Heat exchanger

Abstract: A heat pipe apparatus incorporated in a heat exchanger comprises an evaporative pipe group (16) disposed within a flow (G₁) of a heating fluid, a condenser pipe group (20) located away from the evaporative pipe group (16), a passage (18) for connecting both pipe groups and for circulating there­ through a working medium, another passage (24) branching off from the connecting passage, and at least one another condenser pipe group (26) associated with the another pas­ sage. The condenser pipe group (20) and the another con­ denser pipe group (26) are disposed within two flows (G₂, G₃) of fluid to be heated so as to heat them.

Description: BACKGROUND OF THE INVENTION FIELD OF THE INVENTION: The present invention relates to a heat exchanger incorporating therein a heat pipe apparatus of the kind referred to in the preamble portion of patent claim 1. Such a heat exchanger is known form US-A-4 314 601. DESCRIPTION OF THE PRIOR ART Various types of heat exchangers have been used so as to heat two or more fluids to be heated (lower temperature fluid) by means of one heating fluid (higher temperature fluid). A conventional heat exchanger, for example a heat storage rotary type heat exchanger, a multi-tubular pipe type heat exchanger or plate type heat exchanger among such heat exchangers each necessitates a division of a heating fluid flow into branch flows corresponding to the number of the fluids to be heated, whereby a heat exchange is effected between the branched heating fluid flow and the corresponding fluid to be heated, or necessitates a provision of heat exchangers within the heating fluid each of which heats the corresponding fluid to be heated. Under the above-mentioned circumstances, a heat exchanger has been proposed, which incorporates a heat pipe apparatus including an evaporator pipe section disposed within the flow of a heating fluid, a condenser pipe section is disposed within the flow of a fluid to be heated and located in series and spaced away from the evaporator pipe section, and passage means for connecting both pipe sections to each other. Generally, in this type of heat pipe apparatus which is so called the separate type heat pipe apparatus, it is necessary to provide therein sets of relief valves and non-condensable gas separators. However, as the number of the condenser pipe sections increases, the number of the sets of relief valves and non-condensable gas separators proportionally increases, too. Thus, the number of necessary parts and the cost for the heat exchanger increase. Further, in the above-mentioned construction wherein both pipe sections are arranged in series, a difference between temperatures of the heating fluid and the heated fluid passing from through the condenser pipe section becomes smaller, so that it is required to increase the quantity of heat being exchanged at the upstream side of the fluid. From prior art document US-A-4 314 601 a heat exchanger is known incorporating a heat pipe apparatus, said heat pipe apparatus comprising: evaporative pipe groups disposed within a flow of a heating fluid; first condenser pipe groups disposed within a flow of a fluid to be heated, spaced from said evaporative pipe groups; first passage means for connecting said evaporative pipe groups with said first condenser pipe groups and for circulating therethrough a working medium; and second condenser pipe groups, separated from said first condenser pipe groups: This document disclosed an on-off-valve in a refrigerant outflow conduct which has not the task to remove the non-condensable gas from the system during the operation of the system. If this valve is opened during the operation of the system not only non-condensable gas but also the working medium will be removed outside. SUMMARY OF THE INVENTION An object of the present invention is to provide a heat exchanger incorporating a heat pipe apparatus which has no such disadvantages as mentioned above and which has a structure allowing to remove non-condensable gas effectively from the working medium. This object is accomplished with a heat exchanger as claimed. Dependent claims are directed on features of preferred embodiments of the heat exchanger according to the present invention. Advantages of the present invention will become apparent from the following description of preferred embodiments made in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS: Fig. 1 shows a construction of a conventional separate type heat pipe apparatus; Fig. 2 is a schematic illustration of the apparatus shown in Fig. 1; Fig. 3 is a schematic illustration of the conventional separate type heat pipe apparatus arranged to heat two fluids; Fig. 4 is a diagram showing the variation in temperature between the fluids in the case of the apparatus shown in Fig. 3; Fig. 5 shows a construction of a heat pipe apparatus according to a first embodiment of the present invention; Fig. 6 is a schematic illustration of the apparatus shown in Fig. 5; Fig. 7 is a diagram showing the variation in temperature between the fluids in the case of the apparatus shown in Fig. 6; Fig. 8 shows a construction of the heat pipe apparatus according to a second embodiment of the present invention; Fig. 8A shows a modification of the heat pipe apparatus shown in Fig. 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS: Fig. 1 shows a structure of the conventional separate type heat pipe apparatus. In this Figure, the reference numeral 1 denotes an evaporative pipe group which is disposed within a duct 2 through which a heating fluid (such as, for example, a gas) G1 passes. A medium in the evaporative pipe group 1 is heated by the heating fluid G1 to become a vapor. The medium vapor is carried from an upper header 3 of the evaporative pipe group 1 through a passage section 4A of a passage 4 to an upper header 7 of a condenser pipe group 6 located within a duct 5 permitting therethrough the flow of a fluid (such as, for example, a gas) G2 to be heated. The medium vapor from the evaporative pipe group 1 is condensed within the condenser pipe group 6 and is allowed to flow from a lower header 8 thereof into a lower header 9 of the evaporative pipe group 1 through a passage section 4B of the passage 4. Since the lower header 8 of the condenser pipe group 6 is located at a higher level than the lower header 9 of the evaporative pipe group 1 is, the medium is conducted to a natural circulation. A relief valve 10 and a non-condensable gas separator 11 are provided in the passage section 4A of the passage 4. Fig. 2 illustrates this structure. Fig. 3 illustrates a heat pipe apparatus arranged to transmit the heat of a high temperature gas G1 (such as, for example, a combustion gas of a furnace) passing through the duct 2 to two fluids G2 (for example, an air for a combustion) and G3 (for example, a fuel gas). Within the duct 2, two different evaporative pipe groups 1 and 12 are respectively disposed. Within the ducts 5 and 13 through which the fluids G2 and G3 pass respectively, the condenser pipe groups 6 and 14 associated with the evaporative pipe groups 1 and 12 are respectively disposed. In this case, six relief valves, the number of which is the same as that of the condenser pipe groups, are necessary, and six non-condensable gas separators are also required. In consequence, the number of necessary parts increases, whereby the cost also increases correspondingly. Furthermore, in the above mentioned series arrangement of the pipe groups, the difference in temperature between the higher temperature fluid and each lower temperature fluid at the outlet disadvantageously becomes small as shown in Fig. 4. As a result, it is necessary to make the quantity of heat to be exchanged at the upstream side large. Fig. 5 shows the construction of a heat pipe apparatus according to a first embodiment of the present invention. In the first embodiment, a sub passage 29 is branched off from the passage section 18B through which the liquefied working medium flows back into the lower header 23 of the evaporative pipe group 16, and is connected to the lower header 30 of the condenser pipe group 26 located within the duct 25 through which the third fluid G3 flows. The vapor and the non-condensable gas within the passage section 18B are removed therefrom and flowed into another condenser pipe groups 26, whereby only medium vapor is condensed and the non-condensable gas can be, if necessary, discharged out through the separator 28, so that it is possible to prevent the heat transmission effect from being decreased. Where the heat pipe apparatus is formed in the above-mentioned structure, i.e., a composite type structure, the variation in temperature is as shown in Fig. 7 and the difference between the temperatures of the heating fluid and each of fluids to be heated at the outlet can be made greater. In this embodiment, therefore, it becomes possible to decrease a heat transmission surface. Fig. 6 is a schematic illustration of the structure of the apparatus shown in Fig. 5. Fig. 8 shows the heat pipe apparatus according to a second embodiment of the present invention. This second embodiment is substantially same to the embodiment shown in Fig. 5 in respect of the sub passage 29 which is branched off from the passage section 18B through which the liquefied working medium flows back into the lower header 23 of the evaporative pipe group 16, but is different from the apparatus shown in Fig. 5 in respect of that another condenser pipe group 26 provided with a separator 28 for removing the non-condensable gas is disposed within the same duct 19 or 25 together with the condenser pipe group 20. The foregoing descriptions, have referred to the embodiment of the separate type heat pipe apparatus in which two fluid, i.e., a second and a third fluid are heated.

Claims: A heat exchanger incorporating a heat pipe apparatus, said heat pipe apparatus comprising: evaporative pipe groups (16) disposed within a duct (15) through which a heating fluid (G1) flows, first condenser pipe groups (20) disposed within a duct (19) through which a fluid (G2) to be heated flows, spaced from said evaporative pipe groups, first passage means (18) for connecting said evaporative pipe groups (16) with said first condenser pipe groups (20) and for circulating therethrough a working medium; and second condenser pipe groups (26) disposed within a duct through which another fluid (G3) to be heated flows, separated from said first condenser pipe groups (20), a sub-passage (29) for connecting a lower header (30) of another condenser pipe group (26) with said first or second condenser pipe groups (20); and gas separator means (28) provided at an upper part of said first or second condenser pipe groups (20) for discharging non-condensable gas outside (Fig. 8). A heat exchanger according to claim 1, wherein said second passage means (29) includes three passage sections (Fig. 5). A heat exchanger according to claim 2, wherein said passage sections of said second passage means (29) branch off from a passage section of said first passage means (18) connecting a header (23) of said evaporative pipe groups (16) disposed upstream of flow of said working medium with a header (22) of said first condenser pipe groups (20) disposed downstream of flow of said working medium, and are connected to the lower header (30) of said second condenser pipe groups (26) (Fig. 5).

Inventors: KOUTAKA IKUO, KOUTAKA, IKUO
Applicants: BABCOCK HITACHI KK, BABCOCK-HITACHI KABUSHIKI KAISHA
Application year: 1984
Main classification: F28D15
IPC codes: F23L15, F23J15, F28D15, F23D14