Heating – Work chamber having heating means – Combustion products heat work by contact
Patent
1998-06-24
2000-08-29
Walberg, Teresa
Heating
Work chamber having heating means
Combustion products heat work by contact
432179, 432181, F27D 1700
Patent
active
061099147
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a gas recirculating furnace. More particularly, the present invention relates to a gas recirculating furnace for forming a recirculating gas current (referred to as a strong recirculating current in this specification) whose volume is extremely larger than that of a supplied gas current by temporarily taking the recirculating gas current to the outside of a furnace and then increasing the velocity of the gas current to be returned into the furnace.
BACKGROUND OF THE INVENTION
In case of a material or a small heating target which has a very small radiation ratio such as aluminum or ceramics, it is difficult to remove heat from such a heating target even though the radiation heat is given thereto or uniformly give heat thereto, and hence this kind of target is heated based on convection heat transfer. Since the velocity of a gas current controls the heat transfer in the convection heat transfer, there has been proposed a gas recirculating furnace for forcibly recirculating a gas current in the furnace. For example, a gas recirculating furnace such as shown in FIG. 11 is used for heating the heating target. This gas recirculating furnace is of a batch type and comprises an out-of-furnace circulating path 106 which connects a combustion chamber 102 with an exhaust chamber 103 on both side walls of a furnace 101 and has a hot blast circulating fan 104 and a duct 105 between these chambers. This gas recirculating furnace forms a recirculating gas current which partially takes out combustion exhaust gas from the exhaust chamber 103 and returns it into the combustion chamber 102. In case of this gas recirculating furnace, the gas current heated by the flame in the combustion chamber 102 passes through the inside of the furnace 107 in a direction orthogonal to the direction along which the heating target is carried and flows into the exhaust chamber 103 while heating the heating target W. Further, a part of the recirculating gas current led into the exhaust chamber 103 is exhausted, and the remaining part of the same is led into a duct (circulating path) 105 to be forcibly recirculated.
In addition, as shown in FIG. 12, in case of a continuous gas recirculating furnace constituting a plurality of zones 107a, . . . , 107e, a combustion chamber 102 and an exhaust chamber 103 such as shown in FIG. 11 are provided on the both side walls of the furnace body 101 although not illustrated in FIG. 12 so that the recirculating gas current crossing the inside of the furnace be formed in each zone. An exhaust opening 110 is formed to the zone 107a adjacent to an entry opening for the heating target 108 in order to collect combustion gas which is generated in the respective zones 107a, . . . , 107e and used for increasing the heat of the gas current and exhaust the collected gas from one position.
However, since the energy for causing the strong recirculating current depends on a flow quantity of the gas current and a pressure, the obtainable strong recirculating current is limited in the conventional gas recirculating furnace for performing forcible recirculation while maintaining the hot blast. That is, the pressure is proportional to a square of a flow velocity, and hence the pressure must be gained in proportion to a square of a flow velocity when increasing the flow velocity. However, increasing the pressure in proportion to the square also extremely increases the power of the circulating fan 106, and the discharge pressure can not be increased, thereby limiting a quantity of recirculation. In other words, it is hard to form the large strong recirculating current. Moreover, a high-temperature hot blast is a target, a heat-resisting blade or fan shaft must be cooled down and failures may be likely to occur. Therefore, a fan which can resist the high-temperature hot blast did not exist and recirculating the high-temperature hot blast was difficult in the prior art. Thus, in the prior art gas recirculating furnace, the limit of the temperature of gas which can recirc
Lu Jiping
Nippon Furnace Kogyo Kabushiki Kaisha
Walberg Teresa
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