Experimental Investigation Of Thermophysical Properties Research Articles

Experimental investigation of thermophysical properties of propylene glycol based secondary fluids for ground source heat pumps and indirect refrigeration systems

More than 1.7 million ground source heat pumps are currently in operation in the European Union and a large majority of systems is using propylene glycol as secondary fluid. In this study the thermophysical properties of propylene glycol solutions with specific freezing points between −5 and −50 °C are investigated at low temperatures of interest for refrigeration and heat pump applications. The experimentally determined data are compared to a large number of data from the literature. It has been found that the freezing point results for all concentrations were in very good agreement with both Melinder (2010) and ASHRAE (2021) data. Moreover, the literature data and present study for concentrations above 40 wt-% have different density curve slopes compared to ASHRAE data. The viscosity results for concentrations below 40 wt-% were up to 21.5 % higher than ASHRAE data and the viscosity results for solutions with concentrations above 40 wt-% were lower by up to 9.7 %. The thermal conductivity results for concentrations above 40 wt-% were 10 % higher than ASHRAE (2021) data. The experimental specific heat capacity curves and other studies do not have the same linear trend as Melinder (2010) and ASHRAE (2021) data. This difference indicates that currently available ASHRAE data have been indirectly computed from thermal conductivity data or that they have not been fully experimentally validated. Finally, more studies are required to investigate concentrations below 25 wt-% to identify solutions with higher specific heat capacity than water that could be of interest for specific applications.

Experimental investigation of thermophysical properties of synthesized Mg–Al bimetal oxide/water nanofluid

Experimental investigation of thermophysical properties of synthesized Mg–Al bimetal oxide/water nanofluid

Experimental investigation of thermophysical properties of ethylene glycol based secondary fluids

Aqueous solutions of ethylene glycol are commonly used as secondary fluids in different indirect refrigeration systems and heat pumps as well as nanofluids. A very extensive literature review has been done, including more than 90 references published from 1905 to 2023. Despite the wide application and importance, especially in the energy sector, ethylene glycol solutions seem to be less investigated in low temperature ranges and more research is required to improve the quality and quantity of available data. The novelty of this paper is to investigate the most important thermophysical properties of ethylene glycol solutions in low temperatures. In this study a different approach was made and solutions having a specific freezing point temperature (between -5 and -50 ºC) rather than specific concentration were investigates in temperature ranges applicable for different cooling applications. The concentrations giving a certain freezing point temperature seemed to deviate in some cases with 1–2 wt-% between different sources. Nevertheless, the density results were in rather good agreement with all reference data. The viscosity results were lower by up to ±10% compared to reference values. Additionally, the obtained experimental results for thermal conductivity were higher by up to 12% compared to ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) data. The specific heat capacity results were higher by up to 14.6% and 5.4% than current reference data. There is a high probability that the current ASHRAE data for specific heat are actually indirectly calculated values from thermal conductivity data and not validated using differential scanning calorimetry techniques.

Experimental investigation of thermophysical properties, tribological properties and dispersion stability of nanodiamond-based nanolubricant for air conditioning systems

Compressor oil lubricant plays a vital role in enhancing the performance of air conditioning (AC) systems. Thermophysical and tribological properties, as well as physical stability, of Polyolester (POE) oil dispersed with nanodiamond (ND) have been evaluated experimentally to determine its suitability and feasibility for utilization as a nanolubricant in AC compressors. Thermophysical properties correlations were developed for the ND/POE nanolubricant with volume percentage and temperatures ranges of 0.05 to 0.5% and 10 to 100°C, respectively. The density, thermal conductivity, and viscosity were found to increase with increasing ND particle concentration and reduced with increasing preparation temperature. The developed thermophysical properties correlations showed relatively accurate predictions with a maximum mean absolute error (MAE) of 6%. The nanolubricant at 0.1 vol.% showed the lowest coefficient of friction (COF) to improve the frictional power losses. The ND/POE nanolubricant exhibited a well-dispersed stability using both the photograph image capturing approach and ultraviolet-visible spectroscopy (UV-vis) analysis. As a result of the enhanced thermal, tribological and stability qualities, prolonged lifespan and cool operation of AC compressors are anticipated when utilizing POE oil containing up to 0.1 vol.% of ND.

Preparation, characterization and experimental investigation of thermophysical properties of stable TiN nanofluid for solar thermal application

Preparation, characterization and experimental investigation of thermophysical properties of stable TiN nanofluid for solar thermal application

Experimental Investigations of Thermophysical Properties and Convective Heat Transfer of Al2O3 and CuO Nanofluids in a Copper Tube: Proposing New Correlations

The performance of the Alumina/water and copper oxide/water nanofluids in a heat exchanger is experimentally investigated for particle weight concentrations ranging from 0.02 wt% to 0.5 wt%. The alumina/water and copper oxide/water nanofluids were prepared using two-step methods in an aqueous solution with 0.01 wt% CTAB (Cetyl Trimethyl Ammonium Bromide) as a surfactant at different concentrations and were characterized using HRTEM (High-Resolution Transmission Electron Microscopy) technique. Laminar forced convective heat transfer analysis using alumina and copper oxide nanoparticles suspended in water in a circular horizontal tube under constant heat flux boundary conditions was performed. The effect of various flow conditions and weight concentrations in the local heat transfer coefficient and pressure drop of both the nanofluids were investigated. Reynolds number varied from 1275 to 2200. Results show that 12.7 & 14.5 % thermal performance enhancement was observed with 0.5 wt% of Al2O3 and CuO nanofluids. Maximum, 50.62 % enhancement was observed in the average heat transfer coefficient by Al2O3 nanofluids, whereas 52.74 % was observed using CuO nanofluids using 0.5 wt% concentrations of the nanofluids and at Reynolds number of 2200. Correlations were proposed for thermal conductivity, viscosity, and Nusselt number for both the nanofluids with the maximum and minimum deviations of ±9 % and ±10 %, respectively.

Experimental investigation of thermophysical properties and heat transfer characteristics of hybrid nanofluids based on particle size

In heat transfer applications, nanofluids are utilized to increase thermal conductivity and heat transfer coefficient. The difficulty of nanoparticle stabilization in the fluids is a significant problem in heat transfer applications. Heat exchanger materials may wear and erode as a result of the additional nanoparticle. When compared to mono nanofluids, this can be lowered by using hybrid nanofluids. In this work, hybrid nanofluids are used in a radiator under laminar flow at 75?C, and the effect of volume concentration on heat transfer enhancement is investigated. The thermophysical characteristics of hybrid nanofluids are investigated using SiC and Al2O3 at 0.1 vol.% and 0.2 vol.%. The results revealed that a hybrid nanofluid with a higher volume concentration improves heat transfer. Finally, regression analysis for laminar flow is carried out and correlations for experimental Nusselt number and friction factor values were developed. The impact of particle size, flow rate, and temperature on the radiator?s heat transfer enhancement is investigated using hybrid nanofluid at 75?C. It is observed that the size of the nanoparticle has a substantial effect on heat transfer characteristics. It is concluded that using smaller-sized hybrid nanoparticles of Al2O3/SiC-S with less volume concentration enhances heat transfer and reduces radiator size compared to conventional coolants.

Experimental investigation of thermo-physical properties of MgO-MWCNT (75–25%)/10W40 as a new nano-lubricant

Experimental investigation of thermo-physical properties of MgO-MWCNT (75–25%)/10W40 as a new nano-lubricant

Experimental Investigation of Thermo-Physical Properties of Tri-Hybrid Nanoparticles in Water-Ethylene Glycol Mixture

In recent years, research has focused on enhancing the thermo-physical properties of a single component nanofluid. Therefore, hybrid or composite nanofluids have been developed to improve heat transfer performance. The thermo-physical properties of the Al2O3-TiO2-SiO2 nanoparticles suspended in a base of water (W) and ethylene glycol (EG) at constant volume ratio of 60:40 and different volume concentrations were investigated. The experiment was conducted for the volume concentrations of 0.05, 0.1, 0.2, and 0.3% of Al2O3-TiO2-SiO2 nanofluids at different temperatures of 30, 40, 50, 60, and 70 °C. Thermal conductivity and dynamic viscosity measurements were carried out at temperatures ranging from 30 to 70 °C by using KD2 Pro Thermal Properties Analyzer and Brookfield LVDV III Ultra Rheometer, respectively. The highest thermal conductivity for tri-hybrid nanofluids was obtained at 0.3% volume concentration, and the maximum enhancement was increased up to 9% higher than the base fluid (EG/W). Tri-hybrid nanofluids with a volume concentration of 0.05% gave the lowest effective thermal conductivity of 4.8 % at 70 °C temperature. Meanwhile, the dynamic viscosity of the tri-hybrid nanofluids was influenced by volume concentration and temperature. Furthermore, tri-hybrid nanofluids behaved as a Newtonian fluid for volume concentrations from 0.05 to 3.0%. The properties enhancement ratio (PER) estimated that the tri-hybrid nanofluids will aid in heat transfer for all samples in the present. The new correlations for thermal conductivity and dynamic viscosity of tri-hybrid nanofluids were developed with minimum deviation. As a conclusion, the combination of the enhancement in thermal conductivity and dynamic viscosity for tri-hybrid at 0.3% volume concentration was found the optimum condition with more advantage for heat transfer than other concentrations.

Experimental investigation of thermo-physical properties of drilling fluid integrated with nanoparticles: Improvement of drilling operation performance

Undoubtedly, the extraction of oil and gas from the reservoirs requires drilling processes. Drilling fluid is also required to perform drilling processes. The drilling fluid has several applications and one of its functions is to cool the bit. Normally, drilling fluids used in the world have a relatively low ability to transfer the heating from the bit. Therefore, cooling the bit is not done well. Therefore, solutions to increase the efficiency of drilling fluids in the field of heat transfer should be proposed. It is obvious that specific surface area is one of the variables affecting heat transfer. In other words, if the specific surface area of the drilling fluid molecules increases, the rate of heat transfer will increase. Since nanoparticles have a very high specific surface area, their use can be suggested. Because nanoparticles have a very high specific surface area, they can be used in the structure of drilling fluid components. Therefore, in this study titanium dioxide nanoparticle and carbon nanotube have been used to change the thermo-physical properties of drilling fluid. Results show the amount of specific heat increases about 1.26% by decreasing the size of titanium dioxide nanoparticles from 76 nm to 54 nm. In addition, experimental results show that the ratio of convective heat to conductive heat for drilling fluid integrated with carbon nanotubes is about 30% higher than drilling fluid integrated with titanium dioxide nanoparticles. Results show that the rate of heat transfer coefficient increases from about 2900 W/m2. oC to about 4000 W/m2. oC by decreasing the size of titanium dioxide nanoparticles from 76 nm to 54 nm. Also, it has been observed that the convective heat transfer coefficient increases from 2950 W/m2. oC to 3360 W/m2. oC by decreasing the average size of the carbon nanotubes from 76 nm to 54 nm.

Experimental investigation of thermo-physical properties, heat transfer, pumping power, entropy generation, and exergy efficiency of nanodiamond + Fe3O4/60:40% water-ethylene glycol hybrid nanofluid flow in a tube

The synthesis method of in-situ/chemical co-precipitation was implemented for the addition of Fe3O4 nanoparticles on the surface of nanodiamond (ND) nanoparticles, and it is characterized by using x-ray diffraction, transmission electron microscopy and the magnetic property was estimated from the vibrating sample magnetometer. The 60:40% water-ethylene glycol mixture is used as a base fluid for the preparation of ND-Fe3O4 hybrid nanofluids. Experimental techniques are used to measure the thermophysical properties at various particle volume loadings, and temperatures and the obtained data is validated with literature data. The heat transfer, friction factor, and pumping power are evaluated at particle volume loadings from 0.05% to 0.2% and in the Reynolds number range from 2105 to 8126. The concepts of the second law of thermodynamics are used to evaluate the thermal entropy generation, frictional entropy generation and exergy efficiency of the hybrid nanofluids. The thermal conductivity enhancements are 5.03% and 12.79%, whereas, the viscosity enhancements are 108% and 50.84% at particle loading of 0.2% at temperatures of 20 °C and 60 °C in comparison with base fluid. The Nusselt number is augmented to 15.65%; thermal entropy generation is reduced to 20%, frictional entropy generation is augmented to 272.48% and exergy efficiency is increased to 38.24% with a maximum penalty in friction factor of 1.128-times at 0.2% particle loading and a Reynolds number of 7502 against base fluid data. New equations are modelled to evaluate the thermophysical properties, Nusselt number, and friction factor.

Experimental investigation of thermo-physical properties of n-octadecane and n-eicosane

Reliable knowledge of phase change materials (PCM) thermo-physical properties is essential to model and design latent thermal energy storage (LTES) systems. This study aims to conduct a methodological measurement of thermo-physical properties, including latent enthalpy, isobaric specific heat, thermal conductivity and dynamic viscosity, of two n-alkanes, n-octadecane and n-eicosane. The enthalpy and isobaric specific heat of the materials are measured via differential scanning calorimetry (DSC) technique, using a µDSC evo7 from Setaram Instrumentation with a sample mass of 628.4 mg. The influence of the scanning rates, varying from 0.5 K/min to 0.025 K/min, in dynamic continuous mode within temperature range of 10–65 °C is investigated. The thermal conductivity and the dynamic viscosity are measured via Hot Disk TPS-2500S instrument and Brookfield rotational viscometer, respectively, up to 70 °C. The thermal analysis results via the µDSC show that the isothermal condition can be approached at a very low scanning rate, however at the cost of a higher noise level. A trade-off is observed for n-octadecane, achieving the lowest deviation of 0.7% in latent heat measurement at 0.05 K/min, as compared to the American Petroleum Table values. For n-eicosane, the lowest deviation of 1.2% is seen at the lowest scanning rate of 0.025 K/min. The thermal conductivity measured values show good agreements with a number of documented literature studies in the solid phase, within deviations of 2%. Larger deviations of 5–16% are found for the measurement in the liquid phase. The viscosity values also show a good agreement with the literature values with maximum deviations of 2.9% and 6.3%, with respect to the values of American Petroleum Tables, for n-octadecane and n-eicosane, respectively. The good agreements achieved in measurements establish the reliable thermo-physical properties contributing to the future simulations and designs.

Experimental evaluation of thermophysical properties of oil‐based titania nanofluids for medium temperature solar collectors

AbstractThermal oils are widely used as working fluids in the medium temperature heat transfer applications including concentrating solar thermal collectors. However, the weak thermal characteristics of these oils are major drawbacks in their successful application in the medium‐high temperature solar collectors. Fortunately, the emergence of nanotechnology has provided the opportunity to alter thermo‐physical properties of base fluids by adding small amount of sub‐micron size solid particles possessing better properties. This paper presents an experimental investigation of thermophysical properties of an oil‐based nanofluid to be used in the medium temperature solar collector for enhanced thermal energy transport. The colloidal suspensions were prepared by dispersing different weight fractions (0.25 wt.%, 0.5 wt.%, 0.75 wt.% and 1.0 wt.%) of Titania nanoparticles in Therminol‐55 oil using two‐step method. Shear mixing and high energy ultrasonication was employed to achieve uniform mixing and de‐agglomeration of the nanoparticles in order to enhance the stability of the colloidal suspensions. Thermophysical properties of the nanofluids were determined as a function of nanoparticles concentrations in the temperature range of 25 °C–130 °C. The experimental results demonstrated substantial improvement in thermal conductivity of the nano‐oils with an increase in nanoparticles loading which further enhanced at higher temperatures. Dynamic viscosity and effective density displayed a decreasing trend against rising temperature which indicate the effectiveness of these nanofluids for medium temperature heat supply. Nano‐oils with superior thermal properties can improve the performance of medium temperature solar thermal collectors.

Experimental investigation of thermo-physical properties of geminal dicationic ionic compounds for latent thermal energy storage

To enhance thermal stability of ionic compounds and increase thermal storage density, a series of geminal dicationic ionic compounds have been synthesized. The structures of these geminal dicationic ionic compounds were confirmed by 1H NMR and 13C NMR. Besides, thermal stability was determined by thermogravimetric analysis (TGA); melting point, heat of fusion and heat capacity were investigated by differential scanning calorimetry (DSC) for synthetic geminal dicationic ionic compounds. The effects of alkyl side-chain, the H atom at position 2 of the imidazolium ring, and anions on the thermal properties of the geminal dicationic ionic compounds were investigated. Hydrogen bonding in geminal dicationic ionic compounds was studied, in the case of C4(mim)2(Br)2, by single-crystal X-ray diffraction. The thermal analysis results indicate that geminal dicationic ionic compounds show excellent thermal stability. The decomposition temperatures of geminal dicationic ionic compounds can be up to 741.25 K, and the latent heat can reach 115.69 kJ kg−1. It is increased on average by 61.8% and 126.1%, respectively, as compared to alkyl chain ionic compounds (C4mim)Br. It can be expected that these geminal dicationic ionic compounds are suitable for thermal storage applications. Enhanced thermal storage density can thus be achieved by increasing the density and heat capacity. These values are higher than that of the monocationic ionic compounds. It can be expected that these geminal dicationic ionic compounds are suitable for thermal storage applications.

Experimental Investigation of Thermophysical Properties and Combustion Characteristics of Thickened Jet Fuel

ABSTRACT The thermophysical properties and combustion characteristics of PIB thickened jet fuel are investigated based upon both aims of expanding basic combustion theory (i.e., the coupled gas phase and liquid phase flows and heat transfer involving flame spread over liquid fuel) and potential practical applications (i.e., the oil additive in two-stroke gasoline engine and in-situ burning of leaked oils). The effects of PIB on the thermophysical parameters of jet fuel including density, flashpoint, viscosity and surface tension are experimentally measured. The logarithm of the dynamic viscosity varies linearly with the proportion of PIB, which is in good agreement with predictions. Then, the impact of PIB on fire safety of jet fuel is examined through flame spread and ignition experiments. The temperature evolution, flame spread rate, length and velocity of subsurface flow are quantitated and analyzed. The addition of PIB into jet fuel reduces the flame spread rate, but promotes the ignitability. The viscosity augment plays the principal role in hindering flame spreading over thickened jet fuel.

Experimental investigation of thermophysical properties of rhenium near its melting point

An experimental technique of millisecond electrical pulse heating was used for experimental investigation of Re near its melting point. Experimental data on the specific enthalpy and thermal expansion of rhenium at the temperatures close to the melting point were obtained during the experiments.

Experimental investigation of thermophysical properties of R718 based nanofluids at low temperatures

An extensive experimental investigation on the thermophysical properties of two different types of R718 (water) based nanofluid was performed for particle volume fractions (ϕ) ranging from 0.25–2.5%. R718 (water) is used as a secondary refrigerant in refrigeration systems; therefore, it is important to measure the variation in the thermophysical properties of R718 due to the addition of nanoparticles. The major highlight of the current work is the measurement of the thermophysical properties at a temperature as low as 278 K. Most of the studies available in the open literature are based on the thermophysical property measurement of nanofluids at elevated temperatures (above 293 K). In the present work, the thermophysical properties such as thermal conductivity, viscosity and density of the nanofluids were measured at a temperature varying from 5 to 25 °C (278-298 K) and were later compared with the existing theoretical models and previous experimental results. The specific heat capacity of Al2O3 and CuO based nanofluids was predicted and analysed using a theoretical model. The thermal conductivity of the nanofluid was measured by the Transient hot-wire method and the viscosity of the nanofluid was measured using a Cannon-Fenske viscometer. Copper oxide (CuO) and aluminium oxide (Al2O3) nanoparticles were chosen for the present investigation. The average particle diameter of CuO and Al2O3 nanoparticles was 30 nm. It was observed that the enhancement in thermal conductivity of nanofluids at low temperature (~278 K) is considerably lower than the enhancements at elevated temperatures. The viscosity measurements also revealed that the classical models can be successfully applied for predicting the viscosity of Al2O3 –R718 nanofluids at low particle volume fractions (ϕ < 0.5%).

High-temperature mechanical and thermodynamic properties of silicon carbide polytypes

Silicon carbide is widely used as ultra high-temperature ceramics, semiconductors, and pressure sensors with promising potentials for high-temperature, high-endurance, and radiation hardened applications. Daunting difficulties in experimental investigations of thermophysical properties hinder the better understanding of high-temperature material behaviors of silicon carbide. We present a comprehensive study of temperature-dependent mechanical and thermodynamic properties of SiC polytypes by first-principles methods. The obvious anisotropy of linear expansion and elasticity is found for 3C-SiC, while it is not distinct for other non-cubic SiC polytypes. Results show that the temperature dependences of mechanical properties exhibit the softening behavior, in which small linear reduction (∼4.4%) in Vickers hardness and shear modulus but large linear reduction (∼7.0%) in Young's modulus are detected. The heat-resistant properties of SiC polytypes are ranked as 3C-SiC < 4H-SiC < 6H-SiC < 15R-SiC < 2H-SiC. The present predictions are in favorable accord with available measured data in the literature.

Experimental investigation of thermophysical properties of eutectic Re–C at high temperatures

Using the previously described experimental setup for investigation of thermophysical properties of refractory materials under high pressures and temperatures a few experiments with samples of cast eutectic Re–C were carried out. The experimental technique was extended for millisecond electrical heating of the samples under the high static pressure of inert gas. First experimental data on the specific enthalpy, specific heat capacity and linear thermal expansion of ReC0.3 were obtained.

РАСЧЕТНО-ЭКСПЕРИМЕНТАЛЬНЫЕ ИССЛЕДОВАНИЯ ТЕПЛОФИЗИЧЕСКИХ СВОЙСТВ

РАСЧЕТНО-ЭКСПЕРИМЕНТАЛЬНЫЕ ИССЛЕДОВАНИЯ ТЕПЛОФИЗИЧЕСКИХ СВОЙСТВ