McQuay AC 40A, Applications Manual

Page: 101 / 189

Example of Selection:
The mini chiller has a piping network of diameter 1-1/4". The pipes are to be insulated with
Armaflex. The pipes run through a ceiling space with a temperature of 38°C and 85% RH.
Determine the minimum insulation thickness required to prevent condensation if the chilled water
temperature is at:
a. 7°C
b. 2 °C
The Armaflex insulation has a k-value of 0.0374 W/m.K. The tubular insulation has a black
surface, thereby use a h-value of 9 W/m.K. By entering into the sizing Excel spreadsheet
programme,
we calculate:
1. For a 7°C water temperature, the insulation must be at least 1 inch thick.
2. For a 2°C water temperature, the thickness required is 1.1 inch.
It is recommended that the next size up to be selected to provide some safety factor for the
selection.
If a pre-insulated pipe is used instead, what is the thickness required?
Ignoring the effect of the external cladding, and entering again into the programme with a k-value
of 0.025 W/m.K, we have the minimum thickness:
1. For 7°C water: 0.7 inch
2. For 2°C water: 0.8 inch
Note that polyurethane is a better thermal insulator compared with the Armaflex, therefore the
thickness
is lower.
Section 7 Page 99