A plane wall with surface temperature of 350°C is attached with straight rectangular fins (k = 235 W/m · K). The fins are exposed to an ambient air condition of 25°C and the convection heat transfer coefficient is 154 W/m² · K. Each fin has a length of 50 mm, a base of 5 mm thick and a width of 100 mm. Determine the efficiency, heat transfer rate, and effectiveness of each fin, using

(a) Table 3–3

(b) Figure 3–43.

Table 3-3

Figure 3–43

Transcribed Image Text:

TABLE 3-3 Efficiency and surface areas of common fin configurations Straight rectangular fins m = √2h/kt L = L + 1/2 Afin = 2wLc Straight triangular fins m = = √2h/kt Afin 2w VI²+ (1/2)² = Straight parabolic fins m= V2h/kt Afin WL[C₁ + (L/t)In(t/L + C)] C₁ = V1 + (1/L)² Circular fins of rectangular profile m = √2h/kt 12 = √₂+1/2 Afin = 277(1³-1²) nfin nfin fin = = = tanhmL mLc 1 1(2mL) mL I,(2mL) 2 1 + V(2mL)² + 1 K₁(mr₂)I₁(mr₂.) — 1₁(mr₁)K₁(mr₂c) C₂ ²1(mr₁) K₁(mr₂.) + Ko(mr)1,(mr₂) 2r,/m r² - 1² I y=(1/2) (1-x/L) y=(1/2) (1-x/L)²