Liquid heaters and vaporizers – Water tube
Reexamination Certificate
2000-08-01
2001-08-07
Wilson, Gregory (Department: 3749)
Liquid heaters and vaporizers
Water tube
C122S00600B, C122S367100, C122S367300
Reexamination Certificate
active
06269782
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to boiler body structure of water-tube boilers such as once-through boilers, natural circulation water-tube boilers and forced circulation water-tube boilers.
As a body structure of water-tube boilers, there has been provided, hitherto, one in which a plurality of water tubes are arranged into an annular shape, thereby forming an inner water tube array, where a combustion chamber is defined by a space inner than the inner water tube array, while a plurality of water tubes are further arranged into an annular shape outside the inner water tube array, thereby forming an outer water tube array, where a gas flow passage is defined between the two water tube arrays. Heat transfer primarily by radiation is performed within the combustion chamber, and heat transfer primarily by convection is performed in the gas flow passage.
In this water-tube boiler, for improvement in boiler efficiency, heat transfer fins are provided on the water tubes as a measure for increasing the heat transfer area. More specifically, fully circumferential fins are provided on a specified number of outer water tubes placed near an opening formed in the outer water tube array so that the boiler efficiency can be improved (e.g., see Japanese Patent Laid-Open Gazette Hei 9-133301 (Patent Abstracts of Japan/Publication Number: 09133301A)). However, out of the heat transfer surfaces confronting the gas flow passage, it is only part of heat transfer surfaces of the outer water tube array that are improved in heat transfer surface structure. That is, the heat transfer surface structure is no more than set in two stages, the vicinities of the opening in the outer water tube array and the upstream side of the opening. Still, whereas the water tubes equipped with fully circumferential fins are provided in a region where the gas temperature is lower than a specified temperature in order to prevent the fully circumferential fins from burning out, this region is a much limited region on the downstream side out of the whole gas flow passage. Therefore, the water-tube boiler is other than designed so as to attain enough increase in heat transfer amount. Moreover, although some extent of increase in heat transfer amount can be attained by the provision of the fully circumferential fins, yet there is a need for further device in order to make effective use of the whole heat transfer surfaces of the water tubes equipped with the fully circumferential fins.
SUMMARY OF THE INVENTION
An object of the present invention is to further improve the boiler efficiency and moreover slim down the whole boiler body, by totally improving the heat transfer surfaces confronting the gas flow passage, i.e., forming the heat transfer surface structure into three stages, and also by making effective use of the whole heat transfer surfaces equipped with the fully circumferential fins.
In order to achieve the above object, the present invention provides a water-tube boiler comprising: an annular first water tube array made up of a plurality of water tubes and having a first opening; an annular second water tube array made up of a plurality of water tubes and having a second opening, the second water tube array being arranged outside the first water tube array; a combustion chamber provided inside the first water tube array; and a gas flow passage leading from the first opening to the second opening and defined between the two water tube arrays, wherein heat transfer surfaces confronting the gas flow passage are structured into a high-temperature heat transfer surface structure, a middle-temperature heat transfer surface structure, and a low-temperature heat transfer surface structure, as viewed from an upstream side along gas flow.
In an embodiment of the invention, the water-tube boiler characterized in that: the high-temperature heat transfer surface structure is a structure that the two water tube arrays are formed into a water wall structure with finless water tubes, the middle-temperature heat transfer surface structure is a structure that at least the second water tube array is formed into a water wall structure with one-side finned water tubes, and the low-temperature heat transfer surface structure is a structure that the first water tube array is formed into a water wall structure with finless water tubes while the second water tube array has fully circumferentially finned water tubes arranged so as to be spaced from one another with specified intervals.
In an embodiment of the invention, the water-tube boiler is characterized in that: the high-temperature heat transfer surface structure is a structure that the two water tube arrays are formed into a water wall structure with finless water tubes, the middle-temperature heat transfer surface structure is a structure that at least the second water tube array is formed into a water wall structure with one-side finned water tubes, and the low-temperature heat transfer surface structure is a structure that the first water tube array is formed into a water wall structure with one-side finned water tubes while the second water tube array has fully circumferentially finned water tubes arranged so as to be spaced from one another with specified intervals.
In an embodiment of the invention, the water-tube boiler is characterized in that part of the second water tube array constituting the low-temperature heat transfer surface structure is so structured that a plurality of fully circumferentially finned water tubes are arranged so as to be spaced from one another with specified intervals, and a guide member is provided outside these fully circumferentially finned water tubes.
In an embodiment of the invention, the water-tube boiler is characterized in that the guide member is formed into a projecting-and-depressing state along the fully circumferentially finned water tubes.
In an embodiment of the invention, the water-tube boiler is characterized in that a multiplicity of protrusions are provided inside the guide member.
In an embodiment of the invention, the water-tube boiler is characterized in that the one-side finned water tubes constituting the low-temperature heat transfer surface structure comprise third heat transfer fins provided so as to extend along an axis of the one-side finned water tubes, the third heat transfer fins being projecting into between the individual fully circumferentially finned water tubes.
Further, in an embodiment of the invention, the water-tube boiler is characterized in that the one-side finned water tubes constituting the low-temperature heat transfer surface structure are equipped with flat-shaped fourth heat transfer fins which are formed in multiple stages along an axis of the one-side finned water tubes and which are provided generally horizontally.
Next, embodiments of the present invention are explained. The present invention is embodied as a water-tube boiler of the multiple-tube type, and applied not only as steam boilers or hot water boilers, but also as heat medium boilers in which a heat medium is heated.
An annular first water tube array is formed of a plurality of water tubes, and a combustion chamber is defined inside this first water tube array. Outside the first water tube array, an annular second water tube array is formed of a plurality of water tubes, and a gas flow passage is defined between the second water tube array and the first water tube array. The first water tube array has a first opening formed therein, and the combustion chamber and the gas flow passage are communicated with each other by this first opening. The second water tube array has a second opening formed therein, and the gas flow passage and a flue are communicated with each other by this second opening.
The gas flow passage is classified into a high-temperature region, a middle-temperature region and a low-temperature region, as viewed from the upstream side along the gas flow, according to the gas temperature. Heat transfer surfaces confronting the gas flow passage are set to a high-temperature heat transfer surface s
Kawakami Akinori
Kayahara Toshihiro
Kondou Kanta
Morimatsu Takashi
Ookubo Tomohiro
Birch & Stewart Kolasch & Birch, LLP
Miura Co., Ltd.
Wilson Gregory
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