Problem 3 (20 points) A light motor oil is to be heated in a 1/4-in Schedule 40 steel pipe 15 ft long having a surface temperature of 350F (pipe wall temperature). The oil is to be heated from 150 to 250F. The oil characteristics are given below. Assume the flow is laminar and the Graetz number is large enough for the final equation for laminar flow heat transfer to apply. a)Calculate the correction factor (ov) that accounts for the difference between heating and cooling b)Find the mass flow rate of oil (m) that can be heated in this pipe (lb/hr). Check next slide. c)What heat coefficient can be expected (Btu/ft2.h.F)? d)Calculate the Re number to check the validity of a laminar flow assumption. Thermal conductivity (Btu/ft.h.F) Specific Heat (Btu/lb.F) Temperature (F) 0.082 0.48 Viscosity (CP) 6.0 150 250 3-3 350 1.37 Problem 3- Cont. Helpful hints for part b: b) Find the mass flow rate of oil (mn) that can be heated in this pipe (b/hr). ? Using m= V pS = GS (S is the cross-sectional area of pipe, App. 3) won't help much as the velocity is unknown Using a = cp (250 150) is a good start but both m and q are unknowns. Using q=U A AT, is good but both U and q are unknowns. Therefore, Since you are assuming laminar flow, you can use the equations for this type of flow to find m. Check the solution of Problem 12.1 on the PP slides of Chapter 12- Part 1. We solved the problem for a laminar flow. In addition, Check Eqs. (12.19), (12.20), and (12.27). You will have here two unknowns hi and m. You will use a combination of equations to find m. Note here that: 91 = UAATis part of Eq. (12.20) for constant wall temperature. Remember that = A = circumference of cylinder or pipe x length of pipe = 1 DL