With a conventional absorption water heater/chiller, for example, as shown in Japanese Patent Unexamined Publication No. 8-193767, a liquid chamber serving as a liquid reservoir for storing an absorption solution is formed in upper and lower portions of a combustion chamber, through which a combustion gas generated in a burner of a high temperature regenerator flows, and a plurality of solution tubes for communication between the upper liquid chamber and the lower liquid chamber are provided to extend through the combustion chamber. These solution tubes can be largely classified into two groups.
One of the groups provides a tube group which is positioned near the burner and against which flame strikes, and the other of the groups provides a tube group positioned apart from the burner. A space where the solution tubes do not stand close together is defined between the two groups. Then, flame issuing from the burner is caused to strike against the group of liquid tubes, which are positioned near the burner, to decrease in temperature. Thus, reduction of nitrogen oxide (NOx) generated in the high temperature regenerator is achieved.
Hereupon, with the high temperature regenerator of the absorption water heater/chiller described in Japanese Patent Unexamined Publication No. 8-193767, the solution tubes are circular in cross sectional shape, so that liquid and vapor flow only in one direction from a lower side to an upper side. That is, a one-dimensional flow, in which a boiled rising flow goes throughout the entire tubes, is only generated.
When combustion is effected with the flame of the burner near the group of solution tubes, which stand close together in the combustion chamber, the combustion gas is high in temperature at those regions of the solution tubes, with which flame contacts, to provide a high heat flux. In the case where a circular tube is used for the solution tubes, an increase in heat flux leads to an increase in amount of vapor generated in the tubes to cause an increased flow resistance. As a result, the solution circulating in the solution tubes is reduced amount, and the solution becomes locally high in concentration. An experimental study carried out by the inventors of the present application has revealed that corrosive deterioration is generated in those portions of the solution tubes, in which the solution becomes locally high in concentration. Accordingly, it is not possible to use an inexpensive material, and so use of an extremely expensive high temperature regenerator is unavoidable.
Further, in Japanese Patent Unexamined Publication No. 9-42800 discloses an absorption water heater/chiller, in which forced convection is generated by passing a dilute solution, supplied from a solution pump, through a group of heat transfer tubes having a high heat flux and disposed near the burner. However, when partially loaded, the absorption water heater/chiller is operated with an amount of circulating solution throttled in the high temperature regenerator, thus causing a disadvantageous that partial load operation cannot be effected in the construction described in the above publication, in which forced convection applies for the high temperature regenerator.
Further, Japanese Patent Unexamined Publication No. 8-49802 discloses a high temperature regenerator for an absorption water cooing and heating apparatus, in which Karman's vortices are generated with a relationship P.gtoreq.2D where P indicates a pitch of a group of liquid tubes in a fuel or air flow direction and D indicates a diameter D of the liquid tubes, and mixing of flame is promoted by the Karman's vortices. With the construction described in the above publication, the Karman's vortices are generated to cause mixing of unburned gases which makes the combustion gas uniform in temperature. However, since the combustion gas decreases uniformly in temperature, CO is reduced in a rate of oxidation reaction. Hereupon, to eliminate CO through oxidization, there is caused a need of providing a space which is useful for oxidization of CO but not for heat transfer, in a downstream side of the group of liquid tubes.
The invention has been made in view of the disadvantage of the prior art described above, and an object of the invention is to achieve both of reduction of thermal NOx and restriction of CO generation -in an absorption water heater/chiller. Another object of the invention is to make an absorption water heater/chiller and a high temperature regenerator therefor compact. A further object of the invention is to realize an inexpensive and long-life absorption water heater/chiller and a high temperature regenerator therefor. Still further object of the invention is to realize an absorption water heater/chiller capable of stably operating even under a partly loaded condition, and a high temperature regenerator therefor.