International Journal of Advance Engineering and Research Development PERFORMANCE EVALUATION OF COMPOUND MULTILAYER INSULATION (77K-300K)

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1 Sientifi Journal of Impat Fator (SJIF): 5.71 International Journal of Advane Engineering and Resear Development Volume 5, Issue 0, February -018 e-issn (O): p-issn (P): PERFORMANCE EVALUATION OF COMPOUND MULTILAYER INSULATION (77K-300K) performaner of multilayer insulater for finiding termal ondutivity Pinaben j Caudari 1, Druma A. Patel 1 Meanial Department, Amedabad institute of eng. College Meanial & Automobile Department, Amedabad institute of eng. College Abstrat - Multilayer insulation (MLI) using alternate layers of sield and spaer. In ig vauum MLI is te most effetive Cryogeni Insulation. Te Investigations are entered on te influene of te number of layers and layer density, wit te old boundary at te same temperature as liquid nitrogen. Te paper Presented teoretial and experimental investigation of te eat transfer of different MLI wit different vauum amber pressure. Liquid nitrogen boil of rate metod is used to measure te eat transfer rate. Te apparent termal ondutivity were alulated over a wide range of temperature (77k-300k) and pressure (10-6 mbar 10 3 mbar). Te termal performane of ompound and Composite MLI is investigated. Te temperature profile and eat transfer troug te MLI were obtained as a funtion of level of vauum and vie versa. Keywords- Insulation, vauum, Liquid nitrogen, pressure; Multilayer I. INTRODUCTION Multilayer insulation ave been te subjet of great interest and importane to termal engineers and te early development of eat transfer tenologies, wi alled Super Insulation Material (MLI) blankets are extensively used in spae veile and Cryogeni Dewar as ligt weigt termal protetion system beause of te virtues of good insulation arateristis and little pollution[1]. Multi layer Insulation is te most effetive ryogeni insulation urrently available. In general a large number of igly refleting sields interposed by termal spaers are plaed in a ig vauum environment to form te MLI. Multilayer insulation developments of insulating systems were te eat transfer meanism of gas ondution, solid ondution and radiation ave been redued to minimum. Radiation is minimized by using many layers of igly refleting metal foil, solid ondut is minimized by using a low ondutivity fibrous material or by rinkling te sield material to allow ontat at only a few points. Gaseous ondution is minimized by reduing te residual gas pressure []. Te modes of eat transfer are also dependent on a variety of parameters su as insulation density, number of layers, ontat pressure, out gassing arateristis, gas pressure distribution witin te insulation old and warm boundary temperatures. Te present work involves te development of a set up for evaluation of te performane of ompound MLI and omposite MLI and subsequene investigations on MLI. Te investigations ere intended to [3]. 1. Compare a few indigenous MLI materials. Study te influene of number of layers and layer density on te performane of MLI. 3.Study te vauum amber pressure. 4.Temperature profile of te MLI as a funtion of amber pressure. 5.Compare te experimental results wit teoretial and ea oter. II. THEORETICAL FORMULATION Tere are tree simultations modes of eat transfer witin te blanket, termal radiation between sields and solid ondution troug te separator materials and gases ondution []. A THERMAL RADIATION Te eat transport due to radiation between two surfaes at different temperatures an be redued signifiantly by interposing termal isolated radiation sields. Te radiation eat transfer rate between two surfaes is given by Stefan- Boltzmann equation []. q radiation T A ( T ) Were σ is steafan- Boltzmann onstant (5.67 x 10-8 W/m -k 4 ), A 1 is outer surfae area in inner vessel. T and T ot and old boundary temperature (K), E is emissivity fator. A inner surfae area of outer vessel.e 1 & e is emissivity of inner and outer vessel material at 77 K and 300K. B GAS CONDUCTION Corruini 4 developed te following equation for gas All rigts Reserved 130

2 International Journal of Advane Engineering and Resear Development (IJAERD) q gasondution GPA F ( T T ) () 1 a 1 g R Were G [ ] (a) 1 8T P absolute pressure in pa.f a is aommodation oeffiient fator. 1 1 A1 1 [ 1] (b) Fa a1 A a a 1 and a are aommodation oeffiient of surfaes. C SOLID CONDUCTION Condution troug te solid is expressed as [5] q A ( T T ) (3) solidondution 1 Were is solid ondution of spaer material. Cunningam (1984) as obtained an C s.56 N x T T / (3a) Were C s is emperial orrelation for te solid ondutane (C s = 3.40 x W-m 0.56 / K ) D TOTAL HEAT TRANSFER q total = q radiation+ q gasondution+ q solidondution (4) E THEORETICAL TEMPERATURE DISTRIBUTION Te teoretial temperature distribution for radiation sields separated by a vauum between parallel walls at 300 k and 76 K 6]. T i 4 i [ T ( ) 1/ T T1 ] (5) n 1 Were T i is te temperature of te i t sield and i is te number of te i t sield ounting from te warm wall. n is te total number of sields in te system. F Variation of Termal Condutivity of MLI wit Layer Density Cunningam as obtained an empirial orrelation for te solid ondutane for a MLI onsisting of double - aluminized Mylar sields and a two layer tikness of silk net between te sields in 1984[5]. C s.56 N / x T T Were C s =.4 x 10-8 W-m.56 / m - K = 3.40 x W-m 0.56 /K If te number of layers per unit tikness is inreased, generally te radiant eat transfer is redued, and te apparent termal ondutivity of te MLI may be redued up to a ertain point. If te insulation is ompressed too tigtly, solid ondution begins to inrease to more tan offset te derease in radiant eat transfer, and te apparent termal ondutivity is inreased wit furter inrease in te layer density. Tis effet is illustrated in Fig.1and table 1 for a typial MLI [,5]. (6) 1 e( T kt N x Were = 5.67 x 10-8 w/m - K 4, e = radiation sield emissivity e = 0.0 for aluminum foil e = for double aluminized Mylar H T )( T C ( e) H T C ) All rigts Reserved 131

International Journal of Advane Engineering and Resear Development (IJAERD) III. CYLINDRICAL CALORIMETER WAS DESIGN AND DEVELOPED FOR EXPERIMENTAL WORK.

3 International Journal of Advane Engineering and Resear Development (IJAERD) III. CYLINDRICAL CALORIMETER WAS DESIGN AND DEVELOPED FOR EXPERIMENTAL WORK. A number of different metods as well as different designs & apparatus are available for te measurement of Apparent termal ondutivity of MLI. Considering tis metod [7] te ylindrial a alorimeter and te boil off measurement metod are preferable from te point of view of simpliity and auray. As mentioned by Kagner [8] Main advantage of tis arrangement is tat te sample an be eld wit maximum surfae area and minimum edge area. Te boil of measurement metod is more aurate from te power input metod Hene, te boil off measurement metod and ylindrial apparatus were seleted for te present work. A APPARATUS Te alorimeter onsists of a measuring vessel, two guard vessel and vauum amber as sown in fig-1. Figure. Cylindrial All rigts Reserved 13

4 International Journal of Advane Engineering and Resear Development (IJAERD) Te test and guard ambers are 76mm in diameter ollow ylinder tat form a mandrel for warping te insulation. Tese amber are filled wit Cryogeni fluid and from te old boundary during te tests. Te termoouples used to measure te temperature distribution are suggested in te figure. Te test amber is vented troug a wet test meter and fundamental water displaement metod. Te onstant temperature bat is used to maintain te boil-off rate measurement. Te vapors are in supereated state [3]. Te rate of evaporation is diretly proportion to te rate of eat transport troug te sample. Te guard ambers are vented troug a olumn of water in order to make te guard amber temperature sligtly iger tan te test amber temperature. Tis avoids ondensation of te test amber vent gas as is passes troug te guard [9]. Te apparent termal ondutivity( K at ) for tis experimental arrange is given by [1], [9]. qt ln( ro / ri ) K at (8) LT T ) qt m fg (8a) m V (8b) Were q t is te rate of eat transport to te test amber, L is te lengt of te test amber and r o and r i are inside and outside radius of te speimen, T & T is ot and old surfae temperature respetively. m is mass flow rate of Boil of gas, fg is latent eat of liquid nitrogen, V is volume flow rate, ρ is density of boil off gas. B VACUUM SYSTEM Te vauum amber is evauated using a vauum system onsisting of a two stage rotary vauum pump, to develop a vauum up to 10-3 mbar and to funtion as a bak up pump. Te diffusion pump start to operate wen te vauum is better tat 10 - m bar and measure te level of vauum upto 10-6 mbar. C INSTRUMENTATION Te experiment involves te measurement of boil-off rate, temperature and vauum amber pressure. Boil of rate Te boil-off rate of liquid nitrogen from te measuring vessel is very small relative to te level normally required. Fundamental water displaement metod used to measure volume flow rate in ig vauum,10-6 mbar to 10-4 mbar. 0.5 Lit/revolution apaity, positive displaement wet gas flow meter used to measure te volume flow rate in low vauum, 10-3 mbar to 10 3 mbar. Vauum pressure Te amber pressure is measured using a pirani gauge (up to 10-3 mbar) and a penning gauge (below 10-3 and upto 10-6 mbar). Temperature To measure te temperature distribution troug te MLI tikness and to study its ool-down istory. Digital temperature indiator and opper - onstantan termoouples are loated at seleted positions. IV. PREPARATION OF MLI Te material for sields and spaers are provided indigenously. For test 1, sield of Aluminum foil (30µm) and spaer of fiber glass paper (15µm) wit layer density of 15 layers/m, and insulation tikness is 10 mm. For test sield of double Aluminized Mylar (1µm) and spaer of Tissu fiber glass paper (15µm) wit layer density of 0 layers/m and insulation tikness is 10 mm. In literature test-1 and test- are developed and tested for low temperature insulation appliations. More over tese two sets of material an be used for ompounding as well as omposite type MLI. Here in test-3, We ave ompounded te material like Aluminum foil and fiber glass paper of 10 mm insulation tikness wit layer density of 15 layer/m and 10 mm insulation tikness of double aluminized Mylar and Tissu fiber glass paper wit layer density of 0 layer/m. Total Number of layers are 35 are wrapped on te test and guard ambers of te alorimeter respetively. In test-4, for omposite material, first we ave layered te all above materials as below. Onelayer Tissue glass paper Aluminized Mylar Fiber glass paper Aluminum All rigts Reserved 133

5 International Journal of Advane Engineering and Resear Development (IJAERD) Wole blanket of omposite material is wrapped on te test and guard ambers of alorimeter wit layer density is 10 layers/m. wit insulation tikness is 0 mm. Te speifiation of our samples is sown in table-. Table 1 speifiation of material used to fabriate and test samples. Test MLI No. Sample 1. Alu.foil (30µm) +fiber glass paper (15 µm) Layer density layers /m Total Number of layers Sample tikness (m). Double Aluminized Mylar (1µm) +Tissu fiber glass paper (15 µm.) V. OBSERVATION Te teoretial and experimental Apparent termal ondutivity of different MLI test is sown in table 3 and table 4 as funtion of vauum amber pressures. Table Teoritial Comparison of Apparent Termal Condutivity of different MLI test (T K T -77 to 90K). Camber Pressure (mbar) Apparent Termal Condutivity (mw/m-k) Test 1 Test Table 3 Experiment Comparison of Apparent Termal Condutivity of different MLI test. T K T -77 to 80K Camber Pressure (mbar) Apparent Termal Condutivity (mw/m-k)- Test 1 Test Aording to Table 3 and 4, te experimental results agree very well wit te values of apparent termal ondutivity derived from te teoretial analysis in ig vauum (less tan 10 - mbar) but te All rigts Reserved 134

6 International Journal of Advane Engineering and Resear Development (IJAERD) beomes larger at low vauum due to inadequate gas ondution models and insuffiient data on te gas pressure between te MIL layers. Figure 3. Variation of apparent termal Condutivity wit vauum amber pressure. As per figure 4 te apparent termal ondutivity inreases wit inreases in vauum amber pressures and inrease in number of layers for a given layer density.as per table 4 and figure 4, te omparison of MLI samples in test-1 and, te apparent teramal ondutvity of double aluminized Mylar is about two times more tan aluminum foil. Tus te aluminum foil is better radiation sield tan te double aluminized Mylar.Te omparison between test 3 and 4, te apperant termal onutivity of ompound MLI is less tan omposite MLI.Tus te ompound MLI is better tan omposite MLI. VI. CONCLUSIONS Based on te teoretial and experimental investigations te following onlusions are drawn: (1)As per Table 1 and figure 1, as non omogeneous material, te variation of layer density and ange in emissivity, orrespondingly te termal ondutivity and optimum layer density are also anged. Optimum layer density of aluminum foil is 15 layers/m and doble aluminized Mylar is 0 layers/m. ()As per table 3,4 and figure 4,te Aluminum foil and fiber glass paper is te best ombination among te various ombination. (3) Apparent termal ondutivity of MLI and eat transfer troug te MLI inreases wit inreases in vauum amber pressure and inreases in number of layers for a given layer density. (4)As per figure 5(a) to 5(d), wit inreases in vauum amber pressure te temperature profile of te MLI anges from paraboli to linear from indiating an inrease in te ondutive eat transfer omponent. (5)For te same number of layers, te temperature of any speifi layer dereases wit inreases in vauum amber pressure and vie All rigts Reserved 135

7 International Journal of Advane Engineering and Resear Development (IJAERD) REFERENCES [1] P.J. sun, J.Y. Wu, P.Zang, L.XY, M.L.Jiang, Experiment study of te influenes of degraded vauum on multilayer insulation blankrts, Adv. Cryog. Eng., Vol.49, No.,-1, pp , 009. [] Randall F. Barron, Gyogeni system, seond Edition, Oxford University press, pp , [3] S.L.Bapat, K.G. Narayankedkar and T.P. Lulose, Experimental Investigation of Multilayer Insulation, Advanes in Gyogenis, Vol.-30, pp , [4] R.J.Corruini, Gaseous Heat Condution at Low pressure and temperature,vauum,viii,pp.19-9,1959. [5] R.F. Baeron, Gyogeni Heat Transfer, Taylor and Franis, pp , [6] R.H. kropsot, J.E. Srot, M.M. Fulk, Multiple Layer Insulations, Advanes in Gyogenis.Vol-5, plenum press New York, pp , [7] T.P.Lukose, Performane predition and experimental investigation on multilayer insulations, PD Tesis Indian Institute of Tenology,Bombay,India (1966). [8] M.G. kagner, Termal Insulation in Gyogeni engineering program for sientifi Translation,Ltd, [9] R.H. Kropsot, Multiple Layer Insulation for Gyogeni Appliations, Gyogenis pp [10]S. Jaob, S. kasturirengan and R. Karunaniti, Investigations into te Termal performane of Multilayer Insulation Cryogenis vol.- 3, No.- 1,pp , All rigts Reserved 136

Natural Convection Experiment Measurements from a Vertical Surface

Natural Convection Experiment Measurements from a Vertical Surface OBJECTIVE Natural Convetion Experiment Measurements from a Vertial Surfae 1. To demonstrate te basi priniples of natural onvetion eat transfer inluding determination of te onvetive eat transfer oeffiient.