İklimsel Konfor Ve Enerji Ekonomisi Açısından Isıtma Sisteminin İşletme Şekline Bağlı Olarak Bina Kabuğunun Isıl Performansının Değerlendirilmesi

Abstract

Bu çalışmada; günün belirli saatlerinde kullanılan hacimler için, iklimsel konfor ve enerji ekonomisini sağlamak amacıyla, hacme ait kabuk elemanının ısıl performansının, ısıtma sisteminin işletme şekline bağlı olarak değerlendirilmesinde kullanılabilecek bir yaklaşım geliştirilmiştir. Bina kabuğunun; dış çevredeki iklimsel koşulların etkilerini kontrol altına alarak yapma çevreye aktardığı ve buna bağlı olarak kabuktan geçen ısı miktarının, hacmin iç yüzey sıcaklıklarının ve dolayısıyla bu yüzey sıcaklıklarının bir fonksiyonu olan iç hava sıcaklığının değişimine yol açtığı bilinmektedir. Buna göre, geliştirilen yaklaşımda kullanılmak üzere, ısı geçişi hesaplarının yapılabilmesi için dış iklim koşullarına ait veriler ve hacimde ek bir yapma ısıtma sistemi olduğu koşullarda, iç yüzey sıcaklıklarının saatlik değişimlerinin hesaplanabilmesi için de yapma çevreye ait dizayn değişkenlerinin değerlerinin belirlenmesi gerekmektedir. Bu hesaplamaların yapılabilmesi için zamana bağlı ve tek boyutlu ısı geçişi denklemlerinin çözümünde sonlu farklar yöntemi kullanılmıştır. Belirli aralıklarda kullanılan hacimler için, ısıtma sisteminin işletme şekline bağlı olarak bina kabuğunun dizaynlanması amacı ile, yapma çevre değişkenlerinin tasarım veya işletme aşamasında, en uygun kabuk detayı ve işletme şekillerinin seçilmesine olanak verecek şekilde kontrolü, geliştirilen yaklaşım ile olanaklı olabilecektir.

One of the primary requirements in a built environment for health is to provide users' bioclimatic comfort. To create an indoor climate which satisfies users' comfort while using supplementary heating in the most economical manner, the architect should pay attention to the determination of the optimum combination of design parameters affecting the indoor climate. Considering a space as the built environment, the most important parameter affecting indoor climate is the building envelope which separates the indoor space from the external environment and in this way, modifies or prevents the direct effect of climatic variables. Therefore, according to its storage capacity and its insulation resistance, the building envelope modifies also the effect of the heating system in the space. The aim of this study is the determination of an opaque component, in relation to the other design parameters by taking in account the heating systems from the standpoint of providing bioclimatic comfort conditions and energy conservation. The study consists of eight chapter: Chapter 1 In the first chapter, the importance of the building envelope and heating system and consequently the necessity for the energy conservation are emphasized. Chapter 2 In this chapter, definition of the climatic comfort is introduced and indoor climatic variables which influence bioclimatic comfort conditions in a room are analyzed. Climatic comfort conditions are defined as the condition in which, more than 80 % of users are satisfied. The architect should pay attention to realize the most convenient environment for the biological, psychological, social and cultural needs of users. The factor affecting climatic comfort are classified as follows:. Environmental factors - Air temperature - Mean radiant temperature - Indoor air movement - Indoor air humidity xv . Personal factors - Activity level - Clothing insulation value - Posture of the person in the room Definition of the climatic comfort with combinations of different values of climatic elements can be made by means of "Bioclimatic Chart". This "Bioclimatic Chart" was prepared for users which have 0.8 Clo insulation values and 1.3 MET activity level. Other climatic elements which describe the different climatic human beeings needs are also located on the chart. The relationships between climatic comfort and energy conservation are also explained in this chapter. If a supplementary heating system is required for a room, the amount of energy the passive heating system which runs optimally. Therefore in order to reduce mechanical heating cost, room should be designed as more convenient passive heating system and heating period should also be evaluated with respect to energy conservation. Chapter 3 In these chapter, the factor affecting indoor climate and energy conservation are analyzed. Considering all functions of users are realized in the rooms of a building, a climatic comfort needed by users can be defined for those rooms. Factors directly related to the room (design parameters) are as follows:. Room location in building Location of the room in a building, determines the number of external wall elements surrounding the room and consequently effects the internal air temperature which is a function of the amount of heat gain or loss through the external elements.. Dimensions of the room The ratio of external wall length to room depth is called the shape factor of the room. The surface area of external walls which influence the heat flow through the envelope and consequently the internal air temperature, changes due to the shape factor.. Orientation of the room Orientation is one of the most important passive system variables because of the variation of solar radiation intensity gain by means of external elements. xvi . Heat transfer properties of the room envelope Heat transfer properties of the room envelope are as follows: - Optical properties - Transparency ratio - Surface heat transfer coefficient - Thermal conductivity - Thermal transmittance - Thermal transmittance resistance - Overall heat transfer coefficient - Decrement factor and time lag. Mechanical heating system When needing a supplementary heating system, heating period should be determined according to the climatic comfort and energy conservation. Chapter 4 This chapter deals with the heat transfer through the building envelope. The heat flow through the external wall takes place in three ways:. Conduction. Convection. Radiation Methods for calculating the amount of heat transfer depending on the heat storage capacity of the external wall and heat flow variability according to the time are also explained. Chapter 5 These chapter sets principles and the steps of a new approach which can be use for analyzing the thermal performance of the building envelope according to the heating period and the climatical comfort. The main steps of the new method are as follows:. Determination regional and internal climatic data For the calculations used in the approach, it is necessary to take into consideration; both the outdoor climatic data according to the design day of the year and the indoor climatic data such as the indoor air temperature.. Determination of the values of design variables This step includes; the determination of the using period of the space, the location of the building according to the other building, dimensions of the xvii space, the absorptivity of the building envelope,the transparency ratio, the value of the required overall heat transfer coefficient of opaque component with respect to the orientation and the transparency ratio and the detail of opaque component which satisfied the required overall heat transfer coefficient. The limit value of the overall heat transfer coefficient can be determined by means of several graphics, obtained from some researches.. Determination of the heating period according to the using period of the room. Calculation of the hourly values of the inner surface temperature Considering that there was a supplementary heating in the room, the internal surface temperature of the opaque component at any particular time (toi ") was calculated by the following formula, by using the finite difference method. toi~iÂ^(~xr)i>5i 2^r~ ^ 2ts t°iAT^Lr - x± - 2) AT : time increment, s. Ax : distance increment (within the component), m. A, : thermal conductivity of the surface material, kcal/mh°C,W/m°C. b : absorptivity of the surface under consideration for solar radiation which is transmitted by transparent components. Sj : solar radiation intensity transmitted by transparent components and affecting the surface, kcal/m2h,W/m2. tj : comfort value of indoor air temperature, °C. t2 :the temperature of a point distanced Ax m from surface of the component before a time increment AT, °C. toi : internal surface temperature of the component before a time increment AT,°C. ffi internal surface heat transfer coefficient, kcal/m2h°C,W/m2°C.. Comparison of the inner and outer surface temperatures charts and evaluation of the opaque components according to heating period. The opaque component which provides the nearest value of the inner xviii surface temperature to the internal air temperature is qualified as the most convenient opaque component according to the heating system and climatical comfort. Chapter 6 This chapter consists of the application of the approach to the Istanbul region. Chapter 7 This chapter covers the results of the present study. Chapter 8 The results of this study are as follows:. Different heating period alternatives which are applied with the different opaque component alternatives cause the different climatical condition in the room.. Opaque components which have the same overall heat transfer coefficient, do not give the same climatical comfort conditions with the same heating period alternative.. In the case of removing the place of the insulation material in the opaque component, climatical comfort conditions are also changed. As a result, for the room which is used for a determined time in a day, designing an opaque component, needs to do all those analyzes according to the heating period with respect to the climatical comfort and the energy conservation.