INSTRUCTION: This paper consists of FIVE (5) structured questions. Answer all questions.

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1 INSTRUCTION: This paper consists of FIVE (5) structured questions. Answer all questions. ARAHAN : Kertas ini mengandungi LIMA (5) soalan struktur.jawab semua soalan. QUESTION 1 SOALAN 1 (a) Convert the measuring units as indicated: Tukarkan unit pengukuran seperti yang ditunjukkan: i. 70 F to K 70 F ke K 100 miles/hr to m/s 100 batu/jam ke m/s Calculate the amount of force (in lbf) required to accelerate a mass of 13.3 lbm at a constant acceleration of 1.20 ft/s 2. Kirakan jumlah daya (lbf) yang diperlukan untuk mempercepatkan jisim sebanyak 13.3 lbm pada pecutan malar 1.20 ft/s 2. [4 marks] (c) A 10 cm diameter copper ball is to be heated from 100 C to an average temperature of 150 C in 30 minutes (Fig 1). Taking the average density and specific heat of copper in this temperature range to be ρ = 8950 kg/m 3 and Cp = kj/kg. C, respectively, determine: Satu diameter 10cm bola tembaga akan dipanaskan daripada 100 o C kepada suhu purata daripada 150 o C dalam masa 30 minit (Rajah 1). Mengambil purata ketumpatan dan haba tentu kuprum dalam julat suhu ini sebagai ρ = 8950 kg/m3 dan Cp = kj / kg. o C, masing-masing, tentukan: 2 SULIT

2 Figure 1 / Rajah 1 i. the total amount of heat transfer to the copper ball. jumlah pemindahan haba kepada bola tembaga. [7marks] [7 markah] the average rate of heat transfer to the ball. purata kadar pemindahan haba kepada bola. QUESTION 2 SOALAN 2 (a) i. Define heat conduction. Takrifkan konduksi haba. [3markah] Water has a value of thermal conductivity, k =0.607 W/m C and iron 80.2 W/m. C at room temperature. Explain which is a better heat conductor, water or iron. Air mempunyai nilai kekonduksian terma, k = W / m C dan besi 80.2 W / m. C pada suhu bilik. Terangkan yang manakah merupakan pengalir haba yang lebih baik, air atau besi. [2 marks] [2 markah] 3 SULIT

3 Consider a 0.8m high and 1.5m wide double pane window consisting of two 4mm thick layers of glass (k = 0.78W/m.K) separated by a 10mm wide stagnant air space (k = W/m.K). Determine the steady rate of heat transfer through this double pane window and the temperature of its inner surface for a day during which the room is maintained at 20 o C while the temperature of the outdoors is -10 o C. Take the convection heat transfer coefficients of the inner and outer surfaces of the window to be h 1 = 10 W/m 2. o C and h 2 = 40 W/m 2. o C. Pertimbangkan panel tingkap berkembar yang mempunyai tinggi 0.8m dan 1.5m lebar terdiri daripada dua 4mm lapisan tebal kaca (k = 0.78W/mK) dipisahkan oleh 10mm lebar ruang udara tidak bergerak (k = W / mk). Tentukan kadar pemindahan haba mantap melalui tingkap berkembar dan suhu permukaan dalaman untuk sehari di mana bilik dikekalkan pada 20 o C manakala suhu luaran ialah 10 o C. Ambil pekali perolakan pemindahan haba permukaan dalaman dan luar tingkap adalah h 1 = 10 W/m2. o C dan h 2 = 40 W/m2. o C. [15 marks] [15 markah] QUESTION 3 SOALAN 3 (a) Explain briefly the basic principles of convection. [5 marks] Terangkan secara ringkas prinsip-prinsip asas olakan. [5 markah] Describe natural and forced convection. [4 marks] Huraikan olakan semulajadi dan olakan paksaan. (c) Water at 25 o C flows over a 3m long and 2m wide flat plate maintained at 75 o C with a velocity of 0.8m/s. Determine the rate of heat transfer from the entire plate. [11 marks] Air bersuhu 25 o C mengalir di atas plat rata 3m panjang dan 2m lebar yang bersuhu tetap 75 o C dengan halaju 0.8m/s. Tentukan kadar pemindahan haba daripada keseluruhan plat. [11 markah] 4 SULIT

4 QUESTION 4 SOALAN 4 (a) State the difference between radiation and the other two mechanisms of heat transfer. Nyatakan perbezaan di antara radiasi dan dua mekanisme pemindahan haba. [2 marks] [2 markah] Define the total and spectral blackbody emmisive powers. Takrifkan total blackbody emmisive power dan spectral blackbody emmisive power [4 marks] (c) Consider a 20-cm x 20-cm x 20-cm cubical body at 1000 K suspended in the air. Assuming the body closely approximates a blackbody, determine; i. the rate at which the cube emits radiation energy, in W, [3marks] the spectral blackbody emissive power at a wavelength of 4 µm. Pertimbangkan sebuah kiub bersaiz 20cm x 20cm x 20cm pada suhu 1000K terapung di udara. Dengan anggapan bahawa kiub adalah blackbody, tentukan i. kadar kiub mengeluarkan tenaga radiasi dalam unit W [3markah] spectral blackbody emmisive power pada gelombang 4µm (d) The temperature of the filament of an incandescent lightbulb is 3200 K. Treating the filament as a blackbody, calculate; i. the fraction of the radiant energy emitted by the filament that falls in the visible range. [6marks] the wavelength at which the emission of radiation from the filament peaks. [2marks] 5 SULIT

5 Suhu filament lampu kalimantang ialah 3200K. Anggap filament adalah blackbody, i. Tentukan pecahan tenaga radiasi dipancarkan oleh filament dalam julat nampak [6markah] Tentukan gelombang di mana pancaran radiasi dari filament pada kemuncak. [2marks] QUESTION 5 SOALAN 5 (a) Draw a 2 shell-passes and 8-tube-passes shell and tube heat exchanger. Explain the primary reason for using so many tube passes. Lukiskan penukar haba 2 shell-passes dan 8 tube-passes. Terangkan sebab utama menggunakan tube passes yang banyak. [5 marks] [5 markah] Hot oil is to be cooled in a double tube counter flow heat exchanger. The copper inner tubes have a diameter of 2 cm and negligible thickness. The inner diameter of the outer tube (the shell is 3 cm). Water flows through the tube at the rate of 0.5 kg/s and the oil through the shell at a rate of 0.8 kg/s. Taking the average temperatures of the water and the oil to be 45 C and 80 C, respectively. Determine the overall heat transfer coefficient of this heat exchanger. Given: Nu = 0.023Re 0.8 Pr 0.4 Minyak panas disejukkan di dalam penukar haba berlawanan arus tiub berganda. Tiub tembaga dalaman mempunyai diameter 2 cm dan ketebalan diabaikan. Diameter dalaman tiub luar ( shell adalah 3 cm). Air mengalir melalui tiub pada kadar 0.5 kg / s dan minyak melalui shell pada kadar 0.8 kg / s. Suhu purata air dan minyak adalah 45 C dan 80 C, masing-masing, tentukan pekali pemindahan haba keseluruhan penukar haba ini. Diberi: Nu = 0.023Re0.8Pr0.4 [15 marks] [15 markah] SOALAN TAMAT 6 SULIT