significantly impacted latent heat operation of Phase-Change Materials. The effects of climate parameters were explored by considering five convective heat transfer coefficients ranging from 10 W/(m·K) to 30 W/(m·K), six daily solar radiation intensities ranging from 15.0 MJ/Day to 30.0 MJ/Day, six air average temperatures ranging from −10.0°C to 15°C, and six fluctuation ranges of air temperature ranging from 5°C to 20°C. The thermal performance of the DRLESE system was evaluated by employing the liquid fraction of Phase-Change Materials (PCM), the thermal quantity of DRLESE, and the inner surface heat flow. The numerical results demonstrated that climate parameters have a profound effect on the thermal performance of the DRLESE system. Enhancing convective heat transfer coefficient or lowering outdoor air temperature can significantly attenuate thermal performance by promoting convective thermal dissipation, while increasing daily solar radiation intensity can provide ample solar radiation for absorption by the DRLESE system. With convective heat transfer coefficient increased from 10 W/(m2·K) to 20 W/(m2·K), the daily solar radiation intensity increased from 15MJ/Day to 30MJ/Day, outdoor air temperature increased from −10°C to 15°C, the fluctuation range increased from 5°C to 20°C, indoor effective thermal release was increased −55.38 %, 204.66 %, 241.00 % and 8.11 %, respectively. In addition, employing the transparent covers and selecting the appropriate PCM were recommended to enhance thermal performance of the DRLESE system.

Dynamic thermal performance analysis and experimental study of cascaded packed-bed latent thermal energy storage integrated solar trough collectors

The instability of the renewable energy significantly impacts the thermal performance of solar thermoelectric systems. In this paper, a coupling system consisting of solar trough collector and double-layer cascaded packed-bed latent heat storage system (PLTES) is constructed to investigate thermal performance and operating parameters under dynamic conditions. Additionally, the experimental platform was upgraded to evaluate the dynamic charging/discharging process of the cascaded PLTES. The results show that under dynamic inlet heat flow, the PLTES exhibits only one peak temperature difference, and the average temperature is lower than that in the steady-state. The cascade-packed structure promotes a more uniform temperature and liquid phase distribution, resulting in a longer heat flow output. Higher mass flow rates of the heat flow increase convective heat transfer and reduce the temperature difference, though they have little effect on the energy efficiency. Conversely, an increase in capsule diameter significantly reduces the energy efficiency. Experimental results indicate that under dynamic conditions, the total charge-discharge capacity of the cascade system decreases by 0.5 MJ and 0.9 MJ, and the energy efficiency decreases by 0.15. Nevertheless, the energy efficiency of the cascaded PLTES (0.57) is higher than that of the single layer (0.5).

Thermal performance of solar ground source heat pump system for rural buildings in Chinese cold zone

In response to China's national policy of “achieving carbon peak by 2030 and carbon neutrality by 2060″, and to promote the heating system of rural buildings in China's severe cold zone. Two heating schemes of the GSHP (Ground Source Heat Pump) system and the SGSHP (Solar Ground Source Heat Pump) system are designed and simulated for a single rural residential building in Harbin city. The results present that the outlet temperature of buried pipe in SGSHP system is 13.86 % higher than that in GSHP system, and coefficient of performance (COP) correspondingly increases 9.2 %. There is a better comprehensive performance for the SGSHP system in cold climates. The standard coal consumption of SGSHP system is about 72.35 % less than that of biomass boiler system, showing a greater energy efficiency. Compared to the local conventional biomass boiler system, the dynamic cost payback period of the SGSHP system amounts to 11 years, while yielding a net present value (NPV) of 10,800 CNY throughout the project's life cycle. The emissions of CO2, SO2, and dust are reduced by 2617.13 kg, 19.38 kg, and 14.535 kg respectively. The results indicate a great overall performance of the SGSHP system for residential heating in the cold climate zone. This research offers an energy efficient and eco-friendly alternative for the space heating of Chinese rural buildings in cold climates.

Experimental study of the thermal performance of spiral flow solar water heating system

Experimental study of the thermal performance of spiral flow solar water heating system

MXene: A Roadmap to Sustainable Energy Management, Synthesis Routes, Stabilization, and Economic Assessment.

MXenes with their wide range of tunability and good surface chemistry provide unique and distinctive characteristics offering potential employment in various aspects of energy management applications. These high-performance materials have attracted considerable attention in recent decades due to their outstanding characteristics. In the literature, most of the work is related to specific methods for the preparation of MXenes. In this Review, we present a detailed discussion on the synthesis of MXenes through different etching routes involving acids, such as hydrochloric acid, hydrofluoric acid, and lithium fluoride, and non-acidic alkaline solution, electrochemical, and molten salt methods. Furthermore, a concise overview of the different structural, optical, electronic, and magnetic properties of MXenes is provided corresponding to their role in supporting high thermal, chemical, mechanical, environmental, and electrochemical stability. Additionally, the role of MXenes in maintaining the thermal management performance of photovoltaic thermal systems (PV/T), wearable light heaters, solar water desalination, batteries, and supercapacitors is also briefly discussed. A techno-economic and life cycle analysis of MXenes is provided to analyze their sustainability, scalability, and commercialization to facilitate a comprehensive array of energy management systems. Lastly, the technology readiness level of MXenes is defined, and future recommendations for MXenes are provided for their further utilization in niche applications. The present work strives to link the chemistry of MXenes to process economics for energy management applications.

Experimental study on improving the thermal performance of isobutane refrigeration system by parameter optimization

Improvement of thermal efficiency for isobutane refrigeration system could match well with the building requirements of low-carbon, and sustainable development. The electric radiant heater (ERH) is widely used for the freeze and cold storage (FCS) system, but it has problems of high electric consumption and high freezer compartment temperature rise (FCTR) as a result of low heat-transfer efficiency under defrosting. Therefore, a novel FCS system with an additional electric radiant heater (AERH) based on the heat required for frost melted and synchronous defrosting is proposed. The defrosting consumption and the FCTR of the novel FCS system are comprehensively evaluated by a novel evaluation method. Besides, the effect of the thermal parameters (i.e., the defrosting pause temperature, the position, and electric power of the AERH) on the heat transfer characteristics are compared and optimized by the experimental method. Finally, a novel method is presented to predict the optimum thermal conditions. The results show that the optimum system thermal performance is obtained, the defrosting duration and defrosting consumption are reduced by 44.02 % and 37.03 %, and the defrosting efficiency and energy efficiency could be increased by 17.92 % and 9.96 %, respectively, as compared to the conventional FCS system. The proposed FCS system has better economic performance and heat transfer efficiency. Meanwhile, 30.54 kg of CO2 emissions could be avoided during the annual operation period, and the environmental benefits are also considerable. This study not only reaffirms the benefit of using the AERH for defrosting in the FCS system but also provides a reference for the promotion and application of efficient heat transfer technology in building refrigeration engineering.