Hacimlerin pasif ısıtma sistemleri olarak değerlendirilmesinde kullanılabilecek bir yaklaşım
A New approach for the evaluation of the thermal performance of rooms as passive heating systems
- Tez No: 19400
- Danışmanlar: PROF.DR. EŞHER BERKÖZ
- Tez Türü: Doktora
- Konular: Mimarlık, Architecture
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1991
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 133
Özet
ÖZET Bu çalışmada, hacimlerin pasif ısıtma sistemleri olarak değer lendirilmesinde kullanılabilecek bir yaklaşım geliştirilmiştir. Ge liştirilen yaklaşımın amacı, hacimlerde iç hava sıcaklığının yıllık değişimine bağlı olarak yıllık ısıtma sürelerinin belirlenerek, hacim lerin pasif ısıtma açısından gösterdikleri performansın değerlendiril mesi ve enerji tasarrufu ve ısıtma ekonomisi açısından ısıtma süresi ni minimize eden pasif ısıtma sisteminin seçimine ve dizaynına da ola nak sağlanmasıdır. Geliştirilen yaklaşımda; yıllık ısıtma sürelerinin saptanabil mesi için dış iklim koşullarına ait veriler ve pasif sistem öğelerine ait hesap değerlerinden yararlanılarak, hacimde herhangi bir ek.yapma enerji sistemi olmadığı koşullarda iç hava sıcaklıklarının saatlik değişimleri hesaplanmaktadır. Bu hesaplamaların yapılabilmesi için zamana bağlı ve tek boyutlu ısı geçişi denklemlerinin çözümünde sonlu farklar yöntemi kullanılmıştır. Geliştirilen yaklaşım dış iklim koşulları ve pasif sistem öğe lerinin değerlerine bağlı olarak mevcut bir hacim veya oluşturulan hacim alternatiflerinin pasif ısıtma sistemleri olarak değerlendiril mesine ilişkin yapılabilecek tüm uygulamalarda kullanılabilir nitelik tedir. Bu çalışma kapsamında istanbul yöresi için yapılan örnek uygu lama çalışması da bu sonucu vurgulamaktadır. - v
Özet (Çeviri)
SUMMARY A NEW APPROACH FOR THE EVALUATION OF THE THERMAL PERFORMANCE OF ROOMS AS PASSIVE HEATING SYSTEMS The aim of this study is to develop a new approach whicn can be used for the evaluation of the thermal performance of rooms as passive heating systems. The study consists of eight chapters. Chapter 1 In the first chapter the necessity for the reduction of mechan ical heating cost has been emphasised. In order to reduce mechanical heating cost, rooms should be designed as passive heating systems and their performance should be evaluated with respect to passive heating. Chapter 2 In this chapter, definition of the passive heating system is introduced and passive heating system variables are explained. A. Passive Heating System Under the conditions of mechanical heating system is not operated, a room can be considered as a passive heating system. B. Passive Heating System Variables Definition of the passive heating system can be done through the following variables: a. Location of the room, b. Dimensions and shape factor of the room, c. Orientation of the room, d. Optical, thermo physical and moisture transfer properties of the room envelope. a. Location of the room: Location of the room in a building determines the number of external wall elements surrounding the room and consequently effects the amount of heat gain or loss by means of external elements. b. Dimensions and shape factor of the room: The ratio of external wall length to room depth is call ed the shape factor of the - vi -room. The surface area of external walls which has an important effect on heat gain or loss, changes with the shape factor. c. Orientation of the room: Orientation is one of the most important passive system variables because of the variation of solar angles and solar radiation intensity with orientation. d. Optical, thermophysical and moisture transfer properties of the room envelope. Optical properties of the room envelope are; - absorbtivity, - transmissivity. Thermophysical properties of the room envelope are; - overall heat transfer coefficient, - transparency ratio, - time lag and - decrement factor. Moisture transfer must be taken into consideration because of the risk of condensation occuring within the room envelope. Chapter 3 In this chapter, the importance of the climatic comfort condi tions that must be created in the rooms are reviewed and secondly heating period is defined basing on both the indoor air temperature and outdoor air temperature. A. Climatic Comfort Climatic comfort for a person is defined as“condition of mind which expresses satisfaction with the climatic environment”. The indoor climatic elements are; - indoor air temperature, - mean radiant temperature, - indoor air humidity and - indoor air movement. Definition of climatic comfort with combinations of different values of climatic elements can be made by means of“Bioclimatic Chart”. The“Bioclimatic Chart”was constructed with relative humidity percentages as abscissa and dry-bulb air temperatures as ordinate. Other climatic elements located on the chart describe different cli matic human needs. B. Heating Period One of the primary health requirements in a room is to provide users' climatic comfort continually. However, climatic comfort condi tions in a room can not be met by only passive heating in a particular period of the year. In order to reach the required indoor climatic - vii -conditions, supplementary mechanical heating becomes necessary. Heating period covers the period in which during the mechanical heating systems are required in order to provide climatic comfort conditions for the users. Heating period may be defined by basing on the following cli matic elements: a. The lowest indoor air temperature value from the climatic comfort point of view, b. The outdoor air temperature. a. The lowest indoor air temperature value from the climatic comfort point of view is determined as 21°C by means of the“Biocli- matic Chart”. By taking as the basis the lowest indoor air tempera ture from the climatic comfort view point, heating period is defined as the period during which the indoor air temperature is under 21°C. b. Heating period may be defined by basing on outdoor air temperature values which are given by,. Turkish Standards,. Regulation For Protection Of Air Quality,. Codes of Municipal Police of Greater Istanbul. In this study, heating period is defined basing on outdoor air temperature which is given by Turkish Standards 2754. For example, according to TS 2754 outdoor air temperature value determining the beginning and ending of the heating period is 15°C for Istanbul region. Chapter 4 In this chapter the relationships of the passive heating system, climatic comfort and heating period are explained. Chapter 5 In this chapter, evaluation process for the rooms as passive heating systems is defined in general. In general, evaluation process consists of three steps: - determination of the criteria which can be used for evaluation, - determination of the performance level of the room with regard to passive heating, t deciding whether the actual performance level is satisfactory ac cording to the selected evaluation criteria. As well as to be applied to the rooms in use, the evaluation process can also be considered sub-process of the design process. Chapter 6 In this chapter, the criteria which are used for evaluation rooms as passive heating systems are explained and previous approaches which have been used for the evaluation of rooms are introduced and discussed. - viii -A. The criteria which are used for the evaluation of rooms as passive heating systems are described as follows: a. Climatic Comfort Conditions Optimum indoor climatic conditions are related to users, as well as to indoor climate and the built environment system. A passive heating system performs at the optimum level when it provides the optimum indoor climatic conditions for a possible longest section of the period of use and achieves the minumum deviation from the optimum indoor climatic conditions. Therefore, climatic comfort conditions are the main criteria for design and evaluation process. b. Optimal Values of the Passive Heating System Variables The combinations of the values of the passive heating system variables which provides the required climatic conditions in the rooms are the optimal combinations and define the optimally functioning passive heating system. Therefore, optimal values of the passive heating system variables are used as criteria sets in the evaluation process. c. Amount of Total Heat Loss Rooms as passive heating systems can also be designed and evaluated according to the criteria given below: - the room must provide minumum heat loss during the heating period. d. Heating Energy Use Per Unit Area Heating energy use per unit are may only be adopted as crite rion if it is given in the building regul ations. In Turkey, there are no resulations which give the lowest limit values for the heating energy use per unit area. e. Heating Period In this study, heating period has been used as an evaluation criterion. The criterion: The beginning and ending dates of the heating period basing on the lowest indoor air temperature value from the cli matic comfort view point should at least coincide with those of the heating period basing on the outdoor air temperature. With regard to energy conservation and heating economy the heating period basing on the lowest indoor air temperature value from the climatic comfort point of view should be shorter than the period basing on outdoor temperature. B. As the result of discussion on previous approaches, a new approach has been proposed because of the shortfalls of those approaches. - IXChapter 7 This chapter covers the steps of the new approach developed to be used for the evaluation of rooms as passive heating systems. This approach as well as being applicable rooms in use it can also be used in the design process from the standpoint of selecting suitable room alternative. Symbol A denotes the steps of the approach in the case of it is being considered as a sub-process of the design process. Symbol B denotes the steps of the approach in the case of it is being applied to those in use. (A1),(B1) Gathering Regional Climatic Data For the calculations included in the approach, it is necessary to take into consideration the outdoor climatic data such as solar radiation intensities, hourly air temperature values. (A2),(B2) Preperation of The Annual Variation Chart of The Outdoor Air Temperature The annual variation chart of the outdoor air temperature is prepared by finding the mean hourly values of outdoor air temperatures for a ten-year period. Then the values obtained were plotted on a chart having the days of the year as abscissa and hours of a day as ordinate. (A3),(B3) Determination of The Heating Period Basing On The Outdoor Air Temperature The heating period is determined according to TS 2754. For example in Istanbul the dates and hours on which the air temperature is below 15°C constitute the total heating period. Therefore the 15°C air temperature curves on the“Annual Variation Chart”are the bound aries of the heating period. (A4) Development of Room Alternatives By Basing On The Values of Passive System Variables 1. Assumptions on the location alternatives for the room. 2. Assumptions on the room dimensions and shape factor alternatives. 3. Assumptions on the orientation alternatives for the room. 4. Assumptions on the room envelope. (B4) Determination of the Values of Passive System Variables. (A5),(B5) Calculation of the Hourly Values of The Indoor Air Tempera ture In this approach, it is assumed that there is no supplementary heating or climatization system in the room. And, time dependent heat flow calculations to determine indoor air temperature and inner sur face temperatures are basing on the finite difference method. Thus,the indoor air temperature at any particular time can be calculated by means of the following equation: at n m m l* = *1 + Eqj ^Vi^oi^i) + fW^rV + bhf W + % + Qk) t| : indoor air temperature at any particular time, °C tj : indoor air temperature before a time increment At,°C At : time increment, h. m : mass of the air in the room, kg c^ : specific heat of the air, J/kg°C n ^Vi^ofV'' amount of heat exchange between the indoor air and the 1 inner surfaces of opaque components of the envelope within the time increment, At,W. EA a-(tc^-t. ): amount of heat exchange between the indoor air and 1 ^ inner surfaces of transparent components of the envelope within time increment, At, W. bn : absorbtivity coefficient of the indoor air which is transmissed through the transparent components, m z(I.A ) : amount of solar heat gain from the transparent compo- 1 T p nents within the time increment, At, W. Q : amount of heat exchange between the indoor environment and outdoor environment by means of ventilation and infiltration within the time increment, At, W. Q^ : amount of heat gain to the indoor air from the heat sources in the room within the time increment, At, W. (A6),(B6) Preparation Of The Annual Variation Chart of Indoor Air Temperature Occuring In The Room Alternatives/Room The annual variation chart of indoor air temperature is prepared by means of hourly values of indoor air temperature. The values calculated were plotted on a chart having the days of the year as abscissa and hours of a day as ordinate. (A7),(B7) Determination of heating periods in the room alternatives by taking as the basis the lowest indoor air temperature value from the climatic comfort point of view. The dates and hours on which the indoor air temperature is below 21 °C constitute the heating period. And accordingly, the 21 °C inside air temperature curves on the annual variation chart also the boundaries of heating period. (A8),(B8) Comparison of the heating period determined by taking as the basis the lowest indoor air temperature value from the climatic comfort point of view, with the heating period basing on the outdoor air tem perature and evaluation of the performance of room/rooms from the stand point of passive heating. As the result of the comparison of the heating periods a room (or rooms) meets the heating period criteria can be regarded as a passive heating system which achieves the required performance. - xi -(A9) Determination of the Most Appropriate Room With Regard to Passive Heating. The room which provides the shortest heating period among dif ferent room alternatives is qualified as the most appropriate one. Chapter 8 This chapter covers the application of the approach to the Istanbul region and the results of the application. The results of this study are as follows:. By means of the approach which has been developed in this study it is possible to investigate the annual thermal behaviour of the rooms and to determine the beginning and ending date of the heating period.. This approach can be used to revise the regulations which deter mine the values of outdoor temperatures at which the mechanical heating should be turned on.. By means of this approach, the optimal combinations of the values for the passive heating variables can be determined.. This approach, as well as being applicable to the rooms in use it can also be used in the design process.. In this approach the temperature distribution within opaque components has been calculated under unsteady-state conditions by using the finite difference method. Therefore, more realistic results can be obtained. - XII -
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