--%>
Assignment Help - homework help

Problem on convection coefficient

An experiment to determine the convection coefficient associated with airflow over the surface of a thick stainless steel casting involves insertion of thermocouples in the casting at distances of 10 mm and 20 mm from the surface.  When the experiment was performed in a well insulated air duct so that the temperature of the walls surrounding the steel surface was the same as the air temperature, the thermocouples measured the temperatures of 50°C and 40°C in the steel, respectively, when the air and the surrounding wall temperatures were 200oC.

a) If the steel has a thermal conductivity of 15 W/m2K and surface emissivity of 0.95, what is the convection coefficient between the steel and hot air?

b) Determine the contributions of convective and radiation heat fluxes to steel casting?

In the recurring experiments the duct insulation was eliminated and even though the hot air temperature was similar as before, i.e., 200oC, the surrounding walls temperature dropped to 20oC. As a result the steady state heat flux to the steel casting dropped by 13.3% compared to the first experiment.

c) Supposing similar convection coefficient as the value coputed in part a), what would be the temperatures measured by the thermocouples?

d) Assume that the steel casting were well insulated from each and evry side except for the surface from which the distance to thermocouples is measured. Assuming the same convection coefficient as the value calculated in part a), what would be the temperatures of the thermocouples when:

i) The experiment is performed in the well insulated duct at T∞ = Tsurr = 200oC?
ii) The experiment is executed in non-insulated duct at T∞ = 100oC and Tsurr = 20oC?

   Related Questions in Chemistry

  • Q : Polymers comparison of biodegradable

    comparison of biodegradable and non-biodegradable polymers

    		•
  • Q : Explain Photoelectron Spectroscopy. The

    The energies of both the outer and inner orbitals of atoms and molecules can be determined by photoelectron spectroscopy.Energy changes of the outermost or highest energy electron of molecules were dealt with here in a different passion. The energies of ot

    		•
  • Q : Relative reactivity Which is more

    Which is more reactive towards nucleophilic substitution aryl halide or vinyl halides

    		•
  • Q : Quantum Mechanical Operators The

    The quantum mechanical methods, illustrated previously by the Schrödinger equation, are extended by the use of operators. Or, w

    		•
  • Q : Water under pressure problem-henry law

    Can someone help me in going through this problem. The statement “When 0.003 moles of a gas are dissolved in 900 gm of water under a pressure of 1 atm, 0.006 moles will be dissolved under the pressure of 2 atm", signfies: (a)

    		•
  • Q : Mole fraction and Molality Select the

    Select the right answer of the following question.What does not change on changing temperature : (a) Mole fraction (b) Normality (c) Molality (d) None of these

    		•
  • Q : Describe chemical properties of amines.

    Like ammonia, primary, secondary and tertiary amines have a single pair of electrons on N atom. Hence chemical behavior of amines is similar to ammonia. Amines are basic in nature, and in most of the reactions they act as nucleophiles.      1. Reaction wi

    		•
  • Q : Number of electrons in the benzene

    Describe the number of electrons in the benzene? Write a short note on it?

    		•
  • Q : How reactive is Trimethylindium towards

    Illustrate the reason, how reactive is Trimethylindium towards oxygen and water?

    		•
  • Q : Value of molar solution Select the

    Select the right answer of the question. Molar solution contains: (a)1000g of solute (b)1000g of solvent (c)1 litre of solvent (d)1 litre of solution

    		•