scholarly journals Numerical Investigation of the Effects of Window Height and Gas Thickness on Heat Transfer and Gas Flow in Double Pane Windows

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Sebahattin Unalan ◽  
Evrim Ozrahat
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Gas Flow ◽  
Ideal Gas ◽  
Surface Emissivity ◽  
Film Coatings ◽  
Venetian Blinds ◽  
Window Applications ◽  
Gap Width ◽  
Different Climates

Double pane window is an effective way to reduce the heat loss from windows in buildings. There are many studies on the thermal performance of these window applications for different parameters such as optimum gap width, suitable filling fluid and different applications such as film coatings on panes to obtain different surface emissivity values or placing venetian blinds inside the gap, etc. These investigations are mostly based on the laminar flow assumption inside the gas gap between the two panes for the same window height. In this research, effect of the window height and gap width on the gas flow in the gap and heat transfer over double pane for three cities of Turkey representing different climates were numerically investigated with turbulent flow and ideal gas assumptions inside the gap for air and argon. In the calculations, natural convection for pane surface facing indoors and forced convection for pane surface facing outdoors was assumed as boundary condition. The numerical results shown that also the window height such as gap width has an effect on the heat transfer and gas flow of the double pane window. Thereby, the window height should be taken into consideration for determining the optimum gap width in the double pane window applications.

Heat Transfer and Pressure Drop Through Nano-Fin Arrays in the Free-Molecular Flow Regime

2012 ◽  
Author(s):  
Michael James Martin
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Gas Flow ◽  
Ideal Gas ◽  
Molecular Flow ◽  
Ideal Gas Law ◽  
Transfer Equations ◽  
Flow Through ◽  
The One ◽  
The Ideal

Gas flow through arrays of rectangular nano-fins is modeled using the linearized free-molecular drag and heat transfer equations. These are combined with the one-dimensional equations for conservation of mass, momentum, and energy, and the ideal gas law, to find the governing equations for flow through the array. The results show that the pressure gradient, temperature, and local velocity of the gas are governed by coupled ordinary differential equations. The system of equations is solved for representative arrays of nano-fins to find the total heat transfer and pressure drop across a 1 cm chip.

Heat Transfer of Turbulent Gaseous Flow in Microtubes with Constant Wall Temperature

2021 ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Mohammad Faghri ◽  
Ichiro Ueno
Keyword(s):  
Heat Transfer ◽  
Incompressible Flow ◽  
Wall Temperature ◽  
Gas Flow ◽  
Ideal Gas ◽  
Constant Wall Temperature ◽  
Transfer Rates ◽  
Circulating Water ◽  
Enthalpy Difference ◽  
Total Temperature

Abstract Experiments were conducted with nitrogen gas flow in two microtubes with constant wall temperature, made of stainless-steel and copper with diameters of 524 and 537 micrometers, to measure the total temperature at the inlet and outlet and quantitively determine the heat transfer rates. The temperature differences between the inlet and the wall were maintained at 3, 5 and 10 K by circulating water around the inlet and the wall. The stagnation pressures were controlled such that the flow with atmospheric back pressure reached Reynolds numbers as high as 26000. To measure the total temperature, a polystyrene tube with thermally insulated exterior wall containing six plastic baffles, was attached to the outlet. Heat transfer rates were obtained from the gas enthalpy difference by using the pressures and the total temperatures measured at the inlet and outlet. Heat transfer rates were also compared with those obtained from the ideal gas enthalpy using the measured total temperatures and from the Nusselt number for incompressible flow. It was found that the measured total temperature at the microtube outlet was higher than the wall temperature. Also, the heat transfer rates calculated from the total temperature difference were higher than the values obtained from the incompressible flow theory.

Rarefied gas flow behavior in micro/nanochannels under specified wall heat flux

2015 ◽  
Vol 26 (08) ◽  
pp. 1550087 ◽  
Author(s):  
Mojtaba Balaj ◽  
Hassan Akhlaghi ◽  
Ehsan Roohi
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Flow Behavior ◽  
Direct Simulation Monte Carlo ◽  
Wall Heat Flux ◽  
Linear Distribution ◽  
Thermal Transpiration

In this paper, we investigate the effects of convective heat transfer on the argon gas flow through micro/nanochannels subject to uniform wall heat flux (UWH) boundary condition using the direct simulation Monte Carlo (DSMC) method. Both the hot wall (q wall > 0) and the cold wall (q wall < 0) cases are considered. We consider the effect of wall heat flux on the centerline pressure, velocity profile and mass flow rate through the channel in the slip regime. The effects of rarefaction, property variations and compressibility are considered. We show that UWH boundary condition leads to the thermal transpiration. Our investigations showed that this thermal transpiration enhances the heat transfer rate at the walls in the case of hot walls and decreases it where the walls are being cooled. We also show that the deviation of the centerline pressure distribution from the linear distribution depends on the direction of the wall heat flux.

Study of Temperature and Velocity Distribution of Rarefied Gas Flow in Micro-Nano Channels

2009 ◽  
Author(s):  
Hadi Ghezel Sofloo ◽  
Alireza Shams ◽  
Reza Ebrahimi
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Ideal Gas ◽  
Gas Density ◽  
Channel Size ◽  
Flow And Heat Transfer ◽  
Nonideal Gas ◽  
Gas Effect

This paper deals with simulation of transport phenomena in micro and nano pores. The number of cavities and the cavity radius were estimated by using Henry’s law for adsorption of Argon onto ZSM-5 and NaX zeolites. This work showed both of zeolites have pores with average size less than 1 nm. Then with using micro-nano channel assumption instead of micro-nano pores, gas flow and heat transfer were investigated. Subsonic nonideal gas flow and heat transfer for different Knudsen number are investigated numerically using the Direct Simulation Monte Carlo method modified with a consistent Boltzamnn algorithm. The collision rate is also modified based on the Enskog theory for dense gas. It is shown that nonideal gas effect becomes significant when the gas becomes so dense that the ideal gas assumption breaks down. The results also show that the nonideal gas effect is dependent not only on the gas density, but also the channel size. A higher gas density and a smaller channel size lead to a more significant nonideal gas effect. The nonideal gas effect also causes lower skin friction coefficients and different heat transfer flux distributions at the wall surface.

Heat Transfer and Pressure Drop Through Nano-Fin Arrays in the Free-Molecular Flow Regime

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Michael James Martin
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Gas Flow ◽  
Ideal Gas ◽  
Molecular Flow ◽  
Ideal Gas Law ◽  
Transfer Equations ◽  
Flow Through ◽  
The One ◽  
The Ideal

Gas flow through arrays of rectangular nanofins is modeled using the linearized free-molecular drag and heat transfer equations. These are combined with the one-dimensional equations for conservation of mass, momentum, and energy, and the ideal gas law, to find the governing equations for flow through the array. The results show that the pressure gradient, temperature, and local velocity of the gas are governed by coupled ordinary differential equations. The system of equations is solved for representative arrays of nanofins to find the total heat transfer and pressure drop across a 1 cm chip.

Growth and decay of acceleration waves in non-ideal gas flow with radiative heat transfer

2012 ◽  
Vol 2 (3) ◽  
Author(s):  
Lal Singh ◽  
Raghwendra Singh ◽  
Subedar Ram
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Gas Flow ◽  
Radiative Heat ◽  
Critical Time ◽  
Ideal Gas ◽  
Initial Amplitude ◽  
Linear Solution ◽  
Linear Behavior ◽  
Acceleration Waves

AbstractThe present paper is concerned with the study of the propagation of acceleration waves along the characteristic path in a non-ideal gas flow with effect of radiative heat transfer. It is shown that a linear solution in the characteristic plane can exhibit non-linear behavior in the physical plane. It is also investigated as to how the radiative heat transfer under the optically thin limit will affect the formation of shock in planer, cylindrical and spherically symmetric flows. We conclude that there exists critical amplitude such that any compressive waves with initial amplitude greater than the critical one terminate into shock waves while an initial amplitude less than the critical one results in the decay of the disturbance. The critical time for shock formation has been computed. In this paper we also compare/contrast the nature of solution in ideal and non ideal gas flows.

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