Lohm Laws for Liquids - Examples of how to calculate flow resistance for liquids

Liquid Flow - Examples

Problem 1. A restrictor required to flow 0.1 GPM of 50/50 ethylene glycol/water blend at 45°F and 6 psid. How many Lohms are required?

Solution:
1. Read specific gravity; S= 1.07 from curve.
2. Read kinematic viscosity; n = 5.0 cs from curve.
3. Use n and DP to determine viscosity correction factor, V=.87, from curve.
4. Select unit constant K from table.
5. Compute Lohms required.



Problem 2. What pressure drop will result for a flow of 57 mL/min. of 50/50 ethylene glycol/water mixture at 45°F, flowing through a 1000 Lohm restrictor?

Solution:
1. Find specific gravity and viscosity: S = 1.07, v = 5 cs
2. Use knowledge of system to assume initial solution.
H = 4 psid
3. Use assumed H to determine V = 0.75 from curve.
4. Select units constant K from table.
5. Compute trial DP:


6. Make trials as required to find correct solution.
H = 2 psid V = .55
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