Engelli Hacimlerde Verim Yöntemi İle Aydınlatma Hesabına Engel Faktörünün Belirlenmesi

Abstract

İç aydınlatma sistemleri için çoğu aydınlatma tasarımcısının kullandığı en basit ve en kolay yöntem verim yöntemidir. Ancak verim yöntemi aydınlatılacak hacmi boş kabul etmektedir. Oysaki, aydınlatma sistemi devrede iken hacimlerde insanlar ve eşyalar bulunmaktadır ve bunlar çalışma düzlemi ortalama aydınlık düzeyini dikkate alınması gereken miktarda azaltmaktadır. Literatürdeki çalışmalar, düzlemsel yüzeyli de olsa herhangi bir engel veya yerleşimin olduğu hacimlerde Engel Faktörünün (EF) değerini tasarımcıya net olarak söyleyememektedir. Engel Faktörü, hacim engelli iken çalışma düzlemi ortalama aydınlık düzeyinin, boş olduğundaki değerine oranı olarak tanımlanmaktadır. Bu tez çalışmasında engel içeren hacimlerde düzlemsel yüzeyli herhangi bir engel yerleşimi durumunda Engel Faktörünün değeri belirlenmeye çalışılmıştır. Bu amaç için kurulan bir test odasında, önce tanımlanan elemanter bir engelin çalışma düzlemi ortalama aydınlık düzeyine etkisi incelenmiştir. Çalışma, engel fotometrik yansıtma katsayısının (pe) 0.8, 0.52 ve 0.07, armatür açıklık-yükseklik oranının (AYO) 0.73 ve 1.1, engel yüksekliğinin (he) 0.8m, 1.0m, 1.3m ve 1.6m değerleri için test odasında çalışma düzleminde aydınlık düzeyi ölçümleri yapılarak gerçekleştirilmiştir. Bu iki boyutlu engellerle yapılan incelemeler yanında, oda içine üç boyutlu engeller yerleştirilerek incemeler de yapılmıştır. Üç boyutlu engellerle yapılan incelemelerde engel fotometrik yansıtma katsayıs (pe) 0.52 ve 0.07, armatür açıklık-yükseklik oranı (AYO) 0.73 ve 1.47, engel yüksekliği (he) 0.8m ve ortalama engel yüksekliği (heort) 1.5m değerleri gerçekleştirilmiştir. Engel sayısının birden fazla olduğu çeşitli durumlarda ve değişik engel tiplerinde yapılan ölçümlerden yararlanılarak, EF'nin değişimi, engel yoğunluğunun bir ölçüsü olan dikey engel yüzeyi oranının (DEYO) fonksiyonu olarak, pe ve AYO 'nun yukarıda belirtilen değerleri için lineer fonksiyonları biçiminde modellenmiştir. Lineer fonksiyonlarda bağımsız değişken DEYO olup, fonksiyonun diğer iki katsayısı engel yüksekliğinin DEYO ağırlıklı ortalamasının ikinci dereceden bir polinomu şeklindedir, ikinci dereceden polinomun katsayıları her bir pe ve AYO çifti için hesaplanmıştır. Elemanter engeller ile bulunan EF modelinin, üç boyutlu engeller kullanarak oluşturulan EF modeli ile karşılaştırılması sonucunda, elemanter engellerle hesaplanan EF değerinin üç boyutlu engel içeren hacim durumlarında da yeterli bir doğrulukla kullanılabileceği saptanmıştır.In interior lighting design, average illuminance at working plane is still the basic design criteria for most of the lighting designers. There are average working plane illuminance values depending on the type of activities taken on the spaces (rooms, offices, reading rooms etc). If the advised working plane illimunance value is not obtained, not only the expected performance for the activity will not be reached but also it would be harmfull to eyes' health of the people in the environment. In practice, the coefficient of utilisation method that is used by most of the lighting designers assumes the space to be empty. Basic formula for this method is, = QLnlumr1m avg c where Eavg is average working plane illuminance, niT is number of luminaires, r) efficiency, m is maintanence factor, S is working plane area. In fact, there are some objects and human in the space. Such things in the space causes the reduction on the average working plane illuminance by preventing some of the light flux reach to the working plane. This reduction depends on the spcing to higth ratio of luminaires (SHR), obstruction density, obstruction height, and fotometric reflectance of obstruction, type of luminaire, orientation of the luminaire and obstructions. Depending on the values of these variables, reduction may reach to unexpected ratios. At the literature, this reduction may be up to 20 per cent depending on the spesific values of the above variables. To compansate this reduction caused by obstruction the space, number of the luminaire power of the lamps may be increased. This compansation must be done at the beginning of the design precess. Used lighting design programs and methods obtain average working plane illuminance by averaging point by point illuminance values at the working plane. If the designer decides that the obtained average value is lower than suggested value, he/she increases the number of luminaires or increase the power of the lamp and rearrange the luminaires locations ( if necessary). Then he/she repeats the calculations. By applying this itterative design process, advised average working plane illuminance is obtained in obstructed or empty space. To reduce the duration of this iterative design process, expected obstruction factor may be used as a multiplier in basic coefficient of utilisation formula explained below. = 3>L nlum T] OF m avgobs o V. / XVI where Eavgobs is average working plane illuminance in obstructed space, OF is obstruction factor. In the literature, Obstruction Factor (OF) defined as ratio of average working plane iluminance in obstructed space to the empty space's average working plane illuminance, may vary between 0.6 - 0.9. Chosen value in this interval depends on the experience of the designer and there is no any certain criteria to decide the vaue of OF. In an other approach, spaces and obstructions are classified and experimental and computatinal OF values are obtained for these classifications. These classifications include three types of standart obstruction : light, medium, heavy. In obstructed spaces variables; SHR, obstruction density, height of obstructions and fotometric reflectance of obstruction, type of luminaires, orientation of the fixtures and obstructions are changed to perform computational and experimental studies for OF. The obtained results are only valid for such spaces including standart obstructions. In case of non-standart obstructions this method can not estimate OF values. The aim of this thesis is to investigate the average working plane illuminance in non-standart obstructed spaces. This investigation completely based on experimental work. OF is function of variables, SHR, obstruction density (oaen, VFR) and fotometric reflectance of obstruction (p0t>s), type of luminaire (lt), oriantation of the luuminaire (1OT) and obstructions (oOT) (paralle or vertical to each other). OF = ^i (S.3) F Eavgobs = Eavg OF (S.4) Op = f(Pobs> SHR, lt, lor, hobs, pobs, oden, oor, ot) (S.5) df 8î öf öf dOF = - dp",. + - dSHR + - dh^^do. (S.6) Partial derivatives in equation (S.6) are known as sensitivities of OF for the related variables. Sensitivities must be calculated for non-countable variables(for each type, location or etc.). Equation (S.6) gives variation on EF in terms of sensitivitiees of OF and partial variations on of variables. The room which is constructed for the study has dimensions of 5.34m,4.7m,3m. All surfaces of the room are painted to obtain diffuse reflective surfaces. Diffuse reflectance of the ceilling and wall surfaces is 0.87 and floor reflectance is 0.35. In this study these reflectances are kept constant. Luminaires which are used in this study have the polar photometric intensity distribution shown in Fig S.l, are located at ceiling so as to obtain 0.73 and 1.1 for SHR. XVII Fig S.l Polar photometric intensity distrbution of luminaire at C planes. First of all an elemantary obstruction is defined and the effect of this obstruction on OF is evaluated by moving the obstruction in the quarter room. Dimensions of the elementary obstruction are 1.2 m length, 0.01m width and 0.8m to 1.6 m height. Fotometric reflectances of the obstruction are 0.8, 0.52 and 0.07. The location of the obstruction is changed in the room but not near the walls. When the obstruction is not near the walls, Detailed measurements showed that the effect of obstruction on average working plane illuminance is independent of the position of the obstruction. OF values for same p0bs and AYO may be averaged to find brief results in the case of single elemantary obstruction (Table S.l). In the study, variables that can be expressed numerically ( spacing to heigth ratio, obstruction density etc..) are taken as parameters and sensitivities of OF for these variables are obtained. For single obstruction mode, sensitivities are calculated by using Table S.l. For an obstruction, the variation of OF is given as a function of obstruction height for constant obstruction reflectance and limunaire spacing to height ratio. It is shown that the OF is linearly proportional to number of obstructions provided that obstruction parameters are kept the same. OF fuunction under this assumption is: OFn=[l-n(l-OF)] (S.7) Where OF is obstruction factor for one obstruction in the space, OFn is obstruction factor when there are n obstruuctions in the space. XVIII When there are different obstructions in the space, (S.7) is not valid for the calculation of OF. Table S.l Brief OF measurement results To obtain a proper model to evaluate OF for spaces including general planar obstructions, VFR variable must be included. A linear function approach meets for fitting measurement points. In this case, OF function is : OF = A + B * DEYO (S.8) For cases where the number of obstruction is more than one, OF is expressed as a function of vertical obstruction surface ratio (VFR) (S.8) for average constant obstruction heigths, obstruction reflectances and spacing to heigth ratios. These functions are obtained for obstruction reflectances values: 0.8, 0.52 and 0.07, obstruction heigth values of 0m, 0.8m, lm, 1.3m and 1.6m, spacing to height ratio values of 0.73 and 1.1. OF value can be interpolated in these variables valid ranges. Since these obtained functions are not based on standart obstruction and standart lay out of obstructions, they can also be used for non-standart planar obstructions XIX Table S. 2 Measurements for multi-obstruction modes In expression (S.8) A and B coefficients can be calculated for obstruction height. After investigations, second order polynomials are obtained [(S.9)-(S10)]. These polynomial' coefficients are shown in Table S.4. A - a0 +a,hobs + a2hobs (S.9) B = b0+b,hobs+b2h20 (S.10) Application of OF model, (S-8)-(S-10), on measurements in Table S.2 obstruction type 3 and 4, gives acceptable results. Type 4 belongs to a cube an open top cube in both cases accuracy obtained by model is %2-3. Search results of are given in Table S.3 and Table S.4 briefly. In these tables hobsavg is VFR weighted average height of obstructions. In addition to this investiagtions using elemantry based obstructions which are of two dimensional panels, three dimensional obstructions are included also. Related results of this search is similar to search results based on two dimensional obstructions. Results for three dimensional search is given in Table S.5 and Table S.6. By these investigations on OF, evalulation of OF value is possible in obtsructed spaces. XX Table S.3 OF=A+B*DEYO functions at various modes Table S.4 A, B polynomials depending on hobsavg for the OF=A+B*DEYO functions XXI Table S. 5 OF=A+B*DEYO functions at various modes of three dimensional obstructions Table S.6 A, B polynomials depending on hobsavg for the OF=A+B*DEYO functions of three dimensional obstructions In the following Table S.7 comparesion of OL models Table S.4 and presented by Table S.6 is presented. In this table two cases include three dimensional obsructions in a room which has different VFRs and SHR values. In this table column OL2D is obtained by model in Table S.4 ie in the case of elemantary obstructions and OL3D is obtained OL model in Table S.6 ie aplication of directly aplication of three dimensional obstructions. Table S.7 Comparing OL values calculated by two different models As a result in obtaning of OL model and its appliactions, approach of using elemantary obstructions are good enough to give good results in OL calculations. By the applications of such kind of OL models and elemantry obstructions OL models can be easily obatined and easily applied for real lighting indoor problems.