Question

1. Motor oil at T=-30 deg F has a kinematic viscosity of ν=0.11ft²/s and a specific gravity of SG=0.88. (The rest of this is made up numbers and may not be indicative of actual car engine behavior) Assume that the oil flows at a velocity of V=2ft/s through a cast iron conduit within the engine block. Treat the conduit as a “best case roughness” (use smallest number for ε if needed) cast iron pipe with a diameter of 0.5in and a length of 5ft. Assume oil height is raised by 1ft.
   1. What is the Reynolds number?
   2. Is this laminar or turbulent flow?
   3. What is the friction factor f? Show how you determined this by calculation or moody diagram as applicable.
   4. What is the head loss in ft?

Answer 1

Given,

Kinematic viscosity , v = 0.11 ft2/s

Specific Gravity , G = 0.88

Velocity , V = 2 ft/s

Diameter , d = 0.5 inches = 0.04167 ft

Length of Conduit , L = 55ft

a)

Reynolds Number, Re =

=  

= 1000

b,

1. If Re < 2000, the flow is called Laminar
2. If Re > 4000, the flow is called turbulent
3. If 2000 < Re < 4000, the flow is called transition

therefore the flow is Laminar

c,

Friction factor , f =   ( for laminar )

=

= 0.064

Due to rough regime pipe it is essential to employ yet another dimensionless parameter of the flow, the roughness Reynolds number

( were ε = 1 )

= 2166

d,

Head loss =

= 0.064*1322.115*0.2

= 16.92 ft