DETERMINATION OF OPTIMUM THERMAL INSULATION THICKNESSES CONSIDERING THE SEASONAL ENERGY REQUIREMENTS

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1 DETERMINTION OF OPTIMUM THERML INSULTION THICKNESSES CONSIDERING THE SESONL ENERGY REQUIREMENTS O. KYNKLI, 2 K. SK, 3 Z. KYNKLI,2,3 Mecanical Engineering Department, Faculty of Engineering, Univerity of Uludag, Bura, Turkey kaynakli@uludag.edu.tr, 2 kenanaka@uludag.edu.tr, 3 zkaynakli@otmail.com btract In ti tudy, an optimization of te termal inulation tickne applied to te external all of building a been carried out baed on te eating and cooling and te annual energy requirement conidering olar radiation effect. Ti tudy a been performed for Itanbul, Turkey. Itanbul i located in te econd climatic region in Turkey it HDD=372, CDD=524. By determining te ol-air temperature conidering air temperature and olar radiation vale for Itanbul and maximizing te annual energy aving, te optimum termal inulation ticknee ave been calculated. Te effect of olar radiation on eating-cooling energy requirement, te variation of optimum inulation ticknee it degree-day, te difference beteen te analye baed on eaonal and annual ave been preented in tabular and grapical form. Keyord Inulation tickne; pace eating-cooling; ol-air temperature. I. INTRODUCTION In many countrie, te energy requirement for pace eating and cooling in building (bot ouing ector and commercial-indutrial building) a te iget are of all ic i about 50% of total energy conumed in building (Ozkaraman and Bolatturk 2006). For tat reaon, great amount of aving from eating or cooling energy requirement i poible by applying termal inulation to building. Te optimum termal inulation tickne depend on te cot of inulation material, building lifetime, coefficient of performance of te cooling equipment, efficiency of te eating ytem, te cot of energy ource, and prevailing inflation and interet rate, in addition to tee, it primarily depend on te eating and cooling load of te building. For tat reaon, tee load ould be determined accurately. Te eat load from olar radiation a a ignificant effect on te eating and cooling load of a building. In mot tudie, oever, te olar radiation on building all a not conidered in te calculation of optimum inulation tickne. In te literature, tere are many tudie dealing it optimum inulation tickne for building (Bolatturk 2006; ytac and koy 2006; Comakli and Yukel 2003; Siman et al 2007;Ucar and Balo 200; Haan 999), or refrigeration application (Soylemez and Unal 999; Uta and Ileri 999). ytac and koy (2006) and Bolatturk (2006) calculated te optimum inulation ticknee for different DD zone in Turkey conidering eating energy requirement of building. Hoever, te effect on te cooling energy requirement on te inulation ticknee and te olar radiation ere not invetigated in tee tudie. ***bot te eating and cooling load ere not conidered togeter in te calculation of optimum inulation tickne, and te effect of olar radiation on tee load ere not invetigated. In ti tudy, taking into conideration te paceeating and cooling load togeter, te optimum inulation ticknee ere calculated for Itanbul. Intead of air temperature, te olar-air temperature ic conider te incident olar radiation on a all a ued in te calculation of eating and cooling tranmiion load. Te annual eating and cooling DD ere calculated uing recent (about 5 yearmeaurement) outide air temperature for eac conidered city. II. MTHEMTICL MODEL Degree-day and olar radiation Degree-day metod aume tat te energy need for a building are proportional to te difference beteen te daily mean outdoor temperature and te bae temperature. Conidering te olar eat gain troug te external all of a building, te annual eating and cooling degree-day (HDDand CDD) can be expreed a follo (Bolatturk 2008) 365 T b T ol air HDD () 365 T ol air Tb CDD (2) een above eq. () and (2), te HDD and CDD value are dependent on te ol-air temperature. Te ol-air temperature i a concept relating to te outide air temperature and te olar radiative flux, and defined a (Cengel 998) 4 q T o Turr 4 Tolair To (3) o o Being conervative, te olar aborptivitie (α ) of ligt- and dark-colored urface are taken 0.45 and 0.90, repectively. Recommended ummer and inter deign value for eat tranfer coefficient on outer Proceeding of 68 t Te IIER International Conference, Barcelona, Spain, 3 t pril 206, ISBN:

2 Determination of Optimum Termal Inulation Ticknee Conidering te Seaonal Energy Requirement urface of a building are o = 22.7 W/m 2 K and o = 34.0 W/m 2 K repectively. Te olar radiation incident on a urface depend on urface gradient (lope) and orientation. Firtly, te daily olar radiation on a orizontal urface i determined, ic i given by q q a b S o, S 0 Te coefficient a and b are a function of olar declination angle (δ) and latitude of te ite ( ) and altitude (Z) (Kilic and Ozturk, 983) Te montly average daily extraterretrial radiation on per unit of orizontal urface can be computed a follo Gc 360 q o, 0.033co n co co in in in (5) ereg c i te olar contant, ω i te unet our angle for te mont, and n i te day of te year. Te olar contant i given a 367 W/m 2 (Sukatme 999). Te declination angle and te unet our angle are determined a (Duffie and Beckman 99) (4) in 284 n 365 co tan tan (6) (7) In addition te urface lope, it orientation a a ignificant effect on te falling olar radiation. Te orientation of te urface i expreed it te urface azimut angle (γ). R b i te ratio of te daily direct radiation for loping and orizontal urface, and it alo varie according to urface azimut angle. R b, for example for a urface facing out, i given by co in /80 in co in R b co co in /80 in in (8) Incoming olar energy on vertical urface uc a all can be calculated from te folloing equation. q co co, d q q Rb q, d q q 2 2 (9) ereβ i te urface inclination angle and β = 90 for vertical urface, ρ i te ground reflectance, ic i conervatively aumed to be 0.2. nnual eating and cooling energy requirement Te tructure and propertie of external all conidered in ti tudy are given in Table.Heat lo and gain troug a unit area of te all are repectively, q (0) q U T b T ol U T ol T air air b () In term of degree-day, te annual eating and cooling energy requirement per unit area becaue of te eat lo from te all can be expreed a follo q H, HDDU / 86400CDDU / COP (2) q C, (3) erecop i te coefficient of performance of te cooling ytem. COP depend on te operating parameter, but on te average, it i aumed to be 2.5 (Soylemez and Unal 999; Bolatturk 2008). Te overall eat tranfer coefficient of a typical external all tat include a layer of inulation i given by U / R x / k / R x k (4) i o t, / Table. Te parameter ued in te calculation Proceeding of 68 t Te IIER International Conference, Barcelona, Spain, 3 t pril 206, ISBN:

3 Determination of Optimum Termal Inulation Ticknee Conidering te Seaonal Energy Requirement Energy cot and optimum inulation tickne In ti tudy, te life cycle cot (LCC) analyi i ued in te energy cot calculation. LCC analyi calculate te total cot of eating/cooling over te lifetime (LT in year). uming an inflation rate (i), an interet rate (g) and an expected lifetime, te preent ort factor (PWF) i calculated a (l-sanea et al 2003) PWF LT i i (5) g i g Te annual total (eating and cooling) cot and te optimum inulation tickne are given by 86400HDD C f PWF 86400CDD Ce PWF Ct, Cin x R x / k Hu R x / k x 86400PWF t, t, COP C HDD / Hu C CDD / COPk / 2 f e opt, Rt, C in Inulation ued on external all decreae not only te eating cot but alo te cooling cot. For tat reaon, from an economic point of vie, bot te eating and cooling energy requirement ould be conidered togeter en calculating te optimum inulation tickne. k (6) (7) III. RESULTS ND DISCUSSION Te HDD (T b =8 C) and CDD (T b =24 C) value conidering and not conidering olar load for Itanbul are given in Table 2. Wen calculating te firt value (i.e. it aterik) for degree-day in ti table, te olar load i not conidered. Wen te eat load caued by olar radiation on te urface i added in te calculation (i.e. itout aterik), te eating load in inter eaon i obtained maller and te cooling load in ummer eaon i obtained greater (HDD<HDD* and CDD>CDD*). Table 2 clearly indicate tat te olar radiation a a ignificant effect on bot te eating and cooling load. Table 2. Te HDD and CDD value * Te degree day ere calculated itout taking into account of ol-air temperature Te variation of eating and cooling degree-day it mont i on in Fig. for te bae temperature of 8ºC and 24ºC repectively. effect of te inulation cot in te annual total cot decreae. Ti decreae caue ticker inulation tickne. Terefore, x opt, >x opt,h or x opt, >x opt,c are obtained. Fig.. Variation of montly degree-day Te effect of inulation tickne on te annual eating and cooling energy requirement per quare meter of all i on in Fig. 2(a). Te variation of cot curve it inulation tickne, and te determination of optimum inulation ticknee according to different approace (eating total cot, cooling total cot or annual total cot) i on in Fig. 2(b). Te inulation tickne minimizing te total cot i taken a te optimum inulation tickne). dding more inulation decreae bot te eating and cooling tranmiion load (eating and cooling cot) togeter. a conequence of ti, te Fig. 2 (a) nnual eating or cooling tranmiion load and (b) eating and cooling cot variation it inulation tickne Proceeding of 68 t Te IIER International Conference, Barcelona, Spain, 3 t pril 206, ISBN:

4 Determination of Optimum Termal Inulation Ticknee Conidering te Seaonal Energy Requirement In general, te variation of optimum inulation ticknee it degree-day i on in Fig. 3. Te optimum inulation ticknee increae (but not linearly) it increaing DD value becaue of te fact tat ig DD value mean te ig energy requirement (eating or cooling). It i alo een in ti figure tat x opt, i greater tan x opt,h and x opt,c a mentioned above. On te oter and, x opt,c i iger tan x opt,h for te ame degree-day value. Te reaon of ti i te unit cot of energy. For eating, te unit cot of energy i C f /(Hu.η) in USD/J, for cooling it i C e /COP in USD/kW. HDD eating degree-day, C HDD* eating degree-day conidering olar radiation, C Hu loer eating value of fuel, Jm -3 i inflation rate k termal conductivity of inulation material, Wm - K - K T clearne index LT expected lifetime, year n day of year PWF te preent ort factor q energy requirement per unit area, Jm -2 q mean daily olar radiation on per unit area of a urface, Wm -2 q mean daily olar radiation on per unit area of a loped (vertical) urface, Wm -2 R termal reitance of external all, m 2 KW - R b ratio of te daily direct radiation for loping and orizontal urface S day lengt S 0 maximum poible unine duration T temperature, C U overall eat tranfer coefficient, Wm -2 K - x inulation tickne, m Z altitude, m Fig. 3. Variation of optimum inulation ticknee it degree-day CONCLUSION In ti tudy, te optimum termal inulation ticknee on external all of building ere calculated baed on bot annual and eaonal energy load. Te effect of cae conidering and not conidering te incident olar radiation on eaonal eating/cooling load ere invetigated. Te reult o tat olar radiation greatly affect te eating and cooling load. Te inulation tickne calculation ould be carried out on te bai of annual energy requirement intead of only eaonal. Moreover, by uing te optimum inulation tickne, te annual energy aving reace up to 48%.Since te energy unit cot for cooling i greater tan tat for eating, te x opt,c i obtained iger tan x opt,h for te ame degree-day value. Nomenclature C cot, USD m -2 CDD cooling degree-day, C CDD* cooling degree-day conidering olar radiation, C COP coefficient of performance of te cooling ytem g interet rate G c olar contant, W/m 2 o combined convection and radiation eat tranfer coefficient, Wm -2 K - Greek ymbol α olar aborptivity of urface β urface inclination angle γ urface azimut angle δ olar declination angle ε emiivity of urface η efficiency of te eating ytem latitude of te ite ρ ground reflectance σ Stefan-Boltzman contant ω unet our angle for te mont unet our angle for inclined urface REFERENCES [] H.T. Ozkaraman,. Bolatturk, Te ue of tuff tone cladding in building for energy conervation, Contruction and Building Material 20 (2006) [2]. Bolatturk, Determination of optimum inulation tickne for building all it repect to variou fuel and climate zone in Turkey, pplied Termal Engineering 26 (2006) [3]. ytac, U.T. koy, Te relation beteen optimum inulation tickne and eating cot on external all for energy aving (in Turki), Journal of te Faculty of Engineering and rcitecture of Gazi Univerity 2 (4) (2006) [4] K. Comakli, B. Yukel, Optimum inulation tickne of external all for energy aving, pplied Termal Engineering 23 (2003) [5] N. Siman, E. Kaya, N. ra, H. ra, Determination of optimum inulation ticknee of te external all and roof (ceiling) for Turkey different degree-day region, Energy Policy 35 (2007) [6]. Ucar, F. Balo, Determination of te energy aving and te optimum inulation tickne in te four different inulated exterior all, Reneable Energy 35 () (200) Proceeding of 68 t Te IIER International Conference, Barcelona, Spain, 3 t pril 206, ISBN:

5 Determination of Optimum Termal Inulation Ticknee Conidering te Seaonal Energy Requirement [7]. Haan, Optimizing inulation tickne for building uing life cycle cot, pplied Energy 63 (999) [8] M.S. Soylemez, M. Unal Optimum inulation tickne for refrigeration application, Energy Converion and Management 40 (999) 3-2. [9] N. Uta,. Ileri Computerized economic optimization of refrigeration ytem deign, Energy Converion and Management 40 (999) [0]. Bolatturk, Optimum inulation ticknee for building all it repect to cooling and eating degree-our in te armet zone of Turkey, Building and Environment 43 (6) (2008) [] Y.. Cengel, Heat Tranfer: Practical pproac. McGra-Hill Inc. (998). [2]. Kilic,. Ozturk, Solar Energy(in Turki). Kipa Ditribution Inc., Itanbul, (983). [3] S.P. Sukatme, Solar Energy: Principle of Termal Collection and Storage. 2nd ed. Tata McGra Hill, (999). [4] J.. Duffie, W.. Beckman, Solar Engineering of Termal Procee. 2nd ed. J. Wiley and Son, Ne York, (99). [5] S.. l-sanea, M.F. Zedan, S.. l-jlan,.s. bdul Hadi, Heat tranfer caracteritic and optimum inulation tickne for cavity all, J Termal Envelope and Building Science 26 (3) (2003) Proceeding of 68 t Te IIER International Conference, Barcelona, Spain, 3 t pril 206, ISBN:

SENSITIVITY ANALYSIS FOR COUNTER FLOW COOLING TOWER- PART I, EXIT COLD WATER TEMPERATURE

SENSITIVITY ANALYSIS FOR COUNTER FLOW COOLING TOWER- PART I, EXIT COLD WATER TEMPERATURE *Citranjan Agaral Department of Mecanical Engineering, College of Tecnology and Engineering, Maarana Pratap Univerity