Experimental Study on the Thermal Performance of Rice Straw-Mortar Composite Materials

The effect of organic–inorganic interfaces on the thermal conductivity of composite materials was studied by evaluating thermal conductive resistance at the organic–inorganic interfaces experimentally. Polymer layers were sandwiched between thin ceramic plates to produce multilayer stacked samples. Through the comparison between the thermal conductivities of the multilayer stacked materials and those of single component materials for both polymers and ceramics, the thermal resistance at the interface between a polymer and a ceramic plate was evaluated. The results suggest that the contribution of thermal resistance becomes significant for actual composite materials because of the increase in the number of interfaces. The results also demonstrate that organic modifications of an inorganic surface could effectively reduce interfacial thermal resistance. The control of interfaces seems to be effective for improving the thermal conduction property of composite materials.

Soil profile method for soil thermal diffusivity, conductivity and heat flux: Comparison to soil heat flux plates

Constructal design of I-shaped high conductive pathway for cooling a heat-generating medium considering the thermal contact resistance

Study on thermal conductivity of cement with thermal conductive materials in geothermal well

In the application of hyperthermia to cancer management, it would be useful to know the temperature/tim profile of heated tissues, including the tumor and surrounding normal structures. To obtain this information, knowledge of thermal conductivity and diffusivity of the tissues is required. The thermal conductivity of neuroblastoma was determined by a transient technique to be 89% of the thermal conductivity of water at 25 degrees, 37 degrees, and 44 degrees C. From the latter measurements, the thermal diffusivity of neuroblastoma cells was estimated as 93% of the thermal diffusivity for water. Further, in this study of neuroblastoma cells, the water content was measured as 87.4 g/100 ml of cells, a rather high value not atypical of tumor cells. From literature values of density, specific heat, and thermal conductivity, values for the thermal diffusivity of a variety of normal tissues were estimated. The thermal diffusivity values of normal tissues and neuroblastoma cells exhibit an excellent correlation with water content.

In this work, in-plane and through-plane thermal diffusivities and conductivities of a freestanding sheet of graphene nanoplatelets are determined using photothermal beam deflection spectrometry. Two experimental methods were employed in order to observe the effect of load pressures on the thermal diffusivity and conductivity of the materials. The in-plane thermal diffusivity was determined by the use of a slope method supported by a new theoretical model, whereas the through-plane thermal diffusivity was determined by a frequency scan method in which the obtained data were processed with a specifically developed least-squares data processing algorithm. On the basis of the determined values, the in-plane and through-plane thermal conductivities and their dependences on the values of thermal diffusivity were found. The results show a significant difference in the character of thermal parameter dependence between the two methods. In the case of the in-plane configuration of the experimental setup, the thermal conductivity decreases with the increase in thermal diffusivity, whereas with the through-plane variant, the thermal conductivity increases with an increase in thermal diffusivity for the whole range of the loading pressure used. This behavior is due to the dependence of heat propagation on changes introduced in the graphene nano-platelets structure by compression.

Thermal rectification refers to the phenomenon that heat fluxes or equivalent thermal conductivities are different under the same temperature difference when temperature gradient directions are different. The nature of the thermal rectification is that the structure has different effective thermal conductivities in different directions. Most of previous studies focused on thermal rectification of temperature-dependent thermal conductivity materials or variable cross section area structure, and the effect of thermal contact resistance at the interface was investigated very rarely. In the present paper we present the analytical and finite element numerical solution of temperature field and thermal rectification ratios of a composite structure with variable cross section area and thermal conductivity under different interface thermal contact resistances. The prescribed temperature boundary condition is introduced by penalty method, and the temperature jump condition at the interface is implemented by the definition of thermal contact resistance directly. The nonlinear heat conduction problem caused by temperature-dependent thermal conductivity and interface thermal contact resistance is then solved with a direct iteration scheme. Comparisons between experimental results and the present theoretical and numerical results show the feasibility of the proposed model. Then parameter investigations are also conducted to reveal the effect of some key geometric and material parameters. Numerical results show that thermal contact resistance plays an important role in the temperature field and thermal rectification ratio of the two-segment thermal rectifier. With the increase of the length ratio, thermal ratification ratio increases first and decreases then, and the optimal length ratio varies with both thermal contact resistance and cross-section radius change rate of the two segments. In general, the existence of thermal contact resistance can increase the total thermal resistance of the rectifier and magnify the distinction of the heat flux in forward and reverse cases. However, if the thermal contact resistance is too large, this distinction will decrease and correspondingly the thermal rectification ratio becomes low. With the increase of the boundary temperature difference, thermal rectification ratio increases due to the effect of temperature-dependent thermal conductivity. In the present study, we propose a theoretical and numerical approach to designing and optimizing the length ratio, cross-section radius change rate, thermal conductivity, boundary temperature difference and interface thermal contact resistance to obtain the maximal thermal rectification ratio of a bi-segment thermal rectifier, as well as the manipulation of thermal flux in engineering applications.

Statement of the Problem.The search for energy-efficient solutions is relevant at the current construction and civil engineering development stage. One of the key parameters to be determined is the thermal conductivity of materials and products. This parameter depends on temperature and other factors, necessitating the need for fast and reliable methods to determine it for energy efficiency assessments or research purposes. One such method is using the modeling. This paper describes the formulation of modeling tasks and presents a computer model based on a real device for measuring thermal conductivity via the dynamic calorimetry method. The mathematical foundation of the model is based on Fourier’s law, thermal parameter dependencies documented in the device specifications, and data obtained from benchmark experiments. The model is implemented in the LabVIEW environment and has been tested through experiments in various operational modes. The results demonstrate a significant reduction in time required to obtain data compared to studies conducted using the physical device, highlighting the effectiveness of modeling for research purposes. The purpose of the article. To present the problem formulation and modeling results for studying the thermal conductivity of solid materials. Conclusion. The modeling tasks have been formulated, and a computer model has been developed to study the thermal conductivity of solid materials. The model simulates the processes occurring in a real thermal conductivity measurement device. Experimental studies on the actual instrument have been used to validate the model’s accuracy. The developed model can be utilized both for educational purposes and for obtaining data on the thermal conductivity and thermal insulation properties of various solid materials.

The proximate compositions, moisture (74.2%), protein (28.07%), ash (2.62%), lipid (3.39%), and carbohydrate (4.39%) of brackish water shrimp (Litopenaeus vannamei) were determined. The density, specific heat, thermal conductivity, thermal diffusivity, and latent heat obtained as functions of the proximate composition of the shrimp and found to be 1110 kg/m3, 394 kJ/kgK, 0.5113 W/mK, 1.1773 × 10−6 m2/s, and 256.39 kJ/kg, respectively. The thermophysical values obtained were correlated with the proximate composition value. Correlation analysis reveals that specific heat (0.83), thermal conductivity (perpendicular model) (0.99), and latent heat (0.12) have positive correlation with protein content of shrimp. On the contrary, thermal diffusivity (−0.92) and thermal conductivity (parallel model) (−0.99) have negative correlation with protein content of shrimp. Further, latent heat of shrimp has a weak positive correlation (0.12) with protein content of shrimp and strong positive correlation with carbohydrate (0.82), fat (0.94), and water (1.0). Thermal conductivity (perpendicular model) has weak positive correlation with fat (0.18) and water (0.19), and has strong positive correlation with protein (0.99) and ash (0.81). Shrimp density has strong correlation with protein (0.98) followed by ash (0.86). Heat may be transferred better across the fibers of the shrimp than along the fiber. Context: Shrimp is one of the most valuable sources of high-grade protein among the seafood category. Shrimp has healthy fat a unique source of essential nutrients, including long-chain omega-3 fatty acids, iodine, vitamin D, and calcium. The global shrimp production has increased at a compound annual growth rate (CAGR) of 3.2% during the period 2011 to 2017. High market demand and consumer preference for shrimp food are attributed due to the attractive and sleek appearance, substantial flesh, ease of preparation for processing (mainly due to absence of scales), etc. With the potential and promise of further increases in production, it is essential to provide a firm base for development of technologies suitable for the value-added products from shrimp to further enhance its market expansion. Understanding on thermal properties of foods plays an important role in the design and prediction of heat transfer operations during the handling, processing, canning, storing, and distribution of foods. In addition, they are fundamentally important in mathematical modeling studies for the design and optimization of food-processing operation involving heat and mass transfer. Aims: The aim of the present study is to determine some thermophysical properties of shrimp as a function of its proximate composition to provide data for the development of appropriate equipment and processing technology for brackish water shrimp (L. vannamei). Settings and design: Proximate composition of the brackish water shrimp (L. vannamei) was measured. Prediction equations were developed to predict the thermophysical properties of shrimp. Correlation matrix was prepared to understand the dependence of proximate composition and thermophysical properties of shrimp. Materials and methods: Shrimp (L. vannamei) were obtained from an aquaculture farm in Nagapattinam. Shrimp were handled in accordance with the Codex General Principles of Food Hygiene (CAC/RCP 1-1969) and Code of Practice for Fish and Fishery Products (CAC/RCP 52-2003). The Kjeldahl method was performed according to method 981.10 of the AOAC International. Total lipids in tissue sample were extracted and analyzed by the method. Water content was determined by oven drying at 105°C, and ashing by incineration in a muffle furnace at 525°C. Carbohydrate content was determined by difference method as given in the following equation: % Carbohydrate = 100–% (Crude protein + Total fat + Ash) × 100. Comprehensive models were used predict volume and thermal properties. Statistical analysis used: Correlation matrix of proximate composition and the thermophysical properties of shrimp were prepared to understand the dependence of thermophysical properties with the proximate composition of shrimp. Results: The predicted values of the thermophysical properties of farmed shrimp were in accordance with the already published values. The density of the shrimp is slightly higher side when compared with water alone, indicating the influence of proximate composition. Correlation matrix thus prepared, better explains dependence of thermophysical properties (specific heat, thermal conductivity, thermal diffusivity, latent heat, and density) with the proximate compositions (moisture, protein, ash, lipid, and carbohydrate) of brackish water shrimp (L. vannamei).Shrimp is “nature’s superfood,” an important source of proteins and healthy fat, and a unique source of essential nutrients, including long-chain omega-3 fatty acids, iodine, vitamin D, and calcium. The knowledge of its engineering properties is essential to its processing and preservation to increase its value as food. The thermophysical data obtained in this study could be used as input in heat transfer calculations and to establish critical control points during the drying, freezing, and thermal processing of shrimp meat.

The growing reliance on air conditioning and cooling devices due to extreme heat emphasizes the urgent need for sustainable and affordable eco-friendly insulation options. Sunlight exposure increases excessive heat, prompting the use of air conditioners, electric fans, and other cooling devices. Using a quantitative experimental method, data were gathered by measuring the thermal conductivity and thermal resistance of bio-composite material as an insulator in comparison to commercial insulators. The samples were tested using a FOX 200 Heat Flow Meter to measure thermal conductivity. Thermal resistance was calculated using the sample thickness and the conductivity value from the machine’s datasheet. Results showed that the first rambutan fiber with the binding agent had a thermal conductivity of 0.34046 W/mmK and thermal resistance of 0.06635667 m².K/W, while adding another binding agent slightly increased conductivity (0.38279 W/mmK) and reduced resistance (.07460667 m².K/W). Commercial insulation had significantly better performance, with a conductivity of 0.02740 W/mmK and resistance of 2.61793667 m².K/W. The findings confirm a significant difference in thermal conductivity between the experimental and commercial setups, indicating varying insulation capacities. The study highlights the potential of rambutan peels as an alternative insulation material, though its thermal performance is significantly lower than commercial insulation. The higher thermal conductivity and lower thermal resistance of rambutan fiber indicate it is less effective at preventing heat transfer.

In this study, nanofluids were prepared using Graphene nano-sheets with two concentrations 0.002% and 0.004%. Thermal conductivity was studied to investigate thermal properties for nanofluid compared to pure oil. Thermal conductivity was calculated using the measured values of thermal diffusivity and specific heat values at range of temperatures of (30°C- 90°C). Thermal diffusivity and specific heat values were measured by LFA (Laser Flash analysis) and DSC (Differential Scanning Calorimetry), respectively. Furthermore, Broadband dielectric spectroscopy was used to measure electrical conductivity for nanofluids for a range of frequencies (0.1Hz to 1MHz) and a range of temperatures for heating and cooling. Temperatures range was from 20°C to 100°C for heating and from 95°C to 25°C for cooling with step 10°C. A decrement in thermal diffusivity and thermal conductivity and an increment in specific heat values and electrical conductivity values with increasing temperature were observed. For the optimum nano-sheets concentration, an enhancement of the thermal conductivity by 35% was observed.

There is a need for accurate and rapid thermal conductivity (k), thermal resistivity (R) and thermal diffusivity (D) measurements of food products and soils. Knowledge of the thermal properties of foods allows design of novel food processing techniques in the food industry. In soils, knowledge of the thermal properties allows energy balance and heat transfer calculations. Existing thermal conductivity probes only measure conductivity and cannot be used on liquid samples. A new, simple, easy to use system allows rapid and simultaneous conductivity, resistivity and diffusivity measurements, including liquid samples. The system consists of a hand-held readout and a single-needle sensor. The single-needle sensor consists of a stainless steel needle containing a heater and thermistor. The thermal conductivity and diffusivity are calculated by monitoring the dissipation of heat versus time given a known voltage applied. The range of thermal conductivity measurements is 0.1 to 2.0 Wm -1 C -1 with an accuracy of 5%. The range of thermal resistivity is 0.5 to 10 mCW -1 with an accuracy of 5%. The range of thermal diffusivity measurements is 0.1 to 1.0 mm 2 s -1 with an accuracy of 10%. The objective of this study is to evaluate the performance of the new thermal properties system on selected foods and soils, then compare the data to published literature values. The accuracy and repeatability of the probe is evaluated using glycerin as a reference material. This new thermal properties system provides rapid, accurate and economic means for simultaneously measuring thermal conductivity and thermal diffusivity on selected foods and soils, including liquid samples.

A thermal response method of calculating a soil's thermal properties when backfill material information is unavailable

This paper presents and interprets photoacoustic (PA) infrared spectra and four different thermophysical properties (thermal conductivity, thermal diffusivity, volumetric specific heat and thermal effusivity) for four sets of hydrocarbon cokes. A total of 12 samples, with varying histories, were analyzed. These cokes are a by-product of the upgrading of bitumen to Syncrude Sweet Blend (a blend of hydrotreated components), and were obtained from several locations in the thermal cokers operated by Syncrude Canada Ltd. in Fort McMurray, Alberta, Canada. PA infrared spectroscopy provides detailed information on the amount and type of residual aromatic hydrocarbons in cokes; aliphatic hydrocarbons are sometimes detected in smaller quantities. Three of the thermophysical properties (thermal conductivity, diffusivity and effusivity) display systematic differences among the cokes. On the other hand, volumetric specific heat hardly varies, a phenomenon that accounts for the observed proportionality between thermal diffusivity and conductivity. Analogous relationships exist between thermal effusivity and both thermal conductivity and thermal diffusivity for these cokes. The magnitudes of these three thermophysical properties tend to increase as aromatics contents, determined by PA spectroscopy, decrease.

A study of the thermophysical characteristics, heat resistance, and thermal erosion resistance of high-temperature structural ceramics (SC), which was developed at NTUU "I. Sikorsky Kyiv Polytechnic Institute" under the supervision of Corresponding Member of the National Academy of Sciences of Ukraine, Professor P. I. Loboda was made. This high-temperature structural ceramics is intended for use in aerospace engineering, in particular - for the manufacture of aerodynamic surfaces of reusable hypersonic aircraft and heat-stressed elements of the gas-dynamic paths of their engines. The samples of B4C-SiC-B6Si ceramics of two compositions (No. 1 and No. 2) were studied, which differ in the mass content of the initial components. Temperature dependences of the specific heat and thermal conductivity of the spacecraft, radiation coefficient, heat resistance in an oxidizing environment, and the thermal erosion resistance in supersonic flow of combustion products of an air-kerosene fuel mixture were determined. The temperature dependence of the specific heat was determined using an IT-c-400 instrument (in the range of 40 °C - 440 °C) and by the calculation of the temperature dependences of the specific heat capacity of the system components following the Reno rule (up to 2100 °C). The temperature dependence of the thermal conductivity coefficient of the SC of composition No. 1 was determined by solving the inverse heat conduction problem on a computer model based on experimental data. Temperature fields and heat fluxes were obtained under conditions of one-sided heat-ing with a reducing flame of a propane-oxygen welding burner. The thermal conductivity coefficient of SC composition No. 1 increases from 11 W/(m×K) at 20 °С to 25 W/(m×K) at 1400 °С. Its radiation coefficient in the temperature range 1000 °С - 1400 °С is ε = 0.96 ± 0.02. Heat resistance of SC of both compositions in the oxidizing flame of an oxygen welding burner at a surface temperature of 1400 °C has demonstrated that after two hours of heating, the average values of mass ablation for the two tested samples of compositions №1 and № 2 respectively 2.1% and 1.4% (a sample thickness of 4 mm). Tests in the supersonic flow of combustion products at the same surface temperature confirm the high resistance of the material to thermoerosion in the oxidizing medium. The change in the morphology of the heated surface of the sample after six five-minute heating cycles was manifested only by an increase in its roughness without visible oxidation. High thermal conductivity, heat and thermoerosion resistance, radiation coefficient of the studied SC at a temperature of 1400 °C in combination with low density (2.7 g / cm3) make this high-temperature structural material of aerospace technology promising for use.