scholarly journals Interactive Graphic Depiction Of Working Fluid Thermal Properties Using Spreadsheets

2020 ◽  
Author(s):  
Michael Maixner
Keyword(s):  
Thermal Properties ◽  
Working Fluid ◽  
Interactive Graphic ◽  
Graphic Depiction

Computation of Thermodynamic Properties of Carbon Dioxide in the Range 0–750 Deg C

1970 ◽  
Vol 92 (3) ◽  
pp. 301-309 ◽  
Author(s):  
G. Angelino ◽  
E. Macchi
Keyword(s):  
Carbon Dioxide ◽  
Thermal Properties ◽  
High Temperature ◽  
Thermodynamic Properties ◽  
Thermodynamic Functions ◽  
Critical Region ◽  
Density Measurement ◽  
Working Fluid ◽  
Power Cycles ◽  
Wide Range

The computation of power cycles employing carbon dioxide as working fluid and extending down to the critical region requires the knowledge of the thermodynamic properties of CO2 within a wide range of pressures and temperatures. Available data are recognized to be insufficient or insufficiently accurate chiefly in the vicinity of the critical dome. Newly published density and specific heat measurements are employed to compute thermodynamic functions at temperatures between 0 and 50 deg C, where the need of better data is more urgent. Methods for the computation of thermal properties from density measurement in the low and in the high temperature range are presented and discussed. Results are reported of the computation of entropy and enthalpy of CO2 in the range 150–750 deg C and 40–600 atm. The probable precision of the tables is inferred from an error analysis based on the generation, by means of a computer program of a set of pseudoexperimental points which, treated as actual measurements, yield useful information about the accuracy of the calculation procedure.

Investigation of Thermal Properties in Nanofluids for Thermal Energy Storage Applications

2013 ◽  
Author(s):  
Aitor Zabalegui ◽  
Bernadette Tong ◽  
Hohyun Lee
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Energy Storage ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Working Fluid ◽  
Traditional Theory ◽  
Energy Storage Applications ◽  
Particle Addition

Phase change materials (PCMs) are promising for thermal energy storage applications, but low thermal conductivity limits their heat exchange rate with a working fluid. The nanofluid approach has been established as a method of thermal conductivity enhancement, but particle addition may have an adverse effect on specific energy storage capacity. Latent heat reduction beyond traditional theory has been observed experimentally for carbon nanotubes dispersed in paraffin wax. Nanofluid latent heat and effective thermal conductivity were analyzed to investigate the effects of particle addition on thermal properties affecting PCM energy storage performance. It is shown that particle diameter significantly impacts nanofluid latent heat, with smaller particles generating greater degrees of reduction, but has a negligible effect on thermal conductivity. A method to approximate nanofluid latent heat of fusion is presented, considering the diameter-dependent reduction observed.

scholarly journals Estimation of Cement Thermal Properties through the Three-Phase Model with Application to Geothermal Wells

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2839 ◽  
Author(s):  
Adonis Ichim ◽  
Catalin Teodoriu ◽  
Gioia Falcone
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Working Fluid ◽  
Geothermal Systems ◽  
Well Performance ◽  
Three Phase ◽  
Geothermal Wells ◽  
Ancient Times ◽  
Efficient Heat Transfer ◽  
Selection Of

Geothermal energy has been used by mankind since ancient times. Given the limited geographical distribution of the most favorable resources, exploration efforts have more recently focused on unconventional geothermal systems targeting greater depths to reach sufficient temperatures. In these systems, geothermal well performance relies on efficient heat transfer between the working fluid, which is pumped from surface, and the underground rock. Most of the wells designed for such environments require that the casing strings used throughout the well construction process be cemented in place. The overall heat transfer around the wellbore may be optimized through accurate selection of cement recipes. This paper presents the application of a three-phase analytical model to estimate the cement thermal properties. The results show that cement recipes can be designed to enhance or minimize heat transfer around wellbore, extending the application of geothermal exploitation.

scholarly journals Experimental Analysis PVP Coated Silver Nanofluid Properties for Application in Photovoltaic/Thermal (PVT) Collectors

2020 ◽  
Vol 1 (3) ◽  
pp. 28-40
Author(s):  
A. Naderi ◽  
Gazori H. ◽  
M. Bozegi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Base Fluid ◽  
Fossil Fuels ◽  
Working Fluid ◽  
Solar Collectors ◽  
Step Method ◽  
Energy Technologies ◽  
Pv Module ◽  
Utility Systems

Nowadays, supplying energy for the global population has turned into a prominent issue for countries engendering the consumption of huge amounts of fossil fuels which leads to some serious environmental problems. Among the renewable energy technologies, solar collectors can play major role to improve the efficiency, in air conditioning utility systems by minimum pollution. In photovoltaic/thermal (PVT) solar collectors, which are currently considered as the most advanced type to produce electricity and heat simultaneously, working fluid absorbs Energy from photovoltaic (PV) module engendering to decrease temperature of PV module and increase the electricity efficiency and also provide permissible amount of heat for other residential applications. Meanwhile, utilizing nanofluid as the working fluid in collector, regarding that the nanofluid has enhanced thermal properties relative to the base fluid, leads to a higher collector efficiency. In this research, PVP coated silver nanofluid was prepared in three volume concentration being 250, 500 and 1000 ppm by two-step method. To assess the stability of nanofluid the zeta potential is calculated which is obtained -41.6 V. Also, the prominent thermal properties of the nanofluid were analyzed regarding PVT solar collector applications. According to the results, thermal conductivity of the PVP coated silver nanofluid, improves the properties of base fluid, to the extent that thermal conductivity coefficient grows up 50% in some temperatures and increased from 0.594 for base fluid to 1.098 W/mK by escalation of concentration to 1000 ppm. Thus, PVP coated silver nanofluid can be deemed as the vital working fluid to improve the performance of PVT solar collectors.

Phase Change Thermal Diode Using Al2O3-Cu/Water Hybrid Nanofluids for Thermal Rectification Enhancement

2020 ◽  
Author(s):  
M. Y. Wong ◽  
C. Y. Tso ◽  
T. C. Ho
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Phase Change ◽  
Storage Systems ◽  
Thermal Storage ◽  
Solar Thermal ◽  
Working Fluid ◽  
Hybrid Nanofluid ◽  
Thermal Rectification ◽  
Hybrid Nanofluids

Abstract A thermal diode, a device to manipulate the heat flow in different directions, is useful in various thermal systems, such as solar thermal storage systems. It is noted that the performance of phase change thermal diodes shows the highest thermal rectification performances in the literature. The performances of the phase change thermal diode can be further improved by utilizing a working fluid with enhanced thermal properties. Since hybrid nanofluids are proven to have better thermal properties than the base fluid (i.e. water), in this study, a thermal diode using Al2O3-Cu/water hybrid nanofluid is fabricated and tested to investigate the feasibility of using hybrid nanofluid to enhance the performance of the thermal diode. The heat transfer and thermal rectification performances of the thermal diode using Al2O3-Cu/water hybrid nanofluid are compared experimentally, to a thermal diode using water. The effect of temperature on the heat transfer and thermal rectification performances of the thermal diode is also examined. The results indicate that the effective thermal conductivity in the forward direction and the diodicity of the thermal diode using Al2O3-Cu/water hybrid nanofluid are improved by 42.4% and 30.8%, respectively, compared to that of the thermal diode using water. The findings not only reveal a new direction for future research in enhancement of the thermal rectification performance of the phase change thermal diode but also provide an alternative research path for improving the performance of existing solar thermal storage systems.

scholarly journals Optimizing the Design of a Vertical Ground Heat Exchanger: Measurement of the Thermal Properties of Bentonite-Based Grout and Numerical Analysis

2018 ◽  
Vol 10 (8) ◽  
pp. 2664
Author(s):  
Daehoon Kim ◽  
Seokhoon Oh
Keyword(s):  
Thermal Properties ◽  
High Density Polyethylene ◽  
Fluid Velocity ◽  
Operation Time ◽  
Silica Sand ◽  
Working Fluid ◽  
Hdpe Pipe ◽  
Intermittent Operation ◽  
Vertical Ground ◽  
Off Time

We prepared bentonite-based grouts for use in the construction of vertical ground heat exchangers (GHEs) using various proportions of silica sand as an additive, and measured the thermal conductivity (TC) and specific heat capacity (SHC) of the grouts under saturated conditions. Furthermore, we performed numerical simulations using the measured thermal properties to investigate the effects of grout-SHCs, the length of the high-density polyethylene (HDPE) pipe, the velocity of the working fluid, and the operation time and off-time during intermittent operation on performance. Experimentally, the grout TCs and SHCs were in the ranges 0.728–1.127 W/(mK) and 2519–3743 J/(kgK), respectively. As the proportions of bentonite and silica sand increased, the TC rose and the SHC fell. Simulation showed that, during intermittent operation, not only a high grout TC but also a high SHC improved GHE performance. Also, during both continuous and intermittent operation, GHE performance improved as the working fluid velocity increased, and there was a critical working fluid velocity that greatly affected the performance of the vertical GHE, regardless of operation mode, high-density polyethylene (HDPE) pipe length, or grout thermal properties; this value was 0.3 m/s. Finally, during intermittent operation, depending on the operation time and off-time, critical periods were evident when the ground temperature had been almost completely restored and any beneficial effect of intermittent operation had almost disappeared.

scholarly journals ОПРЕДЕЛЕНИЕ ГРАНИЧНЫХ УСЛОВИЙ ДЛЯ РАСЧЁТА ТЕРМОНАПРЯЖЕННОГО СОСТОЯНИЯ ПОРШНЯ

2019 ◽  
pp. 39-47
Author(s):  
Ван Зионг Нгуен ◽  
Александр Витальевич Белогуб
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Heat Exchange ◽  
Boundary Conditions ◽  
Initial Conditions ◽  
Internal Heat ◽  
Heat Removal ◽  
Temperature Fields ◽  
Working Fluid ◽  
Working Process

The paper deals with the study of the influence of the working process parameters of the two-stroke opposed piston engine like D100 (20.7/2×25.4), especially the heat exchange between the working substance and the wall of the combustion chamber (CC) – cylinder and pistons on temperature and stress-strain state of the piston. To make an estimation of the effect of a working process on the boundary condition we considered the internal heat balance and specific features of gas dynamic loading of main parts of the cylinder-piston group. To calculate the temperature fields, the actual boundary conditions of non-stationary thermal loading were replaced with the equivalent steady-state ones, obtained from the condition that the amount of heat perceived by the piston surface in real and conditionally equivalent processes are equal. Equivalent parameters of heat transfer are calculated by the condition of conservation of the amount of heat passing through the walls of the CS. It was performed the validation of the calculation of equivalent heat exchange parameters. It is shown that in case of an error in specifying the initial conditions, for example, temperature per 100K, the temperature of the piston CC surface may change by 5K in the first 5 operating cycles. It is shown that the developed model of the workflow can be adjusted according to the available experimental data and used to model the boundary conditions. The authors made corrections to the dependence obtained by prof. Rosenblit, to determine the current heat transfer coefficient from the working fluid to the walls of the CC by the total heat removal for the cycle, equal to 20%. It was obtained the average coefficient of heat transfers from the working fluid to the piston and the temperature of the cycle for the nominal mode, which are 3500 W/(m2•K) and 835 K respectively. It was carried out the simulation of the thermal properties of the gap between the piston ring and the groove filled with combustion products. It is shown that the conditions of heat transfer through annular grooves and rings require clarification in modeling, which is associated with the conditions of heat transfer in the gaps, and the gap can be replaced by a gasket with appropriate thermal properties.

The thermal properties of some amine tetraphenylboron salts8-Quinolinol and its derivatives

1960 ◽  
Vol 23 ◽  
pp. 332-336 ◽  
Author(s):  
W WENDLANDT ◽  
J VANTASSEL ◽  
G ROBERTHORTON
Keyword(s):  
Thermal Properties
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