Question

please answer this as soon as possible

1) Air at 15.6°C and 1 atm abs flows across a bank tube consisting of total 10 tubes of 30-mm outside diameter in a staggered manner consisting of 3 transverse rows in the direction of flow and 4 rows normal to the flow as exactly shown in the below picture. The velocity of the air as approaching the bank of the tubes is 5 m/s. The tube surfaces are maintained at 50°C. The spacing Sn of the tubes normal to the flow is 60 mm and Sp is also 60 mm parallel to the flow. Length of the tubes is 0.5 m. a) Calculate S for this staggered design (10 Points)? b) Calculate the maximum possible velocity (Vmax) for this design and show in the below picture the location at which the max velocity is happening and why (10 Points)? c) For a 0.5-m length_of the tube bank, calculate the heat-transfer rate. (30 Points)? Hint: Please note that one trial solution is enough even if your calculated Tbo is different from your initial guess. 申 Question 1 Solution: tlow

Answer 1

Eq.6.12 gives (3) ...... 47.01 4(1.92) 0.87(415) 4 s φ φ τ φ σ == = bd Ld Eq.6.13 gives d f Lo V M L d )( 1 when s σ = +≤ To find M1, we need xu mm 157.46 (300) 0.36(20) (942) 0.87(415) 0.36 0.87 = = = bf Af x ck sty u xu,max = 0.48(400) = 192 mm Since xu < xu,max ; M1 = 0.87 fy Ast (d – 0.42 xu) = 0.87(415) (942) {400 – 0.42(157.46)} = 113.55 kNm ….. (4) From Eqs. (3) and (4), we have (5) ...... )( 01.47 1 L

At the point of inflection Lo is the maximum of d (= 400 mm) or φ = mm). 240 ( 12 With Lo = 400 mm, we can write from Eq.(5) 400 } )10(200 )10(55.113 { 01.47 3 6 φ ≤ + which gives φ ≤ 20.58 mm. Thus, use of φ = mm 20 satisfies the bond requirement.