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1.1 A curtent carrying conducter (2im lene, 0.3cm diameted) loses 90W and it is in a 25 t C envirenment. If the conductor surface temperature is 152C, the convection heat transfer corficient neplecting radiation is approuimately 1.2. The themal cosaat cenducaance at the interface ef two ceometrically imilar leng aluminum plates in measured to be to.poo W/m. R. the thermal cenductivity of aluminum is 237WHm. Ki. if the contact resistance it equal to the thermal resisance of a plate, the thickines of a plate assuming unit heat transier area is (6) 2cm. (a) 237cm (a) 10cm(v)5cm (v) not even 1.3 A 1 w electric resiatance heater in a room is tuened on kept on for 50 minutes. The amount of enerby released by the heater to the room is (b) 1xw (a) 1kj (a) 3600kj (iv) 6000k] (v) 3000k 1.4A10m iene. 8cm over eusus trindrical anem piof is covered with 3cm thick cylindrikal insulation (k=0.05 W/m."Cll if the rate et heat lsis frem the pipe ia a000 W, the temperature drop acrois the insulation is (6) 1044c (a) 1434C (a) 5 se 4 (i) 282C (x) 6004 15 Conuder the following statements in felation to heat transfer by madiation. (A) a medium is necessary for radiation heat trandter (6) matiatien enercy is transletred the eugh electremagutic wown (C) the radation heat enersr emitsed by all redi iorfaces is lesi than the radution entrev emitted by a blackbody at the same ienserature Out of the above statements: (0) all are enoerect (a) osly (A) an correct Ime enly ( b) is cerect (a) only (d) and (c) are reerect (d) all are certect f NoG3023 - Heat Transfer Fxamal-Spring 2021 Name: 1.6 A current carnine insulated long wie f 0.30.15W/m.4C C) is exposed to an ambience this has a convective heat trantiler ceefficient (h) of 12W/m3 lic. The diameter of the wire in 3mm asd the insulution thicknew is 2mm. If the highest posible heat trandier rate per weit length of the wire to the ambience is devired, what should be the thickness of the insulation? (4) 2mm (a) 11.9 mith (a) 12.5mm (ivi) 10.5mm (v). .5mm 1.7 Tao wally A and s have the wame surface arem and the same teingerature drops aoross their thickenewes. The ratio of thermal conductivities (ka/ks) is 4 and the ratio of wall thickeneses (L/L) is 2 . The ratio of soedcy suate heut tramiler rates threuch the wath (8A)in (1) 1 mos fis 1mi4in2 1.8 Acoonding to founier's Lwet heat conduction; (A) steady state heat transfer iate is diectly proportional to temperature gradent. [E] iteady state hear tranider aate is dinecty preportional to thermal resistance ICI ateady teate heat traniler rate is invethely preportional to thermal tewatance Out of the above isatements: (0. (A) and (i) are comect (S) (A) and (C) are correct (E) as satements are wrent (i) Only (A) is correct (A) only (B) is correct