MEE0 (F) / Page of Session : August 0 FINA Examination Paper (COVER PAGE) Programme : BACHEOR OF ENGINEERING (HONS) IN MECHANICA ENGINEERING PROGRAMME (BMEGI) Course : MEE0 : Combustion, Heat and Mass Transfer Date of Examination : (Thursday) December 0 Time : 8.00 am 0.00 am Reading Time : Nil Duration : Hours Special Instructions : This paper consists of SIX questions. Answer any FOUR questions in the answer booklet provided. All questions carry equal marks. Materials permitted : Non-Programmable Scientific Calculator Materials provided : Formulae Data Sheet Attached as Appendix Examiner(s) : Dr Koh Yit Yan Moderator : Associate Professor Dr Hj Mohd Yusuff Bin Mohd This paper consists of 4 printed pages, including the cover page.
MEE0 (F) / Page of INTI INTERNATIONA UNIVERSITY BACHEOR OF ENGINEERING (HONS) IN MECHANICA ENGINEERING MEE0 COMBUSTION, HEAT AND MASS TRANSFER FINA EXAMINATION : AUGUST 0 SESSION Instructions: This paper consists of SIX questions. Answer any FOUR questions in the answer booklet provided. All questions carry equal marks. Question (a) Steam at 0 C flows in a stainless steel pipe (k = W/m C) whose inner and outer diameters are 6 cm and 8 cm, respectively. The pipe is insulated with 6-cm thick glass wool insulation (0.08 W/m C). Under certain condition, the pipe is exposed to the surrounding, subjected to a cross air flow of 6 m/s at 0 C. If the surface of the pipe has a temperature of 4 C, and taking the heat transfer coefficient inside the pipe to be 80 W/m C, determine the rate of heat loss from the steam per unit length of the pipe. (b) Comment on the event shown in Figure Q(b) in the context of heat transfer. (0 marks) Figure Q(b) ( marks) Question (a) Imagine you are driving your vehicle. You realised that your vehicle is running out petrol and you need to pump petrol. If given a choice, would you use RON9 or RON97 for your vehicle and also provide the reasons for making this choice. ( marks)
MEE0 (F) / Page of (b) Propylene (C H 6 ) is burned with 0% excess air during a combustion process. The reaction takes place at C, atm. Assuming complete combustion and the total product pressure of 90 kpa, determine: (i) (ii) The stoichiometric and actual air-fuel ratio. The temperature at which water vapour in the products will start condensing. Briefly explain the significance of the pressure in affecting the dew point temperature. (iii) Calculate the enthalpy of combustion for this process. Briefly comment on your answer. (0 marks) Question (a) What is the greenhouse effect and why is it a matter of great concern among atmospheric scientists? ( marks) (b) Glycerin (C p = 480 J/kg C) at C, enters a double-pipe counter-flow heat exchanger at 0. kg/s, and is heated by water (C p = 480 J/kg C) entering the system at 00 C and flowing at a rate of kg/s. The desired outlet temperature for glycerin is 0 C and the overall heat transfer coefficient is 900 W/m C. Determine the surface area required for the heat exchanger using one method and then verify your answer by the second method. (0 marks) Question 4 (a) Pick an example where the concept of heat exchanger is observed. Explain how the idea of heat exchanger is incorporated into your example. ( marks) (b) The spectral emissivity function of an opaque surface at 00 K is approximated as: 0.0, 0.48, 0., 0 6 m 0 m 6 m 0 m Determine the average emissivity of the surface and the rate of radiation emission from the surface per square meter. (0 marks) (c) The temperature of a filament of an incandescent light bulb, which can be treated as a blackbody, is 00 K. Determine the fraction of the radiant energy emitted by the filament that falls in the visible range. Also, determine maximum wavelength of the emission of the radiation from the filament. (0 marks)
MEE0 (F) / Page 4 of Question (a) The building of Beijing Airport uses the strategy such that maximum sunlight is obtained for the building. Discuss this phenomenon in the context of heat transfer. ( marks) (b) Show that, from the Fourier s law of conduction, the thermal resistance can be represented r r through the relationship R sphere. 4 r r k (7 marks) (c) A spherical, thin-walled metallic container is used to store liquid nitrogen at 77 K. The container has a diameter of 0. m and is covered with an evacuated, reflective insulation composed of silica powder. The insulation is mm thick and with the thermal conductiity of 0.000 W/m C, and its outer surface is exposed to an ambient air at 0 K. The convection coefficient of the liquid is known as 0 W/m C. Find the rate of heat transfer through the wall of the sphere, if the sphere is left in an environement with natural convection. Take = 0.00K -. ( marks) Question 6 (a) Water is boiling in a -cm-deep pan with inner and outer diameters of and cm, respectively that is placed on top of a stove, as shown in Figure Q6(a). The ambient air is recorded as C and the emissivity of the outer surface pan is 0.8. Assuming the entire inner and outer surface of the pan to be at an average temperature of 00 C and 98 C, respectively, determine the thermal conductivity of the of the pan. Neglect the heat loss by evaporation and heat loss from the top and bottom of the pan. Figure Q6(a) (0 marks) (b) Discuss how the process of the combustion contributes to the green house effects and how can this be tackled? ( marks) --THE END MEE0(F)Aug/KohYitYan/CA/0400
MEE0 (F) / Page of MEE0 COMBUSTION, HEAT AND MASS TRANSFER DATA SHEET FOR USE IN EXAMINATIONS Nusselt number, Prandtl number, Raleigh Number, Ra = Gr Pr x x hx Nu x Thermal diffusivity, k v Pr Grashof number, k c p g T Gr v UA No. of transfer units, NT U C min FORCED CONVECTION OVER A FAT PATE Re Pr 0.6 0 0 Re 0.6 Pr 60 0 7 Nu C f Nu C f 0.664Re.8Re 0.07Re 0.074Re 4 Pr Pr FORCED CONVECTION OVER CYINDERS AND SPHERES Cylinder Nu cyl 0. 0.6Re 0.4 Pr Pr 4 Re 8000 8 4 Sphere Nu sph 0.4Re 0.06Re Pr 0.4 s 4
Properties of Saturated Water MEE0 (F) / Page 6 of
Properties of Air at atm pressure MEE0 (F) / Page 7 of
MEE0 (F) / Page 8 of Empirical Correlations for the Average Nusselt Number for Natural Convection over Surfaces
MEE0 (F) / Page 9 of View Factors for Various Combination of Geometries - Two Aligned parallel rectangles of equal size Two Perpendicular Rectangles with a Common Edge
Properties of iquids MEE0 (F) / Page 0 of
NTU Relations for Heat Exchangers MEE0 (F) / Page of
Blackbody Radiation Function f MEE0 (F) / Page of