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  1. R

    Calorific value of Petrol

    Actually I wanted to know if a country ,for example, chooses to extract petrol from liquefaction of coal over cracking of crudeoil, will the petrol be the same as (in terms of energy content) from crude oil.
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    Calorific value of Petrol

    Thanks for the reply. The link you referred gives heating value of many fuels. Is there any source where I can get heating values of petrol extracted from crude oil and, from liquefaction of coal. Are they really different?
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    Calorific value of Petrol

    Hi I am bit confused regarding the heating/calorific value of petrol (used for vehicle) extracted from crude oil and from liquefaction of coal. Should they be same? or Petrol extracted from crude oil will have different calorific value compared to the petrol from liquefaction...
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    Wave Propagation in Vibrating Solid

    Hi I am very confused at determining the type of elastic wave in a vibrating body. For example, an elastic solid is flexuraly vibrating in one of its resonant mode. There should be elastic wave excited from this vibration. But, my question is which wave will be excited through it...
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    Numerical Integration of Double integrals

    Is my way of doing the double integration correct using the trapezoidal rule?
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    Numerical Integration of Double integrals

    so the unit would depend on the unit I am considering for the function. Although the integral is not computing an area but the integral is found from the area of the curve drawn from the function along its limits numerically. e.g. ∫x^3dx= x^4/4 [m^4] (limit say 0 to 5) So I can evaluate it...
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    Numerical Integration of Double integrals

    Please see the attached for the function psi.
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    Numerical Integration of Double integrals

    I have a double integral: ∫∫sin^2(∏x/A)*sin^2(∏y/B)dxdy A=length along x B=length along y ranges: 0 to A(for x) & 0 to B (for y) Analytical result is: A*B/4 (unit^2) Now, I want to evaulate it numerically using trapezoidal rule. Infact, I have done it but not sure whether it is a right...
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    Polar Integration

    Thanks. Actually the problem says that, integrate f(r,θ) in radial and circumferential direction. So it is a bit confusing. I guess rdrdθ could be used depending on my problem. Here, the function f(r,θ) is the mode shape function of a circular plate.
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    Polar Integration

    Thanks. I have a function of r. For example at theta=0, the value of the function have different value at different r values (e.g. r=0 to r=a). I want to evaluate this function over 2∏. So I thought first integrating the function about r and then theta. That is where I am confused, whether to...
  11. R

    Polar Integration

    Hi I have a function [e.g. f(r)] which I want to integrate over r and θ. What would be the integration form? Which one is correct? ∫∫f(r) drdθ OR ∫∫f(r) rdrdθ Please explain. Also, can it be said as area integration as well like the one in cartesian coordinate?
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    Area of the Curve

    Hi How can I calculate the area of the shaded region in picture attached? Please suggest.
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    Increasing Heat Transfer Area

    Is there any effect on temperature, when a flow experience sudden enlargement?
  14. R

    Increasing Heat Transfer Area

    Heat transfer is much less in case of low flow rate. I need the reactor to be heated within a shorter period. But it all failed. A new design is the only solution I guess. Is the heat capacity of damp air higher than the dry air? How can I prove (theoretically) that damp air could improve heat...
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    Transient Heat Transfer in Radial Direction

    Yes the purpose of the fins is to make uniform temperature profile. How can I explain this phenomenon with my geometry? Could you please help? Is is beacuse of a shorter heat path for heat conduction from the walls?
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    Increasing Heat Transfer Area

    I have tried with low flow rate. The heat transfer is much less. My air is coming out from a compressed air cylinder. Could you please explain why the heater is not able to heat the air? could it be because of heat loss through the walls?
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    Transient Heat Transfer in Radial Direction

    It was for my experimental results. My simulation result is also similar to that. But incase of my simulation, i have used constant heat flux and also used a guessed value of h. So results differ from experiment but trends have some similarities. Why the experimental result is so uniform in...
  18. R

    Increasing Heat Transfer Area

    Unfortunately I don't have any flow measuring device attached to my system. I really want to calculate what should happen, but don't know where to start from.
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    Transient Heat Transfer in Radial Direction

    Why am I getting an uniform temperature profile at different radial positions (please above pic) i.e. the temperature difference between one node to another is very small, when using fin? But without fin (only steel shell) the temperature difference is much higher between nodes, especially the...
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    Value of Heat transfer coefficient

    basically, I am trying to see the temperature profile inside the cylinder after a certain period using COMSOL. I am using internal heat flux boundary condition where my external temperature is at 350C and value of heat transfer coefficient has to be given also. So how much time it takes for the...
  21. R

    Value of Heat transfer coefficient

    Sorry about that. Please check now.
  22. R

    Value of Heat transfer coefficient

    where can I get nusselt number for my geometry [please see the pic]??
  23. R

    Value of Heat transfer coefficient

    I have a circular cross-section of steel, around which I have air of constant temperature flowing. I want to calculate the heat flux, but I don't have the value of heat transfer coefficient,h (W/m^2.K) between steel and this air at 350C. Please suggest how to get the value for h. I am neglecting...
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    Increasing Heat Transfer Area

    I think you are right. Too much heat is lost through the walls. Most of it is in the wall surrounding the coil heater. So at moderate flow, air looses the heat through the walls. At high flow the air looses less heat but the heater is unable to cope with high flow, thats why the heater...
  25. R

    Increasing Heat Transfer Area

    Preheater is between the coil heater and compressed air line..
  26. R

    Increasing Heat Transfer Area

    I did not calculate 420W. It is the rating of the heater that is being used in the system. Last day I set the coil heater to 500C and the prheater to be 400C. After flowing the air at high flow rate, both the temperature dropped to 288C and 175C respectively. The powder bed has very low thermal...
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    Increasing Heat Transfer Area

    Powder bed is inside a reactor vessel and, the reactor is enclosed with another vessel ( with gap between them for air flow). Please see the earlier posts in this thread for a schematic. At a relatively moderate flow rate, the heat transfer is slow within the bed and at a high flow rate the heat...
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    Increasing Heat Transfer Area

    well, preheating also did not worked as the temperature of the powder bed reached only 180C after 4 hrs of heating!! :(
  29. R

    Transient Heat Transfer in Radial Direction

    I have created the geometry and also computed results using comsol but, as the outer shell is extracting heat from air surrounding it, I have specified heat flux as the boundary in the outer shell. This is the only boundary condition I have set. For that I need heat transfer coefficient for the...
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    Transient Heat Transfer in Radial Direction

    @Unrest: Please look at my geometry and suggest how can I determine the temperature profile at these nodes. I am still struggling to build up a mode with FDM because of multiple material properties. :( Also in comsol having some difficulties with the boundary condition. :confused:
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