Thermal Test Research Articles

Effect of deformation temperature on the dynamic recrystallization mechanism and dynamic precipitation behavior of Mg-Gd-Nd-Zr alloy

The deformation temperature is an important factor influencing the thermal deformation behavior of alloys. In this paper, thermal compression tests of Mg-Gd-Nd-Zr alloy were carried out at 350 ∼ 500 °C using the Gleeble-3800 thermal simulator, and the dynamic recrystallization (DRX) mechanism and microstructure evolution of the alloy were investigated by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results show that the basal slip a and pyramidal slip a+c were consistently high activity at the test temperatures. As the temperature increased, the pyramidal slip a was gradually activated. At 350 °C, monolayer necklace-like dynamic recrystallized (DRXed) grains were formed around the initial grains via discontinuous dynamic recrystallization (DDRX). At 400 ∼ 450 °C, the monolayer DRXed grains expanded into the initial grain via continuous dynamic recrystallization (CDRX) to form multilayer necklace-like DRXed grains. However, at 500 °C, no necklace-like structure was formed around the initial grains. The initial grains were split into subgrains by low angle grain boundaries (LAGBs), which continuously absorbed dislocations and rotated for DRX. In addition, at 350 ∼ 400 °C, the alloy produced significant precipitation bands (mainly β phase). Above 450 °C, the dynamic precipitation was significantly attenuated. Precipitates greater than 200 nm could well impede dislocation movement and induce DRX nucleation. Nevertheless, the precipitates at the grain boundaries of the DRXed grains in turn pined the grain boundaries, refining the DRXed grains.

Thermal control system of Space Laser Communication Payload

Abstract To ensure the high-quality communication requirements of laser communication payload, the thermal control system is designed. Firstly, the structure and optical system of laser communication payload are introduced. Secondly, the task characteristic is analyzed. Then, the thermal design of laser communication payload is carried out with thermal conduction, thermal insulation, thermal dissipation and heating. Finally, a thermal balance test is performed. The test results show that the temperature of the optical system is 20.9 °C∼22.1 °C, the temperature of the detector is 15.5∼20.7 °C, the temperature of the pointing mechanism is 14.9 ∼ 17.5 °C, the temperature of the star sensor is 9.9 ∼ 18.7 °C, the temperature of the base is 13.9 ∼ 21.8 °C, and the temperature of the electric box is 14.7 ∼ 22.8 °C. The results of the test satisfy the requirements of the temperature indicators, indicating that the thermal design scheme is reasonable and feasible.

Sustainable aviation fuel: Impact of alkene concentration on jet fuel thermal oxidative test (JFTOT)

AbstractOf the processes that are approved to produce synthetic kerosene for use in jet fuel, about half produce olefinic kerosene that is hydrotreated. The alkene concentration in synthetic kerosene is indirectly regulated through the thermal oxidative stability specification. Perceptions about the deleterious influence of alkenes on thermal oxidative stability suggest that olefinic kerosene must be deeply hydrogenated. The extent of olefin saturation required has economic implications. To evaluate what an acceptable alkene concentration in synthetic kerosene is, the impact of alkene concentration on the outcome of the jet fuel thermal oxidative stability test (JFTOT) performed at 325°C in accordance with the ASTM D3241 standard test method was experimentally evaluated. Model synthetic kerosene mixtures to which different concentrations of alkenes (1‐decene, α‐methylstyrene, indene) were added, as well as control samples were studied. In the concentration range investigated, up to 10 wt% 1‐decene, 5 wt% α‐methylstyrene, and 2 wt% indene did not lead to increased fouling in the JFTOT. Fouling passed through a minimum value with increasing alkene concentration and alkene concentration on its own was a poor predictor of thermal oxidative stability. Analysis of the kerosene collected after passing through the JFTOT found measurable changes in density and refractive index. Dissolved oxygen reacting during thermal oxidative stability testing was accounted for mostly in oxygen‐containing products in the kerosene boiling range, which indicated that the heavier products were mainly hydrocarbon in nature. In addition to initiation by autoxidation, the investigation also pointed to the existence of a second thermally initiated fouling pathway that does not require the presence of oxygen.

The changes in selected properties of flax fibre-reinforced biocomposites affected by plant modifier concentration

The application of the sustainable materials is one of the basic steps towards environmentally friendly and resource-efficient society. The aim of the study was to characterise the effects of the natural plant modifier concentration on properties of the biocomposites. The paper describes the influence of tannic acid (TA) concentration on flax fibre-reinforced biocomposites. The prepared biocomposites contained polylactide in 20 wt% and flax fibres (Linum usitatissimum) in 80 wt%, while the modifier concentrations varied from 1 % to 10 %. The manufacturing methods included extrusion and injection moulding of the biocomposites. The evaluation of the effects of modifier concentration on selected parameters of biocomposites was conducted using mechanical tests - tensile tests, thermomechanical - dynamic mechanical analysis (DMA), and thermal tests - differential scanning calorimetry (DSC) and thermogravimetry (TG). Additionally, biocidal and wettability studies were conducted. The examination results revealed, that 5 % is an optimum concentration of modifier which positively affected both mechanical and biocidal properties. The efficient use of modifiers can help in natural resources conversion and minimization of environmental impacts.

Safer operating areas (SOA) of cylindrical lithium-ion battery – A probabilistic approach

This study introduces a real-time probabilistic safety assessment of a 18650 cylindrical battery. The physics-based failure scenarios from battery abuse are mapped onto Bayesian Network framework, enabling a quantitative estimation of monitoring parameters, health indicators and loss of control events. The model (encompassing multiple states, weightage factors, interdependencies, and uncertainties) is validated with 70 experimental data points of the same geometry, comprising 4 categories of abuses (surface heating, fast overcharging, external short circuit, and internal deformation). Through testing, probabilistic safety thresholds are established for 3 observed events: gas formation, venting, and fire and explosion.Sensitivity analysis reveals state of charge (at SOC > 50 %) and surface temperature (at Tsurf > 90°C) as the most influential parameters while inadequate cooling system and current interrupt device (CID) as influential safeguards for thermal runaway and fire to occur. Moreover, the identified safety thresholds are subjected to validation and testing against multiple health indicators to draw important insights. Probability, P(fire)deformation>P(fire)surface heat as internal deformation lowers onset to thermal runaway. In culmination, a safer operating area (SOA) is proposed, leveraging the identified thresholds and most sensitive parameters. The proposed SOA with 4 distinct boundaries is not only consistent with the temporal variations in cell temperature during thermal abuse test, but also provides a robust approach to monitor the safety of a battery.

Pyrolysis mechanism of silicone rubber thermal protection system materials in service environment

The excellent oxidation and ablation resistance of silicone rubber thermal protection system (TPS) materials have made them extensively utilized in large-area thermal protection applications, such as ramjet engines and spacecraft reentry capsules, where air is present in the service environment. The ablation resistance is significantly influenced by the pyrolysis reactions, which serves as the foundation for subsequent ceramic transformation and the development of anti-erosion structures. The majority of previous research has been conducted in inert gas environments. To investigate the pyrolysis mechanism of silicone rubber TPS materials in realistic service environments, thermal analysis tests were performed using a range of analytical instruments including a thermal analyzer, mass spectrometer, infrared spectrometer, and X-ray photoelectron spectrometer from room temperature up to 1300 K in air atmosphere and compared with the results in argon atmosphere. The results demonstrate that silicone rubber TPS materials undergo both pyrolysis and oxidation reactions in air atmosphere. The primary pyrolysis of the matrix is attributed to cyclization reactions and side-chain cross-linking reactions. In comparison to argon atmosphere, the oxidation reaction produces a greater amount of organic gases, thereby diminishing the extent of cross-linking reaction and the thermal stability of the pyrolysis residue. The prolonged exposure to elevated temperatures allows for an extended duration of oxidation reactions, consequently diminishing the long-term thermal stability of TPS materials. The increase in mass of TPS materials at temperatures exceeding 1100 K can be attributed, in part, to the formation of new organic groups through oxidation reactions. The observed morphology of the residue, along with the weight gain from oxidation and SiO2 formation, promotes ceramic transformation of the materials at elevated temperatures.

Temperature-dependent acoustic emission characteristics and statistical constitutive model of granite under uniaxial compression

Understanding the temperature-dependent mechanical behavior and fracture characteristics of granite is crucial for many engineering projects. In this study, the real-time temperature curves of granite specimens were obtained during the heating and cooling process, and the thermal treatment tests were conducted. The physical properties of the specimen before and after thermal treatment, including mass, volume, and P-wave velocity, were measured. The acoustic emission (AE) signal in the uniaxial compression is monitored. The results indicate that the physical properties of granite deteriorate with temperature, while the mechanical properties show two effects of thermal strengthening and thermal weakening. This phenomenon is comprehensively analyzed by literature statistical data and optical microscopic observation. Furthermore, the AE characteristic is strongly dependent on temperature. High temperature induces more AE ring count to appear in the early stage of loading. As the temperature increases, the crack initiation stress decreases and the table crack propagation stage becomes longer. The attenuation of high-frequency signals and the enhancement of low-frequency signals are related to the development and interaction mechanism of thermally-induced crack and stress-induced crack. At 600 °C, the global b-value increases significantly. Meanwhile, the evolution of dynamic b-value helps explain the failure process of granite under axial load after thermal treatment. In addition, a new thermo-mechanical damage statistical constitutive model of granite considering temperature effects is proposed by introducing AE parameters. The main advantages of this model can well fit the nonlinear behavior of granite in the early loading stage after thermal treatment, and reflect the failure process of granite before the peak value.

INVESTIGATION OF THE REFRACTORY PROPERTIES OF KANKARA CLAY FOR ENGINEERING AND INDUSTRIAL APPLICATIONS

The refractory properties of Kankara clay have been investigated with a view to understanding its suitability for various engineering and industrial applications. The experimental procedures include thermal shock resistance, thermal conductivity, shrinkage, apparent porosity, refractoriness under load with rising temperature mode, and refractoriness under loadmaintained temperature mode. The results obtained from the research work showed the clay has good refractory properties that can be used for both Engineering and industrial applications. The value obtained through the thermal conductivity test 0.48W/m℃ , as compared with 0.35- 0.45 W/moC for insulating fire brick and 1.05- 1.45W/m℃ for dense fire brick. 2kg/cm2 of the sample was further subjected to refractoriness test where the sample was heated to 1405oC as compared to 1750oC for the production of fire bricks. Further investigation indicated that a glassy surface structure was formed when the samples was heated above 1400℃ . The value obtained as regard the porosity level was 25% which fell between 20-30% as the acceptable standard. The sample was also subjected to apparent porosity and a value of 38% was obtained. Kankara clay formed a glassy and surfaces when heated above 1400oC. In this research, these bricks porous with an apparent porosity of 38.07%. Attempts to produce these bricks with acceptable porosity level of 20-30% were not successful. Kankara clay exhibits moderate thermal shock resistance, moderate thermal conductivity, moderate shrinkage, high apparent porosity, and high refractoriness under load in both rising temperature mode and maintained temperature mode. "Based on these results, Kankara clay appears to be well-suited for use in applications where moderate levels of thermal shock resistance, thermal conductivity, and shrinkage are acceptable, such as in the manufacture of low-temperature bricks, but less suited for high-temperature applications, such as furnace linings, due to its high apparent porosity and susceptibility to deformation under load. Further research could be conducted to explore strategies for reducing the porosity and improving the refractoriness of this clay for broader applications.

Novel modular PCM wall board for building heating energy efficiency: Material preparation, manufacture and dynamic thermal testing

With the comprehensive implementation of China’s “dual carbon” goals, the building heating sector, characterized by high energy consumption and emissions, urgently requires low-carbon transformation. However, energy-saving measures for plateau regions are scarce and face challenges due to harsh climates. This study proposes an innovative heating method utilizing composite phase change materials. A new modular phase change thermal storage electric heating terminal integrated with a photovoltaic thermal system has been designed to address issues of high building energy consumption and problems related to heating system freezing and leakage in the Tibetan Plateau (Qinghai-Xizang Plateau). Laboratory tests were conducted on six groups of samples with different structures and placements to examine their heat storage and release characteristics. Results indicate: The system’s temperature stabilization time totals 14.6 h; Horizontally placing the terminal reduces melting time by up to 2.7 h, enhancing heat storage performance; Structure three shortens solidification time by up to 2.2 h compared to structure one, improving heat release performance; Vertically placed terminals have better heat release performance than horizontally placed ones, resulting in more effective indoor heating. This study proposes a modular design for phase change heat storage electric heating walls, simplifying installation and maintenance while maintaining aesthetic appeal. Detailed temperature measurements of different wall surfaces revealed excellent cyclic heat storage and release performance. The developed phase change heat storage electric heating terminal is expected to significantly reduce heating energy consumption in the Tibetan Plateau (Qinghai-Xizang Plateau), enhancing building energy efficiency and providing valuable insights for further applications of phase change materials in building design.

Measurement method of vacuum degree in satellite in vacuum thermal test of spacecraft based on diaphragm gauge

Measurement method of vacuum degree in satellite in vacuum thermal test of spacecraft based on diaphragm gauge

Comparison of carbon‐reinforced composites manufactured by vacuum assisted resin infusion with traditional and fully recyclable epoxy resins

AbstractThis study presents a comparative analysis of carbon fiber reinforced polymer (CFRP) composites manufactured through vacuum assisted resin infusion (VARI) using a traditional epoxy resin (E), a fully‐recyclable epoxy resin system with (BBR10) and without (BBR) the addition of a reactive diluent (R*Diluent). Various mechanical and thermal tests were conducted to assess their performance. The BBR10 laminate, incorporating 10 wt% R*Diluent, exhibited competitive mechanical performance, comparable to traditional (E) and fully‐recyclable laminates (BBR). Despite a slightly lower ultimate tensile strength (UTS) compared with BBR, BBR10 demonstrated improved flexural strength and modulus. Low‐velocity impact testing confirmed comparable strength between VARI‐produced composites with the recyclable matrix (BBR and BBR10) and the traditional one (E). X‐ray mCT investigations revealed distinct void arrangements in the CFRP laminates. Additionally, a chemical approach was employed for recovering high fractions of fibers from CFRP laminates with a recyclable matrix (BBR and BBR10). Chemical recycling achieved an almost 100% yield for long carbon fibers.Highlights Comparative analysis of CFRP composites manufactured through VARI. Diluent addition allowed to tailor the recyclable epoxy viscosity. Mechanical characterization of traditional and fully recyclable epoxy resins. Investigation by X‐ray mCT of potential flaws and manufacturing defects. Chemical recycling of CFRP laminates with a recyclable matrix.

Fabrication of the Cu/AgCuTi/Nb composite for superconducting radio-frequency material under extreme service conditions based on electroplating additive manufacturing

The primary objective of this study is the development of Cu/Nb composite materials for Superconducting Radio-Frequency (SRF) applications under extreme service conditions characterized by a strong RF electromagnetic field, extremely low temperatures, and relatively low heat loss. A novel integrated manufacturing approach is proposed, which combines cold-sprayed AgCuTi alloy as an intermediate coating on the Nb surface and an electroplated Cu layer with a subsequent heat treatment brazing effect. This strategy aims to address the significant challenge of non-intermelting Cu and Nb while also considering effective lateral heat transfer. Mechanical property tests showed that the bond strength of Nb/AgCuTi/Cu composites exceeded 150 MPa. Low-temperature thermal transport tests indicate that the Residual Resistance Ratio (RRR) of the Cu layer surpasses 150, with a thermal conductivity at 4.2 K exceeding 1600 W/(m·K). Moreover, both the composite interface and mechanical properties of the specimens remain stable even after undergoing cyclic cold shock experiments. These findings suggest that the Nb/AgCuTi/Cu composite material developed in this study meets the technical requirements for long-term stable and high-performance operation in high-current and high-power superconducting accelerators.

Analysis of warpage and reliability of very thin profile fine pitch ball grid array

With the evolution of advanced integrated circuit (IC) packaging technology, the use of experiments to identify package performance and life expectation will take a significant amount of time and cost to finish the job. To reduce the cost of research and testing, predictive analyses of reliability and performance using simulation tools have become a feasible approach for the IC assembly industry. Therefore, this study utilized Moldex3D molding simulation software to analyze very thin profile fine pitch ball grid array (VFBGA) packages and established a numerical analysis procedure from the molding and curing process, the post-mold cure (PMC) process, to a thermal cycling test (TCT) to predict the amount of package warpage during processing and reliability after TCT.The results showed that the warpage trends of both experiments and simulations during the same temperature ramping process were similar. In the thermal cycling analysis, potential failure locations were found to be at the copper pillars and redistribution layer (RDL), where the maximum Von Mises stress occurred at the lowest temperature (−65 °C). The fatigue life model, Coffin–Manson model, was used to calculate the potential fatigue life at the two locations, resulting in 1689 cycles (copper pillars) and 9706 cycles (RDL L1).

Investigation of constitutive models and microstructure evolution during hot deformation and solution treatment of Al–Zn–Mg–Cu alloy

In this paper, isothermal thermal compression tests were carried out on Al–Zn–Mg–Cu alloys at varying deformation temperatures (360°C∼440°C) and strain rates (0.001s−1∼10s−1) using a Gleeble-3500C thermal simulation tester. Based on the true strain stress data obtained from the tests, the flow behavior of Al–Zn–Mg–Cu alloys during thermal deformation was investigated. Through a comprehensive consideration of deformation temperature, strain rate, and strain compensation, a high-precision constitutive model was established. Additionally, the specimens subjected to hot compression were further treated with solution annealing for different durations (0 h–2 h) to investigate the static recrystallization (SRX) behavior and the associated microstructural evolution of the alloy during the solution treatment process. Electron Backscatter Diffraction (EBSD) was employed to characterize the microstructure evolution of Al–Zn–Mg–Cu alloy under various deformation and solution treatment conditions. The EBSD data were further processed and analyzed using the MTEX toolbox. The results revealed that dynamic recovery (DRV) is the predominant softening mechanism during the deformation process, accompanied by a small amount of dynamic recrystallization (DRX). The dynamically recrystallized grains exhibit a random crystallographic orientation. Further investigation showed that low temperature and high strain rate conditions are unfavorable for the occurrence of dynamic recovery and dynamic recrystallization during the thermomechanical processing. However, dislocations accumulated during deformation provided sufficient stored energy for the growth of static recrystallized grains during subsequent solution treatment, with static recrystallized grains predominantly forming at grain boundaries.

Enhancement of Thermo-Physical Properties of Form-Stable Nano-Enhanced Phase Change Materials: Advancing Maritime Sustainability

This paper explores the application of novel, form-stable eutectic mixtures in thermal energy storage systems for maritime environments. These advanced materials present a significant leap forward, addressing critical challenges faced by conventional phase change materials (PCMs) in marine environments. The stability, eliminating leakage and fluidity issues encountered with liquid PCMs are ensured by incorporating 2-hydroxypropyl ether cellulose (HPEC) as a gelling agent. Additionally, the thermal properties and heat transfer capacities were significantly enhanced, and eventually, overall system efficiency improved by including nano-graphene platelets (NGPs). Notably, NGPs effectively suppress supercooling, minimizing energy losses and guaranteeing consistent performance at elevated temperatures. Further, the eutectic mixture demonstrates exceptional durability through an accelerated thermal reliability test, guaranteeing optimal performance over a projected seventy-year lifespan. This enhanced thermal performance, and enduring stability combination establishes the form-stable eutectic mixture with NGPs as an up-and-coming solution for diverse maritime applications requiring efficient and reliable thermal energy storage. This research provides a compelling case for implementing form-stable eutectic mixtures with NGPs in maritime thermal energy storage systems. Its superior performance and sustainability offer significant advantages for diverse shipboard and offshore applications, contributing to improved energy efficiency, environmental sustainability, and operational resilience within the maritime sector.

Study on the Effects of Pasture Fiber on Thermal Properties of Slag Bricks.

In the context of ecological sustainability, this study focuses on the effect of variables of pasture fibers on the thermal properties of slag bricks made from a green recyclable material. This experiment uses slag as the binder, sand as the aggregate, and pasture fiber as an additive. The experimental variables include the additive content ratio of the pasture fiber, the size of the pasture fiber, and the type of pasture fiber. Significance analysis of the experimental results of the thermal performance tests is carried out using Minitab 18.1.0 software, and the optimal ratios for the thermal performance of the composite samples are derived from the response optimizer and conformity analysis. The results of the experiment's test analysis using Minitab 18 software indicate that, with an increase in pasture fiber content, the thermal performance of the composite samples initially decreases before increasing. Additionally, the lower the thermal conductivity of the composite sample, the lower the apparent density and the higher the porosity. Incorporating pasture fibers into slag bricks, as revealed in this study, reduces the waste of pasture resources in pastoral areas and promotes the development of sustainable building materials with favorable thermal properties.

Numerical study and experimental validation of heat transfer capacity of flat-type divertor for fusion reactor

The divertor must simultaneously withstand unprecedented high heat fluxes of up to 20 MW/m2 and high-energy neutron irradiation of 14-MeV during fusion reactor operation. Accordingly, it is necessary to simultaneously meet the excellent heat dissipation capacity of the divertor and maintain good material performance in harsh neutron irradiation environments. The flat-type divertor demonstrates better heat transfer performance compared to monoblock divertor. Nevertheless, under the condition of a heat flux of 20 MW/m2, the heat transfer and thermal fatigue performance of flat-type divertor using advanced materials are still unidentified. In this study, we conducted a thorough analysis of the heat transfer capabilities and thermal fatigue characteristics of potassium-doped tungsten (KW)/Cu/Oxide dispersion strengthened copper (ODS-Cu)/reduced activation ferritic/martensitic (RAFM) divertor mockup adopts hypervaportron (HV) structure by numerical simulations combined with experiments. The numerical results indicate that the flat-type KW/Cu/ODS-Cu/RAFM divertor mockup expresses excellent heat transfer capacity. The contact area between the edge of the fins and the bottom surface of the ODS-Cu heat sink induces a significant increase in water flow velocity to ∼15 m/s. The peak temperature of loaded KW surface is only ∼985 °C under the flow rate of 5 t/h and inlet temperature of 20 °C. During the high heat flux tests, the prepared flat-type divertor mockup successful endured 1000 cycles of 20 MW/m2 with the peak temperature of 883 °C, and the surface temperature experienced a fluctuation of 2.4 % during the thermal fatigue tests. This study can provide a strong data reference and technical support for the development of fusion reactors, and is of great significance in advancing the commercialization of fusion energy.

Numerical assessment of thermal insulation and stress responses in film-cooled turbine vane thermal barrier coatings under CMAS deposition conditions

Deposition of CaO-MgO-Al2O3-SiO2 (CMAS) significantly contributes to the spalling of thermal barrier coatings (TBCs) on turbine vanes. A thorough understanding of the thermodynamic properties during CMAS deposition is critical for advancing the lifetime design of TBCs. This study employs the CMAS gas thermal shock test to determine the deposition characteristics, which were then analyzed using the critical velocity model. The results of this analysis align closely with experimental outcomes. Based on the numerical simulation of the fluid-solid coupling method, we further explored the insulation efficiency and stress distribution in TBCs under CMAS deposition conditions. It was observed that CMAS predominantly accumulates on the pressure side and within the film pores of the vane TBCs, with minimal deposition on the suction side. Such deposition patterns result in an increased overall temperature of the vane, concurrently diminishing the TBCs' insulation efficiency. Specifically, CMAS deposition raised the maximum surface temperature of the vane by 100 K and decreased the peak insulation performance of the TBCs by 16 %. Additionally, the deposition induced higher stresses within both the TBCs and the underlying vane substrate, with a 7 % increase in the maximum principal stresses at the TBC surface and a 6 % increase in the substrate. Consequently, under CMAS deposition conditions, TBCs in regions of low insulation efficiency and high stress on turbine vanes are prone to cracking and subsequent spallation.

Development and thermal performance testing of radiant conditioning ceiling panels

The past decades have seen an advancement from heavyweight radiant floors to lightweight conditioning ceiling systems. However, the performance of these lightweight systems are seldom comprehensively discussed in an informative manner for designers. This paper reviews lightweight radiant ceiling panel designs and conducts instrumental experiments to examine the thermal performance of different designs. Four distinct capillary hydronic panels have been designed and developed to assesses their thermal performance via empirical testing and measurement. Prototypes were built and integrated into a suspended ceiling system where they were tested in cooling mode. The response time, surface temperature, and energy transfer of the different panel designs were investigated. The experiment results show that higher thermal mass yields higher heat transfer and better surface temperature, but longer response time. A better thermal connection between the capillary tubes and the radiant surface also results in better conduction, faster response times, and improved surface temperature.

A multi-parameter estimation of layered rock-soil thermal properties of borehole heat exchanger in a stratified subsurface

The high initial investment of borehole heat exchanger (BHE) prevents the popularization and application of ground-coupled heat pump system (GCHPs). As the premise of designing BHE, ground thermal properties are usually obtained using thermal response test (TRT), and parameter estimation method are applied based on homogeneous BHE model independent of geological stratification. In this paper, a multi-parameter estimation method using Bat algorithm (BA) is firstly proposed to obtain the layered rock-soil thermal properties based on the numerical layered BHE model, considering the characteristics of geological stratification. Then, a TRT experimental platform of three-layer BHE is developed to measure thermal responses of different stratified subsurface. Finally, the six thermal properties are obtained by the proposed multi-parameter estimation method based on BA, and their accuracy is validated using the experimental data in TRT. The five temperatures obtained from the numerical layered BHE model using the estimated results are compared with the corresponding experimental data, the results show that the maximum error of the inlet and outlet water temperatures of the BHE is respectively 3.32 % and 3.59 %, and it is 3.31 %, 2.38 % and 2.7 % for the coarse sand, fine sand and brown soil, respectively.