Effect of smoke tube constructions to boiler efficiency and furnace load at smoke tube boilers

Steam boilers are one of the most important examples of machines working on the principleof heat transfer. As a result of this heat transfer occurring due to the thermodynamicproperties of water, the water present in the boiler's body is converted into steam by transferof heat via convection from the flames in the furnace and the smoke gas passing through thesmoke pipes. The subject of this thesis is the attempt to increase the transfer of heat in thesmoke pipes by various constructions.Basically there are two methods of increasing the forced transfer of heat between the smokegas flowing inside the pipes and the water on the outside wall of the pipe. The first are activeprocedures and the second are passive procedures. Active procedures involve increasing heattransfer by using an additional external force. Passive procedures increase heat transferwithout the necessity for any external force. Winged pipes, composite (multi-layered) pipesand turbulators are amongst passive procedures. In order to increase the thermal capacity ofthe boiler the easy discharge of hot smoke gasses passing through the pipes should beprevented and heat transfer should be increased by either expanding the transfer surface orreducing and turbulating the flow by placing equipment called turbulators inside the pipes.In the experimental design I prepared as a simple exchanger I passed air heated by anelectrical air heater inside a pipe and passed water inside a larger pipe encompassing this pipeand measured the temperatures of incoming and outgoing air and water. I repeated thisprocedure first without placing any turbulatos inside the pipe then by placing 3 differentturbulators. Thus I obtained different heat transfer and efficiency values. I also performedexergy analysis on these values applying the 2. law of thermodynamics. Withing the scope ofmy findings I observed that turbulators placed inside the pipe increased thermal efficiency by10 to 12 %. Furthermore I found that there are disregarded increases on the exergy which isusable energy and 2. law efficiency. Even though there are some differences in efficiencybetween various turbulators, properties such as cost, ease of production and ease of cleansingshould be taken into consideration when choosing turbulators.Key words: Heat transfer, efficiency, turbulatorJURY:1. Prof. Dr. Galip TEM R (Supervisor) Acceptance Date: 20.06.20062. Prof. Dr. Olcay KINCAY Page: 923. Prof. Dr. Mesut ÖZGÜRLER