SIMULATION OF BUILDING WITH TRANSPARENTLY INSULATED WALLS IN EDIRNE/TÜRKIYE

Transcription

1 rakia Journal of Sciences, Vol 7, Sul, 6-66, 9 Coyright 9 rakia University Available online at: htt://wwwuni-szbg ISS (rint) ISS (online) Original Contribution SIMULAIO OF BUILDIG WIH RASPARELY ISULAED WALLS I EDIRE/ÜRKIYE Semiha Kartal, ürkan Göksal Özbalta,ecdet Özbalta 3 * rakya University Faculty of Engineering and Architecture, Edirne, urkey Ege University Engineering Faculty Civil Engineering Deartment, urkey 3 Ege University Engineering Faculty Mechanical Engineering Deartment, urkey ABSRAC he rate of energy consumtion is rising raidly due to oulation increase, urbanization, consumer tastes, industrial activity, transortation and etc Increasing oulation means construction more buildings, which rises energy consumtion he annual increase in oulation in urkey is determined as about 5 % and, in arallel, building construction also gets increased he increase in building construction was 79% between 985 and When the distribution of energy consumtion in various sectors in urkey is examined, it has been seen that the industry and building sectors have the biggest rates among the others It is generally admitted that most of energy loss in building elements arises due to walls and roofs herefore, the solution in reventing the heat loss is the alication of the insulation materials on the external walls hermal insulation in buildings rovides energy saving and a comfortable and hygienic indoor climate at low ambient temeratures Oaque insulation materials only reduce the heat loss from the inside of the building to the outside But transarent insulation material has the roerty of being transarent to solar radiation while at the same time acting as heat insulation ransarent insulation does not only resent savings in heating costs, but it also increases the thermal comfort, as the wall temerature is often higher than the indoor temerature Furthermore, the troubles such as moisture and mould can also be revented with the alication of transarent insulation because of the higher temerature on the wall inner surface In this study, the thermal behaviour of transarent insulated external wall construction is investigated under Edirne-urkey climatic conditions Key Words: oaque insulation materials, transarent insulation material IRODUCIO oday, energy consumtion is continuously increasing because of oulation, urbanization and industrialization A significant art of the consumed energy is based on fossil sources such as coal, etrol, natural gas However, the most significant roblem in consequence of the consumtion of fossil energy sources is global climate change herefore, the most imortant art of the national energy strategies is energy saving Energy consumtion is generally examined under four main sectors such as industry, buildings, transortation, and agriculture he consumed energy in buildings is about 3% in total energy consumtion In the most countries, energy consumtion for heating is about 4% of the consumed energy in buildings (able ) * Corresondence to: Semiha Kartal, rakya University, Faculty of Engineering and Architecture, Edirne, urkey; tel: (84) 67/35; semihak@trakyaedutr

2 able Distribution of energy consumtion in buildings [,] Sace Water Air condition Lighting Cooling Other heating heating ventilation illumination freezing Houses Commercial About 35% heat lose in buildings comes about through exterior walls (able ) able Distribution of heat loses in buildings [,] Exterior walls Roof Window Floor Infiltration % 35 % 5 % % % 8 Insulation alications on exterior walls and heat gain through solar energy are considerable methods for diminishing energy consumtion for heating RASPARE MAERIALS (IM) ISULAIO Oaque insulation materials have generally been used for the insulation of exterior walls But these materials do not transmit solar energy ransarent insulation materials have been alied on massive walls to increase insulation roerties of buildings and to gain heat from solar radiation he massive walls on which transarent insulation has been alied work like solar collector Absorbed solar energy is stored in massive walls he heat lose from exterior wall is fairly low because of transarent insulation herefore, a significant art of the stored energy has been transferred to interior volume Heat conductivity coefficients of transarent insulation materials change between,6 and, W/m K deending on thickness and tye of material [3,4,5] And the solar radiation ermeability is about 7% Advantages have been sulied by using transarent insulation By transarent insulation, some benefits are obtained which are increase in exterior wall insulation and thermal comfort, decrease in facade condensation, lag on solar heat gain, alicable on existing building and increase in heat storing caacity of massive walls However, excessive heat may aear during summer months MAHEMAICAL MODEL When the model is established, it is assumed that there is one-dimensional transient heat conduction in wall construction and governing equation may be written as [6] ( / t) = α *( / x ) () (x,t) is the temerature t and x stands for the time and sace coordinates, α is the thermal diffusivity When the absortion of the solar radiation is taken into account; from the energy balance, the heat-flux in the outer surface(x=) of the wall is: q out (t, )= α g *I(t)+ h out *[ out (t)-(t,)] () I(t) is the total solar radiation incident on the wall surface, α g is the absortion of the outer wall surface for solar radiation, h out is heat transfer coefficient between the outer surface of wall and outdoor, out (t) denotes outdoor temerature, (t,) is the outer surface temerature he heat-flux in the inner surface of the wall is: q in =h in *[(t,l)- in ] (3) h in is the heat transfer coefficient between inner sace and inner surface of the wall, in denotes indoor temerature, (t,l) is the inner surface temerature of the wall In the study, the daily thermal behaviours of transarent insulated wall constructions that have been tested under current climatic conditions are simulated he one-dimensional transient heat conduction equation is solved by emloying an exlicit finite-differences rocedure taking into account the thermohysical characteristics of the layers Using the energy balance method, the exlicit finite-difference equations are derived for the boundary node on the outside surface, interface nodes between layers, interior nodes inside the layers, the boundary node on the outside surface he resulting finite-difference equations are given as follows:

3 he boundary node () on the outside surface: [ Fo( + Bi )] + Fo + Fo Bi S + = (4) Fo = α Δt and Bi = hout Δx / k and sol-air temerature S is defined as follows: = ( t) + α I( t) / h (5) S out g out Interface node (i) between different layers (K) and (K+): k + ( k B [ B + ( k + ( k + ( K i K + i+ i K K + / Δ i = x)] (6) B = ( K K K + K + ρ C Δx + ρ C Δx) / Δt Interior node (j) inside the layer (M): ( Fo ) + Fo ( + ) + j j M M j j+ = (7) Fo M = α Δt M he boundary node (n) on the inside surface: + n [ Fo ( + Bi )] + Fo + Fo Bi = n n in (8) Fo = α Δt and Bi = hin Δx / k FIDIGS he set of the finite-differences equations is solved iteratively by using the Gauss-Seidel iteration method he stability criterion belonging to every layer has been taken into account in solutions he hourly variation ambient temerature is between -44 and 56 C In January condition, daily solar radiation incident on a horizontal surface and on the wall surface are 468 MJ/m, 356 MJ/m resectively he climatic condition for January in Edirne is shown Fig 64

4 KARAL S et al emerature (C) ime (Hour),6,4, Solar radiation (MJ/m h) Solar radiation emerature Figure Variation of climatic data in Edirne he average temeratures of outer and inner surface are 83 C and 99 C, resectively (Fig ) emerature (C) ime (Hour) Outer surface Inner surface Figure Hourly variation of thermal behaviour of transarently insulated wall he maximum and minimum temeratures of the outer surface of transarently insulated wall are 55 C and 684 C resectively, as 958 C and 833 C are found out resectively on the inner surface of transarently insulated wall A transarently insulated wall works like solar collector herefore efficiency of transarently insulated wall is the ratio of heat-flux in the inner surface to solar radiation on the wall surface Efficiency of transarently insulated wall is lotted as a function of ( in - out )/H H is hourly solar radiation incident on a wall surface Efficiency -, -, -,3 -,4 -, y = -,533Ln(x) +,494 R =,9344 -,6 (in-out)/h Figure 3 hermal efficiency of transarently insulated wall rakia Journal of Sciences, Vol 7, Sul, 9 65

5 DISCUSSIO AD COCLUSIO ransarently insulated walls are the significant comonents in assive solar buildings Contrary to conventional oaque insulation, a transarently insulated wall not only reduces transmission losses of a building wall, but also heats the room behind the I wall Using transarent insulation materials, it is ossible to decrease the heating demand Furthermore the increase of the interior surface temerature contributes to the thermal comfort of the room he temerature of the wall is above ambient temerature for most of the time REFERECES Bakos, GC Insulation rotection studies for energy saving in residential and tertiary sector, Energy and Buildings ; 3: 5-59 Özkahraman, H, Bolattürk, A, he use of tuff stone cladding in buildings for energy conservation, Construction and Building Materials, 6; ; Chattha JA Comuter simulation of transarently insulated buildings for energy evaluation Architectural Science Review ; 44: Yang H, Zhu Z, Burnett J Simulation of the behaviour of transarent insulation materiels in buildings in northern China Alied Energy ; 67: Matuska A simle trombe wall comarion of different glazings, Proceeding of ISES Congress, EuroSun,, Coenhagen 6 Incroera FP, DeWitt DP Fundamentals of heat and mass transfer John Wiley and Sons;