Thermal Conductivity Of Water Research Articles

Figures-of-Merit Analysis Using the Thermophysical Properties of Water and Ethylene Glycol Based Reduced Graphene Oxide/Nanodiamond Hybrid Nanofluids

The water and ethylene glycol based stable rGO/nanodiamond hybrid nanofluids were prepared and used for thermophysical properties analysis. The thermophysical properties were measured experimentally at various particle loadings from 0.2% to 1.0% and various temperatures ranging from 20 to 60 °C. From the measured thermophysical properties the figures-of-merit were analyzed by assuming constant heat flux and turbulent boundary conditions by using different models, and also by assuming the hybrid nanofluids flows through a tube. Results indicate that the thermal conductivity of water and ethylene glycol based hybrid nanofluids at Φ = 1.0% vol. is enhanced about 27.87% and 18.8% at 60 °C; viscosity of water and ethylene glycol based hybrid nanofluids at Φ = 1.0% vol. is also enhanced by 72.15% and 86.62% compared to their base fluids at 20 °C. The density is also increased with an increase of particle loadings, whereas, the specific heat is decreased with a rise of particle loadings. Experimental thermophysical properties are fitted into regression equations by using multi linear regression method. The figures-of-merit of all the prepared hybrid nanofluids show its value is less than one under the used particle loadings and temperatures.

The effect of air solubility on the Kapitza resistance of the copper-water interface

We perform a calibration of the force fields between copper, water, and air based on experimental parameters, such as the value of the water contact angle on a bare copper surface, the bulk density and thermal conductivity of water and air. Besides, the air solubility in water is estimated at different pressures and temperatures. Using nonequilibrium molecular dynamics (NEMD) simulations, we investigate the effect of the air on Kapitza resistance at high pressure in a copper-water-air system. The results show that a thick air layer at the copper–water interface reduces the ordering of the water layers adjacent to the copper surface, and is responsible for an increase in the Kapitza resistance. Moreover, we find that high pressure can induce highly-ordered water layers that significantly promote the phonon transport across the solid-liquid-gas interface, which leads to the reduction of the Kapitza resistance. Furthermore, we analyze the normalized copper–water Kapitza resistance RK,eff/R0 for different gas solubilities and pressures. Here, RK,eff denotes the effective Kapitza resistance between copper and water, where the temperature jump is approximated by the temperature difference across the air layer. R0 is the Kapitza resistance at ambient pressure in the copper–water system without air. The normalized Kapitza resistance suggests that higher pressures can reduce the contribution of the thickness of the air layer on the increase of Kapitza resistance. We propose a simple model for the effective Kapitza resistance taking into account a thin air layer at the solid–liquid interface. At ambient conditions, the model predicts a 3-fold increase in the Kapitza resistance for a 1nm thick air layer.

Couple stress and Darcy Forchheimer hybrid nanofluid flow on a vertical plate by means of double diffusion Cattaneo–Christov analysis

A three-dimensional Darcy Forchheimer mixed convective flow of a couple stress hybrid nanofluid flow through a vertical plate by means of the double diffusion Cattaneo–Christov model is presented in this study. The influence of high-order velocity slip flow, as well as a passive and active control, is also considered. The motive of the research is to develop a computational model, using cobalt ferrite (CoFe2O4) and copper (Cu) nanoparticles (NPs) in the carrier fluid water, to magnify the energy and mass communication rate and boost the efficiency and performance of thermal energy conduction for a variety of commercial and biological purposes. The proposed model becomes more significant, with an additional effect of non-Fick's mass flux and Fourier's heat model to report the energy and mass passage rate. The results are obtained through the computational strategy parametric continuation method. The figures are plotted to reveal the physical sketch of the obtained solution, while the statistical assessment has been evaluated through tables. It has been observed that the dispersion of Cu and CoFe2O4 NPs to the base fluid significantly enhances the velocity and thermal conductivity of water, which is the most remarkable property of these NPs from the industrial point of view.

The impact of moisture on thermal conductivity of fabrics

The article presents the experimental results of the thermal conductivity of absorbent fabrics for increasing relative amount of water in the fabric. Measurements confirm that the effective thermal conductivity of fabrics at low moisture level is proportional to the relative amount of water absorbed in fabrics. With increasing relative amount of water in the fabric, effective thermal conductivity stabilizes around the value comparable with the thermal conductivity of water. The experimental results are compared with the theoretical linear model.

Heating and Cooling Rate Study on Water Cooling Thermal Cycler using Aluminium Block Sample

Temperature measurement has many applications in medical devices. In recent days, body temperature become the main screening procedure to justify people infected by SARS-CoV-2. Related to pandemic situation due to SARS-Cov-2, Polymerase Chain Reaction (PCR) method become the most accurate and reliable detection method. This method employs a device named PCR machine or Thermal Cycler. In this research, we focus to build a Thermal Cycler using a low-cost material such as aluminium and using a liquid coolant as the cooling system. We use 2 types of coolant solution: mineral water and generic liquid coolant. Peltier device in thermal cycler serves as heating and cooling element. In heating rate experiments, generic liquid coolant shows a better result than using mineral water due to specific heat capacity and thermal conductivity of water. In the cooling rate experiments, the water pump is activated to stream the liquid solution, the flow rate of liquid solution is influenced by viscosity of the liquid. Generic liquid coolant has approx. 4,5 times greater viscosity than water. The higher flow rate means better performance for cooling rate. Using 2 pieces of 60-Watt heaters and a 60-Watt chiller and aluminium material as block sample, our research shows a heating and cooling rate up to approx. 0,1°C/s. Compared to commercially thermal cycler, our thermal cycler has a lower wattage; this lower wattage performance has been tradeoff with lower ramping rate. Some factors are suspected become the source of contributors of lower ramping rate.

Experimental investigation on thermal conductivity and stability of water-graphite nanofluid

Enhanced thermal conductivity of nanofluids has proven importance in enhancing heat transfer for many application. In this study, thermal conductivity of graphite nanopowder dispersed in water at different temperatures was studied experimentally. Stable nanofluids of different concentrations (0.2 vol%, 0.5 vol%, 0.8 vol%, 1 vol% and 1.5 vol%) are prepared using ultrasonic cleaner by sonicating for 3 hour. Thermal conductivity was measured from temperature 25 to 55 ºC with an interval of 5 ºC using KD2 Pro thermal properties analyser. Experimental results showed that thermal conductivity increases with increase in temperature and volume concentration. Thermal conductivity of Water – Graphite nanofluid showed enhancement of 5.6% to 20.42% for 0.2 vol% to 1.5 vol% of concentration at 25 ºC respectively. However, the maximum improvement of 39.72% was found at 1.5% of concentration at 55 ºC compared to water. A correlation was developed considering the effect of temperature and concentration using the regression method. The proposed correlation effectively predicts the thermal conductivity of Water – Graphite nanofluids with an accuracy of ±2.8%.

FBG-Based Sensor for the Assessment of Heat Transfer Rate of Liquids in a Forced Convective Environment.

The assessment of heat transfer is a complex task, especially for operations in the oil and gas industry, due to the harsh and flammable workspace. In light of the limitations of conventional sensors in harsh environments, this paper presents a fiber Bragg grating (FBG)-based sensor for the assessment of the heat transfer rate (HTR) in different liquids. To better understand the phenomenon of heat distribution, a preliminary analysis is performed by constructing two similar scenarios: those with and without the thermal insulation of a styrofoam box. The results indicate the need for a minimum of thermal power to balance the generated heat with the thermal losses of the setup. In this minimum heat, the behavior of the thermal distribution changes from quadratic to linear. To assess such features, the estimation of the specific heat capacity and the thermal conductivity of water are performed from 3 W to 12 W, in 3 W steps, resulting in a specific heat of 1.144 cal/g °C and thermal conductivity of 0.5682 W/m °C. The calibration and validation of the HTR sensor is performed in a thermostatic bath. The method, based on the temperature slope relative to the time curve, allowed for the measurement of HTR in water and Kryo 51 oil, for different heat insertion configurations. For water, the HTR estimation was 308.782 W, which means an uncertainty of 2.8% with the reference value of the cooling power (300 W). In Kryo 51 oil, the estimated heat absorbed by the oil was 4.38 kW in heating and 718.14 kW in cooling.

Field and laboratory metabolism and thermoregulation in rhinoceros auklets.

Seabirds spend most of their lives at sea, except when visiting their breeding sites. Since the thermal conductivity of water is 25 times higher than that of air, seabirds resting on water lose heat and expend a considerable amount of energy for thermoregulation. For example, rhinoceros auklet (Cerorhinca monocerata), a medium-sized (480620 g) alcid, spends most of its time floating on the sea. In order to estimate the cost of this behavior in terms of their daily energy expenditure (DEE), we studied rhinoceros auklets breeding on Teuri Island, Hokkaido Japan. We measured their resting metabolic rate (RMR) in air and on water by respirometry, and estimated their DEE by the doubly labeled water method. While RMR on water did not vary significantly between 10C and 15C, it was significantly higher at 5C. Air temperature (5.020.0C) had no effect on RMR. The DEE of free-ranging auklets averaged 1,005.5kJday1 (130.2, n=3). Our results indicate that RMRs are elevated for auklets resting on water, particularly below their lower critical temperature (LCT), compared with in air. Accordingly, spending time above their LCT on water at any time of year will provide enhanced benefits, particularly to seabirds such as rhinoceros auklets which rest a considerable amount of time on water.

An effective thermal conductivity model of rocks considering variable saturation and pore structure: Theoretical modelling and experimental validations

The effective thermal conductivity (ETC) of rocks is crucial for many geological and engineering applications and projects. In this study, a three-component ETC model was proposed, which includes seven parameters, that are, the thermal conductivities of water (λw), gas (λg) and solid phase (λs), the porosity (φ), the coefficient of shape factor (n), the weighted harmonic parameter (η) and saturation degree (Sr). The methods to establish the parameters of the proposed model were described with validation carried out using several experiments including X-ray diffraction (XRD) test, porosity test and thermal conductivity test. Comparisons performed indicated that the new proposed model was flexible enough to reflect the variation of the ETC with saturation degree. Furthermore, the sensitivity analysis and grey correlation analysis were given in examining the effect of the parameters included in the model. The results showed that: 1) The parameter sensitivity analysis and grey correlation analysis of ETC show that the ETC is most sensitive to the thermal conductivity of solid phase (λs), followed by coefficient of shape factor (n), weighted harmonic parameter (η) and saturation degree (Sr), and less sensitive to the porosity (φ). 2) When the pore shape of the porous media is irregular or the thermal conductivity ratio of the continuous phase and discontinuous phase is larger than 100, n is a key parameter that can tremendously influence the value of ETC. 3) Although the change of η does not influence the maximum and minimum values of ETC, it can greatly affect the variation of ETC when 0 < Sr < 1.

A Numerical Investigation on Natural Convection Heat Transfer in Annular-Finned Concentric Horizontal Annulus Using Nanofluids: A Parametric Study

Natural convection heat transfer in a concentric horizontal annulus with annular fins is numerically studied. Due to the low thermal conductivity of water, CuO-water and Al2O3-water nanofluids were used as heat transfer fluids. The effect of three different parameters, including fin spacing, fin eccentricity, and fin thickness at different fin diameters and Rayleigh number range of 104 to 9 105, were studied. The obtained results revealed that Al2O3-water nanofluid has the highest heat transfer rate. The calculated heat transfer rates for Al2O3-water nanofluid for Rayleigh numbers of 9 105, 105, and 104 were respectively up to 12.1%, 26.2%, and 31.6% higher than the heat transfer rate obtained for water. The best heat transfer rate occurred at the fin spacing range of 2 to 3 mm at Rayleigh number of 9 105. Moreover, it was observed that by decreasing the Rayleigh number, the maximum heat transfer rate took place at higher fin spacing. It was concluded that fin eccentricity improves the heat transfer rate, especially for low fin spacing. Furthermore, it was demonstrated that fin eccentricity could improve the heat transfer rate by up to 50.2%. Simulation results indicated that fins with low thickness have higher heat transfer rates than those with higher thickness at lower fin spacing. However, fins with high thickness have higher heat transfer rates than those with lower thickness at higher fin spacing.

Effect of copper nanoparticles on thermal behavior of water flow in a zig-zag nanochannel using molecular dynamics simulation

Molecular dynamics (MD) simulation is one of the most common simulation methods which predict the dynamical and thermodynamical properties of atomic structures based on classical Newton's laws. In this study, the effect of copper nanoparticles on the thermal behavior of the fluid in zig-zag nanochannel was investigated using molecular dynamics simulation. In our simulations, water molecules were used to model the base fluid, and platinum atoms were used to model the nanochannel walls. To investigate the effects of copper nanoparticles on the base fluid, physical quantities such as potential energy, density, velocity, temperature profiles, and finally, the thermal conductivity has been reported. The results show that, by adding nanoparticles to the base fluid, the maximum density increases. On the other hand, the maximum velocity decreases from0.22°A/ps to 8°A/ps to. From the velocity behavior of the fluid particles, the temperature decreases from 363 K to 330 K. Furthermore, a study of the thermal conductivity of the simulated system by using the Green-Kubo method showed an increase in the thermal conductivity of water up to 0.679 W m−1 K−1. The increase of the nanofluid thermal conductivity is consistent with the increase in heat transfer, which can be a promising parameter in industrial applications.

On determination method of thermal conductivity of soil solid material

Soil thermal conductivity always calculated by the thermal conductivity models and the thermal conductivity of each phase in soils, the thermal conductivity of water and gas can be obtained by physicochemical methods, while the test values of soil solid material always effected by the pore waters or pore gases. To determine the thermal conductivity of soil solid material, the calculation relationship between the thermal conductivity of soil solid material and thermal conductivity of soil is deduced based on the geometric average method and the Maxwell-Eucken method, respectively. Meanwhile, a theoretical model for calculating the two-phase medium (i.e., the soil solid material and water) is established by combining the software APDL, FORTRAN, ABAQUS, and the relationship between the thermal conductivity of the two-phase medium and the thermal conductivity of soil solid material is obtained. The thermal conductivity of saturated silty clay, saturated silty soil and saturated sand with different dry densities were tested by the probe method, and the thermal conductivity of soil solid materials are obtained according to the three calculation relationships between thermal conductivity of soil solid material and thermal conductivity of soil which established herein. Meanwhile, the thermal conductivity of model soils were tested to verify the absolute errors of the abovementioned calculation methods. The results show that, the nonlinear behavior induced by the soil-water interface will largely affect the test error of thermal conductivity of soil solid material, the theoretical model proposed herein can reduce the dispersion of the thermal conductivity of soil solid material, which can provide a reference for the prediction of soil temperature fields.

Porous heat exchange tube with ultra-thin dense skin layer via NIPS for AGMD process

In this paper, a kind of poly(vinylidene fluoride) (PVDF) porous heat exchange tube (HET) was prepared via non-solvent induced phase separation (NIPS) method. This porous HET possessed an ultra-thin dense skin layer of 2 μm. Since the thermal conductivity of water is higher than that of PVDF, filling the pores with water can significantly improve the heat performance of the porous HET. A full plastic double-pipe air gap membrane distillation (AGMD) module was fabricated with the porous HETs and PVDF hollow fiber membranes. In the AGMD process, the wetting treatment can make the membrane distillation flux (J) and the gained output ratio (GOR) increased by 30%. During the long-term stability test, the maximum conductivity of distillate water was only 17.2 μS/cm. The experimental results demonstrated that the porous HET can be applied for the AGMD process to treat high saline brine, and the ultra-thin dense layer can prevent the leakage of saltwater.

Pool Boiling Heat Transfer Coefficient of Low-Pressure Glow Plasma Treated Water at Atmospheric and Reduced Pressure

This paper investigates the influence of low-pressure glow plasma water treatment on boiling phenomenon. The presented results show the novel influence and potential new applications of low-pressure glow plasma treated water. Low-pressure glow plasma water treatment affects some of its physical properties such as surface tension, pH, and electric conductivity; this is due to changes in the water structure. An experimental analysis aimed to investigate the effect of such a treatment on the boiling heat transfer coefficient of water, and to assess the stability of GPTW. The experiments were carried out at atmospheric and reduced pressure for heat fluxes up to 70 kW/m2. The analysis shows significant deterioration of the boiling heat transfer coefficient under reduced pressure. In addition, the plasma treatment process had no significant effect on the thermal conductivity of water, as confirmed experimentally. A slight increase was observed, but it was within the measuring error range of the instruments used.

Enhancing thermal conductivity of water by using TiC nanopowder with cryogenic treatment

ABSTRACTThe thermal conductivity of TiC/water nanofluid is found out at different weight fractions of 0.1%, 0.2% and 0.3% and the results are compared with water (base fluid). It has been shown that the thermal conductivity of TiC/water nanofluid is improved when compared with water. Then, an inexpensive cryogenic treatment is adopted to find the thermal conductivity of cryo-TiC/water nanofluid. It has been found that the cryogenic treatment on TiC nanopowder is further enhancing the thermal conductivity of TiC/water nanofluid. The lattice vibration of the particles is responsible for the improvement of thermal conductivity.

Studying the effective longitudinal turbulent transfer at transverse streamlining of in-line tube bundles

The experimental values of the effective thermal conductivity of water at transverse streamlining of the in-line rod bundles with square packing have been obtained. The effective thermal conductivity of water was measured in the direction parallel to the axes of the rods. The measurement method implied mixing of two flat parallel water flows in the working area; the latter moved at the same velocities, but had different temperatures. By measuring the flow temperatures before and after the mixing area, the amount of heat transferred from the hot to the cold flow was determined and the effective thermal conductivity of the liquid was calculated. In the investigated range of Reynolds numbers (from 7·103 to 8·104), calculated by the velocity in a narrow section, the experimental effective thermal conductivity of water showed a linear increase with increasing velocity and good agreement with the results of calculations by the integral turbulence model. The obtained experimental data have confirmed the possibility of using an integral turbulence model to calculate the parameters of the anisotropic porous solid model, used in CFD codes simulating thermal-hydraulic processes in the active zones of nuclear reactors and heat exchangers.

Effect of temperature and mole fraction on viscosity and thermal conductivity of water and ethanol mixture

The viscosity and thermal conductivity of the mixture as a heat exchange medium are the main factors affecting the heat transfer performance. In this paper, the mixture of water and ethanol is used as the research object. The viscosity and thermal conductivity of gas and liquid are calculated by various methods. Combined with the experimental data, the variation law with temperature and mole fraction is analysed, and the difference of different calculation methods is compared. When calculating the viscosity of water and ethanol mixture, the Teja and Rice method and the Jouyban and Acree method are suitable for different temperature ranges. The Jamieson method is more practical than the Baroncini method, when calculating the thermal conductivity. Finally, the calculation results are applied to an ejector refrigeration system calculation program, and it is found that the viscosity and thermal conductivity of the heat exchange medium have an important influence on the accuracy of the system performance calculation.

The Ecological Outcome of Climate Change in Lake Kinneret—Thermal Pollution

Water quality deterioration as a result of pollution comprised of several aspects, among others: nutrient input loads, fishery management, hydrological budget, toxicity, watershed deforestation, soil exposure, and exotic invaders. Thermal pollution is mostly considered as the impact of power or nuclear Station effluent or the effect of exceptional thermal abrupt shock. The long-term influence of global warming consideration is not extensively studied. The long-term (1969-2001) effect of climate change (warming and precipitation decline) on the Lake Kinneret ecosystem is presented. Water and air Temperature, Heat Capacity and Thermal conductivity of water combined with reduced precipitation accompanied by lake water level decline are analyzed. It was found that the temperature of surface water increased with WL decline and decreased in deep layers during high WL. Future management design is suggested.

COMPRESSIVE STRENGTH AND THERMAL CONDUCTIVITY OF WATER AND AIR CURED PORTLAND CEMENT-FLY ASH-SILICA FUME MORTARS

This paper investigated the compressive strength and thermal conductivity of water and air cured Portland cement-fly ash-silica fume mortars. The results showed that density, compressive strength and thermal conductivity of blended cement mortars with fly ash were lower than Portland cement control. However, blended cement mortars that contained silica fume as replacement cement both in binary and ternary phase were higher than fly ash mixes and tends to increase with increase silica fume used as cement replacement due to increased C-S-H phase formation from pozzolanic reaction and its filler effect. In ternary phase, compressive strength and thermal conductivity of 10FA5SF and 5FA10SF mixes had values higher than Portland cement control while 20FA10SF mixes had values similar to Portland cement control. The density, compressive strength and thermal conductivity of blended cement mortars those cured in saturated lime water were higher than air cured specimens. Moreover, relationships between compressive strength and thermal conductivity as well as density and thermal conductivity were compared. X-ray diffraction traces show that intensity of C-S-H phase increased while intensity of Ca(OH)2 decreased with increased silica fume content due to the increased pozzolanic reaction when compared to the reference FA mix.

Nano-fluid thermal processing of watermelon juice in a shell and tube heat exchanger and evaluating its qualitative properties

Abstract Due to specific thermophysical properties of nanofluids, compared with conventional thermal fluids (steam and hot water), their application in diverse industries, to improve heat transfer and to save energy, has increased. One important aspect of applying nanofluid thermal processing is shortening the process time which could have high potentials in the food industry since nutritional and bioactive components would be maintained much higher than common thermal processes. In this project, possibility of replacing water with alumina-water nanofluids (2 and 4% concentrations) during high temperature short time processing (75, 80 and 85 °C for 15, 30 and 45 s) of watermelon juice in a shell and tube exchanger regarding its qualitative properties (lycopene, vitamin C, color, pH and TSS) was investigated. Reduction in process time when applying 2 and 4% nanofluids, up to 24.88 and 51.63%, had considerable effects on maintaining qualitative properties for watermelon juices. For instance, thermal processing by 0, 2 and 4% nanofluids at 75 °C for 15 s could keep 81.15, 84.81 and 91.28% of lycopene and 61.11, 63.70 and 67.04% of vitamin C, respectively. pH and TSS indices of processed watermelon juices were in the range of 5.58–5.82 and 9.0–9.4, respectively, showing no considerable correlation with the heating media used in thermal processing. Our results revealed that nutritional and physicochemical properties of watermelon juice processed with alumina nanofluids were better than common thermal processing by water with 9.89, 6.18 and 50.38% higher lycopene, vitamin C and color retention in the final product, respectively. Industrial Relevance Even so thermal processes are effective in preventing microbial spoilage of fruit juices, high volume of energy transfer in long durations into food products with heat sensible ingredients or properties results in biochemical and nutritional losses, development of unpleasant reactions, changes in overall quality of food products, and high energy consumption. Nowadays, consumers demand for food products with long shelf lives, high quality and proper prices are increasing. So, to meet these demands, food industries are looking for alternative thermal technologies to reduce losses in food characteristics and process costs, and introduce a fresh, nutritious, healthy and affordable food produce. Thermal conductivity of conventional fluids is much lower than metals and oxidized metals. For example, thermal conductivities of copper and alumina are 700 and 60 times higher than the thermal conductivity of water, respectively. Accordingly, fluids with suspended particles of metals or oxidized metals benefit from better heat transfer properties. The term of Nanofluid refers to each stable two-phase compound that includes both base fluids and nanoparticles (lower than 100 nm, at least in one dimension). There is no research dealing with effects of adding nanoparticles to conventional thermal fluids for fruit juices processing. So, the goal of this research was to introduce nanofluid technology for thermal processing of food products for the first time, increasing heat transfer efficiency in shell and tube exchangers by nanofluids and frugality in energy consumption for pasteurization, reducing thermal processing duration and better quality retention of food products.