4 5
SELECTION CRITERIA FOR PRODUCTS
ed. 001-SP-ENG
SELECTION CRITERIA FOR PRODUCTS
ed. 001-SP-ENG
THE Kv FACTOR
The correct sizing of tubes and components of a
refrigerating system is of the utmost importance for all
kinds of plants; over-sizing and under-sizing are both
to be avoided since they are equally hazardous for the
correct operation of the system.
The correct selection of a component is based on the
knowledge of the relationship between capacity and
pressure drop through that component. For this purpose,
EN 60534-1, EN 60534-2-1 and EN 60534-2-3 standards
require manufacturers to specify the Kv coefficient for
every product.
The Kv factor is defined as the cold water flow
(volumic mass = 1000 kg/m
3
) in m
3
/h resulting in
a 1 bar pressure drop with a completely open valve.
This definition applies to all products described in this
handbook. The merely physical meaning, this coefficient
precisely defines the fluid-dynamic and construction
characteristics of the product, so that, with the addition of
other parameters more closely related to the nature and
conditions of the fluid under consideration, the capacity/
pressure drop ratio may be precisely determined.
Castel provides appropriate tables for the most
commonly used refrigerants in typical plant working
conditions in order to help engineers in the correct
selection of products. Tables 1 , 9 , 17 show refrigeration
capacity values with unit Kv related to the standard
rating conditions according to AHRI Standard 760-2007.
Appropriate corrective coefficients may be calculated
taking the values shown on tables 2-3-4-5-6-7-8 , 10-
11-12-13-14-15-16 , 18-19-20-21-22 as a basis ; this will
make it possible to predict actual working conditions.
As a result:
• Liquid line in HFC, HFO, HFC, CO
2
subcritical systems
• Q = Kv x Q
1
x L
1
x L
2
x L
3
• Suction line in HFC, HFO, HFC, CO
2
subcritical systems
• Q = Kv x Q
1
x S
1
x S
2
x S
3
• Hot gas line in HFC, HFO, HFC, CO
2
subcritical systems
• Q = Kv x Q
1
x H
1
x H
2
x H
3
• Gas cooling line in transcritical CO
2
systems:
• Q = Kv x Q
1
x L
1
x L
2
• Suction line in transcritical CO
2
systems
• Q = Kv x Q
1
x S
1
x S
2
• Hot gas line in transcritical CO
2
systems
• Q = Kv x Q
1
x H
1
x H
2
since:
Q = required refrigeration capacity [kW]
Kv = characteristic valve coefficient [m
3
/h]
Q
1
= reference refrigeration capacity [kW]
L
1
; S
1
; H
1
= correction factors of the refrigeration
capacity for operating temperatures different from
reference conditions
L
2
; S
2
; H
2
= correction factors of the refrigeration
capacity for pressure drops different from reference
conditions
L
3
; S
3
; H
3
= correction factors of the refrigeration capacity
for subcooling different from reference conditions
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