scholarly journals Investigation of the Thermodynamic Characteristics of the Ester Oil and R152a, R125, R134a and R123 Refrigerant Mixtures

2021 ◽  
Vol 13 (1) ◽  
pp. 14-24
Author(s):  
Robert Santa
Keyword(s):  
Heat Transfer ◽  
Thermodynamic Properties ◽  
Thermophysical Properties ◽  
Kinematic Viscosity ◽  
Thermodynamic Characteristics ◽  
Refrigeration System ◽  
Refrigerant Mixtures ◽  
System Changes ◽  
Different Temperatures ◽  
Hydraulic Processes

Abstract The presence of the lubricant POE 68 in the refrigeration system changes the thermophysical properties of the refrigerant, which significantly affects the heat transfer and the hydraulic processes. The purpose of this research is to investigate the thermodynamic properties of the R152a, R125, R134a and R123 refrigerant and POE 68 lubricant mixtures at different temperatures from 233,15 to 313,15 K. There have been investigated the values of the densities and kinematic viscosities of the mixtures at different concentrations (100%, 90%, 80%). Finally, it was found that, the density and kinematic viscosity of the R123/POE 68 mixture were most affected by the change of the concentration.

scholarly journals Copper Oxide Nanoparticles for Advanced Refrigerant Thermophysical Properties: Mathematical Modeling

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
S. A. Fadhilah ◽  
R. S. Marhamah ◽  
A. H. M. Izzat
Keyword(s):  
Mathematical Modeling ◽  
Heat Transfer ◽  
Copper Oxide ◽  
Heat Transfer Rate ◽  
Thermophysical Properties ◽  
Transfer Rate ◽  
Copper Oxide Nanoparticles ◽  
Working Fluid ◽  
Refrigeration System ◽  
R 134A

In modern days, refrigeration systems are important for industrial and domestic applications. The systems consume more electricity as compared to other appliances. The refrigeration systems have been investigated thoroughly in many ways to reduce the energy consumption. Hence, nanorefrigerant which is one kind of nanofluids has been introduced as a superior properties refrigerant that increased the heat transfer rate in the refrigeration system. Many types of materials could be used as the nanoparticles to be suspended into the conventional refrigerants. In this study, the effect of the suspended copper oxide (CuO) nanoparticles into the 1,1,1,2-tetrafluoroethane, R-134a is investigated by using mathematical modeling. The investigation includes the thermal conductivity, dynamic viscosity, and heat transfer rate of the nanorefrigerant in a tube of evaporator. The results show enhanced thermophysical properties of nanorefrigerant compared to the conventional refrigerant. These advanced thermophysical properties increased the heat transfer rate in the tube. The nanorefrigerant could be a potential working fluid to be used in the refrigeration system to increase the heat transfer characteristics and save the energy usage.

Numerical Modeling and Thermal Analysis of an Adsorption Refrigeration System

2015 ◽  
Vol 23 (04) ◽  
pp. 1550033 ◽  
Author(s):  
Anirban Sur ◽  
Randip K. Das
Keyword(s):  
Thermophysical Properties ◽  
Cooling System ◽  
Isosteric Heat ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Adsorption Refrigeration ◽  
Simulation Code ◽  
Mass Transfer Processes ◽  
Different Temperatures

The aim of this paper is to develop a complete, precise and simple numerical model based on the thermophysical properties of an adsorptive cooling system (using activated carbon–methanol pair), analyze and discuss the heat and mass transfer processes and identify the parameters which influence the system performance. In the design of adsorption refrigeration system, the characteristics of both adsorbate–adsorbent pairs and system operating conditions are very important. So in this model, different thermophysical properties of working pair such as, specific heat, density, isosteric heat of adsorption and desorption, and different temperatures of the system are considered. A simulation code, written in FORTRAN, is carried out. The performance of the system is assessed in terms of refrigeration effect and coefficient of performance (COP).

Effect of pre-swirl nozzle closure modes on unsteady flow and heat transfer characteristics in a pre-swirl system of aero-engine

2021 ◽  
pp. 095441002110191
Author(s):  
Gaowen Liu ◽  
Zhao Lei ◽  
Aqiang Lin ◽  
Qing Feng ◽  
Yan Chen
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Temperature Drop ◽  
Thermodynamic Characteristics ◽  
Circumferential Direction ◽  
Temperature Changes ◽  
Air Supply ◽  
Cooling Air

The pre-swirl system is of great importance for temperature drop and cooling air supply. This study aims to investigate the influencing mechanism of heat transfer, nonuniform thermodynamic characteristics, and cooling air supply sensitivity in a pre-swirl system by the application of the flow control method of the pre-swirl nozzle. A novel test rig was proposed to actively control the supplied cooling air mass flow rate by three adjustable pre-swirl nozzles. Then, the transient problem of the pre-swirl system was numerically conducted by comparison with 60°, 120°, and 180° rotating disk cavity cases, which were verified with the experiment results. Results show that the partial nozzle closure will aggravate the fluctuation of air supply mass flow rate and temperature. When three parts of nozzles are closed evenly at 120° in the circumferential direction, the maximum value of the nonuniformity coefficient of air supply mass flow rate changes to 3.1% and that of temperature changes to 0.25%. When six parts of nozzles are closed evenly at 60° in the circumferential direction, the maximum nonuniformity coefficient of air supply mass flow rate changes to 1.4% and that of temperature changes to 0.20%. However, different partial nozzle closure modes have little effect on the average air supply parameters. Closing 14.3% of the nozzle area will reduce the air supply mass flow rate by 9.9% and the average air supply temperature by about 1 K.

scholarly journals Kinetics and thermodynamic properties related to the drying of 'Cabacinha' pepper fruits

2016 ◽  
Vol 20 (2) ◽  
pp. 174-180 ◽  
Author(s):  
Hellismar W. da Silva ◽  
Renato S. Rodovalho ◽  
Marya F. Velasco ◽  
Camila F. Silva ◽  
Luís S. R. Vale
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Free Energy ◽  
Thermodynamic Properties ◽  
Gibbs Free Energy ◽  
Removal Rate ◽  
Effective Diffusion ◽  
Drying Time ◽  
Three Samples ◽  
Different Temperatures

ABSTRACT The objective of this study was to determine and model the drying kinetics of 'Cabacinha' pepper fruits at different temperatures of the drying air, as well as obtain the thermodynamic properties involved in the drying process of the product. Drying was carried out under controlled conductions of temperature (60, 70, 80, 90 and 100 °C) using three samples of 130 g of fruit, which were weighed periodically until constant mass. The experimental data were adjusted to different mathematical models often used in the representation of fruit drying. Effective diffusion coefficients, calculated from the mathematical model of liquid diffusion, were used to obtain activation energy, enthalpy, entropy and Gibbs free energy. The Midilli model showed the best fit to the experimental data of drying of 'Cabacinha' pepper fruits. The increase in drying temperature promoted an increase in water removal rate, effective diffusion coefficient and Gibbs free energy, besides a reduction in fruit drying time and in the values of entropy and enthalpy. The activation energy for the drying of pepper fruits was 36.09 kJ mol-1.

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