scholarly journals Influence of the color of the refrigeration body on its thermal parameters

2018 ◽  
Vol 19 (12) ◽  
pp. 589-592
Author(s):  
Karolina Perz ◽  
Łukasz Mamoński ◽  
Aleksandra Rewolińska
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Expanded Polystyrene ◽  
The Body ◽  
Thermal Parameters ◽  
Body Colour ◽  
The Impact

The article discusses the issue of the impact of the color of refrigeration bodies on the thermal parameters of insulation. The tests of the density of heat flux flowing through metal claddings were carried out, and then their heat transfer coefficient was calculated on their basis. In the further part of the article, the influence of the body colour on the thermal conductivity of a three-layer wall consisting of an insulating core (expanded polystyrene) and two external claddings of different colour was analyzed. On the basis of the obtained results, it can be stated that the colour of the body affects the value of heat that passes through it.

Nanoparticle aggregation kinematics on the quadratic convective magnetohydrodynamic flow of nanomaterial past an inclined flat plate with sensitivity analysis

2021 ◽  
pp. 095440892110562
Author(s):  
AS Sabu ◽  
Joby Mackolil ◽  
B Mahanthesh ◽  
Alphonsa Mathew
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Sensitivity Analysis ◽  
Heat Transfer Coefficient ◽  
Heat Source ◽  
Transfer Coefficient ◽  
Flat Plate ◽  
Inclined Plate ◽  
The Impact ◽  
The Heat Transfer Coefficient

The study focuses on the aggregation kinematics in the quadratic convective magneto-hydrodynamics of ethylene glycol-titania ([Formula: see text]) nanofluid flowing through an inclined flat plate. The modified Krieger-Dougherty and Maxwell-Bruggeman models are used for the effective viscosity and thermal conductivity to account for the aggregation aspect. The effects of an exponential space-dependent heat source and thermal radiation are incorporated. The impact of pertinent parameters on the heat transfer coefficient is explored by using the Response Surface Methodology and Sensitivity Analysis. The effects of several parameters on the skin friction and heat transfer coefficient at the plate are displayed via surface graphs. The velocity and thermal profiles are compared for two physical scenarios: flow over a vertical plate and flow over an inclined plate. The nonlinear problem is solved using the Runge–Kutta-based shooting technique. It was found that the velocity profile significantly decreased as the inclination of the plate increased on the other hand the temperature profile improved. The heat transfer coefficient decreased due to the increase in the Hartmann number. The exponential heat source has a decreasing effect on the heat flux and the angle of inclination is more sensitive to the heat transfer coefficient than other variables. Further, when radiation is incremented, the sensitivity of the heat flux toward the inclination angle augments at the rate 0.5094% and the sensitivity toward the exponential heat source augments at the rate 0.0925%. In addition, 41.1388% decrement in wall shear stress is observed when the plate inclination is incremented from [Formula: see text] to [Formula: see text].

scholarly journals Numerical study of heat transfer in 90° bend tube by AI2O3 nano fluids using fluid injection

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hadi Mahdizadeh ◽  
Nor Mariah Adam
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Volume Fraction ◽  
Fluid Injection ◽  
Content Type ◽  
Nano Fluid ◽  
The Impact

Purpose This paper aims to investigate increasing heat transfer in bend tube 90° by fluid injection using nano fluid flow that was performed by expending varying Reynolds number. This paper studies the increased heat transfer in the bent tube that used some parameters to examine the effects of volume fraction, nanoparticle diameter, fluid injection, Reynolds number on heat transfer and flow in a bend pipe. Design/methodology/approach Designing curved tubes increases the thermal conductivity amount between fluid and wall. It is used the finite volume method and simple algorithms to solve the conservation equations of mass, momentum and energy. The results showed that the nanoparticles used in bent tube transfusion increase the heat transfer performance by increasing the volume fraction; it has a direct impact on enhancing the heat transfer coefficient. Findings Heat transfer coefficient enhanced 1.5% when volume fraction increased from 2 % to 6%, the. It is due to the impact of nanoparticles on the thermal conductivity of the fluid. The fluid is injected into the boundary layer flow due to jamming that enhances heat transfer. Curved lines used create a centrifugal force due to the bending and lack of development that increase the heat transfer. Originality/value This study has investigated the effect of injection of water into a 90° bend before and after the bend. Specific objectives are to analyze effect of injection on heat transfer of bend tube and pressure drop, evaluate best performance of mixing injection and bend in different positions and analyze effect of nano fluid volume fraction on injection.

Study on Methods of Calculating Heat Transfer Coefficient of Supercritical Water With Grey Theory

2010 ◽  
Author(s):  
Xiaozhuang Liu ◽  
Tao Zhou ◽  
Zhenyang Li ◽  
Handing Wang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Multiple Regression ◽  
Supercritical Water ◽  
Grey Model ◽  
Grey Theory ◽  
System Pressure ◽  
The Impact

Heat transfer coefficient is an important feature factor in describing SCWR. Using grey theory and multiple regression, writing code with MATLAB with considering temperature and enthalpy of coolant, heat flux and system pressure, establish GM(1.1), GM(1,3) and multiple regression models of heat transfer coefficient of supercritical water. analyzing the impact of temperature and enthalpy of coolant, heat flux, pressure on the changes of heat transfer coefficient in SCWR. Grey model generally summarize the experimental data. and its calculation results are compared with the results of regression model, which shows grey model can forecast the changes of heat transfer coefficient better, provides new methods of fitting and forecasting heat transfer coefficient of supercritical water.

Thermal performance of fully wet longitudinal porous fin with temperature-dependent thermal conductivity, surface emissivity and heat transfer coefficient

2019 ◽  
Vol 16 (4) ◽  
pp. 749-764 ◽  
Author(s):  
G. Sowmya ◽  
B.J. Gireesha ◽  
O.D. Makinde
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Surface Emissivity ◽  
Content Type ◽  
Porous Fin ◽  
Convective Parameter ◽  
The Impact ◽  
Simultaneous Variation

Purpose The purpose of this paper is to study the thermal behaviour of a fully wet porous fin of longitudinal profile. The significance of radiative and convective heat transfer has been scrutinised along with the simultaneous variation of surface emissivity, heat transfer coefficient and thermal conductivity with temperature. The emissivity of the surface and the thermal conductivity are considered as linear functions of the local temperature between fin and the ambient. Darcy’s model was considered to formulate the heat transfer equation. According to this, the porous fin permits the flow to penetrate through it and solid–fluid interaction occurs. Design/methodology/approach Runge–Kutta–Fehlberg fourth–fifth-order method has been used to solve the reduced non-dimensionalized ordinary differential equation involving highly nonlinear terms. Findings The impact of pertinent parameters, such as convective parameter, radiative parameter, conductivity parameter, emissivity parameter, wet porous parameter, etc., on the temperature profiles were elaborated mathematically with the plotted graphs. The heat transfer from the fin enhances with the rise in convective parameter. Originality/value The wet nature of the fin enhances heat transfer and in many practical applications the parameters, such as thermal conductivity, heat transfer coefficient as well as surface emissivity, vary with temperature. Hence, the main objective of the current study is to depict the significance of simultaneous variation in surface emissivity, heat transfer coefficient and thermal conductivity with respect to temperature under natural convection and radiation condition in a totally wetted longitudinal porous fin.

Convective heat transfer measured directly with a heat flux sensor

1990 ◽  
Vol 68 (3) ◽  
pp. 1275-1281 ◽  
Author(s):  
U. Danielsson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
The Body ◽  
Heat Flux Sensor ◽  
Calibration Constant

A heat flux disk has been developed that directly measures the convective heat transfer in W/m2. When the sensor is calibrated on an aluminum cylinder, the calibration constant obtained is greatest in still air. As air movement increases, the calibration constant is reduced with increasing convective heat transfer coefficient, 0.5%.W-1.m2.K. The influence of wind on the calibration value is greatly reduced when the sensor is attached to a surface with lower thermal conductivity. The local convective heat transfer coefficient (hc) of the human body was measured. The leg acts in a manner similar to that of a cylinder, with the highest hc value at the front facing the wind and the lowest approximately 90 degrees from the wind, and in the wake a value is obtained that is close to the average hc value of the leg. When hc is measured at several angles and positions all over the body, the results indicate that the body acts approximately as a cylinder with a hc value related to the wind speed as hc = 8.6.v0.6 W.m-2.K-1, where v is velocity.

Advanced Thermosyphon Cooling With Nanoporous Structured Mini Channel Evaporators

2009 ◽  
Author(s):  
Justin N. W. Chiu ◽  
Rahmatollah Khodabandeh ◽  
Richard Furberg
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Smooth Surface ◽  
Surface Structures ◽  
Nanoporous Structure ◽  
Reduced Pressure ◽  
Structured Surfaces ◽  
The Impact

Attention has been given to enhance boiling surfaces in order to decrease the temperature difference and to increase heat transfer coefficient. Structured surfaces may provide both surface enlargement and artificial nucleation sites, thus ameliorate the heat transfer coefficient. The goal of the present experimental work is to analyze the influence on heat transfer coefficient (HTC) of enhanced surface structures coated on mini channel heat exchanger working in a closed loop thermosyphon system. Experimental tests were carried out with three types of surface enhanced mini channel evaporators: smooth surface, threaded structure and nanoporous coating. The evaporators are single channel half circularly shaped, adapted for filming purpose, measuring 30mm in length and 3mm in diameter. Surface areas of channels are 1.41cm2. Experiments were conducted in refrigerant 134a at 4.87bar (reduced pressure pr = 0.12) and at heat fluxes ranging from 0.7W/cm2 to 63.8W/cm2. A high speed video camera was used for visualization of the two-phase flow in the evaporator channel. It is shown that threaded surface provides the highest heat transfer coefficient (HTC) from no load to heat flux of 7.1W/cm2, the nanoporous structure shows the highest performance between 7.1W/cm2 and 49.6W/cm2, and the smooth surface channel exhibits the best HTC from 49.6W/cm2 and higher. In this paper, the influences of heat flux and surface structures on HTC are discussed, and the impact of refrigerant flow regimes on heat transfer performance is also highlighted.

Development of a New Correlation and Post Processing of Heat Transfer Coefficient and Pressure Drop of Functionalized COOH MWCNT Nanofluid by Artificial Neural Network

2018 ◽  
Vol 14 (2) ◽  
pp. 104-112 ◽  
Author(s):  
Mohammad Hemmat Esfe ◽  
Somchai Wongwises ◽  
Saeed Esfandeh ◽  
Ali Alirezaie
Keyword(s):  
Neural Network ◽  
Heat Transfer ◽  
Thermal Conductivity ◽  
Artificial Neural Network ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Regression Coefficient ◽  
New Correlation ◽  
The Neural Network

Background: Because of nanofluids applications in improvement of heat transfer rate in heating and cooling systems, many researchers have conducted various experiments to investigate nanofluid's characteristics more accurate. Thermal conductivity, electrical conductivity, and heat transfer are examples of these characteristics. Method: This paper presents a modeling and validation method of heat transfer coefficient and pressure drop of functionalized aqueous COOH MWCNT nanofluids by artificial neural network and proposing a new correlation. In the current experiment, the ANN input data has included the volume fraction and the Reynolds number and heat transfer coefficient and pressure drop considered as ANN outputs. Results: Comparing modeling results with proposed correlation proves that the empirical correlation is not able to accurately predict the experimental output results, and this is performed with a lot more accuracy by the neural network. The regression coefficient of neural network outputs was equal to 99.94% and 99.84%, respectively, for the data of relative heat transfer coefficient and relative pressure drop. The regression coefficient for the provided equation was also equal to 97.02% and 77.90%, respectively, for these two parameters, which indicates this equation operates much less precisely than the neural network. Conclusion: So, relative heat transfer coefficient and pressure drop of nanofluids can also be modeled and estimated by the neural network, in addition to the modeling of nanofluid’s thermal conductivity and viscosity executed by different scholars via neural networks.

Sign in / Sign up

Export Citation Format

Share Document