Recen Inno a ions in Mecha onics (RIiM) Vol. 2. (2015). No. 1-2.
DOI: 10.17667/ iim.2015.1-2/18.
1
S o e Elemen s LabView-based Ene gy- low Models
De elopmne and Implemen a ion in HVAC sys ems
Szász Csaba
Depa men o Elec ical Machines and D i es
Technical Uni e si y o Cluj
[email protected] cluj. o
Abs ac — I is well known ha s o e elemen s such as
liquid anks, wa e ese oi s, o gas con aine s, a e basic
elemen s in hea ing, en ila ion and ai condi ioning (HVAC)
sys ems de elopmen and implemen a ion. In a wide ange o
applica ions hey se e as e icien ene gy s o age elemen s by
cap u ing hea ene gy amoun in ho wa e o m. This pape
p esen s a LabView g aphical so wa e-based ene gy- low model
de elopmen o s o e elemen s in HVAC sys ems. In he i s
esea ch s eps he ma hema ical backg ound desc ibing he
ene gy- low p ocesses in he conside ed s o e elemen (wa e
ank) i is p esen ed and discussed. Then an o iginal so wa e
model has been designed and implemen ed o simula e he
ongoing ene gy- low p ocesses. The esul o he abo e men ioned
esea ch e o s is a powe ul and e sa ile so wa e oolki
( i ual ins umen ) well sui able o modeling and simula e
complex ene gy- low p ocesses in HVAC sys ems embedding
a ious ypes o s o e elemen s. Beside he elabo a ed
ma hema ical model conc e e so wa e simula ion examples and
measu emen da a a e also p o ided in he pape . No a leas ,
he p oposed o iginal model o e s a easible solu ion o u u e
de elopmen s and esea ch in HVAC sys ems so wa e modeling
and simula ion pu poses.
Keywo ds — s o e elemen , ene gy- low, HVAC sys em,
LabView model, i ual ins umen
I. INTRODUCTION
As i is well known, a wide ange o compu e so wa e is
a ailable on he ma ke o guide and help esea ches in
complex HVAC sys ems design and implemen a ion pu poses.
These ools wi h a a ying deg ee o complexi y and
pe o mance ha e been de eloped o di e en scopes and
applica ions, and o di e en use o cus ome ca ego ies [1].
Some exis ing HVAC sys ems modeling and simula ion
oolki s ensu es he use ha he espec i ely ool is easy o
use and ul ills in all he daily needs and equi emen s o
designe ‟s. On he o he side, he e a e complex so wa e
oolki s p o iding an accu a e p edic ion o sys em o
componen s pe o mance. In o he wo ds, his gene ous o e
embeds a la ge scale o so wa e p oduc s s a ing wi h
oolki s used by enginee s o au oma e common asks,
con inuing wi h compu e aided d a ing (CAD) p og ams o
modeling and simula e ope a ing condi ions (i.e. o p edic
annual ene gy use and u iliza ion expenses), and up o
specialized analysis ools [1, 2]. These las ypes o so wa e
esou ces a e used as esea ch ins umen s including
echnically accu a e simula ion modules specially de eloped
o academic s udy and esea ches in HVAC sys ems
de elopmen and implemen a ion, usually ocused on de ails
and pe o mance c i e ia.
Ob iously, he abo e discussed compu e so wa e
esou ces may be classi ied in se e al main g oups o
ca ego ies. Acco ding o P. Jacobs and H. Hende son, i can be
dis inguished he ollowing majo ca ego ies [2]:
- P ac i ione Design Tools (a emp o au oma e common
o epe i i e asks such as d awing, sizing, analyzing,
cos ing, and a e used by p o essionals o design
HVAC sys ems);
- Whole Building Ene gy Analysis Tools (aimed a
simula e building ene gy use and de e mina e ope a ing
condi ions ac oss he yea , calcula ing annual
ope a ing expenses);
- Ene gy and En i onmen al Sc eening Tools ( ocused o
e alua e cos -e ec i eness and en i onmen al impac o
ene gy- and HVAC echnologies);
- Specialised Analysis Tools (embedding he bes a ailable
me hods and echniques o simula e speci ic aspec s o
building o ene gy sys em pe o mance; ha a e
gene ally no in widesp ead use by p o essionals).
Howe e , i is no doub among specialis s and esea che s
in ol ed ha he es ablished HVAC sys em models and
simula ion oolki s play a key ole in he en i e building
au oma ion sys ems de elopmen and implemen a ion p ocess.
O cou se, as i has been men ioned abo e, he e a e on he
ma ke a wide ange o cu en ly a ailable p oduc s, anging
om sp ead-shee ools o special-pu pose ools, o ools ha
in eg a e mul iple aspec s o HVAC sys ems modeling and
simula ion [1, 3]. The e is no enough space o enume a e o
discuss all hese oolki s (and i is no he scope o his pape ),
bu i is ou lined ha he cu en ou h gene a ion ools end o
be ully in eg a ed wi h espec o di e en in elligen
buildings pe o mance aspec s, such as au oma e moni o ing
and supe ising, applica ion quali y con ol, in elligen use
in e aces, aul -diagnosis, e c. Un o una ely, e en a his las -
gene a ion le el he e a e impo an discussions among
Recen Inno a ions in Mecha onics (RIiM) Vol. 2. (2015). No. 1-2.
DOI: 10.17667/ iim.2015.1-2/18.
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Fig. 1. The wa e bu e ank manu ac u ed by he Hajdú company
(Deb ecen Uni e si y, Technical Facul y, Depa men o Elec ical
Enginee ing and Mecha onics)
Fig. 2. Ene gy- low model o a s o e elemen (ho wa e ank)
esea che s in ol ed in HVAC sys ems de elopmen
ega ding he adop ed models and simula ion s a egies [3].
I seems ha some basic HVAC elemen o componen models
a e no enough well es ablished and de eloped ye , o ully
cla i ied. The e is he oom whe e his pape p oposes o add
con ibu ions and solu ions by de eloping and implemen ing
no el LabView so wa e-based models sui able o imp o e he
HVAC sys ems modelling and simula ion p ocesses.
II. STORE ELEMENTS ENERGY-FLOW MODEL DEVELOPMENT
I is well known ha s o e elemen s ( a ious ypes o wa e
anks, gas con aine s, o o he liquid anks) a e widely used
elemen s in HVAC sys ems de elopmen and implemen a ion.
Usually hey se e as e icien ene gy s o e elemen s by
cap u ing hea ene gy amoun . Fo he esea ch pu poses
appoin ed in his pape i is a ailable one 750l capaci y
specially de eloped ho wa e bu e ank manu ac u ed by he
Hajdú company (Fig. 1).
This basic HVAC elemen i is used in a hea ing and ai -
condi ioning sys em o s o e in a o m o a ho wa e he hea
ene gy amoun cap u ed by a o ced ai -duc hea pump
sys em ins alled in a building. In o de o de elop he ene gy-
low model o his s o e elemen , i is conside ed he
simpli ied block diag am shown below in “Fig. 2".
In he en i e design p ocess i will be aken in o accoun ha
he s o ed ho wa e will be used bo h o hea ing and cooling
pu poses. Towa d, i is assumed ha he wa e empe a u e is
he same e e ywhe e inside he ank (ideal mixing p ocess).
In o de o calcula e he ins an aneous empe a u e (T) o he
s o ed wa e , i is necessa y o sol e he ollowing ene gy
balance equa ion [3]:
𝑚∙𝑐𝑤∙𝑑𝑇
𝑑𝑡=𝜌∙𝑉∙𝑐𝑤∙𝑑𝑇
𝑑𝑡=𝑞𝑛
(1)
whe e qn [kW] ep esen s he ne hea ene gy ans e o he
ank wa e , cw [kJ/kgK] is he speci ic hea capaci y o he
wa e , V [m3] is he ank olume, and m [kg] he mass o he
s o ed wa e . Addi ionally, i is gi en he 4,1813 [kJ/kgK]
speci ic hea capaci y o he wa e a 25˚C empe a u e.
The ne qn hea ene gy ans e can be calcula ed by
conside ing all he ene gy- low p ocesses be ween he ank
and i s en i onmen . The e o e, i can be w i en he ollowing
ela ionship [3]:
𝑞𝑛=𝑞ℎ+𝑞𝑜𝑢𝑡 +𝑞𝑖𝑛+𝑞𝑒𝑖𝑛 +𝑞𝑒𝑜𝑢𝑡 +𝑞𝑝𝑖𝑛 +𝑞𝑝𝑜𝑢𝑡 ,
(2)
whe e he gi en magni udes a e wi h he ollowing
in e p e a ion:
- qh hea added by he hea e elemen o bu ne ;
- qou is he hea ans e o/ om he use side plan
connec ions;
- qin is he hea ans e o/ om he sou ce side plan
connec ions;
- qein hea ans e o/ om he ambien en i onmen (0, when
he hea e is u ned o );
- qeou hea ans e o/ om he ambien en i onmen (0,
when he hea e is u ned on);
- qpin hea added due o on-cycle pa asi ic loads (0, when he
hea e is u ned o );
- qpou hea added due o o -cycle pa asi ic loads (0, when
he hea e is u ned on);
Due o simpli y calcula ions in his model he qpin and qpou
pa asi ic hea amoun s will be neglec ed by conside ing ideal
on/o swi ching p ocesses. The e o e, he equa ion (2)
simpli ies o he ollowing ela ionship:
𝑞𝑛=𝑞ℎ+𝑞𝑜𝑢𝑡 +𝑞𝑖𝑛+𝑞𝑒𝑖𝑛 +𝑞𝑒𝑜𝑢𝑡 . (3)
The hea quan i ies changed by he wa e hank o/ om i s
nea en i onmen can be exp essed wi h he equa ions:
𝑞𝑒𝑖𝑛 =𝑘𝑒𝑖𝑛 ∙ 𝑇𝑒−𝑇 ; 𝑞𝑒𝑜𝑢𝑡 =𝑘𝑒𝑜𝑢𝑡 ∙ 𝑇𝑒−𝑇 , (4)
whe e Te means he en i onmen empe a u e whe e he ank is
placed, kein és keou a e he loss coe icien s o he gi en wa e
ank in on/o ope a ion mode. The qou and qin hea ene gy-
lows a e calcula ed wi h he ma hema ical exp essions [3]:
Recen Inno a ions in Mecha onics (RIiM) Vol. 2. (2015). No. 1-2.
DOI: 10.17667/ iim.2015.1-2/18.
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𝑞𝑜𝑢𝑡 =𝑘𝑜𝑢𝑡 ∙𝑚𝑜𝑢𝑡
∙𝑐𝑤∙ 𝑇𝑜𝑢𝑡 −𝑇 ; 𝑞𝑖𝑛 =𝑘𝑖𝑛∙𝑚𝑖𝑛
∙𝑐𝑤∙
𝑇𝑖𝑛−𝑇 , (5)
kou and kin being e iciency coe icien s in he gi en ela ions.
A he same ime Tou means he empe a u e on he use side
plan , supposing ha he bu e anks e en may be placed in
o he ooms ( o example: cella o basemen ) like he use
hea ed ones. The Tin a iable ep esen s he empe a u e o he
ecycled wa e in o he ank. Ca ying ou he adequa e
subs i u ions in he equa ion (3), esul s:
𝑞𝑛=𝑞ℎ+𝑘𝑜𝑢𝑡 ∙𝑚𝑜𝑢𝑡
∙𝑐𝑤∙ 𝑇𝑜𝑢𝑡 −𝑇 +𝑘𝑖𝑛∙𝑚𝑖𝑛
∙𝑐𝑤∙
𝑇𝑖𝑛−𝑇 +𝑘𝑒𝑖𝑛 ∙ 𝑇𝑒−𝑇 + 𝑘𝑒𝑜𝑢𝑡 ∙ 𝑇𝑒−𝑇 . (6)
A e pe o ming he simple ma hema ical ope a ions
esul s ha :
𝑑𝑇
𝑑𝑡 = 1
𝑚∙𝑐𝑤∙ 𝑞ℎ+𝑘𝑜𝑢𝑡 ∙𝑚𝑜𝑢𝑡
∙𝑐𝑤∙𝑇𝑜𝑢𝑡 +𝑘𝑖𝑛∙𝑚𝑖𝑛
∙𝑐𝑤
∙𝑇𝑖𝑛+𝑘𝑒𝑖𝑛 ∙𝑇𝑒 + 𝑘𝑒𝑜𝑢𝑡 ∙𝑇𝑒 +
+−1
𝑚∙𝑐𝑤∙ 𝑘𝑜𝑢𝑡 ∙𝑚𝑜𝑢𝑡
∙𝑐𝑤+𝑘𝑖𝑛∙𝑚𝑖𝑛
∙𝑐𝑤+𝑘𝑒𝑖𝑛 + 𝑘𝑒𝑜𝑢𝑡 ∙
∙𝑇 . (7)
The abo e ela ionship is no hing else han a
𝑑𝑇
𝑑𝑡 = 𝑎+𝑏∙𝑇
(8)
ype di e en ial equa ion, whe e
𝑎=1
𝑚∙𝑐𝑤∙ 𝑞ℎ+𝑘𝑜𝑢𝑡 ∙𝑚𝑜𝑢𝑡
∙𝑐𝑤∙𝑇𝑜𝑢𝑡 +𝑘𝑖𝑛∙𝑚𝑖𝑛
∙∙𝑐𝑤
∙𝑇𝑖𝑛+𝑘𝑒𝑖𝑛 ∙𝑇𝑒 + 𝑘𝑒𝑜𝑢𝑡 ∙𝑇𝑒
𝑏=−1
𝑚∙𝑐𝑤∙ 𝑘𝑜𝑢𝑡 ∙𝑚𝑜𝑢𝑡
∙𝑐𝑤+𝑘𝑖𝑛∙𝑚𝑖𝑛
∙𝑐𝑤+𝑘𝑒𝑖𝑛 + 𝑘𝑒𝑜𝑢𝑡
∙𝑇 . (9)
The solu ion o he equa ion 8 is [3]:
𝑇 𝑡 = 𝑎
𝑏+𝑇𝑣𝑘 ∙𝑒𝑏𝑡−𝑎
𝑏 ,
(10)
Twi meaning he wa e ini ial empe a u e a he momen
＝
0.
I he b coe icien is ze o, hen he solu ion o he di e en ial
equa ion is:
𝑇 𝑡 =𝑎∙𝑡+𝑇𝑤𝑖 . (11)
I i is necessa y o calcula e he amoun o ime in which he
wa e eaches i s Tw inal empe a u e, in a same way om he
ela ionship 8 esul s he ollowing alue:
𝑡=1
𝑏∙𝑙𝑛 𝑎
𝑏+𝑇𝑤𝑓
𝑎
𝑏+𝑇𝑤𝑖 .
(12)
In he case o b being ze o
𝑡= 𝑇𝑤𝑓 −𝑇𝑤𝑖
𝑎 .
(13)
The abo e deduced ma hema ical ela ions a e su icien o
desc ibe he en i e hea ing/cooling p ocesses and ene gy- low
phenomena in s o e elemen s like wa e anks o o he liquid
ese oi s.
III. STORE ELEMENTS ENERGY-FLOW PROCESSES LABVIEW-
BASED MODELLING AND SIMULATION
By using as backg ound he ma hema ical model de eloped
in he p e ious pa ag aph, o iginal LabView g aphical
so wa e-based i ual ins umen s (VIs) ha e been designed
and implemen ed in o de o ep oduce and simula e he
ene gy- low p ocesses in s o e elemen s. As an example, in
“Fig. 3” i is p esen ed he ene gy- low model o a 750l
capaci y wa e bu e ank. Ho wa e lows in o he ank ia
he adequa e pipe sys em (Boolean_1) ca ying he hea
ene gy gene a ed by he ai -wa e hea pump moun ed in he
building‟s ceiling. The ho wa e is ci cula ed con inuously by
using he Boolean_2 pump and he opened Boolean_3 al e.
I means ha he hea e (o bu ne ) o he ank i is swi ched
in o he on s a e, he s o ed wa e is hea ed now. The ed
colou o he pipes indica es a ho wa e low, he g een colou
o he pump and al e he ope a ion mode, espec i ely he
open-s a e o hese de ices. I he hea ing p ocess is s opped,
he pipes u ns ins an aneously in o a g ay colou , and he
pump and al e o s a es will be ma ked wi h ed colou s.
The ed pipe moun ed on he igh -down side o he wa e ank
indica e ha he ho wa e i is used o indoo s hea ing
pu poses and he ank i is connec ed o an coils placed in
di e en ooms o he buildings. The le -down side placed
blue colo ed pipe exp esses ha he ho wa e is ci cula ed
inside a closed pipe sys em, in o he s o e elemen e u ning
cool wa e , a e he hea amoun has been ansmi ed o he
indoo s en i onmen ia he used an coil sys em. The inpu
hea amoun can be easily con olled by using he le side
e idenced slide-swi ch con olle .
Fo he ene gy- low p ocess simula ion i is necessa y o
p o ide only he Twi ini ial empe a u e o he wa e amoun
s o ed in he ank and o open he slide-swi ch hea con olle .
In his case he s o ed wa e ins an aneous empe a u e will be
indica ed bo h by a nume ical display and g aphical
he mome e placed on he F on Panel o he VI. Addi ionally,
he empe a u e a ia ion is plo ed ia a i ual oscilloscope in
o de o ensu e a con enien moni o ing acili y o his
magni ude e olu ion in a gi en ime domain. Towa d, a
nume ical indica o displays he ins an aneous hea amoun in
wa s s o ed in he wa e ank espec i ely a LED diode
indica es any change o he slide-swi ch posi ion which
con ols he inpu hea amoun .
Recen Inno a ions in Mecha onics (RIiM) Vol. 2. (2015). No. 1-2.
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Figu e 3. The s o e elemen ene gy- low model (LabView-so wa e, he VI F on Panel)
Figu e 4. Ini ial s a e o he s o e elemen (ho wa e ank)
In ig. 4 i is gi en he simula ion F on Panel window
co esponding o he ini ial s a e o he ho wa e ank, when
he bu ne (o hea e ) ye is in he u n-o s a e.
I is no wi hou impo ance o men ion he e, ha he
de eloped ene gy- low modelling and simula ion so wa e
implemen s he ca alogue pa ame e s gi en by he
Hajdú company. Acco ding o his, he model akes in o
accoun ha he insula ion o he ank is no ideally sui ed,
he e o e a e conside ed i s speci ic hea loss coe icien s.
Hence, when he ou side en i onmen empe a u e is lowe
han he s o ed wa e empe a u e au oma ically a hea ans e
p ocess will ake place o he ou side en i onmen . O he wise,
when he s o ed wa e empe a u e is lowe , he hea ans e
p ocess di ec ion is e e sed now. O he coe icien s like
speci ic hea capaci ies, low- a es, mass low, o o he
cons an s can be se led a bi a y (o a e de use speci ic
needs) in he LabView g aphical p og am.
Recen Inno a ions in Mecha onics (RIiM) Vol. 2. (2015). No. 1-2.
DOI: 10.17667/ iim.2015.1-2/18.
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Figu e 5. The s o e elemen ene gy- low model LabView-based implemen a ion (Block Diag am)
In Fig. 5 i is gi en a piece om he LabView Block
Diag am o he s o e elemen ene gy- low modeling and
simula ion p og am. The e i can be dis inguished he
ma hema ical equa ion used o implemen a ion, VI uni s o
e en s cap u ing, in eg a ion, display and moni o ing, s a e
machines implemen a ion, o o he embedded elemen s.
Howe e , he de eloped i ual ins umen allows su icien
lexibili y and eedom o he use s o model and simula e
a ious ene gy- low p ocesses in a wide ange o wa e anks,
gas con aine s, o o he liquid anks. Ob iously, in his pape
only a i s e sion o he designed and implemen ed so wa e
has been p esen ed. Taking in o accoun he immense
complexi y o he add essed opic, his modelling and
simula ion so wa e suppo s a con inuously imp o emen and
de elopmen p ocess in o de o achie e a mo e accu a e
imi a ion o he en i e ene gy- low p ocesses in a wide ange o
s o e elemen s used in complex HVAC
sys ems implemen a ion.
IV. CONCLUSIONS
The pape p esen s a LabView so wa e-based ene gy- low
model de elopmen o s o e elemen s in HVAC sys ems.
Beside he es ablishmen o an adequa e ma hema ical model
indispensable o such a pu pose, he so wa e implemen a ion
s eps o s o e elemen s ene gy- low p ocesses is un olded and
p esen ed. The esul is e sa ile and powe ul so wa e
p og ams (VIs) sui able o simula e complex ene gy- low
p ocesses and se ing as no el ools o HVAC sys ems ene gy
balance e alua ion. E en in his s age o he esea ch he
elabo a ed so wa e models a e unde a con inuous
de elopmen and imp o emen p ocess, he p oposed o iginal
model o e s a easible solu ion o u u e de elopmen s and
esea ch in HVAC sys ems modeling and simula ion pu poses.
ACKNOWLEDGMENT
This esea ch was suppo ed by he Eu opean Union and
he S a e o Hunga y, co- inanced by he Eu opean Social
Found in he amewo k o TÁMOP 4.2.4. A/2-11-1-2012-
0001 „Na ional Excellence P og am‟.
REFERENCES
[1] DOE, “Building Ene gy So wa e Tools Di ec o y”, U.S. Depa men o
ene gy, a ailable a : h p://www.ee e.ene gy.go / [accessed:
Augus , 2009].

Recen Inno a ions in Mecha onics (RIiM) Vol. 2. (2015). No. 1-2.
DOI: 10.17667/ iim.2015.1-2/18.
6
[2] J. Jacobs, H. Hende son, “S a e-o - he-a e iew whole building,
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design olls” US Depa men o Comme ce, Po Royal Road, 5285,
Sp ing ield 22161, VA, 2002.
[3] Ene gyPlusTM-Ene gyPlus Enginee ing Re e ence, “The e e ence o
ene gy plus calcula ions” US Depa men o Ene gy, 2013.