© 2024 Brno University of Technology – VUTIUM Press Editor © 2024 Belo Füri Text © 2024 Milan Kubín, Jiří Hirš Graphic design and layout © 2024 Karel Scherzer ISBN 978-80-214-6205-2
Contents
About the Authors 7 Preface 9 Nomenclature 11 Experimental Setup 16 Chapter I. 21 Ti e ur e ui te erature in a i r annel Chapter II. 37 ur a e ten i n in erti al a i r annel Chapter III. 54 ur a e ten i n in in line a i r annel Chapter IV. 75 e tt a e ui in a i r annel Chapter V. 94 x eri ental in e ti ati n e e t eat tran er ara teri ti in a i r -channels Chapter VI. 127 e t eat ux, a ux an ualit a ur n t e eat tran er e ient in a i r annel Chapter VII. 150 Effect of surface r u ne in a i r annel n riti al eat ux and friction factor during condensation Chapter VIII. 176 Effect of position and connection heat exchanger on thermal and hydrodynamic be a i r in a i r annel Chapter IX. 196 Investigation on the e e t ra itati nal rientati n n ui urin n en ati n in a i r annel Chapter X. 226 Prediction of t e u elt nu ber b eat tran er in a i r annel Conclusion 258 Appendix 260 Subject index selected 296
l
an i in, i l M la l M in MT nb , ut re r
at t tt tran
,
i ui a ter , , , , 0 i ui l bet een bubble an all a ter 0 a a ter 2, a ur a ter 4, a ae a ter 4 a a ter 2, a ur a ter 4, , , , , 0 a nl , all ta en a a ur a ter 0 Heat a ter t a ter 0 annel a ter nter ittent t annular tran iti n a ter 0 nternal a ter , , , 0 nlet a ter , 2, , 4, , , , , 0 i ui a ter 2, , li ui ae a ter 4 i ui a ter 2, , 4, , , , 0 arit i ean a ter a inar a ter 0 i ui nl , all ta en a li ui a ter 0 Mixture a ter 4 eter inin a ter 4 Mini u alue a ter , , , 0 Mean te erature a ter u leate b ilin a ter 0 utlet a ter , 2, , 4, , , , , 0 ae a ter 4 re i te a ter , , 0 e u e a ter u er ial a ter 4 a ur a ter trai t annel erti al a ter , 0 aturati n a ter , 0 in le a e a ter 0 T ae a ter 0 Turbulent li ui turbulent a a ter 0 a inar turbulent tran iti n a ter 0 a ur a e a ter 2, a ur a ter 4, , , , 0 i u 10). ater, all, eate ur a e, r ertie e aluate at all n iti n , a ter , 2, , , , 0 a annel in line , all a ter , 0
a ter
15
Experimental Setup
r in e ti atin ara eter a e tin t e e e t eat tran er an ui , an ex eri ental ea urin line a et u t el t e eratin n iti n urin t e n en ati n ater a ur in t e tube bun le a eat ex an er it a icro-channels. r t e ex eri ental in e ti ati n t e e e t re uire ara eter , t e i e l i al e i n t e ea urin line a initiall er r e , t e ain e aluate ele ent, i , a t e tube eat ex an er it a i r annel T e a tual ea urin line a et u n t e ba i a ree e i n an te ni al u entati n in t e eratin re i e t e tea ur e an lin ater u lier T e exeri ental etu r t e e ri ti n i i i e int a ater a ur ir uit an lin ater ir uit, ee i ure T e ater a ur ir uit n i t a tan ur e ere an re ure v,in a T e a ur i r u e it a n n te erature tv,in ater a ur enter t t e ea ure bun le er t in alle tube , ere it be e t t e n en ati n r e T e n en ate lu e an c condensate temperature tc,out i ea ure n t e utlet t e tube bun le a ir annel be re in int t e tan T e internal i tan e bet een tube in t e bun le i le b a ir uit r a ur e l ater lu e an e t e lin ater are en ate b t e ex an i n tan n t e a ur n en ate at le el H tan ar a bun le a i r annel i n t e uter au e n le el T e tube a in t e ex an er i in ulate b t er al in ulati n it a t i ne 0 , t e eat tran er i n t a e te an it e n t lea t eat l T e inner ur a e t e ea urin a i r annel i leane it a i erenta e al l leaner an t e urit t e ater a ur r t e tea enerat r i er T e be t ex eri ental nit rin t e tube a ur ater eat ex an er a ea ure in a erti al iti n in binati n it unter an arallel nne ti n lin ater e i e t at, an in t e et nne ti n t e ex an er a unter arallel ara etri an e in ut li ui ere exer i e , i e n t e i e in ut a ur an n t e i e in ut lin ater The side of vapour: ne ariable ara eter n t e ater a ur i e a in t e r a an e t e re ure t e aturate ater a ur at t e inlet t e ex an er an t ere i a ner i ti all a iate an e in t e a ater a ur in t e ex an er T e ran e re ure an e a r 0 0 bar eat ater a r x 00 t 20 bar aturate a ur a r x T e re ure inlet aturate a ur a ea ure b te erature, in e en entl n t la e it t e en iti it t e thermocouple ± 0.10 K. 16
The side of water: T e t ariable ara eter n t e ater i e ere te erature an ater T e lu e ater a ea ure in e en entl a ater eter an a eter la e ne be in t e t er T e e i e r u ulati el , t e tatu an ti e ere re r e in t e r a i ital t ra ntainin t e ti e tran er t e n an tatu tran er t liter T e te erature inlet ater a ea ure in e en entl n t la e it t e en iti it t e t er u le 0 0 K, ee Table 1.1 – 10.1, see Appendix. T e ea ure ent t la e in a tati nar r it a xe e etr t e ex an er iti n an nne ti n in binati n it a xe ettin in ut ara eter a ur re ure, te erature an ater an urin t e ea ure ent a n t a ti el inter ere t t e ab e ettin T e t er al re n e t e eat ex an er a ur ater a re r e it re iti ne t er u le it en iti it 0 0 K in a ti e te e n , ee i ure , 4 T e rauli re n e t e eat ex an er a nit re in e en entl b a ater eter an a eter n t e ater i e in t e r a i ital t ra tatu an ti e , a t e re r t e a ater a ur n en ate i a er r e b t ra in a i ital ale tatu an ti e , it en iti it 0 0 an a ran e r 0t 0 T e e aluate ele ent t e a e ble ea urin line i t e ex eri ental in line tube eat ex an er it a i r annel , a t tal ie e er t in alle a i r annel t e len t 00, 0 inner ia eter an 0 all t i ne ee i ure 2, Table 2 The a a tati n a all a e been a lie er iall in e t e 0 n e i le and transpiration re-entry cooling of rocket boosters, ablative surfaces cross-hatching and bu ti n a ber r l a ri ati n a e i n an in u e ean rti e an an alternatin e n ar bran i el in ui ixin in i e t e annel ere ean rti e ur en t e in t e a annel i er i an t e i un table an e n ar are e el e i intr u e air trea i e riente rti e a e an e in a i r annel urrentl are art a little ex l re el t er na i annel are intenti nall a t in a bun le ie e an t u , e small geometric imperfections of each channel are eliminated. The currently measured alue in ata le rre n re t t e tati ti al a era e an t e e e e e t i al eli inate T e bun le i urr un e b an uter er tube it a ia eter 4 The number of measured data points in a time step of 5 seconds, for a vertical position of the eat ex an er i , in t tal 2 2 4 i e 40 ur unter nne ti n 2 4 int , i e ur , arallel nne ti n int i e 2 0 ur rt e in line iti n t e ex an er 4 t e t tal nu ber ata int i 24 i e 4 hours ( unter nne ti n int , i e 2 4 ur , arallel nne ti n 2 int , i e 2 ur r t e ur e e aluatin t e re r e ata r i la in t e ti e ur e t e te erature t e li ui in t e eat ex an er a t e ba i characteristics for determining heat transfer and other parameters an interactive electronic ra i t l T a reate r re r e alue n t e ri er an t e e n ar t e eat ex an er, b t r arallel an unter T i intera ti e ele tr ni ra i al t l i t e ub e t atent r te ti n t e aut r t i arti le T e ti e ur e te erature n en in ater in a i r annel i t e 17
essential starting point for the calculation of basic parameters according to suitable correlati n an ele te e iri al relati n ater r ariant unter an arallel of the vertical heat exchanger and their evaluation. ir uit a i r annel i e ne b it a elen t , a litu e , rauli ia eter h), all t i ne t , a rati 2 x , h, function y1 x y2 x in 2 x rx 0, t A parameter, 𝛼𝛼, e ab lute alue i e ual t t e rati t e u er all a e a litu e t t e l er all a litu e, i u e t e ribe t e n urati n t e annel e indicate both plus and minus values for 𝛼𝛼 in r er t i tin ui t e i eren e bet een t e annel t at a e a a e a e a litu e at t e u er all en 𝛼𝛼 < 0, the troughs t e l er all an t e re t t e u er all a e ea t er it ut a e i eren e annel Whereas, for 𝛼𝛼 0, t e enter at x x0 int an ex an e art t e a and if 𝛼𝛼 0 at t e entran e t e a annel it in l e int a ntra te re i n in t e i init t e u er all e i e t at, r 𝛼𝛼 0 t e u er all i trai t an r 𝛼𝛼 = 1 the channel is so called serpentine and for 𝛼𝛼 = – 1 it is a raccoon channel. n t er ara teri ti t e a annel i t e critical Reynolds number to transiti n r la inar t turbulen e n t e a alle annel, t e critical Reynolds nu ber e en n 2a an i le t an t e critical e n l nu ber ec 2 00 r trai t annel M Ke et al. 1980). Tolentino et al. 200 a e n t at t e critical e n l nu ber i e en le t an 2 0 r 2a 0
Figure 1 Schematic of the experimental set up 18
0,0 °C 0,0 °C 0,0 °C 0,0 °C 0,0 °C 0,0 °C 0,0 °C
0,0 °C
0,0 °C 0,0 °C
0,0 °C 0,0 °C 0,0 °C 0,0 °C 0,0 °C 0,0 °C 0,0 °C
0,0 °C 0,0 °C 0,0 °C
0,0 °C 0,0 °C 0,0 °C 0,0 °C 0,0 °C 0,0 °C
Figure 2 The experimental channel heat exchanger with wavy micro-channels
0,00 kW (0,00 °C) 0,0 °C 0,0 °C 0,0 °C 0,0 °C
0,0 °C
0,0 °C
0,0 °C
0,0 °C
i ure Schematic of the location of the sensors on the heat exchanger for reading the measured data, vertical position
0,0 °C
0,0 °C 0,0 °C 0,0 °C
0,0 °C
0,0 °C
0,0 °C
0,0 °C 0,0 °C 0,0 °C 0,0 °C 0,0 °C
Figure 4 Schematic of the location of the sensors on the heat exchanger for reading the measured data, inclined position
0,0 °C 0,0 °C 0,0 °C
0,0 °C
0,0 °C
0,0 °C
0,0 °C 0,0 °C
0,0 °C
Figure 5 Wavy micro-channels heat exchanger 0,0 °C 0,0 °C 0,0 °C 0,0 °C 0,0 °C 0,0 °C
19
Figure 5 Cross section of heat exchanger with wavy micro-channels (dimension mm)
The total length channel The medium length of the channel in contact with water The corrugated length of the channel The uncorrugated length of the channel The number of waves on one channel External The wave area of one channel 414,5 The area of the corrugated part of the channel 11 606 The area of the uncorrugated part of the channel 4 298 The total area of the channel 15 904 The area of 55 pcs channels 874 703 Table 2 The basic technical data wavy micro-channels of the heat exchanger
20
1 300 mm 1 142 mm 800 mm 171+171 mm 28 Internal 310,9 mm2 8 705 mm2 3 223 mm2 11 928 mm2 656 028 mm2
Chapter I. Time course of fluid temperatures in wavy micro-channels
1. Introduction T e ti e ur e ui te erature in ener e ui ent i eat ex an er all uali ati n are t e ne e ar art a e been an are t e ub e t eat tran er r b an aut r , r exa le , 2 , , 4 , , T e in e ti ati n t e ur e te erature ari u ui it a uitable arran e ent ui in ener e ui ent an eter inin t eir ti al e ien tran i i n an erati n ara teri ti an be un , r exa le , , 0 , , 2, , 4, T e e ial e a i i la e n t e ui u e an it i al an e i al r ertie t all t e ui u e in te ni al ra ti e are uitable r t eir u e in ener e ui ent an eat ex an er Heat ex an er la a ital r le in aer a e, aut ti e, e i al, cryogenic, etc. engineering applications and processes such as refrigeration, chemical an il re nin , ele tri er enerati n an r e in , et n t i arti le e ill eal in re etail it t e e aluati n t e ti e ur e ui te erature an ele te te erature in uen e t e ara eter in a i r annel t e eat ex an er in t e erti al iti n an in t e in line iti n 4 in t e ie t e ri ntal lane urin t e ater n en ati n n t e ba i n t e ex eri ental in e ti ati n t e ba e ui r t e exa inati n ater a en , be au e it bein a ualit , a e an n n a able li ui it er t er al r ertie n a iti n ater till n its application not only as a refrigerant or temperature medium in technological processes and heating systems, cooling or air conditioning systems, but also in electrical engineerin , t e ar in u tr , t e ar a euti al in u tr , et T e ntributi n e n t eal it t e e aluati n t e ti e ur e te erature t er t e ater ea ater et r ater it i erent i uritie in t e eat ex an er 2 For the purpose of evaluating the recorded data set for displaying of the time course te erature t e ui in t e a i r annel t e ex an er, t e intera ti e ele tr ni ra i t l T a reate r re r e alue n t e ri er an t e e n ar r erti al an in line eat ex an er iti n arallel , unter T e te n l ue M ataba e, a li ati n l i n H an renerin t HTM it an J n intuiti e alue ele t r i a ailable t at all e niti n t e re uire ata r t e ataba e a r xi atel 00 000 re r n t e intera ti e t l ne an ire tl e t e re uire t e re r e alue , ti e ra e, ran e en r b e nin inter al r e i all in i i uall , rate i n rin e iati n an t e a re ente i la n art r a , en r , ail a era e , 21
a era e er en r , etail T e ren ere art i ull intera ti e, it i ible to rotate, zoom in, omit graphic lines and take pictures into PNG or curve SVG format. rtabilit i al n i ere , an i en ie , an le ren erin , et i ible t be are ea il b en in a lin T e ea urin line a ba e n t e a ree te ni al u entati n in t e eratin re i e t e a ur an t e lin ater u lier 140,000
Temperarure [°C]
120,000
Figure 1.1. The time courses of fluid temperatures in the heat exchanger with wavy micro-channels, vertical position, counterflow
118,1
100,0
100,3
100,000
80,000
75,8
73,6 61,8
60,000
38,0
40,000 40,0
28,4 21,6
20,000 11,8
0,000 0
200
400
140,000
600 Length [mm]
800
1000
1200
1400
Figure 1.2. The time courses of fluid temperatures in the heat exchanger with wavy micro-channels, vertical position, parallel flow
120,000
Temperarure [°C]
111,5
100,000
95,4
94,0
95,0
80,000
74,1
66,3
60,000
48,3
40,000
32,6 24,0
39,8
36,6
43,9
25,4
17,6
20,000 12,4
0,000 0
22
200
400
600 Length [mm]
800
1000
1200
1400
120
i ure The time courses of fluid temperatures in the heat exchanger with wavy microchannels, inclined position, counterflow
112,6 101,6 96,6
Temperarure [°C]
100
97,3
98,3
91,2 82,0
80 68,6
66,1
60 46,8 42,8
40
34,2 25,0
20
0
14,2
0
200
400
600 Length [mm]
800
80
70 61,1
59,1
60
1000
1200
1400
Figure 1.4. The time courses of fluid temperatures in the heat exchanger with wavy micro-channels, inclined position, parallel flow
71,2
Temperarure [°C]
21,6
50 40,5
40
40,8
40,2 40,8
33,6 32,8
30
37,7
38,0
35,2
20 10 0
0
200
400
600 Length [mm]
800
1000
1200
1400
thick red line – modular curve of theoretical time course of temperatures (MCTTCT – vapour, condensate thin red line – experimental time course of temperature (ETCT) – vapour, condensate thick line – modular curve of theoretical time course of temperatures (MCTTCT) - cooling water thin line – experimental time course of temperature (ETCT) – cooling water 23
Table 1.1. T e ea ure ata in t e ele te ti e ra e t e eat ex an er ea ure ent it a i r annel r t e erti al iti n a unter , b arallel an rt e in line iti n unter , arallel , ee en ix
2. Solution methods r an ui , e i te erature r le in ener e ui ent, in lu in t e eat ex an er in ari u iti n erti al, ri ntal, in line are i en in ntributi n , re ie an r e i nal b , r exa le , 20 , 2 , 22 , 2 , 24 2 ll the time courses of temperatures should be carefully checked before use because very ten a ura bet een i erent ur e i n t uarantee T i a er are t e ti e courses of temperatures and selected te erature ara eter in t e n en ati n ater a ur in t e eat ex an er in t e erti al an in line a i r annel T e e aluati n ui i ater, t e inlet an utlet te erature t e ri er an t e e n ar are btaine r t e intera ti e ele tr ni ra i t l T , ee Table 2 Position HE
vertical counterflow parallel flow
inlet temperature 118.1 t ui Ti l ui ti outlet temperature t ui To l ui to
111.5 24
inclined counterflow parallel flow 112.6 42
71.2 2
2
40
4
Table 1.2. The inlet and outlet temperatures of fluids for different positions of the heat exchanger with wavy micro-channels
2.1. Parameters influencing the time course of temperatures 1. Heat Transfer Fluids (HTFs) HT an be la i e b t eir tate atter urin n r al eratin n iti n iti nall t t e t ree tan ar tate a e u , li ui , li , HT t at un er a a e an e an u er riti al ui are al ible rtant t er i al r ertie HT are l te erature li itati n li i ati n te erature , i u er te erature li itati n e a rati n te erature t er al tabilit li it at l re ure , i t er al n u ti it re ei er te erature l e t HT te erature, l i it l er u in er re uire ent , i en it an eat a a it enable u e a t ra e e iu , ibilit u a ea r in ui , e i al atibilit l rr i it it nta t aterial , l t, i a ailabilit , l t xi it , a abilit , ex l i it an en ir n ental a ar 2 24