ASHRAE Journal - October 2014 - 27

TECHNICAL FEATURE

Mixed Flow Temperature Calculations
Secondary Flow Greater Than Primary Flow (Table 1)
Analysis for "T-Connection A" Flow (Figure 2)
Secondary Supply Mixed Temperature (T2) Calculation
T1 = Primary Supply Flow Temperature
T2 = Secondary Supply Flow Temperature
T3 = Secondary Return Flow Temperature
T5 = Decoupler Flow Temperature
x1 = Fraction of Secondary Flow in Decoupler Piping

Primary Flow Greater Than Secondary Flow (Table 1)
Analysis for "T-Connection B" Flow (Figure 2)
Primary Return Mixed Temperature (T4) Calculation
T1 = Primary Supply Flow Temperature
T3 = Secondary Return Flow Temperature
T4 = Primary Return Flow Temperature
T5 = Decoupler Flow Temperature
x2 = Fraction of Primary Flow in Decoupler Piping

T2 = x1 × T5 + (1- x1) × T1

T4 = x2 × T5 + (1 - x2) × T3

T5 = T3

T5 = T1

T2 = x1 × T3 + (1 - x1) × T1 (Eq. 1)

T4 = x2 × T1 + (1 - x2) × T3 (Eq. 3)

T2 = x1 × T3 + T1 - x1 × T1
T2 = x1 × (T3 - T1) + T1
T2 - T1 = x1 × (T3 - T1)

T4 = x2 × T1 + T3 - x2 × T3
T4 = x2 × (T1 - T3) + T3
T4 - T3 = x2 × (T1 - T3)

x1 = (T2 - T1)/(T3 - T1) (Eq. 2)

x2 = (T3-T4)/(T3-T1) (Eq. 4)

Temperature Based Flow Approach

Primary Flow % Calculation

The temperature based flow approach uses mixed
temperature calculations at the decoupler piping
"T-Connection A" and "T-Connection B"(see sidebar,
"Mixed Flow Temperature Calculations").

The Primary Flow % calculated value is used to control primary pump variable frequency drive (VFD)
speeds and add additional chillers to meet secondary cooling load requirements while maintaining

www.info.hotims.com/49809-35
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ASHRAE JOURNAL

27



ASHRAE Journal - October 2014

Table of Contents for the Digital Edition of ASHRAE Journal - October 2014

Contents
ASHRAE Journal - October 2014 - Cover1
ASHRAE Journal - October 2014 - Cover2
ASHRAE Journal - October 2014 - 1
ASHRAE Journal - October 2014 - 2
ASHRAE Journal - October 2014 - Contents
ASHRAE Journal - October 2014 - 4
ASHRAE Journal - October 2014 - 5
ASHRAE Journal - October 2014 - 6
ASHRAE Journal - October 2014 - 7
ASHRAE Journal - October 2014 - 8
ASHRAE Journal - October 2014 - 9
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ASHRAE Journal - October 2014 - 11
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ASHRAE Journal - October 2014 - 13
ASHRAE Journal - October 2014 - 14
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ASHRAE Journal - October 2014 - 17
ASHRAE Journal - October 2014 - 18
ASHRAE Journal - October 2014 - 19
ASHRAE Journal - October 2014 - 20
ASHRAE Journal - October 2014 - 21
ASHRAE Journal - October 2014 - 22
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ASHRAE Journal - October 2014 - 24
ASHRAE Journal - October 2014 - 25
ASHRAE Journal - October 2014 - 26
ASHRAE Journal - October 2014 - 27
ASHRAE Journal - October 2014 - 28
ASHRAE Journal - October 2014 - 29
ASHRAE Journal - October 2014 - 30
ASHRAE Journal - October 2014 - 31
ASHRAE Journal - October 2014 - 32
ASHRAE Journal - October 2014 - 33
ASHRAE Journal - October 2014 - 34
ASHRAE Journal - October 2014 - 35
ASHRAE Journal - October 2014 - 36
ASHRAE Journal - October 2014 - 37
ASHRAE Journal - October 2014 - 38
ASHRAE Journal - October 2014 - 39
ASHRAE Journal - October 2014 - 40
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ASHRAE Journal - October 2014 - 49
ASHRAE Journal - October 2014 - 50
ASHRAE Journal - October 2014 - 51
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ASHRAE Journal - October 2014 - 55
ASHRAE Journal - October 2014 - 56
ASHRAE Journal - October 2014 - 57
ASHRAE Journal - October 2014 - 58
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ASHRAE Journal - October 2014 - 60
ASHRAE Journal - October 2014 - 61
ASHRAE Journal - October 2014 - 62
ASHRAE Journal - October 2014 - 63
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ASHRAE Journal - October 2014 - 65
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ASHRAE Journal - October 2014 - 70
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ASHRAE Journal - October 2014 - 73
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ASHRAE Journal - October 2014 - 76
ASHRAE Journal - October 2014 - 77
ASHRAE Journal - October 2014 - 78
ASHRAE Journal - October 2014 - 79
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ASHRAE Journal - October 2014 - 84
ASHRAE Journal - October 2014 - 85
ASHRAE Journal - October 2014 - 86
ASHRAE Journal - October 2014 - 87
ASHRAE Journal - October 2014 - 88
ASHRAE Journal - October 2014 - HR1
ASHRAE Journal - October 2014 - HR2
ASHRAE Journal - October 2014 - HR3
ASHRAE Journal - October 2014 - HR4
ASHRAE Journal - October 2014 - HR5
ASHRAE Journal - October 2014 - HR6
ASHRAE Journal - October 2014 - HR7
ASHRAE Journal - October 2014 - HR8
ASHRAE Journal - October 2014 - HR9
ASHRAE Journal - October 2014 - HR10
ASHRAE Journal - October 2014 - HR11
ASHRAE Journal - October 2014 - HR12
ASHRAE Journal - October 2014 - HR13
ASHRAE Journal - October 2014 - HR14
ASHRAE Journal - October 2014 - HR15
ASHRAE Journal - October 2014 - HR16
ASHRAE Journal - October 2014 - HR17
ASHRAE Journal - October 2014 - HR18
ASHRAE Journal - October 2014 - HR19
ASHRAE Journal - October 2014 - HR20
ASHRAE Journal - October 2014 - HR21
ASHRAE Journal - October 2014 - HR22
ASHRAE Journal - October 2014 - HR23
ASHRAE Journal - October 2014 - HR24
ASHRAE Journal - October 2014 - HR25
ASHRAE Journal - October 2014 - HR26
ASHRAE Journal - October 2014 - HR27
ASHRAE Journal - October 2014 - HR28
ASHRAE Journal - October 2014 - HR29
ASHRAE Journal - October 2014 - HR30
ASHRAE Journal - October 2014 - HR31
ASHRAE Journal - October 2014 - HR32
ASHRAE Journal - October 2014 - 89
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ASHRAE Journal - October 2014 - 104
ASHRAE Journal - October 2014 - Cover3
ASHRAE Journal - October 2014 - Cover4
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