# Search results

1. ### Heat Transfer on a windshield

in this case its a simple, conduction + Convection problem. if u have a respectable Heat transfer book u can get an equation that defines the heat transfer from an inclined plane to the atmosphere, and conduction is simple. and u don't have to take a semi-infinite solid, because the equations...
2. ### Heat Transfer on a windshield

at first i thought like u did, that he wanted to heat the whole car, but semi-infinite solid really puts the dots on the letters, doesn't it !
3. ### Heat Transfer on a windshield

wait a minute, isn't it a question of only melting the ice on the windshiled? it can't be inside heating and where he had taken it as a semi-infinite solid !
4. ### Heat Transfer on a windshield

i second on drendank, and the glass can be accounted for as conduction in the thermal circuit.
5. ### Convection heat transfer, Fluent vs Calculations

wow, i'm getting 2000W !! very close to the 1713 i got by hand !! i think i'm pretty close now..i'll take that as my answer. thnx man
6. ### Convection heat transfer, Fluent vs Calculations

now i've realized something. when i put thickness to the water plate it changes temperature, while if i put a no thickness plate it maintains its temperature, propably that was the difference between the heat transfer fluxes. i've tried the method u told me, unfortunately i can't trust my hand...
7. ### Convection heat transfer, Fluent vs Calculations

if water thickness is not that important,(which i know) but how did it change the answer from 600W-->5900W? i will remesh my volume, mayb try one without a boundary layer even though i think bdry layer is very important in such natural convection. btw. do u believe that the empirical equation...
8. ### Convection heat transfer, Fluent vs Calculations

i already did that. i installed boundary layers next to the area close to the pool but how do u check mesh convergence? Btw, before on the plate i put plate thickness of 2m which is the depth of the pool. in the next trial which i'm doing now i removed the thickness, the heat transfer rocketed...
9. ### Convection heat transfer, Fluent vs Calculations

well solution convergence. the equation geometry? the setting is normal convection over a horizontal plate. there's no integration and the like, just 1 simple derived formula. My setting is a pool inside a closed fixed temp room. i've taken the pool as a plate to be able to find the Heat...
10. ### Convection heat transfer, Fluent vs Calculations

the solution on Fluent is stable, i have 410000+ meshed volumes, the pc would explode if i add more. the answer is constantly 600W ! and i think it has reached convergence.
11. ### Convection heat transfer, Fluent vs Calculations

Hi all I've been calculating heat convection off a horizontal heated plate to still cool air around it. Since the plate has a size of 50m2 the GrPr number is turbulent i there's no equation in my book to calculate heat transfer by convection for GrPr > 10^11, so i used the equation of GrPr at...
12. ### Is it possible to find the combustion pressure on any ICE?

btw i would need the empirical chemical formula of the 110 octane racing fuel and NO2 amount (percentages, or moles...)
13. ### Is it possible to find the combustion pressure on any ICE?

i'll work on the chemistry equation and see how to set it up. meanwhile i don't know if a formula like that could work, mayb u should check it out: Power= Force*distance/time distance is the distance travelled by the piston in an amount of time (which u can get from RPM)..and u have the power...

oh ok ! :)
15. ### How would you determine the Lift(thrust) force of a Helicopter in hover

definitely interested in that:)
16. ### How would you determine the Lift(thrust) force of a Helicopter in hover

i think u can find the maximum power yield by zeroing the velocity at the exit
17. ### How would you determine the Lift(thrust) force of a Helicopter in hover

i wonder if bernouilli's equation can be put to use in this case. i know that it can be used when there is wind driving a wind turbine. it should work here
18. ### Heat Exchanger problem

ok follow this up, i hope ur familiar with the Staunton number: here goes Eq.1: St*Pr=f/, f is the friction coefficient defined by: Eq.2: Delta P (pressure difference)=f (L/d)(Rho)(Um^2/2g) Um is the mean velocity f=1.325/[ln(epsilon/3.7d)+5.74/Re^0.9]^2 for tubes.. Another approximation u...
19. ### Dynamic mesh analysis

using boundary layers Well before u use this option u have to delete autosmoothing from Gambit..to do this Edit-->Defaults, then put autosmoothing to a value of zero. Then after u open the boundary layer meshing first, the options are pretty straight forward, there are drawing that gambit will...
20. ### Insulation thickness calculation

i didn't quite understand u where insulating what from what, but ur dealing with high temperatures here, and i think u should research professional companies, as for the calculations, after u choose the material u want u would be able to get the thermal conductivity constant from it and u can...
21. ### Hydro carbon fuel - H2 % value of total heat

actually its 56% C and 44% H, and a value nearly equal to 7% to the final yield is used for bond breaking. but how can u ignore the energy needed to break the bonds? u can't do that.
22. ### Determine the capacity of a boiler

i think the peak load needed can be calculated using Q=m c DeltaT, m being flow rate, c specific heat ratio, and DeltaT should be the difference in temperature from inlet to outlet thus telling us how much heat the water absorbed. after this step you would have to do complex forced...
23. ### Thermal Energy storage of phase change material

WEll other than ur heat transfer book u can ask ur university for Fluent tutorials provided by the manufacturer of the program they have EXACTLY the same problem ur trying to solve, a tutorial involving phase change :). As for ideas i think fins is a good idea, other ideas would be difficult to...
24. ### Thermodynamics u-tube help

btw this is not even close to thermodynamics !!
25. ### Thermodynamics u-tube help

Ok simple, we know that the pressure exerted by a fluid is explained by the following relation: P= rho * g * height of water. g is the gravity. now on the water side we have P = Rho of water*g*H on the other side we have P= Rho water*g*H1 + Rho Oil*g*4H1 (since height of oil is 4 times that of...
26. ### Life of a spring

try finding books of Mechanical Design subjects, or Theory of Machines. they usually contain such answers, they are long formulas with many many variables sometimes more than 8 variables that depend on the materials and applications of the spring. good luck
27. ### Ideas for review paper

i didn't quite understand what you want, but i'm a Mechanical engineer and most of us know aerodynamics and heat transfer whether finite or not. i mean applications OF the SR-71? like spying?or research? then u move to sonic booms, which is all about physics and calculations, but are mostly...
28. ### Heat Exchanger problem

i would go with the manometer, it is more accurate. There is an error in the formula u r given, no wonder ur off target. the Nusselts number is DIRECTLY proportional to Reynolds number, so u have to lose the -8, actually the equation is: Nu= 0.023Re^0.8 x Pr^n. where n is 0.4 for heating of the...
29. ### Is it possible to find the combustion pressure on any ICE?

well to calculate peak pressure i would normally use chemistry and assume full combustion. but if the torque is known, then u can calculate the force translated to the piston, having the area of the piston we know that P=F/A. to find the force reaching the piston you would have to go through...
30. ### Hydro carbon fuel - H2 % value of total heat

Here goes: i really had to dig up the past to get you the answers, lucky i still know where i have put them:) In ideal combustion the combustion energy of hydrogen is 120000KJ/Kg, the 141800 is the higher heating value and cannot be used in engine yield calculations or combustion calculations...