Liquid Temperature Research Articles

Experimental and 4NTU-Le heat and mass transfer model theoretical analysis based on a novel internally cooled liquid desiccant dehumidifier

A microchannel flat tube-rectangular corrugated fin type new internally cooled liquid desiccant dehumidifier (NIC-D) was designed. It was found that the existing NTU-Le heat and mass transfer model is not well adapted to its physical phenomena. To respond to the study gap, this study proposed a new 4NTU-Le heat and mass transfer model based on the physical characteristics of NIC-D in the dehumidification process. Through theoretical derivation and experimental verification, the heat and mass transfer process between air, liquid desiccant and cooling water was analyzed, and the heat and mass transfer mechanism among the three fluids was deeply revealed. On this basis, a new method for calculating heat and mass transfer coefficients was given in combination with the model, which was more adapted to the calculation of the 4NTU-Le model in terms of concept. In addition, this method summarised the correlation between heat and mass transfer from experimental data to predict and characterize the performance of the NIC-D dehumidification process. The results show that the 4NTU-Le mathematical model, the new method for calculating heat and mass transfer coefficients, has high accuracy, in addition to the applicability of the Nu and Sh correlations. According to the analytical results of the validation experiments, the errors between the calculated and experimental values of air outlet temperature, liquid desiccant outlet temperature, cooling water outlet temperature, and air outlet humidity content are within 8.0 %, 15.0 %, 10.0 %, and 10.0 %, respectively, and the absolute average errors AAD are 1.73 %, 6.35 %, 1.46 %, and 3.18 %, respectively. Decreasing the temperature of imported liquid desiccant is a valuable way to improve dehumidification efficiency and energy effectiveness. For every 1.0 °C reduction in the temperature of imported liquid desiccant, the dehumidification efficiency and energy effectiveness increased by 2.6 % and 1.1 %, respectively.

Compositional design of slag for homogenized rare earth treatment by slag-steel interaction under vacuum

Reduction of La2O3 in molten slag by the C in liquid steel during slag-steel interaction under vacuum is expected to achieve homogenized La treatment for steel. To develop the appropriate slag for La treatment, the liquidus temperature, viscosity and fluoride vaporization of 50 wt%CaF2-30 wt%CaO-(20-x)wt%Al2O3-xwt%La2O3 slag were studied, as well as the La distribution between the La2O3 containing slag and GCr15 steel under vacuum. The results show that the liquidus temperature of slag firstly decreases with the increase of La2O3 content from 0 to 5 wt%, and then increases as the La2O3 content continuously increases. The LaAlO3 phase starts to precipitates in slag when La2O3 content of slag exceeds 10 wt%, which accounts for the increases on liquidus temperature. Thus, the La2O3 content in slag should not exceed 15 wt%. La2O3 can play the depolymerization role on slag melts, which contributes to the decrease in slag viscosity. Furthermore, the increase of La2O3 content in slag decreases vapor pressure of CaF2 and AlF3, and fluoride vaporization is inhibited. Rare earth treatment with considerable La content through slag-steel interaction that dissolved C in liquid GCr15 steel reacts with La2O3 in molten slag is realized under vacuum. The La content in GGr15 equilibrated with slag bearing 15 wt% La2O3 under 0.5–1 kPa is 0.0135 wt%.

Non-isothermal wicking in polymer sintered bead wicks: Experimentation, analytical solutions, and numerical validation

Though models and applications abound for spontaneous imbibition of liquids into porous media (also called wicking), this is perhaps the first attempt to propose (and rigorously test) any model under non-isothermal conditions. This paper evaluates non-isothermal wicking phenomena through experiments, theoretical models, and numerical simulations. Experiments measure the wicking height of hexadecane in a heated beaker with a polypropylene wick at room temperature. An analytical solution predicts the wicking rate based on temperature-sensitive liquid properties, such as viscosity, surface tension, and density. Three temperature models are introduced: Liquid Temperature Model, Average Temperature Model, and Dynamic Temperature Model. The first two models incorporate temperature-induced changes in liquid properties but have limitations. The Liquid Temperature Model overestimates wicking height, while the Average Temperature Model improves predictions but still faces challenges. The Dynamic Temperature Model, using numerical simulation, accurately calculates fluid properties at dynamically determined temperatures, leading to better predictions of wicking height. Comparisons with experimental data show increasing accuracy across the three models. The Dynamic Temperature Model also successfully demonstrates temperature transitions in the wick observed through thermal imaging.

Uniqueness of glasses prepared via x-ray induced yielding

The yield point marks the beginning of plastic deformation for a solid subjected to sufficient stress, but it can alternatively be reached by x-ray irradiation. We characterize this latter route in terms of thermodynamics, structure and dynamics for a series of GeSe3chalcogenide glasses with different amount of disorder. We show that a sufficiently long irradiation at room temperature results in a stationary and unique yielding state, independent of the initial state of the glass. The glass at yield is more disordered and has higher enthalpy than the annealed glass, but its properties are not extreme: they rather match those of a glass instantaneously quenched from a temperature 20% higher than the glass-transition temperature. This is a well-known, key temperature for glass-forming liquids which marks the location of a dynamical transition, and it is remarkable that different glasses upon irradiation head all there.

Energy, Exergy, and Economic Performance Comparison and Parametric Optimization of Organic Rankine Cycles Using Isobutane, Isopentane, and Their Mixtures for Waste Heat Recovery

The possibility of applying the organic Rankine cycle (ORC) to further recycle the low-grade waste heat efficiently is studied in the present work. The energy, exergy, and economic models of the ORC system are established, and the isobutane, isopentane, and their mixtures are selected as the organic working mediums (OWMs). Due to the slip characteristics of mixed OWM, four operational conditions of the ORC system are proposed, and then the contrastive analysis of energy, exergy, and economic performances under the four operational conditions are conducted. Finally, the optimal mixture mass fraction and crucial parameters of the ORC system are separately determined through the bi-objective optimization. The results show that the ORC system using the mixed OWM can achieve a larger net power output and exergy efficiency by comparing the pure OWM when the condensing temperature is set as the saturated vapor temperature during the condensation process. The electricity production cost first rises and then decreases with the rising mass fraction of isobutane in mixed OWM, and the ORC system using the isopentane can achieve the smallest electricity production cost. By taking the low-grade flue gas of 433.15 K as the ORC heat source, four operational conditions have the same optimal ORC crucial parameters, namely the evaporating temperature of 393.15 K, condensing temperature of 308.15 K, and superheat degree of 0 K. The pure OWM of isobutane can achieve better overall performance by setting the condensing temperature as the saturated liquid temperature.

Thermotropic liquid crystalline and fluorescence resonance energy transfer under temperature excitation of imidazolium salt/CdTe quantum dots composites

ABSTRACT The optical characteristics and surface area of quantum dots (QDs) render them a compelling platform for the development of composite materials based on fluorescence resonance energy transfer (FRET). A novel luminescent liquid crystal nanocomposite (CBphCM-CdTe) has been successfully prepared through the ionic self-assembly route using imidazolium salt (CBphCM) and CdTe QDs. DSC and POM analyses confirm that CBphCM-CdTe undergoes the smectic A and C phases, but its liquid crystal temperature range is narrower compared to that of pure CBphCM. Concurrently, CBphCM-CdTe exhibits excellent fluorescence characteristics. Increasing temperature serves as a trigger for fluorescence resonance energy transfer between CdTe QDs and CBphCM, wherein the fluorescence of CdTe QDs is quenched, while the fluorescence intensity of CBphCM increases with rising temperature. A strong correlation exists between temperature and fluorescence intensity within the liquid crystal temperature range. Such thermochromic materials are anticipated to facilitate innovative development in dynamic thermo-optical sensing, thereby enabling enhanced control over light manipulation in stimuli-responsive devices.

Compartmental modeling of CO2 absorption in a rotating packed bed

Capturing carbon dioxide (CO2), i.e., the primary greenhouse gas that contributes to climate change, from CO2 containing gas mixtures in various industrial sectors, e.g., natural gas processing and treating refinery off-gases, is necessary. Rotating packed beds (RPBs) have shown great efficiency in CO2 capture from flue gases with an appreciable intensification in the absorber size compared to the conventional packed bed absorbers. Successful commercialization of an RPB technology requires a comprehensive understanding of its performance under various operating conditions, process configurations, and for different solvents. In this study, we presented a mathematical model describing the performance of an RPB absorber for CO2 capture by aqueous amine solutions. We established the compartmental model based on two plug-flow reactors for gas and liquid phases. We validated this model adopting two sets of experimental data from literature. We considered reaction rates of all compounds in the system in the model. We, subsequently, employed the validated model to highlight the potential parameters in enhancing the overall CO2 recovery by an RPB absorber. The developed model takes advantage of acquired knowledge and data from literature based on years of numerical studies on RPBs. We studied the effects of operating conditions, such as inlet gas and liquid flow rates, amine fraction, rotating speed, and inlet liquid and gas temperatures on the performance of an RPB by the validated model. Although we initially developed the model for the CO2-monoethanolamine (MEA) solvent, we also studied the effect of changing the solvent to methyl diethanolamine (MDEA) and piperazine (PZ) on the overall absorption performance of an RPB absorber. We further adopted the developed model as a design tool to assist us in replacing a pilot- and an industrial-scale packed bed absorber with corresponding single RPB absorbers.

Extraction, characterization, and antineoplastic effect of Macadamia nut extracts against cutaneous melanoma cells: a comprehensive study focused on SK-MEL-28 cells

In this study the potential of macadamia nut extracts against cutaneous melanoma cells was evaluated. The extracts were obtained through ultrasound-assisted extraction (UAE), where the effects of solid–liquid ratio, irradiation power, and temperature were assessed. Additionally, pressurized ethanol extraction (PEE) was performed, focusing on the impact of pressure, flow rate, and temperature. In both methods, a gas chromatography was used to characterize the extracts in terms of fatty acids. To evaluate the antineoplastic effect, SK-MEL-28 cells were treated with different concentrations of extracts (0.01–10 mg.mL−1) for 24 h. The MTT assay was used to assess cell viability. Furthermore, mitochondrial transmembrane potential and apoptotic bodies formation were evaluated. The highest global yield value obtained by UAE and PEE was 52.73 % and 38.84 %, respectively. The chemical characterization indicated that the main fatty acids were the methyl cis-9 oleate followed by methyl palmitoleate, methyl palmitate. With respect to the antineoplastic effect, both macadamia extracts significantly reduced melanoma cell viability, lowered mitochondrial transmembrane potential, and induced the formation of apoptotic bodies. Extract from UAE had superior antineoplastic effect than extract PEE. This fact is based on the influence of extraction techniques on the concentration of extracted compounds. The results suggest that macadamia extracts have potential to be used as adjuvant therapy in melanoma context.

Simultaneous measurement of liquid refractive index and temperature based on the birefringence response of a water-filled D-shaped photonic crystal fiber

In this paper, a water-filled D-shaped photonic crystal fiber (WFDSPCF) sensor based on the birefringence response for simultaneously measuring the liquid refractive index (LRI) and liquid temperature (LT) is proposed. We undertake theoretical and simulation calculations, and the results show that the proposed WFDSPCF can achieve ultrahigh LRI and LT sensitivities when operating around the group birefringence turning point. By optimizing the structural parameters, the proposed WFDSPCF sensor can achieve LRI and LT sensitivities of -25642.86 nm/RIU and 12.8 nm/°C, respectively. In addition, in order to eliminate the sensing crosstalk between the LRI and LT, a parallel Lyot interferometer structure is also proposed. The proposed WFDSPCF sensor is expected to have potential use in biochemical sensing, measurement science, and environmental monitoring.

Highly sensitive liquid level and temperature sensors based on all-fiber intermodal interferometers

Abstract Fiber optic-based precise measurements of liquid level and temperature are crucial for remote controlling in pharmaceutics, chemistry, and bromatology. Thus, it is essential to monitor liquid level and temperature simultaneously. In this paper, we propose all-fiber intermodal interferometers for highly sensitive liquid level and temperature measurements. We fabricated two different structures of single mode fiber-no core fiber-single mode fiber (SMF-NCF-SMF). One of them was used to measure the liquid level when the liquid soaked the NCF, and the other one was further coated with PDMS thermal-optic material and utilized to detect temperature. The measurement sensitivity of liquid level was 580 pm/mm within the range of 0-20 mm, while that of temperature was 1 nm/°C within the range of 28-51°C. A matrix was finally obtained by demodulating the measurements of liquid level and temperature. The proposed liquid level and temperature sensors, exhibiting the merits of high sensitivity, easy fabrication, and low cost, could be a candidate for precise and remote monitoring of liquid levels.

Medium-Range Structural Order as the Driver of Activated Dynamics and Complexity Reduction in Glass-Forming Liquids.

We analyze in depth the Elastically Collective Nonlinear Langevin Equation theory of activated dynamics in metastable liquids to establish that the predicted inter-relationships between the alpha relaxation time, local cage and collective elastic barriers, dynamic localization length, and shear modulus are causally related within the theory to the medium range order (MRO) static correlation length. The latter grows exponentially with density for metastable hard sphere fluids and as a nonuniversal inverse power law with temperature for supercooled liquids under isobaric conditions. The physical origin of predicted connections between the alpha time and other metrics of cage order and the thermodynamic inverse dimensionless compressibility is fully established. It is discovered that although kinetic constraints from the real space first coordination shell are important for the alpha time, they are of secondary importance compared to the consequences of the more universal MRO correlations in both the modestly and deeply metastable regimes. This understanding sheds new light on the theoretical basis for, and prior successes of, the predictive mapping of chemically complex thermal liquids to effective hard sphere fluids based on matching their dimensionless compressibilities, a scheme we call "complexity reduction". In essence, the latter is equivalent to the physical requirement that the thermal liquid MRO correlation equals that of its effective hard sphere analog. The mapping alone is shown to provide a remarkable level of quantitative predictive power for the glass transition temperature Tg of 21 molecular and polymer liquids. Predictions for the chemically specific absolute magnitude and growth with cooling of the MRO correlation length are obtained and lie in the window of 2-6 nm at Tg. Dynamic heterogeneity, elastic facilitation, and beyond pair structure issues are briefly discussed. Future opportunities to theoretically analyze the equilibrated deep glass regime are outlined.

SOME COMMENTS ON THE NATURE OF GLASSES

ABSTRACT I undertake a brief presentation of the early history of the development of our modern understanding of glass-forming liquids that provides a look at how the scientific and technological communities were viewing the state of the art and how the knowledge in the field developed. I discuss aspects of our understanding from how the Vogel–Fulcher–Tammann (VFT) equation became known to questions about the development of the concept of the “ideal” glass transition. The framework for this history leads us to ask whether some of the cautions that the pioneering researchers provided should have been taken more seriously by the community. I discuss, in particular, the view presented by Tammann and Hesse [Z. Anorg. Allg. Chem. 156, 245 (1926)] cautioning that the apparent singularity of the viscosity at a finite temperature was not physical and how the, now famous, VFT equation is accurate for interpolation rather than for extrapolation. The other point is the strong sense by much of the glass community that the so-called Kauzmann paradox [Chem. Rev. 43, 219 (1948)] is fundamental to glass-formation despite the comment by Kauzmann himself that the extrapolation of the entropy to negative values is “operationally meaningless.” I build on these ideas through a presentation of my own data and that of others that addresses the Tammann and Hesse comment through experiments that show that there is not a viscosity (or relaxation time) divergence near to the Kauzmann or VFT temperatures, and I show that the equilibrium entropy of a polymer that cannot crystallize shows no evidence of an ideal glass transition that is often invoked as a means of avoiding the Kauzmann paradox. In addition to providing some sense of the history of time (or a brief history of time and temperature in glass-forming liquids, with apologies to Stephen Hawking) and viscosity, I think that the data presented lead to the conclusion that much of our understanding of the problem of glass-formation is based on misleading interpretations of the original works as well as being inconsistent with the newer data that have been published over that past 25 yr or so. On an optimistic note, there are newer models that do not rely on the VFT divergence or the Kauzmann paradox to account for glass-formation in supercooled or equilibrium liquids. In addition, the experimental situation clearly leads to the possibility of deeper investigations into the “deep glassy state” through “finessing” the geological timescale issue of creating equilibrium glasses. Such investigations are ultimately important to understanding behavior of glassy materials, especially polymers, that are used deep in the glassy state, but still close enough to the glass temperature that models able to reliably predict their behavior require better representations of glass-formation to engineer their performance.

Modeling, simulation, and optimization of multi-stage equilibrium extraction of phenolic compounds from grape pomace

The seasonal nature of wine production results in the accumulation of significant quantities of grape pomace (GP) during harvest, presenting management challenges for wineries that traditionally regard this solid byproduct as low-value waste. However, extracting phenolic compounds (PCs) from GP offers a promising avenue for creating bioactive extracts for use in the food, pharmaceutical, and cosmetic industries. This study develops a mathematical model for predicting the total phenolic content (TPC) and total dissolved solids (TDS) in liquids obtained from multi-equilibrium-stage extraction processes using a 50% aqueous ethanol solution to recover PCs from Tannat GP. The model is applicable across a wide range of TPC and TDS concentrations in the liquid (0.2–45.4 gGAE/L for TPC and 1–118 g/L for TDS) and extraction temperatures between 30 and 70 °C. It is used to determine the optimal operational conditions of a Shanks extraction system, either to minimize fresh solvent consumption or to maximize selectivity for PCs extraction, achieving a desired extraction yield with a specified number of extraction vessels.

Hysteresis of unfrozen water content of tailing mud with freeze-thaw and its correlation with electrical conductivity

Identifying the correlation between the hysteresis of unfrozen water content and the electrical conductivity (EC) of tailing mud with freeze-thaw is essential for determining the range of frost hazards in tailings ponds by field conductivity measurement and enabling targeted treatment in coastal and seasonally frozen areas. In this study, dynamics of unfrozen water content and temperature of saturated tailing mud samples with 0.0–5.0 % NaCl were evaluated with 5TM sensor while the EC with the frequency domain reflectometry (FDR) sensor. Results show that unfrozen water hysteresis of tailing mud with freeze-thaw occurred below phase-change temperatures, with the cooling section above the warming. The area of hysteresis curve rose upon higher salinity or fewer freeze-thaw cycles. Phase-change temperatures of tailing mud, including freezing and thawing points, depressed with higher salinity but were less affected by freeze-thaw cycles, with the former coinciding with the liquidus line of NaCl solution while the latter located above. The EC curve also exhibits hysteresis with freeze-thaw and the initial salinity determines both the maximum EC value and the slope logEC/T below phase-change temperatures. It was concluded that the unfrozen water content, converted salt concentration and EC of frozen tailing mud show synchronous changes. A modified Michalowski model, with phase-change temperatures and residual unfrozen water content respectively simplified as proportional and exponential functions of initial salinity, was established to characterize the unfrozen water hysteresis of tailing mud with freeze-thaw cycles. A simple EC model with hysteresis was then developed by approximating the EC of frozen tailing mud as a power function of the converted salt concentration, which was applied to the tailing mud with 0.5–5.0 % NaCl in the range of −20 °C up to phase-change temperatures.

Numerical Study on Composite Multilayer Insulation Material for Liquid Hydrogen Storage

This study investigated the heat transfer characteristics of composite multilayer insulation (MLI) materials used for the storage and transport of liquid hydrogen at cryogenic temperatures. This research focused on analyzing the effects of thermal boundary temperature, total layer count, and vacuum level on the heat flux through the insulation material. Based on the layer-by-layer model, a heat transfer model of composite MLI was constructed. This research introduces a novel method for analyzing the heat transfer properties of composite MLI in the liquid hydrogen temperature range. Results indicate that heat flux increases with higher thermal boundary temperatures, with the MLI layers near the cold boundary playing a critical role in overall insulation performance. Additionally, numerical analysis was conducted to examine the impact of different material combinations and variations in vacuum level on heat transfer characteristics. Findings reveal that adding spray-on foam insulation reduces heat flux by 20.76% compared to using MLI alone. Furthermore, increasing the total number of MLI layers effectively mitigates heat flux increase, achieving an optimal heat flux of 0.5377 W/m2 with a total of 50 layers.

Simultaneous measurement of temperature and refractive index based on fiber optic Fabry–Pérot cavity in batteries

Abstract A Fabry-Pérot (FP) sensor for simultaneous measurement of refractive index and temperature of an all-fiber synchronous liquid based on the Vernier effect is proposed, special application for internal monitoring of lithium-ion battery electrolytes. The theoretical model of high sensitivity cascade Fabry-Pérot interferometer (PFPI) is established, the sensitivity amplification mechanism of PFPI is analyzed in detail, the perfect matching scheme for measuring the refractive index of the electrolyte inside the battery is designed according to the matching conditions of the optical path, and the corresponding sensors for simultaneous measurement of the temperature and the refractive index are fabricated. The experimental results show that the sensor has a maximum refractive index sensitivity of 15391.5033 nm/RIU, a good linear fit, and can effectively monitor the refractive index change of the electrolyte by 10-4 orders of magnitude during normal charging and discharging of lithium-ion batteries. Compared to traditional epoxy adhesive bonded or laser processed FP sensors, this all-fibre optic structure not only improves temperature and corrosion resistance, but also significantly reduces temperature cross-sensitivity. Its small size and excellent resistance to high temperature and corrosion ensure the sensor's excellent response and broad application prospects in monitoring the refractive index of the electrolyte in 18650 lithium-ion batteries, which provides effective technical support for monitoring the health status of batteries and detecting early safety issues.

The Concept of the Estimation of Phase Diagrams (An Optimised Set of Simplified Equations to Estimate Equilibrium Liquidus and Solidus Temperatures, Partition Ratios, and Liquidus Slopes for Quick Access to Equilibrium Data in Solidification Software) Part I: Binary Equilibrium Phase Diagrams

This paper presents equations derived from thermodynamic equations for calculating the liquidus and solidus temperatures, the liquidus slope, and the partition ratio for solidification simulations. The constants of these equations can be easily determined from measurement data obtained by digitalisation from known diagrams or can be calculated using a CALPHAD-based software. ESTPHAD has a hierarchical system; the developed functions of the binary systems are used in the calculation of the functions of the ternary systems, the functions of the ternary systems in the calculation of the function of quaternary systems, and so on. The developed method is demonstrated by processing the liquidus and solidus of Si–Ge isomorphous and Al–Mg and Al–Si eutectic equilibrium phase diagrams. The use of this method for calculating the functions of ternary systems will be shown in Part II. The advantages of this method are that the equations are simple, can be determined very quickly, and can be built into the simulation software very easily. The most significant advantage is that the calculation time is shorter by some order of magnitude than that of a CALPHAD-type calculation.

A consistent treatment of mixed‐phase saturation for atmospheric thermodynamics

AbstractIce processes are integral to the formation and maintenance of high‐level clouds and can contribute substantially to the buoyancy of deep moist convection. These processes are represented in modern microphysics parameterisations but are commonly ignored in theoretical treatments of moist thermodynamics. While many thermodynamic variables can be defined uniquely for saturation with respect to liquid water and ice, it is desirable to account for the presence of mixed‐phase condensate, which is common in real clouds. Here, a simple yet novel representation of mixed‐phase saturation is introduced. Using this approach, analytical equations are derived for a variety of thermodynamic variables under mixed‐phase conditions. These include mixed‐phase versions of the saturation vapour pressure, saturated lapse rates, isobaric wet‐bulb temperature, and equivalent potential temperature. A new formulation of the ice–liquid water potential temperature is also presented, together with a method for calculating the mixed‐phase pseudo wet‐bulb temperature and wet‐bulb potential temperature. In addition, two new thermodynamic quantities are introduced: the isobaric saturation‐point temperature, a mixed‐phase analogue of the dew‐point and frost‐point temperatures, and the lifting saturation level, a mixed‐phase analogue of the lifting condensation and lifting deposition levels. Differences between each mixed‐phase variable and its liquid‐ and ice‐only counterparts are quantified across a wide range of atmospheric conditions. A Python library for evaluating these variables, developed during the course of this work, is also briefly introduced.

Liquidus temperatures in the La2O3-SrO-TiO2-ZrO2-Fe2O3 system: Calculation and experiment

Ceramics based on the La2O3-SrO-TiO2-ZrO2-Fe2O3 system is of considerable interest for the development of the materials based on high-entropy oxides when their high-temperature endurance is required. However, limited information on its high-temperature behavior greatly limits its applications. In the present work, the potential of the geometric method for liquidus temperature calculation (GMLTC) in five-component oxide systems using data on the corresponding binary systems is verified for the first time with the example of the La2O3-SrO-TiO2-ZrO2-Fe2O3 system. The liquidus temperatures in the studied system calculated accordingly were experimentally confirmed by visual polythermal analysis within the limits not exceeding 10 % of the determined melting temperature. This allows us to recommend the proposed GMLTC approach for prediction of the position of liquidus curves in multicomponent oxide systems, which is particularly important for the calculations of liquidus temperatures of high-entropy oxides with unique physicochemical properties valuable for application at high temperatures up to 3000 K.

Experimental study of a gas-coupled pulse tube cold finger with both active piston and cold inertance tube as phase shifters for 8 K applications

Stirling-type pulse tube cryocoolers (SPTCs) working at temperatures below 8 K represent advantages in very long wave infrared detection, terahertz detection, etc. It is essential for SPTCs to obtain reasonable distribution of impedance to achieve good cooling performance. However, adjusting the distribution of impedance to an optimal value is hard as temperature decreases. It is critical for muti-stage SPTCs working at temperatures below 8 K to arrange appropriate phase shifter at each stage. This paper introduces a gas-coupled pulse tube cold finger with active piston and cold inertance tube as phase shifters for 8 K applications. The cold finger consists of pulse tube 1 (PT1) which works at liquid hydrogen temperatures and pulse tube 2 (PT2) which operates at liquid helium temperatures. Active piston is the phase shifter of PT1. It could adjust the impedance to any value theoretically and make the cold finger highly adaptable. The phase shifter of PT2 is cold inertance tube and gas reservoir. Cold inertance tube and gas reservoir has simple structure which makes it suitable for space applications. The impact of frequency and operating parameters of active piston on no-load temperature is investigated by experiments. A lowest no-load temperature of 5.16 K is achieved in experiments. The effect of temperature distribution of cold finger on cooling capacity at 8 K is also researched. A cooling capacity of 74 mW at 8 K can be obtained with the electric input power of 177.5 W and a pre-cooling capacity of 9.1 W/70 K.