# unit operations

**Topics:**Fluid dynamics, Viscosity, Reynolds number, Length, Experiment, Hypothesis /

**Pages:**15 (2104 words) /

**Published:**Oct 13th, 2014

Michael Hunter, Yianni Dres, Endy Lau

Section: W2-805

Professor Maase

November 26, 2013

Introduction: The purpose of the efflux lab experiment is to determine the time it takes a liquid to drain from a certain height in a tank through an exit pipe under the influence of gravity. The time it takes to completely drain the tank from one point to another is mostly dependent on the exit pipe’s height and the inner diameter. Other factors such as frictional forces, pressure and velocity may also contribute to the efflux time. The first objective in this experiment is to determine efflux times of water with different varieties of pipes. These efflux times will be compared to calculated theoretical values through the use of Bernoulli’s equation1. The second objective is to determine the effect that pipes of different diameters and lengths have on efflux times. We will be observing data from the 70 in line on the tank to the 56 in line (Figure 3).

Assumptions:

Constriction and friction losses are negligible.

Standard room temperature was 25 °C and atmospheric pressure was 2,116.8 lb/ft2

Normal friction of water (µ = 5.98 x 10-4 lb/f*s) and density of water (ρ = 62.4 lb/ft3)

PA = PB (pressure), and ZB = 0 ft (height), Velocity coefficient (α) = 0

Cross sectional area is much greater than that of the pipe (VA 4000). Once the type of flow was categorized as turbulent, the turbulent flow efflux time equation was used to calculate the theoretical efflux time. This was represented by the equation: t= (1.6 + )1/2 ()1/2[(h1+L)1/2 – (h2-L)1/2] [3]. For this equation AT is the cross-sectional area of the tube, AP is the cross-sectional area of the pipe, L is the length of the pipe, H1 and H2 are the starting and stop height, and g is the gravitational constant. Since the calculated Reavg > 4000, it was turbulent. The efflux time was then calculated using the derived Bernoulli equation

References: 1. Cengel, ,. Y., & Cimbala, J. M. (2014). Fluid Mechanics: Fundamentals and Applications. New York: McGraw-Hill. 2. Sherine Dao, Dhir Patel, and Thao Tran: Efflux Time for a Tank and a Pipe Pre-Lab: November 3rd, 2013