Questions tagged [convection]
51 questions
5
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How to determine if mass transfer convection is natural or forced?
I know that forced convection requires some external bulk flow, but is there an equation to determine which form of Convection is dominant? I looked around and found the Richardson number $\mathrm{Ri}=\frac{\mathrm{Gr}}{\mathrm{Re}^2}$ but I don't…
user4785
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4
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1 answer
Heat Transfer coefficient calculation for hot air flow inside rectangular duct
I am working on modeling of air-heater component. A simplified representation of system is as follows:
Cold air flow enters steel duct at one end. Inside duct is Calrod heating element shaped as ellipse. Follwing heat transfer occur…
user1768201
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3
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What is the difference between the wave equation and the advection equation?
I am trying to understand what is the difference between the wave equation ad the advection equation? Bot the equation seems to move a quantity. While in literature it is said that the advection equation is the simpler of the two I don't see how the…
GRANZER
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2
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Convective heat transfer coefficient in finite difference method boundary conditions
Suppose there is a cubic material with an internal heat source ($\Delta q / \Delta t =$ Constant), and is immersed in a sufficiently large amount of water. Now I would like to use finite difference method to simulate the steady state temperature…
Xiangxi Meng
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2
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1 answer
Heat transfer characteristics in narrow rectangular channel
Please take a look at following figure:
System considered is a narrow rectangular channel of 2.5 mm depth (W x L is 60 mm x 150 mm). Since channel has low depth, it can be considered as mini-channel. Bottom surface is hot and at $~ 100\,^o…
user1768201
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2
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1 answer
Can I neglect kinetic energy when modeling convective heat transfer for viscous, low mach airflow? Why or why not?
I'm looking at convective heat transfer for air flow over a solid at Ma=0.2. At this speed, it is plausible to model the flow as incompressible because of small density variations in the air. Normally, when modeling compressible flow, we include…
Paul
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Can a steel plate reach -20°C due to radiative cooling when the ambient temperature is 2°C?
Conditions: there is a steel plate insulated at the bottom and facing the clear night sky, the ambient air temperature is 2°C, the cosmic microwave background radiation is 3K, and the convective heat transfer coefficient is 10 . My job is to…
Miya
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1 answer
Why heat transfer happens only via conduction in this case?
Why heat transfer between a heated flat plate and a fluid happens via conduction only and not convection, when the fluid is present below it?
Consider a plate under which a fluid is present and it extends to infinity in the vertical direction. Let's…
Harshit Rajput
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Can the Whitaker Nusselt number correlation be used for a hot sphere in convection with cool air?
The Whitaker Nusselt number correlation (equation 4 here if you don't know it) seems to not be applicable for when the viscosity of the fluid gets higher away from the surface, but it seems to get used in problems where we have a hot sphere in…
William G Martin
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In this scenario, if I continue to increase the length of heat exchanger how will the temperatures change?
Consider a counter flow double pipe heat exchanger inside which the cold fluid enters at 20 degrees Celsius and hot fluid enters at 100 degrees Celsius. Initially the length of the heat exchanger is L1 and the temperature profiles are shown in the…
Harshit Rajput
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1
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2 answers
How to visualise/measure airflow in sauna?
I'd like to visualise/measure the flow of air in sauna to optimise the ventilation.
Is there a way to colour the air (non-toxic!!!) so I may watch the flow?
Or is there any other accessible technology applicable in the home conditions?
EDIT:…
Honza Zidek
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Errors obtained in the numerical solution of the 1D convection-diffusion equation
I have been trying to solve the 1D convection-diffusion equation
In implementing the above, I have tried to follow closely the method described here:…
gary105
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1
vote
2 answers
Analytical solution for the 1D convection-diffusion equation
The Ogata and Banks analytical solution of the convection-diffusion equation for a continuous source of infinite duration and a 1D domain:
where C [mol/L] is the concentration, x [m] is the distance, R is the retardation factor, D [m2/day] is the…
gary105
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1
vote
1 answer
surface temperature due to constant heat flux
Imagine a hollow cylinder with the outside surface exposed to air (convection). If there is a constant heat flux on the inside surface how would I calculate both the inside and outside surface temperature?
mani shekar
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1
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Heat Conduction/Convection Along discontinuous tube
I have a question regarding heat conduction/convection. I have a metallic tube over which a rope heater is wound, supplying power. A glass tube and a 2nd metallic tube lies at the exit of the first tube. The inlet thermocouple is placed at the inlet…
arodor
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