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Boilers and Fired Systems
Published in Stephen A. Roosa, Steve Doty, Wayne C. Turner, Energy Management Handbook, 2020
Fire-tube and water-tube boilers have some key differences, which affect their operating characteristics and suitability for specific applications. Water-tube boilers require less floor space than fire-tube boilers for a given capacity. Water-tube boilers are available for higher pressures (~5,000 psig), whereas fire-tube boilers are generally limited to under 350 psig. Water-tube boilers are available with much higher capacities than fire-tube boilers. The output of fire-tube boilers is generally limited to a maximum of 20 million Btu/hour (600 boiler hp). Water-tube boilers are available in much greater output capacities. Because water-tube boilers have lower water mass within the boiler, water-tube boilers take less time to increase temperature from a cold start. In addition, water-tube boilers are considered to be more responsive to load variation and more capable of precise load control. However, because a fire-tube boiler has more internal water mass and a larger steam drum than an equivalent capacity water-tube boiler, the fire-tube boiler can handle greater short-term surges in demand. The disadvantage to this is that once pressure has dropped to meet the surge in demand, the fire-tube boiler takes longer to increase the operating pressure back up to the control setpoint. In general, water-tube boilers have higher turn-down ratios. Fire-tube boilers reportedly have simpler operating designs, less critical water quality requirements, and comparably lower maintenance costs than water-tube boilers.
Heat Recovery
Published in David A. Lewandowski, Design of Thermal Oxidation Systems for Volatile Organic Compounds, 2017
Another form of recuperative heat recovery uses waste heat boilers. The boiler and thermal oxidizer are directly connected through a transition section of ductwork. Hot products of combustion flow through the boiler, generating steam from boiler feedwater. Two types of boilers are used in this application: firetube and watertube. Both units are essentially shell and tube heat exchangers. In a firetube boiler, the hot combustion products flow through a tube bank that is surrounded by water. Conversely, in a watertube boiler, water flows through tubes and hot combustion products flow around the tubes. In contrast to combustion/boiler systems whose sole purpose is to produce steam, waste heat boilers in thermal oxidizer applications are not designed with a radiant section. A radiant boiler section is normally used when a high temperature flame or combustion zone is present. In the thermal oxidizer, such a zone may be present, but it is at the beginning of the thermal oxidizer residence chamber near the burner(s). By the time the combustion products enter the boiler, flames have dissipated.
Understanding and Managing Boilers
Published in Barney L. Capehart, William J. Kennedy, Wayne C. Turner, Guide to Energy Management, 2020
Barney L. Capehart, William J. Kennedy, Wayne C. Turner
A boiler is either a fire tube boiler—with tubes containing flame and surrounded by water—or a water tube boiler—with tubes containing water surrounded by flame. The basic operation of a fire tube boiler is shown in Figure 9-1. Fuel and air are combined in a burner, go through tubes and heat up water, and leave through a flue. The water is brought into the boiler, surrounds the tubes containing the fire from the burner, rises to the top under pressure, and leaves the boiler for use in industrial processes or to generate electricity.
Heat Transfer in Multiport Minichannel Condensers and Evaporators: Correlation Development and Meta-Analysis
Published in Heat Transfer Engineering, 2023
Yagnavalkya Mukkamala, Jaco Dirker
Industrial condensers and evaporators such as water-cooled shell and tube condensers or water-tube boilers are frequently used in power plants and other large-scale process industries for condensing or generating steam and other applications. Although the design of such surface phase-change heat exchangers (HXs) is well established, they are bulky, expensive, and not very energy efficient. Compact, lightweight, highly efficient condensers and evaporators have replaced traditional shell and tube designs in the aerospace and electronics industries. They are also widely used as condensing HXs and dehumidifiers onboard spacecraft. These compact systems have high heat absorption rates and superior thermal efficiencies. Multiport minichannels or microchannels consisting of several parallel small diameter channels are frequently deployed as condensers and evaporators and combine a single channel’s high efficiency and heat transfer rates. Kedzierski [1] demonstrated that compact, multiport, brazed condensers and evaporators were highly efficient as compact industrial-grade HXs.