ENV 12977-3:2001

SLOVENSKI STANDARD
SIST ENV 12977-3:2002
01-november-2002
7RSORWQLVRQþQLVLVWHPLLQVHVWDYQLGHOL1HVHULMVNRL]GHODQLVLVWHPLGHO
'RORþDQMH]QDþLOQRVWLKUDQLOQLNRYWRSORWH]DVLVWHPHRJUHYDQMDVVRQFHP
Thermal solar systems and components - Custom built systems - Part 3: Performance
characterisation of stores for solar heating systems
Thermische Solaranlagen und ihre Bauteile - Kundenspezifisch gefertigte Anlagen - Teil
3: Leistunsprüfung von Warmwasserspeichern für Solaranlagen
Installations solaires thermiques et leur composants - Installations assemblées a façon -
Partie 3: Caractérisation des performances des dispositifs de stockage pour des
installations de chauffage solaire
Ta slovenski standard je istoveten z: ENV 12977-3:2001
ICS:
27.160 6RQþQDHQHUJLMD Solar energy engineering
91.140.10 Sistemi centralnega Central heating systems
ogrevanja
91.140.65 Oprema za ogrevanje vode Water heating equipment
SIST ENV 12977-3:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST ENV 12977-3:2002

---------------------- Page: 2 ----------------------

SIST ENV 12977-3:2002
EUROPEAN PRESTANDARD
ENV 12977-3
PRÉNORME EUROPÉENNE
EUROPÄISCHE VORNORM
April 2001
ICS 27.160; 91.140.10; 91.140.65
English version
Thermal solar systems and components - Custom built systems
- Part 3: Performance characterisation of stores for solar heating
systems
Installations solaires thermiques et leur composants - Thermische Solaranlagen und ihre Bauteile -
Installations assemblées à façon - Partie 3: Caractérisation Kundenspezifisch gefertigte Anlagen - Teil 3:
des performances des dispositifs de stockage pour des Leistunsprüfung von Warmwasserspeichern für
installations de chauffage solaire Solaranlagen
This European Prestandard (ENV) was approved by CEN on 12 March 2001 as a prospective standard for provisional application.
The period of validity of this ENV is limited initially to three years. After two years the members of CEN will be requested to submit their
comments, particularly on the question whether the ENV can be converted into a European Standard.
CEN members are required to announce the existence of this ENV in the same way as for an EN and to make the ENV available promptly
at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the ENV) until the final
decision about the possible conversion of the ENV into an EN is reached.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. ENV 12977-3:2001 E
worldwide for CEN national Members.

---------------------- Page: 3 ----------------------

SIST ENV 12977-3:2002
Page 2
ENV 12977-3:2001
Contents
Page
Foreword . 3
Introduction. 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Symbols and abbreviations . 10
5 Store classification. 11
6 Laboratory store testing. 11
7 Store test combined with a system test according to ISO 9459-5 . 51
8 Test report . 51
Annex A (normative) Requirements for the numerical store model . 54
Annex B (normative) Store model benchmark tests . 56
Annex C (normative) Benchmarks for the parameter identification . 58
Bibliography. 60

---------------------- Page: 4 ----------------------

SIST ENV 12977-3:2002
Page 3
ENV 12977-3:2001
Foreword
This European Prestandard has been prepared by Technical Committee CEN/TC 312
"Thermal solar systems and components", the secretariat of which is held by ELOT.
According to the CEN/CENELEC Internal Regulations, the national standards
organizations of the following countries are bound to announce this European
Prestandard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany,
Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain,
Sweden, Switzerland and the United Kingdom.
The annexes A, B and C are normative.
Introduction
The test methods for stores of solar heating systems as described in this Prestandard
are required for the determination of the thermal performance of small custom built
systems as specified in ENV 12977-1.
These test methods deliver parameters, which are needed for the simulation of the
thermal behaviour of a store being part of a small custom built system.
NOTE 1 For additional information about the test methods for the performance characterization of
stores see
1 in Bibliography.
NOTE 2 With the test methods for stores given in prEN 12897:1997 only a few parameters are
determined in order to characterise the thermal behaviour of a store. These few parameters are not
sufficient for the determination of the thermal performance of small custom built systems as described in
ENV 12977-2.
This is due to the fact that the performance of thermal solar systems depends much more on the
thermal behaviour of the store (e. g. stratification, heat losses), as conventional systems do. Hence this
separate Prestandard for the performance characterisation of stores for solar heating systems is
needed.

---------------------- Page: 5 ----------------------

SIST ENV 12977-3:2002
Page 4
ENV 12977-3:2001
1 Scope
This Prestandard specifies test methods for the performance characterization of
stores which are intended for use in small custom built systems as specified in
ENV 12977-1.
Stores tested according to this Prestandard are commonly used in solar hot water
systems. However, also the thermal performance of all other thermal stores with water
as storage medium (e.g. for heat pump systems) can be assessed according to this
Prestandard.
The Prestandard applies to stores with a nominal volume between 50 and 3000 litres
and without integrated oil or gas burner.
2 Normative references
This European Prestandard incorporates, by dated or undated reference, provisions
from other publications. These normative references are cited at the appropriate
places in the text and the publications are listed hereafter. For dated references,
subsequent amendments to or revisions of any of these publications apply to this
European Prestandard only when incorporated in it by amendment or revision. For
undated references the latest edition of the publication referred to applies.
EN 12976-2:2000 Thermal solar systems and components - Factory made
systems - Test Methods
ENV 12977-2:2001 Thermal Solar Systems and Components – Custom Built
Systems – Test Methods
prEN 12828:1997 Heating systems in buildings – Design and installation of water
heating systems
prEN 12897:1997 Water supply – Specification for indirectly heated unvented
(closed) hot water storage systems
EN ISO 9488 Solar energy – Vocabulary (ISO 9488:1999)
ISO 9459-5 Solar heating – Domestic water heating systems – Part 5:
System performance characterization by means of whole –
system tests and computer simulation
3 Terms and definitions
For the purposes of this European Prestandard the following terms and definitions together
with EN ISO 9488 apply.
3.1
ambient temperature
mean value of the temperature of the air surrounding the store
3.2
charge
process of transferring energy into the store by means of an heat source

---------------------- Page: 6 ----------------------

SIST ENV 12977-3:2002
Page 5
ENV 12977-3:2001
3.3
charge connection
pipe connection used for charging the storage device
3.4
combistore
store used for both domestic hot water preparation and space heating
3.5
~

constant inlet temperature ( )
x,i
temperature which is achieved during charge (x=C) or discharge (x=D), if the mean
~

value over the period of 0,5 reduced charge / discharge volumes (see 3.34) is within
x,i
~
o
(  1) C

x,i
3.6
~


constant flow rate (V )
~


flow rate which is achieved, when the mean value V over the period of 0,5 reduced charge
~


/ discharge volumes (see 3.34) is within V 10 %
3.7
~
constant charge power (P )
C
charge power which is achieved, when the mean value P over the period of 0,5 reduced
C
~
charge volumes is within P  10 %
C
3.8
conditioning
process of creating a uniform temperature inside the store by
~
o
discharging the store with  = 20 C until a steady state is reached
D,i
NOTE The conditioning at the beginning of a test sequence is intended to provide a well defined
initial system state, i. e. an uniform temperature in the entire store.
3.9
discharge connection
pipe connection used for discharging the storage device
3.10
dead volume / dead capacity
the volume / capacity of the store which is only heated due to heat conduction (e. g.
below a heat exchanger)

---------------------- Page: 7 ----------------------

SIST ENV 12977-3:2002
Page 6
ENV 12977-3:2001
3.11
direct charge / discharge
transfer or removal of thermal energy in or out of the store, by directly exchanging the
fluid in the store
3.12
discharge
process of decreasing thermal energy inside the store caused by the hot water load
3.13
double port
a corresponding pair of inlet and outlet connections for direct charge / discharge of the
store
NOTE Often, the store is charged or discharged via closed or open loops that are
connected to the store through double ports.
3.14
effective volume / effective capacity
the volume / capacity which is involved in the heat storing process if the store is
operated in a usual way
3.15
electrical (auxiliary) heating
electrical heating element immersed into the store
3.16
external auxiliary heating
auxiliary heating device located outside the store. The heat is transferred to the store
by direct or indirect charging via a charge loop. The external auxiliary heating is not
considered as part of the store under test
3.17
( )
heat loss capacity rate UA
s,a
the overall heat loss of the entire storage device per K temperature difference
between the store temperature and the ambient air temperature
NOTE The heat loss capacity rate depends on the flow conditions inside the store. Hence a
stand-by heat loss capacity rate and a operating heat loss capacity rate are defined. If (UA) is
s,a
mentioned without specification, (UA) represents the stand-by heat loss capacity rate.
s,a
3.18
heat transfer capacity rate
the thermal power transferred per K temperature difference

---------------------- Page: 8 ----------------------

SIST ENV 12977-3:2002
Page 7
ENV 12977-3:2001
3.19
immersed heat exchanger
heat exchanger which is completely surrounded with the fluid in the store tank
3.20
indirect charge / discharge
transfer or removal of thermal energy into or out of the store, via a heat exchanger
3.21
load
the heat output of the store during discharge. The load is defined as the product of the
mass, specific thermal capacity and temperature increase of the water as it passes
the solar hot water system
3.22
mantle heat exchanger
heat exchanger mounted to the store in a way, that it forms a layer between the fluid
in the store tank and ambient
3.23
measured store heat capacity
the measured difference in energy of the store between two steady states on different
temperature levels, divided by the temperature difference between this two steady
states
3.24
measured energy (Q )
x,m
time integral of the measured power over one or more test sequences, excluding time
periods used for conditioning at the beginning of the test sequences
3.25
measured power (P )
x,m
power calculated from measured volume flow rate as well as measured inlet and outlet
temperature
3.26
mixed
state when the local store temperature is not a function of the vertical store height
3.27
model parameter
parameter used for quantification of a physical effect, if this physical effect is
implemented in a mathematical model in a way which is not analogous to its

---------------------- Page: 9 ----------------------

SIST ENV 12977-3:2002
Page 8
ENV 12977-3:2001
appearance in reality, or if several physical effects are lumped in the model (e. g. a
stratification number)
3.28


nominal flow rate ( V )
n
the nominal volume of the entire store divided by 1 h
3.29
nominal heating power (P )
n
the nominal volume of the entire store multiplied by 10 W/l
3.30
nominal volume (V )
n
fluid volume of the store as specified by the manufacturer
3.31
operating heat loss capacity rate (UA)
op,s,a
heat loss capacity rate of the store during charge or discharge
3.32
predicted energy (Q )
x,p
time integral of the predicted power over one or more test sequences, excluding time
periods used for conditioning at the beginning of the test sequences
3.33
predicted power (P )
x,p
power calculated from measured volume flow rate, as well as measured inlet
temperature and calculated outlet temperature. The outlet temperature is predicted by
numerical simulation
3.34
reduced charge / discharge volume
integral of a charge / discharge flow rate divided by the store volume
3.35
stand-by
state of operation in which no energy is deliberately transferred to or removed from the
store
3.36
stand-by heat loss capacity rate (UA)
sb,s,a
heat loss capacity rate of the store during stand-by

---------------------- Page: 10 ----------------------

SIST ENV 12977-3:2002
Page 9
ENV 12977-3:2001
3.37
steady state
state of operation at which at charge or discharge during 0,5 reduced charge /
discharge volume (see 3.34) the standard deviation of the temperature difference,
between store inlet and store outlet temperature of the charging / discharging circuit is
lower than 0,05 K
NOTE In cases of an isothermal charged store rather constant temperature differences
between the inlet and outlet temperature of the discharge circuit may occur during the discharge of the
first store volume before the outlet temperature drops rapidly. These state is not considered as steady
state.
3.38
store temperature
temperature of the store medium
3.39
stratified
state when thermal stratification is inside the store
3.40
stratified charging
increase of thermal stratification in the store during charging
3.41
stratifier
device that enables stratified charging of the store. Common used stratifiers are e.g.
convection chimneys or pipes with radial holes
3.42
theoretical store heat capacity

the sum over all thermal capacities m  c of the entire store (fluid, tank material,
i p,i
heat exchangers) having part of the heat store process
3.43
thermal stratification
state when the local store temperature is a function of the vertical store height, with
the temperature decreasing from top to bottom
3.44
transfer time (t )
x,f
time period during which energy is transferred through the connections for charge
(x=C) or discharge (x=D). The transfer time is calculated over one or more test
sequences, excluding time periods used for conditioning at the beginning of the test
sequences

---------------------- Page: 11 ----------------------

SIST ENV 12977-3:2002
Page 10
ENV 12977-3:2001
4 Symbols and abbreviations
C thermal capacity of the entire store, in J/K
s
c specific heat capacity, in J/(kg K)
p
P nominal heating power, in W
n
P measured power transferred through the charge (x=C) or discharge (x=D)
x,m
circuit, in W
P predicted power transferred through the charge (x=C) or discharge (x=D)
x,p
circuit, in W
Q measured energy transferred through the charge (x=C) or discharge (x=D)
x,m
circuit, in J
Q predicted energy transferred through the charge (x=C) or discharge (x=D)
x,p
circuit, in J
t time required to achieve a steady state, in s
st
t transfer time for charging (x=C) or discharging (x=D) , in s
x,f
o

ambient temperature, in C
a
o

store temperature, in C
s
 o

inlet temperature of the charge (x=C) or discharge (x=D) circuit, in C
x,i

constant inlet temperature of the charge (x=C) or discharge (x=D) circuit, in
x,i
o
C
o

outlet temperature of the charge (x=C) or discharge (x=D) circuit, in C
x,o
(UA) heat transfer capacity rate between heat exchanger and store, in W/K
hx,s
(UA) heat loss capacity rate of the store, in W/K
s,a
(UA) operating heat loss capacity rate of the store, in W/K
op,s,a
(UA) stand-by heat loss capacity rate of the store, in W/K
sb,s,a
V nominal volume of the store, in l
n


V nominal flow rate, in l/h
n
~


V constant flow rate of the charge (x=C) or discharge (x=D) circuit, in l/h
x

mean logarithmic temperature difference, in K
m
 relative error in mean power transferred during charge (x=C) or discharge
x,P
(x=D), in %
 relative error in energy transferred during charge (x=C) or
x,Q
discharge (x=D), in %
3
 density, in kg/m

---------------------- Page: 12 ----------------------

SIST ENV 12977-3:2002
Page 11
ENV 12977-3:2001
5 Store classification
Hot water stores are classified by distinction between different charge and discharge
modes. Five groups are defined as shown in Table 1.
Table 1 - Classification of the stores
Group charge mode discharge mode
1 direct direct
2 indirect direct
3 direct indirect
4 indirect indirect
5 stores that cannot be assigned to groups 1 to 4
NOTE 1 All stores may have one or more additional electrical heating elements.
NOTE 2 Stores that can be charged or discharged directly and indirectly (e. g. a store of a
space heating system with an internal heat exchanger for the preparation of domestic hot water) can
belong to more than one group. In this case the appropriate test procedures or the assignment to one of
the groups respectively, shall be chosen depending on its mode of operation.
6 Laboratory store testing
6.1 Requirements on the testing stand
6.1.1 General
The hot water store shall be tested separately from the whole solar system on a store
testing stand.
The testing stand configuration shall be determined by the classification of hot water
stores as described in clause 5.
An example of a representative hydraulic testing stand configuration is shown in
Figure 1 and Figure 2.
The circuits are intended to simulate the charge and discharge loop of the solar
system and to provide fluid flow with a constant or well controlled temperature. The full
test stand consists of one charge and one discharge circuit.
NOTE 1 If the store consists of more than one charge or discharge devices (e.g. two heat
exchangers), then these are tested separately.

---------------------- Page: 13 ----------------------

SIST ENV 12977-3:2002
Page 12
ENV 12977-3:2001
The testing stand shall be located in an air-conditioned room where the room
o
temperature of 20 C should not vary more than 1 K during the test.

Both circuits shall fulfil the following requirements:
3
- The flow rate shall be adjustable between 0,05 m³/h and 3 m /h, by deviation < 2 %.
- The working temperature range shall be between 10 °C and 90 °C.
- The minimum heating power of the charge circuit shall be 15 kW.
- The minimum cooling power in the discharge circuit shall be 5 kW at a fluid
temperature of 20 °C.
NOTE 2 If mains water at a constant pressure and a constant temperature below 20 °C is
available, it is recommended to design the discharge circuit in a way, that it can be operated as closed
loop or as open loop using mains water to discharge the store.
- The minimum heating power of the discharge circuit shall be 5 kW.
- The control deviation of the store inlet temperature shall be less than 0,05 K.
- The minimum heating up rate of the charge circuit with disconnected store shall be
3 K/min.
- The minimum available electrical heating power for electrical auxiliary heaters shall
be 6,0 kW.
NOTE 3 The electrical power of the pump (P102) shall be chosen in such a way that the
temperature increase induced by the pump (P102) is less than 0,6 K/h when the charge circuit is "short
circuited" and operated at room temperature. (“short circuited” means that no storage device is
connected and SV102, V113, V115 and V116 are closed, see Figure 1).

---------------------- Page: 14 ----------------------

SIST ENV 12977-3:2002
Page 13
ENV 12977-3:2001
ST Store
Key
SV Solenoid valve
FF Flow meter
TT Temperature sensor
HX Heat exchanger
TIC Temperature indicator and controller
OP Overheating protection
VValve
PPump
Figure 1 - Charge circuit of the store testing stand

---------------------- Page: 15 ----------------------

SIST ENV 12977-3:2002
Page 14
ENV 12977-3:2001
The heating medium water in the charge circuit (see Figure 1) is pumped through the
cooler (HX101) and the temperature controlled heaters (TIC106) by the pump (P101).
A buffer tank (ST101) is used to balance the remaining control deviations. By means
of the bypass (V107) the flow through the store can be regulated, it also ensures a
continuously high flow through the heating section and therefore good control
characteristics. With the solenoid valve (SV101) the heating medium can bypass the
store to prepare a sudden increase of the inlet temperature into the store.
The temperature sensors are placed near the inlet (TT101) and outlet (TT102)
connections of the store, the connection to the store is established through insulated
flexible pipes.
The charge circuit can be operated closed, under pressure (design pressure 2,5 bar,
membrane pressure expansion tank and pressure relief valve (V109)) as well as open
(valve (V108) open) with the tank (ST102) serving as an expansion tank. A calibration
of the installed flow meter (FF105) is possible by weighing the mass of water leaving
the valve (V112). The installation is equipped with the usual safety devices, i. e.
pressure relief valve (V117) and overheating protection device (OP101).
The discharge circuit (see Figure 2) is constructed in a similar way. It includes two
coolers - (HX201) and (HX202) - and a temperature controlled heating element
(TIC206) with 5 kW heating power. The discharge circuit can either be operated in
open circulation with water from the net or it can be operated in closed circulation.
During open operation the water is led via the safety equipment (V201) and flows
through the coolers, the heating section and the flow meter (FF205) into the store. The
hot water leaving the store flows through the solenoid valve (SV201) and the valve
(V210) into the drain. The valve (V212) is closed.
For heating the water it is recommended to increase the flow through the heating
section with the pump (P201) in order to improve the control performance; the
additional volume flow returns through the bypass (V209).
During closed-circle operation, the valve of the safety equipment and the cut-off valve
(V210) remain closed, the valve (V212) is open and the water is circulated by the
pump (P201).
NOTE 4 For periodical checks of the measuring accuracy, it is recommended to integrate a
reference heater into the testing stand. Instead of a store, this reference heater is connected to the
testing stand. The reference heater is supplied with an electric heating device.
NOTE 5 See /2/ and /3/ in Bibliography for further information on the use of reference heaters.
The heat transfer fluid used for testing may be water or a fluid recommended by the
manufacturer. The specific heat capacity and density of the fluid used, shall be known
with an accuracy of 1 % within the range of the fluid temperatures occuring during the
tests.

---------------------- Page: 16 ----------------------

SIST ENV 12977-3:2002
Page 15
ENV 12977-3:2001
SV Solenoid valve
Key
TT Temperature sensor
FF Flow meter
TIC Temperature indicator and controller
HX Heat exchanger
VValve
PPump
Figure 2 - Discharge circuit of the store testing stand

---------------------- Page: 17 ----------------------

SIST ENV 12977-3:2002
Page 16
ENV 12977-3:2001
6.1.2 Measuring data and measuring procedure
The data listed in Table 2 shall be measured with the given accuracy:
Table 2 - Measuring data
Measuring data Measuring device Uncertainty
(see figure 1 and 2)


volume flow V in the charge circuit
FF105 2,0 %
C
3
between 0,05 m³/h and 1 m /h


volume flow V in the discharge circuit
FF205 2,0 %
D
3
between 0,05 m³/h and 1 m /h
temperature
of the charging medium
TT101 0,1 K
C,i
at store inlet
temperature
of the charging medium
TT102 0,1 K
C,o
at store outlet
difference in the charging medium
TT101 and TT102 0,02 K
temperature 
between store inlet
C
and store outlet:
(for tests according to 6.3.1)
difference in the charging medium
TT101 and TT102 0,05 K
temperature 
between store inlet
C
and store outlet:
(for tests according to 6.3.2)
temperature
of the discharging
TT201 0,1 K
D,i
medium at store inlet
temperature
of the discharging
TT202 0,1 K
D,o
medium at store outlet
difference in the discharging medium
TT201 and TT202 0,02 K
temperature 
between store inlet
D
and store outlet:
(for tests according to 6.3.1)
difference in the discharging medium
TT201 and TT202 0,05 K
temperature 
between store inlet
D
and store outlet:
(for tests according to 6.3.2)
ambient temperature
TT001 0,1 K
am


electric power Q (auxiliary heating)
-2 %
el

---------------------- Page: 18 ----------------------

SIST ENV 12977-3:2002
Page 17
ENV 12977-3:2001
The relevant data shall be measured every 10 s at least and the measured data shall
be recorded as mean values of at most three measured values. However, for Test H
(see 6.3.1.1.3) during the transient the temperatures shall be measured and recorded
every second.
The temperature sensors shall have a relaxation time of less than 10 seconds. (i. e.
90 % of the temperature variation is detected by the sensor immersed in the heat
transfer fluid within 10 seconds after an abrupt step in the fluid temperature).
Prior to each store test a zero measurement should be performed where the fluid in
the charge or discharge circuit is pumped over the short-circuited charge or discharge
circuit. “Short- circuited” means that flow pipe and return pipe of the corresponding
3
circuits are directly connected (recommended volume flow approximately 0,6 m /h,
temperatures 20 °C, 40 °C, 60 °C, 80 °C). If the measured temperature difference
exceeds the permissible uncertainty of 0,02 K / 0,05 K, the temperature sensors shall
be calibrated.
A reference heater may also be used for the zero measurement.

---------------------- Page: 19 ----------------------

SIST ENV 12977-3:2002
Page 18
ENV 12977-3:2001
6.2 Installation of the store
6.2.1 Mounting
The store shall be mounted on the testing stand according to the manufacturer's
instructions.
The temperature sensors used for measuring the inlet and outlet temperatures of the
fluid used for charging and discharging the storage device, shall be placed as near as
possible at least 200 mm to the inlet and outlet connections of the storage device. The
installation of the temperature sensors inside the pipes shall be done according to
approved methods of measuring temperatures.
If there is/are more than one pair of charging and/or discharging inlet or outlet
connections, then only one may be connected to the testing stand (at the same time)
while the other(s) shall be closed.
The pipes between the store and the temperature sensors shall be insulated
according to prEN 12828:1997.
6.2.2 Connection
The way of connecting the storage device to the testing stand depends on the
purpose of the thermal tests which shall be performed. Detailed instructions are given
in the clauses where the thermal tests are described. Except the test described under
6.3.1.1.2, only the thermal performance of the storage device itself (excluding
connecting pipes) is determined. Hence, for these tests the connections at the storage
device, as delivered by the manufacturer, are considered as the thermal demarcation
between the storage device and the testing stand.
Except the test described under 6.3.1.1.2, the solenoid valves shall be placed as near
as possible to the inlet and outlet connections of the storage device.
Connections of the store which do not lead to the charge or discharge circuit of the
testing stand shall be closed, and not connected heat exchangers shall be filled up
with water. All closed connections shall be insulated in the same way as the store.
Since fluid in closed heat exchangers expands with increasing temperature, a
pressure relief valve shall be mounted.
6.2.3 Testing of the storage device in respect of the design of the connections
The aim of the test described under 6.3.1.1.2, is to determine the influence of poor
designed store connections on the heat loss of the store (e.g. due natural convection
within one single pipe). For this test, the pipes connected to the store shall be taken
into consideration, and convection flows may not be stopped near to the storage
device by solenoid valves. Hence, for the test according to
...