JPS62142961A - Heat exchanger for use in water heater - Google Patents

Abstract

PURPOSE:To increase the cooling effect of the titled heat exchanger to reduce the heat storage quantity of a drum and to prevent after-heating after fire extinguishment of a burner by using gas-permeable ceramics consisting of a honey-comb structure for the drum of the heat exchanger, and aligning the direction of cells of the honey-comb structure in the direction of a combustion gas. CONSTITUTION:A combustion gas supplied to a burner 4 forms a flame 10 on a burner, and made into a combustion gas 9 which is supplied to a fin tube heat exchanger 2 to heat water 8 to be heated. The thus heated water is utilized as hot water. A part of heat generated by the burner is supplied to a combustion drum 3. A material used for the drum 3 is ceramics which form a honey-comb structure 12. Cool air 17 within the cells 16 of the honey-comb structure is heated and obtains bouyancy and rises up. Accordingly, cool air brings away heat supplied to the drum 3. Therefore, the heat storage quantity of the drum 3 is small, and after-heating when the burner and the heating of water are stopped is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat exchanger for water heaters for domestic or commercial use.

Conventional technology A combustion chamber is constructed by placing a heat exchanger and a cylindrical drum around the heat exchanger, and a heat exchange tube is wrapped around the drum.
Copper is often used as the material. The heated water received heat from the heat exchange tubes surrounding the drum and the fin tube heat exchanger, and was used as hot water.

Problems to be Solved by the Invention In such a heat exchanger, a burner is located at the entrance of a combustion chamber, and combustion heat from a flame formed on the burner is utilized. If the hot water is turned off during taping, the temperature of the hot water remaining in the heat exchanger continues to rise. This phenomenon is generally referred to as after-boiling, and it is thought that the combustion heat stored in the heat exchanger caused the water temperature to rise. After boiling, when the user uses the hot water again, the hot water first comes out, which can cause burns and pose many safety problems.

On the other hand, a method of constructing a cylindrical drum out of ceramic has begun to be used. This is aimed at downsizing the heat exchanger and improving its durability. Shigashina≠nuhe? Even after the burner is extinguished, this heat still heats the water in the fin tube, and the above drawbacks cannot be solved.

The present invention reduces heat accumulation in the drum and prevents the after-boiling phenomenon.

Means for solving the problems and technical means of the present invention for solving the above problems are as follows:
Air-permeable ceramics having a honeycomb structure are used for the drum of the heat exchanger, and the cells constituting the honeycomb are positioned in appropriate directions to make the surface of the ceramic dense and eliminate air permeability.

The upstream side of the honeycomb is open to the outside air so that cooling air can flow into it.

Some of the heat generated from the flame burned in the working burner is radiated, and some is supplied to the drum by heat transfer from the combustion gas. Most of the heat is then supplied to the fin-tube heat exchanger.

At this time, the heat supplied to the drum heats the air in the honeycomb portion of the drum. Therefore, the air flows upward due to buoyancy and absorbs heat from the ceramics. At this time, since the surface of the ceramic is dense, the airflow inside the drum is cut off from the airflow outside, and there is little loss of heat to the outside. Furthermore, the buoyancy effect of the air within the drum is large and the temperature rise in the drum is small.

Therefore, the amount of heat stored in the drum is small, and the above-mentioned after-boiling phenomenon can be easily prevented.

EXAMPLE An example of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, 1 is a heat exchanger body, 2 is a fin tube heat exchanger, 3 is a cylindrical drum, and 4 is a burner for heating the heat exchanger body 1. In FIG. The heat exchanger main body 1 includes a fin-tube heat exchanger 2 and a drum 3, and constitutes a combustion chamber 6.

The fin tube heat exchanger 2 is composed of a large number of flat fins 6 and water pipes 7 arranged in a meandering manner perpendicular to the fins 6. Heated water 8 flows through the water pipes 7, and the heat generated on the burner 4 is heated. It is heated by the high-temperature combustion gas 9 and used as hot water.

Figure 2 is an assembly diagram of the heat exchanger main body 1 and burner 4, and A-AI in Figure 1! 'r plane. 10 is a flame. 11 is a part of the exterior.

FIG. 3 is a detailed view of a portion of the drum 3. The drum 3 is made of ceramic and has a honeycomb structure 12. - By way of example, a honeycomb structure is manufactured as follows. A corrugated sheet is formed by bonding a corrugated sheet 13 and a plate-like sheet 14, and a large number of cells 16 are formed by using the walls of each sheet as cell walls 16 to form a honeycomb structure. Cooling air 17 passes through the cell.

The cells 16 of the drum 3 are composed of a corrugated sheet 13 and a plate-like sheet 14.
The cell 16 is located between the inlet 18 and the outlet 19 of the combustion chamber. The inner surface 20 of the drum 3 is open to the combustion chamber 5, and the outer surface 21 is open to the atmosphere. The main component of ceramics is alumina fiber, which is formed into a corrugated form using corrugated sheets and plate-like sheets. A slurry of ceramic powder suspended in water is applied to the surface of the molded product, and the molded product is fired at 1250'C in air. The surface of this molded product is dense and has no air permeability, and the porosity after firing is 40 to 95 inches.

Next, the operation of the structure of this embodiment will be explained. The combustion gas supplied to the burner 4 forms a flame 1o on the burner, becomes high-temperature combustion gas 9, is supplied to the fin tube heat exchanger 2, heats the heated water 8, and is used as hot water. Part of the heat generated by the burner is supplied to the drum 3 as radiation, and the other part is supplied to the drum 3 by heat transfer from the high-temperature combustion gas.

This heat heats the cooling air 17 within the cells 1e of the honeycomb structure. The cooling air gains buoyancy and rises.

Therefore, since the heat supplied to the drum 3 is carried away by the cooling air, the amount of heat stored in the drum is small.

Heat is supplied to the inner surface 20 of the drum from the flame or hot combustion gases. Since the surface is dense, there is no heat transfer due to gas inflow or outflow due to molecular diffusion. Most of the heat transfer is due to radiation. This heat is then transferred to the corrugated sheet 13.

At this time, the cooling air removes heat from the plate-like sheet 14 and the corrugated sheet 13, but the corrugated sheet has a large surface area. Therefore,
The amount of heat carried away by the cooling air 17 passing through the cells 16 is large. Further, since the cell wall around the cell 16 is made of a ceramic heat insulating material, the buoyancy of the cooling air is fully utilized. Since the sheet has a large porosity, cooling air flows inside the ceramic sheet. As a result, the temperature increase on the drum outer surface 21 is small.

Further, the drum 3 is a honeycomb structure 12 and has a dense surface, so it has a high structural strength.

In FIG. 2, the outlet 19 of the drum 3 is located in the fin tube heat exchanger 2, and when the combustion gas passes through, cooling air 17 is blown into the fin tube heat exchanger 2. Heat is absorbed by exchanger 2. Since the cooling air 17 receives buoyancy within the cell 16 and is further sucked by the fin-tube heat exchanger, the flow velocity within the cell increases, heat can be sufficiently removed by the cell, and the temperature of the outer surface is low.

Furthermore, since the outer surface of the drum is low, the distance from the outer device 1 can be shortened, making it easy to make the water heater compact.

Next, other embodiments of the present invention will be described.

FIG. 4 shows another embodiment in which the drum outlet 22 is located outside the fin-tube heat exchanger 23. In such a structure, since the cooling air 26 passing through the cells 25 of the drum 24 is released to the atmosphere from the drum outlet 22, it is possible to further prevent after-boiling when the burner and heated water are stopped.

Effects of the Invention The present invention forms a honeycomb structure in the drum part of a heat exchanger for a water heater using a ceramic material. The direction of the cell is located in the direction of the combustion gas, and the following effects can be obtained.

(1) The amount of heat stored in the drum is small because the heat received from the burner is reduced, and the cooling air passes through the voids of the drum, which is made of a honeycomb structure with a small heat capacity, and takes away the heat from the drum. After-boiling can be prevented.

(2) Since it is a honeycomb structure with high air permeability and a hard surface, it is lightweight and has sufficient mechanical strength.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of an embodiment of the heat exchanger for a water heater of the present invention, FIG. 2 is a vertical sectional view of the same, FIG. 3 is a perspective view of the main parts constituting the wall of the drum, and FIG. 4 FIG. 2 is a longitudinal cross-sectional view of another embodiment. 1... Heat exchanger body, 2... Fin tube heat exchanger, 3... Drum, 4...
・Burna, 16...Cell. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
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Claims (2)

[Claims] (1) In a water heater heat exchanger in which a combustion chamber is configured by a drum and a fin-tube heat exchanger, the drum is made of a honeycomb structure made of porous ceramics having multiple cells, and each cell is a heat exchanger. A heat exchanger for a water heater, which is located in the direction of the flow of combustion gas in the water heater, and is characterized by having a porous ceramic surface that forms a drum and has a dense structure. (2) The heat exchanger for a water heater according to claim 1, wherein the porous ceramic has a porosity of 40% to 95%, and the surface is a thin layer with no air permeability.