Transient Hot-wire Method Research Articles

Experimental investigation on thermal conductivity and thermal degredation of Honge oil methyl ester with B-20 blend.

Honge oil methyl ester (HOME) with B-20 blend is considered to examine thermal con- ductivity and thermal degredation of the biodiesel. Transient hot wire method is adopted to determine thermal conductivity of the samples.Heat source is clubbed with C-DAQ and LAB-VIEW software is utilized to record temperature and time. Following Sastry’s power law model, an improved emperical relation is developed for thermal conductivity of HOME with B-20 blend. Thermogravitometry (TG-DTG) analysis is performed under atmospheric condi- tions with 10°C/min heating rate of pure air flow.Diesel is exhibited one mass loss event from 55–334°C, whereas two mass loss event in case of biodiesel. Maximum decoposition tem- perature noticed for diesel,HOME andB-20 blend are 195°C, 227°C and 175°C respectively. Complete mass degradation takes place for diesel and HOME at 498°C, in case of HOME with B-20 blend complete mass degradation occurred at 377°C.

Development of measurement setup for thermal conductivity at high temperatures using the parallel hot-wire

An experimental setup is built to determine the thermal conductivity of a mixture of KNO3 and NaNO3 with a ratio of 54-46m% which is used in high temperature thermal storage systems. The measurement principle is based on the transient parallel hot-wire method which is described in the standards NBN B 62-202 and ISO 8892-2. The setup is designed to measure the thermal conductivity around the melting temperature (<300°C). Measurements within the liquid region show faulty results caused by natural convection within the sample. The measured thermal conductivity within the solid region is 0.5466-0.5529W/mK close to the melting point and 0.7174W/mK at room temperature, which shows a decreasing thermal conductivity with increasing temperature in the solid region.

Thermophysical, rheological and electrical properties of mono and hybrid TiB2/B4C nanofluids based on a propylene glycol:water mixture

Hybrid nanofluids aim to further improve the characteristics of mono nanofluids. However, experimental studies that jointly explore the physical properties of hybrids and the corresponding mono nanofluids are missing. In this work, mono B4C and TiB2 and hybrid TiB2:B4C nanoadditives are used for the first time to design nanofluids based on propylene glycol:water 20:80 wt%. The density, isobaric heat capacity, and thermal conductivity of the nanofluids are determined by the oscillating U-tube, differential scanning calorimetry, and transient hot wire methods, respectively. The rheological behaviour is investigated through rotational rheometry. Additionally, surface tension and electrical conductivity are investigated. The B4C mono nanofluid shows the highest improvements of thermal conductivity (6.0%) and electrical conductivity (70 times higher), but also the highest viscosity increases (51–54%). The hybrid nanofluid presents intermediate values between those of the mono nanofluids for all the properties except dynamic viscosity. Interactions between spherical and sheet-like nanoparticles explain this behaviour.

Ultra-High Temperature Thermal Conductivity Measurements of a Reactive Magnesium Manganese Oxide Porous Bed Using a Transient Hot Wire Method

Abstract Pelletized magnesium manganese oxide shows promise for high temperature thermochemical energy storage. It can be thermally reduced in the temperature range between 1250 °C and 1500 °C and re-oxidized with air at typical gas-turbine inlet pressures (1–25 bar) in the temperature range between 600 °C and 1500 °C. The combined thermal and chemical volumetric energy density is approximately 2300 MJ/m3. The rate at which a thermochemical storage module can be charged is limited by heat transfer inside the solid packed bed. Hence, the effective thermal conductivity of packed beds of magnesium-manganese oxide pellets is a crucial parameter for engineering Mg-Mn-O redox storage devices. We have measured the effective thermal conductivity of a packed bed of 3.66 ± 0.516 mm sized magnesium manganese oxide (Mn to Mg molar ratio of 1:1) pellets in the temperature range of 300–1400 °C. Since the material is electrically conductive at temperatures above 600 °C, the sheathed transient hot wire method is used for measurements. Raw data is analyzed using the Blackwell solution to extract the bed thermal conductivity. The effective thermal conductivity standard deviation is less than 10% for a minimum of three repeat measurements at each temperature. Experimental results show an increase in the effective thermal conductivity with temperature from 0.50 W/m °C around 300 °C to 1.81 W/m °C close to 1400 °C. We propose a dual porosity model to express the effective thermal conductivity as a function of temperature. This model also considers the effect of radiation within the bed, as this is the dominant heat transfer mode at high temperatures. The proposed model accounts for microscale pellet porosity, macroscale bed porosity, pellet size, solid thermal conductivity (phonon transport), and radiation (photon transport). The coefficient of determination between the proposed model and the experimental results is greater than 0.90.

Thermal conductivity measurement and correlation at saturation condition of HFO refrigerant trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(E))

• Thermal conductivity measurements of R1336mzz(E) are performed by the transient hot-wire method over a wide range of temperature and pressure. • The experimental thermal conductivity data are compared with other researchers. • Correlations at saturation conditions have developed with the experimental data by the extrapolation method. The trans-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(E)) would be a novel working fluid in the heat pumps and organic Rankine cycles with low-GWP value, lower toxicity, and non-flammability. The transport property mainly thermal conductivity measurement is the main target of the paper for this HFO refrigerant for the liquid, vapor, and supercritical states, respectively. Simple correlations at saturated state are developed to estimate the thermal conductivity for industrial design and simulation. In this article, the thermal conductivity data were reported in the temperature from 313 to 393 K over the pressure until 4.0 MPa and temperature from 313 to 453 K at pressure up to 2.5 MPa both for liquid and vapor states, respectively. Also, the thermal conductivity in a supercritical region was recorded from temperature range 413 to 453 K and pressures at 3.0 to 4.0 MPa. The experimental liquid and vapor thermal conductivity data of R1336mzz(E) were compared with the data measured for cis-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(Z)). Moreover, the correlations at the saturated state were developed by extrapolating the experimental data until the saturation conditions both for liquid and vapor states. The estimated combined uncertainties for the liquid, vapor and supercritical regions of thermal conductivity measurement were recorded to 1.94 %, 1.98 %, and 2.01 %, respectively.

Measurement and analysis of thermal conductivity of ceramic particle beds for solar thermal energy storage

A systematic study was performed to measure the effective thermal conductivity of ceramic particle beds, a promising heat transfer and thermal energy storage medium for concentrating solar power (CSP). The thermal conductivity of the ceramic particle beds was measured using a transient hot-wire (THW) method within a temperature range of room temperature to 700 °C, the target operating temperature of the next-generation CSP systems. Two different types of ceramic particles were examined: (1) CARBOBEAD HSP 40/70 and (2) CARBOBEAD CP 40/100 (also known as ACCUCAST ID 50) with the average particle sizes of ~405 μm and ~275 μm, respectively, and thermal conductivities ranging from ~0.25 W m −1 K −1 to ~0.50 W m −1 K −1 from 20 °C to 700 °C in both air and N 2 gas. The gaseous pressure dependence of the thermal conductivity of the ceramic particle beds was also studied in the N 2 environment to differentiate the contributions from gas conduction, solid conduction, and radiation. Calculations using the Zehner, Bauer, and Schlünder (ZBS) model showed good agreements with the measurements. Based on the model, it is concluded that the effective thermal conductivity of the packed particle beds is dominated by the gas conduction while the solid conduction and radiation contributes to about 20% of the effective thermal conductivity at high temperature. • First thermal conductivity measurement of CARBOBEAD HSP 40/70 and CP 40/100 up to 700 °C. • Analysis of thermal conductivity from temperature and gaseous pressure dependence. • Quantification of relative contributions from gas, solid contacts, and radiation at various temperature. • Gaseous conduction is found to be the dominant mechanism.

High pressure thermal conductivity of three ethyl esters in the liquid phase

Recently, biodiesel is considered as a biodegradable, renewable and high-potential fuel which could be used directly in tradition internal combustion engines. Fuel’ transport properties in high pressure are required to model the process of fuel spray, atomization and combustion accurately. This work, three ethyl esters’ liquid thermal conductivity (biodiesel compounds) in the liquid phase was measured by an experiment system which is established based on a transient hot-wire method with a bare platinum hot wire. The measurements were conducted at the temperatures ranging from 292 K to 372 K and pressure up to 15 MPa. The combined expanded uncertainty of the measurement was estimated to be ±2.0% (in the 0.95 confidence level). For interpolation, the relationship between measured results with temperature and pressure were correlated as a polynomial function, and the maximum deviation of correlations were less than 0.30%.

Thermal conductivity measurements for long-chain n-alkanes at evaluated temperature and pressure: n-dodecane and n-tetradecane

With the key role of long-chain hydrocarbons in the wide applications in numerous industrial areas, such as working fluids, phase change materials, fuels, etc., the knowledge of the thermal conductivity of hydrocarbons is essential in the energy conversion process. Thus, it is of great significance to get reliable experimental data of hydrocarbons’ thermal conductivity for further accurately theoretical predictions and the potential applications. In this work, the thermal conductivities of two long-chain hydrocarbons of n-dodecane and n-tetradecane, are investigated experimentally. The transient hot-wire method was used for the measurement of the thermal conductivity under the conditions of 293–523 K and 0.1–15.0 MPa. By comparing the present work with literature results, the possible reasons for the deviations were analyzed. The results in this study provide accurately measured of the thermal conductivity of the two long-chain hydrocarbons at high temperature and pressure, which are expected to fill the gap in literature.

Investigating thermo-physical properties and thermal performance of Al2O3 and CuO nanoparticles in Water and Ethylene Glycol based fluids

The thermophysical properties and thermal performance of water- and ethylene-glycol-based nanofluids containing and CuO nanoparticles were examined. Nanofluids were prepared at four concentrations (1- 4 vol%) using an electric mixer and magnetic stirrer, and the thermophysical properties were measured. Surfactants were used to improve stability. The transient hot-wire method (KD2-Pro device), Dynamic Light Scattering (DLS), and Ostwald viscometer (ASTM D445-06) were used to measure the resulting thermal conductivity coefficient, nanoparticle diameter, and nanofluid viscosity, respectively. The experiments were carried out in the 20 to 50 °C temperature range. Adding 1 wt% sodium dodecyl sulfate (SDS) to the CuO–water and the same amount of sodium dodecylbenzene sulfonate (SDBS) to the –water nanofluid were found to stabilize them for 20 and 22 days, respectively. Increasing the nanoparticle volume fraction, raising the temperature, and reducing nanoparticle diameter were found to increase the thermal conductivity coefficient. The density also increases with the nanoparticle volume fraction in the base fluid increasing. Moreover, at the same volume fraction, the CuO–water nanofluid had a higher density than –water. Better base fluid thermal properties amplify the effect on the nanofluid's thermal conductivity coefficient. The actual thermal conductivity coefficient was determined by comparing model predictions of the coefficient.

Measurements on the thermal conductivity of three fuel blends containing a biodiesel compound methyl laurate + diesel compounds: n-Undecane, n-dodecane, n-tridecane

Recently, biodiesel has received tremendous attention from a lot of scientists as a biodegradable, renewable and high-potential fuel which could be used directly or blended with diesel in internal combustion engines. The adequate thermophysics properties of fuel are required to model the process of fuel spray, atomization and combustion accurately. In this work, three fuel blends containing methyl laurate and n-undecane, n-dodecane, n-tridecane were prepared and an important transport property—liquid thermal conductivity of which were measured by the transient hot wire method system. The measurement was conducted at temperature ranging from 292 K to 362 K at atmospheric pressure with the mass fraction of methyl laurate being nearly 0.2000, 0.4000, 0.6000 and 0.8000 (by weight) in the binary mixtures. Furthermore, the relationship between the experimental results and temperature and concentration of methyl laurate were correlated as a function. The uncertainty of the experimental system is less than ±2.0%.

Multicomponent bio-based fatty acids system as phase change material for low temperature energy storage

In this study, new multicomponent mixtures of fatty acids for low temperature thermal energy storage applications have been developed. The new mixtures were based on coconut oil fatty acids (CoFA) and commercial grades of oleic (OA) and linoleic acid (LA). Refined coconut oil (CO) was first converted into free fatty acids by alkaline saponification. The prepared CoFA were then mixed with OA or LA at various compositions to prepare stable bio-based phase change materials (BPCMs). The thermal behavior including melting/solidification temperatures, specific heat and enthalpy of the developed mixtures were investigated by means of differential scanning calorimetry (DSC) and T-history. Transient hot wire method was used to measure thermal conductivity of the PCMs. The chemical stability and thermal reliability of the mixtures were assessed stepwise from 100 to 700 melt/freeze cycles by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and DSC. Based on DSC and T-history results, the phase transition of the developed PCMs were in line with the range of human comfort temperatures i.e. 18-25 °C, with no incongruent melting and less than 0.6 °C super cooling, whereas specific heat and enthalpy of the new mixtures were in the range of 1-5 J/g K, and 40-100 J/g. The FTIR and DSC results indicated that the PCMs mixtures are chemically and thermally stable. The thermal conductivity of the mixtures were in average 0.2 W/m K, in liquid phase and 0.35 W/m K, in solid phase. Out of the different developed combinations, the mixture of LA/CoFA (20/80) showed distinguished performance and can be considered as potential BPCM for low temperature thermal energy storage applications.

Measurements of the Thermal Conductivity of l-Menthol–Decanoic Acid Deep Eutectic Solvents in the Temperature Range from 283.15 to 363.15 K at Pressures up to 15.1 MPa

In this work, the thermal conductivities of l-menthol–decanoic acid (Men–DecA) deep eutectic solvents were measured with different mole compositions using a transient hot-wire method. The measured ...

Effect of hydrate distribution on effective thermal conductivity changes during hydrate formation in hydrate-bearing quartz sands

The effect of hydrate distribution on the effective thermal conductivity changes of the actual hydrate-bearing sediments is uncertain. To define this effect, in the hydrate-bearing quartz sands, the effective thermal conductivity was measured by the transient hot-wire method, and hydrate distribution was analyzed by the electrical resistance changes. At first, the effective thermal conductivity changes were investigated from gas saturation, gas pressure, water saturation, water pressure, and temperature. Afterward, in three kinds of hydrate formation processes, compared with hydrate distribution, the changing trends of the effective thermal conductivity at five measuring points were analyzed. The results showed that the effective thermal conductivity was increased with decreasing gas saturation and increasing water saturation or water pressure, and impacted slightly by gas pressure and temperature. Moreover, at five measuring points, the non-uniform hydrate distribution caused different changing trends of the effective thermal conductivity during hydrate formation. In the excess-water setting, an increasing trend was only observed at some local measuring point. The decreasing trends at the most of the measuring points were governed by the reduced water distribution. But in the excess-gas setting, at the most of the measuring points, this increasing trend was observed and controlled by the enlarged hydrate distribution. Besides, for some actual sediments in the excess-water setting, hydrate distribution may be not the key factor of the effective thermal conductivity changes, and further studies were required. This research could offer some valuable reference to the thermal properties in the actual sediments.

Measurement and modeling of thermal conductivity for short chain methyl esters: Methyl butyrate and methyl caproate

Fatty acid methyl esters (FAMEs) are the main component of biodiesels. Before the industrial application of FAMEs, it is essential to investigate the thermophysical properties of FAMEs. Thermal conductivity of fuels is used in various processes, such as the design of the heat transfer system and the determination of the temperature distribution of engines. Thus, it is of great significance to acquire accurate experimental data and develop reliable models for obtaining accurate thermal conductivity data of FAMEs. In this work, thermal conductivities of two short-chain FAMEs, methyl butyrate (MeC4:0) and methyl caproate (MeC6:0) were studied experimentally and theoretically. The thermal conductivities of these two FAMEs were measured by the transient hot-wire method at T = 303 to 523 K and p = 0.1 MPa to 15 MPa, the data were correlated as a polynomial function of temperature and pressure, the AADs are 0.38% for MeC4:0 and 0.42% for MeC6:0, respectively. Moreover, the experimental thermal conductivities agree well with the available data from literature. In addition, three classical models (Latini model, Sastri model, Liu model) were used to represent the present experimental data and the results show that Liu model with re-fitted parameters performs better in the prediction of the thermal conductivity of FAMEs, with regard to accuracy.

Experimental Study on the Enhanced Thermal Performance of Two-Phase Closed Thermosyphon Using Mechanical and Chemical Treated MWCNTs Nanofluids

Nowadays the two-phase closed thermosyphon (TPCT) has been widely used as an important heat transfer medium for passive cooling systems. Since the enhancement of the performance of electronic device releases a considerable amount of heat, the development of working fluids which can improve thermal performance of the TPCT is necessary. In this experiment, two different type of MWCNT nanofluids were successfully made by using ball-mill process and alkaline treatment. The morphological and structural analysis were conducted by using transmission electron microscope (TEM), fourier-transform infrared spectroscopy (FT-IR). Also thermal conductivity of modified MWCNT nanofluids were investigated by introducing transient hot wire method. The results of TEM, FT-IR and thermal conductivity showed that the MWCNTs were successfully functionalized as well as had higher thermal conductivity. The TPCT was fabricated with copper tube and total length of the TPCT is 700mm, in which the evaporator section, the adiabatic section and the condenser section are 150mm, 400mm, and 150mm, respectively. The experiment of the thermal performance of the TPCT was evaluated by introducing RMS value of the temperature of the evaporation section, thermal resistance and heat transfer coefficient at five different filling ratios, 10%, 30%, 50% and 70% by ratcheting up heat loads in five levels, 5W, 8W, 10W, 13W and 15W. The overall results showed that the both of modified MWCNT nanofluids can decrease thermal resistance and increase the heat transfer coefficient, especially at 10% filling ratio with 8W. M-CNT nanofluid can even enhance the thermal performance of TPCT at 30% filling ratio with all heat loads.

Thermal Conductivity of 1,2-Ethanediol and 1,2-Propanediol Binary Aqueous Solutions at Temperature from 253 K to 373 K

1,2-Ethanediol, 1,2-propanediol and their aqueous solutions are widely used as heat transfer fluids. Their thermal conductivity is a vital physical property, yet there are only few reports in literature. In this paper, thermal conductivity of binary aqueous solutions of the two glycols was measured using the transient hot wire method at temperature from 253.15 K to 373.15 K at atmospheric pressure. Measurement was made for six compositions over the entire concentration range from 0 to 1 mole fraction of glycol, namely, 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 mole fraction of glycol. The uncertainties of temperature and concentration measurement were estimated to be 0.01 K and 0.1 %, respectively. The combined expanded uncertainty of thermal conductivity with a level of confidence of 0.95 (k = 2) was 2 %. The second-order Scheff\'e polynomial was used to correlate the temperature and composition dependence of the experimental thermal conductivity, which was found to be in good agreement with the experiment data from the present work and other reports.

Evaluation of Korean recycled aggregates as backfilling underground power system considering particle breakage effect

Attempts have been made to address the strict regulations on eco-friendly construction and recycle aggregate resources, encouraging researchers to consider the utilization of recycled aggregates for the backfilling of underground power systems. It is essential to recognize the physical and thermal characteristics of domestic recycled aggregates for use as backfill materials for underground power conduits in Korea. Herein, the thermal properties of concrete-based recycled aggregates with different grain-size distributions are evaluated, and the particle breakage effect of recycled aggregates is identified through the compaction tests. The thermal properties of the recycled aggregates and the river sand were measured using a transient hot wire method after a standard compaction test. The particle breakage effect was also investigated during the standard compaction test. The thermal resistivities of the recycled aggregates and the river sand showed a similar trend, which were decreased with an increase in the water content at the same dry unit weight. In addition, particle breakage during compaction led to an enhanced compaction effect, reducing the thermal resistivity and increasing the fine particle content. This study shows that the recycled aggregates can be promising backfill materials that substitute natural aggregates when backfilling underground power conduits.

Experimental research on the liquid thermal conductivity of mixtures of methyl caprate and ethyl caprate with n-undecane and n-tridecane

Globally, biofuel is considered as the largest renewable energy source to substitute the petrochemical fuel and it is thus received a great amount of attention from both developed countries and developing countries. Among all the biofuels, biodiesel is strongly recommended as a promising alternative fuel for traditional internal combustion engines. Thermal conductivity is an essential transport property of fuel, and is vital in the flow and heat transfer process. Therefore, it is necessary to conduct the research associated with fuel’s thermal conductivity. In this work, four binary fuel mixtures containing biodiesel components methyl caprate and ethyl caprate with n-undecane and n-tridecane were prepared respectively, and the liquid thermal conductivity of which were measured by the transient hot wire method system. The measurement was conducted at the temperature from 292 K to 362 K at atmospheric pressure. The experimental data reported here have an uncertainty of less than 2%. In addition, a correlation about the relationship between the liquid thermal conductivity with temperature and the esters’ concentration in different fuel blends has been correlated.

Experimental study of the anisotropic thermal conductivity of 2D carbon-fiber/epoxy woven composites

The anisotropic micro-structure of fiber will lead to the macroscopic anisotropic properties of fiber reinforced composites in both heat transfer and mechanical strength. However, few experimental studies have be made on the anisotropic heat transfer properties of fiber reinforced composites. In this study, the anisotropic thermal conductivities of two-dimensional (2D) plain woven and twill woven carbon-fiber/epoxy composites are measured at different temperature with the one-dimensional (1D) steady-state method, transient plane source (TPS) method and transient hot wire method, respectively. The out-of-plane thermal conductivity and in-plane thermal conductivity at the temperature ranging from −45 °C to 160 °C are obtained and comparisons are made among the three methods. The results show that all the three methods can be used to measure the anisotropic thermal conductivity of fiber/epoxy woven composites. Both the out-of-plane thermal conductivity and in-plane thermal conductivity of carbon-fiber/epoxy woven composites increase with temperature, and the in-plane thermal conductivity is approximately four times as high as the out-of-plane thermal conductivity for the plain woven composites. Compared with the results of 1D steady-state method, the max deviations of TPS method and hot wire method are 18.1% and 17.1%, respectively. The sources of error that leading to the deviations are also discussed.

Influence of the Hydric State and Lime Treatment on the Thermal Conductivity of a Calcareous Tufa

An experimental study was conducted to investigate changes of thermal conductivity of a raw and lime-treated calcareous tufa (north-west of Algeria) during drying process. Treated (with 4% of lime) and untreated samples were prepared by static compaction at the Standard Proctor Optimum (SPO), Modified Proctor Optimum (MPO) and at a constant stress level of 4 MPa. Transient Hot Wire (THW) method was used to measure the thermal conductivity and the water content and degree of saturation of samples were determined at various drying times. Results show that the drying process induces a decrease in thermal conductivity. This parameter seems to vary linearly with the water content and the degree of saturation. In addition, it was found that the lime treatment leads also to a decrease in the thermal conductivity. Thus, the drying process and the lime treatment will jointly contribute to the reduction of the thermal conductivity of the studied material in such a way that it is more insulating than some traditional building materials like concrete or fired bricks. Doi: 10.28991/cej-2021-03091663 Full Text: PDF