Isıtma Cihazlarının Geçiş Fonksiyonları

Abstract

Ülkemizdeki ısıtma sistemlerinde doğal gazın yakıt olarak kullanılmaya başlanması ile birlikte bireysel ısıtma daha fazla tercih edilen bir uygulama haline gelirken radyatör kullanımında da önemli artışlar olmuştur. Bireysel ve merkezi ısıtma uygulamalarında değişik malzemelerden ve değişik tiplerde radyatörler kullanılmaktadır. Radyatör seçimindeki önemli kriterler maliyet, birim ısıl verim, kullanım ömrü, ısıtma sistemlerine uygunluğu ve rejime girme süreleridir. Enerji tasarrufu sağlaması açısından radyatörlerin rejime girme süreleri, seçilen ısıtma sistemine uygunluk ve birim ısıl verimleri son derece önemlidir. Bu çalışmada ısıtma cihazlarının ısıl davranışları incelenmiş farklı malzemelerdeki radyatör tipleri için transfer fonksiyonları çıkartılarak, bu fonksiyonların zaman sabitleri hesaplanmıştır. Sıcak su panel radyatöre girdiğinde, radyatörün kanalları içinde soğumakta olan suyla, arasında bir miktar karışma meydana gelecektir. Mükemmel karışımın belirtisi su sıcaklığının radyatör boyunca aynı sıcaklıkta olmasıdır. Panel radyatörün ısıl reaksiyonu;As the individual heating becomes a more preferred application within the beginning of natural gas usage at the heating systems in our country, there also have been increases in radiator using. Radiators of different materials and with different types are being used in individual and central heating. The most important creations in radiator selection is cost, thermal output per unit, life time, appropriateness to heating system and time constant. Time constant, appropriateness to the heating system chosen and thermal output per unit are very important in the case of saving energy. With this work, the thermal attitudes of heating equipment have been examined and the time constants of transfer functions found for the radiators of different types have been calculated. When hot water enters a panel radiator some mixing will occur between it and water already cooling in radiator's channels. The symptom of perfect mixing would be that the water temperature throughout the radiator. The equation for the thermal response of the panel radiator; CR =mwater cwater + mmetal cmetal Transfer function of systems is explained; The time constant of systems is explained; In some designs of low water content radiator, the radiator channels consist in fact of a small number of pipes bonded to the convector surface. Very little mixing would be expected to take place in such an arrangement. The equation for the thermal response of the aluminum radiator; Cm: Thermal capacity of metal = mmetal cmetal Transfer function of systems is explained; The time constant of systems is explained; In the much older column radiator the thermal mass of iron columns may not be correctly modeled by simply aggregating it with the water content as was inferred earlier for the steel panel radiator. In effect this gives two equations describing the radiator dynamics; Transfer function of systems is explained; The time constant of systems is explained; The risk of instability and system gain had been examined by comparing radiator output at different flow temperatures. The risk of instability therefore occurs at low load condition. The risk can be reduced by separately reducing the flow temperatures in accordance with external load. In addition to this it was given transfer function at fluctuations in water flow rate and fluctuations flow temperature by examining behavior of coils, embedded heating panels. For fluctuations in water flow rate: For fluctuations in water flow temperature: (? = ?c0/ v ) The BSRIA model estimates these time constants on the basis of length of tubes per circuit actively transferring heat, the number of tubes per header, the water velocity in the tube and the air velocity through the heat exchanger. It has been seen that the time constants of aluminum radiators are shorter than the other radiator types. Panel, iron and steel radiators are following aluminum radiators. Radiators, which have shorter time constant, will be adept to any changes in the systems.