Question

An array of electronic chips is mounted within a sealed rectangular enclosure, and cooling is implemented by attaching an aluminum heat sink (k = 180 W/m-K). The base of the heat sink has dimensions of wi = wº = 100 mm, while the 6 fins are of thickness: = 10 mm and pitch S = 18 mm. The fin length is 1; = 50 mm, and the base of the heat sink has a thickness of Ls = 15 mm. S Chips 4 L Water W... Electronic package, P If cooling is implemented by water flow through the heat sink, with = 3 m/s and 7 - 17°C, what is the base temperature T. of the heat sink when power dissipation by the chips is Perec - 1800 W? Take the increase in temperature of the water as it flows through the heat sink into account. The average convection coefficient for surfaces of the fins and the exposed base may be estimated by assuming parallel flow over a flat plate. Properties of the water may be approximated ask = 0.62 W/m.K. p = 995 kg/m',c, = 4178 J/kg K, v = 7.73 x 10 m/s, and Pr = 5.2. Assume the water does not escape through the upper surface of the heat sink and that the boundary layers on each fin surface do not merge, allowing evaluation of the heat transfer coefficient using an appropriate external flow correlation

Answer 1

GWEN DATA- PAGE Heat sink ka 180 w/mik -> Heat sink dimensions - W2 - 100mm 6 fins are q Bicknes t-lomm Pitch 18mm fin lengths Lt = somm Heat sink cleare IS mm PROPERTIES OF WATER - Ubo 2 3 m/s Тю 17c Pelec 1 800w k 0.62 wlmik 995 a Im3. 13 op 2 417 Ilngele 7.73 x107mels Pr 5.2 >> THERMAL CIRWIT! To TO Rь Reio CS

Το REOLVEL PAGE 2 q Pere To To Ro+Rto @v q Pele .. { Comin (Tv Tov) 1 - exp (-AI) o NTU UA (min =; Rb + Rtio Rb Сь k (wixw.) R4, о h NAH (e-nd) At At and At αλα fim and total surface Quasi- ile A 2wz (4 + 2x0-1 Coos too +00) 0.011m² At NAD tab 2 NAD +(N-1) (3.1) We (1001)+(6-1)(-01-01)x04 ((0.01)+ (5) Cooldoo) 80-1 0.0m

PAGE-3 0015 Ro 8.33 *10kwa 180 (0:18011) By taking (Rev) Reynolds number Uoo wi 3x0) 7737107 . 3.88 x105 Re L 5 X10 (laminar flow) يع 7 ] 0.664 (Re)'2 we (8) 73 0.62 0.6c4 x (s. 2220?)* 6-2," quua.6 wlmak. 2) he a (44 + + = (0.05 0.01 + 2) 2 0055 Ton in (male) e Tash (mx 0.055) 2 x (44424) [ ] Y Here 180 xool 70.25mt (toids 20.05S) -0.9991 Then Tanh

Tas hmlu RASEY Ey] s) ht - MLC 0.9991 7025 X0.055 94 O-a 58 Rt, o = 4442.6 x0:07 6.011)(6) (1-0.258) 0.04 2) Rt ,0 - 0.0107 kW 1 (8 - 33x1023) + (0.0107) 52.54 wlk UA 52.54 wlk e ) (min ap(N-1) 4 (s-t) to co 995 (6-1) Roos (0.018- 0.01) x3 x4178 24942. 66 52.54 u NTU 24942.66 Q.1x102 NTU = 2:1810?

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