Heat Transfer Class (Mech Engineering, Raldi A. Koestoer)
Take Home Examination
Please write your Name, Stud Number, Handphone, Email.
Submission date : Thursday , 12 November 2013 at 16.00. From member to Michel and then Michel transfer the folder to teacher. Filename must be your nickname. Copy-paste will be punished severely, this is an individual test.
Your text format should be better in MSWord 2007. Look at your last digit of stud number, if your digit include in 0 to 3 you must use the A data, for 4 to 6 use B data, for 7 to 9 use C data.
You can use any data table for the empirical formulation concerning Nu, Gr, Re, Pr, Ra or other physical properties, from books, documents, or address in web, but you should have to mention the reference.
Any question about this THE can be discuss by mailing-list.-
The composite wall of a furnace consist of steel plate and L1 cm thick refractory wall separated by L2 cm air gap. Estimate the inside temperature of the refractory wall when the steel plate and ambient temperature are T1 dgC and T2 dgC, respectively. The thermal conductivity of the refractory wall is 0.05 Btu/hr.ft.dgF (pls convert to SI unit). Assume there is no convective heat transfer in the air gap.
(guidance: the heat transfer to the ref wall from the steel plate occurs by radiation only, further transfer through the ref wall by conduction to the outside air, sketch the position first).
A : L1 24 cm. L2 48 cm, T1 500, T2 35.
B : L1 30 cm, L2 40 cm, T1 700, T2 32.
C : L1 30 cm, L2 48 cm, T1 900, T2 28.
Consider a heating chamber with 1 meter high vertical wall. The wall surface temperature is T1 dgC and the ambient is T2 dgC.
Find the convective heat transfer coefficient and the rate of heat transfer per unit surface area of the wall. Neglect radiation heat transfer. (Select yourself the properties of air at 1 atm absolute).
A: T1 300 T2 40
B: T1 450 T2 30
C : T1 600 T2 40
Determine the radiant heat flux transferred between 2 parallel planes of dimension h m, L m, w m. Temp of the planes are T2 K and T1 K . The surrounding will be considered the third surface with T3 0K (Zero K). The emissivities of the planes are e1 0.4 and e2 0.7.
A : h 1,5 L 3,0 w 3,0 T2 900 T2 1100
B : h 2 L 2,5 w 4,0 T2 600 T1 700
C : h 4 L 2,5 w 4,0 T2 600 T1 900
Water (Cpw =4181 J/kg dgK) at 20 dgC at the rate of M1 Kg/hr It is used to cool engine oil (Cpo = 1900 J/Kg dgK) at T1 dgC, which flows at M2 Kg/hr. The overall heat transfer coefficient is 300 W/m2 dgK.
Calculate the oil outlet temperature if the coaxial intercooler function in (PF Parallel Flow or CF Counter Flow). Coaxial intercooler is a double tube concentrice.
A : M1 4000 T1 205 M2 11000 PF
B : M1 6000 T1 175 M2 8000 CF
C : M1 4000 T1 205 M2 11000 CF