ISO/DIS 21773

Method of test and characterization of performance for energy recovery components

Méthode d'essai et caractérisation des performances des composants récupérateurs d’énergie

Standards Content (sample)

DRAFT INTERNATIONAL STANDARD
ISO/DIS 21773
ISO/TC 86/SC 6 Secretariat: ANSI
Voting begins on: Voting terminates on:
2019-12-03 2020-02-25
Method of test and characterization of performance for
energy recovery components

Méthode d'essai et caractérisation des performances des composants récupérateurs d’énergie

ICS: 23.120; 91.120.10
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
This document is circulated as received from the committee secretariat.
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STANDARDS MAY ON OCCASION HAVE TO
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WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 21773:2019(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
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PROVIDE SUPPORTING DOCUMENTATION. ISO 2019
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ISO/DIS 21773:2019(E)
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ISO/DIS 21773:2019(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 4

5 Metrics ............................................................................................................................................................................................................................. 5

5.1 Effectiveness ............................................................................................................................................................................................. 5

5.2 Pressure drop ........................................................................................................................................................................................... 6

5.2.1 Measured pressure drop ........................................................................................................................................... 6

5.2.2 Standardized pressure drop .................................................................................................................................. 6

5.3 Recovery Efficiency Ratio .............................................................................................................................................................. 7

5.4 Outside Air Correction Factor .................................................................................................................................................... 7

5.5 Exhaust Air Transfer Ratio............................................................................................................................................................ 8

5.6 Sensible energy transfer rate for the supply airstream ....................................................................................... 8

5.7 Humidity transfer rate for the supply airstream ....................................................................................................... 8

6 General test requirements ......................................................................................................................................................................... 8

6.1 Test apparatus ......................................................................................................................................................................................... 8

6.2 Installation .................................................................................................................................................................................................. 8

6.3 Static Pressures ...................................................................................................................................................................................... 9

6.4 Instrument Calibration .................................................................................................................................................................... 9

7 Effectiveness tests ............................................................................................................................................................................................10

7.1 Test requirements .............................................................................................................................................................................10

7.2 Stability limits when testing effectiveness ...................................................................................................................10

7.3 Data collection period ....................................................................................................................................................................11

7.4 Data sampling rates .........................................................................................................................................................................11

7.5 Temperature and humidity conditions: inlets to exchanger ........................................................................11

7.6 Test temperature limits ................................................................................................................................................................12

8 Pressure drop tests .........................................................................................................................................................................................12

9 Leakage tests .........................................................................................................................................................................................................12

9.1 General Test Requirements .......................................................................................................................................................12

9.2 Outside Air Correction Factor .................................................................................................................................................12

9.3 Exhaust Air Transfer Ratio.........................................................................................................................................................13

10 Uncertainty Limits ...........................................................................................................................................................................................13

10.1 Uncertainty limits for effectiveness tests ......................................................................................................................13

10.2 Uncertainty limits for RER .........................................................................................................................................................13

10.3 Uncertainty limits for measured pressure drop tests ........................................................................................13

10.4 Uncertainty limits for leakage tests ...................................................................................................................................14

11 Inequality limits .................................................................................................................................................................................................14

11.1 Inequality limits for thermal tests.......................................................................................................................................14

11.2 Inequality limits for leakage tests .......................................................................................................................................14

12 Reporting of Test Results ..........................................................................................................................................................................15

12.1 Pressure drop test results ..........................................................................................................................................................15

12.2 Leakage test results .........................................................................................................................................................................15

12.3 Thermal test results .........................................................................................................................................................................15

12.4 Uncertainties .........................................................................................................................................................................................15

Annex A (informative) Example of test data collection and calculation of metrics ..........................................16

Annex B (informative) Best Practices ...............................................................................................................................................................20

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ISO/DIS 21773:2019(E)

Annex C (informative) Expression of performance metrics for use in calculation of system

performance ......... ..................................................................................................................................................................................................27

Annex D (informative) Inequality limits for use when condensate flow rate can be measured ..........31

Bibliography .............................................................................................................................................................................................................................32

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ISO/DIS 21773:2019(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,

as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the

Technical Barriers to Trade (TBT) see the following URL: www .iso .org/iso/foreword .html.

The committee responsible for this document is Technical Committee ISO/TC 86, Refrigeration and air-

conditioning, Subcommittee SC 6, Testing and rating of air-conditioners and heat pumps.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
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ISO/DIS 21773:2019(E)
Introduction
[TBC]
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DRAFT INTERNATIONAL STANDARD ISO/DIS 21773:2019(E)
Method of test and characterization of performance for
energy recovery components
1 Scope

This standard prescribes the methods for testing the performance of air-to-air heat/energy exchangers

when used as devices to transfer heat or heat and water vapor between two airstreams used in

ventilation systems. This standard prescribes methods to characterize the performance of exchangers

for use in calculation of the energy performance of buildings. The types of air-to-air heat/energy

exchangers covered by this standard are:
a. fixed-plate exchangers [also known as recuperators],

b. rotary exchangers, including heat wheels and total energy wheels [also known as regenerators],

c. heat pipe exchangers using a heat transfer medium, excluding those using mechanical pumping,

This standard does not provide a method for measuring the response of exchangers to the formation

of frost.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ASHRAE 84-2020Method of Testing Air-to-Air Heat/Energy Exchangers.

ISO 3966:2008, Measurement of fluid flow in closed conduits — Velocity area method using Pitot static tubes

ISO 5167-1:2003, Measurement of fluid flow by means of pressure differential devices inserted in circular

cross-section conduits running full — Part 1: General principles and requirements

ISO/TR 9464:2008, Guidelines for the use of ISO 5167:2003

ISO/TR 5168:2015, Measurements of fluid flow procedures for the evaluation of uncertainty

ISO 5801:2017, Fans — Performance testing using standardized airways

ISO 13253:2017, Ducted air-conditioners and air-to-air heat pumps — Testing and rating for performance

ISO/IEC 17025:2017, General requirements for the competence of testing and calibration laboratories

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at http: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
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ISO/DIS 21773:2019(E)
3.1
effectiveness

the actual energy transfer rate (sensible, latent, or total) divided by the maximum possible energy

transfer rate.
Note 1 to entry: the equation for effectiveness is given in (5.1).
3.2
exhaust air transfer ratio (EATR)

the tracer gas concentration difference between the supply air outlet and the supply air inlet, divided

by the tracer gas concentration difference between the exhaust air inlet and the supply air inlet which

quantifies the air quantity transferred from the exhaust to the supply.
Note 1 to entry: the equation for exhaust EATR is given in (5.5).

Note 2 to entry: may be expressed as a percentage for rating purposes but is used as a ratio in the calculation of RER.

3.3
fixed-plate exchanger

an exchanger with multiple alternate airflow channels, separated by a heat or heat and water vapor

transfer plate(s) and connected to supply and exhaust airstreams.
3.4
heat pipe exchanger

an exchanger with an array of finned and sealed tubes that are placed in side-by-side supply and

exhaust airstreams, which may include an internal wick structure in each tube, and filled with a heat

transfer medium.

Note 1 to entry: thermosiphon exchangers are a subset (or type) of heat pipe exchanger in which the heat transfer

medium moves by gravitational forces only.
3.5
outside air correction factor (OACF)

a factor defined as the entering supply airflow divided by the leaving supply airflow.

Note 1 to entry: the equation for OACF is given in (5.4).
3.6
recovery efficiency ratio (RER)

a ratio of the recovered energy rate divided by the sum of the calculated combined fan power and the

auxiliary power.
Note 1 to entry: the equation for RER is given in (5.3).

Note 2 to entry: RER can be characterized as gross, or as net in which case EATR is accounted for.

3.7
rotary exchanger

an exchanger with porous discs, fabricated from materials with heat or heat and water vapor retention

capacity, that are regenerated by collocated supply and exhaust airstreams.
3.8
standard air (SI units)
3 -5

dry air with a density of 1.2043 kg/m , and dynamic viscosity of 1.8247 x 10 kg/(m∙s).

Note 1 to entry: These conditions approximate dry air at 20°C and 101.3250 kPa absolute

3.9
station

location in the test apparatus at which conditions such a temperature, humidity, pressure, or airflows

are measured.
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ISO/DIS 21773:2019(E)
3.10
static pressure differential
static pressure at supply outlet less the static pressure at exhaust inlet.

Note 1 to entry: a positive pressure differential occurs when the static pressure at station 2 is higher than the

static pressure at station 3. A negative pressure differential occurs when the station 2 static pressure is lower

than the station 3 static pressure.
3.11
Entering Supply Air
outside air entering the Exchanger.
Note 1 to entry: indicated in Figure 1 as 1.
Note 2 to entry: sometimes referred to as the Outdoor Airflow (OA).
Note 3 to entry: sometimes referred to as the Supply air inlet
3.12
Leaving Supply Air
outside air after passing through the Exchanger.
Note 1 to entry: indicated in Figure 1 as 2.
Note 2 to entry: sometimes referred to as the Supply Airflow (SA).
Note 3 to entry: sometimes referred to as the Supply air outlet.
3.13
Entering Exhaust Air
indoor air entering the Exchanger.
Note 1 to entry: indicated in Figure 1 as 3.
Note 2 to entry: sometimes referred to as the Return Airflow (RA).
Note 3 to entry: sometimes referred to as the Exhaust air inlet.
3.14
Leaving Exhaust Air
indoor air after passing through the Exchanger.
Note 1 to entry: indicated in Figure 1 as 4.
Note 2 to entry: sometimes referred to as the Exhaust Airflow (EA).
Note 3 to entry: sometimes referred to as the Exhaust air outlet
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ISO/DIS 21773:2019(E)
Key
1 entering supply air 2 leaving supply air
3 entering exhaust air 4 leaving exhaust air
5 exchanger
Figure 1 — Schematic diagram of airflows for heat and energy recovery exchangers
4 Symbols and abbreviated terms
Symbol Term Units
e Effectiveness %
ṁ mass flow rate of dry air at Station 1, 2, 3 or 4 kg/s
1,2,3,4
NOTE 1
EATR Exhaust air transfer ratio 1
RER Recovery efficiency ratio W/W
NOTE
OACF Outside air correction factor 1
T Dry bulb temperature at Station1, 2, 3 or 4 °C
1,2,3,4
T Wet bulb temperature at Station1, 2, 3 or 4 °C
WB,1,2,3,4
T The average value of temperature readings at a measurement station for °C
AVE
purposes of determining effectiveness.
W Humidity at Station 1, 2, 3 or 4 kg water/kg dry
1,2,3,4
air

W The average value of humidity readings at a measurement station for purpos- kg water/kg dry

AVE
es of determining effectiveness. air
h heat of vaporization of water, J/kg
Q Leaving supply volume flow rates m /s
Q Entering exhaust volume flow rates m /s
Q Sensible Energy Transfer Rate W
sensible
Q Humidity Transfer Rate kg water/(kg dry
latent
air ∙ s)
Q Total Energy Transfer Rate W
total
Ps Static pressure at station 1, 2, 3 or 4 Pa
1,2,3,4
DP Pressure Drop through the exchanger, exhaust air stream, measured Pa

NOTE Some quantities of dimension 1 are defined as ratios of two quantities of the same kind. The coherent derived unit

is the number 1. (ISO 80000-1:2009, 3.8).
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ISO/DIS 21773:2019(E)
Symbol Term Units
DP Pressure Drop through the exchanger, supply air stream, measured Pa
DP Pressure Drop through the exchanger, exhaust air stream, at reference Pa
e,ref
conditions
DP Pressure Drop through the exchanger, supply air stream, at reference Pa
s,ref
conditions
ρ dry air density at station 1, 2, 3 or 4 kg/m
1,2,3,4
q Auxiliary power input to the exchanger (e.g. to rotate a wheel) W
aux
NOTE
η Combined efficiencies of the supply and exhaust air fan and drive 1
fs,fe
DT Temperature change in the supply airstream °C or K
1-2
DW Humidity change in the supply airstream kg water / kg dry
1-2
air
c specific heat of dry air at station 1, 2, 3 or 4 J/(kg⋅K)
p,1,2,3,4
H Enthalpy of air at station 1, 2, 3 or 4 kJ/kg dry air
1,2,3,4
C Tracer gas concentration at station 1, 2, 3 or 4 10
1,2,3,4

NOTE Some quantities of dimension 1 are defined as ratios of two quantities of the same kind. The coherent derived unit

is the number 1. (ISO 80000-1:2009, 3.8).
Subscript Description
Indicates parameter refers to sensible energy
sensible
Indicates parameter refers to latent energy
latent
Indicates parameter refers to total (enthalpic) energy
total
Refers to stations 1, 2, 3 or 4
1, 2, 3, 4
Supply fan, exhaust fan
fs, fe
Process or change in the outside airstream between entering and leaving
1-2
Process or change in the exhaust airstream between entering and leaving
3-4
Supply, exhaust
s, e
m the lesser of ṁ and ṁ
min 2 3
5 Metrics

The performance of an air-to-air heat/energy exchanger is primarily characterized by its sensible,

latent, and total effectiveness (see Formulae [1],[2] and,[3] its pressure drops (see Formulae [4], [5], [6]

and [7]), its recovery efficiency ratio (see Formulae [8] and [9]), the outside air correction factor (see

Formula [10]), and its exhaust air transfer ratio (see Formula [11]).

Derived metrics that are needed for use in calculating the performance of complete systems include

sensible energy transfer rate (see Formula [12]), humidity transfer rate (see Formula [13]) and enthalpy

transfer rate (see Formula [14]).
5.1 Effectiveness
mC TC− T
21pp,,12 2
ε = [1]
sensible
mC TC− T
minp,,11 p 33
mh Wh− W
21fg,,12fg 2
ε = [2]
latent
mh Wh− W
minfgf,,11 g 33
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ISO/DIS 21773:2019(E)
mh −h
21 2
ε = [3]
total
mh −h
min 13
where
ṁ mass flow rate at station 1, 2 or 3
1,2,3
ṁ the lesser of ṁ and ṁ
min 2 3
C specific heat of dry air at station 1, 2 or 3
p,1,2,3
h heat of vaporization of water at station 1, 2 or 3
fg, 1,2,3
T dry bulb temperature at station 1, 2 or 3
1,2,3
W humidity at station 1, 2 or 3
1,2,3
h enthalpy at station 1, 2 or 3
1,2,3
5.2 Pressure drop
5.2.1 Measured pressure drop

The air friction pressure drops (DP and DP ) at specific conditions and air mass flow rate through the

s e
exchanger are defined by:
Δ=Ppsp− s [4]
s 12
Δ=Ppsp− s [5]
e 34
where
ps static pressure at station 1, 2, 3 or 4
1,2,3,4
5.2.2 Standardized pressure drop
Air friction pressure drops at reference conditions may be determined by:
ρ μ ρ μ
     
1 s 2 s
Δ=Ppsp− s [6]
     
sr,1ef 2
ρ μ ρ μ
   
 s  1  s  2
 ρ  μ   ρ  μ 
3 s s
Δ=Ppsp− s [7]
     
er,3ef 4
ρ μ ρ μ
     
s 3 s 4
where
ρ density at station 1, 2, 3 or 4
1,2,3,4
ρ standard density of air = 1.2043 kg/m
μ dynamic viscosity at station 1, 2, 3 or 4
1,2,3,4
μ dynamic viscosity of standard air = 1.8247 x 10 kg/(m∙s)
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ISO/DIS 21773:2019(E)
5.3 Recovery Efficiency Ratio

a. Determination of the gross recovery efficiency ratio (RER ) of a heat/energy exchanger is defined

gross
by the formula:
mh −h
21 2
RER = [8]
gross
ΔPQ ΔPQ
s 23e
+ +q
aux
fans,,fane

b. Determination of the net recovery efficiency ratio (RER ) of a heat/energy exchanger is defined by

net
the formula:
hE−()ATRh
mh −
()1−EATR
RER = [9]
net
ΔPQ ΔPQ
s 23e
+ +q
auux
fans,,fane
where

ΔP and ΔP the measured pressure drops across the supply and exhaust sides of the exchanger,

s e
respectively
Q and Q the leaving supply and entering exhaust volume flow rates,
2 3
η and η supply and exhaust air fan and drive combined efficiencies (see Note).
fs fe

q the total auxiliary power input to the exchanger (e.g., to rotate a regenerative wheel,

aux.
a pump, and to operate controls)
Note 1 to entry EATR must be expressed as a ratio in the above formula.

Note In laboratory testing of heat/energy exchangers it is not usually possible to measure the power

required to move air through the exchanger directly, as the blowers in the test system also are required to

overcome friction pressure of the conditioning equipment, flow measurement equipment, and etc. Therefore,

the power required to move air through the exchanger must be calculated, based on a reference fan and drive

total efficiency which is selected for the purposes of comparison of one exchanger to another. For example, a

performance rating agency could elect to use a reference fan and drive total efficiency of 0.50 in calculation of

RER for all the exchangers for which it provides ratings.
5.4 Outside Air Correction Factor

The outside air correction factor (OACF) of a heat/energy exchanger at a specific operating condition is

defined by the formula:
OACF= [10]
where
ṁ are the mass flow rates at stations 1 and 2
1,2
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ISO/DIS 21773:2019(E)
5.5 Exhaust Air Transfer Ratio

The exhaust air transfer ratio (EATR) of a heat/energy exchanger at a specific operating condition is

defined by the formula:
CC−
EATR= [11]
CC−

where C is the concentration of tracer gas at stations 1, 2 and 3 during the test described in 9.3.

1,2,3

Note 1 to entry to express exhaust air transfer ratio as a percentage, multiply by 100.

5.6 Sensible energy transfer rate for the supply airstream

Sensible energy transfer rate into or out of the supply airstream for an exchanger at a specific operating

condition is defined by the formula:
Qm=−⋅ Tc Tc [12]
sensible 21 pp,,12 2
5.7 Humidity transfer rate for the supply airstream

Humidity transfer rate into or out of the supply airstream for an exchanger at a specific operating

condition is defined by the formula:
Qm=⋅ΔW [13]
latent 21−2
where
ΔW is the humidity change for the supply airstream
1-2
Total energy transfer rate for the supply airstream

Total energy transfer rate into or out of the supply airstream for an exchanger at a specific operating

condition is defined by the formula:
Qm=⋅Δh [14]
total 21−2
where
Δh is the enthalpy change for the supply airstream
1-2
6 General test requirements
6.1 Test apparatus

The test apparatus shall consist of four measurement stations. Measurements shall be taken at each

station of temperature, humidity, dry air mass flow rate, tracer gas concentration, and static pressure.

6.2 Installation

Equipment to be tested shall be installed in accordance with the manufacturer’s instructions

Note 1 to entry See Annex B for best practices of connecting exchanger to test system.

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ISO/DIS 21773:2019(E)
6.3 Stati
...