International Journal of Thermophysics最新文献

This study evaluates the energy performance, operational carbon emissions, and energy autonomy of electrified residential buildings compared to a conventional gas-based Zero-Energy Building (ZEB) under Korea’s ZEB certification framework. A detached single-family house was modeled with three configurations: a gas-based ZEB, a Packaged-Terminal Heat Pump (PTHP) ZEB, and an Air-to-Water Heat Pump (AWHP) ZEB. A 3-kW rooftop photovoltaic (PV) system was applied to all cases, representing a typical residential-scale installation for energy self-sufficiency. The results show that full electrification increases primary energy consumption—from 148.3 to 201.6 kWh/m²·yr—under the current source energy conversion factor (2.75 for electricity), making it difficult for electrified ZEBs to satisfy the present 90 kWh/m²·yr threshold. Although the electricity emission factor (EF) of the Korean grid is projected to decline significantly from 0.4781 to 0.0480 kgCO₂eq/MWh by 2050, this reduction reflects grid decarbonization, not changes in building performance. When building operational emissions are recalculated using the future EF values, electrified ZEBs show substantially lower annual emissions than the gas-based case, highlighting the long-term benefits of electrification under a decarbonized power system. PV-based energy autonomy analysis reveals that the load cover ratio (LCR) and self-consumption ratio (SC) remain within 38–67%, while the self-sufficiency ratio (SS) exceeds the 20% threshold required for ZEB certification. Nevertheless, the high loss of power supply probability (63–78%) underscores the necessity of storage or load-shifting strategies. Overall, electrification represents a viable transition pathway toward carbon–neutral ZEBs, contingent upon continued grid decarbonization and expanded renewable integration.

Passive radiative cooling performance is influenced by material properties and meteorological conditions. A more transparent atmospheric window reduces downwelling longwave radiation, thereby increasing cooling power and reducing surface temperature. Atmospheric emissions can be quantified using sky emissivity or sky temperature, both of which can be parameterized by ambient temperature, humidity, and cloudiness. This study first reviews the historical development of clear-sky and cloudy-sky temperature models, highlighting the challenges in establishing a universal sky temperature model. It then examines state-of-the-art meteorological remote sensing technologies and assesses their roles in monitoring and acquiring radiative cooling data. As radiative cooling materials and systems hold strong potential for building energy conservation and their effectiveness is highly weather-dependent, this study investigates how radiative cooling informatics enhances quantitative building energy simulations, assessments, and management.

We numerically and experimentally investigate the impact of photogenerated minority excess carriers on the plasma–elastic and total photoacoustic response of semiconductors. The frequency domain behavior of photoacoustic signals is examined as a function of the surface conditions, optical absorbance, and material thickness. For a visible-light excitation, distinct peak-like features in the plasma–elastic amplitude emerge at high modulation frequencies and for thin enough samples. These trends are attributed to carrier density asymmetries between the illuminated and non-illuminated surfaces. These findings highlight the key role of carrier dynamics in shaping plasma–elastic coupling to optimize and interpret photoacoustic measurements in semiconductor characterization.

Molten salts play a crucial role in numerous industrial applications, including nuclear reactors, thermal energy storage, and high-temperature electrochemical processes. Their thermophysical properties, such as viscosity, surface tension, and molar volume, are essential for optimizing performance and ensuring operational safety, as they govern heat transfer, fluid flow, and interfacial behavior in high-temperature environments. The TCSALT Molten Salts Database (Version 2.0) provides critically assessed thermodynamic and thermophysical data for fluoride- and chloride-based salts with oxide additions: AlCl₃–AlF₃–Al₂O₃–CaCl₂–CaF₂–CaO–KCl–KF–K₂O–LiCl–LiF–Li₂O–MgCl₂–MgF₂–MgO–NaCl–NaF–Na₂O–SiCl₄–SiF₄–SiO₂–SrCl₂–SrF₂–SrO–ZnCl₂–ZnF₂–ZnO. The database employs the Ionic Two-Sublattice Liquid Model to describe the molten salt solutions, enabling accurate predictions of multicomponent phase diagrams together with both thermodynamic and thermophysical properties. Using this database, viscosity and surface tension can be directly predicted from the underlying ionic structure description of the melt, offering quantitative insights into species distribution, connectivity, and structural evolution across a wide range of temperatures and compositions. The database also includes molar volume descriptions for both liquid and solid phases, further enhancing its applicability in high-temperature material processing and engineering applications. The integration of these thermophysical properties within a unified computational thermodynamic framework provides a powerful tool for material design and process optimization.

New experimental data for squalane, including liquid densities, liquid heat capacities, and saturated vapor pressures, are presented together with their respective uncertainties. Liquid densities were determined from 293.15 K to 453.15 K at pressures up to 20 MPa using an accurate single-sinker magnetic suspension densimeter. Auxiliary measurements were performed with a vibrating tube densimeter from 273.15 K to 363.15 K at ambient pressure, including the correction for sample viscosity. Heat capacities were measured using two differential scanning calorimeters, covering a temperature range from 260 K to 518.6 K. Vapor pressures in the range from 0.21 Pa to 49 Pa were acquired by the static method, spanning a temperature interval from 388 K to 462 K. Correlations for density and heat capacity of liquid squalane developed within this work are discussed and compared to the literature data. A correlation for saturated vapor pressure in the form of the Wagner equation, covering a wide temperature range, was obtained by simultaneously correlating vapor pressures and the relevant caloric data. The choice of exponents used in the Wagner equation is discussed.

Given the high cost and time demands associated with experimental thermodynamic measurements, the development of reliable, theory-based equations of state (EOSs) is crucial for the accurate prediction of refrigerant behavior in practical thermal systems. Such predictive capabilities are essential for optimizing the design, efficiency, and energy performance of refrigeration and heat pump technologies. In this study, a novel two-parameter cubic EOS was developed within a simplified statistical mechanical perturbation theory framework. The temperature-dependent parameters of the proposed model were optimized using saturated property data for 35 refrigerants, covering a wide range of industrially relevant compounds including chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, hydrocarbons, and natural inorganic refrigerants. Comparative evaluations were conducted for vapor–liquid equilibrium (VLE), saturated and high-pressure liquid densities, normal boiling points, enthalpies of vaporization, pressure–enthalpy (P–H) diagrams, pressure–pressure (P–S) diagrams, isochoric specific heat capacities (C_v), isobaric specific heat capacities (C_p), speed of sound (u), and the coefficient of performance for selected refrigerants, employing the proposed EOS alongside other widely adopted two-parameter models. Furthermore, the new EOS was applied to mixture systems, including isothermal VLE calculations for azeotropic and non-azeotropic binary mixtures, liquid density predictions, thereby demonstrating its versatility and applicability to chemical and process engineering refrigerant systems. The results of the comparative analyses consistently highlight the superior predictive performance of the proposed simple cubic EOS relative to commonly used existing models.

The use of heat transfer improvement methods is crucial for enhancing energy efficiency, minimizing system sizes, lowering costs, and promoting environmental sustainability. In this context, passive (fins, nanoparticles, etc.) and active (ultrasonic, magnetic field) heat transfer improvement methods are applied to the thermal systems. However, relatively few studies have examined the combination of nanofluid and ultrasonic enhancement. Taking advantage of this gap in the literature, this study presents the first systematic experimental investigation of a CuO/water nanofluid in laminar flow regime combined with low-power (P_us = 5 W) ultrasound (US), focusing on the synergistic effects on thermohydraulic performance. For this purpose, a heat flux of q″ = 2250 W·m⁻² was applied to the surface of a smooth tube made of copper, and two different volumetric concentrations (φ = 0.01% and 0.05%) of CuO/water nanofluid were passed through it at four different Reynolds numbers (Re) of 500, 825, 1500, and 1780. In addition, US was applied at a frequency of f = 25.7 kHz at the entry section. The average Nusselt number (Nu) was found to increase with both the increase in Re and the application of US. With the application of US, the average Nu values of the systems containing water, φ = 0.01% and 0.05% CuO/water nanofluids were increased by 11.0 %, 2.0 %, and 4.0 %, respectively. However, when the nanofluid concentration was increased to φ = 0.05%, the average Nu decreased compared to φ = 0.01%, which was considered to be due to increased viscosity and particle agglomeration. The average friction coefficient (ff) increased with both nanofluid use and US. In experiments with water, an average of 20% increase was obtained with the US application, while increases of 15% and 10% were observed with φ = 0.01% and 0.05%, respectively. In measurements performed under NUS (non-ultrasonic) conditions, it was determined that φ = 0.01% and 0.05 % CuO/water nanofluids increased the friction in the system by 11.0% and 15.7 %, respectively. In terms of Performance Evaluation Criteria (PEC) analyses, the use of φ = 0.01% CuO/water nanofluid was more favorable than φ = 0.05%. Although PEC was higher in US conditions at low Re, NUS conditions were found to be more advantageous, as the average PEC values obtained under NUS conditions were 3.0% higher compared to US conditions. These findings demonstrate that the use of low-concentration nanofluid and optimal US application is critical to efficiency in heat transfer systems.

This study investigates thermal energy transport in a microscale heterogeneous thermoelectric system. It is common knowledge that a finite time is needed to complete any physical interactions in materials. The two most essential factors in thermal sciences are the heat flux vector and temperature gradient, which occur at different times during the transport process. This leads to the concept of thermal lagging. The dual-phase-lag model is utilized to determine the interaction of these two factors, as mentioned earlier, by using two relaxation constants, ({tau }_{T}) and ({tau }_{q}), to explore the lagging behavior. The magnitudes of these two constants play an essential role in energy transport in microscale and nanoscale thermal systems. A high-order hyperbolic partial differential equation is utilized to determine the cause-and-effect interaction for a particular pair of relaxation constants. Ultimately, one needs to solve a coupled, but moderately simple, system of finite difference equations that involves the temperature and heat flux simultaneously. The effects of relaxation constants and temperature-dependent material properties in semiconductor thermoelements are thoroughly examined. The microscale heat transport phenomenon plays a significant role in thermal management technology. The study confirmed that the dual-phase-lag model is an appropriate design tool for engineers in the thermoelectric industry.

The thermophysical properties of choline salicylate ([Ch][Sal]), an active pharmaceutical ingredient ionic liquid (API-IL), in (0.1, 0.2, and 0.3) mol‧kg⁻¹ aqueous amino acids (_L-alanine, _L-proline, _L-arginine) solutions have been measured at 298.15 K. Density, speed of sound, viscosity, refractive index, and electrical conductivity of [Ch][Sal] in these solutions at varying concentrations were measured. The standard partial molar volumes, (mathop Vnolimits_{varphi }^{0})  , partial molar isentropic compressibility’s, (kappa_{varphi }^{0}) , viscosity B-coefficients, molar refractions, (mathop Rnolimits_{D}), ion association constants, K_A, and limiting molar conductivities, Λ⁰, were derived. The values of (mathop Vnolimits_{varphi }^{0}) for [Ch][Sal] increased from 196.76 cm³‧mol⁻¹ to 200.56 cm³‧mol⁻¹ in _L-alanine solutions but decreased to 192.03 cm³‧mol⁻¹ in _L-arginine solutions, indicating stronger ion-polar interactions with _L-alanine. Similarly, (kappa_{varphi }^{0}), shifted from negative in water to positive values for _L-alanine and remained positive for _L-proline and _L-arginine, suggesting hydrophobic effects in longer alkyl chains. The viscosity B-coefficients showed an increasing trend in _L-arginine solutions, indicating stronger solute–solvent interactions. To further investigating the interactions in the studied systems, COSMO-based analysis was employed. Results indicate the presence of strong ion-polar interactions between [Ch][Sal] and _L-alanine. These results provide crucial insights into the physicochemical behavior of API-ILs in biologically relevant systems.

Trombe walls represent an effective passive solar heating strategy that can significantly improve indoor thermal comfort and building energy efficiency. However, their overall performance strongly depends on geometric configuration and heat transfer enhancement techniques, which remain under continuous optimization. This study investigates how the integration of V-shaped fins influences the thermal behavior and energy performance of a Trombe wall system. Four fin configurations: 6, 8, 10, and 12 fins were examined experimentally and numerically under controlled conditions (ambient temperature of 16 °C and solar radiation of 750 W m^–2). A three-dimensional CFD model was developed and validated using ANSYS FLUENT based on the finite-volume approach, while experimental data were used for verification. The results demonstrate that increasing the number of fins enhances both convective heat transfer and airflow circulation inside the wall. The thermal efficiency increased from 18.20 % for the unfinned configuration to 26.46 % for the 12-fin case, corresponding to a 45.38 % improvement. Numerical and experimental results showed close agreement, with deviations ranging from 1 to 3 °C. The findings confirm that incorporating V-shaped fins substantially improves the thermal performance and temperature uniformity of Trombe walls, providing an effective design pathway for sustainable and energy-efficient buildings.