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MERLOT II


    

Peer Review


Moody Friction Factor Calculator

 

Ratings

Overall Rating:

3.7 stars
Content Quality: 3.5 stars
Effectiveness: 3.3 stars
Ease of Use: 4.2 starsstar
Reviewed: Nov 24, 2004 by Engineering Editorial Board
Overview: The Moody Chart, which provides values for friction factors for flows through
pipes and ducts, has been one of the more useful charts in fluid mechanics since
its introduction by L.F. Moody in 1944. This online calculator provides a
simple way to determine Moody Friction Factors for turbulent and laminar flows
that would be using in calculating headloss in flow conduits of circular and
noncircular cross section areas.

Learning Goals: To provide students of fluid mechanics with a convenient means of calculating
the friction factor for liquid or gas flows in pipes or ducts.
Target Student Population: College level civil,chemical or mechanical engineering students taking classes
in fluid mechanics.
Prerequisite Knowledge or Skills: Knowlege of fluid friction losses and some familiarity with the traditional
Moody chart.
Type of Material: An online calculator.
Recommended Uses: For students solving problems in pipe or duct flow.
Technical Requirements: A JAVA-enabled browser. It works well using both Netscape Navigator 7.1 and
Internet Explorer 6.0. Other browsers were not tested.

Evaluation and Observation

Content Quality

Rating: 3.5 stars
Strengths: The calculator is reasonably accurate over most of its stated range of validity
and employs accepted relations for calculating the friction factor in the
laminar (Re < 2100)and fully turbulent (Re > 5000)flow regimes. It wisely makes
no attempt to calculate friction factors in the transition range (2100 <5000).
Concerns: The calculator uses an explicit equation for determining the friction factor in
the turbulent flow regime instead of the implicit Colebrook equation on which
the Moody diagram is actually based. Over most of the range of validity, this
results in errors on the order of 1% or less. However, at a Reynolds number of
5000 and a relative roughness (e/D) of 0.01, an error of 2.8% occurs.

Potential Effectiveness as a Teaching Tool

Rating: 3.3 stars
Strengths: The calculator is based on one of the explicit relations for the friction factor
often used in fluid mechanics classes. It also includes tables for fluid
properties and typical surface roughness values for commonly used pipes and
ducts. Hence, it maybe used as a demonstration tool for lecture purposes.

Concerns: Although useful as a calculator, this object would be more useful as a teaching
tool if it included more background material, such as a discussion of the
Colebrook Equation on which the Moody diagram is based. It does, however,
provide a link to another page where the Colebrook Equation is at least given.

Ease of Use for Both Students and Faculty

Rating: 4.2 stars
Strengths: The calculator is both easy and intuitive to use, with little effort required to
begin using the calculator. Values may be entered in either English or SI
units as long as the units are employed consistently. It permits six different
combinations of user input data. Displaying the output values in blue and the
input values in black is a nice feature.

A useful addition to the calculator is a set of online tables for pertinent
fluid properties and pipe roughness values in both English and SI units.
Concerns: Users should be instructed to enter values for the kinematic viscosity and
surface roughness to replace the default values provided. Beginning students may
not be aware of this. For non-circular duct input, the user prompt
("Non-circular Duct: Enter A, P, and" ) is incomplete. Presumably it should
read: "Non-circular Duct: Enter A, P, and Q".

Other Issues and Comments: Overall, this calculator is quite useful and reasonably accurate for determining
friction factors for flows in pipes. However,its accuracy could be improved by
either using the implicit Colebrook equation with an iterative approach or by
using a more accurate explicit method.